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Mammalian Physiology > Slide 10 > Flashcards

Slide 10 Flashcards

1
Q

What are the 4 types of bone structures?

A

long bones [leg ones]
short bones [like connecting one]
irregular bones
flat bone

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2
Q

What is the composition of bone?

A

compact bone on the outside = dense and supports well
solid and dense in appearance

spongy bone/trabecular bone on the inside = calcified lattice
needle like structure/space filled

epiphysis = end of long bone
epiphyseal plate = site of bone growth
diaphysis = shaft of long bone [hollow]

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3
Q

Define the composition of the diaphysis

A

main shaft of long bone
hollow, cylindrical, mostly compact bone/thick
provide strong support without too much weight (since hollow)

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4
Q

Define the composition and function of the epiphysis

A

present at both ends of the long bone
composed of cancellous bone filled with marrow
provides attachment for muscles and stabilizes joints

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5
Q

What is the articular cartilage? What is hyaline cartilage?

A 
layer of hyaline cartilage that covers the articular surface of epiphyses 
most outer (exterior) part of the epiphysis

hyaline cartilage: elastic cartilage that cushions jolts so impact does not go on bone directly but absorbed by the hyaline cartilage first

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6
Q

What are the layers of bone from the exterior to interior (2)

A

periosteum

endosteum

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7
Q

What is the periosteum?

A

dense, white, fibrous membrane that covers the bone

attaches to the tendons firmly to bones
contains cells that form and destroy bones
contains blood vessels important in growth and repair
contains blood vessels that send branches into bone
essential for bone cell survival and bone formation

basically on the exterior of bone

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8
Q

periosteum

A

outside
attachment
have blood vessel - vascularization
form and destroy bone units

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9
Q

What is the endosteum for?

A

thin epithelial membrane that lines the medullary cavity

medullary or marrow cavity: hollow/tube/in the diaphysis/ filled with yellow marrow in adult

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10
Q

What is bone composition in short, flat and irregular bones?

A

inner portion is cancellous covered with compact bone

space inside cancellous bones of irregular and flat bones are sometimes filled with red marrow

large amounts of red bone marrow are found in flat bones like ribs, pelvis and skull

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11
Q

What is the composition of the extracellular matric of bone? the organic and inorganic component

A

organic: secreted by bone cells [osteoblasts derived from mesenchymal stem cells] get imprisoned in the matrix
ground substance: collagenous fibers and a mix of protein and polysaccharaides forms gelatinous material

it is important in bone growth, repair and remodelling since it acts as a medium for the diffusion of nutrients, oxygen and metabolic waste

ground substance+calcium = bone rigidity

inorganic;
salts, deposition of hydroxyapatite: contributes to hardness of bones and have crystals of calcium and phosphate
calcium carbonate
resist stress and mechanical deformation
magnesium and sodium are also found in bone

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12
Q

How do you get rigid bones?

A

ground substance +calcium

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13
Q

What are the four major structures of each osteon?

A

(tree rings)
lamella: each ring, calcified matrix altered by growth

lacunae: small space containing tissue fluid where osteocytes are located between hard layers [the outermost ring layer of the osteon]
canaculi: ultrasmall canals from the osteocyte and connecting them to each other between lacunae

haversian canal: the centre of the osteon contains blood vessels and lymphatic vessels

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14
Q

What is the structure of cancellous bone?

A

there are NO OSTEONs but trabeculae needled like bony spicules

nutrients and waste are delivered and removed by diffusion through tiny canaliculi =located on the lines of stress to enhance bone strength

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15
Q

What is the most common difference between cancellous and compact bone?

A

cancellous: between compact bone common in flat bone, on the inner surface of long bone

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16
Q

What are the 4 types of bone cells?

A

osteogenic cells: differenciate and develop into osteoblasts

osteoblasts: synthesize and secrete collagen in matrix and become trapped in the matric when it calcifies turning to osteocyte
osteoclasts: stem form macrophages [not osteogenic cells]

17
Q

How do osteoblasts and osteoclasts differ?

A

blasts: deposit calcium and make new bone matrix
clasts: break down bone during bone resorption

18
Q

Define the osteoclasts.

A

giant multinucleated cells
responsible for bone erosion
developed from stem cells in the bone marrow
attach to bone surface by integrins

have large numbers of mitochondria and lysozyme to breakdown macromolecules

brings about resorption of bone by secreting:
collagenase,
matric metalloproteinase, (destroy ECM such as collagen)
and secretion of lactic and citric acids

19
Q

Define osteocytes.

A

translated osteoblast that is (matured) trapped in the surrounding calfiied bone matric
final differentiation state for an osteoblast

20
Q

How do osteoclast reshape a bone while osteoblasts lay down new ECM on underlying surface?

A

formation of bone tissues continue throughout life even after growth stops

bone formation and reasboprtion balance each other

21
Q

How do osteoblast induce osteoclast differentiation?

A

RANKL is on surface of osteoBLAST = binds to receptor RANK on osteaCLAST precursor cell

leads to differentiation of osteoclast precursor cells and activation of osteoclast resobption of bone

stimulators: parathyroid horone [released from thyroid to trigger Ca release]
inhibitors: estrogen acting via osteoprotegrin = OPG binds and competively inhibits RANKL to bnid to RANK receptor so there is less resorption and osteoclast differentiation

22
Q

How and why do we need to regulate calcium?

A

bones: store calcium/reserves

maintain and modulate blood calcium levels

calcium is mobilized and moves in and out of blood during remodelling

formation: Ca removed by osteoblast from blood to deposit in bone
breakdown: osteoclast release calcium into blood and increase circulating levels

controlled by parathyroid hormone, calcitonin and vitamin D

Why?

need positive balance of calcium = for bone growth

adults= usually zero balance

don’t want osteoporosis = negative balance [postmenopausal women]

23
Q

How does parathyroid hormone regulate Ca?

A

when plasma is low in Ca

  • mobilize Ca from bone
  • enhances reabsorption of calcium in kidneys
  • stimulates release of calcitriol (increases intestinal calcium absorption into blood)
24
Q

What is calcitriol?

A

increases intestinal calcium absorption

stimulated release by parathyroid hormone

25
Q

How does calcitonin act to lower blood calcium?

A

opposes PTH

produces when high blood calcium levels

calcitonin released in plasma

  • decreases bone resorption
  • increases renal calcium excretion
26
Q

How does vit D (calcitriol) reglate calcium?

A

absorbed by small intestine as part of the diet or synthesized from UV exposure converting the light to vit D

precursor travels to liver and kidneys via blood

vit D:
increases calcium reabsorption in proximal and distal convoluted tubules of kidney

stimulates osteoblast activity to increase bone mass and calcification

intestine increases synthesis of calcium binding proteins on intestinal cells

disorders of vit D can cause weka bones because less calcium absorption

27
Q

How can we have calcification?

A

laying down calcium salts [calcium and phosphorus]

28
Q

What is the general development of bone osteogenesis?

A

skeleton forms in a fetus = cartilage

cartilage replaced by calcified bone matrix

constant remodelling and growing bone changes cartilage to adult bone = constant activity by osteoblast and osteoclasts

calcification by laying down calcium salts (deposits)

adult bone sculpting allows bones to respond to stress/injury by changing size and shape and density

exercise stimulates osteoblasts to secrete more collagen which makes bone stronger

29
Q

What are the two mechanism of bone formation?

A

intramembranous

endochondral

30
Q

What is the intramembranous way?

A

fibrous membranes replaced by bone tissue

  • does not begin as cartilage
  • starts as dense areas of mesenchymal cells [multipotent stem cells] that differentiate and begin to lay down bone around themselves = forms early spicules
  1. spongy bone tissue begins to develop at sites in membrane = centers of ossification
    - occurs in connective tissue membrane
    - migration of mesenchymal stem cells to the site of bone formation an differentiate into osteoblasts and then cluster to make centers of ossification
    - osteoblasts secrete matrix material and collagenous fibrils (ground substance)
    - mineralization occurs where organic strands once mineralized are called trabecula
  2. red bone marrow forms within spongy bone tissue followed by formation of compact bone outside
31
Q

How does bone develop through the endochondral development?

A

begins as cartilage with bone formation from centre to the end

  • mesenchymal stem cell migrate to site of eventual bone development
  • become chrondocytes=cartilage cells
  • differentiate into dense avascular mass
  • cartilage forms in the shape of bone
  • cartilage is surrounded by periosteum
  • osteoblasts differentiate from inner surface of periosteum to make a collar bone
  • primary ossification centre forms
  • blood vessel enters the cartilage at midpoint of diaphysis
  • bone grows LENGTHwise = elongates as cartilage/chrondrocytes
  • more cell division produces a new epiphyseal plate
  • at the other epiphyseal end, older cartilage is broken down by invading osteoclasts which is replaced by the expandin medullary cavity
32
Q

What are the four layers of the epiphyseal plate?

A

zone of proliferaition = cartilage cells/chrondrocytes undergo active mitosis

zone of hypertrophy: older, enlarged cells undergoing degenerative changes associated with calcium deposition

zone of calcification: dead or dying cartilage cells under rapid calcification

ossification zone: matric undergoes calcification

33
Q

What is a centre of ossification?

A

where spongy bone tissue begins to develop at the sites within membrane

34
Q

What are mesenchymal cells?

A

multipotent stem cells differentiate and being to lay down bone

35
Q

When do the epiphyseal plates fuse?

A

around puberty

they remain between diaphysis and each epiphysis until bone growth in length is complete

36
Q

How does the epiphyseal plates closing vary?

A

they enlarge and increase in length until puberty

closing varies based on:

  • bone type
  • person (male/female)
37
Q

What are the processes of appositional bone growth?

A

occurs in parallel to the growing bone length

periosteum cells develop into osteoblasts = produce more matrix on outer surface of bone

osteoclasts erode the inner surface to enlarge the marrow cavity

Mammalian Physiology (17 decks)

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