Lecture 1 - Histology Flashcards
why do we need to study histology?
we can correlate pathological changes in function to changes in tissue and its components
Histology is relevant at what levels?
mostly tissue and cellular and partially molecular, from around 1mm to 1um
connective tissue =?
cells + extracellular matrix
Extracellular matrix =?
ground substance + fibres
describe briefly the extracellular matrix
it is a 3d network consisting of molecules and minerals that provide biochemical support to surrounding tissues
what are the major cells of connective tissue?
fibrocytes (CT proper)
chondrocytes (cartilage)
osteocytes (bone)
are fibers a part of the ground substance?
no, fibers are a separate component of the ECM
what is ground substance primarily composed of?
water and large organic molecules (glycosaminoglycans, glycoproteins and proteoglycans)
what are GAGs?
polysaccharideds that trap water, giving the ground substance its gel-like texture.
what is the role of proteoglycans and glycoproteins?
provide structure to the ground substance and attaches components of the GS to each other and cells.
what type of sugar attachement does a glycoprotein have?
oligosaccharide
what type of sugar attachment does a proteoglycan have?
polysaccharide
what is chondroitin sulfate?
a type of GAG, which is the polysaccharide attachment of a proteoglycan
what is the main difference in non fibrous components of areolar tissue vs dense regular tissue
there are far less non fibrous components in dense regular tissue than areolar tissue.
(e.g. less ground substance and PGs and GPs)
the amount of ground substance in a type of connective tissue directly relates to its….?
function
what are the three types of fibers of the ECM?
collagen, reticular and elastic
describe the features of collagen fibers
- long and unbranched
- stretches a little but not much (~20%)
- provides strength
- a bit flexible
describe the features of reticular fibers
- contains collagen type III but are thinner and branched
- strong but flexible
- allows movement of cells while maintaining structure e.g. spleen
describe the features of elastic fibres
- branched
- allows tissue to stretch (200%)
- elastin
- allows for movement
list the main functions of areolar tissue
- holds organs in place and provides cushioning
- attaches epithelia to underlying tissue
- allows cell movement (e.g phagocytic cells which provide defense against pathogens)
why would areolar connective tissue require cell movement of phagocytic cells?
exposure to environment: such as pathogens and injury
what is the function of adipose connective tissue?
- provides cushioning
- insulation
- stores energy
- heat production?
where is there areolar (loose) connective tissue?
in the dermis of the skin and the lamina propria of the small intestine
is there a higher % of GS or fibres in areolar connective tissue?
more GS and therefore more proteoglycans
in adipose tissue, how does the % of cells relate to GS?
hardly any ground substance present due to large lipid filled cells.
- this related directly to its functions
what other type of connective tissue is found in adipose tissue in trace amounts?
reticular connective tissue
what are the main functions of reticular connective tissue?
- fibres form a supporting skeleton for organs
- allows movement of cells and fluids
where is adipose connective tissue commonly found?
in the skin and intestine
is there a higher % of GS or fibres in reticular connective tissue?
more GS than fibres, but the fibres create a network for cell movement
where is reticular connective tissue commonly found?
in the liver.
the reticular tissue provides structure but also allows movement which cannot be provided by areolar or dense connective tissues
what are the functions of dense regular connective tissue?
- provides firm attachment
- strength in one direction
- stabilize position of bones
is there a higher % of GS or fibres in dense regular connective tissue?
more collagen fibres (usually type I)and hardly any ground substance and therefore very little proteoglycans
what are the functions of dense irregular connective tissue
- provides strength
- resistant to forces from different directions
where is dense irregular connective tissue commonly found?
skin and intestines, as these locations move and require force resistance from different directions
what is the supporting connective tissue classes?
- hyaline
- elastic
- and fibrocartilage
what are the functions of hyaline cartilage?
- reduces friction
- allows for compression
- provides flexible support
is there a higher % of GS or fibres in hyaline cartilage
more ground substance and therefore proteoglycans
what produces cartilage?
condrocytes in lacunae in the ECM
where is hyaline cartilage commonly found?
Joints
- flexible support which allows for compression and reduces friction
describe the main functions of elastic cartilage
- provides support and flexibility
- allows tissue to distort but return to its original shape
where is elastics cartilage commonly found?
in the ear
what are the main functions of fibrocartilage
- resists compression
- provides cushioning
where is fibrocartilage commonly found?
intervertebral disks
why is the fibrocartilage at the intervertebral disks but not at the knee joints?
the main role of hyaline cartilage at joints is to reduce friction. the fibrocartilage is rougher and would not be as adequate for this reason.
