Epithelial Flashcards
Advanced, beyond NCERT
Tissue term given by? was first seen in which animal group?
Bichat
tissue first appeared in coelentrates/cnidarians
Histology term given by
Mayer
Founder of histology
Malpighi
Epithelium term given by
Ruysch
Exception of nervous tissue when three germ layers are considered
MICROGLIA (mesodermal)
epithelial tissue which is vascular
stria vascularis (cochlea of ear)
fish scales are? (wrt tissue) can they be removed?
what about snake scales?
also, which epithelial tissue is present in human skin?
dermal. no, hence used to determine age of fish.
snake cells are epidermal.
Keratinised stratified squamous (compound)
mostly cell junctions are found in which tissue
epithelial
extracellular, living basement membrane is characteristic of epithelial tissue.
basement membrane is made of?
false.
extracellular, non living basement membrane is characteristic of epithelial tissue.
basement membrane is sandwiched between the epithelial and connective tissue and is made up of their respective cell products/ secretions giving the upper, thin basal lamina (glycoproteins and mucopolysaccharides) and lower, thick fibrous reticular layer (collagen and reticular fibres).
thyroid follicular glands and gonads: which epithelium
cuboidal
bronchi and trachea
ciliated pseudostratified columnar
male’s urethra
non ciliated pseudostratified columnar
ependymal
ciliated columnar
simple tubular
crypts of leiberkuhn
branched tubular
gastric and uterine
compound tubular
brunners, mammary glands of protherans
simple coiled tubular
sweat
simple alveolar
cutaneous glands of frogs
simple branched alveolar
sebaceous
compound alveolar
sublingual, submandibular
compund tubulo alveolar
pancreas, parotid, mammary
zymogen granules are found in which of pancreas
secretions include enzymes, hence, exocrinal component i.e. pancreatic acini
islets of langerhans form which component of pancreas
secrete hormones, hence, endocrinal part
apocrine
mammary, axillary sweat
holocrine
sebaceous
merocrine
most sweat, digestive
Urinary bladder, ureter, urethra
Transitional/Urothelium
Superficial most layer: stratum corneum (outermost layer of skin which forms horns of some mammals)
germinative layer: stratum germinatum/ stratum malpighi (columnar cells)
Which junctions are always found on the top layer?
Zona occludens (tight junctions) "these junctions prevent leakage of substances across tissue and are observed in the apical part of the adjacent epithelial cells"
Tight junctions and gap junction aka
Zona occludens and macula occludens
(gap junctions are made up of protein sub units called connexons. these connexons help in transfer of ions, small molecules and sometimes even large molecules)
Plasma membrane in apical parts of adjacent epithelial cells becomes tightly packed to form?
Tight junctions (Zona occludens)
What is present just below tight junctions
adhering junctions/ intermediate junctions
perform the job of cementing cells together
describe intermediate/adhering junctions
zonula adherens
these are present immediately below tight junctions. the intercellular spaces contain low electron density fluid. there is a dense plaque like on the cytoplasmic site of each plasma membrane from which fine microfilaments of actin protein extend into the cytoplasm. there are no intracellular filaments in intermediate adhering junctions.
2 major differences between Zonaula adherens and Macula adherens
Intermediate/adhering junctions versus Desmosomes
1) Intermediate adhering junctions do not possess intercellular filaments/protein, whereas intercellular proteins are present in desmosomes
2) Intracellular protein of intermediate adhering junctions: actin, while Desmosomes have non-actin (keratin like) protein intracellular filaments called tonofibrils. They are thicker and stronger.
What do hemi-Desmosomes do?
hemi desmosomes are single sided desmosomes adn are hence quite similar to them, just that the thickness of the cell membrane is seen only on one side. more importantly, They connect the epithelial tissue to basement membrane
Olfactory mucosa
Sensory epithelium (nose)
Schneiderian membrane
Sensory epithelium (nasal canal)
Myoepithelium does what? Seen in?
Contraction (mammary, sweat)
Pigmented epithelium is found where?
Retina, iris
Layers of diffusion boundary
Three:
1) endothelium
2) basement membrane
3) alveolar squamous epithelium
Mesothelium refers to
Epithelium of visceral organs (SEROSA)
Wall of alimentary canal has how many layers
Four:
1) serosa- Mesothelium
2) muscularis
3) sub mucosa- CT with blood nerves lymph (sometimes glands like duodenal/Brunner’s)
4) mucosa- inner epithelium
Mucosal epithelium refers to
Mucosa, i.e. , goblet cells which release mucus for lubrication
Mention variations in mucosa in stomach and intestines
though in stomach, simple columnar and in small intestine, ciliated columnar are found certain structural variations are also detected. given as follows:
Mucosal infoldings in stomach are known as RUGAE and act as gastric glands.
Small Intestine has villi and microvilli to increase surface area, the valley of these villi have mucosal epithelium and glands- crypts of Lieberkuhn
Also, SI has circular folds of mucus membrane: PLICAE CIRCULARIS/VALVE OF KERKING/VALVULAE CONNIVENTES
Valves of Kreking, what relevance do they have wrt to epithelial tissue
They are circular folds of mucosal membrane found in small intestine.
what part of the body is the first to face both internal and external environment?
epithelial tissue. present on the lining of any surface, external or internal.
simple epithelium ncert function and structure
#made up of a single layer of cells, all of which rest on the basement membrane (contrast with compound epithelial tissue where only the first germinative layer is present on the basement membrane) #serves as a lining for body cavities, ducts and tubes #functions: filtration, exchange, secretion, absorption
tesselated epithelium is a modification of?
simple squamous epithelium: flat, polyhedral with centrally placed nucleus.
(named so due to their wavy/ irregular boundaries.)
which epithelium is present as a lining of blood vessels, lymph vessels, heart, coelom, visceral organs? name these linings.
simple squamous.
blood vessels: endothelium
coelom/visceral organs: mesothelium
in the histology of gut, serosa is the outermost layer which is made of mesothelium with some connective tissue, while the innermost layer lining the lumen of alimentary canal is mucosa. This layer forms irregular folds called rugae in the stomach and small finger like foldings called villi in the small intestine. The cells lining the villi produce numerous microscopic projections called microvilli giving a brush bordered appearance (increase SA). villi are supplied with a network of capillaries and a large lymph vessel called the lacteal. Mucosal epithelium has goblet cells which secrete mucus which helps in lubrication. Mucosa also forms glands in the stomach (gastric glands: branched tubular) and crypts in between the bases of villi in the intestine (crypts of lieberkuhn: simple tubular)
