Bone Structure & Development Flashcards
what is the effect of exercise on the skeletal system?
- bone health: build strong bones when one is young and maintain bone strength as you age
- reduce bone loss and improve bone mass
- flexibility: help keep joints as flexible as possible
-synovial fluid production: exercise can increase the production of synovial fluid
what is the effect of hormones on the skeletal system?
- bone growth:
- thyroxine stimulates cell metabolism and increases rate of osteoblast activity (produced in thyroid gland)
- growth hormone (GH) stimulates protein synthesis and cell growth throughout body (produced by pituitary gland
- bone maintenance: hormones control bone growth, maintain bone, and remodel it
- bone strength: sex hormones are important for maintaining the mass and strength of bone
- bone density: too much or too little of certain hormones can contribute to osteopenia and osteoperosis, which are conditions that make bones weak and likely to break
- bone remodeling: osteocytes sense mechanical strain and microcracks, respond to hormonal changes, and trigger bone remodeling
what is the effect of puberty on bone development and the skeletal system?
- increased sex hormones (estrogens and androgens) stimulate osteoblasts to produce bone faster than rate at which epiphyseal cartilage expands
- estrogen and androgen account for differences in male and female size and body proportions
- over time, epiphyseal cartilage narrows and closes
- timing differs from bone to bone and individual to individual (ie. toes may complete ossification by age 11, while pelvis continues to enlarge until 25)
- estrogen is faster at epiphyseal closure than androgens
- females generally shorter than males
what is the effect of nutrients on bone development and the skeletal system?
- body needs constant dietary sources of Ca and phosphate salts and lesser amounts of Mg, F, Fe, and Mn
- Calcitriol: essential for normal Ca and phosphate absorption
- produced in kidneys
- synthesized from Vitamin D3 produced in skin or absorbed from diet
- adequate levels of Vitamin C
- required as coenzyme in reactions of collagen synthesis
- stimulates osteoblast activity
- Vitamin A: stimulates osteoblast activity
- Vitamin K & B12: required for synthesis of proteins in bone
what are irregular bones?
complex-shaped bones with short, flat, notched surfaces
- seen in spinal vertebrae, bones of pelvis, ethmoid & sphenoid bones
what is the importance of calcium within the body, specifically as it relates to the skeletal system?
- most abundant mineral in the body
- 99% housed in bones and teeth
- plays a role in physiological processes such as:
- muscle contractions
- tight junctions
- hormone secretion
- blood clotting
- body has tight control over levels (usually within +/- 10%)
- 30% abv normal: neurons and muscle cells become unresponsive
- 35% below normal: neurons become too excitable resulting in convulsions
- 50% below normal: death
how does the body control [Ca2+] in the body?
- controlled by pair of hormones with opposing effects
- coordinate storage, absorption, and excretion of Ca2+
- calcitonin (thyroid)
- parathyroid (PTH - parathyroid gland)
- 3 target sites
- bones (storage)
- digestive tract (absorption)
- kidneys (excretion)
describe calcium homeostasis in bones
- bone is a major storage site for Ca2+
- movement of Ca2+ in and out of bone helps determine blood calcium levels (critical for normal muscle and NS functioning)
- calcium moves into bones as osteoblasts build new bone
- calcium moves out as osteoclasts break bone down
- blood Ca2+ levels regulated by hormones
what happens when blood calcium levels are too low?
- osteoclast activity increases
- calcium released by osteoclasts from bone into blood
- blood calcium levels are restored
what happens when blood calcium levels are too high?
- osteoclast activity decreases
- osteoblast activity increases
- calcium taken from blood by osteoblasts to produce new bone
- blood calcium levels decrease
what is calcitonin?
- secreted from thyroid gland
- inhibits osteoclast activity
- increases rate of excretion of Ca2+ at kidneys
- decreases blood Ca2+ levels
- increasing blood Ca2+ levels stimulates calcitonin secretion
what is PTH?
aka parathyroid hormone
- from parathyroid glands
- stimulates increased bone breakdown; increases blood Ca levels
- stimulates osteoclast activity
- increases Ca2+ reabsorption from urine in kidneys; decreases rate of excretion
- stimulates kidneys to form Vitamin D (also increases Ca2+ absorption in GI tract)
- decreasing blood Ca levels stimulates PTH secretion
how does aging effect the skeletal system?
articulation of skeletal system affected by years of use (and abuse)
- if not used, joints get stiff due to lack of synovial circulation
- decreases in ability to repair damage
- fractures easier
- exercise to maintain mobility
what is rheumatism?
general term indicating pain and stiffness of skeletal and/or muscular systems
what is arthritis?
encompasses all rheumatic diseases affecting synovial joints
- always involves damage to articular cartilages
- specific cause can vary: bacterial, viral, injury, metabolic, or severe physical stresses
what is osteoarthritis?
also known as DJD (degenerative joint disease)
- generally affects 60y/o+
- due to cumulative wear and tear at joint surfaces or genetic factors affecting collagen formation
- at 60+ yrs, 25% women/15% men show signs
- regular exercise, physical therapy, drugs reducing inflammation (aspirin) can slow progress
what is rheumatoid arthritis?
- inflammatory condition
- affects 0.5 - 1.0% of adult population
- some cases can be an autoimmune disease
- body attacks its own joint tissue due to allergies, bacteria, viruses, and/or genetic factors
what is osteopenia?
in adequate ossification
- part of natural aging process
- reduction in bone mass occurs btwn ages 30-40
- osteoblast activity begins to decline while osteoclast activity remains normal
- women lose abt 8% of skeletal mass/decade
- men lose 3%
- epiphyses, vertebrae, and jaws lose more mass than other sites
- results in fragile limbs, reduction in height, and loss of teeth
what is osteoporosis?
condition when reduction in bone mass leads to compromise in normal functioning
- hip can fracture due to standing
- over age 45: 29% of women and 18% of men have osteoporosis
- in women, condition accelerates after menopause due to decline in estrogen circulation
- men retain androgen levels until late in life
- develops as secondary effect w/ cancers which release osteoclast-activating factor
what is gigantism?
rare condition causing accelerated growth during childhood
- pituitary gland produces too much growth hormone (GH) before epiphyseal lines close
- results in longer appendages and tall stature
what is pituitary dwarfism?
inadequate production of GH leads to reduced epiphyseal cartilage activity and abnormally short bones
what is Marfan’s syndrome?
inherited/genetic metabolic condition resulting in excessive cartilage formation at epiphyseal cartilage
- affects the heart, eyes, blood vessels, and skeleton
- characterized by tall and thin (lanky) stature, with long arms, legs, fingers, and toes
