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Skeletal system Skeleton • Axial Skeleton • Support and protect organs of the head, neck, and trunk • Skull • Vertebral Column • Thoracic cage • Appendicular Skeleton • Bones of limbs • Bones that anchor limbs to axial skeleton • Pectoral Girdle • Pelvic girdle Functions • 1. Support – A hard framework that supports the weight of the body and cradles its soft organs Functions • 2. Protection – Skull forms a protective case for the brain – Vertebrae surround spinal cord – Rib cage protect the organs of the thorax Functions • 3. Movement – Skeletal muscles attach to the bones by tendons and use the bones as levers to move the body and its parts. – The arrangement of bones and the structure of the joints determine the types of movement that are possible Functions • 4. Mineral Storage – Reservoir for minerals, especially calcium and phosphate – Stored minerals are released into the bloodstream as ions for distribution to all parts of the body as needed. – If body needs more, osteoclasts break down bone to release Ca into blood – Osteoporosis: disorder caused by excessive loss of bone volume and mineral content *Bones easily fractured *Most common in light skinned females after menopause *Risk increases if decrease calcium intake, decrease exercise, and decrease estrogen *May be prevented if dietary intake of 800mg Ca before age 35, regular excercise Functions • 5. Blood-cell formation – Bones contain red and yellow bone marrow in the cavity of long bones, spongy bone, osteonic canals of compact bone. – In adults red marrow is found in spongy bone of ribs, sternum, vertebrae, pelvis and epiphyses of humerus and femur – Red marrow makes the blood cells (red, white, and platelets), and yellow marrow is a site of fat storage, with little or no role in blood-cell formation – With increase age, red marrow is replaced by yellow marrow. Classification of Bones • The shape of each bone fills a particular need • Bones are classified by their shape as long, short, flat or irregular 1. Long Bones • Long bones are longer than they are wide • Most bones in the limbs are long bones • named for elongated shape, not for overall size 2. Short Bones • Roughly cube shaped • Ex. Bones of wrist • Sesamoid bones are a special type of short bone that forms within a tendon (patella) 3. Flat Bones • Flat bones are thin, flattened, and usually curved. • Ex. Skull, ribs, sternum, and scapula 4. Irregular Bones • Various shapes that don’t fit into previous categories • Ex. Vertebrae and hip bones Gross Anatomy of Bones • Compact bone: almost every bone of the skeleton has a dense outer layer that looks smooth and solid to the naked eye. This external layer is compact bone. Composes the wall of the diaphysis • Internal to this is spongy bone (cancellous bone) a honeycomb of small needle like or flat pieces called trabeculae (little beams) Open spaces between the trabeculae are filled with red or yellow bone marrow Found in epiphysis, lightweight Structure of a Typical Long Bone A. The tubular diaphysis or shaft forms the long axis of a long bone B. The epiphyses are the ends of bones C. Periosteum- covering of the bone, made of fibrous c.t.; place of attachment for ligaments and tendons, helps repair bone tissue D. Medullary cavity- hollow chamber in the diaphysis; lined by the endosteum, filled with marrow (marrow cavity) Bone Structure • Matrix is dense and mostly calcium phosphate with some collagen fibers • -contains bones cells within pockets (lacunae) • 1. Osteocytes- mature bone cells which recycle calcium in the matrix and repair damaged bone • 2. osteoblasts- cells actively depositing bone matrix • 3. osteoclasts- cells actively removing bone matrix • Functional Unit of Bone is the Osteon. – Osteocytes are arranged in concentric layers (lamellae) around a central canal which contains one or more blood vessels • Narrow passageways (canaliculi) extend between the lacunae and blood vessels to form a network for exchange of nutrients, gases, and wastes Bone Development and Growth • During development cartilage is replaced by bone (ossification) • 2 types: – Intramembranous ossification • Occurs in the deeper layers of the dermis (fibrous connective tissue) • Some skull bones, mandible, clavicle Endochondral ossification – Most bones form this way – Within cartilage – 1. cavities form within the cartilage – 2. blood vessels grow around the edges – 3. cartilage cells convert to osteoblasts & a layer of bone forms around the shaft Endochondral ossification – 4. blood vessels penetrate the central region & osteoblasts start producing spongy bone – 5. remodeling forms the marrow cavity & bone of the shaft becomes thicker & the cartilage near the epiphysis is replaced by bone Increasing the length of bone • 1. Osteoblasts from the diaphysis continually invade the cartilage of the epiphyses & ossify • 2. new cartilage is continually added to the epiphyses. This region is the epiphyseal plate. This causes the bone to lengthen. Increasing the length of bone • 3. at puberty, the onset of hormones stimulates bone growth. Osteoblasts produce bone faster than the cartilage can keep up. The epiphyseal plate narrows and disappears. The epiphyseal line is all that remains. THE BONE STOPS GROWING Axial Skeleton • Bones of the skull, thoracic cage, & vertebral column The skull (22 bones) Cranium • • • • • Occipital bone: posterior & inferior surfaces Frontal bone: forms forehead & roof orbits Parietal bones (2): superior & lateral surfaces Temporal bones (2): lateral & inferior Sphenoid bone: extends from one side, behind the eyes, and to the other side • Ethmoid bone: forms part of the orbital wall, floor of cranium, roof of nasal cavity, & nasal septum Face • Maxillae (2): forms upper jaw • Palatine bones (2): form posterior of hard palate (roof of mouth) • Nasal bones (2): extend from bridge of nose to nares • Vomer: inferior portion of nasal septum • Inferior nasal conchae (2): scroll like bone in nasal cavity • Zygomatic bones (2): Cheek bones • Lacrimal bones (2): smallest; in the medial portion of each orbit • Mandible: lower jaw Vertebral Column (26 bones) • Vertebrae (24) – Cervical vertebrae (7) • Neck; C1-C7 • Sacrum – 5 bones fused into 1 • Thoracic (12) vertebrae – Midback; articulates with the ribs; T1--T12 – Lumbar (5) vertebrae » Lowerback; L1L5 Coccyx 4 bones fused into 1 Vertebra anatomy • 1. body-supports weight • 2. vertebral foramen- opening for spinal cord • 3. transverse process- site of muscle attachment; may articulate with ribs. • 4. spinous process- posterior projection (what you feel) • 5. superior & inferior articular processes where vertebrae articulate with one another • Intervertebral discs- discs of fibrocartilage which help absorb shock Thoracic Cage • Ribs (costae) 12 pairs – 1-7 Vertebrosternal (true) ribs connected to vertebrae & sternum – 8-12 (false ribs) • 8-10 Vertebrochondral ribs connected to vertebrae, ribs fused together to connect to sternum • 11-12 vertebral ribs (floating ribs) connected to vertebrae only • Sternum (breast bone) – Manubrium-articulates with clavicles & 1st ribs – Body- ribs attach here – Xiphoid process- diaphragm and abdominal muscle attach here Appendicular Skeleton • 126 bones • 1. Pectoral girdle (shoulder girdle) – Connect arms to trunk of body – A. clavicle (2) (collarbone) s-shaped bones; articulate with manubrium of sternum – B. scapula (2) (shoulder blade) triangular bones; articulate with the humerus • 2. humerus (2) – Extends from the scapula to the elbow • 3. Ulna (2) – Bone of forearm (medial) – Forms the point of the elbow • 4. Radius (2) – Bone of forearm (lateral) • 5. Carpals (16) – Bones of the wrist (capitate, hamate, lunate, pisiform, scaphoid, trapezium, trapezoid, triqetrum) • 6. Metacarpals (10) – Bones of the hand • 7. phalanges (56) – Bones of the fingers, thumbs, and toes – 2bones in each thumb and great toe • 8. Pelvic girdle – Connect the legs to the axial skeleton – A. coxa (2) (hip bone) a fusion of 3 bones • 1. ilium- large flared bones • 2. ischium- inferior & posterior; the body weight is on this when seated • 3. pubis- inferior & anterior; the two pubic bones articulate at the pubic symphysis (a pad of fibrocartilage • b. differences between male and female pelvis – 1. women- enlarged pelvic outlet; less curvature of the sacrum & coccyx; low pelvis; pubic arch greater than 100° – 2. men- opposite of above; pubic arch 90° or less • 9. femur (2) – Bones of thigh – Longest and heaviest bones of the body • 10. Patella (2) – Bones of the knee • 11.tibia (2) – Large medial bone of the lower leg (shin) • 12. fibula (2) • Slender lateral bone of the lower leg • 13. tarsals (14) – Bones of the ankle • A. talus -2nd largest foot bone; articulates with the tibia • B. calcaneus- heel bone; largest bone of the foot • 14. metatarsals (10) – Bones of feet JOINTS: WHERE TWO BONES MEET • JOINTS, OR PLACES WHERE TWO BONES COME TOGETHER, PERMIT THE BONES TO MOVE WITHOUT DAMAGING EACH OTHER. • Joints are responsible for keeping bones far enough apart so they do not rub against each other as they move. At the same time, joints hold the bones in place. • THE CLASSIFICATION OF JOINTS IS BASED ON THE AMOUNT OF MOVEMENT POSSIBLE: • A. SYNARTHROSIS IS AN IMMOVABLE JOINT; THEY ARE OFTEN CALLED FIXED JOINTS, AND ALLOW NO MOVEMENT BETWEEN BONES. These joints are interlocked and held together by Connective Tissue, or they are fused together. The places where the bones of the SKULL meet (SUTURES) are examples of immovable joints. • B. AMPHIARTHROSIS IS A SLIGHTLY MOVABLE JOINT. (SEMI MOVABLE JOINTS) These joints permit a small amount of movement. These bones are farther apart from each other than immovable joint bones. The joints between the two bones of the lower leg (TIBIA and FIBULA) and the joints of the vertebrae are examples of slightly movable joints. • C. DIARTHROSIS IS A FREELY MOVABLE JOINT. MOST OF THE JOINTS OF THE BODY ARE FREELY MOVABLE JOINTS. • In Synovial Joints, the ends of the bones are covered with a layer of Cartilage that provides a smooth surface at the joint. • The joints are also surrounded by a Fibrous Joint Capsule that helps hold the bones together and at the same time allows for movement. Fibrous Joint Capsule • One of the layers of the joint capsule may thicken to form ligaments. • ligaments are attached to the membranes that surround bones and hold bones together and in place. • The synovial memberane of the joint capsule produces synovial fluid, which forms a thin lubricating film over the surface of a joint and protects the ends of bones from friction. • In some freely movable joints, small pockets of synovial fluid called bursae form. Bursae reduce the friction between the bones of a joint and also acts as a tiny shock absorber. • If a joint is injured, too much fluid moves into the bursa, causing it to swell and become painful, a condition called BURSITIS. • 9. A more serious disorder that affects the joints is ARTHRITIS or INFLAMMATION OF THE JOINT. There are Two Forms of Arthritis that affect joints. • A. RHEUMATOID ARTHRITIS develops when the Immune System begins to attack the body. The joints become inflamed, swollen, stiff, and deformed. • B. OSTEOARTHRITIS - a Degenerative Joint Disease (DJD) in which the cartilage covering the surface of bones becomes thinner and rougher. As a result, bone surfaces rub against each other, causing severe discomfort. • Synovial Joints are grouped according to the shapes of surfaces of the adjacent bones. • • A. BALL AND SOCKET JOINT - Permits circular movement - the widest range of movement. THE SHOULDER Joint, which enables you to move your arm up, down, forward and backward, as well as to rotate it in a complete circle. • B. HINGE JOINT - Permits a back-and-forth motion. The Knee enables your leg to flex and extend. The Elbow, which allows you to move your forearm forward and backward. • C. PIVOT JOINT - Permits rotation of one bone around another. The elbow enables your hand to turn over. It also allows you to turn your head from side to side. • D. GLIDING JOINT - Permits a sliding motion of one bone over another. Found at the ends of the collarbones, between wrist bones, and between anklebones. • E. SADDLE JOINT - Permits movement in two planes. This type of joint is found at the base of the thumb. • F. CONDYLOID JOINT - Allows for a hinge type movement in two directions. The joints that connect fingers with the palm and toes with the soles of feet are examples. Types of movement and examples (with muscles) flexion- move lower leg toward upper extension- straightening the leg hyperextension- increasing the angle past normal abduction- moving leg away from body adduction- movong leg toward the body rotation- around its axis supination- rotation of arm to palm-up position pronation- palm down circumduction- swinging arms in circles inversion- turning foot so sole is inward eversion- sole is out Elevation and depression- raising body part up or down • Dorsiflexion-flexion of ankle elevation of sole (stand on heels) • Plantar flexion- extend ankle elevate heel (stand on tip toes • Protraction moving forward (thrusting chin forward) • Retraction- moving a part backward (pulling chin back) • Opposition-touching the thumb to the little finger • Gliding- bones glide past each other (carpals, tarsals, vertebrae) Types of bone breaks Simple (Closed)- skin is not pierced Compound (Open)- skin is pierced Complete- bone is broken in half Incomplete- not broken through Linear-parallel to the long axis Transverse- perpendicular to the bone’s long axis Compression- bone is crushed Greenstick- incomplete break on outer arc (the way a green twig breaks) Comminuted- broken into several pieces (3+) Spiral- twisted (common sports fracture) Epiphyseal- epiphysis separates from the diaphysis along the epipyseal plate Depressed- broken bone portion pressed inward (typical in skull fracture) Fracture repair (189p) Hematoma- blood clot in space between edges of break Fibrocartilage callus- begins tissue repair Bony callus- osteoblasts produce trabeculae (structural support) of spongy bone and replace fibrocartilage Remodeling- osteoblasts build new compact bone, osteoclasts build new medullary cavity