EPITHELIA Flashcards
What are the two types of epithelia
Surface epithelia that lines the surfaces of internal and external surfaces of the body
Glandular epithelia epithelial cells involved in secretion
What supports all epithelial cells? what is its function
Basement membrane
separates epithelia from underlying connective tissue
Brings blood and nervous innervation close to epithelia
Why is it Polarity important in simple cuboidal and simple columnar epithelium
allows the cells to have asymmetry which allows specific receptor proteins and transport proteins to be present on different sides of the cell. As such all epithelial cells have an apical and basal side
What are the two layers of the basement membrane
Basal lamina comprised of mainly collagen one to which epithelial cells directly anchor
Reticular lamina thicker layer of reticular fibres
What is the difference between simple, stratified and psudostratified epithelium
Simple: all cells have direct contact with basement membrane single layer
Stratified: multiple layers of cells. Only deepest cell layer has connection with basal lamina
Psudostratified: single layer of irregularly shaped cells all with direct contact with the basement membrane
How do you classify epithelial tissue?
First simple stratified psudostratifed
Then classify by shape squamous columnar transitional
Then add ending epithelium
Where can you find simple squamous epithelium
Alveoli
walls of capillaries (endothelium)
Not resistant to abrasion allows rapid diffusion absorption secretion
Where would one find simple cuboidal epithelium
Collecting tubules of kidney
Thyroid follicle cells
What are characteristics of simple cuboidal epithelium
Nucleus contrarily located
Box shaped in contact with approximately 6 other cells
Found on secretory and absorptive surfaces
Where in the body can you find simple columnar epithelium?
small intestine
stomach
What are key identifiable features of simple columnar epithelium?
cells taller than they are wide
nucleus more basaly located
How are stratified epithelium classified?
On shape of outermost cell
What are the characteristics of stratified squamous epithelium
more resistant to friction and abrasion
layer in contact with basement membrane active mitosis and cell division
Where can you find stratifies squamous epithelium
Vagina
oesophagus
oral cavity
What is keratinised stratified squamous epithelium
Keratinised cells
Further protection to withstand abrasion and from a protective waterproof barrier
Skin
What is transitional epithelium?
Where is it located
Adaptations
Cell shape changes
Stratified not all cells in contract with basal lamina
Found in the urinary tract e.g. bladder
Allows cells to stretch and change shape and withstand high toxicity of urine
What are some tissue specialisations?
Villi increase surface area for absorption
Cilla beat rhythmically to waft mucus
Goblet cells produce and secrete mucus
What is ciliated psudostratified epithelia with goblet cells
found in upper respiratory tract
acts to trap pathogens and dust particles preventing them entering the lungs
cilia beat to prevent stagnation waft mucus up to mouth swallowed
What are the most apical junctions in cells?
Tight junction Zona occludens
super-tight impermeable junctions prevent movement of proteins on cell surface and ions between cells
all ions and molecules must pass through the cell
What is the zona adherens what is there function
Belt desmosomes
located just below tight junctions involved in cell to cell anchoring and stability
What is the macula adherens
Spot desmosomes
ack like wielding points between cells
What are gap junctions?
formed from 6 connexins on each side of the membrane joining together to from a connexion which then lign up to form a channel
An electrical synapse allow for electrical continuity between cells through movement of ions
What are hemidesmosomes
Junction through which epithelial cells attaches to the basal lamina
What does carcinoma mean?
form of cancer that originates in epithelia tissue
