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<ul><li> 1. Skeletal System By Dr. Shamanthakamani Narendran</li></ul><p> 2. 3. 4. INTRODUCTION </p> <ul><li>The skeletal system refers to the jointed framework of rigid bones which supports the soft tissues of the body. </li></ul><ul><li>There are 206 bones in the adult skeletal system. </li></ul><p> 5. 6. 7. </p> <ul><li>Importance of this system:</li></ul><ul><li>The bones form a complex lever system which permits body movements. </li></ul><ul><li>They form cages and boxes which protest fragile organs. e.g. the rib cage, breastbone (sternum) and backbone (vertebral column) protect the heart and lungs. </li></ul><ul><li>The bones given the body its shape. </li></ul><ul><li>As a prelude to the description of the skeletal system, thebody cavitieswill be discussed briefly, below. </li></ul><p> 8. BODY CAVITIES </p> <ul><li>The trunk of the human being is made up ofthreemain cavities </li></ul><ul><li>Thorax </li></ul><ul><li>Abdomen </li></ul><ul><li>Pelvis </li></ul><p> 9. THORACIC CAVITY </p> <ul><li>Thorax or chest extends from the bottom of the neck, above, to the diaphragm, below. </li></ul><ul><li>The diaphragm is a muscular dome which separates the thoracic and abdominal cavities, and plays an important part in respiration. </li></ul><ul><li>The thorax contains three cavities. </li></ul><ul><li>There cavities are all lined with a membrane which also covers the organs inside them. </li></ul><p> 10. </p> <ul><li>The central cavity is thepericardial cavity . </li></ul><ul><li>This contains the heart, covered by thepericardium . </li></ul><ul><li>On both sides of the pericardial cavity,</li></ul><p>there are two pleural cavities, which contains the lungs, covered bypleura . 11. ABDOMINAL CAVITY </p> <ul><li>The region of the body located below the chest and above the pelvis. </li></ul><ul><li>The chest and abdomen are separated by a muscular dome, the diaphragm. </li></ul><ul><li>Inside this cavity are the vital organs which play an important part in digestion (stomach, intestines, liver, pancreas, and others) and in excretion (kidneys). </li></ul><ul><li>These organs are covered by the membrane which lines the abdominal cavity theperitoneum . </li></ul><p> 12. </p> <ul><li>The muscles which form the anterior wall or the front of the abdomen, hold the organs in place and give support to them. </li></ul><p> 13. PELVIC CAVITY </p> <ul><li>The pelvic cavity lies within the bony which is made up of the lower part of the vertebral column (the sacral and coccygeal parts) and the hip bones on either side. </li></ul><ul><li>The peritoneum lines the pelvic cavity and also covers the organs inside it. </li></ul><p> 14. 15. CARTILAGE </p> <ul><li>Cartilage is flexible white tissue around the joints and in other parts of the body. </li></ul><ul><li>For example, cartilage is present in the windpipe ( trachea ), the sound box ( larynx ), the ears, and the tip of the nose. </li></ul><ul><li>It also makes up the discs between the vertebrae of the column</li></ul><ul><li>( backbone ) and the</li></ul><ul><li>surfaces of certain joints. </li></ul><p> 16. </p> <ul><li>In general Cartilageimproves flexibility ,Serves as padding , &amp;Prevents friction . </li></ul><ul><li>During early fetal life the human skeleton is composed mainly of cartilage, which is later replaced by bone. </li></ul><ul><li>Cartilage is subject to a number of disorders. </li></ul><ul><li>Arthritisproduces degeneration of the cartilage as well as the bones of the joints. </li></ul><ul><li>Avertebral discmay slip out of place and cause severe back pain. </li></ul><p> 17. BONE </p> <ul><li>Is a rigid structure of connective tissue interlaced with nerves and blood vessels. </li></ul><ul><li>It is hardened by deposits of (mainly) calcium phosphate. </li></ul><ul><li>The entire bone is sheathed in a tough tissue called theperiosteum . </li></ul><ul><li>Babies bones are pliable and contain a high proportion of cartilage, which is gradually replaced by more rigid bone tissue. </li></ul><p> 18. </p> <ul><li>In adults, each bone has a very dense outer layer with a high content of calcium. </li></ul><ul><li>It is this dense layer which makes bones opaque and hence visible on X-rays. </li></ul><ul><li>Under this layer, the</li></ul><ul><li>structure is spongy</li></ul><ul><li>with pores and</li></ul><ul><li>cavities of various</li></ul><ul><li>sizes. </li></ul><p> 19. </p> <ul><li>Bones are hinged and held together by ligaments to form the skeletal system. </li></ul><ul><li>This system provides support, mechanical leverage for movement, and protection for the vital organs. </li></ul><ul><li>Also, the red blood cells, suppliers of oxygen to the body, are produced in the red marrow of certain bones such as the vertebrae and ribs. </li></ul><ul><li>Generally, bone is as strong as cast iron, but infinitely lighter and more flexible. </li></ul><p> 20. </p> <ul><li>Its rigidity enables us to bear our own weight, plus the stress of lifting and carrying. </li></ul><ul><li>Since bones are hinged together with ingenious joints some working as levers, others as hinges this system also permits us to be amazingly agile. </li></ul><ul><li>Bones also store minerals such as calcium. </li></ul><p> 21. DEVELOPMENT OF BONES 22. 23. CLASSIFICATION </p> <ul><li>Since bones vary in shape their gross appearances have led to a classification into long bones , e.g. the bones of the limbs &amp;short bones , e.g. bones of the fingers and toes. </li></ul><ul><li>Based on whether the bones make up the central frame or the limbs, they have been classified as theaxial skeletal vertebral column, skull, and rib cage &amp;appendicular skeleton bones of the arms, hands, legs, feet, shoulder, and pelvic bones. </li></ul><p> 24. CLASSIFICATION OF BONES 25. JOINTS </p> <ul><li>The point where 2 bones comes into contact is called ajoint . </li></ul><ul><li>There are three main types of joints based on the type of material which is present between the bones. </li></ul><ul><li>Fibrous joints do not permit any movement, e.g. the structures between the skull bones. </li></ul><p> 26. </p> <ul><li>Cartilaginous joints permit slight movement, e.g. is the type of joint which exists between the upper and lower parts of the breast bone ( sternum ), before these parts fuse. </li></ul><p> 27. </p> <ul><li>Synovial joints have maximum movement. </li></ul><ul><li>The parts of the bones which are in contact are enclosed within ajoint capsule . </li></ul><ul><li>There isno continuitybetween the two (or more) bones. </li></ul><ul><li>The bone surface are covered with a special type of cartilage articular cartilage . </li></ul><p> 28. </p> <ul><li>It has a very low coefficient of friction. </li></ul><ul><li>The sliding contact (ice on ice) is further enhanced by the presence of a viscous fluid thesynovial fluid . </li></ul><ul><li>This fluid is partially secreted by a membrane, thesynovial membrane . </li></ul><ul><li>It lines the joint capsule, and covers the exposed surfaces of the bones, ligaments, and tendons within the capsule. </li></ul><p> 29. </p> <ul><li>Itdoes notcover the articular cartilage and two other structures articular discs and menisci.</li></ul><ul><li>(These are cartilaginous structures which improve the congruity of the joint surfaces.) </li></ul><ul><li>The membrane has two main functions it is one of the contributors to the production of synovial fluid, it also has cells which are capable of ingesting debris and particulate matter. </li></ul><ul><li>The synovial fluid is a viscous, pale yellow fluid. </li></ul><p> 30. </p> <ul><li>In human joints it is present in small amounts. </li></ul><ul><li>Usually not more than 0.5ml can be aspirated (withdrawn by suction), even from the large joints (e.g. knee). </li></ul><ul><li>Functions include lubrication, reduction of erosion, and provision of nutrition for articular cartilages, articular discs, and meniscus </li></ul><p> 31. TYPES OF SYNOVIAL JOINTS </p> <ul><li>Hingejoint resemble hinges, and are designed to restrict movement to one plane, e.g. are the elbow and knee joints (to be precise the latter is described as a bicondylar joint). </li></ul><ul><li>Sliding/Planejoints are appositions of almost flat surfaces, e.g. wrist joint. </li></ul><ul><li>Pivotjoints are those in which rotation occurs around apivot .This type of movement occurs between the first and second vertebrae (pivot = pin or shaft on which a wheel or body turns) </li></ul><p> 32. </p> <ul><li>Ball-and-socketjoints are formed between a sphere like head and an opposing cup, e.g. hip and shoulder joints. These joints allow maximum movement. </li></ul><p> 33. TYPES OF JOINTS 34. TENDONS </p> <ul><li>A tendon is a strong elastic tissue which connects muscles to bones. </li></ul><ul><li>Tendons may be short and thick, like those which attach the biceps to the shoulder. </li></ul><ul><li>Others are long and slender, like those which run from the muscles in the forearm across the back of the wrist to the bones of the fingers. </li></ul><ul><li>A tendons acts as an anchor for the muscles. </li></ul><ul><li>They do not stretch. </li></ul><p> 35. 36. LIGAMENTS </p> <ul><li>A ligament is band of tough, elastic tissue which binds together the bones as a joint. </li></ul><ul><li>A major joint, such as the elbow has a set of overlapping ligaments to support the three bones. </li></ul><ul><li>A ligament can stretch. </li></ul><ul><li>Forcing a joint beyond its normal range of movement overstretches or tears the ligaments and causes asprainwhich generally heals if the joint is rested. </li></ul><p> 37. 38. BURSAE / BURSA </p> <ul><li>A bursa is a fibrous sac lined with synovial membrane, bursae facilitate movement without friction, and may be present between tendon and bone, skin and bone, and between two muscles. </li></ul><p> 39. SPECIFIC BONES some salient features </p> <ul><li>The skull </li></ul><ul><li>Protects the brain. </li></ul><ul><li>The bones of the skull are held together by fibrous joints. </li></ul><ul><li>These joints are not fused at birth, thus allowing for growth of the infants skull, and the area between the bones is soft thefontanelles . </li></ul><ul><li>These fontanelles are all fused by eighteen months. </li></ul><p> 40. </p> <ul><li>The skull bones contain large hallow spaces or air cavities inside them. </li></ul><ul><li>There are four sets of hallows in the skull, around the nose. </li></ul><ul><li>These are called paranasal sinuses. </li></ul><ul><li>They are situated in the forehead, behind and below the forehead, in the cheekbones, and at the back of the nasal passages. </li></ul><ul><li>These sinuses have passages leading into the nose. </li></ul><ul><li>Their function is uncertain. </li></ul><p> 41. </p> <ul><li>They lighten the skull and add resonance to the voice. </li></ul><ul><li>Within the skull there are three tiny bones, which help in the transmission of sound. </li></ul><ul><li>They are located in the middle ear. </li></ul><ul><li>The jaw bone or mandible comprises the lower jaw and contains the lower row of teeth. </li></ul><p> 42. </p> <ul><li>Teeth </li></ul><ul><li>The teeth are embedded in the upper and lower jaws. </li></ul><ul><li>They contain a hard bony substance. </li></ul><ul><li>Above the gum this is covered with tooth enamel the ivory colored part which we can see. </li></ul><ul><li>This is the hardest material in the body. </li></ul><ul><li>It cannot be replaced. </li></ul><ul><li>If it gets worn away the inner core the pulp is exposed. </li></ul><p> 43. </p> <ul><li>The pulp has both blood vessels and nerves. </li></ul><ul><li>The presence of the latter is responsible for toothache. </li></ul><ul><li>There are 20 milk or</li></ul><ul><li>temporary teeth. </li></ul><ul><li>Permanent teeth are</li></ul><ul><li>32 in number. </li></ul><p> 44. </p> <ul><li>Teeth of a child </li></ul><ul><li>The face of a six-year-old child showing the milk teeth in position and the developing permanent teeth (in red) </li></ul><p> 45. </p> <ul><li>Vertebral column </li></ul><ul><li>Three important functions: </li></ul><ul><li>To support the human body in the upright position. </li></ul><ul><li>To protect the spinal cord </li></ul><ul><li>To allow movement and locomotion. </li></ul><ul><li>The vertebral column consists of 24 separate bony vertebrae, together with 5 fused vertebrae which form the sacrum, and usually 4 fused vertebrae which form the coccyx. </li></ul><p> 46. </p> <ul><li>The 24 separate vertebrae include the topsevenin theneck , thecervical vertebrae . </li></ul><ul><li>The first of these, the atlas, supports the skull. </li></ul><ul><li>Below thetwelvechest orthoracicvertebrae, to which the ribs are attached. </li></ul><ul><li>Below are thefive lumbarvertebrae, which lie in the abdomen. </li></ul><ul><li>Thesacrumand then thecoccyx(tail bone) are fused, and lie below. </li></ul><p> 47. 48. </p> <ul><li>The entire vertebral column is made up of sets of vertebrae resting on each other. </li></ul><ul><li>The vertebrae consist of avertebral body , which faces forwards. </li></ul><ul><li>An arch projects backwards, and the bony processes at the end of it can be felt in the back. </li></ul><ul><li>The arch encloses a hallow area which is called thespinal canal , as thespinal cordpasses through it. </li></ul><p> 49. </p> <ul><li>Nerves arising from the spinal cord pass out through special spaces. </li></ul><ul><li>There are specific parts where the ribs are attached, and where the vertebrae articulate with those above and below them. </li></ul><ul><li>Between adjacent vertebral bodies, with the exception of the first and second cervical vertebrae, there is an intervertebral disc. </li></ul><ul><li>There are also strong ligaments along the anterior and posterior surfaces of the vertebrae, keeping them in place. </li></ul><p> 50. </p> <ul><li>The muscles of the vertebral column and their ligaments are also essential for its stability. </li></ul><ul><li>Theintervertebral discsplay a vital role in the functioning of the spine. </li></ul><ul><li>These discs have two important functions </li></ul><ul><li>* they play an important part in the transmission of loads from one vertebral body to the next. </li></ul><ul><li>*they allow, and restrain movements at the inter (vertebral) body joints. </li></ul><p> 51. 52. </p> <ul><li>The discs have a central part made up of semifluid gel thenucleus pulposus , and surrounding this, concentric layers of fibrous tissue, called theannulus fibrosus . </li></ul><ul><li>It is important that the nucleus pulposus is fluid, as it can be deformed under pressure without a change in volume. </li></ul><ul><li>This enables it to accommodate to movement and to transmit some of the compressive load from one vertebra to the next. </li></ul><p> 53. </p> <ul><li>The discs are thickest in thelumbarregion where they are required to bear a greater proportion of the body weight. </li></ul><ul><li>The discs tend to deteriorate with age. </li></ul><ul><li>With age, or due to excessive strain a condition called slipped disc may occur. </li></ul><ul><li>In this condition, the nucleus pulposus bulges through the annulus fibrosus and protrudes. </li></ul><ul><li>This may compress the nerve arising from the spinal cord, thus causing pain. </li></ul><p> 54. </p> <ul><li>Certain postures increase the risk of a slipped disc. </li></ul><ul><li>Postures to be avoided are those in which the spine is bent and compressed . </li></ul><ul><li>For e.g. if one bends to pick up a heavy weight, it is alwaysbest to bend ones knees and hips, and minimize spine flexion . </li></ul><p> 55. </p> <ul><li>Spinal curves </li></ul><ul><li>When viewed from the side, the vertebral column shows four main curves. </li></ul><ul><li>The lowercervicalspine isconvexforwards, thethoracicpart isconcaveforwards, thelumbarcurve isconvexforwards, and thesacrumisconcaveforwards. </li></ul><ul><li>The shape varies in normal spines. </li></ul><ul><li>Lateral curves or scoliosis are also seen in some normal individuals. </li></ul><p> 56. Rib cageSternum </p> <ul><li>Rib cage </li></ul><ul><li>The rib cage is made up of twelve pairs of ribs, which articulate with the vertebrae at the back, and the breastbone or sternum, in front. </li></ul><p> 57. </p> <ul><li>The appendicular skeleton </li></ul><ul><li>This includes the bones of the upper and lower limbs, and the bones which articulate with the axial skeleton. </li></ul><ul><li>The upper limb consists of thehumerusin the arm. </li></ul><ul><li>The humerus articulates with two bones at the elbow. </li></ul><ul><li>These are theradiusand theulna . </li></ul><ul><li>They lie in the forearm. </li></ul><p> 58. </p> <ul><li>At its upper end, the humerus forms theshoulder joint , where it articulates with the collar bone ( clavicle ) and the shoulder blade ( scapula ). </li></ul><ul><li>The radius and ulna form the wrist joint along with thecarpal bones . </li></ul><ul><li>Themetacarpal bonesmake up the hand, and in the fingers there are tiny bones with joints in between (thephalanges ). </li></ul><ul><li>The lower limb has the long, heavy thigh bone thefemur . </li></ul><p> 59. </p> <ul><li>At its upper end it articulates with thehip boneto form the hip joint. </li></ul><ul><li>At its lower end it articulates with the bones of the lower leg thetibiaandfibula . </li></ul><ul><li>The ankle joint is formed by these two bones, and thetarsalor ankle bones. </li></ul><ul><li>Metatarsal bonesmake up the feet, while (as for the hand) in the digits there are thephalanges . </li></ul><p> 60. MUSCULOSKELETAL SYSTEM </p> <ul><li>In man, as in other animals, movement is carried out by muscles. </li></ul><ul><li>Muscle tissue is made up of elastic cells which can repeatedly contract and relax. </li></ul><ul><li>These cells often very long, hence they are calledfibers . </li></ul><ul><li>Based on their structure and function muscles are classified asthreegroups - Voluntary muscle, Cardiac muscle, and Smooth muscle </li></ul><p> 61. </p> <ul><li>Voluntary muscleis so called because it resp...</li></ul>