1. Osteology Study of bone structure and function Bones are organs
Organs are tissues working together
Bones are made up of osseous (bone) tissue, cartilage, connective tissue, cardiovascular tissue, adipose (fat) tissue, and nervous tissue

2. Structure of Bone Tissue
Each bone is a living organ made up of tissue
There are two types of bone tissue, which differ in their density
Compact bone – heavier; gives bones hardness and strength
Spongy bone - lighter, less dense

3. Functions of Bone Tissue
1. Support
Support soft tissues
Provide attachment sites for tendons of muscles
2. Protection
Cranium protects brain
Ribs protect heart and lungs
Pelvic girdle protects reproductive organs
3. Movement
Bones provide sites for muscle attachment
Bones and muscles work together to produce movement

4. Functions of Bone Tissue (continued)
4. Mineral Homeostasis
Bone stores 99% of body’s calcium
Normal calcium levels 9-11 mg/dl
When Ca+2 blood levels are low, Ca+2 is released from the bone
Blood Ca levels are maintained by two hormones:
Parathyroid hormone- if blood Ca levels are too low, PTH pulls Ca from the bone to increase blood Ca levels
Calcitonin- if blood Ca levels are too high, CT decreases blood Ca levels by depositing calcium into the bones

5. Functions of Bone Tissue (continued)
5. Hemopoiesis
Process of blood cell formation (red blood cells, white blood cells and platelets)
Takes place in red bone marrow
6. Triglyceride Storage
Fat is stored in yellow bone marrow
Red bone marrow is present at birth…it is gradually replaced by yellow marrow in adults

6. Parts of Long bones
1. Diaphysis – shaft of long bone; compact bone
2. Epiphysis- proximal and distal ends of long bones; spongy bone
3. Metaphysis-where diaphysis joins the epiphysis
Location of epiphyseal plate (growth plate)
Where bone replaces cartilage
4. Articular cartilage- covers the epiphysis
Forms joints
Reduces friction and absorbs shock

7. Parts of Long Bones (cont)
5. Periosteum - connective tissue
Covers the outer surface of the long bone
Important for growth and repair, thickens bone, attachment point for tendons
6. Medullary Cavity - hollow space in diaphysis
Contains yellow marrow
7. Endosteum - inner surface that lines the medullary cavity
Contains bone forming cells

8. Bone (Osseous)Tissue
Contains four types of cells suspended in a matrix that is 25% H2O, 25% protein, 50% mineral salts
1. Osteogenic cells – unspecialized stem cell
Undergo cell division
Mature into osteoblasts
Found in periosteum, endosteum & canals in bone that contain blood vessels
2. Osteoblasts – bone forming cells
Secrete collagen fibers for the matrix
Deposit calcium which makes bone hard (calcification)

9. Bone (Osseous) Tissue (cont)
3. Osteocytes - mature bone cells
Trapped in the matrix
Maintain cellular activity of bone tissue (exchange of nutrients with blood)
4. Osteoclasts – breaks down and reabsorbs bone
helps keep Ca and P in the blood stream at a constant level

10. Matrix Contains calcium carbonate & calcium phosphate
Also contains magnesium hydroxide, fluoride & sulfate (mineral salts)
Minerals are deposited in a framework of collagen fibers, which gives flexibility
Calcification – mineralization
The minerals crystallize and then harden to become bone

11. Two Types of Bone
1. Compact Bone – 80%
2. Spongy Bone – 20%

12. Compact Bone External layer of all bones Makes up most of diaphysis
Provides support & protection
Osteon – also known as Haversian system
Functional unit of compact bone
Allows nutrients and O2 to reach osteocytes
Removes waste

13. Structure of Compact Bone
1. Perforating Canals- where blood vessels and nerves enter
2. Central Canals- run longitudinally through bone
3. Concentric Lamellae- encircle the central canals
4. Lacunae- space on lamellae where osteocytes are trapped
5. Canaliculi- small channels; connect lacunae with each other and with central canals

14. Structure of Compact Bone (cont)
6. Circumferential lamellae – encircle the bone beneath the periosteum
7. periosteal vessel – what lets nutrients and blood get into the bone

15. Structure of Spongy Bone
Lightweight
Where hemopoiesis takes place
Does not have true osteons
Lamellae are arranged in trabeculae, which is a thin, irregular lattice of bone with red marrow found in the spaces
Osteocytes get nutrients and oxygen directly from blood in the medullary cavity

16. Effect of Exercise on Bone
Bones alter their strength in response to mechanical stress
When placed under stress, bone tissue adapts by becoming stronger through increased mineral salt deposits and production of collagen (the converse is also true…with no stress, bones become weaker)

17. Effects of Age on Bone Birth to Adolescence
More deposition than reabsorption
Bone building phase
Young Adults
Deposition equals reabsorption
Bone maintenance
Middle Age
More reabsorption than deposition
Bone loss

18. Reasons for Bone Loss
1. Demineralization -loss of calcium and other minerals from the bone matrix
Females – starts ~ age 30
Lose 8% bone mass every 10 years
Males – starts ~ age 60
Lose 3% bone mass every 10 years

19. Reasons for Bone Loss (cont)
2. Brittleness –results from a lowered rate of protein synthesis, which decreases the strength of bone
Decreased collagen production causes fractures, pain, stiffness, deformity, loss of height & teeth