Tissue level organisation Flashcards
cell junctions. definition and function
points of contact between adjacent cell plasma membranes
- form fluid tight seals
- anchor cells together or to extracellular material
- act as channels, which allow ions and molecules to pass from cell to cell
list 5 cell junction types
tight junctions adherent junctions desmosome hemidesmosomes gap junction
Tight junctions
- structure
- function
- location
plasma membranes fused with strap of transmembrane proteins
watertight seal between seals
common between cells that line GIT and bladder
Adherens junctions
- structure
- function
- location
dense layer of proteins (plaque) insdide cell membrane attaches to membrane proteins (catherine) and microfilaments (actin)
holds epithelial cells together
common between cells that line GI
Gap junctions
- structure
- function
- location
cells are separated by fluid filled tunnels called connexons
cell communication, diffusion of ions and small molecules, transfer fo nutrients
heart and smooth muscle of gut; muscle and nerve impulses spread from cell to cell
Desmosomes
- structure
- function
- location
contains plaque and catherine and attaches to intermediate filaments (keratin)
cell to cell stability
skin and cardiac muscle
Hemidesmosomes
- structure
- function
- location
half desmosome; same structure ad desmosome but it connects cell to underlying basement membrane d extracellular material using membrane proteins (integrin)
cell to membrane stability
any cell attached to basest membrane
Types of tissues.
definition
4 principle types (ecmn)
tissue is a group of similar cells that are specialised for a particular function
epithelial tissues
connective
muscle tissue
nervous
Epithelial tissue
structure
- closely packed epithelial cells that always have a free (apical) surface and a basal surface
- little extracellular material between cells
- many cell junctions
- cells sit on basement membrane
basal lamina
reticular lamina - avascular (no blood supply)
- good nerve supply
- rapid cell division (high mitotic rate)
Epithelial tissue
general functions
- selective barrier
helps transfer substance in / out of body
-secretory surface
release molecules into free surface
-protective surface
resist any abrasive influence of environment
What two types is epithelial tissue is there?
covering and lining epithelium
glandular epithelium
classification of covering and lining epithelium
name 3 arrangement of cells
simple (one layer)
stratified (two or more)
pseudostratified (located at multi levels - lots multilayered)
classification of covering and lining epithelium
name 4 shapes of cells
squamous (flat)
cubodial (cube shaped)
columnar (tall column)
transitional (shape varies with tissue stretching)
simple squamous epithelium
structure
function
location
single layer. flat scale like cells. nuclei centrally located
diffusion, secretion, filtration
lining of blood vessels (endothelium), serous membranes (mesothelium), kidneys, lungs
simple cuboidal epithelium
structure
function
location
single layer of cube shaped cells. nuclei round and centrally located
secretion and absorption
lines kidney tubules, makes up secreting portion of glands
simple columnar epithelium
non-ciliated & ciliated
structure
function
location
non ciliated
- single layer of column like cells
- no cilia but microvilli and goblet cells present
- oval nuclei near base of cell
secretion, absorption and protection
lines GIT, ducts of glands
Ciliated
- single layer of column like cells
- cilia present
- oval nuclear near base of cell
motility
lines bronchioles, uterine tubes, uterus, ventricles of brain
Pseudostratified columnar epithelium
ciliated and non ciliated
structure
function
location
non ciliated
- single layer - appears to have several
- nuclei at various levels
- no cilia, lacks goblet cells
absorption and protection
large ducts of glands, male urethra
Ciliated
single layer - appears to have several
nuclei at various levels
cilia and goblet cells present
secretion (mucous) motility
lines airways
stratified squamous epithelium
keratinised and non.
structure
function
location
keratinised
- several layers of cells. apical layer flat. deeper layers vary from cuboidal to columnar
- tough layer of keratin in apical layer
- protection
- superficial layer of skin
non keratinised
- several layers. apical is flat. deeper vary from cuboidal to columnar
- does not contain large amounts of keratin
constantly moistened by mucous
lines mouth, oesophagus, pharynx, vagina
stratified cuboidal epithelium
structure
function
location
2 or more layers of cells where apical cater is cube shaped
fairly rare
protection
limited secretion and absorption
ducts of sweat glands, male urethra
stratified columnar epithelium
structure
function
location
2 or more layers where apical layer is columnar and lower layers and irregular in shape
uncommon
protection and secretion
lines large, excretory ducts f some glands, part of urethra and in conjunctiva of eye
transitional epithelium
structure
function
location
multiple layers. variable appearance
apical surface contains large rounded cells
cells change shape as tissue stretches from cuboidal to squamous
protection
lines urinary bladder, ureters, urethra
Glandular epithelium
list the two types and a general description
gland is a single cell or a mass of epithelium cells adapted for secretion
endocrine glands
exocrine glands
Endocrine glands structure function location
ductless secrete product (hormones) into interstitial fluid and then into blood stream
secrete hormones that maintain homeostasis
brain, thyroid, adrenal, pancreas, reproductive organs
exocrine glands
structure
function
location
contains ducts
secrete product into ducts that empty onto surface of a covering an lining epithelium (skin)
secrete substances such as sweat, oil, saliva, digestive enzymes
salivary, sudorifero and ceruminous glands, pancreas
