1. Chapter 6
Bone Tissue

2. CLASSIFICATION OF BONE
Location
Axial
Appendicular

3. Axial vs Appendicular AXIAL
Location – forms the axis of the body: skull, vertebral column and rib cage
Function – protection of organs, support of body
APPENDICULAR
Location – upper and lower limbs; shoulder and hip girdles
Function – Locomotion and manipulate our environment

4. CLASSIFICATION OF BONE
Shape
e) Sesamoid –
patella (knee)
Wrist and ankle bones

5. FUNCTIONS OF BONE
Support
Protection
Movement
Storage
Hematopoiesis

6. BONE MARKINGS Depressions and Openings Fossa Fissure Foramen Meatus
Groove
Sinus
Function – allow nerves and blood vessels to pass through the bone

7. Foramen Round or oval opening through a bone
Base of skull to allow passage of spinal cord

8. Sinus Cavity within a bone Filled with air Lined with mucous membranes
Skull

9. Fossa Shallow basin like depression on the surface of a bone
Scapula (shoulder blade)

10. Meatus
Canal like passage
External opening to ear canal

11. BONE MARKINGS Projections for attachment of muscles/ligaments
Tuberosity
Crest
Trochanter
Epicondyle
Process

12. BONE MARKINGS
Projections that help to form joints
Head
Condyle
Ramus

13. Bone: External/Internal
Compact bone forms the outer shell of all bone and also the shafts in long bones.
Spongy bone is found at the expanded heads of long bones and fills most irregular bones.
Contains honey-comb of small needle-like or flat pieces called TRABECULAE; contains red and yellow bone marrow.

14. Histology of Compact Bone
Note Volkmann’s
Canals
Volkmann’s canals

15. GROSS ANATOMY OF LONG BONES

16. Gross Anatomy of Long Bone
Periosteum – shiny white double layer that covers external surface of the bone
Epiphysis – bone ends (proximal/distal)
Exterior - compact bone
Internal - spongy bone
Joint surface – thin layer of hyaline cartilage

17. GROSS ANATOMY of LONG BONE continued
Diaphysis – long axis of the bone shaft
Medullary cavity (central marrow cavity)
Contains red and yellow bone marrow
Hematopoetic (Red) – produces blood cells
Yellow contains fat in adults (at birth all marrow is red; with age more and more is converted to yellow
Endosteum – Covers the internal bone surfaces
- Delicate connective tissue
- Covers the trabeculae of spongy bone and lines the canals

18. Spongy Bone

19. Microscopic Anatomy of Compact Bone
Osteon – structural unit of compact bone
Lamella –concentric circles of bone tissues in the osteon
Haversian canal – runs vertically through the core of each osteon; contains small blood vessels and nerve fibers

20. Microscopic (cont.)
Volkmann’s canal – runs horizontally; connects blood and nerve supply of periosteum to the central canals
Osteocytes (bone cells) – found in the lacunae (cavities) at the junction of lamellae
Canaliculi – hairlike canals that connect lacunae to each other and the central canal
****Spongy bone has no osteons*****

21. Intramembranous Bone Formation
Bone develops from a fibrous membrane
Occurs in:
Flat bones of the skull
Clavicles

22. Membrane Ossification

23. Endochondral Ossification
Most common type: Occurs in all of the bones except the skull and clavicles.
Definition: Begins in the second month of fetal development
Uses hyaline cartilage “bones” formed earlier as models or patterns for bone construction.

24. Endochondral Ossification Steps
1 Bone collar forms around the model
2 Internal cartilage begins to break down
3 Spongy bone, arteries, veins, lymph vessels, nerves, red marrow, osteocytes develop in the medullary cavity
4 Cartilage in the diaphysis continues to ossify (turn into bone)
5 Ossification of epiphyses; cartilage remains ONLY at the junction of the diaphysis and epiphysis [epiphyseal (growth) plate], and on epiphyseal surface (articular hyaline cartilage)

25. Endochondral Ossification “Replacement Bone”

26. Epiphyseal Plate also known as Epiphyseal Line or Growth Plate

27. Hormonal Regulation of Bone Growth During Youth
During infancy and childhood, epiphyseal plate activity is stimulated by growth hormone
During puberty, testosterone and estrogens:
Initially promote adolescent growth spurts
Cause masculinization and feminization of specific parts of the skeleton
Later induce epiphyseal plate closure, ending longitudinal bone growth (age 18 F, 21 M)

28. Bone Remodeling Remodeling units – osteoblasts deposit bone
and osteoclasts resorb or breakdown bone at membrane surfaces
- Deposition is greater in early life, whereas resorption is greater in later life.

29. Bone Deposition
Occurs where bone is injured or added strength is needed
Requires a diet rich in:
protein,
vitamins C, D, and A
calcium, phosphorus, magnesium, and manganese

30. Bone Resorption Accomplished by osteoclasts
Resorption involves osteoclast secretion of:
Lysosomal enzymes that digest organic matrix
Acids that convert calcium salts into soluble forms
Broken down matrix is secreted into the blood

31. Control of Remodeling Two control loops regulate bone remodeling
Hormonal mechanism maintains calcium homeostasis in the blood
Mechanical and gravitational forces acting on the skeleton
Results in
Differences between individuals
Difference in amount of change that occurs in different bones of an individual

32. Mechanical Stress
Wolff’s law – a bone grows or remodels in response to the forces or demands placed upon it
Observations supporting Wolff’s law include
Long bones are thickest midway along the shaft (where bending stress is greatest)
Curved bones are thickest where they are most likely to buckle
Large, bony projections (e.g.,greater trochanter of femur) occur where heavy, active muscles attach

33. Response to Mechanical Stress
Figure 6.13

34. Hormonal Mechanism
Rising blood Ca2+ levels trigger the thyroid to release calcitonin
Calcitonin stimulates calcium salt deposit in bone
Falling blood Ca2+ levels signal the parathyroid glands to release PTH
PTH signals osteoclasts to degrade bone matrix and release Ca2+ into the blood

35. Hormonal Mechanism
Figure 6.12

36. Common Types of Fractures
Comminuted – bone fragments into three or more pieces; common in the elderly
Spiral – ragged break when bone is excessively twisted; common sports injury
Depressed – broken bone portion pressed inward; typical skull fracture; shaken baby syndrome; concussion
Compression – bone is crushed; common in porous bones
Greenstick – incomplete fracture where one side of the bone breaks and the other side bends; common in children

37. Common Types of Fractures
Table 6.2.2

38. Common Types of Fractures
Table 6.2.3

39. Common Types of Fractures
Table 6.2.1

40. Bone Repair

41. Homeostatic Imbalances
Osteoporosis
Group of diseases in which bone resorption outpaces bone deposit
Spongy bone of the spine is most vulnerable
Occurs most often in postmenopausal women
Bones become so fragile that sneezing or stepping off a curb can cause fractures

42. Osteoporosis: Treatment
Calcium and vitamin D supplements
Increased weight-bearing exercise
Hormone (estrogen) replacement therapy (HRT) slows bone loss
Quit smoking (reduces estrogen levels)

43. Science Applications
What bone features do forensic scientists use to identify skeletal remains?
What happens to bone density of astronauts in space? Cause/Prevention?