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Chapter 5

Chapter 5. The Skeletal System. Introduction. The adult skeleton is composed of 206 bones The skeletal system is subdivided into 2 divisions: Axial skeleton Appendicular skeleton The skeletal system includes joints, cartilages, & ligaments. Bones: An Overview. Functions of the bones

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Chapter 5

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  1. Chapter 5 The Skeletal System

  2. Introduction • The adult skeleton is composed of 206 bones • The skeletal system is subdivided into 2 divisions: • Axial skeleton • Appendicular skeleton • The skeletal system includes joints, cartilages, & ligaments

  3. Bones: An Overview • Functions of the bones • Support—bones form the internal framework that supports & anchors all soft organs • Protection—bones protect body organs • Movement—skeletal muscles, attached to bones by tendons, use the bones as levers to move the body & its parts • Blood Cell Formation- produced in red marrow • Storage-stores lipids in yellow marrow, and

  4. Bones: An Overview • Functions of the bones • Storage—fat is stored in the internal cavities of bones, and bone serves as a storehouse for minerals such as calcium • Blood cell formation—this process is also called hematopoiesis & occurs within the marrow of certain bones

  5. Classification of Bones • There are 2 basic types of bones • Compact bone—dense & looks smooth • Spongy bone—composed of small needlelike pieces of bone & lots of open space • Bones are classified into 4 groups according to shape • Long bones—longer than they are wide; mostly compact bone; includes all the bones of the limbs

  6. Classification of Bones • Bones are classified into 4 groups according to shape • Short bones—cube-shaped; mostly spongy bone; includes all the bones of the wrist & ankle & also the patella • Flat bones—thin, flat, & curved; 2 thin layers of compact bone with a layer of spongy bone in between; includes the bones of the skull, ribs, & sternum • Irregular bones—bones that do not fit any of the above categories; includes the bones of the hip & vertebrae

  7. Classification of Bones

  8. Structure of a Long Bone • Diaphysis • Shaft of the bone • Makes up most of the bone’s length & is composed of compact bone • Periosteum • Fibrous connective tissue membrane • Covers & protects the diaphysis

  9. Structure of a Long Bone • Epiphyses • Ends of the long bone—proximal & distal • Consists of a thin layer of compact bone that encloses an area filled with spongy bone • Articular cartilage • Covers the external surface of the epiphyses • It provides a smooth, slippery surface that decreases friction at joint surfaces

  10. Structure of a Long Bone • Medullary cavity • The cavity of the shaft that is primarily a storage area for adipose tissue • Also known as the yellow marrow cavity

  11. Structure of a Long Bone

  12. Bone Formation, Growth, & Remodeling • The skeleton is formed from two of the strongest & most supportive tissues in the body—cartilage & bone • In embryos, the skeleton is primarily made of hyaline cartilage, but in the young child most of the cartilage has been replaced by bone.

  13. Bone Formation, Growth, & Remodeling • Ossification—process of bone formation & involves 2 phases: • The hyaline cartilage is completely covered with bone matrix by bone-forming cells called osteoblasts. • The hyaline cartilage is digested away, opening a medullary cavity within the newly formed bone.

  14. Bone Formation, Growth, & Remodeling

  15. Bone Formation, Growth, & Remodeling • Bones are always changing & are remodeled in response to changes in 2 factors: • Calcium levels in the blood • If blood calcium levels are too low, osteoclasts (bone-destroying cells) break down bone matrix & release calcium into the blood. • If blood calcium levels are too high, calcium is deposited in bone matrix as hard calcium salts. • The pull of gravity & muscles on the skeleton

  16. Bone Formation, Growth, & Remodeling • Bone remodeling is essential if bones are to retain normal proportions & strength during long-bone growth as the body increases in size & weight

  17. Bone Fractures • Bones are susceptible to fractures, or breaks, all through life. • During youth, most fractures result from exceptional trauma that twists or smashes the bones. In old age, bones thin & weaken, & fractures occur more often.

  18. Bone Fractures • 2 common types of fractures: (p 123) • Simple (closed) fractures = a fracture in which the bones breaks cleanly but does not penetrate the skin • Compound (open) fractures = when the broken bone ends penetrate through the skin • Fractures are treated by reduction—realignment of the broken bone ends

  19. Bone Fractures

  20. Axial Skeleton • Forms the longitudinal axis of the body • Divided into 3 parts • Skull—formed by 2 sets of bones • Cranium—encloses & protects the brain tissue; made up of several smaller bones (pp 126-127) • Frontal bone—forms the forehead • Parietal bones—forms the superior & lateral walls • Temporal bones—inferior to the parietal bones • Occipital bone—forms the back of the cranium • Sphenoid bone—butterfly-shaped & forms part of the floor of the cranial cavity • Ethmoid bone—lies anterior to the sphenoid & forms the roof of the nasal cavity

  21. Axial Skeleton • Facial bones—hold the eyes in position & allow the facial muscles to show our feelings (p 129) • Maxillae—upper jaw • Palatine bones—form the posterior part of the hard palate • Zygomatic bones—cheekbones • Lacrimal bones—medial walls of the eyes & has a groove that serves as a passageway for tears • Nasal bones—forms the bridge of the nose • Vomer bone—single bone in the median line of the nasal cavity (nasal septum) • Inferior conchae—curved bones projecting from the lateral walls of the nasal cavity • Mandible—lower jaw; the largest & strongest bone of the face!!!

  22. Axial Skeleton • Fetal skeleton—the skull of a fetus or newborn infant is different from an adult skull. When a baby is born, its skeleton is unfinished. The skull also has regions that yet to be converted to bone which are called fontanels. These are also known as the “soft spots.”

  23. Axial Skeleton • Vertebral Column (p 131) • Extends from the skull to the pelvis • Formed from 26 irregular bones • Running through the central cavity of the vertebral column is the spinal cord • The vertebrae are separated by pads of cartilage-intervertebral discs-cushion the vertebrae • The spinal cord curves & forms an S-shaped structure • Abnormal spinal curvatures (p 132) • Scoliosis • Kyphosis • lordosis

  24. Axial Skeleton • 3 main types of vertebrae • Cervical vertebrae • Identified as C1 to C7 • Form the neck region to the spine • Thoracic vertebrae • Identified as T1 to T12 • Larger than cervical vertebrae • Lumbar vertebrae • Identified as L1 to L5 • Where most of the stress on the vertebral column occurs • Sacrum—formed by the fusion of 5 vertebrae • Coccyx—formed by the fusion of 3-5 tiny vertebrae; also known as the human “tailbone”

  25. Axial Skeleton

  26. Axial Skeleton

  27. Axial Skeleton • Bony thorax—aka the thoracic cage (p 135) • Sternum • Aka the breastbone • A flat bone & the result of the fusion of 3 bones: • Manubrium • Body • Xiphoid process • Ribs • 12 pairs • Males DO NOT have 1 rib less than females!!! • 3 types of ribs: • True ribs—the 1st 7 pairs that are attached directly to the sternum • False ribs—the next 5 pairs that are attached to the sternum • Floating ribs—the last 2 pairs of false ribs that lack sternal attachment

  28. Axial Skeleton

  29. Appendicular Skeleton • Composed of 126 bones of the limbs & pectoral & pelvic girdles • Bones of the shoulder girdle (p 139) • Clavicle—aka the collarbone • Scapula—aka the shoulder blades • Bones of the upper limbs (pp 140-141) • Arm—formed by a single bone=humerus • Forearm—2 bones: • Radius—on the thumb side • Ulna—on the pinky side

  30. Appendicular Skeleton

  31. Appendicular Skeleton

  32. Appendicular Skeleton • Hand—3 sets of bones • Carpals—8 bones that make up the wrist • Metacarpals—the palm of the hand • Phalanges—bones of the fingers • Bones of the pelvic girdle (p 142) • Formed by 2 coxal bones called hip bones • Each hip bone is formed by the fusion of 3 bones: • Ilium • Ischium • pubis

  33. Appendicular Skeleton

  34. Appendicular Skeleton • Differences between the male & female pelvis: • Female pelvis is shallower • Female bones are lighter & thinner • Female sacrum is shorter & less curved • Bones of the lower limbs (pp 144-145) • Thigh—formed by a single bone=femur • Leg—2 bones • Tibia—shinbone=larger & more medial • Fibula—lies next to the tibia

  35. Appendicular Skeleton

  36. Appendicular Skeleton • Foot—3 sets of bones • Tarsals—7 bones that make up the posterior foot • Metatarsals—the sole of the foot • Phalanges—the bones of the toes

  37. Appendicular Skeleton

  38. Joints • Also called articulations • 2 main functions • Hold bones together securely • Give the skeleton mobility • Classified in 2 ways • Functionally • Structurally

  39. Joints • Functional classification--focuses on the amount of movement allowed by the joint • Immovable joint • Slightly movable joints • Freely movable joints • Structural classification—focuses on the type of tissue • Fibrous joints—bones are united by fibrous tissue • Cartilaginous joints—bones are united by cartilage • Synovial joints—joint cavity contains synovial fluid

  40. Joints • Types of synovial joints based on shape • Plane joint—short slipping or gliding; ie joints of the wrist • Hinge joint—movement in one direction; ie elbow, ankle, & the joints between the bones of the fingers • Pivot joint—rotating movement; ie between the radius & ulna • Condyloid joint—bones move from side to side or back & forth; ie your knuckles

  41. Joints • Saddle joint—same movement as condyloid; ie twiddling your thumbs • Ball-and-socket joint—head of one bone fits into a round socket; ie shoulder & hip joint

  42. Joints

  43. Joints • Inflammatory disorders of joints • Arthritis • Inflammation of the joint • Most widespread disease in the U.S. • Symptoms=pain, stiffness, & swelling of the joint • Osteoarthritis • Most common type of arthritis • Chronic degenerative condition that affects the aged

  44. Joints • Rheumatoid arthritis • Chronic inflammatory disorder • Affects more women than men • The body’s immune system attempts to destroy tissues • Gout • Uric acid accumulates in the blood & may be deposited as needle-shaped crystals in the soft tissues of joints • Usually affects the great toe

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