Download Anatomy and Physiology I – Fall 2014 The Skeletal System – Part 2

Anatomy and Physiology I – Fall 2014
The Skeletal System – Part 2
Physiology of Osseous Tissue
I.
Mineral Deposition – mineralization begins in fetal development
A.
B.
Why does bony tissue usually develop only in bone?
1.
Calcium phosphate crystals
2.
Inhibitors of crystallization
3.
Osteoblasts and crystallization
Ectopic calcification
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Arteriosclerosis
II.
Mineral Resorption – dissolves bone; release of minerals
A. Osteoclast activity and HCl
B.
III.
Osteoclasts and acid phosphatase
Calcium & Phosphate (PO4) Homeostasis – mineral/ion reservoir
A. PO4 – what contains it: blood acid:base imbalances
B.
Ca+2 - 99% Ca+2 in bones
Neurons, muscles, blood clotting, signaling
1.
Hypocalcemia
a.
Effects on nervous system
b.
Effects on muscles - spasms, tetany, suffocation
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2.
C.
c.
Effects on bone - rickets and osteomalacia
d.
Causes of hypocalcemia
a.
Low levels of vitamin D
b.
Underactive parathyroid glands
c.
Thyroid tumors
d.
Pregnancy/lactation
Hypercalcemia – effects on nervous/muscular systems
a.
Effects of the nervous system
Emotional disturbances, lethargy, depression
b.
Effects on muscles
Weakness, sluggishness, cardiac arrest
Hormonal Regulation of Ca+2 homeostasis
Calcitriol (vitamin D), parathyroid hormone, calcitonin,
estrogen/testosterone
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1.
Calcitriol
a.
Production (skin, liver, and kidney)
b.
Functions
1) Ion absorption
2)
2.
Stimulation of osteoclasts
Parathyroid Hormone and parathyroid gland
a.
Production of osteoclasts
b.
Ca+2 resorption
c.
Inhibits collagen synthesis
d.
Promotes excretion of PO4 by kidneys
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3.
Calcitonin and Thyroid
a.
Functions
1) Inhibits osteoclasts
2)
b.
4.
Osteoblasts
Role in children, adults, pregnant/lactating women
Estrogen
Source: Science Daily http://www.sciencedaily.com/releases/2011/04/110411163910.htm
How Estrogen Protects Bones - Mar. 25, 2007
Researchers at the University at Buffalo described how estradiol, the primary estrogen in
humans, aids in maintaining bone density, a function critical to avoiding osteoporosis. Estrogen
is essential for healthy bone. When production of estrogen is reduced, as occurs normally in
postmenopausal women or after exposure to radiation or chemotherapeutic drugs, bones
become brittle and break easily. Their study found that estradiol helps maintain bone density by
stopping activity of the enzyme caspase-3, which initiates apoptosis (programmed cell death) of
osteoblasts, bone cells that aid in growth/development of bones. Estrogens prevent bone loss
and bone fractures by preventing apoptosis in osteoblasts by inhibiting caspase-3 activity.
4.
Role of obesity in bone density
Effects of obesity on bone metabolism, Jay J Cao, Cao J. Orthopaedic Surgery and Res. 2011, 6:30
Obesity is traditionally viewed as beneficial to bone health due to the positive effect of mechanical
loading conferred by body weight on bone formation, despite being a risk factor for many other chronic
health disorders. Although body mass has a positive effect on bone formation, whether the mass derived
from obesity or excessive fat accumulation is beneficial to bone remains controversial. Underlining
relationships between obesity and bone are complex and continue to be an active research area.
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Recent data strongly support that fat accumulation is detrimental to bone mass. Obesity affects
bone metabolism through several mechanisms. Because both adipocytes and osteoblasts are derived
from a common stem cell, obesity may increase adipocyte differentiation and fat accumulation while
decreasing osteoblast differentiation and bone formation. Obesity is associated with chronic inflammation.
Increased proinflammatory messengers in obesity may promote osteoclast activity and bone resorption.
Furthermore, excessive secretion of leptin and/or decreased production of adiponectin by adipocytes in
obesity may affect bone formation/resorption by increasing proinflammatory messenger production. Highfat intake may also block intestinal Ca+2 absorption and decrease Ca+2 availability for bone formation.
Obesity and bone metabolism are interrelated. First, both osteoblasts and adipocytes (fat storing
cells) are derived from a common stem cell and agents that inhibit adipogenesis stimulate osteoblast
differentiation and agents that inhibit osteoblastogenesis increase adipogenesis. Second, decreased
bone marrow osteoblastogenesis during aging is usually accompanied by increased marrow
adipogenesis. Third, chronic use of steroid hormone, such as glucocorticoid, results in obesity and rapid
bone loss. Fourth, both obesity and osteoporosis are associated with increased production of
proinflammatory messengers.
BONE DISORDERS
I.
Fractures
A.
Several Types of Fractures
1.
Closed vs. open
2.
Complete vs. incomplete
3.
Comminuted
4.
Spiral
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II.
5.
Epiphyseal
6.
Colles
Other Bone Disorders
A. Osteoporosis
Breaks of femur, hips, distal forearm bones, compression
fractures of vertebrae
Who’s affected?
Estrogen and osteoclasts – covered above
Other factors – smoking; diabetes; diets low in Ca+2, protein,
vitamins C and D; genetics
Role of exercise
Supplemental calcitonin
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B.
Osteosarcoma (males between 10-25 years)
JOINTS (Articulations) – Chapter 8
Contact areas between bones
I.
Types
A. Sutures - fibrous connective tissue between skull bone
B.
Syndesmosis - sheet or bundle of dense connective tissue
(between tibia and fibula)
C.
Gomphosis – socket in which teeth fit
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D.
Synchondrosis –united by hyaline cartilage. Permanent
example = first rib and manubrium
E.
Symphysis – fibrocartilage pad – shock absorber. Pubic
symphysis; intervertebral discs
C.
Synovial Joints - diarthrosis (freely movable)
Articular cartilage, fibrous capsule, synovial fluid,
synovial membrane, ligaments
Types of Synovial Joints – see Table 8.1 and figure below
1.
Ball-and-socket joints – globular head with cupshaped cavity
Head of humerus or femur with glenoid cavity or
acetabulum
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2.
Condyloid joint – oval condyle into elliptical cavity
Metacarpals and phalanges
3.
Gliding joints – flat surfaces slide past each other
Joints between carpal/tarsal bones
4.
Hinge joints – convex and concave surfaces meet
Joints between phalanges; between olecranon
process and olecranon fossa in elbow
5.
Pivot joints – cylindrical surface rotates within ring
Proximal ulna and radius; atlas and dens of axis
6.
Saddle joints – both bones have convex and concave
regions
Trapezium and thumb metacarpal
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II.
Types of Joint Movements
A. Flexion – decreases angle of joint
Example:
B.
Extension – increases angle of joint
Example:
C.
Dorsiflexion
Example:
D.
Plantar flexion
Example:
E.
Rotation – spinning joint around another
Example:
F.
Circumduction – move part in circle
Example:
G.
Abduction – moves part away from midline
Example:
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H.
Adduction – moves part towards midline
Example:
I.
Supination
Example:
J.
Pronation
Example:
K.
Eversion
Example:
L.
Inversion
Example:
M.
Protraction – moves part forward
Example:
N.
Retraction – moves part backwards
Example:
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O.
Elevation – raising a part
Example:
P.
Depression – lowering a part
Example:
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