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Bioscience 2 > Skeletal System > Flashcards

Skeletal System Flashcards

1
Q

What do osteoprogenitor cells do?

A

Found in endosteal and periosteal membranes, differentiate into osteoblasts.

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2
Q

What do osteoblasts do?

A

Modified fibroblasts that synthesize and secrete organic matrix, calcify matrix.

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3
Q

What do osteocytes do?

A

Mature bone cells that transfer minerals from interior to growth surfaces.

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4
Q

What do osteoclasts do?

A

Form from monocytes, act to resorp bone and release Ca+2 and phosphate

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5
Q

What is bone’s organic matrix comprised of?

A
  • Proteoglycans
  • Glycoproteins
  • Type 1 collagen
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6
Q

What makes up the inorganic component of bone?

A
  • calcium phosphates
  • calcium fluoride
  • calcium hydroxide
  • calcium carbonate (secreted by osteoblasts)
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7
Q

What is the functional unit of bone?

A

Osteon

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8
Q

What is the makeup of an osteon?

A

-Concentric lamellae of osteocytes (which sit in lacunae filled with ECF) connected by cannaliculi

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9
Q

How do nutrients and wastes get into and out of osteocytes?

A
  • Cannaliculi transfer nutrients and wastes between blood vessels and osteocytes
  • Haversian canals and Volkmanns canals
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10
Q

What is the difference between haversian canals and volkmann’s canals?

A
  • Haversian canals run the length of long bones whereas volkmann’s canals run across them.
  • Volkmann’s canals join Haversian canals.
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11
Q

Where is cortical bone typically found?

A

Outer surface of bone

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12
Q

Where is spongey (trabeccular/canellous) bone usually found?

A

Inner bone

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13
Q

What are the five steps of bone formation?

A

1) Formation of bone collar around hyaline cartilage
2) Cavitation of hyaline cartilage
3) Invasion of periosteal bud
4) Continuation of ossification
5) Ossification of epiphyseal plate

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14
Q

What vitamins are needed for bone growth?

A
  • C
  • D
  • Calcium
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15
Q

What hormones are needed for bone growth?

A
  • Growth Hormone (leads to IGF-1 secretion)
  • Insulin
  • Thyroid Hormone
  • Androgens
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16
Q

Where does Membranous ossification occur?

A

-Flat bones

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17
Q

How does membranous ossification occur?

A

-mesenchymal cells turn right into bone: osteoprogenitors->osteoblasts->bone

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18
Q

Tell the bone remodeling story

A
  • Osteoclasts express RANK receptor
  • Osteoblasts express the protein RANKL
  • Osteoblasts also secrete osteoprotegrin, which inhibits RANKL
  • Osteoblasts secrete RANKL activates Osteoclasts, and this provides a normal Blast/Clast balance.
  • Up until menopause, RANKL
19
Q

How much of the body’s calcium is stored in the bones?

A

-99%

20
Q

T/F Calcium does not normally move between bone and plasma

A

FALSE. In a healthy body, calcium moves freely between plasma and bone.

21
Q

T/F Calcium is the most abundant mineral in the body

A

True. 1100gm.

22
Q

T/F Maybe 1% of calcium is free floating in plasma and blood

A

True

23
Q

How much intracellular calcium is free?

A

45-50%

24
Q

How much intracellular calcium is bound to albumin?

A

40-45%

25
Q

What does free calcium play a role in and how?

A

Acts as a second messenger important in…

  • Blood clotting
  • Muscle contraction
  • Nerve signal transmission
26
Q

What hormones are involved with calcium homeostasis?

A
  • Parathyroid hormone
  • Calcitonin
  • Vitamin D
27
Q

What systems are involved in calcium homeostasis?

A
  • The kidneys

- GI System

28
Q

How is phosphate homeostasis related to calcium homeostasis?

A
  • Phosphate is important aspect of ATP. Is less regulated than calcium and fluctuates easily with diet.
  • Regulated by same hormones as calcium, but responds in opposite ways (i.e. calcium goes up, phosphate goes down.)
29
Q

How does parathyroid hormone regulate calcium?

A

-Calcium receptors on parathyroid gland secrete a normal concentration of parathyroid hormone when calcium levels are normal, increased levels when calcium is low, and decreased levels when calcium is high.

30
Q

What three organs does parathyroid hormone impact?

A
  • Bone
  • Kidneys
  • GI Tract
31
Q

How does PTH impact bone?

A
  • PTH binds to osteoblasts, causing differentiation and activity of osteoclasts.
  • Causes increased osteoclast activity, which breaks down bone and increased blood /plasma levels of calcium AND phosphate.
32
Q

How does PTH impact the kidneys?

A
  • Increases calcium reabsorption and decreases calcium secretion
  • Decreased phosphate reabsorption and increased phosphate excretion
33
Q

How does PTH impact the GI Tract?

A
  • The GI tract actively regulates calcium and iron absorption.
  • PTH does not impact the small intestine actively, but rather promotes the synthesis of ACTIVE VITAMIN D to increase calcium absorption.
34
Q

How does calcitonin impact calcium?

A
  • Calcitonin is secreted by parafollicular cells of the thyroid gland
  • High plasma calcium concentration (indicative of bone breakdown) is the stimulus for release
  • Calcitonin inibits release of calcium from bone.
  • Reduces the reabsorption of calcium and phosphate at the kidneys.
  • Less impactful than PTH
35
Q

Where is vitamin D found?

A

Inactive form found in dietary sources such as fish liver oils, fatty fish, eggs, leafy greens.

36
Q

How is vitamin D activated?

A

Hydroxylation at the liver and the nat the kidneys.

37
Q

What is the action of vitamin D?

A
  • Acts on epithelial cells in the cut as a steroid hormone.
  • Alters gene transcription in cells, stimulating the cells to produce stuff that makes cells better at absorbing calcium across GI epithelium.
  • Enhances reabsorption of calcium at kidneys
  • Needed for normal calcification of bone matrix
38
Q

What are the effects of disturbances in calcium balance?

A

-Alters smooth and skeletal muscle contractions.

39
Q

What are the effects of hypocalcemia?

A

-Increased neuronal excitement and neuromuscular excitability

  • Seizures
  • Fatigue
  • Anxiety.
  • Chronic skin problems
  • Paresthesia of hands and feet.
  • Perioral tingling
  • Laryngospasm, bronchospasm, wheezing.
  • Carpopedal spasm.
40
Q

What is chvostek’s sign?

A

Result of hypocalcemia, tapping over the facial nerve anterior to the ear elicits twitch in ipsilateral face muscles.

41
Q

What is trousseaus sign?

A

-Inflation of BP Cuff elects carpal spasm.

42
Q

What are the signs of hypercalcemia?

A
  • Depressed Neuronal excitability
  • Can be acute and cause GI problems (anorexia, nausea), renal issues (polyuria, polydipsia) , neuromuscular issues (depression, confusion/stupor, coma), or cardiac issues (bradycardia, first degree AV block)
43
Q

What are the chronic signs of hypercalcemia?

A
  • Constipation, pancreatitis,
  • Kidney stones
  • Generalized weakness

Bioscience 2 (10 decks)

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