Lecture 5 - Epithelial Tissue Flashcards
where are epithelial tissue derived from
all three germ layers
where is the epidermis derived from
ectoderm
where is the lining of the GI tract and respiratory tract derived from
the endoderm
where is the endothelium and mesothelium derived from
the mesoderm
endothelium definition
lining of blood vessels, derived from mesoderm
mesothelium definition
lining of pericardial and thoracic cavities, derived from mesoderm
two types of epithelial tissue
membranous epithelia
glandular epithelia
membranous epithelia
sheetlike tissues that cover or line surfaces, cavities and organs of the body
glandular epithelia
perform secretory functions
what do epithelial tissues cover
tubes (digestive and cardio tracts), cavities (thoracic), and all body surfaces (skin)
functions of epithelial tissue (5)
protection and containment (skin) absorption (intestines) secretion (glands) sensation (neuroepithelium) contractility (myoepithelium)
characteristic of epithelial tissue
- cells closely bound together by membrane specializations (junctions), form continuous sheets
- supported by basement membrane (seperated from underlying supporting tissue)
- Not penetrated by blood vessels (avascular)
- Polar
simple epithelial tissue
on a surface or facing a lumen single layer places where diffusion, absorption, or secretion occur squamous, cuboidal, or columnar have cilia or microvilli
simple squamous
flat cells (scales) diffusion of fluids or gas (very thin)
location of simple squamous
lungs, blood and lymphatic vessels, cavities (pleural, peritoneal, pericardial)
simple cuboidal
as tall as they are wide with prominent nucleus
excretion, secretion, absorption
location of simple cuboidal
ducts of kidney, thyroid gland, salivary gland
simple columnar
cells taller, eliptical nucleus located basally function in absorption
location of simple columnar
intestines
simple columnar ciliated
cilia at apical surface
propel ovum over cell surface to uterus
in the oviduct and respiratory tract
pseudostratified columnar ciliated
nuclei at different positions but only one real layer
propel mucuous and entrapped particles
in trachea
Sometimes lymphocytes will have infiltrated
stratified
two or more layers
protective function
classification is based on shape of cell at surface
stratified squamous
top layer flattened
withstand chronic abrasion
in oral cavity, esophagus, cervix, vagina
stratified squamous keratinized
surface layer of keratin, withstand chronic abrasion, epithelial surface of skin (epidermis)
stratified cuboidal
1-2 layers of cuboidal
provide thicker lining
larger excretory ducts of exocrine glands (ex: salivary glands)
transitional epithelium
many layers of cells, top is round and pillowed
withstand toxicity of urine and accommodate stretch
in urinary tract
where are binucleated cells found
surface of transitional epithelium
glandular epithelium
invagination of epithelial surfaces, formed during embryonic development, proliferation of epithelial cells into underlying connective tissue NOBODY KNOWS TRIGGER
exocrine gland
maintain continuity with epithelial surface, discharge secretions via ducts
endocrine gland
degenration of duct leaving islands of epithelial tissue, secretory products go right into blood
modes of exocrine secretion
- merocrine, most common, no loss of membrane (ex: goblet cell)
- apocrine - secretory product in vesicles (ex: mammary gland)
- holocrine - whole cell broken for discharge of products (ex: sebaceous gland)
secretion into lumen is through what layer
apical (exocrine)
secretion into blood vessel is through what layer
basal (endocrine)
goblet cell is what type of gland
unicellular
goblet cells use what type of secretion
merocrine
synthesis of mucigen
protein component in RER, goes to golgi where a carb gets attached
release of mucigen
secreted at steady basal rate, local irritation will cause release of entire mucigen content
function of goblet cells
in upper GI tract, provide protection coat against autodigestion
in lower GI tract, provide lubrication
in respiratory tract, prevent drying and helps humidify inspired air and act as sticky surface to trap dust and microorganisms so they don’t go to lungs
