Introduction to Human Anatomy PDF

Body structure, organization and functions Emebet C. (MSc. In clinical Anatomy) Introduction to Gross Anatomy Anatomy Definition - anatome = up (ana) + cutting (tome)  The art of separeting the parts of an organism in order to ascertain their position, re...

Body structure, organization and functions Emebet C. (MSc. In clinical Anatomy) Introduction to Gross Anatomy Anatomy Definition - anatome = up (ana) + cutting (tome)  The art of separeting the parts of an organism in order to ascertain their position, relations & structures. Brief History  Is one of the old Biomedical sciences.  It was first formally studied in Egypt - around 500 B.C.  Earliest descriptions of human anatomy were written on papyruses- B/n 3000 and 2500 B.C  Was taught in Greek by Hippocrates (460 - 377 B.C.E.)  Aristotle (384-322 BC) was the first person to use the word “anatome.”  During renaissance artists & anatomists like Leonardo davinci, Michelangelo, and Vesalius (1514-1564) began to accurately display and describe the parts of the human body  In 1543 the first comprehensive human anatomy book on the structure of human body was published by Andreas Vesalius  In the 19th century anatomy started to be divided into its different parts; Disciplines of Anatomy  Gross Anatomy: structures studied with the naked eye.  Systematic anatomy: organized by systems, e.g., digestive, nervous, endocrine, etc.  Regional anatomy: study of all structures in an area of the body, e.g., upper extremity bones, muscles, blood vessels, etc.  Microscopic anatomy  Cytology – internal structures of cells  Histology – study of tissues (groups of cells)  Developmental anatomy (embryology)  Pathological anatomy  Radiologic anatomy (x-ray, CT, MRI)  Other areas? (surgery) Approach To Studying Anatomy  The three main approaches to studying anatomy are regional, systemic, and clinical (or applied) 1. Regional Anatomy  Regional anatomy (topographical anatomy) considers the organization of the human body as major parts or segments  A main body, consisting of the head, neck, and trunk (subdivided into thorax, abdomen, back, and pelvis/perineum), and paired upper limbs and lower limbs.  Surface anatomy is an essential part of the study of regional anatomy.  It provides knowledge of what lies under the skin and what structures are perceptible to touch (palpable) in the living body at rest and in action. FIGURE 1. Major parts of the body and regions of the lower limb. Anatomy is described relative to the anatomical position illustrated here. Approach To Studying Anatomy 2. Systemic Anatomy  is the study of the body’s organ systems that work together to carry out complex functions.  The body is divided into 11 body systems. a) The integumentary system (dermatology) consists of the skin and its appendages— hairs, nails, and sweat glands, for example—and the subcutaneous tissue just beneath it. b) The skeletal system (osteology) consists of bones and cartilage; it provides our basic shape and support for the body and is what the muscular system acts on to produce movement. It also protects vital organs such as the heart, lungs, and pelvic organs. c) The articular system (arthrology) consists of joints and their associated ligaments, connecting the bony parts of the skeletal system and providing the sites at which movements occur Approach To Studying Anatomy d) The muscular system (myology) consists of skeletal muscles that act (contract) to move or position parts of the body (e.g., the bones that articulate at joints), or smooth and cardiac muscle that propels, expels, or controls the flow of fluids and contained substance. e) The nervous system (neurology) consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves and ganglia, together with their motor and sensory endings). The nervous system controls and coordinates the functions of the organ systems, enabling the body’s responses to and activities within its environment. The sense organs, including the olfactory organ (sense of smell), eye or visual system (ophthalmology), ear (sense of hearing and balance—otology), and gustatory organ (sense of taste), are often considered with the nervous system in systemic anatomy. Approach To Studying Anatomy f) The circulatory system (angiology) consists of the cardio vascular and lymphatic systems, which function in parallel to transport the body’s fluids.  The cardiovascular system (cardiology) consists of the heart and blood vessels that propel and conduct blood through the body, delivering oxygen, nutrients, and hormones to cells and removing their waste products.  The lymphatic system is a network of lymphatic vessels that withdraws excess tissue fluid (lymph) from the body’s interstitial (intercellular) fluid compartment, filters it through lymph nodes, and returns it to the bloodstream. Approach To Studying Anatomy g) The alimentary or digestive system (gastroenterology) consists of the digestive tract from the mouth to the anus, with all its associated organs and glands that function in ingestion, mastication (chewing), deglutition (swallowing), digestion, and absorption of food and the elimination of the solid waste (feces) remaining after the nutrients have been absorbed. h) The respiratory system (pulmonology) consists of the air passages and lungs that supply oxygen to the blood for cellular respiration and eliminate carbon dioxide from it. The diaphragm and larynx control the flow of air through the system, which may also produce tone in the larynx that is further modified by the tongue, teeth, and lips into speech. Approach To Studying Anatomy i) 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 (liquid waste). j) The genital (reproductive) system (gynecology for females; andrology for males) consists of the gonads (ovaries and testes) that produce oocytes (eggs) and sperms, the ducts that transport them, and the genitalia that enable their union. After conception, the female reproductive tract nourishes and delivers the fetus. k) The endocrine system (endocrinology) consists of specialized structures that secrete hormones, including discrete ductless endocrine glands (such as the thyroid gland), isolated and clustered cells of the gut and blood vessel walls, and specialized nerve endings. Approach To Studying Anatomy 3) Clinical anatomy (applied anatomy)  emphasizes aspects of bodily structure and function important in the practice of medicine, dentistry, and the allied health sciences. It incorporates the regional and systemic approaches to studying anatomy and stresses clinical application. Anatomical Terminology  Anatomical terminology introduces and makes up a large part of medical terminology.  Although you are familiar with common, colloquial terms for parts and regions of the body, you must learn the international anatomical terminology (e.g., axillary fossa instead of armpit and clavicle instead of collarbone)  That enables precise communication among healthcare professionals and scientists worldwide.  Without anatomic terms, one cannot accurately discuss or record the abnormal functions of joints, the actions of muscles, the alteration of position of organs, or the exact location of swellings or tumors. Cont’d… 1. Anatomical Position The anatomical position refers to the body position as if the person were standing upright with the: head, gaze (eyes), and toes directed anteriorly (forward), arms adjacent to the sides with the palms facing anteriorly, and lower limbs close together with the feet parallel. Cont’d… 2. Anatomical Planes Anatomical descriptions are based on four imaginary planes (median, sagittal, frontal, and transverse) that intersect the body in the anatomical position.  The median plane (median sagittal plane), the vertical plane passing longitudinally through the body, divides the body into right and left halves.  Sagittal planes are vertical planes passing through the body parallel to the median plane.  Frontal (coronal) planes are vertical planes passing through the body at right angles to the median plane, dividing the body into anterior (front) and posterior (back) parts.  Transverse planes are horizontal planes passing through the body at right angles to the median and frontal planes, dividing the body into superior (upper) and inferior (lower) parts. FIGURE 2. Anatomical planes. The main planes of the body are illustrated. Cont’d… The main use of anatomical planes is to describe sections.  Longitudinal sections run lengthwise or parallel to the long axis of the body or of any of its parts, and the term applies regardless of the position of the body.  Transverse sections, or cross sections, are slices of the body or its parts that are cut at right angles to the longitudinal axis of the body or of any of its parts.  Oblique sections are slices of the body or any of its parts that are not cut along the previously listed anatomical planes. In practice, many radiographic images and anatomical sections do not lie precisely in sagittal, frontal, or transverse planes; often they are slightly oblique. FIGURE 3. Sections of the limbs. Sections may be obtained by anatomical sectioning or medical imaging techniques. Cont’d… 3. Terms of Relationship and Comparison  Superior refers to a structure that is nearer the vertex  Vertex the topmost point of the cranium  Cranial toward the head or cranium.  Inferior refers to a structure that is situated nearer the sole of the foot.  Caudal is a useful directional term that means toward the feet or tail region  Posterior (dorsal) behind, in back, or in the rear  Anterior (ventral) denotes the front surface of the body.  Rostral is often used instead of anterior when describing parts of the brain; it means toward the rostrum (L. for beak); however, in humans it denotes nearer the anterior part of the head (e.g., the frontal lobe of the brain is rostral to the cerebellum). Cont’d…  Medial is used to indicate that a structure is nearer to the median plane of the body.  Lateral stipulates that a structure is farther away from the median plane.  Dorsum usually refers to the superior aspect of any part that protrudes anteriorly from the body, such as the dorsum of the tongue, nose, penis, or foot.  Dorsal surface the surface of the hands, the feet, and the digits corresponding to the dorsum.  Palmar surface the surface of the hand and fingers corresponding to the palm  Plantar surface the surface of the foot and toes corresponding to the sole Cont’d…  Combined terms describe intermediate positional arrangements:  inferomedial means nearer to the feet and median plane  superolateral means nearer to the head and farther from the median plane.  Other terms of relationship relating primarily to the body’s surface or its central core:  Superficial nearer to surface  Intermediate between a superficial and a deep structure  Deep farther from surface Cont’d… 4. Terms of laterality  BilateralPaired structures having right and leftmembers (e.g., the kidneys)  Unilateral those occurring on one side only (e.g., the spleen)  Ipsilateral Something occurring on the same side of the body as another structure (for example, the right thumb and right great (big) toe are ipsilateral).  Contralateral means occurring on the opposite side of the body relative to another structure; the right hand is contralateral to the left hand. FIGURE 4. Terms of relationship and comparison. These terms describe the position of one structure relative to another. Cont’d… 5. Terms Of Movement A site where two or more bones come together is known as a joint. Some joints have no movement (sutures of the skull), some have only slight movement (superior tibiofibular joint), and some are freely movable (shoulder joint).  Flexion indicates bending or decreasing the angle between the bones or parts of the body. For most joints (e.g., elbow), flexion involves movement in an anterior direction.  Extension indicates straightening or increasing the angle between the bones or parts of the body.  Dorsiflexion describes flexion at the ankle joint, as occurs when walking uphill or lifting the front of the foot and toes off the ground.  Plantarflexion bends the foot and toes toward the ground, as when standing on your toes. Cont’d…  Hyperextension Extension of a limb or part beyond the normal limit (overextension)  Abduction means moving away from the median plane (e.g., when moving an upper limb laterally away from the side of the body)  Adduction is a movement of a limb toward the body  Circumduction is a circular movement that involves sequential flexion, abduction, extension, and adduction (or in the opposite order) in such a way that the distal end of the Cont’d…  Rotation involves turning or revolving a part of the body around its longitudinal axis, such as turning one’s head to face sideways  Medial rotation (internal rotation) brings the anterior surface of a limb closer to the median plane  lateral rotation (external rotation) takes the anterior surface away from the median plane.  Pronation and supination are the rotational movements of the forearm and hand that swing the distal end of the radius (the lateral long bone of the forearm) medially and laterally around and across the anterior aspect of the ulna (the other long bone of the forearm)  Pronation rotates the radius medially so that the palm of the hand faces posteriorly and its dorsum faces anteriorly.  Supination is the opposite rotational movement, rotating the radius laterally and uncrossing it from the ulna, returning the pronated forearm to the anatomical position. Cont’d…  Eversion moves the sole of the foot away from the median plane, turning the sole laterally.  Inversion moves the sole of the foot toward the median plane (facing the sole medially).  Protrusion is a movement anteriorly (forward) as in protruding the mandible (chin), lips, or tongue.  Retrusion is a movement posteriorly (backward), as in retruding the mandible, lips, or tongue.  Elevation raises or moves a part superiorly, as in elevating the shoulders when shrugging, the upper eyelid when opening the eye, or the tongue when pushing it up against the palate (roof of mouth).  Depression lowers or moves a part inferiorly, as in depressing the shoulders when standing at ease, the upper eyelid when closing the eye, or pulling the tongue away from the palate. FIGURE 5. Terms of movement. These terms describe movements of the limbs and other parts of the body; most movements take place at joints, where two or more bones or cartilages articulate with one another. Anatomical Variations  Anatomy books describe (initially, at least) the structure of the body as it is in the most common pattern.  However, occasionally a particular structure demonstrates so much variation within the normal range that the most common pattern is found less than half the time  Often students ignore the variations or inadvertently damage them by attempting to produce conformity.  Therefore, you should expect anatomical variations when you dissect or inspect prosected specimens. Fascias, Facial compartment, Bursae and Potential spaces (body cavities) Fascias  Constitute the wrapping, packing, and insulating materials of the deep structures of the body.  Lie between the skin and the underlying muscles and bones.  The fasciae of the body can be divided into two types— superficial and deep 1. The superficial fascia (subcutaneous tissue)  is a mixture of loose areolar and adipose tissue  Unites the dermis of the skin to the underlying deep fascia  In the scalp, the back of the neck, the palms of the hands, and the soles of the feet, it contains numerous bundles of collagen fibers  In the eyelids, auricle of the ear, penis and scrotum, and clitoris, it is devoid of adipose tissue Cont’d… 2. The deep fascia  is a dense, organized connective tissue layer, devoid of fat  Covers most of the body deep to the skin and subcutaneous tissue  Extensions from its internal surface invest deeper structures, such as individual muscles and neurovascular bundles, as investing fascia  Its thickness varies widely. For example, in the face, distinct layers of deep fascia are absent  In the limbs, groups of muscles with similar functions sharing the same nerve supply are located in fascial compartments  This muscles are separated by thick sheets of deep fascia, called intermuscular septa FIGURE 7. Excavated section of the leg demonstrating the deep fascia and fascial formations The deep fascia  The fascial compartments may contain or direct the spread of an infection or a tumor  Near certain joints (e.g., wrist and ankle), the deep fascia becomes markedly thickened, forming a retinaculum  That limits the outward expansion of the bellies of contracting skeletal muscles  preventing them from taking a shortcut, or bow stringing, across the angle created FIGURE 8. Extensor retinaculum on the posterior surface of the wrist holding the underlying tendons of the extensor muscles in position. Subserous fascia lies between the internal surfaces of the musculoskeletal walls and the serous membranes lining the body cavities. These are the endothoracic, endoabdominal, and endopelvic fascias; The latter two may be referred to collectively as extraperitoneal fascia. Bursae  are closed sacs or envelopes of serous membrane (a delicate connective tissue membrane capable of secreting fluid to lubricate a smooth internal surface).  Bursae are normally collapsed.  Unlike realized spaces, these potential spaces have no depth  Their walls are apposed with only a thin film of lubricating fluid between them  When the wall is interrupted at any point, or when a fluid is secreted or formed within them in excess, they become realized spaces Bursae  Bursae enable one structure to move more freely over another  Subcutaneous bursae occur in the subcutaneous tissue between the skin and bony prominences, such as at the elbow or knee  Subfascial bursae lie beneath deep fascia; and  subtendinous bursae facilitate the movement of tendons over bone.  Synovial tendon sheaths are a specialized type of elongated bursae that wrap around tendons  Collapsed bursal sacs surround many important organs (e.g., the heart, lungs, and abdominal viscera) and structures (e.g., portions of tendons). Cont’d…  This configuration is much like wrapping a large but empty balloon around a structure, such as a fist  The object is surrounded by the two layers of the empty balloon but is not inside the balloon  The balloon itself remains empty. For an even more exact comparison, the balloon should first be filled with water and then emptied, leaving the empty balloon wet inside  In exactly this way,  The pericardial sac surround the heart  The pleural sac surround each lung, and  The peritoneal sac surround the abdominal viscera  The inner layer of the balloon or serous sac (the one adjacent to the fist, viscus, or viscera) is called the visceral layer;  the outer layer of the balloon (or the one in contact with the body wall) is called the parietal layer Body Cavities FIGURE 9. bursal sacs. Bursal sacs enclose several structures, such as the heart, lungs, abdominal viscera, and tendons, much like this collapsed balloon encloses the fi st. Review of body system Skeletal system The skeletal system may be divided into two functional parts 1. The axial skeleton consists of the bones of the head (cranium or skull), neck (hyoid bone and cervical vertebrae), and trunk (ribs, sternum, and vertebrae). 2. The appendicular skeleton consists of the bones of the limbs, including those forming the pectoral (shoulder) and pelvic girdles. Cartilage and Bones  The skeleton is composed of cartilages and bones  Cartilage  is a resilient, semirigid form of connective tissue that forms parts of the skeleton where more flexibility is required  example, where the costal cartilages attach the ribs to the sternum  Blood vessels do not enter cartilage (i.e., it is avascular)  The younger a person is, the more cartilage he or she has. Cartilage  There are three types of cartilage: 1. Hyaline cartilage has a high proportion of amorphous matrix and covers the articular surfaces of nearly all synovial joints. Hyaline cartilage is incapable of repair when fractured; the defect is filled with fibrous tissue. 2. Fibrocartilage has many collagen fibers embedded in a small amount of matrix and is found in the discs within joints. 3. Elastic cartilage possesses large numbers of elastic fibers embedded in matrix. As would be expected, it is flexible and is found in the auricle of the ear, the external auditory meatus, the auditory tube, and the epiglottis. Cartilage and Bones  Bone  is living tissue, a highly specialized, hard form of connective tissue that makes up most of the skeleton. Bones of the adult skeleton provide:  support for the body and its vital cavities; it is the chief supporting tissue of the body.  protection for vital structures (e.g., the heart).  the mechanical basis for movement (leverage).  storage for salts (e.g., calcium).  A continuous supply of new blood cells Cont’d..  Periosteum afibrous connective tissue covering surrounds each bone like a sleeve, except where articular cartilage occurs  Whereas that around cartilage is perichondrium  The periosteum and perichondrium nourish the external aspects of the skeletal tissue  They are capable of laying down more cartilage or bone, particularly during fracture healing  And provide the interface for attachment of tendons and ligaments  There are two types of bone; 1. compact bone 2. spongy (trabecular) bone Cont’d…  All bones have a superficial thin layer of compact bone around a central mass of spongy bone  Except where the latter is replaced by a medullary (marrow) cavity  Within the medullary cavity of adult bones, and between the spicules (trabeculae) of spongy bone, yellow (fatty) or red (blood cell and platelet forming) bone marrow—or a combination of both—is found  Compact bone provides strength for weight bearing  The amount of compact bone is greatest near the middle of the shaft where the bones are liable to buckle Classification Of Bones  Bones are classified according to their shape. Long bones are tubular (e.g., the humerus in the arm). Short bones are cuboidal and are found only in the tarsus (ankle) and carpus (wrist). Flat bones usually serve protective functions (e.g., the flat bones of the cranium protect the brain). Irregular bones have various shapes other than long, short, or fl at (e.g., bones of the face). Sesamoid bones (e.g., the patella or knee cap) develop in certain tendons and are found where tendons cross the ends of long bones in the limbs; they protect the tendons from excessive wear and often change the angle of the tendons as they pass to their attachments. Bone markings and formations  Bone markings appear wherever tendons, ligaments, and fascias are attached or where arteries lie adjacent to or enter bones  Some of the various markings and features of bones are: Capitulum: small, round, articular head (e.g., capitulum of the humerus). Condyle: rounded, knuckle-like articular area, often occurring in pairs (e.g., the lateral and medial femoral condyles). Crest: ridge of bone (e.g., the iliac crest). Epicondyle: eminence superior or adjacent to a condyle (e.g., lateral epicondyle of the humerus). Facet: smooth fl at area, usually covered with Bone markings and formations Foramen: passage through a bone (e.g., obturator foramen). Fossa: hollow or depressed area (e.g., infraspinous fossa of the scapula). Groove: elongated depression or furrow (e.g., radial groove of the humerus). Head (L. caput): large, round articular end (e.g., head of the humerus). Line: linear elevation (e.g., soleal line of the tibia). Malleolus: rounded process (e.g., lateral malleolus of the fibula). Notch: indentation at the edge of a bone (e.g., greater sciatic notch). Bone markings and formations Protuberance: projection of bone (e.g., external occipital protuberance). Spine: thorn-like process (e.g., the spine of the scapula). Spinous process: projecting spine-like part (e.g., spinous process of a vertebra). Trochanter: large blunt elevation (e.g., greater tro chanter of the femur). Trochlea: spool-like articular process or process that acts as a pulley (e.g., trochlea of the humerus). Tubercle: small raised eminence (e.g., greater tubercle of the humerus). Tuberosity: large rounded elevation (e.g., ischial tuberosity). FIGURE 12. Bone markings and formations. Markings appear on bones wherever tendons, ligaments, and fascia attach. Other formations relate to joints, Bone Development  Most bones take many years to grow and mature.  ossification is not complete until age 20.  All bones derive from mesenchyme (embryonic connective tissue) by two different processes: intramembranous ossification (directly from mesenchyme) and endochondral ossification (from cartilage derived from mesenchyme) In intramembranous ossification (membranous bone formation), mesenchymal models of bones form during the embryonic period, and direct ossification of the mesenchyme begins in the fetal period. In endochondral ossification (cartilaginous bone formation), cartilage models of the bones form from mesenchyme during the fetal period, and bone subsequently replaces most of the cartilage. FIGURE 13. Development and growth of a long bone. A. The formation of primary and secondary ossification centers is shown. B. Growth in length occurs on both sides of the cartilaginous epiphysial plates (doubleheaded Vasculature and Innervation of Bones  Bones are richly supplied with blood vessels.  Most apparent are the nutrient arteries (one or more per bone)  The nutrient artery divides in the medullary cavity into longitudinal branches that proceed toward each end, supplying the bone marrow, spongy bone, and deeper portions of the compact bone  Small branches from the periosteal arteries of the periosteum are responsible for nourishment of most of the compact bone  Blood reaches the osteocytes (bone cells) in the compact bone by means of haversian systems or osteons (microscopic canal systems) that house small blood vessels  The ends of the bones are supplied by metaphysial and epiphysial arteries that arise mainly from the arteries that supply the joints Vasculature and Innervation of Bones Veins accompany arteries through the nutrient foramina. Lymphatic vessels are also abundant in the periosteum. Nerves accompany blood vessels supplying bones. The periosteum is richly supplied with sensory nerves periosteal nerves that carry pain fibers. The periosteum is especially sensitive to tearing or tension Bone itself is relatively sparsely supplied with FIGURE 14. Vasculature and innervation of a long bone. Clinical correlations Accessory (Supernumerary) Bones  Accessory (supernumerary) bones develop when additional ossification centers appear and form extra bones.  It is important to know that accessory bones are common in the foot  To avoid mistaking them for bone fragments in radiographs and other medical images. Clinical correlations Heterotopic Bones  Bones sometimes form in soft tissues where they are not normally present (e.g., in scars).  Horse riders often develop heterotopic bones in their thighs (rider’s bones),  Probably because of chronic muscle strain resulting in small hemorrhagic (bloody) areas that undergo calcification and eventual ossification. Clinical correlations Osteoporosis  During the aging process, the organic and inorganic components of bone both decrease,  Often resulting in osteoporosis, a reduction in the quantity of bone, or atrophy of skeletal tissue (Fig).  Hence, the bones become brittle, lose their elasticity, and fracture easily. FIGURE 15. Normal bone and Osteoporotic bone Clinical correlations Avascular Necrosis  Loss of arterial supply to an epiphysis or other parts of a bone results in the death of bone tissue— Avascular necrosis (nekrosis = deadness).  After every fracture, small areas of adjacent bone undergo necrosis.  In some fractures, avascular necrosis of a large fragment of bone may occur.  A number of clinical disorders of epiphyses in children result from avascular necrosis of unknown etiology (cause).  These disorders are referred to as Joints Joints (articulations) are unions or junctions between two or more bones or rigid parts of the skeleton.  CLASSIFICATION OF JOINTS  Three classes of joints are described 1. Synovial Joints 2. Fibrous Joints 3. Cartilaginous Joints FIGURE 16. The three classes of joints 1. Synovial Joints are the most common type Freely moveable joints  are united by a joint capsule spanning and enclosing a joint cavity  The joint cavity of a synovial joint, like the knee, is a potential space that contains a small amount of lubricating synovial fluid, secreted by the synovial membrane  Provide free movement between the bones they join  They are joints of locomotion, typical of nearly all limb joints 1. Synovial Joints 1. Plane joints  permit gliding or sliding movements in the plane of the articular surfaces.  The opposed surfaces of the bones are flat or almost flat, with movement limited by their tight joint capsules.  Plane joints are numerous and are nearly always small.  An example is the acromioclavicular joint between the acromion of the scapula and the clavicle 1. Synovial Joints 2. Hinge joints Permit flexion and extension only Permit movements that occur in one plane (sagittal) around a single axis that runs transversely Thus hinge joints are uniaxial joints. The joint capsule of these joints is thin and lax anteriorly and posteriorly where movement occurs; however, the bones are joined by strong, laterally placed collateral ligaments. Example: the elbow joint is a hinge joint. 1. Synovial Joints 3. Saddle joints Permit abduction and adduction as well as flexion and extension, movements occurring around two axes  Thus saddle joints are biaxial joints that allow movement in two planes, sagittal and frontal. The performance of these movements in a circular sequence (circumduction) is also possible. The opposing articular surfaces are shaped like a saddle (i.e., they are reciprocally concave and convex). 1. Synovial Joints 4. Condyloid joints Permit flexion and extension as well as abduction and adduction Thus condyloid joints are also biaxial. However, movement in one plane (sagittal) is usually greater (freer) than in the other. Circumduction, more restricted than that of saddle joints, is also possible. The metacarpophalangeal joints (knuckle joints) are condyloid joints. 1. Synovial Joints 5. Ball and socket joints Allow movement in multiple axes and planes flexion and extension, abduction and adduction, medial and lateral rotation, and circumduction  Thus ball and socket joints are multiaxial joints. In these highly mobile joints, the spheroidal surface of one bone moves within the socket of another. Example: the hip joint is a ball and socket joint in which the spherical head of the femur rotates within the socket formed by the 1. Synovial Joints 6. Pivot joints Permit rotation around a central axis; Thus they are uniaxial. In these joints, a rounded process of bone rotates within a sleeve or ring. The median atlantoaxial joint is a pivot joint in which the atlas (C1 vertebra) rotates around a finger-like process, the dens of the axis (C2 vertebra), during rotation of the head. FIGURE 17. The six major types of synovial joints plane, hinge, saddle, condyloid, ball and socket, and pivot JOINT VASCULATURE AND INNERVATION Joints receive blood from articular arteries that arise from the vessels around the joint Articular veins are communicating veins that accompany arteries (L. venae comitantes) Joints have a rich nerve supply provided by articular nerves with sensory nerve endings in the joint capsule  The Hilton law states that the nerves supplying a joint also supply the muscles moving the joint and the skin covering their distal attachments. Muscular system (mycology) Muscular system  The muscular system consists of all the muscles of the body. Types of Muscle (Muscle Tissue)  Muscle cells (muscle fibers) are specialized contractile cells.  They are organized into tissues that move body parts or temporarily alter the shape of internal organs  Three types of muscle are described based on distinct characteristics relating to:  Whether it is normally willfully controlled (voluntary vs. involuntary).  Whether it appears striped or unstriped when viewed under a microscope (striated vs. smooth or unstriated).  Whether it is located in the body wall (soma) and limbs or makes up the hollow organs (viscera, e.g., the heart) of the body cavities or blood vessels (somatic vs. visceral). Muscular system There are three muscle types: 1. Skeletal striated muscle is voluntary somatic muscle that makes up the gross skeletal muscles that compose the muscular system, moving or stabilizing bones and other structures (e.g., the eyeballs). 2. Cardiac striated muscle is involuntary visceral muscle that forms most of the walls of the heart and adjacent parts of the great vessels, such as the aorta, and pumps blood. 3. Smooth muscle (unstriated muscle) is involuntary visceral muscle that forms part of the walls of most vessels and hollow organs (viscera), moving substances through them by coordinated sequential contractions (pulsations or peristaltic contractions). TABLE 1. TYPES OF MUSCLE (MUSCLE TISSUE) Skeletal Muscles All skeletal muscles, commonly referred to simply as “muscles”  Most muscles are named on the basis of their function or the bones to which they are attached. for example, The abductor digiti minimi muscle, abducts the little finger. The sternocleidomastoid muscle attaches inferiorly to the sternum and clavicle and superiorly to the mastoid process of the temporal bone of the cranium. Other muscles are named on the basis of their position (medial, lateral, anterior, Skeletal Muscles  Muscles may be described or classified according to their shape, for which a muscle may also be named:  Flat muscles have parallel fibers often with an a poneurosis, for example, the external oblique and the sartorius.  Pennate muscles are feather-like in the arrangement of their fascicles, and may be unipennate, bipennate, or multipennate, for example, extensor digitorum longus (unipennate), rectus femoris (bipennate), and deltoid (multipennate).  Fusiform muscles are spindle shaped with a round, thick belly and tapered ends for example, biceps brachii. Cont’d….  Convergent muscles arise from a broad area and converge to form a single tendon, for example, pectoralis major.  Quadrate muscles have four equal sides, for example, the rectus abdominis, between its tendinous intersections.  Circular or sphincteral muscles surround a body opening or orifice, constricting it when contracted, for example, orbicularis oculi (closes the eyelids).  Multiheaded or multibellied muscles have more than one head of attachment or more than one contractile belly, respectively. Biceps muscles have two heads of attachment (e.g., biceps brachii), triceps muscles have three heads (e.g., triceps brachii), and the digastric and gastrocnemius muscles have two bellies FIGURE 18. Architecture and shape of skeletal muscles. The architecture and shape of a skeletal muscle depend on the arrangement of its fi bers. Skeletal Muscle Action All movements are the result of the coordinated action of many muscles. A muscle may work in the following four ways:  Prime mover: A muscle is a prime mover when it is the chief muscle responsible for a particular movement. For example, the quadriceps femoris is a prime mover in the movement of extending the knee joint  Antagonist: Any muscle that opposes the action of the prime mover is an antagonist. For example, the biceps femoris opposes the action of the quadriceps femoris when the knee joint is extended Cont’d…  Fixator: A fixator contracts isometrically (i.e., contraction increases the tone but does not in itself produce movement) to stabilize the origin of the prime mover so that it can act efficiently. For example, the muscles attaching the shoulder girdle to the trunk contract as fixators to allow the deltoid to act on the shoulder joint  Synergist: In many locations in the body, the prime mover muscle crosses several joints before it reaches the joint at which its main action takes place. To prevent unwanted movements in an intermediate joint, groups of muscles called synergists contract and stabilize the intermediate joints. For example, the flexor and extensor muscles of the carpus contract to fix the wrist joint, and this allows the long flexor and the extensor muscles of the fingers to work efficiently Nerves and Arteries to Muscles Variation in the nerve supply of muscles is rare  In the limb, muscles of similar actions are generally contained within a common fascial compartment and share innervation by the same nerves  When a nerve pierces a muscle, by passing through its fleshy portion or between its two heads of attachment, it usually supplies that muscle  Exceptions are the sensory branches that innervate the skin of the back after penetrating the superficial muscles of the back Cardiac Muscle Cardiac striated muscle forms the muscular wall of the heart, the myocardium are not under voluntary control  Heart rate is regulated intrinsically by a pacemaker they, in turn, are influenced by the ANS  Both types of striated muscle: skeletal and cardiac are further characterized by the immediacy, rapidity, and strength of their contractions  To support its continuous level of high activity, the blood supply to cardiac striated muscle is twice as rich as that to skeletal Smooth muscle  Smooth muscle, named for the absence of striations in the appearance of the muscle fibers under microscopy  It occurs in all vascularized tissue  It also makes up the muscular parts of the walls of the alimentary tract and ducts  Smooth muscle is found in skin, forming the arrector muscles of hairs associated with hair follicles  And in the eyeball, where it controls lens thickness and pupil size  Like cardiac striated muscle, smooth muscle is involuntary muscle  Its contraction can also be initiated by hormonal stimulation or by local stimuli The circulatory System The circulatory System The circulatory system transports fluids throughout the body It consists of the cardiovascular (heart and vessels)and lymphatic systems Circulatory Loops  The heart consists of two muscular pumps that divide the circulation into two components:  The pulmonary circulations  Systemic circulations or circuits  The circulatory System 1. Pulmonary Circulation Transports blood from the right ventricle through the pulmonary arteries to the lungs and returns it to the left atrium of the heart through the pulmonary veins. 2. Transports blood from the left ventricle through the aorta to all parts of the body and returns it to the right atrium through the  The circulatory System A. Heart Is a hollow, muscular, four-chambered organ that pumps blood to two separate circulatory loops  Is regulated in its pumping rate and strength by the ANS,  which controls a pacemaker (i.e., sinoatrial node). The circulatory System B. Blood Vessels  Transport blood through all parts of the body.  Most vessels of the circulatory system have three coats, or tunics:  Tunica intima, an inner lining. Capillaries consist only of this tunic  Tunica media, a middle layer consisting primarily of smooth muscle.  Tunica adventitia, an outer connective tissue layer or sheath  The tunica media is the most variable coat. Arteries, veins, and lymphatic ducts are distinguished by the thickness of this layer The circulatory System  There are four types of blood vessels: arteries, veins, capillaries. and sinusoids 1. Arteries  Carry blood from the heart to the capillary beds  Have thicker walls than do veins.  Do not have valves  Consist of three main types: elastic arteries, muscular arteries, and arterioles.  Arterioles are the smallest arteries,