7) trans-epithelial transport: kidney tubules transport salt & water from the lumen of collecting tubules back into bloodstream through the interstitial space
8) contraction of myoepithelial cells: eg. to squeeze milk from excretory lobules of mammary glands
PARTTSS C
How is epithelia classified?
1) by the number of cell layers
2) by the shape/height of cells
3) whether they are ciliated or non-ciliated
simple
signifies a single layer of epithelial cells
typically found in tissues specialized for absorption & secretion but NOT subject to extensive wear & tear
eg. endothelium, mesothelium, bowman’s capsule, distal and proximal convoluted kidney tubule, small intestine, lung alveoli
Where is the shape or height of epithelium cells observed?
the shape of epithelium cells is classified by observing their most apical (outermost) layer
squamous
cells that are thin, flat & scale-like
cuboidal
cube-shaped cells
columnar
cell that are taller than they are wide
simple squamous (4)
a single layer of thin, flat & scale-like cells specialized for filtration, diffusion, osmosis & secretion
1. cells lining capillaries (endothelium)
2. serosal cells lining mesentery
3. cells lining Bowman's capsule of kidney
4. cells lining lung alveoli
What type of epithelial cell are the arrows pointing toward? (dark purple cells)
mesothelium - a form of simple squamous
lines body cavities and allows passage of tissue fluids into and out of these cavity by diffusion (also lubricates to prevent friction)
What type of cells are the arrows pointing toward? (dark purple cells)
endothelium - a form of simple squamous epithelia found in blood vessels
these cells are specialized for passive transport (diffusion) of fluids
endothelial cells of capillary (cross-section)
simple squamous epithelium
simple cuboidal (1)
a single layer of cube-shaped cells specialized for secretion and absorption
1. cells in kidney tubules
collecting tubule in kidney made up of simple cuboidal epithelium
secretory, excretory & absorptive functions
simple columnar epithelium of small intestine
specialized for absorption
simple columnar
single layer of cells whose height is greater than their width specialized for secretion and absorption
these cells may or may not be ciliated
1. intestinal epithelium cells
pseudostratified columnar (2)
epithelial cells that appear to be stratified (have more than two layers) because cell nuclei look like they're in a different layer, however each cell actually rests on the basement membrane and there's really only a single layer of cells
1. ducts in the male reproductive system: EPIDIDYMIS
2. respiratory tract: TRACHEA
these cells may be ciliated, and if so are specialized for secretion and propulsion of mucus by beating ciliary action
*when in doubt whether something is pseudostratified or stratified cuboidal or columnar, GUESSING pseudostratified means you will be right 99% of the time
pseudostratified columnar epithelium (of the trachea)
specialized for propelling mucus & debris toward the throat
stratified squamous
consists of flattened (squamous) cells on the surface of multiple layers of cells; usually protective
1. keratinized/cornified: differentiating cells formed by mitosis at the basal layer that make a lot of keratin, lose their nuclei, & move apically to replace the outermost squamous layer of cells (eg. skin)
2. non-keratinized/non-cornified (moist): cells that produce less keratin & apical squamous cells do not lose their nuclei (eg. esophagus)
stratified squamous keratinizing epithelium of thin skin
specialized for protection, waterproofing
stratified squamous keratinizing epithelium of thick skin
found in vagina, oral cavity, esophagus & anal canal
nuclei present in surface layer
stratified cuboidal
multiple layers of cube-like cells found in epithelium lining large glandular ducts
they're specialized for protection
stratified cuboidal epithelium
lines large excretory ducts of exocrine glands such as salivary gland; functions in protection
stratified columnar
multiple layers of cells whose height is greater than their width specialized for secretion and protection
1.epithelium lining of very large glandular ducts.
2. portions of male urethra
(others: ocular conjunctiva of the eye, parts of the pharynx & anus, female's uterus, male's vas deferens)
stratified columnar epithelia
transitional epithelium
unusual stratified cuboidal epithelium whose appearance varies depending on whether it's contracted or expanded
it's specialized for distension and contraction to accommodate the changes in volume of urine
apical cells are dome shaped, some are bi-nucleated
1. lining of renal pelvis
2. ureter
3. urinary bladder
4. initial part of urethra
transitional epithelium of urinary bladder
has umbrella cells & occasional bi-nucleated cells in superficial layer; is specialized for waterproofing, distention
glands
single or groups of cells specialized for secretion
glands are derived from epithelia (glandular epithelia)
What are the two types of glands?
exocrine and endocrine
endocrine gland
glands that secrete secretions into the bloodstream through the interstitial space
they do NOT have ducts and are NOT all derived from epithelia
exocrine glands
glands that release their secretions into ducts continuous with the surface epithelium of an organ (eg. in skin or gastrointestinal tract)
How are exocrine cells classified?
1. the number of cells in the gland: unicellular or multicellular
2. the duct system: simple or compound
3. architecture of terminal branches: tubular or acinar
4. nature of secretion: mucous or serous
5. mode of secretion: merocrine, apocrine, holocrine
simple glands
either do not branch or branch only once
type of exocrine gland classification
compound glands
branch repeatedly to form a branched tree
type of exocrine gland classification
tubular glands
form terminal tubular lobules
type of exocrine gland classification
acinar glands
form terminal rounded, grape-shaped, lobules
type of exocrine gland classification
compound acinar gland
the branched duct system means it's compound
mucous secretion
watery
serous secretion
serum-like
submandibular gland
a branched compound tubuloacinar salivary gland whose secretory portion contains BOTH mucus and serous cells
Merocrine
secretion by exocytosis
eg. mechanism for the secretion of mucus by goblet cells by mucus or serous by salivary glands
type of secretion done by exocrine glands
Apocrine
secretion by decapitation of cells’ apical region
mechanism for the production of milk in mammary gland
type of secretion done by exocrine glands
Holocrine
secretion of whole cells’ content following apoptosis
mechanisms for the production of sebum (mixture of lipids) by the sebaceous gland
type of secretion done by exocrine glands
What type of cell is stained darkly? What is it's mode of secretion? What does it secrete?
Goblet cell - UNIcellular gland found in the intestinal epithelium that helps keep it moist
uses merocrine (secretory vesicles, exocytosis) to secrete mucus
Cystic Fibrosis (CF)
is a common inherited autosomal recessive disorder caused by malfunctioning of the cystic fibrosis transmembrane conductance regulator (CTFR), small chloride channel,
the CFTR channel is found in the apical membrane of epithelial cells of many organs including the lung, liver, pancreas, digestive tract, reproductive track & skin
the membrane protein normally moves Cl- OUT of an epithelial cell to the covering mucus.
absence of the channel results in imbalance of ion concentrations across the cell membrane and more viscous mucus
Breast cancer
lobular carcinomas - most common types of breast cancer originates from the epithelial cells lining the milk-producing secretory lobules in the mammary gland
ductal carcinomas - less common types of breast cancer originates from epithelial cells lining the ductal system
What type of epithelial cells are these?
simple sqamous - very flat cells
small arterial (blood) vessel
this type of tissue specializes to allow diffusion of gasses into/out of the tissue
endothelium vs. mesothelium
mesothelium will generally line entire body cavities
endothelium is seen lining smaller things, such as blood vessels
What type of epithelial cells are these?
simple squamous epithelium
cells that line the Bowman's capsule of a kidney glomerulus