Bone Histology Flashcards
bone is a connective tissues characterised by what type of extracellular matrix? [1]
bone is a connective tissues characterised by what type of extracellular matrix? [1]
- mineralised ECM
what is the main mineral in the mineralised ECM in bones? [1]
what other subtstance is mostly found in the bone matrix [1]?
what is the main mineral in the mineralised ECM in bones? [1]
calcium phosphate
what other subtstance is mostly found in the bone matrix [1]?
type 1 collagen - 90% of bone
what are spaces found in bone matrix called? [1]
what connects the spaces found in bone matrix? [1]
what is name of bone cell found here ^? [1]
what are the other 4 type of cells found in bone [4]
what are spaces found in bone matrix called? [1]
lacunae
what connects the spaces found in bone matrix? [1]
canaliculi connect lacunae
what is name of bone cell found here ^? [1]
osteocyte
what are the other 4 type of cells found in bone [4]
- *- osteoprogenitor cell
- osteoblast
- bone-lining cells (osteoblast outside after active growth)
- osteoclast (bone remodelling)**
histological features of bones:
what is lamaellae?
histological features of bones:
what is lamaellae?
- parralel bundles of collagen in thin layers with regular spaced cells between. heavily calcified
what are canaliculi?
Tiny canals in bone to allow for the passage of blood vessels for nutrient supply.
They appear as fine lines
Extend from capillaries to osteocytes and their matrix.
Osteocytes are interconnected by the canaliculi through processes. Communication through gap junctions.
bone classification:
- outside, dense part of bone is called?
- inside, less dense is called?
Bones are generally classified into 3 general groups. What are they? [3]
bone classification:
- outside, dense part of bone is called: compact
- inside, less dense is called: spongy (trabeculae)
Bones are generally classified into 3 general groups. What are they? [3]
- *- tubular
- cuboid**
- *- flat**
label A & B
A - compact bone!
B - spongy - trabeculae
what are bones covered on their outer surface? [1]
when are they not covered with this? [1]
what are bones covered on their outer surface? [1]
periosteum
when are they not covered with this? [1]
where they articulate with other bones
mature bone is composed of units called? (2 names) [2]
what connects ^? [1]
mature bone is composed of units called? (2 names) [2]
- osteons
aka
-haversian systems
what connects ^? [1]
- haversian canal connects osteons
what are volkmanns canals? [1]
what are volkmanns canals? [1]
- channels in the lamellar bone perpendicular to central canal
what is the arrangement of cells like in immature bone?
what is the arrangement of cells like in immature bone?
- cells are randomly arranged (mature bones arranged in same direction as lamellae)
- osteocyts go in different directions to lamalle
immature bones
immature woven bones form more quickly, but have less strengh than mature bone because dont have mineralised ECM
which one of these is immature and mature bone?
Osteoprogenitor cells are located where?
Osteoprogenitor cells are located on the outside of trabecula eg beside adipocytes
what is
what is periosteum?
Fibrous capsule surrounding bone
Carries blood and neural supply
Periosteal blood vessels penetrate the bone from this layer.
Inner periosteum is liner by osteoprogenitor cells.
These may differentiate into osteoblasts and so are important in bone growth, modelling and repair.
what type of bone is this? [1]
explain your reasoning [2]
what type of bone is this? [1]
compact bone
explain your reasoning [2]
parallel lamallae
densely packed osteons
what type of bone is this? [1]
explain why [2]
what type of bone is this? [1]
spongy bone / trabeculae
explain why [2]
- interconnected trabeculae covered with endosteum
osteoblast !! come back
osteoblast –> osteocytes
where do you find osteocytes? [1]
characteristic feature of osteocytes [1]
role of osteocytes? [1]
how do u prepare bone to see ^? [1]
where do you find osteocytes? [1]
- osteocytes encolosed in bone matrix, trapped in lacunae
characteristic feature of osteocytes [1]
- osteocyte processes
role of osteocytes? [1]
- respond to redeuced mechanical stress by secreting MMPs: osteocytic remodelling
how do u prepare bone to see osteocyte processes? [1]
- visible on ground sections (no stain, just dried)
- not visible with H&E
(see photo)
bone lining cells:
derived from which cells? [1]
function?
located? [2]
bone lining cells
derived from which cells? [1]
osteoblasts
function [1]
maintain and support the osteocytes
located [2]
cover internal and external surfaces
named periosteal cells when external
named endosteal cells when internal
cover the bone when its inactive / not remodelling
osteoclasts
location? [1]
characteristics? [1]
derived from? [1]
function? [1]
osteoclasts
characteristics?
large and multinucleated
location
at sites where bone is removed
derived from? [1]
from the fusion of the granulocytes / macrophage progenitor cells
function [1]
responsible for bone resorption in response to long term calcium requirements and changing mechanical stresses.
what are osteoclasts activated by?
how does it cause bone remodelling?
which other cells can activate them?
osteoclasts express a receptor molecule called RANK (receptor activator of nuclear factor). interaction with RANKL ligand molecule expressed on osteoblasts
dissolves bone matrix: pumps protons out to acidify & enzymes = bone remodelling
also activated by t-lymphocytes (can express RANKL) during inflammation
which two mechanisms does bone formation occur? [2]
endochrondral ossification: cartilage model as precursor
intramembranous ossification: no cartilage model
how does intramembranous ossification occur?
how does intramembranous ossification occur?
NO CARTILAGE
- bone is formed by differentiation of mesenchymal cells into osteoblasts at ossification centres
i) forms around capillaires - newly formed bone matrix appears in histological sections as small, irregular spicules and trabaculae
how does endochrondral ossification occur?
endochrondral ossification: cartilage model as precursor
- hyaline cartilage model in shape of bone
- bony collar formed: first sign of ossification
- chondrocytes become hypertrophic and matrix undergoes calfication. chondrocytes die
- messenchymal cells migrate into the cavity along growing blood vessels
- differentiate into osteoblasts producing bone matrix
what type of cartilage does endochrondral ossification occur from?
hyaline cartilage
what are the 6 zones that occur when endochonral ossification occurs?
zone of reserved cartliage:
zone of proliferation:
zone of hypertrophy:
zone of calcified cartilage:
zone of resorption:
what occurs at each zone when endochondral ossification occurs [6]
zone of reserved cartliage: hyaline cartilage
zone of proliferation: collagen type 2
zone of hypertrophy: chondrocytes become hypertrophied & swollen. collagen type 10.
zone of calcified cartilage: chondrocytes undergo apoptosis. matrix secreted
zone of resorption: bone tissue formed. capillaries occur and merge with bone arrow cavity. osteoblasts secrete osteod
how does bone repair occur when a fracture occurs?
- initial formation of soft callus. after endothelial regeneration and osteoblastic proliferation is replaced by woven bone
