Mm Histology 1 Intro & Epithelia

One of the 4 main classes of tissues (epithelial, muscle, and nervous tissues)

Composed of some cells + A LOT of extracellular matrix

Holds things in place

(ex. fascia, tendon, fat, cartilage, bone, skin, and teeth)

Protein + Carbohydrate mix outside the cell

Provides support to cells

Secreted by the surrounding cells

Different composition in different types of connective tissue

Main structural protein found in extracellular matrix of connective tissue

It is the most abundant protein in mammals

Created by fibroblast cells

Produces and secretes fibers to maintain the ECM

(ex. collagens, reticular fibers, elastic fibers)

Main cells of connective tissue

Cells that line a cavity or the outside of the body

Secrete and absorb things

(ex. nutrients from gut, hormones into the blood via endocrine glands in blood, sweat glands on skin)

Thin layer of extracellular matrix below epithelial cells

Provides support/protection for Epithelia to sit on (above the muscle, fat, etc)

Composed of proteins/carbohydrates (ex. collagen, proteoglycans, and glycoproteins like laminin and fibronectin)

Thin layer of extracellular matrix below the basal lamina

Basal Lamina + Reticular Lamina = "Basement Membrane"

Anchors the basal lamina to underlying connective tissue

Composed mainly of collagen fibers

1. Simple (one layer)

2. Stratified (many layers)

1. Columnar (rectangular)

2. Cuboidal (square)

3. Squamous (flat)

Multiple cells that form "hills" or projections

Increase surface area

Small little projections from individual cells to increase their surface area

Helps them absorb more substances

(ex. found mainly in the small intestines)

The apical surface of some types of epithelial cells that have microvilli

Specialized for absorption (ex. small intestine and kidney)

Simple cuboidal & simple columnar cells

Enzymes responsible for digestion are tethered as integral membrane proteins in the plasma membrane of the enterocyte.

Side of epithelial tissue facing the lumen

Outer layer of epithelial cells in cavities that are exposed to the external environment (ex. esophagus. nasal passage)

Protects and lubricates

A gland found in the epithelial lining of the small intestine and colon

Inlet of lumen between villi covered by epithelium

Contain stem cells, Paneth cells, and goblet cells

Secretes mucous into the lumen

Found in epithelium of the small intestine

In the crypts of Lieberkühn

Helpful in immune defense (secrete anti-microbial compounds to kill bacteria in the intestinal lumen)

Loose connective tissue directly under a mucous membrane

Supports the mucosa and connects the mucosa to smooth muscle

Outermost connective tissue of an organ or structure

A type of epithelial cell that lines the gut

Coat on the outside of cell that is made of carbohydrates

(aka "thin candy shell", like M&Ms)

Found mainly on epithelia & some bacteria

Hairlike fibers on the outside of cell

Made of microtubules

Used to move things along a cavity

Tubes that carry the egg from the ovary to the uterus

This is where fertilization takes place between a sperm and an ovum

Have cilia

Transports saliva from the parotid gland (aka the major salivary gland) to the mouth

Interphase

Prophase

Metaphase

Anaphase

Telophase

+ charge (basic)

Stains things BLUE that are basophilic (have + charge)

ex. nucleus, DNA and RNA

- charge (acidic)

Stains things RED that are acidophilic (have - charge)

ex. cytoplasm, PROTEINS, extracellular fibers (collagen)

Used to detect carbohydrates (purple color)

(Ex. glycogen, glycoproteins, basement membrane GAGS)

Creates aldehydes from OH groups

A mixture of 3 dyes used to distinguish different tissue from each other

(ex. collagen fibers stained blue, nuclei stained black, smooth muscle stained red)

Allows visualization of types of different structures

Specifically for nervous system and reticulin fibers (connective tissue fibers made of type III collagen)

Target tissue appears as black dots

Shows contrast between collagen and other types of tissues

(ex. collagen stains pink, muscle stains yellow)

1. Fixation

2. Dehydration (with ethanol)

3. Clearing

4. Infiltration

5. Embedding (in parafin solution)

Cuts samples thin (to 5 microns)

Condenser – collects and focuses light

Objective – enlarges and projects

image to eyepiece

Eyepiece - further magnification and projection onto retina

Where the membranes of two cells come very close together and appear to be fused.

Create polarity (two different sides of cells), prevent redistribution of the plasma membrane

Act as a barrier so that materials cannot pass between two cells (materials must be regulated by going through the cell)

(ex. in the gut to regulate absorption of digested nutrients)

1. Occludin proteins - 2 intracellular and 2 extracellular domains, involved with the regulation of signaling event

2. Claudins proteins - major structural and functional elements, 2 intracellular and 2 extracellular domains, mediate calcium-independent cell-cell adhesion

3. JAMs - single transmembrane domain

Provide strong mechanical attachments between adjacent cells

(ex. hold cardiac muscle cells tightly together, hold epithelial cells together)

cadherins - transmembrane proteins, extracellular segments bind to each other

Only create adhesion when bound to calcium ion

catenins - connect cadherins to actin filaments

Inherited mutations in a gene encoding a cadherin can cause stomach cancer.

Proteins involved in linking cells to each other extracellularly (like cadherins)

Part of Adherins Junctions

Localized patches that hold two cells tightly together

Appear as thickened patches in the cell membrane region between two cells

Cadherins attach to cytoplasmic plaques that are attached to intermediate filaments (ex. keratin)

Similar to desmosomes but attach epithelial cells to the basal lamina instead of to each other.

Intracellular plaque is attached to integrins

Integrins - mediate cell-ECM interactions with collagen, fibrinogen, fibronectin, and vitronectin.

Provide essential links between the extracellular environment and the intracellular signalling pathways

Play roles in cell behaviours such as apoptosis, differentiation, survival, and transcription

Consist of an alpha and beta subunit, each have a large extracellular domain, a transmembrane domain and a short cytoplasmic domain

Intercellular channels that permit the free passage between of ions and small molecules between cells

Constructed from connexins.

Permit changes in membrane potential to pass from cell to cell (ex. the action potential in cardiac muscle flows from cell to cell through the heart providing the rhythmic contraction of the heartbeat)

1. Delivery of Proteins (to apical, basal, and lateral areas)

2. Selective Retention, Destruction of Proteins on Apical or Basal Surface

3. Cell-Cell Junctions

AA sequence on the carboxyl end of a protein that is the signal to send it to the APICAL membrane

These proteins lack transmembrane domains, so they must be associated with lipid or other membrane domains

Bringing proteins from the basal to the apical membrane

Ex. immune system antibodies

Mechanism is unclear, but probably doesn't involve a lipid raft

Sequence on a protein to tell it to go to the basal membrane

They stick out of golgi vesicles and bind to adaptor proteins (multi domain, MU domain binds to the XXY region & Beta domain binds to clathrin coating protein)

Clustered in vesicles surrounded by a coat of adaptor proteins and associated clathrin.

A cluster of nearly 10 proteins which attaches the vesicle to the basolateral membrane.

The vesicle goest to the BL membrane, uncoats its clathrin, and interacts with the exocyst

This permits v-snare and t-snare to attach and vesicle to fuse so the protein gets put into the basolateral membrane

When two cells touch (called a kiss "kiss"), the membrane zone where they meet is very different than the free areas.

When claudins or occluding from different cells are touching, this connection is then built upon by additional claudins and occludins in the interacting cells and they form a plaque of claudins and occludins.

This zone recruits more proteins to aggregate at the site of contact within each cell

(ex. claudin and occluding zone = cytoplasmic plaques of Zo-1, Zonab, cyclins and cytoskeleton)

Adhesion junctions of cadherins also create homotypic patches on the cell membrane (ex. beta-catenin-alpha-catenin-actin filaments organized at those spots)

Polymeric IgG receptor = a membrane protein at the basal side of the membrane that binds antibodies (being made by lymphocytes that underlie our epithelial layers)

These antibodies give us what is called “mucosal immunity”

The PIGR binds these antibodies and transcytoses them to the apical lumen, where it is cleaved

This means that full length PIGR is found only at the basal surface and hence appears to be apically distributed.

The tight junction forms a “fence” so that the proteins in the lipid membrane cannot undergo lateral movement

The claudins and the occludins block the flow of membrane proteins across their high density zone

Apical remains apical, and basal remains basal

Pars are the regulators of the proportion of the membrane that is apical to the portion of the membrane which is basalolateral.

Par-1 gets phosphorylated by Par-6 and unites with "helper" Par-5

Phosphorylated Par-1along with "helper" Par -5 go to basal space and free Par-3 from the basal part of the tight junction (by Par-1 phosphorylating it too)

Phosphorylated Par-3 then goes with "helper" Par-5 up to the apical side of the tight junction

Hence stimulation of Par1 reduces basolateral Par3 and hence blocks basolateral phenotype, permitting an apical phenotype

Adhesion junctions contain a reservoir of beta-catenin

When this protein is released into the cytosol it is degraded by APC

If APC is inhibited by Wnt signaling, then excess beta catenin heads into the nucleus and turns on a 1000 genes

This event is the most important signaling in developing stem cells

Proteins by endocytosis of vesicles coming from the apical membrane

Ions/Water across carriers or channels (simple or facilitated diffusion)

Ions by ATPase

61 log (inside/outside)

Then all you do is compare this to the voltage gradient and use reason to figure out which way each push is sending them

Add or subtract accordingly

Apical side is much more negative than the basal side, but still more positive than the cell