Introduction to Anatomy (PDF)

# Introduction of Anatomy Anatomy is the science that describes the form and structure of the organism's body. Anatomical studies can be done on dead and living bodies both macroscopically by the naked eye and microscopically by using the microscope. ## Anatomical Terms * Superficial: denotes a p...

# Introduction of Anatomy Anatomy is the science that describes the form and structure of the organism's body. Anatomical studies can be done on dead and living bodies both macroscopically by the naked eye and microscopically by using the microscope. ## Anatomical Terms * Superficial: denotes a position nearer to the surface (skin). * Deep: means a position farther away from the surface. * Superior: nearer to the head. * Inferior: nearer to the feet. * Anterior (ventral): nearer to the front. * Posterior (dorsal): nearer to the back. * Medial: nearer to the median plane. * Lateral: farther away from median plane. * Middle: means exactly midway between two fixed points. * Proximal: nearer to trunk or point of origin. * Distal: farther away from trunk or point of origin. * Internal: nearer to the cavity of the organ (hollow organ). * External: away from the cavity of the organ (hollow organ). ## Terms of Position * **Erect anatomical position** The body is standing upright; eyes are looking horizontally forwards, upper limbs are stretched by the side of the trunk, palms are facing forwards, lower limbs parallel and feet are directed forwards. * **Supine position:** the body lies on its back. * **Prone position:** the body lies on its face ## Anatomical Planes and Lines * **Coronal plane:** it is a vertical plane which divides the body into anterior (ventral) part and posterior (dorsal). * **Horizontal plane:** it is a transverse plane which divides the body into upper (superior) and lower (inferior) parts. * **Sagittal plane:** it is a vertical plane which divides the body into right and left halves. # Structure of the Body ## The Cell The cell is the structural and functional unit of the body. The cells of the body are grouped to form: 1. Tissues: made of fixed cells connected together 2. Cells of the body fluids: like blood and lymph cells. ## The Tissue Tissue is made of a large number of fixed cells having the same function. Four basic tissues are recognized in the body: 1. The epithelial tissue. 2. The connective tissue. 3. The muscular tissue. 4. The nervous tissue. ## An Organ Is formed by groups of tissues which unite in a special way and perform a specific function. ## A System Is formed of a group of organs associated together to form a functional unit. The human body is formed of many systems. Each system is formed of some organs (e.g. heart, arteries and veins form CVS) # Connective Tissue Connective tissue includes: 1. The sheets of fascia. 2. Cartilage. 3. Bones. # Fasciae of the Body The term fascia is applied to the membrane-like sheets of fibroareolar connective tissue which covers or binds; the tissues or organs. It is either external or internal. ## Types of External Fascia ### I-Superficial fascia It is subcutaneous connective tissue, made of loose elastic fibers and variable amount of fat. #### Functions 1. It allows considerable movement of the skin over the under laying structures. 2. Transmits the nerves and blood vessels and lymphatic to and from the skin. 3. It is the main site for fat storage * Heat insulator * Fat gives the body its rounded contours N.B. Amount of fat is more in: females, young aged persons and especial sites as in breast Fat is absent in eye lids, scrotum and penis. 4. It makes the body soft. 5. Contains muscles: e.g. muscles of expression in the face and dartos muscle in scrotum. 6. Contains many glands: mammary gland and sweat glands. ## II. Deep Fascia * It is thick, dense, tense, inelastic, strong membrane of connective tissue. * It is formed by regularly arranged collagenous fibers. * It covers the whole body except in certain regions as in the face and in the anterior abdominal wall where it is absent. #### Functions Deep Fascia 1. It keeps the underlying structures in its position. 2. It forms intermuscular septum: partition between different muscle groups. 3. It forms the interosseous membrane of the forearm and leg which fixes the bones together 4. It forms a thick transverse band called retinaculum at wrist and ankle joints to retain the muscle tendons in their positions. 5. It forms aponeurosis in the palm and sole of the foot for protection of deeper structures. 6. It forms sheaths for blood vessels and nerves e.g. carotid sheath. 7. It gives capsular covering for the glands e.g. thyroid 8. It helps venous and lymphatic return by contraction of muscle against the strong deep fascia. ## Internal Fascia * **Parietal layer:** lining the body cavities (thoracic and abdominal). * **Visceral layer:** covers the organs and condensed to form ligaments that support these organs # Bones (The Skeletal System) . Bones - a living tissue- is highly specialized, hard form of connective tissue. Bone forms with cartilage the skeletal tissue of the body ## Functions of the Bones 1. It gives the form of the body. 2. It transmits weight to the ground. 3. It protects the vital structures e.g. skull protects the brain. 4. It forms the joints which is the mechanical basis for movement. 5. Muscular attachments 6. Stores calcium and phosphorus 7. New blood cells from bone marrow ## Types of the Bones ### I. According to the type of ossification 1. **Membranous ossification** in which the bones are formed from membranous mesenchymal tissue e.g. clavicle, skull cap and some facial bones. 2. **Cartilaginous ossification** in which the mesenchymal tissue forms cartilaginous module (transformed into cartilage). Later on the cartilage is replaced by bones. ### II. According to the histological structure 1. **Compact bone:** is dense in texture near the surface of bones e.g. cortex of long bone.. 2. **Spongy bone:** is formed of network of bone trabeculae with spaces in between containing the bone marrow. ### III. According to the position in the body 1. **Axial bones:** forms the axis of the body and include the skull, vertebral column and thoracic cage (ribs and sternum). 2. **Appendicular bones:** bones of the upper and lower limbs. ### IV. According the shape of the bones 1. **Tubular bones:** consists of cylindrical body (shaft) and two expanded ends #### Two types of tubular bones are recognized: * **Long tubular:** (for example humerus – femur) * The upper and lower epiphyses: are expanded ends of the bone and are formed of a mass of spongy bone covered by a thin layer of compact bone. It has a smooth articular surface that is covered by the hyaline articular cartilage. They are shared in the formation of the joints. * The shaft is also called a "diaphysis": it is formed by a tube of compact bone covered by the periosteum and it contains a central medullary cavity filled by the bone marrow. The endosteum: It is a vasculocellular layer lining the medullary canals. * The metaphyses: are the expanded parts of the bone next to diaphysis. Metaphyses are the most active parts during bone growth. They have no medullary canal. * **Epiphyseal plate of hyaline cartilage** lies between the epiphyses and metaphyses in the growing bone and is responsible for growth of bone in length. It ossifies about 18 to 21 years old * **Short tubular:** they look like long tubular bones but shorter having the same appearance. They have no medullary cavity and a single epiphysis plate. For example metacarpals and phalanges in hand. 2. **Short bones:** they are small-sized, have no shaft. They consist of mass of spongy bone covered by thin bone cortex (compact). For example carpals in hand 3. **Flat bones:** consist of inner and outer tables of compact bone with spongy bone in between containing red bone marrow. * **Functions:** * provide protection to internal organs e.g. skull cap, * provide a wide surface area for muscle attachment e.g. scapula 4. **Irregular bones:** they have no special form. They have multiple processes. They have the same construction as the short bones e.g. vertebrae. 5. **Pneumatic bones:** * **Structure:** the bones of skull around the nose is filled by a cavity containing air and is lined by mucous membrane to form the paranasal air sinuses * Example: maxillary and frontal bones * **Functions:** * lighten the weight of the skull, * give resonance to voice, * worming and humidification of air. 6. **Sesamoid bones:** * they are small bones embedded in the tendon of certain muscles, * **Functions:** * Reduce friction between the tendon and under laying bone, thus protect the tendons from excessive wear: * Example: Patella in the tendon of quadriceps femoris ## The Blood Supply of the Bone of Long Bone 1. **Periosteal vessels:** they are numerous and derived from the muscular arteries. They supply the outer 2/3 of the thickness of the diaphysis. Periosteal vessels are important for healing process. 2. **Nutrient artery:** it passes through the nutrient foramen which is usually about the middle of the shaft. As the artery reaches the medullary cavity it divides into upper and lower branches to both ends of the bone. They supply the inner 1/3 of the thickness of the bone. * The direction of the nutrient artery (and foramen) is the opposite of that of growing ends of the long bones of the limbs. 3. **Epiphyseal arteries:** they are directed to the epiphysis. 4. **Metaphyseal arteries:** * Metaphyseal arteries: from the muscular arteries. They, they are not anastomose with the epiphyseal arteries except after fusion of the epiphysis with the diaphysis after the ossification of the epiphyseal plate of cartilage ## Growth of the Bones Growth of bones includes increase in length and width 1. **Growth in length:** * Before birth most of the long bones have primary ossification centers at the middle of the shaft with the ends not ossified forming the cartilaginous epiphyses * **Secondary ossification centers** * They appear at different ages in the different bones. Each long bone has at least one secondary center for each end. * The long bone grow from either of its ends by the activity of the epiphyseal plate of cartilage , until the epiphysis unites with the rest of the shaft of the bone * **Growing end of a long bone:** the epiphyseal center of one end of the bone usually appears earlier than that of the other end and commonly unites later forming growing end. The epiphysis of the less growing end fuses earlier with the shaft. 2. **Growth in thickness:** it is due to the deposition of bones on the surface of the shaft from the periosteum. * **Growing ends of the long bones:** * In the upper limbs, the growing ends are the upper end of the humerus and the lower ends of the radius and ulna. Epiphyses around the elbow unit with the shaft at about the age of 16-18 years while those away from the elbow at 18-20 years. * In the lower limb, the growing ends are the lower end of the femur and the upper ends of the tibia and fibula. Epiphyses around the knee unite with the shaft at about the age of 18-20 years while those away from knee at 16-18 years. * The nutrient arteries and foramina are directed away from the growing ends "to the elbow I go, from the knee I flee". # Joints (Articulations) **Definition:** Joint is a site of meeting or articulation of two or more bones. **Classification of joints** according to their structure and mobility into three types ## 1. Fibrous Joints The bony surfaces are joined by a fibrous tissue. They have a minimal and limited degree of movement. **Types** * **Sutures:** are only seen in the skull bones. The bones are connected by suture ligament. Sutures may close with age. * **Gomphosis:** Each tooth root is fixed in a socket with a periodontal membrane * **Syndesmosis:** the bony surfaces are connected by a strong membrane “interossous ligament” eg. inferior tibiofibular joint. ## 2. Cartilaginous Joints The bony surfaces are joined by cartilage. **Types** * **Primary cartilaginous joint:** it is temporary and ossifies later in life. It is formed of a plate of hyaline cartilage between the articulated bones. It is immobile. * e.g. epiphyseal cartilage between epiphyses and diaphysis of growing long bone. * **Secondary cartilaginous joint:** it is permenant and nerve ossify by age. Tthe articulating bones are separated by a disc of white fibrocartilage. It is slightly mobile. * e.g. intervertebral disc of vertebral column. ## 3. Synovial Joints Freely movable joints and **Particular features:** * **Articular surfaces:** smooth and covered by hyaline cartilage. * **Fibrous capsule:** it is a fibrous tube surrounding the joint. It is attached around the articulating bones together. It is perforated by vessels and nerves. * **Ligaments:** They are fibrous bands normally are taught, may be: * Intrinsic ligaments: they are thickening of the fibrous capsule. * Extrinsic ligaments: they are outside the capsule. * **Synovial membrane:** it is a thin,moist and glistening membrane that lines the fibrous capsule and covers all intra-capsular structures except the articular surfaces. * **Function:** * It secretes and reabsorbs the synovial fluid. * **Synovial fluid:** Pale yellow viscid fluid. * **Functions:** * Lubrication of the articular surfaces so facilitate the movement, * Gives nourishment for cartilage. * **Intra-articular structure** * Especial structure is found in some joints for certain functions e.g * Disc of cartilage e.g. tempromandibular joint. * Tendons e.g. biceps brachii in the shoulder joint. * Ligaments e.g. cruciate ligaments in the knee joint. * Semilunar cartilage (Meniscus ) e.g. knee joint. ## Types of the Synovial Joints **A. According to the number of the articulating bones:** 1. **Simple** consists of two bones surrounded by one articular capsule e.g. shoulder joint. 2. **Compound** consists of more than two articulating bones surrounded by one articular capsule e.g. elbow joint. 3. **Complex** has intra-capsular structures e.g. knee joint. **B. According to the shape of the articular surfaces and axis of movement:** * **Uniaxial joints:** movements take place around single axis * **Hinge:** uniaxial - axis is horizontal - trochlea like articulating surface. It permits flexion and extension e.g. elbow joint * **Pivot:** uniaxial - the axis is longitudinal. The articulating bones consists of central bony pivot surrounded by a fibro-osseus ring e.g. superior radio-ulnar joint * **Biaxial joints:** movements take place around two axes perpendicular to each other: * **Ellipsoid:** biaxial in which an oval convex surface moves on a similar oval concave opposite surface. It permits flexion, extension, adduction and abduction e.g. wrist joint. * **Condyloid:** biaxial, the articulating surfaces consist of two convex condyles which articulate with two concave surfaces e.g. knee joint. * **Saddle:** concavoconvex biaxial joint in which one concavo-convex surface fitting into another surface reciprocally curved but at right angles e.g. carpometacarpal joint of the thumb. It permits flexion, extension, adduction, abduction and little ranges of rotational movements. * **Multiaxial joints:** occur around more than 2 axes * **Ball and socket:** multiaxial joint. The articulating bones move around an indefinite number of axes. The articulating surfaces consist of a round head and a cup- shaped concave surface e.g. shoulder and hip joints. * **Plane joint (non axial):** the surfaces are flat and only permit gliding movement e.g. Intercarpal joints ## Factors Affecting Stability of the Joints 1. The shape of the articulating surfaces and their fitting together. 2. The strength and thickness of the fibrous capsule and ligaments. 3. The muscles: give support and their contractions keep the articular surfaces in firm contact.. ## Factors Which Terminate the Movement at a Joint 1. Bony factors: presence of many processes around the joint e.g. elbow joint, helps the early limitation of the movement. 2. Tension on the ligament. 3. Approximation of the soft tissue of the part. ## Nerve Supply: According Hilton's law: the nerve which supplies muscle acting on a joint must give a branch to supply this joint and a branch to the skin covering the joint. ## Terms of Movement * **Flexion:** (bending) approximates anterior surfaces to each other * **Extension:** (straightening) approximates posterior surfaces to each other * **Adduction:** moving the limb towards the trunk * **Abduction:** moving the limb away from the trunk or median plane * **Medial rotation:** the limb rotates medially around its long axis * **Lateral rotation:** the limb rotates laterally around its long axis * **Circumduction:** is a series of flexion, abduction, extension and adduction movements which follow one another in succession * **Pronation and supination of forearm** * **Inversion and eversion of foot** # Muscles Muscles form half the weight of the body. The muscular tissue has the property of contraction. ## Types 1. Skeletal. 2. Smooth. 3. Cardiac muscle. ## Comparisons Between Different Types of Muscles | Type | Location | Nerve supply | |---|---|---| | Striated | Attached to skeleton, | Voluntary somatic nervous system | | Cardiac | Muscle of the heart, | Involuntary, autonomic nervous system | | Smooth | *Walls of hollow organs, & blood vessels | Involuntary, autonomic nervous system | ## Attachments of the Muscle The muscle has at least two attachments, one is less mobile and more proximal is called origin. The other is relatively mobile and more distal and is called insertion.. ## Site of Attachments 1. Bone 2. Skin to the dermis (e.g. muscle of expressions in the face) 3. Cartilage (muscles of larynx) 4. Raphe: fibrous band connects two flat with each other ## Attachments of Muscle are Through 1. Its fleshy fibers 2. Tendons which are rounded cord like or band like. 3. Aponeurosis means flat tendon ## Pattern of Arrangement of the Muscle Fibers Muscle fibers are arranged according to the line of pull (line extends from the origin to the insertion of the muscle): ### Muscles with fibers parallel to the line of pull: 1. Long strap- like muscle e.g. Sartorius muscle 2. Quadrangular muscles e.g. pronator quadratus muscle 3. Fusiform e.g. lumbrical muscle. ### Muscles with fibers oblique to the line of pull. #### A. Muscles with fibers obliquely arranged in relation to the line of pull with pennate formation: 1. Unipennate muscle: the fibers lie on one side of the tendon like a half a feather. 2. Bipennate muscle: the fibers converge on both sides of the tendon like a full feather. 3. Multipennate muscle: several bipennate muscles are united together by intermuscular septa and tendon converging at one insertion. 4. Circumpennate muscle: the fibres converge on central tendon which lies within the muscle, encircling it. #### B. Muscles with fibers oblique to the line of pull but are not pennate. 1. Triangular: temporalis muscle. 2. Spiral: spinator muscle. 3. Cruciate: masseter muscle. 4. Circular: orbicularis oris ## NB.. Muscles with more than one fleshy belly 1. Biceps has two heads. 2. Triceps has three heads. 3. Quadriceps has four heads. ## Nerve and Blood Supply of the Muscle Nerve and blood supply of the muscles are termed the neuro-vascular bundle. This bundle enters at the hilum. The muscle is supplied by three nerves: 1. Motor nerve 2. Sensory nerve 3. Sympathetic fibers o the blood vessels. ## Muscle Action and Power * The range of movements of the muscle depends on the length of the muscle fibers i.e. the longer the muscle fibers is the wider range of movement. * The force of contraction of the muscle depends on the number of muscle fibers i.e. greater number of muscle fibers the greater the force of contraction. Muscles can act from either its origin or insertion according to the movement needed. ## Types of Action 1. **Prime movers:** they are the main, but not the only, muscle doing a certain action. They are responsible for initiation and maintenance of a particular movement. 2. **Antagonists:** they are the muscles that oppose the prim mover. 3. **Fixators:** they fix the bone(s) of origin of the prime movers to allow the prime mover to work efficiently. 4. **Synergists (helper):** by eliminating the unwanted movements.