Skeletal System Overview

1. Skeletal System Overview Chapter 7 p. 192 – p. 204

2. What makes up bone? • Osteocytes (bone forming cells) and extracellular matrix • Osteocytes are found in lacunae (holes in the bony matrix) • Extracellular matrix is made up of collagen and inorganic salts (nonliving)

3. What tissues are associated with bone?

4. What tissues are associated with bone? Cartilage Dense connective tissue Blood Nervous tissue

5. Types of Bones Long bones Short bones Flat bones Irregular bones Sesamoid bones

6. Short Bones Make up hands and feet

7. Flat Bones Scapula (shoulder blade) Skull Ribs

8. Irregular Bones Vertebrae Facial bones

9. Sesamoid Bones Not always a separate category Round bones Patella

10. Long Bones • Epiphysis • Articular Cartilage • Diaphysis • Spongy bone • Compact bone

11. Parts of the Long Bone • Periosteum • Vascular, fibrous outer covering of bone • Endosteum • Lines medullary cavity • Contains bone forming cells • Medullary Cavity • Hollow region of bone • Continuous with the spongy bone • Marrow, blood vessels found here • Adults: yellow marrow

12. Spongy Bone • Trabeculae: branching bony plates • Space between the bony plates allows for cushion • Spongy bone is usually found at the ends of long bones • In adults: red marrow found here

13. Compact Bone • Made up of osteons • Circular units with central blood vessels and nerves • Also called Haversian systems • Resists compression • Run parallel with the diaphysis • Canaliculi connect osteocytes • Allow for the transport of nutrients and waste

14. Compact Bone • Made up of osteons • Circular units with central blood vessels and nerves • Also called Haversian systems • Resists compression • Run parallel with the diaphysis • Canaliculi connect osteocytes • Allow for the transport of nutrients and waste • Volkmann’s canals • Also known as perforating canals • Contain blood vessels and nerves • Communicate with surface of the bone • Run perpendicular to the diaphysis

15. Bone Marrow

17. Osteon

18. Volkmann’s Canals

19. Bone Development • Osteogenesis: development of bone • Intramembranous Bone (flat bones) • Unspecialized cells appear at site of new bone formation • Blood vessels move into these cells and allow cells to differentiate into osteoblasts • Deposit bony matrix to form spongy bone • Spongy bone would fill in with higher amounts of bony matrix to form compact bone

20. Bone Development • Endochondral Bones • Develop from masses of hyaline cartilage • Hyaline cartilage lays down basic bone layout • Over time, bone forms over the cartilage template • Osteoblasts form and secrete bony matrix • Once bony matrix surrounds the osteoblasts, they are called osteocytes • Endochondral ossification

21. Bone Development • Primary ossification center • Bone begins to replace hyaline cartilage in the diaphysis • Osteoblasts in periosteum deposit compact bone • Secondary ossification centers • Epiphyses • Spongy bone • Epiphyseal plate – zone of cartilage between diaphysis and epiphysis

22. Bone Development

23. Growth at the Epiphyseal Plate • 4 layers • Resting cartilage • No growth • Closest to the epiphysis • Proliferating cartilage • Young cells, mitosis • Zone of hypertrophic cartilage • Older cells • Zone of calcified cartilage • Dead cells and extracellular matrix

25. Osteoclasts • Invade areas of calcified cartilage • Break down extracellular matrix • Osteoblasts then move in • Deposit bony matrix in place of calcified cartilage

26. Ossification Timetable (p. 200)

27. Bones under the microscope

28. Stages of Human Bone Development

29. Infant • Less than one year old • Approximately 300 bones (small bones have not fused yet) • Skull much larger than body • Bones are not fused • Smaller pelvis

30. Toddler 1 – 2 years Begin teeth growth Ossification of bones

31. Youngster Ages 3 – 9 Bones complete fusion Cervical vertebrae thicken Lower jaw thickens Skull becomes rounder, less elongated Increase in teeth number Ribs ascend Pelvis broadens

32. Youth Ages 10 – 13 Angular jaw More teeth Longer neck Sacrum shorter Fibula separates farther from tibia

33. Adolescent / Young Adult Ages 14 – 25 pelvis wider at the top Rib cage elongates Vertebrae thicken Growth plates close

34. Adult • 26+ • Mature bones • Back curves • Sharp ridges on neck • Rough edges on bone • High amounts of deposits • Hip angle increases (more triangular) • Heel bone extends • Vertebrae begin to shrink

35. Adult with Osteoporosis Vertebrae shrink Pronounced curvature of the back Bone becomes brittle, breaks easily

36. Osteoporosis

37. Factors Effecting Bone Growth and Repair Nutrition Exposure to sunlight Hormones Physical exercise Work with a partner to research a factor effecting bone growth and it’s effect on development Look up a bone growth disorder, too. (Brief!)

38. Fractures Greenstick – incomplete, across bone (usually in developing bone) Fissured – incomplete, longitudinal Comminuted – complete, shatters the bone Transverse – complete, right angle to bone axis Oblique – at an angle other than a right angle Spiral – caused by excessive twisting of the bone Compound – bone breaks the skin

39. Fractures

40. Bone Repair Hematoma forms (blood released from vessels within the bone) Formation of spongy bone and fibrocartilage Bony callus Osteocytes, osteoblasts and osteoclasts

41. Functions of the Skeletal System • Support and Protection • Movement • Origin and insertion of muscle • Origin: immovable end of the muscle • Insertion: movable end – during contraction, insertion will move toward the origin

42. Functions of the Skeletal System • Blood production • Hematopoiesis • Bone marrow – long bones, spongy bone, larger canals of compact bone • Red marrow: produces red blood cells, white blood cells and platelets • White marrow: fatty tissue

43. Functions of the Skeletal System • Inorganic salt storage • Salts account for approximately 70% of extracellular matrix of bone • Mostly calcium phosphate – hydroxyapatite • Also: magnesium, sodium, potassium, carbonate ions • Will also absorb small amounts of harmful metallic elements (lead, strontium)