Tissues 1 Flashcards
What 5 things is the human body mainly composed of?
- cells
- ECM (shape+structure)
- tissue fluid (removes waste+metabolites)
- organs
- tissues
what are the 4 types of tissues?
- nerve
- muscle
- connective
- epithelial
(nobody ever compliments me)
what is a tissue?
specialised cells which have the same function
what is function of epithelial tissue? (3)
- covers surfaces (e.g. wall of body organs) and open cavities (e.g. digestive and respiratory systems)
- sheets of connected cells
- separates compartments
what are some of the secondary functions which epithelial tissue cells often have? :3
secretion, absorption, retaining (forms glands)
what structures often have epithelial tissue linings?
blood vessels, lungs, skin, gut etc.
what is the function of connective tissue?
- connects!
- provides internal support, can include bone, ligaments, tendons, cartilage and adipose
- structural and metabolic support (supports, binds, separates)
what are the 2 main constituents of connective tissues?
- cell
- ECM
Both define its function and structure
It’s not cells which define connective tissue, but it’s…
extracellular proteins in the matrix
what are 3 main examples of connect tissue?
- blood
- bone
- adipose
what is the matrix of fat composed of?
liquid AND solid
what is the main protein in blood?
albumin; regulates osmotic pressure and binds and transports other molecules in blood
what is the main mineral found in bone?
calcium phosphate
where are ligaments found?
between bone and bone
where are tendons found?
between bone and muscle
where is cartilage found?
between bones and joints
what are 3 types of connective tissues?
- fibroblasts; produce collagen, maintain ECM/material
- adipocytes; storage and metabolism of fat
- mast cells and tissue macrophages; defence and immune function
what is the main property of the muscle tissue?
it’s contractile and can generate force
what do muscle cells look like?
long and thin fibre units (stacked with mitochondria, actin and myosin)
what are 3 types of muscle cells?
- skeletal (moves skeleton/body)
- smooth (no contractile units)
- cardiac (associated with heart and blood vessels, synchronised)
what is the main function of nerve tissue?
integrates communication (receives, generates and transmits information and electrical signal)
how does epithelial tissue maintain the coverage of surfaces? (3)
- no contact inhibition
- cell-cell junctions (cell adhesion)
- cell- ECM junctions
what are cell-cell junctions?
- stick cells together
what is the function of desmosomes? (macula adherens)
- firm anchorage
- localised patches which are attached to intermediate filaments of keratin in cytoplasm
- keep surfaces intact, prevent leaky surfaces
what is another name for tight junctions?
occluding junctions
what is the function of tight/occluding junctions?
- seals intracellular spaces (gaps between epithelial cells)
- waterproof
-whatever is absorbed by cell stays there, ensures max. absorption
-has network of claudins
-prevent migration of floating membrane proteins
“stitched together cells”
what is another name for gap junction?
channel forming junction
what is the function of gap/channel forming junction?
- cell-cell communication
- similar to gap junctions but have small pores/holes for small ion and molecule transfer between cells
- contain rosettes of proteins
what structures are pores found inside in gap junctions?
rosettes (form intercalated discs)
what are pores in gap junctions very sensitive to?
calcium
what is denied access through pores in gap junctions?
large molecules and negative ions
what makes up the intracellular gap in gap junctions?
connexons
how many subunits make up connexons?
6 subunits
where are gap junctions found in larger numbers?
cell which :
-exchange of chemical messengers for cell recognition
-differentiation
-passage of nutrients from cell to cell
-control of cell position
such as cardiac cells where synchronisation is crucial
what are anchoring junctions?
- present in discrete patches holding adjacent cells together
- adherens (zonula adherens) and desmosomes (macula adherens) make it up
- anchorage for cytoskeletons of both cells to form a single functioning unit
what are adherens junctions linked to?
actin skeleton (links it with the cell)
what are desmosomes linked to?
link keratain filaments in to cells
what 2 proteins are found in anchoring junctions?
- cartherines
2. catenins
what are ECM anchoring junctions?
- hemidesmosomes anchor cell to basal lamina (BL)
- membrane integrins linked by hemidesmosomes to BL on basement membrane
what is the basement membrane composed of? (2)
- basal lamina
2. reticular lamina
what is the basal lamina?
- layer of ECM/ basement membrane
- epithelium sits on it
- it’s “fuzzy”
what is the reticular lamina?
- it’s “stringy”
- layer which lies below BL
- anchors BL to underlying connective tissue
what is the basement membrane? (6)
- condensed layer of EC material
- provides support
- binds epithelium to underlying supportive tissue
- controls epithelial growth
- permits flow of nutrients to and from epithelium (since no blood vessels)
- regulates permeability
what is the function of thick epithelium?
wear and tear (e.g. skin)
what is the function of thin epithelium?
diffusion; exchange of materials
what are cillia? (singular: cilium)
- finger-like projections from apical surface
- found on cell surfaces
- beat in wave-like manner generating a current which propels fluid along epithelial surface
- create physical movement
- extensions of the cell, sweep mucus to remove dust e.g. in lungs
what is the microtubule arrangement in cilia?
9+2 arrangement
what are microvilli?
- smaller and thinner than cilia projections found on cells surfaces
- increase and maximise SA for absorption and secretion
- form a “brush border”so metabolites can be easily absorbed
which area of the body has a larger number of microvilli for maximum absorption?
small intestine
what is protein which makes up the microvilli and supports it?
actin
what are properties of squamous epithelium?
- single cell thickness
- used for diffusion of tiny molecules, secretion and absorption
- provide little protection against mechanical abrasion
where is squamous epithelium found?
- air sacks in lungs (alveoli)
- lining of blood vessels (endothelium)
- lining of body cavities (mesothelium)
what are properties of cuboidal epithelium?
- all cells same height and width (squares)
- single cell but standing up
- used for secretion and absorption
- slightly thicker than squamous
where is cuboidal epithelium found?
- small collective ducts in kidneys
- salivary glands
- pancreas
what are properties of columnar epithelium?
- single cell but standing up
- much longer
- used for secretion and absorption
- nuclei elongated and may be found near base, centre or apex of cytoplasm (known as polarity)
- most are ciliated
where is columnar epithelium found?
- small intestine
- stomach (where lots of secretion/absorption takes place)
what does the word stratified epithelia mean?
several layers on top of each other (more than 2 layers)
what are properties of squamous stratified epithelium?
- can withstand abrasion
- poorly adapted for desiccation (extreme dryness)
where is squamous stratified epithelium found? (5)
- oral cavity
- pharynx
-oesophagus
-anal canal
-uterine cervix and vagina
(places which secrete mucus/moist)
what are properties of cuboidal stratified epithelium?
- provides more sturdy lining rather than being involved in secretion/absorption
where is cuboidal and columnar stratified epithelium found?
lining of large excretory ducts of exocrine glands e.g. salivary glands
what are properties of stratified transitional epithelium?
- cells look like frog spawn
- epithelium can accommodate volume and can stretch
- cells are irregular because of constant shape changes
- can withstand large volumes and toxicity
- transitional as it’s between stratified squamous and cuboidal epithelia
where is stratified transitional epithelia found?
found in URINARY system
- cells can withstand volume and toxicity of urine
- found in bladder, urethra and ureters
what are properties of pseudostratified columnar epithelium?
- looks like stratified but it’s NOT
- nuclei found at different levels, tall and columnar
- all cells are found on BL but give an illusion of being stratified- they are NOT
- contain cilia
what 2 characteristics can be used to distinguish between pseudostratified and stratified epithelia?
- pseudostratified exhibit polarity (nucleus found on the basal 2/3 of the cell)
- cillia are never present on stratified epithelia, but found on pseudostratified
what are glandular epithelia? (glands)
- invaginations of epithelial surfaces which are formed during embryonic development by proliferation of epithelium into underlying tissues
- involved in secretion
- more specialised than regular tissue
what is the largest gland in the body?
liver (produces chemicals such as bile)
what is an EXOCRINE gland?
secretes into tubes, closed gaps, lumens, gut surfaces (outside the blood)
what is an ENDOCRINE gland?
secretes into bloodstream/ circulatory system (inside the blood)
