Anatomy PDF

Anatomy is the study of the structure of the body and the relationship of its constituent parts to each other. The cell is the basic unit of the human body. Most types of cells tend to occur in groups similar both in appearance and in function. Such organized groups of cells are known as tissues. Va...

Anatomy is the study of the structure of the body and the relationship of its constituent parts to each other. The cell is the basic unit of the human body. Most types of cells tend to occur in groups similar both in appearance and in function. Such organized groups of cells are known as tissues. Various types of tissues form more complex anatomical functional units known as organs which in turns form system. The three main approaches to studying anatomy are regional, systemic, and clinical (applied), ☺Regional anatomy is the method of studying the body's structure by focusing attention on a specific part (e.g., the head), region (the face), or subregion (the orbit); examining the arrangement and relationships of the various systemic structures (muscles, nerves, arteries, etc.) within it. ☺Systemic anatomy recognizes the organization of the body's organs into systems that work together to carry out complex functions. The basic systems are: The integumentary system consists of the skin and its appendages. The skeletal system (osteology) consists of bones and cartilage. The articular system (arthrology) consists of joints and their associated ligaments. The muscular system (myology) consists of muscles that act (contract) to move parts of the body. The nervous system (neurology) consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves and ganglia). The circulatory system (angiology) consists of the cardiovascular (the heart and blood vessels) and lymphatic systems, which function in parallel to transport the body's fluids. The digestive or alimentary system (gastroenterology) consists of the organs and glands associated with ingestion, mastication (chewing), deglutition (swallowing), digestion, and absorption of food and the elimination of feces (solid waste) remaining after the nutrients have been absorbed. The respiratory system consists of the air passages and lungs that supply oxygen to the blood for cellular respiration and eliminate carbon dioxide from it. 1 The urinary system (urology) consists of the kidneys, ureters, urinary bladder, and urethra, which filter blood and subsequently produce, transport, store, and intermittently excrete urine. The reproductive or genital system consists of the gonads (ovaries and testes) that produce eggs (oocytes and sperms), the ducts that transport them. The endocrine system (endocrinology) consists of discrete ductless glands (such as the thyroid gland). ☺Clinical (applied) anatomy emphasizes application of anatomical knowledge to the practice of medicine. The anatomical position: The person is oriented in an erect standing position, with eyes and head looking forwards, the arms close to the sides, palms of the hands facing forward with fingers extended, and feet forward and perpendicular to the body with the heels are together. The anatomical planes The median sagittal plane is an imaginary vertical plane passing through the center of the body, dividing it into equal right and left halves (Fig. 1). Paramedian sagittal plane is any plane parallel to the median plane. Coronal plane is any vertical plane at right angle to the median plane or sagittal plane. It divides the body into anterior and posterior parts. Horizontal or transverse plane is any plane at right angle to both the median and coronal planes. It divides the body into upper and lower parts. Terms of position ☺Median: any structure lying in the median plane. ☺Anterior (ventral): any structure nearer to the front of the body. ☺Posterior (dorsal): any structure nearer to the back of the body. ☺Proximal: any structure nearer to the roots of the limbs (trunk). ☺Distal: any structure far away from the roots of the limbs (trunk). ☺Superficial: means nearer to the surface (skin) of the body. ☺Deep: means away from the surface (skin) of the body. ☺Superior means closer to the head. ☺Inferior means closer to the feet. 2 ☺Medial: A structure situated nearer to the median plane of the body than another is said to be medial to the other. ☺Lateral: A structure that lies farther away from the median plane than another is said to be lateral to the other. Fig. 1: The anatomical position Terms related to movement (Fig.2): ☺Flexion is a movement that takes place in a sagittal plane. For example, flexion of the elbow joint approximates the anterior surface of the forearm to the anterior surface of the arm. It is usually an anterior movement, but it is occasionally posterior, as in the case of the knee joint. ☺Extension means straightening the joint and usually takes place in a posterior direction. ♦Lateral flexion is a movement of the trunk in the coronal plane. 3 ☺Abduction of a limb is the movement away from the midline of the body in the coronal plane. Fig.2: Some anatomical terms used in relation to movements. 4 ☺Adduction of a limb is the movement toward the body in the coronal plane. ☺Rotation is the term applied to the movement of a part of the body around its long axis. ☺Circumduction is the combination in sequence of the movements of flexion, extension, abduction, and adduction. SOME BASIC ANATOMICAL STRUCTURES SKIN The skin covers the body surface. It protects the deeper structures, and plays an important role in regulation of body temperature. It is formed of two layers, the superficial layer, the epidermis, and the deep layer, the dermis (Fig.3). The epidermis is a keratinized stratified epithelium (several layers). It has a tough, horny superficial layer that provides a protective outer surface overlying its basal layer. The epidermis has no blood vessels. The avascular epidermis is nourished by the underlying vascularized dermis. The dermis is composed of dense connective tissue containing many blood vessels, lymphatic vessels, and nerves. These fibers provide skin tone and account for the strength and toughness of skin. The skin appendages are hair follicles, sebaceous glands, sweat glands (fig.3) and the nails (fig.4). ►The nails are keratinized plates on the dorsal surfaces of the tips of the fingers and toes. The proximal edge of the plate is the root of the nail. Fig.3: Structure of the skin. 5 With the exception of the distal edge of the plate, the nail is surrounded Fig.4: and overlapped by folds of skin The nail. known as the nail folds. The surface of skin covered by the nail is the nail bed. ►Hairs are distributed over the whole surface of the body except the lips, the palms of the hands, the sides of the fingers, the glans penis and clitoris, the labia minora and the internal surface of the labia majora, and the soles and sides of the feet and the sides of the toes. Hair follicles are invaginations of the epidermis into the dermis. The follicles lie obliquely to the skin surface. Sebaceous glands lie within the dermis on the sloping undersurface of the follicles. They pour their secretion, the sebum, onto the shafts of the hairs as they pass up through the necks of the follicles. Sweat glands are long, spiral, tubular glands distributed over the surface of the body except the red margins of the lips, the nail beds, and the glans penis and clitoris. FASCIAE The fasciae of the body may be divided into two types, the superficial and the deep. They lie between the skin and the underlying muscles and bones. 1-The superficial fascia, or subcutaneous tissue, is a mixture of loose areolar and adipose tissue that unites the dermis of the skin to the underlying deep fascia. It allows the skin to move more or less freely over the underlying structures. It conducts the blood vessels and nerves which supply the skin, is an important factor in preventing the loss of body heat and gives the body its contour. It is dense in the scalp, back of the neck, palms of the hands and soles of the feet. It is very thin over the dorsal aspects of the hands, feet, sides of neck and face. It is most distinct at the lower part of the anterior abdominal wall, limbs and perineum. 6 Contents: 1-Fat: It contains a variable quantity of fat except in the eyelids, the nose, external ear, the penis, and the scrotum. 2-Muscles: In the face and neck it contains numerous somatic muscles ex. platysma. In the scrotum, it contains the visceral dartos muscle, which corrugates the scrotal skin and helps to support the testes, as well as altering the surface area of the scrotum to control heat loss from it. 3- Mammary gland: in the pectoral region 4- Blood vessels, nerves and lymphatic vessels. 2-The deep fascia: It is a thin dense membrane located deep to the superficial fascia. It is loosely attached to the superficial fascia (Fig.5). It is inelastic, forming sheath for the muscles and preserving the contour of the limb. The deep fascia sends various intramuscular septa from its deep surface to connect it to the bone. These septa divide the limb into different groups of muscles. It is thickened in the palm of the hand and sole of the foot. It is absent in the abdomen allowing it to change its volume during respiration. Fig.5: Section through the arm, to show arrangement of superficial and deep fascia. 7  MUSCLES Definition: Muscles are the red flesh of the body. They are tissues specialized to produce motion by contraction. Types: There are three types of muscular tissue: 1- Skeletal or voluntary: They are stripped (striated) and under the control of will. Examples of skeletal muscles are muscles of limbs. 2- Smooth or involuntary: They are not under the control of will. They are non stripped muscle. Examples of this type are muscles of intestine, uterus and urinary bladder. 3- Cardiac: Involuntary, partially stripped. The function of all three types of muscles is contraction and relaxation. The skeletal muscles mostly pass from one bone to another across a joint. By contraction they approximate the sites of attachment. The cardiac muscle and smooth muscles form the walls of the cavities and tubes; so by their contraction they expel their contents. Gross anatomy of the skeletal (striated muscle) ☺The skeletal muscle is formed of 1-Fleshy part of the belly (Fig. 6). 2-Non-fleshy part by which the muscle is attached into a bone. It may be cord like (tendon), or sheet like (aponeurosis). Muscle attachments: Skeletal muscle is attached by origin and insertion. a) Origin: It is fixed, less mobile attachment. It is the proximal attachment of limb muscle. b) Insertion: It is less fixed, more mobile. It is the distal attachment of the limb Fig. 6: Origin, insertion, and belly of gastrocnemius muscle. muscle. 8 Muscle forms (Fig. 7): Different forms of muscles are present and described according to the direction of their muscle fibers. 1- Strap or parallel muscle fibers e.g. sartorius. 2- Fusiform: Spindle shaped fleshy belly and terminal tendon e.g. biceps brachii. 3- Pennate: a) Unipennate: When its tendon appears on one side of the fleshy fibers, an example is palmar interossei muscles. b)Bipennate: When the fleshy fibers are attached to the tendons at angles on both sides e.g. The rectus femoris. c) Multipennate: When muscle has several tendinous elements to which the fleshy fibers reach from several directions e.g. deltoid. d) Circumpennate: the fibers are arranged in a circurmradial manner around the central tendon e.g. the tibialis anterior muscle. Joints Fig. 7: The different forms of internal structure of skeletal muscle. 9  JOINTS A joint is the articulation between two or more bones. Classification (Figs.8&9): 1- Fibrous joints are of three types: 1) The sutures of the vault of the skull where the fibrous tissue is very thin (sutural ligaments).No movement is allowed. 2) Gomphosis as fixation of the teeth in the alveolar sockets 3) Syndesmoses where the two bones are connected by collagenous interosseous ligament, membrane or cord. Slight movement is allowed. Examples as the inferior tibiofibular joints and interosseous membranes in the forearm and leg. 2- Cartilaginous joints may be divided into two types, primary and secondary. A) Primary cartilaginous joint is one in which the bones are united by a plate of hyaline cartilage that ossifies later on. Thus, the union between the epiphysis and the diaphysis of a growing bone and that between the first rib and the manubrium sterni are examples of such a joint. No movement is possible. B) Secondary cartilaginous joint (symphysis) is one in which the bones are united by a plate of fibrocartilage, and the articular surfaces of the bones are covered by a thin layer of hyaline cartilage. Examples are the manibrusternal junction, the intervertebral disc and the symphysis pubis. The amount of movement possible is dependent on the physical qualities of the fibrocartilage. 3- Synovial joint: It is composed of: a) Bony articular ends, which are usually large and smooth. b) Articular cartilage covers the articular surface of the ends of bones. Its elasticity is useful for the load distribution. 10 Fig. 8: Examples of three types of joints: (A) fibrous joint (coronal suture of skull), (B) cartilaginous joint (joint between two lumbar vertebral bodies), and (C) synovial joint (hip joint). 11  Sutures Gomphosis Syndesmoses Primary cartilaginous joint Synovial joint Secondary cartilaginous joint Fig.9: Types of joints 12 c) Fibrous articular capsule connects the two bony ends together. It may be thickened in parts to form ligaments. d) Synovial membrane and synovial fluid. The inner surface of the articular fibrous capsule is lined by a synovial membrane. It is a highly vascular membrane which covers all the intracapsular structures except the articular surface.It secretes a small amount of synovial fluid to lubricate the movements and to nourish the articular cartilage. e) The blood and nerve supply of the synovial joint is conveyed through arteries and nerves that pierce the fibrous capsule. ►►►TYPES OF SYNOVIAL JOINTS (Fig. 10): Synovial joints may be classified according to the arrangement of the articular surfaces and the types of movement that are possible. 1-Plane joints: The apposed articular surfaces are flat or almost flat, and this permits the bones to slide upon one another. Examples of plane joints are carpal and tarsal joints. 2-Hinge joints: These joints resemble the hinge on a door, (uniaxial joint). Examples of hinge joints are elbow and ankle joints. 3-Pivot joints: In these joints, there is a central bony pivot surrounded by a bony-ligamentous ring. In this type of joint, rotation is the only movement possible (uniaxial joint). The atlanto-axial and superior radioulnar joints are good examples. 4-Condyloid joints: These joints have two distinct convex surfaces that articulate with two concave surfaces. The metacarpophalangeal joints (knuckle joints) are examples. 5-Ellipsoid joints: In these joints, there is an elliptical convex articular surface that fits into an elliptical concave articular surface. The wrist joint (radio-carpal) is a good example (biaxial). 6-Saddle joints: In these joints, the articular surfaces are reciprocally concavoconvex and resemble a saddle on a horse's back. The best example of this type of joint is the carpometacarpal joint of the thumb (multi-axial joint). 7-Ball-and-socket joints: This arrangement permits very free movements (multi-axial joint). The shoulder and hip joints are good examples. JOINTS STABILITY: The stability of a joint depends on three main factors: (1) the shape, size, and arrangement of the articular surfaces, (2) the ligaments, and (3) the tone of the muscles around the joint. 13 Fig. (10): Examples of the different types of synovial joints: (A) plane joints (sternoclavicular and acromioclavicular joints), (B) hinge joint (elbow joint), (C) pivot joint (atlanto-axial joint), (D) condyloid joint (metacarpophalangeal joint), (E) ellipsoid joint (wrist joint), (F) saddle joint (carpometacarpal joint of the thumb), and (G) ball-and-socket joint (hip joint). 14  BONES Bone is a living tissue capable of changing its structure as the result of the stresses to which it is subjected. ►►Functions of bones: 1- Bodily Support: It forms the supporting framework of the body. 2-Motion: Bones give attachment to the muscles and are essential for locomotion. 3-Leverage: Bones serve as a lever for the muscles, as seen in the long bones of the limbs. 4- Protection. The skeleton protects certain soft structures within the human body. An example is the skull, which surrounds the brain and the thoracic cage which protect the heart and lungs. 5- Formation of blood cells. Blood cells are manufactured in the red bone marrow, mainly found in flat bones. 6- Storage for salts as calcium and phosphorus. A) Types of bones according to general shape (figs11,12B): 1- Long: It is made up of an elongated tubular shaft and two enlarged ends. It form levers e.g. bones of the limbs as humerus and femur. 2- Short small: Strengthen an area of skeleton with limited movement e.g. carpal and tarsal bones. 3- Flat: It protects certain structure e.g. bones of skull or provides a wide surface for muscular attachment e.g. scapula. 4- Irregular: Have a variable shape e.g. hip bone. 5- Pneumatic: The central part of the bone is absorbed. It is replaced by air-filled spaces e.g. air sinuses. 6-Sesamoid bones are small nodules of bone that are found in certain tendons where they rub over bony surfaces. The function of a sesamoid bone is to reduce friction. The largest sesamoid bone is the patella, which is situated in the tendon of the quadriceps femoris (fig.11). B) Types of bones according to structure : Bone exists in two forms: a) Compact bone: Outer layer. It is hard substance (Fig.13). b) Cancellous (Spongy) bone: consists of a branching network of trabeculae with intervening spaces that contains red marrow..The trabeculae are arranged in such a manner as to resist the stresses and strains to which the bone is exposed. 15. Fig.12A: The vertebral column. Fig.11:Sections of different types of bones. A Long bone (humerus). B Irregular bone (calcaneum). C Flat bone (two parietal bones separated by the sagittal suture).D Sesamoid bone (patella).E Note arrangement of trabeculae to act as struts to resist both compression and tension forces in upper end of femur. Scapula Fig. 12B: Examples for types of bones Humerus Vertebra Humerus 16  Some details on long bones: ☺Each long bone is formed of two ends (epiphyses) and a shaft (diaphysis). ☺The shaft is composed of compact bone (cortex) encloses a cavity called medullary cavity filled with bone marrow (fig.13). ☺The shaft is covered by a thick layer of fibrous tissue called the periosteum(fig. 13). Fig.13: Parts and structure of long bone. ♦♦♦Flat bones of skull are composed of outer and inner tables of compact bone enclosing a layer of spongy bone called dipole. C) Types of bones according to region: a) Axial skeleton includes the skull, hyoid bone, the vertebral column, the sternum and the ribs (fig.14). b) Appendicular skeleton includes the bones of the appendages i.e. upper limb with shoulder (pectoral) girdle and lower limb with pelvic girdle. The skull together with the mandible forms the skeleton of the head The vertebral column is formed of series of bones called vertebrae. It is formed of five regions (Fig.12A) which are: the cervical region (7 vertebrae), the thoracic region (12 vertebrae), the lumbar region (5 vertebrae), the sacral region (5 vertebrae), and the coccygeal region (3- 5 vertebrae). 17 The thoracic vertebrae with sternum ribs and costal cartilages form the skeleton of the thoracic cage. The sacral vertebrae are united into a single triangular bone called sacrum. Together with two hip bones, the sacrum forms the pelvis. N.B.: The vertebrae articulate with one another by means of intervertebral discs and synovial joints. The skeleton of the limbs (upper or lower), each limb consists of three segments; proximal, intermediate and distal. The proximal segment consists of one bone: the humerus in the arm and the femur in the thigh. The intermediate segment consists of two bones: the radius and ulna in the forearm - the tibia and fibula in the leg. The distal segment consists of three sets of bones: 1. Some small bones: carpal bones in the hand - tarsal bones in the foot. 2. Five elongated bones: metacarpals in the hand – metatarsals in the foot. 3. The digits: three in each finger or toe except the thumb and the big toe where they are two. The shoulder (or pectoral) girdle consists of the clavicle and the scapula while the pelvic girdle consists of the hip bone. 18 Fig.14: The skeleton. A. Anterior view. B. Lateral view. 19  Digestive System The digestive system includes: The alimentary (gastro-intestinal) tract. Certain accessory (digestive organs) glands. The alimentary (gastro-intestinal) tract is the tube in which the food travels during digestion. It starts in the mouth to end at the anus. It is formed of the following structures: the mouth, the pharynx, oesophagus, stomach, small intestine (duodenum, jejunum, and ileum) and large intestine (appendix, caecum, colon, rectum, and anal canal) (Fig. 15). The accessory glands includes salivary glands (parotid, submandibular and sublingual), liver, pancreas and spleen. ♣♣ Mouth: The mouth is divided ►The vestibule of the mouth is a cleft like space separating the lips and cheeks from the teeth and gums. ►Mouth proper is the rest of the mouth cavity, which is enclosed by the teeth. Its floor is formed by the tongue and its roof is formed by the hard and soft palate, which is covered by a mucous membrane. ♣♣ Lips and cheeks: The lips and cheeks are composed chiefly of muscles and fat covered with skin and lined with mucous membrane. ♣♣ Gums: Gums are dense fibrous tissues covered with mucous membrane, attached to the alveolar border of the jaws. It is adherent around the neck of the teeth. ♣♣ Teeth: Permanent teeth:A full set of adult teeth consists of 32 (16 per jaw). Eight (8) in each half jaw counting from before backwards are: 2 incisors, 1 canine, 2 premolars, and 3 molars. Eruption of permanent teeth begins at 6 years of 20 age and ends at 12 years. The third permanent molar erupts around 18 years (Wisdom tooth). Primary or milk teeth: They are 20 in number. 5 in each half jaw, counting from before backwards are two incisors, one canine and two molars. Eruption of deciduous teeth starts at 6 months of age and is completed at two years. ♣♣ Tongue: A fleshy mobile organ, present at the floor of the mouth and mostly formed by muscles covered by a mucosa. The tongue maneuvers the food for chewing and swallowing. It is also concerned with speech and taste. It is attached at the base of the mouth by the lingual frenulum. The dorsum of the tongue is divided into palatine part which occupies the anterior ⅔ and pharyngeal part that occupies the posterior⅓. The two parts are separated by a v- shaped sulcus terminalis. Fig. 15: The digestive system. The mucous membrane of the anterior ⅔ is roughened by the presence of papillae that is responsible for taste sensation. ♣♣ Pharynx: It is a wide 12 cm muscular tube that extends from the base of the skull to the level of the 6th cervical vertebra where it is continuous with the oesophagus. It is divided by the soft palate and epiglottis into three parts; nasopharynx, oropharynx and laryngopharynx. 21 1-Nasopharynx: It lies behind the nasal cavities. It is the widest part of the pharynx. It is always patent. The pharyngeal end of the auditory tube opens in its lateral well. At the junction of the roof and its posterior wall, there is a collection of lymphoid follicles forming the pharyngeal tonsils. In children it may be enlarged to form adenoids. 2-Oropharynx: It lies behind the mouth and tongue. Its side wall presents the palatine tonsil on each side. 3-Laryngo-pharynx: It lies behind the larynx. It is continuous with oesophagus opposite the lower border of the cricoid cartilage (level of the sixth cervical vertebra). Fig.16:The pharynx, midline sagittal view. ♣♣ Oesophagus: It is a 25 cm muscular and collapsible tube that extends from the pharynx above to the stomach below. It passes through the neck, thorax and pierces the diaphragm to open into the cardiac orifice of the stomach. Its wall is formed of a muscular coat and mucous membrane. ♣♣ Stomach: It is concerned with digestion of food. It is the most dilated part of the gut. It is located under the diaphragm (left cupola), in the epigastric area of the abdomen. Its shape and position vary according to its condition and the condition of the surrounding viscera. It has 2 orifices, 2 borders and 2 surfaces. ►Orifices (ends) (Fig. 17): The stomach has 2 ends the cardiac and the pyloric ends. The cardiac end lies between the oesophagus and the stomach. The pyloric end lies between the 22 stomach and the small intestine. The pyloric end is guarded by a strong sphincter of circular muscle fibers called the pyloric sphincter. ►Borders: The stomach has 2 borders, right and left. The right border is short and forms the lesser curvature. The left border is longer and forms the greater curvature. ►Parts: The stomach is formed of fundus, body and pylorus. The fundus is the upper bulging part of the stomach. The body extends from the fundus to the pylorus. The pyloric antrum leads to the pylorus. The pylorus has a canal called pyloric canal which ends by a sphincter called pyloric sphincter. ►Surfaces: The stomach has two surfaces anterosuperior surface and posteroinferior surface. The anterior surface is related to the liver, diaphragm and anterior wall of the abdomen. Fig. 17: The stomach. 23 The posteroinferior surface is related to structures known as stomach bed. These structures are the transverse colon, the pancreas, the spleen, the left kidney, the left suprarenal gland and the diaphragm. Structures of the stomach bed are separated from the stomach by a peritoneal sac called lesser sac cavity. This sac allows distension of the stomach. The stomach is almost completely surrounded by peritoneum. ♣♣ Small intestine: The small intestine is concerned with completion of digestion and absorption of the digested food. It is formed of duodenum, jejnum and ileum. It is about 7 meters long. Fig. 18 ►The duodenum: It is the shortest and widest part of small intestine. If forms a c-shaped curve around the head of pancreas. It is about 25 cm (10 inches) long. The duodenum is usually described to have upper (first), descending (second), horizontal (third) and ascending fourth 24 parts. The fourth part is continuous with the jejunum. The second part of the duodenum receives the bile duct and the pancreatic duct (Fig. 19). ►Jejunum and ileum: It is about 5 to 6 meter in length. It extends from the duodeno-jejunal junction to the ileo-cecal junction. It forms a number of loops. The proximal two-fifths form the jejunum, while the distal three fifths form the ileum. No sharp lines between the two parts. The intestinal mucosa is bent into circular folds and many finger-like projections form villi. Groups of lymphatic nodules, the Peyer's patches are present in the lining of the ileum and prevent bacterial invasion. ♣♣ Large intestine is about 1.5 meters (Fig.20). It begins at the end of ileum and terminates at the anal orifice. It is divided into: caecum, vermiform appendix, ascending colon, right colic flexure, transverse colon, left colic flexure, descending colon, sigmoid colon, rectum and anal canal. Ascending colon 2nd 1st caecum 3rd 4th Fig. 19: The duodenum. Fig. 20: Large intestine. ►Caecum lies in the right iliac fossa. It is a large sac which has a blind lower end and is continuous with the ascending colon.The ileum opens into the large intestine at the junction between the caecum and 25 ascending colon. This opening is called ileocecal junction and is provided by the ileocecal valve. ►Vermiform appendix lies in the right iliac region. It is a very narrow tube of 12 cm long that opens into the posteromedial aspect of the caecum, 2 cm below the ileocecal valve. It contains a large amount of lymphoid tissue. ►Ascending colon begins at the caecum and ascends to the undersurface of the liver where it bends to the left forming the right colic (hepatic) flexure. ►Transverse colon begins from the right colic flexure, crossing the abdomen into the left, where it curves downwards forming the left colic (splenic) flexure. ►Descending colon begins from the left colic flexure and ends at the inlet of the pelvis where it joins the pelvic colon (sigmoid colon) in the left iliac fossa. ►Sigmoid colon forms a loop which lies in the pelvis. It begins at the descending colon and ends at the rectum in front of third sacral vertebra. ►Rectum is about 5 inches (13 cm) long and begins in front of the third sacral vertebra as a continuation of the sigmoid colon and it descends following the concavity of sacrum and coccyx and ends at the anal canal and anus. ►The anal canal is the terminal part of the large intestine. It is situated between the rectum and anus. It is approximately 4 cm long. It is surrounded by inner involuntary and outer voluntary sphincters which keep the lumen closed. 26 Differences between the small and large intestine Small intestine Large intestine Length It is about 7 meters It is about 1.5 meters long long Caliber Smaller Larger Mobility Freely mobile Less freely mobile Teniae coli (3 bands of Absent Present longitudinal muscles) Sacculations Absent Present Appendices epiploicae Absent Present over the free (fat ) surface of the colon except the caecum, the appendix and the rectum The mucous Has permanent No plicae circulares membrane folds, called plicae circulares Villi in mucosa Present Absent Peyer's patches Present absent (lymphatic aggregations) ♣♣ Salivary glands: are 3 pairs The parotid glands are the largest and located in front of the ear. They open in the vestibule of the mouth at Stensen's duct. The submandibular glands are located at the base of the mouth where they open through the Wharton's ducts. Fig. 21: Salivary glands. 1: Parotid gland; The sublingual glands are also located at 2:Submandibular gland; the base of the mouth (under the tongue). 3: Sublingual gland. 27 ♣♣ Liver is the largest gland in the body concerned with metabolism of absorbed food, detoxification of chemicals and secretion of the bile salts which emerge from the liver through the right and left hepatic ducts. It lies under the right copula of the diaphragm. It is formed of 2 large lobes (right and left lobes), (Fig. 22) and 2 small lobes (caudate and quadrate lobes) which are present on the under surface of the liver. They are separated by (porta hepatis) the hilum of the liver, through which vessels and ducts pass. Its upper surface is in contact with the diaphragm and with the anterior abdominal wall. Its visceral surface is related to many structures. The stomach and the lower part of oesophagus are in contact with the left lobe. The right lobe is in contact with the hepatic colic flexure, the duodenum, the right kidney and the right suprarenal gland. The liver secretes the bile-salts which emerge from the liver through the right and left hepatic ducts. Extra hepatic biliary passages ♦Hepatic ducts are two, right and left, one from each lobe. They unite in the porta hepatis to form the common hepatic duct (Fig. 23). ♦Common hepatic duct is about 1.5 inches (4 cm) long and is formed by the union of the right and left hepatic ducts. It is joined on the right side by the cystic duct from the gall bladder to form the bile duct. Fig. 22: The Liver. 28 ♦Gall bladder is an elongated pear-shaped sac that lies on the inferior surface of the right lobe of the liver. It serves as a reservoir for bile, with a capacity of about 50 ml and it has the ability to concentrate the bile. Bile is delivered to the duodenum as the result of contraction and partial emptying of the gall bladder and this mechanism is initiated by the entrance of fatty foods into the duodenum. ♦Cystic duct is about one and half inches long. It joins the common hepatic duct to form the bile duct. ♦Common bile duct is formed by the union of the cystic duct and the common hepatic duct. It is about three inches long. It opens into the wall of the second part of the duodenum where it unites with the pancreatic duct to form the hepatopancreatic ampulla. The hepatopancreatic ampulla (of Fig. 23: Extrahepatic biliary passage. Vater) is guarded by a sphincter (of Oddi) to control the flow of bile.♣♣ Pancreas is a soft lobulated gland. It lies transversely across the posterior abdominal wall behind the stomach. It extends from the duodenum to the spleen. It secretes pancreatic juice into the duodenum. It also has an endocrine Fig. 24: Parts of pancreas. function, and secretes insulin directly in the blood stream. 29 The parts of the pancreas are the head (within the duodenal loop), the neck, the body (extends upwards and to the left) and the tail which reaches the spleen. ♣♣ Spleen is a soft organ and it is the largest single mass of lymphoid tissue in the body. It lies in the left hypochondrium. Its long axis is parallel with the lower 9, 10, 11 ribs. It has 2 surfaces, 2 borders and 2 ends. The two surfaces are: ♦The diaphragmatic surface: is smooth and convex. It is related to the diaphragm. ♦The visceral surface is directed towards the abdominal cavity and related to the stomach, left kidney, tail of pancreas and left colic flexure. The two borders are: ♦Superior border is characterized by the presence of notches. ♦Inferior border is smooth and rounded. The two ends: ♦Posterior end which is directed upwards, backwards and medially. ♦Anterior end which is directed downwards, forwards and laterally. THE PORTAL CIRCULATION The portal circulation is formed by the veins that carry blood from the stomach, small intestine, large intestine, spleen, pancreas and gall bladder. The blood is conveyed to the portal vein. It ascends to the porta hepatis where it divides into right and left branches. Each passes to the corresponding lobe of the liver where it branches until open in the liver sinusoids. From the liver, the blood is conveyed to the inferior vena cava by 4 hepatic veins (Fig.25). The portal vein starts like a vein but ends like an artery by giving branches. The portal vein has no valves. It is 7.5 cm long. It is formed by the union of the superior mesenteric and splenic veins. 30 It runs to the liver where it branches into smaller and smaller veins that open in the liver sinusoids between cords of the liver cells. The hepatic artery brings oxygenated blood to the liver, while the portal vein brings venous blood rich in products of digestion which have been absorbed from the gastrointestinal tract to the liver to be metabolized. Products of metabolism are produced by the liver cells into liver sinusoids, and conveyed by central veins (inside liver lobules) into hepatic veins. Hepatic veins are 4 in number, 2 from each lobe that drain directly into inferior vena cava. Fig. 25: The portal circulation. 31  CARDIOVASCULAR SYSTEM Cardiovascular system is the transport system of the body (fig.26), through which the nutrients are conveyed to places where these are utilized, and the metabolites (waste products) are conveyed to appropriate places from where these are expelled. The conveying medium is a liquid tissue, the blood, which flows in tubular channels called blood vessels. The circulation is maintained by the central pumping organ called the heart. THE HEART The heart is conical hollow muscular pump (Figs. 26,27) inside the pericardium occupying a major part in the chest. It has four chambers two atria (right and left) and two ventricles (right and left). The two atria lie behind the two ventricles. The coronary groove encircles most of the upper part of the heart and seperates the atria from the ventricles, also division of the ventricles is indicated by the anterior and posterior interventricular grooves.It has an apex, base, two surfaces and four borders. The surfaces are the sternocostal and diaphragmatic. The borders are right, left, upper and lower borders. ♦Apex is formed only by the left ventricle and is directed downwards, forwards and to the left. Pulsations of the apex can be felt below nipple of the left breast, in the left 5th intercostal space. ♦Base is formed mainly by the left atrium and the back of the right atrium. It is directed backwards and to the right. lt has a quadrilateral shape and lies opposite the bodies of middle thoracic vertebrae (5-8). ♦Sternocostal surface is directed forwards, upwards and to the left. It is divided by the coronary groove into: 1. Atrial Portion: It is formed mainly by the right auricle and a small part of the left atrium. 32 2. Ventricular Portion: One third of this surface is formed by left ventricle, and two thirds by the right ventricle. Fig. 26: The heart (Anterior view). ♦Diaphragmatic (inferior) surface: It is directed downwards and slightly backwards. It is located upon the central tendon of the diaphragm which separates it from stomach and liver. It is formed by the two ventricles; two thirds by the left ventricle and one third by the right ventricle. ♦Upper border: It is formed by the two atria, mainly the left. ♦Right border: It is formed only by the right atrium. ♦Lower border: It is formed by the right ventricle and the apical part of left ventricle. ♦Left border: It is formed mainly by the left ventricle and partly by the left atrium. 33 ▼▼Chambers of the heart ►Right Atrium It forms the right border of the heart between the superior and inferior venae cavae (Fig. 26). It is separated from the left atrium by the interatrial septum. The right atrium is composed of two main parts, a smooth posterior portion and a rough walled anterior portion. The anterior part is continuous anteriorly with the right auricle. In the large smooth part the following orifices are present (Fig.27): 1. The inferior vena cava opens into the lower posterior part. It brings blood from the lower limbs and abdomen to the right atrium. 2. The superior vena cava opens into the upper posterior part. It brings blood from head, neck, upper limbs and thorax. 3. Tricuspid valve connects the right atrium with the right ventricle. It is guarded by three cusps. 4. The coronary sinus opens in front and to the left of inferior vena cava.It conveys venous blood from the heart wall to the right atrium. Fig. 27: The heart (Posterior view). 34  Fig. 28: Interior of the right atrium. ►Left Atrium: The left atrium forms the greater part of the base of the heart (Fig. 27). It lies behind and to the left of the right atrium. It interior presents a smooth surface except for little rough part. The left auricle lies to the left and in front of the pulmonary trunk. The left atrium shows the following orifices: 1. The four pulmonary veins two from each lung. 2. The mitral valve connects the left atrium with the left ventricle. ►Right ventricle forms the largest part of the sternocostal surface and a small part of the diaphragmatic surface.It is separated from the left ventricle by interventricular septum. Its wall is muscular and is thicker than the atrial wall. The pulmonary trunk arises from the right ventricle and divides into two pulmonary arteries one to each lung. There are three papillary muscles attached to the wall of the ventricle. From the apices of the papillary muscles, fibrous cords (chorda tendinae) pass to the cusps of the tricuspid valve (Fig. 29). 35  Fig. 29: Interior of the heart. ►Left ventricle is longer than the right ventricle and forms the apex of the heart, its left border, ⅓ of its sternocostal surface and ⅔ of its diaphragmatic surface. Its wall is nearly three times thicker than the right. The ascending aorta arises from it. The wall of the ventricle showed trabeculae carneae, and has 2 papillary muscles (Fig. 29). ►Pericardium is the fibroserous sac which encloses the heart and the roots of its great vessels. It consists of an outer fibrous sac lined with an inner serous sac. The heart lies inside the fibrous sac and invaginates the serous sac from behind. So the serous pericardium has a visceral layer covering the heart and a parietal layer lining the fibrous pericardium. The fibrous pericardium limits movements of the heart. ▼▼Conducting system of the heart The conducting system of the heart consists of modified cardiac muscle fibers which are responsible for initiation and maintenance of cardiac rhythm. The conducting system (Fig. 30) is formed of: 36 1. Sino-atrial node (SAA) is horse-shoe shaped band in the lateral wall of the right atrium. It is supplied by the right vagus nerve. 2. Atrioventricular node (AVN) is situated in the interatrial septum. It is supplied by the left vagus nerve. 3. Atrioventricular bundle (AVB) is a slender bundle which extends from the A-V node to Fig. 30: Conducting system of the the interventricular septum. heart. Then it divides into right and left bundle branches. ▼▼Blood supply of the heart The heart is supplied by two coronary arteries (right and left) which arise from the beginning of the ascending aorta. ▼▼Venous drainage of the heart The heart is drained mainly by coronary sinus and to a lesser extent by anterior cardiac vein and vena cordis minimi ►►►Main Branches of the Aorta (Fig. 31) *The ascending aorta arises from the left ventricle. It gives two coronary arteries; right and, left. The coronary arteries supply the heart. *Ascending aorta arches to give the aortic arch which gives 3 arteries: 1. Brachiocephalic artery which giyes the right subclavian and right common carotid arteries. 2. Left common carotid artery. 3. Left subclavian artery. * The carotid arteries supply the head, neck and brain, 37 *The subclavian artery continues as axillary artery, then brachial artery which divides into radial and ulnar arteries. The continuation of the subclavian artery supplies the upper limb. *The descending thoracic aorta descends in the thorax and gives branches which supply the bronchi, oesophagus and intercostal spades. The descending aorta pierces the diaphragm to become the abdominal aorta. Branches from the abdominal aorta supply the digestive system, kidneys, suprarenal glands, testes, ovaries and the diaphragm. The abdominal aorta ends at level of the fourth lumbar vertebra by givm*g two commonillac arteries. Each common iliac artery gives External and internal iliac arteries. The external iliac continues as Femoral artery which will supply the lower limb. The internal iliac artery gives branches which supply the pelvic organs (urinary bladder, rectum, uterus, and vagina). Fig. 31: The aorta 38  RESPIRATORY SYSTEM The respiratory system, which buds off the primitive gut, has two portions (Fig. 32): (1) conducting and (2) respiratory. The conducting Portion, or air passages, comprises: nasal cavities, pharynx, larynx, trachea, bronchi and bronchioles. The respiratory Portion comprises: lungs (having respiratory bronchioles, alveolar ductules, and alveoli) The respiratory system absorbs oxygen, the absorption taking place in the alveoli of the lung. Carbon dioxide is eliminated there simultaneously. ►►The conducting portion: ♦►Nasal Cavities, right and a left, are separated from each other by a thin median partition, the nasal septum. The entrance to each cavity, the nostril or naris, opens into a vestibule which is lined with hairy skin to filter the air. From the side wall of each cavity, three downward curved shelves, the conchae, overhang three antero-posteriorly running passages, the meatuses. Nasolacrimal (tear) duct opens into the inferior meatus while large air sinuses open into the other meatuses. ♦►Pharynx is a fibro muscular tube, funnel shaped which extends from the base of the skull to the level of sixth cervical vertebrae posteriorly and lower border of cricoid cartilage anteriorly. It is widest (5 cm) opposite the hyoid bone and narrowest at its inferior end where it is continuous with the oesophagus. Communicating with it from front are the nasal, oral, and laryngeal cavities. So it is divided into three parts (upper, middle, and lower), called the nasal, oral, and laryngeal parts, respectively. The nasopharynx is the backward extension of the nasal cavities. It communicates the nasal cavity with tympanic cavity and it has a respiratory function. 39  Fig. 32: Respiratory system. ♦►Larynx The larynx is continuous below with the trachea and opens at the lowest part of the pharynx. This voice box is kept rigid by a number of hyaline and elastic cartilages which are united by membranes. It is lined with mucous membrane internally and covered with voluntary muscles externally. The cartilages of the larynx are (Fig. 32): A- Single cartilages: 1. The thyroid cartilage: has two perpendicular laminae which meet in front in the middle as the laryngeal prominence (Adam's apple). 2. The cricoid cartilage: is a complete ring expanded posteriorly into a lamina or plate and so resembles a signed ring. 3. The epiglottic cartilage is leaf, attached to angle of the thyroid cartilage. 40  cartilage. Fig. 33: Cartilages of the larynx. B -Paired cartilages: 1. The arytenoid cartilages: are paired, small, and pyramidal cartilages their bases articulate with the upper border of the lamina of the cricoid cartilage. 2. Corniculate cartilages: one on each side, small nodule of cartilage articulates with apices of arytenoid cartilage. 3. Cuneiform cartilages: are two small, rod –shaped pieces of cartilage lying in front of the corniculate cartilage. ♦►Trachea or windpipe is an elastic tube about 10 cm long. It is kept patent by about 20 U-shaped rings of hyaline cartilage which are opened posteriorly. At the level of the sternal angle, the trachea bifurcates into right and left bronchi. ♦►Bronchi: Each bronchus, having an oblique course, enters the respective lung at the hilus and descends towards the base, giving off branches which in turn branch like a tree. The bronchi have the same structure as the trachea. When the bronchi are reduced to the diameter of 1 mm, they are called bronchioles. The terminal bronchioles divide 41 into a number of alveolar ductules (2 to 11) which end in dilated air sacs (alveolar sacs). The right bronchus is short (2.5 cm) wide and on the same line with the trachea. The left bronchus is longer (5 cm), narrower and more oblique than the right. ♦►The lungs: The right and left lungs are conical in shape (fig. 34). It has an apex and base, costal and medial surfaces, anterior and inferior borders and a hilus. Apex is directed upwards and projects into the root of the neck. Base is concave and directed downwards where it is related to the diaphragm. Anterior border is sharp and thin. Lateral (costal) surface is convex and is related to the ribs and intercostal spaces. Medial surface contains the hilum of the lung, and is divided into mediastinal and vertebral parts: a) Mediastinal part: is related to the side of the mediastinum (the heart and pericardium) and has the hilum in its posterior. The hilus of the lung transmits the main bronchus, one pulmonary artery and two pulmonary veins. b) Vertebral part: lies behind the hilum and is related to the side of the vertebral column. ▼▼▼Lobes and fissure of the lung: * Right lung: is divided into 3 lobes (upper, middle and lower) by 2 fissures (oblique and horizontal). * Left lung: is divided into 2 lobes only (upper and lower) by the oblique fissure, which is similar to the oblique fissure of the right lung 42  Fig. 34: The lungs. ▼▼▼Difference between the right & left lung: 1. The right lung is divided by two complete fissures into three lobes while the left lung is divided by one fissure into two lobes. 2. The right lung is short and broad (presence of the liver pushes the diaphragm upwards on the right side). 3. The left lung is long and narrow (the heart lies on the left side). 4. The left lung has a cardiac notch on its anterior border and a lingual just below the notch. ►►►PLEURA: Each lung is covered by a delicate smooth serous membrane, the visceral pleura. Another layer of pleura lines the ribs, diaphragm, and mediastinum, this is the parietal pleura. Both the parietal and visceral pleura are continuous at the hilum of the lung. The potential space between the parietal and visceral pleura is the pleural cavity. 43  Diaphragm The diaphragm forms a musculofibrous partition between the thoracic and abdominal cavities. It has convex upper surface which forms the floor of the thoracic cavity. Its concave lower surface forms the roof of the abdominal cavity. The diaphragm takes origin from the circumference of the outlet of the thorax. The fibers converge from their origin to be inserted into the central tendon of the diaphragm. This is a thin, but strong, aponeurotic tendon formed of interlacing fibers which run in different directions. Action: The diaphragm is the chief muscle of inspiration. It also has an important role in expulsive acts e.g. defecation, urination and parturition. Major openings in the diaphragm (fig.35): 1- Vena caval opening: At the level of eighth thoracic vertebra. 2-Oesophageal opening: At the level of tenth thoracic vertebra. 3- Aortic opening: At the level of the last thoracic vertebra. Fig. 35: Major openings in the diaphragm. 44  URINARY SYSTEM The urinary system is composed of 2 kidneys, 2 ureters, urinary bladder and urethra. 'The kidneys excrete urine. This passes down two muscular tubes, the ureters, into the urinary bladder which is a muscular organ. The urine is stored the urinary bladder and is discharged through the urethra. ♦►THE KIDNEY (fig.36) Kidneys position: The kidneys lie on the posterior abdominal wall, one on each side of the vertebral column, behind the peritoneum. Each kidney extends from the level of the 12th thoracic vertebra to the level of the 3rd lumbar vertebra with its long axis directed downwards and laterally. The right kidney is slightly lower than the left one. Shape, size & features: Each kidney is bean shape, about 12 cm in length, 6 cm in width and 3 cm in thickness. It has 2 borders (medial and lateral), 2 surfaces (anterior and posterior) and 2 ends (upper and lower). A B Fig. 36: Urinary system. A) In female. B) In male. 45  The lateral border is convex, the medial border is convex at both ends and concave in the middle and presents the hilum of the kidney which gives passage to the renal vessels and nerves and the pelvis of the kidney. The anterior surface faces forwards and laterally. In the right side, this surface is related to the right suprarenal gland, second part of duodenum, right lobe of liver, right colic flexure and coils of small intestine. In the left side, the anterior surface is related to the left suprarenal gland, the spleen, the body of pancreas, the stomach, the descending colon and coils of small intestine. The posterior surfaces of the kidneys face backwards and medially. It is related to the diaphragm, and muscles of posterior abdominal wall. The kidney is surrounded by a thin fibrous capsule. The tissue of the kidney is differentiated into an outer cortex and an inner medulla. The cortex lies under the capsule. Cortical tissue also extends between the pyramids of the medulla. The medulla is formed of 10 to 18 pyramids. The base of each pyramid is directed towards the cortex. The apex of the pyramid projects into the renal sinus. Pelvis of the kidney is a dilated sac which occupies the renal sinus. It extends outside the hilum to be continuous with the ureter. Coverings of the kidney: 1) Fibrous capsule is closely surrounds the kidney, and is continuous into the renal sinus to line its walls. 2)Perirenal (perinephric)fat: It lies just to the outside of the capsule. 3) Renal fascia. 4) Pararenal (paranephric) fat: It is a large mass of fat situated outside the renal fascia especially behind the kidney. Arteries of kidneys: Right and left renal arteries from abdominal aorta. 46 ♦►URETERS The ureters are two muscular tubes one on each side. They convey urine from the kidneys to the urinary bladder. Each is 25 to 30 cm in length. Half of its course is in the abdomen, while the other half is in the pelvis. The ureters begin inside the sinus of the kidney in the form of a dilated part called the renal pelvis. They descend on the posterior abdominal wall opposite tips of the lumber transverse processes. The ureters enter the pelvis and curve forwards and medially to reach the posterosuperior angle of the urinary bladder, where they open with a valve like opening. The ureter passes obliquely in the wall of the bladder for 1 inch before it opens into its cavity at the lateral angle of the trigone. This part of the ureter is the narrowest and is called the intramural part. Another two sites of anatomical constrictions in the course of the ureter are at the pelvi-ureteric junction and where the ureter crosses the common iliac artery. At these sites, stone impaction may occur. ♦►URINARY BLADDER It is a hollow viscus with strong muscular wall which serves as a reservoir for urine. Position:-The urinary bladder lies in the pelvic cavity directly behind the pubic bones, only separated from them by the retropubic space. Shape: It is pyramidal in shape with an apex (directed anteriorly), base (directed posteriorly) and 3 surfaces. It has the capacity of 220cc but can accommodate up to 500 cc without discomfort. Apex lies behind the upper part of the symphysis pubis. It is continuous with the median umbilical ligament (the fibrosed urachus of the foetus). The base triangular in shape in the male is related to the seminal vesicles and ampulla of vas deferens on each side. 47 In female it is related to the cervix of the uterus and anterior wall of the vagina. The superolateral angles of the base are joined by the ureters, and the inferior angle gives rise to the urethra. The neck in male, the neck rests on the prostate gland and continuous with the prostatic part of the urethera, in female it is Fig. 37: Urinary bladder. continuous with the urethra. The surfaces of the bladder are one superior and two inferolateral, each one is triangular in shape. In male, the superior surface is related to the pelvic colon and coils of small intestine. In female it is related to the anterior surface of the uterus and coils of small intestine. Internal urethral orifice: It is Fig. 38 placed at the lowest part of the bladder. It is surrounded by an involuntary non-striated muscle forming the sphincter vesicae. Arteries of the urinary bladder: 1 - Superior vesical artery. 2- Inferior vesical artery. 48 ♦►MALE URETHRA Shape & course: The male urethra is S-shaped, 20 cm. in length. It extends from the internal urethral orifice at the neck of the urinary bladder to the external urethral orifice at the tip of the penis. Division: It is divided into 3 parts: prostatic, membranous and spongy. 1) Prostatic urethra: It measures 3 cm in length. It is the widest and most dilatable part of the whole urethra. It passes downward and forward through the prostate gland from its base and emerges from anterior aspect of the prostate a little above its apex. The ejaculatory ducts open into the prostatic urethra. 2) Membranous urethra: It is 1-2 cm long. It extends from the apex of the prostate to the bulb of the penis, being placed 1 inch below and behind the pubic symphysis. 3) Spongy (penile) urethra: It is 15–16 cm in length long. It extends from the end of the membranous urethra where it receives the ducts of the two bulbo-urethral glands. It ends at external urethral orifice on the glans penis. ►►Sphincters of the urethra: 1) Internal urethral sphincter (sphincter vesicae): consists of non- striated muscle fibers (involuntary), and surrounds the internal urethral orifice and neck of the bladder. 2) External urethral sphincter (sphincter urethrae): consists of striated muscle fibers (voluntary), and surrounds the membranous urethra ♦►FEMALE URETHRA: It is 4 cm long. It begins at the internal urethral orifice and opens into the vestibule of the vagina by the external urethral orifice which lies directly in front of the vaginal orifice, 1 inch below and behind the clitoris. 49  REPRODUCTIVE ORGANS THE MALE GENITAL SYSTEM The male reproductive organs are: The testes, epididymes, ductus deferens, seminal vesicles, ejaculatory ducts, prostate and bulbo- urethral glands. The external genital organs are the penis and the scrotum (fig.39). ♦►SCROTUM: It is a sac of skin containing the 2 testes and lower parts of the spermatic cords (of both sides). ▪Arterial supply: External pudendal arteries (superficial and deep): from the femoral artery. ▪Nerve supply: Ilio-inguinal nerve (L1). ▪Lymphatic drainage: The wall of the scrotum drains into the superficial inguinal lymph nodes ♦►TESTIS The testis is the primary male sex organ which lies in the scrotum, one on each side of the median septum. It measures 5 cm in length and 2.5 cm in breadth and 3cm in anteroposterior diameter is suspended by the spermatic cord. It is oval in shape having 2 borders (anterior and posterior), 2 ends (upper and lower) and 2 surfaces (lateral and medial). Each testis has anterior and posterior borders, and 2 surfaces, medial and lateral. It has a thick fibrous capsule, the tunica albuginea. The testis is composed of numerous convoluted, seminiferous, tubules. Each tubule is about 2 feet in length. They produce the male sex cells, the sperms. From the upper part of the testis, about 6-12 fine ducts (efferent ductules) arise. They open into the duct of the epididymis (fig.40). The testes are present in the scrotum where the temperature is less than that of the body to favour the process of spermatogenesis (formation of spermatozoa). 50  Fig. 39: Male genital system. ♦►TUNICA VAGINALIS: The tunica vaginalis is formed by the terminal blind end of the processus vaginalis which is invaginated by the testis. This processus vaginalis is an evagination of peritoneum which extends into the inguinal canal down to the scrotum in the fetus. Blood supply and lymphatic drainage of the testes: ▪Arterial supply: by the testicular artery from abdominal artery. ▪Venous drainage: The right testis drains into the inferior vena cava while the left testis drains into the left renal vein. ▪Lymphatic drainage: into the lateral aortic lymph nodes. ♦►EPIDIDYMIS(fig.40): It is a highly coiled duct that lies on the posterior border of the testis. It has the following parts: 1) An expanded head caps the upper pole of the testis where it is connected with the efferent ductules. 2) A body. 3) A narrow tail attached to the lower end of the testis and is continuous with the ductus deferens. 51 The epididymis secretes the mucoid secretions which carry the spermatozoa. Spermatozoa are stored and matured in the epididymis until ejaculated. ♦►SPERMATIC CORD ▪Position: It lies in the inguinal canal as well as in the scrotum.It extends from the lower end of the testis (below) to the deep inguinal ring (above) where the ductus deferens enters the pelvis. The left cord is a little longer than the right one. ▪Contents: 1) Ductus (vas) deferens: It is the duct which transfers the sperms from the testis, and is characterized by having a thick muscular wall and a narrow lumen. Each vas deferens connects the duct of the epididymis to the urethra. It is 45 cm long. It ascends through the spermatic cordto the abdominal wall, where it passes into the pelvis from the deep inguinal ring. On the pelvic wall, it lies behind the peritoneum to reach the base of the urinary bladder. It unites with the duct of the seminal vesicle to form the ejaculatory duct. 2) Artery of the ductus deferens. 3) Vessels and nerves of the testis. a- Testicular artery: arises from the abdominal aorta b- Sympathetic fibers: surround the testicular artery forming the testicular plexus. c- Pampiniform plexus of veins: this is a plexus formed by several veins which emerge from the back of the testis. d- Lymph vessels: drain the testes and epididymis and accompany the testicular blood vessels up to the lateral aortic lymph nodes. 4) Vestige of the processus vaginalis: It is a fibrous strand which represents the obliterated remains of the processus vaginalis 52 ♦►THE EJACULATORY DUCTS: Each ejaculatory duct is 2 cm long and pierces the prostate to open into the prostatic urethra close to its fellow. ♦►THE SEMINAL VESICLE (fig.41): The seminal vesicles are two pear shaped lobulated pouches that secrete alkaline secretion of the seminal fluid. Each is 5 cm long. They lie on each side of the base of the urinary bladder. Their ducts unite with the ductus deferens to form the ejaculatory ducts. ♦►THE PROSTATE: The prostate is a fibromuscular accessory gland which encircles the neck of the urinary bladder. It is conical in shape, having a base, an apex, anterior, posterior, and two inferolateral surfaces. The base is directed upwards, continuous with the neck of the urinary bladder. The apex is directed downwards. The prostate measures 4 cm in the transverse diameter, 3 cm in the vertical diameter and 2 cm in the anteroposterior diameter. The prostate produces the majority of the volume of the seminal fluid. Secretions of the prostate are rich in enzymes which liquefy the semen to allow sperms to travel the female genitalia. ♦►THE BULBOURETHRAL GLANDS: A pair of pea sized yellowish glands. They lie within the sphincter urethra. Their ducts open into the spongy part of urethra. ♦►THE PENIS: The penis is formed of two main parts, the root which lies in the perineum and the body which is the free part of the penis. Its anterior end is enlarged to form the glans penis. The body is formed of three elongated erectile bodies, one ventral and two dorsal. The ventral body is the corpus spongiosum, and the dorsal bodies are the corpora cavernosa.The root is formed of a bulb and two crura. The bulb is the posterior expanded part of the corpus spongiosum. The crura are the 53 posterior parts of the corpora cavernosa. The urethra traverses the corpus spongiosum. Fig. 40: Cut section in the testis and epididymis. Fig. 41: Prostate, seminal vesicle and Ejaculatory duct.. 54  THE FEMALE GENITAL ORGANS The female reproductive organs are two ovaries, two uterine tubes, a uterus and a vagina. The parts of external genitalia are clitoris, mons pubis, labia majora, labia minora, greater vestibular glands and vaginal orifice. ♦►OVARY Position: ovaries are present in the pelvis, in the ovarian fossa, one on each side of the uterus, on the back of broad ligament. Shape and size: The ovary is almond-shaped. It is about 5 cm long 1.5 cm wide and 1 cm in thickness. Features: It has smooth surface before puberty, become irregular with aging. At birth each ovary contains about 200,000 immature ova, from puberty to the end of reproductive period, one ovum is released every other months from each the ovary. The monthly release of an ovum is called ovulation. UTERUS Shape and site: The uterus is a thick-walled muscular pear-shaped organ situated in the lesser pelvis between the rectum behind and urinary bladder in front. Size: It measures 3 inches in length, 2 inches in width and 1 inch in thickness. Openings: Above, a uterine tube opens into the uterus on each side, below the uterus opens into the vagina. Divisions: The uterus is divided into 3 parts, fundus, body and cervix. Fundus: It is the part above the entrance of the uterine tubes. It is convex in all directions and related to coils of small intestine. Body: It is formed of a main part (2 inches long) and the cervix. It narrows from the fundus to the cervix. Its anterior surface is flattened; its posterior surface is convex. 55 Cervix: It is about 1 inch long and 1 inch thick. It projects through the vagina, so its upper ½ is above the vagina (supravaginal part) and the lower ½lies inside the vagina (vaginal part). It is more cylindrical than the body and more fixed by ligaments. The cavity of the cervix, the cervical canal, is spindle shaped and communicates with cavities of the uterus and vagina through the internal os and the external os, respectively. N.B.: The wall of the uterus consists of 3 layers: 1. Perimetrium: The outer coat of peritoneum. 2. Myometrium: The middle muscular coat, 12-15 mm. thick. 3. Endometrium: The inner mucous coat. During the fertile period of female (13 years - 45 years) the endometrium. exhibits cyclical changes every 4 weeks. these changes take place to prepare the endometrium each month to receive a fertilized ovum, so pregnancy may occur. If implantation does not occur shedding of the endometrium occurs (menstruation) which is followed by repair and a new cycle. These cyclical changes of the endometrium of the fertile female are called the menstrual cycle. Position of the uterus: The uterus is usually not exactly in the median plane. Its fundus is slightly tilted to the right, while the cervix and upper part of vagina are slightly tilted to the left. The position of the uterus is described as being anteflexed and anteverted which means the following: 1- Anteflexed position: the body of the uterus bent forwards on itself at the level of internal os to form an angle of about 170. 2- Anteverted position: the long axis of the whole uterus (body and cervix) makes a right angle with the long axis of the vagina. This angle faces forwards and downwards. In some women, the uterus may acquire an abnormal position of retroversion and retroflexion. 56 Blood supply of the uterus: 1) Uterine artery is a branch of the internal iliac artery. 2) Uterine vein ends in the internal iliac vein ♦►UTERINE TUBES The Fallopian tube is 10 cm long, and lies in the free anterior border of the broad ligament. It extends laterally from the lateral angle of the uterus to the ovary where the tube curves around it. It has 2 openings: a medial opening into the uterine cavity, and a lateral or abdominal opening which opens into the peritoneal cavity. The abdominal opening is funnel shaped (the infundibulum). The uterine tube receives the ovum from the ovary and propels it into the uterine cavity. Parts of the Fallopian tube: The uterine tube has 4 parts: uterine part, isthmus, ampulla and infundibulum (from medial to lateral). Arterial supply: by the uterine artery and ovarian artery. Venous drainage: into ovarian and uterine veins. ♦►VAGINA: It is a collapsed musculomembranous canal which connects the uterus with the vestibule. It lies between the bladder and the urethra anteriorly and the rectum and anal canal posteriorly. It anterior wall is 7 cm and its posterior wall in 9 cm. The anterior wall is pierced by the cervix. The vagina forms a gutter around the cervix known as vaginal fornices. Arterial supply: by the 1) Vaginal artery. 2) Uterine artery. Venous drainage: into vaginal vein which drains into internal iliac veins and communicates with vesical, uterine and rectal venous plexuses. 57  Fig. 42: Female reproductive organs,coronal section.. Fig. 43: Female reproductive organs, sagittal section.. VULVA The external genital organ of female is the vulva. The vulva consists of: 1. Mons pubis: Hairy fatty elevation of skin in front of the pubic bones. 2. Clitoris: Highly sensitive organ of 2-3 cm and is located anteriorly in the vulva. 58 3. Labia majora: two large hairy folds of skin that provide protection for the urethral and vaginal orifices. 4. Labia minora: Two small hairless folds of skin that lie between the labia majora. Labia minora encloses the vestibule of the vagina. 5. Vestibule of the vagina: Is a triangular area bounded laterally by ,the labia majora and anteriorly by the clitoris. In the vestibule, the urethral orifice opens in front of the vaginal orifice and is present 2 cm. behind the clitoris. In the virgin, the vaginal orifice is protected by a mucous fold that has a central opening and is known as the hymen. NERVOUS SYSTEM (NS) Fig. 44: Normal position of the uterus. 59  NERVOUS SYSTEM (NS) It consists of highly specialized cells that transmit information rapidly between various parts of body. It is divided into two parts: central nervous system (CNS) and peripheral nervous system (PNS). Brain and spinal cord constitute CNS which lies within the skull and vertebral canal. Cranial and spinal nerves of PNS connect CNS with all other parts of the body. CNS is collection of nerve cells connected in a complex fashion to do functions of nervous system; thought, language, emotion, control of movement and analysis of sensation. Cellular Structure: Basic cellular unit of NS is the nerve cell or neuron Neurons differ in size and shape according to their function and location, but all neurons have three characteristic components: a cell body, an axon, and dendrites. Cell body of a neuron is an expanded portion of the cell which contains the nucleus (fig.45) and apparatus necessary to sustain metabolic activities of the cell. Axon is longitudinal, tubular process of cell membrane and cytoplasm; and transmit information away from cell body. Dendrites are processes of the cell membrane that radiate from the cell Fig. 45: Nerve cell. body in various directions, and are receiving information and transmitting it to the cell body. 60 Dendrites differ from axons as they typically undergo extensive branching very close to the cell body. Axons, in contrast, remain singular for most of their course; do not branch until their ends are away from parent cell body. Neuron has only one axon, several dendrites. Lengths and caliber of axons and dendrites vary depending on function of neuron. CENTRAL NERVOUS SYSTEM CNS is formed of the brain and the spinal cord both are centrally located and protected by bones of the skull and vertebral column. I- BRAIN: The brain is enclosed inside the skull and 3 meninges, which protect it. The brain is formed of the following parts. a) Cerebrum: This is formed of two hemispheres connected by fibers called the corpus callosum. Each cerebral hemisphere is formed of an outer gray matter and an inner white matter. The gray matter is formed mainly of nerve cells with some nerve fibers. It is called the cerebral cortex. The cerebral cortex contains the motor and sensory areas as well as memory and psychic areas. The inner white matter is formed mainly of nerve fibers. Fig 46: Central nervous system. Within the white matter masses of gray matter appears forming the basal ganglia (a group of nuclei involved in the control of movement). The most important basal ganglia are the caudate and lentiform nuclei. 61 The surface of the cerebral cortex shows convolutions known as gyri separated by sulci. This increases the surface area of the cortex. The cerebral cortex contains about 14 billion nerve cells. Each cerebral hemisphere is divided into 4 lobes which are: 1-The frontal lobe: It is located anteriorly. It contains the motor area of the brain. 2-The parietal lobe: It is located posterior to the frontal lobe. It contains the sensory area of the brain. Fig 47: Lobes of the cerebral hemisphere (lateral surface). 3-The occipital lobe: It is located posteriorly. It contains the visual area. 4-The temporal lobe: It is located inferiorly (fig. 47). It contains the auditory area (hearing). b) The cerebellum is mass of neural tissue, control posture, repetitive movements and geometric accuracy of voluntary movements. It is located inferior to the occipital lobe. It consists of two cerebellar hemispheres on each side connected together by a median part called the vermis. Like the cerebrum, the cerebellum has an outer cortex (gray matter) and inner medulla (white matter). The medulla contains masses of gray matter called the nuclei of the cerebellum (e.g. the dentate nucleus). The cerebellum is connected to the brain stem by three pairs of masses of nerve fibers called peduncles. These peduncles are: 1-The superior cerebellar peduncles connect the cerebellum with the midbrain. 62 2-The middle cerebellar peduncles connect the cerebellum with the pons. 3-The inferior cerebellar peduncles connect the cerebellum with medulla. c) The brain stem: It is a stalk-like structure which connects the brain with the spinal cord. It is formed of three different parts: 1- The midbrain: It connects the cerebrum with the pons. It is connected with the cerebellum by the superior cerebellar peduncle. 2- Pons: It connects the midbrain with the medulla oblongata It is connected with the cerebellum by the middle cerebellar peduncle. 3- Medulla oblongata: It connects the pons with the spinal cord. It is connected with the cerebellum by inferior cerebellar peduncle. Cerebral hemisphere Corpus callosum Brain stem cerebellum Beginning of the spinal cord Fig 48: Medial surface of the cerebral hemisphere. 63  II- SPINAL CORD Long thick cable formed by thousands of longitudinally running axons surrounding a central core of gray matter. The spinal cord is the continuation of the medulla oblonagata. It is enclosed within meninges inside the upper part of the vertebral canal. It is divided into 31 segments: 8 Cervical segments, 12 Thoracic segments, 5 Lumber segments, 5 Sacral segments, and 1 Coccygeal segment. A pair of spinal nerves arises from each segment of the spinal cord. Fig 49: Spinal cord The spinal cord is formed of an outer layer of white matter and an inner layer of gray matter. The gray matter is H shaped. The two anterior (horns) limbs contain motor cells and the two posterior horns contain sensory cells. About 45 cm. long and occupies vertebral canal at cervical, thoracic and upper lumbar levels. Width of spinal cord is not uniform along its length, expanded below its rostral end and near its caudal end. This occurs at levels of spinal cord responsible for innervation of upper and lower limbs; cervical and lumbar enlargement. 64 Fig.50: General arrangement of somatic part of nervous system (left) compared to autonomic part of nervous system (right). Central core of spinal cord consists of gray matter, central area surrounding central canal of the spinal cord, central gray matter, projecting dorsolaterally and ventrally from this central area are extensions of gray matter, dorsal (post.) and ventral (ant.) horn. Ventral horns on each side are formed by cell bodies of neurons that innervate voluntary muscles, axons of these cells leave spinal cord through ventral roots. Dorsal horns consist of cells concerned with processing of sensory information, enters spinal cord through dorsal roots. Between T1 and L2 segments of spinal cord, a horn of gray matter projects laterally in angle between dorsal and ventral horns on each side, lateral horn, contains cell bodies of neurons, axons of which constitute part of autonomic nervous system. 65 Peripheral part of spinal cord consists of white matter formed by axons arranged in tracts that convey information to or from brainstem, or between different segments of spinal cord. ♦►The Meninges: Although glial (supporting) cells hold neurons of CNS together and afford them protection against metabolic insults, the CNS is a soft, cellular mass. So, it is vulnerable to external, mechanical insults which might arise where it freely mobile within the skull or vertebral canal. To protect against such insults, CNS is surrounded by 3 membranes, collectively called meninges, and is bathed in cerebrospinal fluid. ♦►Cerebrospinal Fluid (CSF): It is a clear watery fluid filling subarachnoid space (fig.51). It is secreted by capillaries that project into lateral, 3rd and 4th ventricles of the brain. Fig. 51: Circulation of CSF. 66  It fills cavities of CNS and emerges through apertures in roof of 4th ventricle to fill subarachnoid space. Secreted continuously and reabsorbed into bloodstream, reabsorption occurs through extensions of arachnoid mater, arachnoid granulations, that pierce dura mater of falx cerebri and project into superior sagittal sinus. NB: Cervical spinal cord segments remain related to their vertebrae, with cervical nerve roots more or less retaining their original transverse course (fig. 49). Upper thoracic spinal cord segments are displaced from their respective intervertebral foramina by about one segmental level and progressively lower spinal cord segments are displaced until S5 spinal segment lies 10 vertebral segments shorter than S5 intervertebral foramen. Below caudal tip of spinal cord, L2 to Co1 nerve roots form a leash of nerves hanging freely in dural sac, cauda equine (fig.49). PERIPHERAL NERVOUS SYSTEM (PNS) This is formed of the peripheral nerves (cranial and spinal). Spinal nerves tend to form plexuses which are the cervical, the brachial, the lumbar and the sacral plexuses. Cranial nerves are 12 pairs of nerves. Peripheral tissues of body can be classified into structural components that give body its shape or external form, and internal organs, or viscera. Structural tissues, such as bone, muscle and skull are referred to collectively as somatic structures, and the nerves that supply these tissues are called somatic nerves. Nerves that supply the viscera, such as heart, lungs and digestive tract, can be called visceral nerves. 67  Because nervous functions concerning viscera are largely automatic and subconscious, that part of NS that innervates viscera is called autonomic nervous system, has components in both CNS and PNS. ►►Constituents of Peripheral Nerves: Peripheral Nerves are composed of different types of axons that are classified according to their size, function, or physiological characteristics. Classification of axons recognizes afferent (sensory) fibers and efferent (motor) fibers. 1. CRANIAL NERVES: Certain nerves project from cranial portion of CNS. They connect brainstem and diencephalon with various structures and tissues in head and heck, and with various thoracic and abdominal viscera. While inside the skull, these nerves constitute part of CNS and become peripheral nerves only once they leave the skull. They are 12 pairs of cranial nerves, known by number or by a name: the name usually reflects form, function or distribution of the nerve. The cranial nerves are: 1-The first (I), the olfactory nerve. It is purely sensory and mediates perception of smell from the nose. 2-The second (II), the optic nerve. It is purely sensory and transmits visual information from ipsilateral retina. 3-The third (II), the oculomotor nerve. It is motor to some muscles of the eye. It has parasympathetic fibers which constricts the pupil. 4-The fourth (IV), the trochlear nerve. It is purely motor. It supplies a single muscle (superior oblique muscle) of the eye. 5-The fifth (V), the trigeminal nerve. It is divided into three branches; Ophthalmic, maxillary, and mandibular. It is sensory to the skin of the face and motor to muscles of mastication. 68 6-The sixth (VI), the abducent nerve. It is purely motor and innervates lateral rectus muscle of the eye which is responsible for abducting the eye. 7-The seventh (VII), the facial nerve. It is a mixed nerve. It is motor to muscles of the face (muscles of facial expression) and carries taste sensation from the anterior two thirds of the tongue. It has parasympathetic secretory fibers to the lacrimal, submandibular and sublingual salivary glands. 8-The eight (VIII), the vestibulocochlear nerve. It is purely sensory. has 2 components: vestibular & cochlear. Cochlear part arises in cochlea of inner ear, responsible for hearing. Vestibular part innervates vestibular apparatus of inner ear, responsible for sense of balance. 9-The ninth (IX), the glossopharyngeal nerve. It carries the taste sensation from the posterior 1/3 of the tongue. It provides sensory supply to the pharynx It is also motor to one muscle (stylopharyngeus) in the pharynx. It has parasympathetic fibers to the parotid gland. 10-The tenth (X), the vagus nerve, has a diverse distribution including sensation of mucosa of larynx, motor to smooth muscles of much of viscera of chest and abdominal viscera. It carries parasympathetic inhibitory fibers to the heart. IX and X cranial nerves also innervate carotid body and carotid sinus, so, involved in cardiovascular reflexes. 11-The eleventh (XI), the accessory nerve, has two components: a cranial and a spinal part. The two join for a short distance, but fibres of the cranial part are transferred to vagus nerve through which it is distributed to muscles of pharynx, larynx and soft palate. Spinal accessory nerve supplies sternomastoid and trapezius muscles. 12-The twelfth (XII), the hypoglossal nerve, is motor to the muscles of the tongue. 69 2. SPINAL NERVES: They are short nerves that lie within intervertebral foramina of vertebral column. Outside vertebral column they form elements of PNS, but within vertebral canal each spinal nerve is connected to spinal cord by central and dorsal nerve roots which are components of CNS. There are 31 pairs of spinal nerves, each being named according to one segment of the spinal cord from which it arises. Each nerve is formed of an anterior root (motor arising from anterior horn cells) and posterior root (sensory reaching the posterior horn cells). The two roots unite to form the trunk of the nerve which is mixed. The nerve trunk is divided into an anterior ramus and a posterior ramus. Each ramus is mixed. Each spinal nerve carries different sensations from the skin, muscles and deeper structures as well as motor fibers to skeletal muscles. Sensory fibers relay in spinal ganglia before entering the cord. The spinal nerves tend to form plexuses in regions supplying the limbs.these plexuses are cervical, brachial, lumbar and sacral plexuses. Autonomic Nervous System (fig.52) The autonomic nervous system is the part of the nervous system concerned with the innervation of involuntary structures such as the heart, smooth muscles and glands throughout the body. It is divided into 2 parts: sympathetic and parasympathetic. The two systems differ in where they are connected to CNS: ►Parasympathetic nerves emerge from the CNS in cranial nerves Ill, VII, IX and X, and in S2-S4 spinal nerves. So, parasympathetic nerves are having cranio- sacral outflow. Activities of the parasympathetic system aim at conserving and restoring energy of the body. 70 ►Axons of sympathetic nervous system emerge from spinal cord in T 1 L2 spinal nerves. So, sympathetic nerves are having thoraco-lumbar outflow. It prepares the body for emergency. Fig. 52: Autonomic nervous system 71  Endocrine Glands Endocrine glands or ductless glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. The main endocrine glands include the pituitary gland, pancreas, ovaries, testes, thyroid gland, and adrenal glands(fig.53). ►♦The pineal gland is located in the diencephalon. Its primary hormone is melatonin, which influences daily rhythms and may have an antigonadotropic effect in humans. ►♦Hypophysis cerebri (Pituitary gland) is a small gland about the size of a pea hanging by a stalk, the infundibulum, which forms the floor of the third ventricle of the brain. It rests on the deeply concave body of the sphenoid bone in the region behind the nasal cavities. It is made up of two lobes, an anterior and a posterior, entirely different from one another functionally. The anterior lobe forms most of the gland. It produces several trophic hormones which because of their influence on other endocrine glands have caused the hypophysis cerebri to be referred to as "master gland". The posterior lobe is a down growth from the brain and produces secretions which stimulate contraction of the uterus (oxytocin) and the retention of water in the body (antidiuretic hormone). ►♦Thyroid gland lies in front of the neck. The thyroid gland consists of 2 lobes and an isthmus. The thyroid gland secretes thyroid hormone (thyroxin) which is concerned with stimulation of metabolism of the body. When produced in excessive quantities, it disturbs the normal rate at which the cells of the body function; and this is called thyrotoxicosis. 72 ►♦Parathyroid glands The parathyroid glands are 4 small ovoid bodies, two on each side. They lie on the back of the thyroid gland. They regulate the relative amounts of calcium in the blood and in the bones. Fig.53: Endocrine glands. ►♦Thymus gland This gland, an essentially elongated bilobed gland, lies behind the manubrium sterni, and in front of the great vessels above the heart. The thymus is largest and most active during the neonatal and pre- adolescent periods. By the early teens, the thymus begins to atrophy and thymic stroma is replaced by adipose (fat) tissue. It resembles a lymphoid organ and no hormone has yet been isolated from it. ►♦Suprarenal (Adrenal glands) are two glands. Each one caps the top of each kidney, but they are not functionally related. It is formed of cortex and medulla. It produces a group of hormones. Some are 73 essential to life because they regulate water and electrolyte balance. The cortex secretes mineralocorticoids (aldosterone), glucocorticoids (cortisone) and small amounts of sex hormones. The medulla secretes adrenaline and nor-adrenaline. ►♦Pancreas has both an exocrine and an endocrine function. The endocrine cells are small islets of cells that release the hormone insulin and glucagon into the blood stream. These islets are called islets of Langerhans. Glandular tissue pours its exocrine secretion through the pancreatic duct into the duodenum. ►♦Testes and Ovaries not only produce the spermatozoa and ova respectively, which may be considered as exocrine function but they have an important endocrine function as well. Specialized cells release the male and female sex hormones. These regulate the sexual function of the adult person and determine the secondary sexual characters including all aspects of maleness and femaleness. The testes secret androgens (testosterone) and the ovaries secrete estrogen and progesterone. 74  BONES OF UPPER LIMB The upper limb is composed of the shoulder girdle, arm, forearm and hand. The bones of these segments are as follows(Fig.14): 1. Bones of the shoulder girdle: are the scapula and clavicle together. These 2 bones surround the upper part of the chest like a belt. 2. The bone of the arm: is the humerus. 3. Bones of the forearm are radius (laterally), and ulna (medially). 4. Bones of the hand: are the carpus, metacarpus and phalanges. THE CLAVICLE ▼▼ Functions: 1. It acts as a strut to carry the weight of the limb. It allows the limb to swing away from the trunk. 2. It transmits the weight of the upper limb to the trunk through its articulation with the sternum. ▼▼ Parts of the clavicle: It is a long bone. It has a shaft that lies horizontaly, and two ends medial and lateral. The medial end is thick and rounded and articulates with the clavicular notch of the manubrium sterni to form the stemoclavicular joint. The lateral end is fattened and articulates with the Fig: 54:The Clavicle acromion of the scapula to form the acromioclavicular joint. 75 The shaft: It presents a double curvature resembling the letter S. Its medial 2/3 is convex forwards while its lateral 1/3 is convex bachwards. Its lateral 1/3 is flattened having 2 borders (anterior and posterior) and 2 surfaces (superior and inferior). Its medial 2/3 is cylindrical having 4 surfaces (superior, inferior, anterior and posterior). SURFACE LANDMARKS: The clavicle can readily be felt beneath the skin throughout its length (the two ends and the shaft). TO IDENTIFY THE CLAVICLE RIGHT OF LEFT: Put the bone in the anatomical position with reference to your body. 1. The medial end is rounded and thick, while the lateral end is flat. 2. The anterior surface is convex in its medial 2/3, but concave in its lateral 1/3. 3. The superior surface is smooth, while the inferior surface is rough THE SCAPULA It is a flat triangular in shape (fig.55) having three borders (superior, medial and lateral), two surfaces (anterior and posterior) and three processes (spine, acromion and coracoid process). ♦BORDERS: 1) Superior border: It extends from the superior angle to the lateral angle which is represented by the glenoid cavity. It has the suprascapular notch which is transformed into a foramen by the suprascapular ligament. 2) Medial (vertebral) border: It extends from the superior angle to the inferior angle opposite the ribs from the 2nd to the 7th. 3) Lateral (axillary) border: It is directed towards the axilla and extends from the glenoid cavity to the inferior angle. 76 ♦ SURFACES: 1) Anterior (Costal) surface: It is concave and is called subscapular fossa. 2) Posterior (Dorsal) surface * It is marked by the spine of scapula which divides the surface into a supraspinous fossa (above) and an infraspinous fossa (below). ♦ARTICULATIONS: It articulates with the clavicle by its acromion to form the acromioclavicular joint and with the head of humerus by the glenoid fossa to form shoulder joint. Fig. 55: The scapula. THE HUMERUS ♦It is a long bone (fig.56). It is made up of a shaft, upper and lower ends. ►►The upper end is formed of the head, greater and lesser tuberosities. ♦The head forms a hemisphere directed medially. The anatomical neck is the line which immediately adjoins the articular surface of the head. ♦The lesser tuberosity is a projection from the anterior surface of the upper end. 77 ♦The greater tuberosity is projection at the lateral aspect of the upper end. ♦The two tuberosities are separated by the intertubercular sulcus. ♦The surgical neck is the part of the bone that joins the upper end with the shaft. ►►Shaft of humerus: It is cylindrical in its upper ½ and triangular in its lower ½. It has 3 borders (medial, lateral and posterior) and 3 surfaces (anteromedial, anterolateral, and posterior). ►►The lower end is formed of articular and non articular parts. I-Articular: a) Capitulum: A smooth rounded convex projection. It is seen on the anterior and inferior surfaces. It articulates with the head of radius. b) Trochlea: It a pulley shaped articular surface medial to the capitulum. It articulates with the trochlear notch of the ulna. Fig.56: The humerus 78 II-Non articular: a) Medial epicondyle: A projection on the medial side of the lower end. It is felt subcutaneously. b) Lateral epicondyle: A projection on the lateral side of the lower end. ►►Articulations: 1. With the glenoid cavity of the scapula by its head at the glenohumeral articulation (shoulder joint). 2. With the radius by its capitulum and with the ulna by its trochlea at the elbow joint. THE RADIUS ♦It is the lateral bone of the forearm. ♦It is a long bone made up of a shaft, an upper end and a lower end. ►►The upper end is made up of head, neck and tuberosity (fig.58). ♦The head is disc shaped. It is subcutaneous. Its upper surface is concave articulating with the capitulum. It articulates medially with the radial notch of the ulna to form the superior radio-ulnar joint. ♦Neck is constricted and cylindrical below the head. ♦Radial tuberosity is below and medial to the neck. Fig.57: Radius and ulna. 79 ►►The shaft: It has 3 borders and 3 surfaces: The borders are anterior (rounded), Posterior (sharp) and Interosseous (shape and directed medially).The surfaces are anterior surface; between the anterior and the interosseous border, lateral surface between the posterior and anterior barders and a posterior surface between the Fig.58: Lower end of posterior and interosseous borders. humerus and upper ends of radius and ulna. ►►The Lower end: It is formed of 5 surfaces. Lateral surface forming the styloid process, medial surface which has an unlar notch, lower surface, anterior surface and posterio