epithelium Flashcards
what are the 4 basic tissue types
- Epithelium
- Connective tissue
- Muscle
- Nervous tissue
what do these make up
almost all tissues and organs are made up of a combination of these
what is epithelium composed of
closely aggregated, polyhedral epithelial cells with a minimum
of intercellular substance.
what does surface epithelia cover
surfaces, cavities and tubes
how does epithelilal cells protect its structures
Adhesion between cells is strong; thus cellular sheets are formed which cover exposed external surfaces and line internal cavities and form solid organs
what are the functions of the epithelia
▪Mechanical barrier (e.g. skin)
▪ Chemical barrier (e.g. lining of stomach)
▪ Absorption (e.g. lining of intestine)
▪ Secretion (e.g. salivary gland)
▪ Containment (e.g. lining of urinary bladder)
▪ Locomotion (by cilia) (e.g. oviduct
what are the characteristic of epithelal cells
- typically polarised (head and tail JOINED to basal membrane)
- basal surfacea ttatched to basal lamina
- non vascular
- tend to adhere toghether in sheets where cells are closely spposed to one another requiring a cytoskeleton and
prominent intercellular junctions.
what 3 main classes of filaments form the cytoskeleton of cells
microfilaments - 5nm dia
intermediate filaments - 10nm dia
microtubules - 25nm dia
how do they form the cytoskeleton
these filamentous protiens attatch to cell membrane and each other, by anchoring and jpining protien to form dynamic 3d internal scaffolding
what are the 3 types of junctions in between the epithelial cells
occluding - form between diffusion barrier
anchoring - provides mechanical strength
communicating - allows movement of molecules between cells
what is the junctional complex
close association of several types of junctions found in certian epithelial and other tissue
e.g - ZO, ZA, MA
what are epithelia classified on
Cell Shape:
▪ Squamous (flattened, like a fish scale)
▪ Cuboidal (cube shaped)
▪ Columnar (like a column, relatively tall and thin)
The Number of Layers:
▪ ‘Simple’ = one layer
▪ ‘Stratified’ = two or more layers
▪ ‘Pseudostratified’ = tissue has multiple layers, but all cells are in contact with the basal lamina
presence of specialised cells of cell/tissue surface or within epithelium
what is cilia
motile cell process
propel mucosa or fluid over cell surface
what is keratin
tough structural protiens found associated with some stratisfied squamous epithelia
what solid organs are formed of epithelium cells
glandular organs mostly
where is exocrine gland product secreted
toward the apical end of the
cell into the lumen of internal space, into a duct, or onto
the body surface.
Termed ‘ducted’ glands
e.g Lacrimal glands
Pancreas
Salivary glands
Sweat glands
Mammary glands
Liver
Brunner’s glands
Sebaceous glands
where is endocrine gland product secreted
toward the basal end of the
cell (end sitting on basal lamina), then distributed by
vascular system throughout body.
Termed ‘ductless’ glands.
e.g Pituitary gland
Thymus gland
Thyroid gland
Adrenal glands
Pancreas
Ovaries/Testes
