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
Compact Bone

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
Compact Bone

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)
Age
Occurrence
3rd month of prenatal development
Ossification of long bones begins
4th month of prenatal development
Primary ossification centers are present in long bones
Birth to 5 years
Secondary ossification centers present
F: 5-12 years; M: 5-14 years
Ossification rapid through ossification centers
F: years; M: years
Bones of upper limb/scapulae completely ossified
F: years; M: years
Lower limbs and hips completely ossified
F: years; M: years
Sternum, clavicles, vertebrae completely ossified
F: by 23; M: by 25
Nearly all bones are completely ossified

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)