Week 5 Epithelium Flashcards
Most common histological stain
H & E
Hematoxylin, a basic, cationic stain that stains acidic/basophillic structures blue/purple. Examples include nuclei, ribosomes, and DNA, rough Er.
Eosin is an acidic/anionic stain that stains basic/acidophilic structures pink.
Main qualities of epithelial tissues
Distinct polarity (apical and basilar domains)
Rapid renewal (epidermis: 15-30 days. Cornea: 7 days)
Typically avascular, which a vasculature supply nearby.
Functions as a barrier, protection, to absorb nutrients and secrete hormones, enzymes, and mucous.
Apical epithelium features- microvilli.
Small, not seen by a Light Microscope. They increase the surface area of the epithelium by 30x. They are specialized for absorption and the core contains actin filaments (contractile).
Seen in the brush border of the small intestine.
Apical epithelium features- cillia.
Long, motile structures that can be seen using a light microscope.
Formed from microtubule doublets and are ATP dependent motor proteins.
They propel surface mucous and fluids. They beat in rhythmic pattern and are found in the respiratory tract and female reproductive tract.
Basolateral cell features- cell junctions.
- Tight/occluding junctions
-Zonular occludens (ZO) - Zonular ahderens
-Belt junctions. Adherent to actin cytoskeleton. - Communicating junctions
-Gap junctions, cell-cell communication - Desmosome
-Cell to cell junction with intermediate filaments - Hemidesmosome
-Cell to basal laminal junction
Intermediate filaments
Basal epithelial features
Infoldings/invaginations. Increase surface area for ion transport + mitochondria.
Role of the basement membrane
Separates and anchors epithelium from the underlying connective tissue.
Structure of the basement membrane
Bi layered.
Basal lamina (outer lamina lucida, inner lamina densa)
Inner connective tissue like layer (lamina reticularis) ***Not actually connective tissue
Thickness depends on location, presence/abselce of disease.
Tight junctions
Most restrictive. Adhere cells together along the apical/luminal border, which forms an epithelial sheet and selective barrier.
Direct connection between adjacent cells, linked by actin cytoskeleton.
Facilitate boundary gradients across epithelial tissues
-Zonular adhering or belt junctions.
Bladder, intestine, secretory glands, cornea
Cadherins
A specialized form of an adheren.
A transmembrane protein that are linked to cell’s actin cytoskeleton Cadherins of one cell bind to the catherine of another cell. They are often continuous and form a belt around the cell.
Actin microfilament contraction can create cell membrane invaginations during development.
Desmosomes
Anchor epithelial cells to one another. Bind identical catherine of adjacent cells. Plaques linked between cells are anchored to cytoplasmic intermediate filaments.
Hemidesmosomes
Anchor epithelia to the basal lamina.
Integrins bind to laminas of the basal lamina.
Linked to the intermediate filaments within the cytoplasm.
Types of simple epithelial tissue types
Squamous, cuboidal, columnar, pseudostratified columnar
types of stratified epithelial tissues
Squamous Keratinized (SSK), Squamous non keratinized (SSNK), columnar, and cuboidal
Transitional epithelial types
Non-distended (not stretched) and distended (stretched)
Cell shape, purpose and examples of simple squamous
Flattened, single layer, tightly packed.
Rapid diffusion of gases or fluids through.
Lines blood and lymphatic vessel walls, pleural and abdominal cavities.
Found in kidney (nephron loop, bowman’s capsule), pulmonary alveoli.
Body cavity membranes: Mesothelium (pericardium, pleura, and peritoneum) **
Superficial lining of blood lymph endothelium conduits.
Cell shape, purpose and examples of simple cuboidal
Cube/polygon shaped single layer of cells.
Primary function: secretion and absorption.
Line ducts of smaller glands such as the kidney tubules, mammary glands, sweat gland ducts.
Cell shape, purpose and examples of simple columnar without cilia
Rectangular shape, single layer, variable in height, nuclei often aligned basally.
Primary function: absorption, secretion.
Lines much of Gi tract- stomach, intestines, and gall bladder.
Cell shape, purpose and examples of psuedostratified columnar
All cells rest on basal lamina with only some cells reaching the surface- nuclei are not aligned. Typically ciliated.
Primary function: Conduction, protection, secretion (goblet cells)
Lines much of the respiratory tract- nasal cavity, trachea, bronchi.
Cell shape, purpose and examples of Stratified squamous non keratinized (SSNK)
Flattened superficial cells (with nuclei)
Examples include the cornea, mouth, esophagus and vagina
Cell shape, purpose and examples of stratified squamous keratinized (SSK)
Flattened superficial cells (without nuclei). Basal layers mitotically active; cells migrate towards the surface and lose organelles before being shloffed off.
Examples include the epidermis of the skin.
Cell shape, purpose and examples of stratified cuboidal
Layers of cube shaped cells. 2 layers indicate TRUE stratified cuboidal. (5-6 layers indicate transitional)
Primary function: absorption, secretion
Lining ducts of large glands, such as sweat glands and salivary glands.
*Simple cuboidal plays a bigger role.
Cell shape, purpose and examples of stratified columnar
Layers of rectangular shaped cells. This is a rare, transitional tissue. Conjunctiva of the eye.
Cell shape, purpose and examples of transitional epithelium
Found in urinary tract. Large dome shaped cells when bladder is empty, flattened when bladder is distended.
