Basic Tissues Flashcards
what is a tissue
collection of cells that form a particular function
what are the 4 basic tissues
- epithelia
- connective
- nervous (not discussed in this section)
- muscle
Epithelia key points
- covers services
- lines cavities and tissue
- form glands
characteristics:
- attached onto base membrane- avascular cells = no blood vessels in cells themselves
- bound closely together (cellularity)
- regeneration (usually quite rapid)
- polarity (apical side which faces lumen/surface and basal side attached to basement membrane)
classification of epithelia
based on -
number of cells:
simple = one layer
stratified = two or more layers
shape of cell:
squamous
cuboidal
columnar
main types of epithelia
- simple squamous
- keratinised stratified squamous
- non keratinised stratified squamous
- simple cuboidal
- simple columnar
- pseudostratified ciliated columnar epithelium w/goblet cells
simple squamous
- flat + oval shaped nuclei
- one layer of cells
- used for diffusion cuz so thin
location - blood vessels, alveoli
smooth = so provides smooth flow of blood/air etc.
keratinised stratified squaomous
flat surface cells + oval nuclei
- many layers (so is stratified)
- produce keratin on top layer
- used for protection, barrier
(- has multiple layers so if one gone, then it’s okay,
- keratin makes it tougher, waterproof)
location - skin
some oral cavity (where abrasion occurs more)
non-keratinised stratified squaomous
same as keratinised but without keratin duh
- also used as protection/barrier
location - oral cavity, oesophagus
simple cuboidal
square cells + round nuceli
one layer thick
used for secretion and absorption
location - forms glands, found in kidney tubules
simple columnar
tall cells + oval nuclei usually basally located
one layer
used for absorption + secretion
found in GI tract
(some areas have suraface mods e.g. microvilli in small intestine)
pseudostratified ciliated columnar epithelium w/goblet cells
tall cells
appear stratified - all touch the basement membran but NOT ALL reach the lumen/surface
usually modified w/ cillia and goblet cells
used as mucocilliary escalator
found in trachea & large respiratory airways
(SPECIFIC TO RESPIRATORY TRACT)
Intercellular junctions, what proteoglycans bind cells together in epithelial cells?
specialised areas of cell memb that bind one cell to another
- desmosomes
- hemidesmosomes
- tight junctions
- gap junctions
desmosomes
- very strong connections between adjacent cells
- resist stretching and twisting
hemidesmosomes
attach cells to basement memb
- act as stabaliser and anchor cell to tissue
tight junctions
- proteins that interlock between cells
- found near apical edge
- prevents passage of water & solutes BETWEEN CELLS
gap junctions
- memb proteins interlock
- contains central pore
- allows movemne tof small molecules, ions between cells
found in cardiac muscle
connective tissues: functions, main cells and extracellular matrix components
functions:
- structural framework
- supports, surrounds, interconnects other tissue types
- protect delicate organs
- trasport fluids/dissolved mat
- energy reserves
- defend body from microorganisms
always consist of cells within extracellular matrix
main cells:
- fibroblasts = cell type that sythesizes extracellular matrix
- adipocytes, macrophages, mast cells
extracellular matrix made up of:
- ground substance with tissue fluid in it
- has fibres : collagen and/or elastic
classification of connecitive tissues
- specialised connective tissue
- connective tissue proper
specialised connective tissue
e.g. blood (blood cells in plasma (extracellular fluid)
bone (bone cells in background matrix (hardened w/ Ca and Phosphate, but still counts as extracellular fluid)
cartilage (condrocytes - in matrix as well)
connective tissue proper classification
classified according to
type, arrangement, abundance of the fibres, cells and ground substance
Loose arelolar (aka loose irregular)
dense irregular
dense regular
Loose arelolar
- lots of ground substance
- few fibres (e.g. collagen, elastic)
many types: - fibroblasts (secrete hylouronan + proteins)
- adipocytes (fat cells, contain lipid droplet)
- macrophages (immune response)
- found under epithelium that lines surfaces
dense irregular connective tissue
- little ground substance
- many collagen fibre bundles arranged randomly
few cell types: - mainly fibroblasts
- resists stretching and distension due to all of the collagen fibres
found in dermis of skin
dense regular connective tissue
- little ground substance
- many densley packed collagen fibres in PARALLEL rows
- few cell types:
mainly fibroblasts
found in tendons and ligaments
cuz quite regular tension that needs to be resisted
Muscle tissue: function, types
produces movement, specialised for contraction
- skeletal
- smooth
- cardiac
similarities between ^ these 3:
- all elongated parallel to axis of contraction
- numerous mitochondria
- contractile elements
skeletal muscle
- moves, stabilises the skeleton
- forms sphincters in digestive or urinary tracts (e.g. bumhole contracts to stop poop)
- involved in respiration (contraction relaxation of sutff)
- long cylinderical cells
- striated (look striped)
- multinucleated ( cuz so long, usually at periphery of cell)
- innervated by somatic nervous system
xsmooth muscle
- located in organs, blood vessels, airways
- responsible for GI movement (peristalsis)
- alters diameter of airways and blood vessels (e.g. if u want to inc blood vessel by contricting, smooth muscle constricts)
- short, fusiform (ie spindle shaped)
- non striated
- single nucleus in the middle
- innervated by autonomic nervous system
cardiac muscle
- found in heart fall
- circulates blood, maintains BP
- branched muscle fibres
- striated
- 1 or 2 central nuclei
- cells are joined by interclated discs joined by gap junctions
- innervated by autonomic nervous system
what is transitional epithelium
aka urothelium
foud in stratified epithelium
appears cuboidal when relaxed and squamous when stretched
e.g. found in bladder
