Lec 1 Epithelia Flashcards
What kind of dye is hematoxylin
What cell components can it attract
Hematoxylin is a basic dye. (blue)
It attracts acidic molecules like DNA, RNA and ribosomes.
We will see these stain blue.
What kind of dye is Eosin
What does it stain.
Eosin is a acidic dye. Stains basic molecules like proteins.
Pink color
What is the epithelium on the outer surface called.
Epidermis
What is the name for the epidermis and its connective tissue
Cutaneous membrane - Skin
What are internal body surface (passageways open to the outside) epithelia + CT called.
Mucosal membrane
What is epithelium lining vessels - vein, arteries, heart, lymphatic vessels
Endothelium
What is the epithelium lining body cavities that doesn’t open to the outside.
Mesothelium - for pleural, peritoneal, pericardial cavities
For mesothelium, what is it when combined with CT. Name 3
Serous membrane - pleura, pericardium, peritoneum
Epithelia characteristics (6)
- Cellularity - densely packed
- Polarity - has func and struc different sides - basal, lateral, apical
- Intercellular junctions - diff connections btwn cells
- Basement membrane
- Regeneration
- Avascular but Innervated - no blood vessels/flow, but gets stuff by diffusion and has stuff coming from the CT through the BM
Basement membrane properties, origin and its func
Acellular layer made of cell products made from secretion from both the epithelial and CT layers
FUNCS:
1. structural support
2. attachment (contacts btwn epi, BM and CT)
3. semipermeable molecular filter(epi is avascular so metabolites need to be exchanged thru the BM
4. Provides scaffolding for repair and regen of epithelium
Epithelial functions (4), What determines its function
- Physical protection - barrier to dehydration, microbial attack, abrasion
- controlled permeability - ANYTHING substance that crosses into body must cross a epithelium (trans, para and molecular transport)
- Provides sensation - touch, temp, vision, hearing, balance, smell
- produce specialized secretions - sweat, hormones … from glandular epi
FUNC is determined from the requirements of its LOCATION
What is the development order for epithelia
All starts off as a simple epi, then can remain a simple or become stratified or for a gland ( exocrine, endocrine)
What does multicellular glands structure consist of
Duct and secretory portions
What are the different EXOCRINE glands by SECRETION type
Mucous glands - secretes mucinogens
Serous glands - secretes a protein-rich, watery soln
Mixed seromucous glands - population of both types
What are the different EXOCRINE glands by MODE OF SECRETION
Merocrine - secretory product released by exocytosis
Apocrine - Some cytoplasm released with product, apex of cell gets packed with vesicles and then pinched off
Holocrine - entire cell sheds into the lumen of the exocrine glands
Explain Goblet cells
Unicellular exocrine glands found spread out in epithelial cells - produces mucinogens
Secretes out the APICAL end
Where are multicellular endocrine cells found and where does it secrete into
In CT where they lose attachment to the epithelium
Ductless, secretes into interstitial fluid to be taken up and delivered in blood
What does UNIcellular endocrine cells exist as?
What do they do
In some covering epithelia as Diffuse Neuroendocrine cells and in digestive tract as Enteroendocrine cells
Secrete into underlying BM tissue fluid, Can be used for paracrine or systemic sig
What is the size and number of microvilli proportional to
Proportional to the rate at which molecules move
What specialization of the apical surface microvilli provide
Increase surface area that func in absorption and secretion
- nutrients absorbed thru apical side of epithelia and then into BM and CT where blood picks it up
- well developed in SI and kidney
- minimally motile
- actin core and terminal web
What is cilia specialized for on the Apical surface
Where is it found
Specialized to move fluid along the luminal surface
Highly motile and synchronized
Core of microtubules, dynein proteins
Highly developed in respiratory and uterine tube epithelia
What are the functional classes of intercellular junctions(3)
Anchoring junctions - provide mech strength, connects cytoskeleton of epi cells and to BM
Occluding junctions - blocks intercellular spac, controls paracellular movement
Communicating junctions - controls ionic/ molecular movement, pores connecting adjacent epi cells
What does the zonula adherins do
Where is it well developed
Surrounds cells and bind them together (Beers plastic)
ZA links the actin microfilament cytoskeleton between cells - transmembrane protein Cadherins links across the IC space where proteinaceous plaques (catenins and Vinculins) connect Cadherins to the actin
Well developed in the SI
What does desmosomes do, how are they similar or different to zonula adherins
Desmosomes links cells together
Links though Intermediate filament cytoskeleton (different from ZA - actin cytoskeleton)
Links with Cadherins though the IC space (same as ZA)
What does Desmosomes function where is it found most
Distributes sheer forces
Found in skin
What is the role of Hemidesmosomes, what links does it make, where is most common
Anchors epithelia to underlying tissue
Links cytoskeletal IF (keratin) in epi cells across the basal surface to the BM (common in skin)
Integrins - transmembrane proteins that bind from basal epi to molecules of BM (across EC space)
What kind of cellular movement does TIGHT junc control
paracellular movement
What glycoprotein is in tight junctions
Integral transmembrane protein CLAUDINS
Forms branching anastomosing strips
What is arranged belt like, another name for tight juncs
Zonula occludens
What is the tight junction a important part of
What is it important for in terms of actively transported molecules
BBB, Blood testis barrier, Blood thymus barrier
Prevents back diffusion, important for creating gradients
What is the gap junc made of, where are they located
What does it function to do
Connexons - made of 6 connexins
Found on lateral cell membranes
Connect cytoplasm of adjacent cells, couples cells metabolically and electrically (movement of ions and molecules) - ensures synchronous movement
What are characteristics of simple squamous epi
Where and in what tissues/epithelium would we find this
Thinness promotes rapid and passive diffusion of molecular transport
Found in Alveoli, endothelium, mesothelia
What type of cell and what type of epithelium is on the luminal side of alveoli
What about blood vessels
In alveolar apical side - lined with simple squamous epithelium called pneumocytes
In blood vessels are endothelium - simple squamous epi
What are simple cuboidal epithelium designed for
Lines surfaces involved in ACTIVE processes of secretion and absorption
- may have microvilli to facilitate the rate of molecular transport
(Proximal convoluted tubules, kidney)
Simple columnar importance and function
lines surfaces involved in HIGH rates of absorption and secretion - SI - has microvilli and goblet cells, gall bladder- microvilli
ALSO in fallopian tubes with cilia
What is the function of simple columnar epithelia in the GALL BLADDER
The concentrate the bile that is stored. Occurs by actively transporting water out of the lumen into the CT
Has tight junctions btwn the cells to prevent passive back diffusion of water
Where to find pseudostratified epithelium
Found in respiratory tracts, and is usually ciliated and contains goblet cells to clean air before the exchange
What is the role of stratified squamous non-keratinized epithelium
where find
Protects INTERNAL surfaces from abrasion, pathogens, chemical dmg
BUT NOT from dehydration - must be kept moist by glandular secretions
Found in mouth, anus, vagina, esophagus
What cell junction does stratified squamous non-keratinized epithelium has that help it with abrasive forces
desmosomes
What is the role of stratified squamous keratinized epithelium, where find
protect from EXTERNAL abrasion, chemicals, pathogens AND prevents dehydration
Found in SKIN
What is keratinization
Surface cells converted into a sheet of dead protein packed and is strongly interconnected by desmosomes
Roles of Transitional epithelium
Where find
Lines surfaces that requires to be stretched and allow recoil
Urinary bladder and Ureter
