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Histology > Cartilage and Bones > Flashcards

Cartilage and Bones Flashcards

1
Q

What 3 functions is cartilage structurally designed to do?

A

-withstand tension & compression
-provides low friction surface at joints and
to provide support to soft tissue.
-Provide a framework for long bone osteogenesis (during development).

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2
Q

Functional difference between chondrocytes and chondroblasts

A
  • Chondroblasts produce new matrix until skeleton stops growing. They are ‘immature/undifferentiated’
  • Chondrocytes are found in groups in cavities called lacunae. They are ‘mature cells’ and are less active.
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3
Q

5 differences between cartilage and bone

A

Cartlage is:

  • More flexible
  • Avascular (less blood supply, thus heals very slowly)
  • Less organized structure
  • No nerve fibers
  • Composed of up to 80% water
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4
Q

How are nutrients provided to cartilage?

A

Via diffusion through the perichondrium

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5
Q

What is the perichondrium?

A

A fibrous connective tissue sheath that contains:

  • Type I collagen fibers
  • Vascular supply for collagen
  • Chondrogenic cells
  • perichondrium is NOT found in all cartilage types
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6
Q

Main difference between 3 different types of cartilage

A
  • cell distribution and number

- type of fiber in the matrix

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7
Q

What two main fibers are found in cartilage?

A

1) collagen fibers - stronger than steel fibers of the same size
- Thin fibers - hyaline cartilage
- Thick fibers - fibrocartilage
2) elastic fibers
- elastic cartilage

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8
Q

3 main components of cartilage

A

Cells, fibers, and ground substance

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9
Q

What does ground substance of cartilage consist of, and what is the main function?

A
  • contains water, glycosaminoglycans, glycoproteins, and proteoglycans
  • proteoglycans are aggregates of chondroitin sulfate and hyaluronic acid
  • functions to generate electrostatic repulsion and resist compression
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10
Q

What is caused by the loss of chondroitin sulfate in cartilage ground substance?

A

osteoarthritis

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11
Q

Explain proteoglycan repulsion

A

occurs between negative fixed charges on adjacent glycosaminoglycan molecules

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12
Q

Main functions of hyaline cartilage

A
  • absorbs mild compression, provides support, flexibility, and resilience
  • weakest of the 3 types of cartilage
  • most widespread type
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13
Q

simple composition of hyaline cartilage

A
  • has perichondrium
  • has spherical chondrocytes
  • type II collagen fibers
  • no nerves or blood vessels
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14
Q

4 hyaline cartilage locations

A
  • articular cartilages - end of long bones
  • costal cartilage - ribs/sternum
  • respiratory cartilage
  • nasal cartilage
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15
Q

What is ossification?

A

The process of hyaline cartilage turning into bone

-chondroblasts die and are replaced by osteoblasts in ossification centers

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16
Q

Characteristics of fibrocartilage

A
  • strongest type of cartilage
  • contains both type I and type II collagen
  • lacks perichondrium
  • highly compressible
  • located at sites subject to pressure & stretch
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17
Q

Characteristics of elastic cartilage

A
  • resembles hyaline cartilage, but more stringy
  • contains perichondrium
  • network of elastic fibers within matrix in addition to type II collagen fibers
  • found in external ear and epiglottis
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18
Q

5 functions of bone

A
  • support
  • protection
  • assisting movement
  • mineral homeostasis
  • blood cell production
19
Q

What 3 hormones regulate calcium homeostasis?

A
  • parathyroid hormone
  • 1,25-dihydroxycholecalciferol
  • calcitonin
20
Q

Characteristics of parathyroid hormone

A
  • secreted by chief cells of parathyroid glands
  • mobilizes calcium from bone
  • increases urinary phosphate excretion
21
Q

characteristics of 1,25-dihydroxycholecalciferol

A
  • formed from vit D in skin via sun, and from liver and kidneys
  • increases calcium absorption from intestine
  • increases calcium in bone
22
Q

characteristics of calcitonin

A
  • calcium lowering hormone secreted by parafollicular cells in thyroid gland
  • inhibits bone resorbtion
23
Q

Interaction of PTH and calcitonin

A
  • PTH increases blood levels of calcium when plasma levels get too low
  • calcitonin decreases blood levels of calcium when plasma levels get too high
24
Q

Regulatory feedback between vit D and PTH

A
  • PTH helps activate vit D to 1,25-dihydroxycholecalciferol in kidney
  • 1,25-dihydroxycholecalciferol can then downregulate PTH release
25
Q

What happens when calcium is too high in plasma? Too low?

A
  • Too high: calcitonin is secreted from parafollicular cells of thyroid to inhibit calcium reabsorbtion from bone
  • Too low: parathyroid chief cells release PTH to stimulate the reabsorbtion of calcium from bone into plasma, reabsorbtion in kidney, and activation of vit D
26
Q

What is the function of activated vit D with respect to calcium?

A

it increases calcium reuptake in the gut

*calcitriol feedback inhibits PTH release

27
Q

What cells secrete calcitonin, and from where?

A

parafolluclar cells of the thyroid

28
Q

Where are G-protein coupled receptors for calcitonin found?

A

bones (on osteoclasts) and kidneys

29
Q

In what 4 ways does calcitonin lower plasma calcium levels?

A
  • inhibits calcium absorption by the intestines
  • inhibits osteoclast activity in the bones
  • stimulates osteoblastic activity in bones
  • inhibits renal tubular cell reabsorption of calcium, allowing it to be excreted in the urine
30
Q

What 4 ‘other’ hormones impact calcium metabolism?

A
  • glucocorticoids
  • growth hormone
  • estrogens
  • insulin
31
Q

Effect of glucocorticoids on bone

A

-lowers plasma calcium levels by inhibiting osteoclast formation and activity

32
Q

Effect of growth hormone on bone

A
  • increases calcium excretion in urine

- increases intestinal absorption of calcium

33
Q

Effect of estrogens on bone

A

-prevents osteoporosis by inhibiting stimulatory effects of cytokines on osteoclasts

34
Q

Effect of insulin on bone

A
  • increases bone formation

* significant bone loss in untreated diabetes

35
Q

Rickets/Osteomalacia

A

-Rickets (children) and osteomalacia (adults) is caused by a defective bone matrix due to vit D and/or calcium deficiency

36
Q

What is osteopetrosis?

A
  • osteoclasts are defective and unable to absorb bone, so osteoblasts operate unopposed
  • bone density is increased and growth becomes distorted
37
Q

What is osteoporosis?

A
  • relative excess of osteoclast function results in loss of bone matrix and high risk of bone fractures
  • treatment using bisphosphonates to inhibit osteoclasts
38
Q

What disfiguring bone condition is associated with bisphosphonate?

A

Osteonecrosis of the jaw (ONJ)

39
Q

Compare bone & cartilage

A

BONE/CARTILAGE
osteocytes/chondrocytes
periosteum/perichondrium
vascularized/avascular

40
Q

How does bone grow?

A
  • Osteocytes are unable to divide

- All bone growth is by apposition - deposition of bone on preexisting surfaces

41
Q

Main protein found in bone matrix

A
  • type I collagen makes up over 90% of bone matrix

- type I collage is as strong as steel

42
Q

What are lamellae?

A
  • what adult bone is composed of

- 2 types of architecture: compact (cortical) bone and trabecular (spongy) bone

43
Q

Osteoclasts, osteoblasts, and osteocytes

A
  • Osteoclasts - bone resorption
  • Osteoblasts - bone formation
  • Osteocytes - mature bone cells
44
Q

Phosphorous homeostasis

A
  • 85% of the body’s phosphorous is stored in bone

- kidney regulates human phosphate homeostasis via excretion and reabsorption

Histology (5 decks)

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