1. Bones and Skeletal Tissues

2. Major Function of Bones
Support – form the framework that supports the body and cradles soft organs.
Protection – provide a protective case for the brain, spinal cord, and vital organs.
Movement – provide levers for muscles.
Mineral storage – reservoir for minerals especially calcium and phosphorus
that can be released into the blood if the body needs them.
Blood cell formation – hematopoiesis occurs within the marrow cavities of bones

3. Minor Functions of Bones
Acid/Base Balance: Absorbs or releases alkaline mineral salts if blood pH changes drastically.
Detoxification: Helps remove heavy metals and foreign elements from the blood to protect other vitals organs.
It will try to release them slowly to prevent excessive stress on the kidneys who must excrete them.

4. Bone: Cell Types
Bone is considered connective tissue that contains several types of cells make it capable of adapting and changing according to stresses placed on it.
Osteoblast (build): Produced by osteogenic cells if there is an increase in stress or fracture to the bone.
They lay down building blocks of bone matrix (collagen and glycoaminoglycans) ( GAGs). This plays an important role in mineralization of bone.
Osteocyte: As the osteoblast deposit matrix they become trapped in lacunae. They stop producing matrix and assume a role in maintaining calcium and phosphate balance between bone and blood.

5. Bone: Cell Types
Osteoclast: (Break) break down bone matrix by secreting acids and enzymes . Components of the matrix mainly Calcium and Phosphorus are released in the blood.
Osteoid – unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

6. Bone Membranes Periosteum – double-layered protective membrane
Outer fibrous layer is dense regular connective tissue
Inner osteogenic layer is composed of osteoblasts and osteoclasts
Richly supplied with nerve fibers, blood, and lymphatic vessels, which enter the bone via nutrient foramina
Endosteum – delicate membrane covering internal surfaces of bone

7. Microscopic Structure of Bone: Compact Bone
Figure 6.6a, b

8. Gross Anatomy of Compact Bone
dense and heavy bone designed for compressive forces
Haversian system, or osteon – the structural unit of compact bone
Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen
Haversian, or central canal – central channel containing blood vessels and nerves
Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal
Canaliculi – hairlike canals that connect lacunae to each other and the central canal

9. Microscopic View of Compact Bone

10. Histology of Compact Bone

11. Structure of Spongy Bone
Trabeculae: Light weight porous bone that’s arrangement is aligned to the stresses placed on them.
part of the bone that weakens and fractures with osteoporosis.
Red bone marrow is found within the trabeculae cavities

12. Structure of Long Bones

13. Structure of Long Bone

14. Red Marrow In infants In adults
Found in the medullary cavity and all areas of spongy bone
In adults
Found in the diploë of flat bones, and the head of the femur and humerus

15. The Skeleton The human adult skeleton has 206 bones.
Axial skeleton – bones of the skull, vertebral column, and rib cage
Appendicular skeleton – bones of the upper and lower limbs, shoulder, and hip

16. Shapes of Bones

17. Response to Mechanical Stress
Trabeculae form along lines of stress
Large, bony projections occur where heavy, active muscles attach

18. Remodeling of Bone
Mechanical and gravitational forces acting on the skeleton influence bone remodeling.
Less stimulation on bone increases osteoclasts activity resulting in the resorption of bone matrix which:
Demineralization of bone
releases the calcium and phosphate into the blood
Increasing stress levels stimulate of osteoblasts resulting in the deposition of bone matrix which:
removes calcium and phosphate from the blood
increases bone density
Hormonal mechanism maintains calcium homeostasis in the blood

19. 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

20. Hormonal Mechanism

21. Response to 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
Who will have a higher bone density.
A 32 year old astronaut how has been in space for 6 months.
A 55 year old active female
An 18 year old female who has been paralyzed from the waist down for 6 months.

22. Osteoporosis
In premenopausal women the hormone Estrogen has a protective effect on the bone by increasing osteoblastic activity and limiting osteoclastic activity.
When levels of estrogen drop( menopause) there is a shift is towards osteoclastic. This weakening of the bone leads to a condition called Osteoporosis.
It is critical to consume most of your dietary calcium between the years of
This is when you deposit most of the calcium that will protect your bone for the rest of your life.

23. Osteoporosis
The spongy bone in the thoracic spine is very susceptible to osteoporosis.

24. Female Athlete Triad Disordered eating:
Energy output is greater than energy input.
Loss of menstrual period (Amenorrhea)
Females who loose to much weight or have a body fat percentage less than 12% often experience hormonal irregularities secondary to inhibition of hypothalamic function.
Osteoporosis
The hypothalamus is needed to produce estrogen which has important for bone health.
The lack of this hormone leads to the premature weakening of bones.
Stress fractures in the young is a red flag !

25. Table 6.2.1

26. Table 6.2.2

27. Common Types of Fractures
Table 6.2.3

28. Joints and Their Classification
Arthrology = study of the joints
Kinesiology = study of musculoskeletal movement
Classified by freedom of movement
diarthrosis (freely movable)
amphiarthrosis (slightly movable)
synarthrosis (little or no movement)
Classified how adjacent bones are joined
fibrous, cartilaginous, bony or synovial

29. Fibrous Joint -- Sutures
Immovable fibrous joints
bind skull bones together
Considered a synarthrosis

30. Fibrous Joint -- Syndesmosis
Two bones bound by ligament only
interosseus membrane
Most movable of fibrous joints
Amphiarthrosis
Interosseus membranes unite radius to ulna and tibia to fibula

31. Cartilaginous Joint -- Symphysis
2 bones joined by fibrocartilage
pubic symphysis and intervertebral discs
Only slight amount of movement is possible
Amphiarthrosis

32. General Anatomy of Synovial Joint
Articular capsule encloses joint cavity
continuous with periosteum
lined by synovial membrane
Synovial fluid = slippery fluid; feeds cartilages
Articular cartilage = hyaline cartilage covering the joint surfaces
Articular discs and menisci
jaw, wrist, sternoclavicular and knee joints
absorbs shock, guides bone movements and distributes forces
Tendon attaches muscle to bone
Ligament attaches bone to bone

33. Synovial Joint
Joint in which two bones are separated by a space called a joint cavity
Most are freely movable
diarthrosis

34. Tendon Sheaths and Bursae
Bursa = saclike extension of joint capsule
between nearby structures so slide more easily past each other
Tendon sheaths = cylinders of connective tissue lined with synovial membrane and wrapped around a tendon

35. Types of Synovial Joints

36. Arthritis Arthritis ( Arthro= Joint) itis =inflammation
Osteoarthritis results from years of joint wear
articular cartilage softens and degenerates
accompanied by crackling sounds called crepitus
bone spurs develop on exposed bone tissue causing pain

37. What Joint is this? Which has Arthritis?

38. Osteoarthritis

39. Total Hip Replacement.

40. Arthritis and Artificial Joints
Rheumatoid arthritis is autoimmune attack on joint
antibodies attack synovial membrane, enzymes in synovial fluid degrade the cartilage, bones ossify
remissions occur, steroids and aspirin control inflammation
Arthroplasty is replacement of diseased joint with artificial device called prosthesis

41. Rheumatoid Arthritis