Chapter 5:The skeletal system

1. Chapter 5:The skeletal system Anatomy & Physiology

2. The Skeletal System • Parts of the skeletal system • Bones (skeleton) • Joints • Cartilages • Ligaments (connect bone-to-bone) • Two subdivisions of the skeleton • Axial skeleton • Appendicular skeleton

3. Functions of Bones • Support the body • Provides internal framework • Protect soft organs • i.e. brain, vital organs in thorax, spinal cord • Allow movement due to attached skeletal muscles • Bones serve as attachment points • Store minerals and fats • Blood cell formation • Hematopoisesis occurs in some bone marrow cavities

4. Bones of the Human Body • The adult skeleton has 206 bones • Two basic types of bone (osseous) tissue • Compact bone • Dense and smooth appearance • Spongy bone • Small needle-like pieces of bone • Many open spaces (porous)

5. Classification of Bones on the Basis of Shape

6. Classification of Bones • Long bones • Typically longer than they are wide • Have a shaft with heads at both ends • Contain mostly compact bone • Found in limbs • Example: • Femur • Humerus • Tibia • Fibula

7. Classification of Bones • Short bones • Generally cube-shape • Contain mostly spongy bone • Example: • Carpals • Tarsals

8. Classification of Bones • Flat bones • Thin, flattened, and usually curved • Two thin layers of compact bone surround a layer of spongy bone • Example: • Skull • Ribs • Sternum

9. Classification of Bones • Irregular bones • Irregular shape • Do not fit into other bone classification categories • Example: • Vertebrae • Hip bones

10. Anatomy of a Long Bone • Diaphysis • A.K.A. Shaft • Composed of compact bone • Epiphysis • Ends of the long bone • Composed mostly of spongy bone

11. Anatomy of a Long Bone • Periosteum • Outside protective covering of the diaphysis • Fibrous connective tissue membrane • Sharpey’s fibers/Perforating fibers • Secure periosteum to underlying bone • Arteries • Supply bone cells with nutrients

12. Anatomy of a Long Bone • Articular cartilage • Covers the external surface of the epiphyses (ends of bones) • Made of hyaline cartilage • Decreases friction at joint surfaces • Epiphyseal plate (a.k.a. Growth Plate) • Flat plate of hyaline cartilage seen in young, growing bone • Epiphyseal line • Remnant of the epiphyseal plate • Seen in adult bones

13. Anatomy of a Long Bone • Medullary cavity • Cavity inside of the shaft • Contains yellow marrow (mostly fat) in adults • Storage area for adipose • Contains red marrow (for blood cell formation) in infants

14. Bone Markings • Surface features of bones • Sites of attachments for muscles, tendons, and ligaments • Passages for nerves and blood vessels • Categories of bone markings • Projections or processes—grow out from the bone surface • Terms begin with “T” • Depressions or cavities—indentations • Terms begin with “F” except FACET

15. Bone Markings

16. Bone Markings

17. Microscopic Anatomy of Bone • Osteon (Haversian system) • Occurs in compact bone • Contains capillaries and lamellae (think collection of concentric circles) • Central (Haversian) canal • Opening in the center of an osteon (vascular canal) • Carries blood vessels and nerves • Perforating (Volkman’s) canal • Canal perpendicular to the central canal • Carries blood vessels and nerves

18. Microscopic Anatomy of Bone

19. Microscopic Anatomy of Bone • Lacunae • Cavities containing bone cells (osteocytes) • Arranged in concentric rings • Lamellae • Rings around the central canal • Sites of lacunae

20. Microscopic Anatomy of Bone • Canaliculi • Tiny canals • Radiate from the central canal to lacunae • Form a transport system connecting all bone cells to a nutrient supply

21. Formation of the Human Skeleton • In embryos, the skeleton is primarily hyaline cartilage • During development, much of this cartilage is replaced by bone • This process is called “ossification” • Possible because of “osteoblasts” (bone forming cells) • Cartilage remains in isolated areas • Bridge of the nose • Parts of ribs • Joints

22. Bone Growth (Ossification) • Epiphysealplates (growth plate) allow for lengthwise growth of long bones during childhood • New cartilage is continuously formed • Older cartilage becomes ossified • Cartilage is broken down • Amedullarycavity is opened up/created • Bone replaces cartilage through the action of osteoblasts

23. Bone Growth (Ossification) • Bones are remodeled and lengthened until growth stops (i.e. growth plates close) • Bones are remodeled in response to two factors • Blood calcium levels • Pull of gravity and muscles on the skeleton • Bones grow in width (called appositional growth) • This depends if body increases in size/weight (i.e. weight gain/muscle hypertrophy)

24. Articularcartilage Hyalinecartilage Spongybone New center ofbone growth New boneforming Epiphysealplatecartilage Growthin bonewidth Medullarycavity Bone startingto replacecartilage Bloodvessels Growthin bonelength New boneforming Bone collar Epiphysealplate cartilage Hyalinecartilagemodel In an embryo In a fetus In a child (a) Long Bone Formation and Growth

25. Types of Bone Cells • Osteocytes—mature bone cells • Osteoblasts—bone-forming cells • Osteoclasts—bone-destroying cells • Break down bone matrix for remodeling and release of calcium in response to parathyroid hormone • Bone remodeling is performed by both osteoblasts and osteoclasts

26. Bone Fractures • Fracture—break in a bone • Types of bone fractures • Closed (simple) fracture—break that does not penetrate the skin • Open (compound) fracture—broken bone penetrates through the skin • Bone fractures are treated by reduction and immobilization

27. Bone Fracture Types

28. Hematoma Externalcallus Bonycallus ofspongybone Internalcallus(fibroustissue andcartilage) Newbloodvessels Healedfracture Spongybonetrabecula Bone remodeling Hematomaformation Fibrocartilagecallus formation Bony callusformation Repair of Bone Fractures Hematoma (blood-filled swelling) is formed Break is splinted by fibrocartilage to form a callus Fibrocartilage callus is replaced by a bony callus Bony callus is remodeled to form a permanent patch

29. The Axial Skeleton • Forms the longitudinal axis of the body • Divided into three parts • Skull • Vertebral column • Bony thorax

30. The Skull • Two sets of bones • Cranium • Facial bones • Bones are joined by sutures • Only the mandible is attached by a freely movable joint

31. Human Skull, Lateral View

32. Human Skull, Superior View

33. Human Skull, Inferior View

34. Human Skull, Anterior View

35. Paranasal Sinuses • Hollow portions of bones surrounding the nasal cavity • Functions of paranasal sinuses • Lighten the skull • Give resonance and amplification to voice

36. The Hyoid Bone • The only bone that does not articulate with another bone • Serves as a moveable base for the tongue • Aids in swallowing and speech

37. The Fetal Skull • The fetal skull is large compared to the infant’s total body length • Fontanels—fibrous membranes connecting the cranial bones • Allow the brain to grow • Convert to bone within 24 months after birth

38. The Vertebral Column • Each vertebrae is given a name according to its location (i.e. C-4, L-5) • There are 24 single vertebral bones separated by intervertebral discs • 7 cervical vertebrae are in the neck • 12 thoracic vertebrae are in the chest region • 5 lumbar vertebrae are associated with the lower back • 5 fused vertebrae form saccrum • 4 fused vertebrae form coccyx (a.k.a. tailbone) • Intervertebral discs • Discs made of fibrocartilage that provide the spine with cushion and absorb shock forces

39. The Vertebral Column

40. Postural Deviations of Vertebral Column

41. A Typical Vertebrae, Superior View

42. Cervical Vertebrae-Atlas & Axis

43. Cervical Vertebrae (C3-C7)

44. Thoracic Vertebrae (how many?)

45. Lumbar Vertebrae (how many?) Notice any differences in Lumbar vertebrae compared to the other types of vertebraes?

46. Sacrum and Coccyx What do you think these foramina are for?

47. Thorax • Made up of three parts • Sternum (where ribs articulate ventrally) • Ribs • True ribs (pairs 1–7) • Each rib attaches directly to sternum • False ribs (pairs 8–12) • Attach indirectly to sternum or don’t attach at all • Floating ribs (pairs 11–12) • Don’t have a sternum/sternal attachment • Thoracic vertebrae (where ribs articulate dorsally) • Function: Forms a cage to protect major organs

48. Thorax