1. Bones and Skeletal Tissues

2. Bones and Skeletal Tissues
Histology of cartilage and bone
Function of the skeletal system
Bone terminology
Bone development and growth

3. Cartilage: Hyaline cartilage (glassy)
Resilient tissue—it springs back to original shape
Hyaline cartilage (glassy)
Most abundant
Support through flexibility
Elastic cartilage—contains many elastic fibers
Tolerate repeated bending
Fibrocartilage—resists compression and tension
Intermediate between hyaline and elastic

4. Cartilage: Connective tissue
Chondroblasts lay down matrix, becoming chondrocytes when surrounded by EC matrix
Chondrocytes do not mitose resulting in poor healing
On aging, cartilage becomes calcified and less flexible

5. Tissues in Bone Dominated by bone CT
Bones contain several types of tissues
Dominated by bone CT
Contain nervous tissue and blood CT
Contain cartilage in articular cartilages
Contain ET lining blood vessels

6. Function of Bones Support Movement Protection Mineral storage
Blood-cell formation

7. Bone Tissue Bone tissue Organic components: Inorganic components:
cells & fibers
Inorganic components:
mineral salts that invade bony matrix

8. Extracellular Matrix
Gives bone exceptional properties: 35%—organic components
Contributes to flexibility and tensile strength
65%—inorganic components
Provide exceptional harness, resists compression

9. Three Types of Cells
Osteogenic cells: stem cells that differentiate into osteoblasts
Osteoblasts: actively produce and secrete bone matrix
Bone matrix is osteoid
Osteocytes: keep bone matrix healthy
Osteoclasts
Responsible for resorption of bone
Secrete hydrochloric acid and lysosomal enzymes

10. Classification of Bones
Long bones—longer than wide; a shaft plus ends
Short bones—roughly cube-shaped
Flat bones—thin and flattened, usually curved
Irregular bones—various shapes, do not fit into other categories

11. Classification of Bones

12. Compact bone—dense outer layer of bone
Gross Anatomy of Bones
Compact bone—dense outer layer of bone
Spongy (cancellous) bone—internal network of bone

13. Structure of Short, Irregular, and Flat Bones
Flat bones, short bones, and irregular bones
Contain bone marrow but no marrow cavity
Diploë
Internal spongy bone of flat bones
Spongy bone
(diploë)
Compact bone
Trabeculae
igure 6.5

15. Structure of a Typical Long Bone
Diaphysis—“shaft” of a bone
Epiphysis—ends of a bone
Blood vessels—well vascularized
Medullary cavity—hollow cavity filled with yellow marrow
Membranes
Periosteum, perforating fibers, and endosteum

16. Structure of a Long Bone
Articular cartilage
Compact bone
Proximal
epiphysis
Spongy bone
Endosteum
Epiphyseal
line
Endosteum
Periosteum
Compact bone
Medullary
cavity (lined
by endosteum)
(b)
Diaphysis
Yellow
bone marrow
Compact bone
Periosteum
Perforating
(Sharpey’s)
fibers
Nutrient
arteries
Distal
epiphysis
(a)
(c)
Figure 6.4a–c

19. 1. Compact Bone Osteoclasts break down bone
Osteon = functional unit of bone
Osteoblasts lay down the matrix in layers (lamellae)
Become osteocytes when surrounded by EC matrix
Lacunae
Osteoclasts break down bone

20. Microscopic Structure of Compact Bones
Contains passage ways for blood vessels, lymph vessels, and nerves
Osteons—long cylindrical structures
Function in support
Structurally—resembles rings of a tree in cross-section

21. Microscopic Structure of Compact Bones
Spongy bone
Perforating
(Volkmann’s)
canal
Central
(Haversian) canal
Endosteum lining
bony canals and
covering trabeculae
Osteon
(Haversian system)
Circumferential
lamellae
(a)
Perforating (Sharpey’s) fibers
Periosteal blood vessel
Lamellae
Periosteum ()
Nerve
Vein
Artery
Canaliculi
Osteocyte
in a lacuna
Lacunae
Lamellae
Central canal ()
Interstitial
lamellae
Lacunae
Lamellae
Central Canal
Lacuna (with
osteocyte)

22. 2. Spongy Bone
Lacy network of struts called trabeculae reinforce the bone
Covered by endosteum

23. Microscopic Structure of Spongy Bones
Is less complex than compact bone
Trabeculae contain layers of lamellae and osteocytes
Are too small to contain osteons

24. Microscopic Structure of Spongy Bones
Marrow
space
Trabecula
Osteocytes
Endosteum
(a)
Osteoblasts
(b)
Figure 6.9

25. 3. Marrow Red Marrow Yellow Marrow Active Blood Precursors Inactive
Mostly fat

26. Anatomy of Epiphyseal Growth Areas
In epiphyseal plates of growing bones:
Cartilage is organized for quick, efficient growth
Cartilage cells form tall stacks
Chondroblasts at the top of stacks divide quickly
Pushes the epiphysis away from the diaphysis
Lengthens entire long bone

28. Postnatal Growth of Endochondral Bones
As adolescence draws to an end:
Chondroblasts divide less often
Epiphyseal plates become thinner
Cartilage stops growing
Replaced by bone tissue
Long bones stop lengthening when diaphysis and epiphysis fuse

30. Bone Remodeling Bone is dynamic living tissue
500 mg of calcium may enter or leave the adult skeleton each day
Spongy bone of the skeleton is replaced every 3–4 years
Compact bone is replaced every 10 years

31. Osteoclast—A Bone-Degrading Cell
Crawls along bone surfaces
Breaks down bone tissue
Secretes concentrated HCl
Lysosomal enzymes released
Derived from hematopoietic stem cells

32. Fractures Young vs. old patients Simple vs. open (compound) fractures
Healing:
Reduction and stabilization
Formation of hematoma
Callus—
fibrocartilagenous and
bony
Remodeling—months later

33. Common Types of Fractures
Table 6.2 (1 of 3)

34. Common Types of Fractures

35. Common Types of Fractures
Table 6.2 (3 of 3)

36. Stages of Healing a Fracture
Hematoma
External
callus
Bony
callus of
spongy
bone
Internal
callus
(fibrous
tissue and
cartilage)
New
blood
vessels
Healed
fracture
Spongy
bone
trabecula 1
A hematoma forms. 2
Fibrocartilaginous
callus forms. 3
Bony callus forms. 4
Bone remodeling
occurs.
Figure 6.15

37. Osteoporosis
Figure 6.16

40. The End