2: Tissues Flashcards
4 different tissues
epithelia, connective, muscle, neural
epithelia tissue
covers exposed surfaces
lines internal passageways and chambers
produces glandular secretion
many layers of cells
classified according to number of cell layers and shape
key features in epithelial cells
cell junction - joins two cells
cilia - hair like structures on top
microvilli - smaller hair like structures to increase surface area
basement membrane - connects to basal surface
apical surface = top surface, may be open to outside world
mitochondria, nucleus, Golgi apparatus
no blood vessels
4 functions of epithelia
provide physical protection
control permeability
provide sensation
produce specialised secretions (exocrine secretions discharged onto surface, endocrine secretions released into surrounding tissue and blood)
cell junctions
tight junction = lipid layers of adjacent plasma membranes tightly bound by interlocking membrane proteins
gap junction = two cells held together by embedded membrane proteins
simple squamous
linings e.g. blood vessel
reduce friction, used for absorption and secretion
thin flattened cells = smooth surface
good for diffusion
stratified squamous
found where mechanical stresses are severe e.g. skin
physical protection from abrasion, pathogens, chemicals
more layers of cells for more protection
simple cuboidal
lining glands
secretion and absorption
large cells for organelle
stratified cuboidal
relatively rare
along ducts of sweat glands
simple columnar
protection, secretion, absorption
lines stomach and intestinal tract
stratified columnar
relatively rare
along portions of pharynx, epiglottis, anus
only top layer of cells columnar
pseudostratified ciliated columnar
appear layered but in fact all connect to the basement membrane
line nasal cavity, trachea, bronchi
move mucus with cilia
transitional epithelium
stratified epithelium that tolerates repeated cycles of stretching and recoiling
e.g. lining of uterus and bladder
exocrine glands
produced exocrine secretions through a duct onto a surface
classified as unicellular or multi-cellular
multi-cellular further classified by branching pattern of duct and it’s shape (tubular, coiled, branched, alveolar)
methods of secretion
merocrine = product released from secretory vesicles by exocytosis, most common method
apocrine = loss of both cytoplasm and the secretory product, outermost portion of cytoplasm becomes packed with secretory vesicles before shedding
holocrine = entire cell packed with secretory vesicles then bursts, releasing the secretion but killing the cell
types of secretion
serous glands = secrete watery solution containing enzymes
mucous glands = secrete mucins that form think slippery mucus
mixed glands = contain more than one type of gland cell
connective tissue
3 basic components: specialised cells, extracellular protein fibres and fluid known as ground substance
matrix = extracellular fibres and ground substance
never exposed to outside environment
highly vascular - many blood vessels
functions of connective tissue
support and protection
transportation of minerals
storage of energy reserves
defence of the body
3 major types of connective tissue
connective tissue proper = tissue under skin, can be loose or dense
fluid connective tissues = blood and lymph
supporting connective tissues = cartilage and bone