Cartilage and bone physiology Smith Week 2

Question 1

what type of cells make up cartilage?

Answer 1

chondrocytes

Question 2

cartilage is structurally designed to do what 4 things?

Answer 2

1. withstand tension and compression
2. provide low friction surface at joints
3. provide support to soft tissue
4. provide a framework for long osteogenesis during development

Question 3

how is cartilage different from bone?

Answer 3

• more flexible
• avascular
• less organized structure
• no nerve fibers
• composed of up to 80% water

Question 4

how do nutrients get into the cartilage?

Answer 4

via perichondrium

Question 5

what is the perichondrium made of?

Answer 5

• fibrous connective tissue sheath
• type I collagen
• vascular supply
• chondrogenic cells
• no present in all types of cartilage

Question 6

what are the 3 types of cartilage in the body?

Answer 6

• Hyaline-along axial skeleton
• Fibrocartilage-meniscus, pubic symphisis, and intervertebral disks
• Elastic cartilage-external ear, and epiglottis

Question 7

fiber types in hyaline cartilage

Answer 7

type II collagen fibers only

Question 8

fiber types in fibrocartilage

Answer 8

type I and II collagen

Question 9

fiber types in elastic cartilage

Answer 9

elastic fibers, and type II collagen

Question 10

what does chondoitin sulfate, a proteoglycan, do in cartilage?

Answer 10

provides much of the resistance to compression via electrostatic repulsion
*loss of chondoitin leads to osteoarthritis *

Question 11

collagen II bound to proteoglycan aggregates made up of chondroitin sulfate linked to hyaluronic acid is what provides repulsion force in you cartilage? T/F

Answer 11

True

Question 12

hyaline cartilage

Answer 12

most widespread type of collage
weakest of the three types of collagen
looks like frosted glass
*has a perichondrium
*has spherical chondrocytes
*made of type II collagen
*no nerves or blood vessels

Question 13

Fibrocartilage

Answer 13

strongest of all the cartilages

• contains both type I and II collagen
• more fibers than cells
• lacks a perichondrium
• highly compressible
• menisici of knee, intervetebral discs, and pubic symphysis

Question 14

Elastic cartilage

Answer 14

resembles hyaline cartilage but is more springy

• contains collagen type II and elastic fibers
• has a perichondrium
• only found in external ear and epiglottis

Question 15

axial skeleton composition

Answer 15

skull, vertebrae, ribs and sternum

Question 16

five functions of bone

Answer 16

support
protection
assist in movement
mineral homeostasis
blood cell production

Question 17

Bone compared to cartilage

Answer 17

• both contain living cells with occupy cavities called lacunae
• contain a fibrous connective tissue covering
• bone is highly vascularized
• bone contains more collagen
• all bone growth is by apposition or by deposition on an already existing surface

Question 18

adult bone is composed lamellae and are arranged to form types of bone

Answer 18

compact or cortical-most of bone in body 80%

trabecular or spongy 20%

Question 19

what do osteoclasts do?

Answer 19

bone resorption(breakdown) by creating SEALING zones and in part lowers the pH which dissolves hydroxyapatite and collagen.

Question 20

do osteoblasts build or break down bone?

Answer 20

build

Question 21

Bone calcium is available from two reservoirs, what are they?

Answer 21

exchangeable and stable. Most is in the stable form and is released slowly where the exchangeable is readily available

Question 22

where are the four places we get calcium and phosphorus from?

Answer 22

bone, kidneys, GI and diet.

*most of the calcium and phosphate in the body is in the bone

Question 23

parathyroid hormone (PTH)

Answer 23

• secreted by chief cells of the parathyroid gland
• mobilizes calcium from bone and increases calcium in blood
• increases urinary phosphate excretion and *increases calcium reabsorption

Question 24

1,25-dihydroxycholecalciferol

aka calcitriol

Answer 24

is a steroid hormone formed from Vit. D n skin via the sun and successive hydroxylations in the liver and kidneys

• increases calcium absorption form the intestine
• increases calcium in bone

Question 25

Calcitonin

Answer 25

lowers the calcium in blood via

• inhibiting bone resorption(breakdown)
• inhibiting calcium absorption by the intestine
• stimulates osteoblastic activity in bones
• inhibits reabsorption of calcium in kidney
• secreted by the parafollicular cells in the thyroid gland

Question 26

regulatory feedback between Vit D and PTH

Answer 26

• PTH helps activate Vit D to 1,25-dihydroxycholecalciferol in kidney
• then it can down regulate PTH release

Question 27

osteopetrosis

Answer 27

osteoclasts are defective and unable to resorb bone, so osteoblasts operate unopposed. bone over growth

Question 28

osteoperosis

Answer 28

relative excess of osteoclast function results in loss of bone matrix and high risk of bone fractures.
two causes: age and bisphosphinates(inhibit osteoclast activity, preventing resorbtion and increasing mineral content of bone.