Histology I: Lecture 9 Flashcards
histology
the study of the normal structure of tissues
tissue
-groups of cells, similar in structure, that cooperate to perform a function
-cells embedded in ECM of ground substance and fibrous proteins
primary tissue classes
epithelial, connective, nervous, muscular
epithelial tissue
sheets of tightly packed cells, little visible ECM; coverings and linings or glands
connective tissue
loosely scattered cells; ECM most prominent; bind, support, protect, connect parts of the body
muscular tissue
long, cylindrical, or spindle shaped cells; little visible ECM; contractile/generate force
nervous tissue
mostly fluid ECM; process and transmit information
extracellular matrix (ECM)
ground substance and fibrous proteins that surround cells
ground substance
EC fluid, gel, or solid; water, ions, nutrients, and macromolecules: glycosaminoglycans, proteoglycans, and glycoproteins
fibrous proteins
collagen fibers, elastic fibers, and reticular fibers
glycosaminoglycans (GAGs)
strands of ‘bottle brush’; charged- attract water molecules
proteoglycans
‘bottle brush’; slow pathogens, connect ECM to cell membranes
glycoproteins
bind plasma membrane to EC collagen and proteoglycans
collagenous fibers
(thickest) 25% of bodies protein; tough- resist stretching and tension
reticular fibers
(median thickness) thin collagen fibers with glycoprotein coat; form spongelike frameworks for spleen and lymph nodes
elastic fibers
(thinnest) made of elastin-coiled protein with ability to recoil (elasticity)
cell shapes
squamous, cuboidal, columnar, polygonal, stellate, spheroidal, discoid, fusiform, fibrous
cell junctions
physical connections between tissue cells;
types: tight junctions, desmosomes, and gap junctions
tight junctions
integral membrane proteins of adjacent cells lock together to form an impermeable seal
desmosomes
integral membrane proteins of adjacent cells interweave between cells and connect to intermediate filaments within cells; resist mechanical stress
gap junctions
interlocked protein pores that allow substances to pass between cells
(broad) types of epithelial tissue
- coverings and linings
- glands
epithelial characteristics
polarity, specialized contacts, avascular, supported by connective tissue, innervated, regeneration
structural characteristics of epithelium
cell shape, number of layers
epithelial functions
protection, secretion, excretion, absorption, filtration, sensation
simple squamous
bound by tight junctions
function: rapid diffusion, secretion
location: lung alveoli, kidney glomeruli, endothelium, serosa
simple cuboidal
function: absorption and secretion
location: liver, thyroid, mammary, salivary, kidney tubules, bronchioles
simple columnar
function: absorption and secretion
location: GI tract lining, uterus, kidneys, uterine tubes
pseudo-stratified columnar
includes cilia and goblet cells
function: secretes and propels mucous
location: upper respiratory tract, portions of male urethra
transport across epithelia
transcellular- osmosis, diffusion, active and vesicular transport
paracellular- less common (due to tight junctions)
stratified squamous
most abundant epithelia, keratinized and non-keratinized
keratinized stratified squamous
function: resist abrasion and water loss
location: epidermis
non-keratinized stratified squamous
function: resist abrasion
location: tongue, oral mucosa, esophagus, vagina
stratified cuboidal
function: secretes sweat, sperm production, and ovarian hormone production
location: sweat gland ducts, ovarian follicles, seminiferous tubules
transitional
function: distension
location: ureter and bladder
glands
cell or organ that secretes or excretes substances
exocrine glands
maintain contact with body surfaces via ducts
endocrine glands
no ducts, secrete products into blood stream
goblet cells
GI and respiratory tracts; secrete mucous
types of exocrine glands
simple tubular, simple acinar, compound acinar, compound tubuloacinar
merocrine (eccrine)
products released as vesicles during exocytosis
ie: tear glands, pancreas, gastric glands, sweat
apocrine
part of the cytoplasm broken off along with vesicles from apical portion
ie: mammary glands
holocrine
cells accumulate product, then rupture to release it
