Flashcards in Epithelial Tissue & Cell Junctions Deck (69):
Epithelial Tissue Properties
1. Intercellular Space
2. Intercellular Junctions
3. Intermediate Filament: Keratin
4. Regenerate when injured
5. Avascular & Non-nervous
6. Basement Membrane
7. Exhibit Polarity
9. Derived from all germ layers
Change in epithelial cell structure due to chronic condition
Lining of GI tract derivation
1. Zonula Occludens
2. Zonula Adherens
3. Macula Adherens
4. Nexus/Gap Junctions
1. Basement Membrane
2. Focal Adhesions
4. Basal Membrane Infoldings
First from the top in Lateral Domain.
Includes JAM, occludin, claudin, ZO-1, ZO-2, ZO-3, and actin
Surrounds the entire perimeter of the cells
Intra-membranous sealing strands occlude the space between cells; confers epithelial tightness or leakiness; establishes functional domains in the plasma membrane
Form backbone; form extracellular aqueous channels for the paracellular passage of ions and other small molecules.
Maintain barrier between adjacent cells as well as barrier between apical and lateral domains.
Present in endothelial cells; mediates interactions between endothelial cells and monocyte adhesions.
Mutation in gene encoding claudin-14
Increased permeability of ZO in organ of Corti which decreases generation of action potentials causing hereditary deafness.
Cell Adhesion molecules
Cadherins- calcium dependent transmembrane proteins
Integrins- calcium independent transmembrane proteins
Cell membranes separated by an intercellular space which is larger than zonula occludens.
Extends around the entire perimeter of the cell
Actin filaments are linked by alpha-actinin, vinculin, and catenin to E-cadherin (calcium dependent)
1. Mechanical Stability-cohesive function of cell groups
2. Regulate differentiation, migration, proliferation, morphogenesis (formation of tubes, embryonic folding, etc.), and survival of epithelial cells
Cell membranes separated by a wider intercellular space than ZA
Occurs at small discrete sites-spot welds
Link cytokeratin (intermediate) filaments to desmogleins & desmocollins
Linkage through plaque proteins (Desmoplakins & Plakoglobins)
1. Provide high tensile strength and resist shearing forces
Autoantibodies against desmogleins causing painful flaccid blisters in oropharynx and skin
Effects people over 40 and results in dysfunctional desmosomes or macula adherens
Important in tissues in which activity must be coordinated:
1. Epithelia engaged in fluid and electrolyte transport
2. Vascular and Intestinal Smooth Muscle
3. Heart Muscle
Nexus/Gap Junctions Features
1. Nutrients and signal molecules may be transported between cells without loss of material into the intercellular space.
2. Cell membranes of two adjoining cells are separated by an intercellular space bridged by connexon (individual unit of a gap junction)
3. Each connexon is formed by 6 Gap Junction Proteins Connexin
4. Connexons contain central pores that allow passage of molecules with molecular mass < 1500 Da
Tissues affected by mutation in genes encoding for connexin
1. Cardiac arrhythmias
2. Slower conduction of nerve impulses
3. Decreased peristalsis in the small intestine
4. Inefficient glycogenolysis
5. Congenital Deafness (Cx26)
6. Inherited Cataract (Cx46 & Cx50)
1. Infoldings of lateral membrane
2. Localized Na+/K+ ATPase
3. Important in epithelia engaged in fluid and electrolyte transport (eg small intestine)
1. Heterotypic interactions
2. Interact with ECM molecules (such as collagens, laminin, and fibronectin) & with actin and intermediate filaments of the cell cytoskeleton
3. Regulate cell adhesion, control cell movement and shape, and participate in cell growth and differentiation
Create a dynamic link between the actin cytoskeleton and ECM.
1. Molecular basis for cell migration
2. Mechanosensitivity- sensing and transmitting signals from the extracellular environment into the interior of the
1. Occurs in the cornea, the skin, and the mucosa of the oral cavity, esophagus, and vagina - epithelia subject to abrasion and mechanical shearing forces
2. Link intermediate filaments in cell to ECM
3. Intracellular Attachment Plaque-major proteins-Plectin, BP 230 (BPAG1), Erbin
4. Transmembrane Proteins belong to integrin family - a4B6 integrin, Collagen Type XVII, CD 151
5. Type XVII collagen (BPAG2, BP 180) - regulates expression and function of laminin-5
Dermo-epithelial separation are antibodies against integrin causing blisters - think basal effect
Causes blisters that are less likely to erupt because they are deep
Autoantibodies against hemidesmosomal proteins BP230 and BP180
Causes widespread blistering with pruritus
Basement Membrane Staining
H&E stain does not show BM
PAS staining stains carbohydrates and shows BM
Basal Lamina vs. Basal Membrane
Basal Lamina includes lamina densa and lamina rara/lucida
Basal Membrane includes lamina densa, lamina rara/lucida, and reticular fibers
Clinically there really is no difference
Basement Membrane Zone
Important clinically as it contains:
1. Anchoring Plaque (Collagen type IV)
2. Anchoring Fibrils (Collagen type VII)- communicate with ECM and anchor cell
Basal Lamina Molecular Components and Functions
1. Collagen, Type IV: Insoluble structural support
2. Heparan Sulfate (Proteoglycan): Most common in basal lamina is perlecan. Confers electrostatic charge.
3. Laminin (Glycoprotein): Bridge between the cells & Type IV Collagen; Possess binding sites for different integrin receptors
4. Entactin/Nidogen (Glycoprotein): Bridge between two networks: Laminin and Type IV Collagen
Collagen in Basal Lamina
1. Type IV, major type: Insoluble structural support, forms scaffold
2. Type VII: Forms anchoring fibrils that link the basal lamina to the underlying reticular lamina
Basal Lamina Functions
1. Structural attachment-cells to adjacent CT
2. Compartmentalization-isolate the connective tissue from epithelia, nerve, and muscle tissues
3. Filtration- Movement of substances to and from the CT is regulated in part by the basal lamina, largely through ionic charges and integral spaces
4. Tissue Scaffolding-Serves as a guide or scaffold during regeneration
5. Serve as pathways for cellular migration but act as barriers against tumor cell invasion
6. Regulate cell shape, proliferation, differentiation, and motility as well as gene expression and apoptosis during morphogenesis, fetal development, and wound healing
Epidermolysis Bullosa Dystrophica
Type VII Collagen Gene Mutation
No anchoring fibrils- dermal-epidermal separation
Basement Membrane Zone separation
Results in scarring
Invagination of the Cell Membrane-increase surface area
Numerous Mitochondria, Provide Substrate ATP
Contain Ion Pumps (Na+/K+ ATPase)
Predominate in cells involved in active transport- PCT, DCT, ducts of salivary glands
Shelf like cristae
Hair-like extensions of the apical plasma membrane- seen mostly in pseudostratified epithelium
Much taller than microvilli
The internal core of microtubules in cilia
Hold cilia in place in apical domain. A centriole-derived, microtubule organizing center (MTOC)
2. Basal body
3. Radial Spoke-connect peripheral to central microtubules
4. Nexin-between peripheral microtubules
5. Dynein arms-site of energy in cilia (ATPase)
1. The axoneme consists of 9 doublet microtubules uniformly spaced around 2 central microtubules. (9+2)
2. Nexin connects the 9 doublet microtubules. It keeps the doublets from moving away from each other independently.
3. Each doublet has short arms that consist of dynein ATPase, which splits ATP to provide energy.
4. These are inserted into basal body that consists of 9 triplet microtubules and no central microtubule (9+0).
5. Ciliary action results from bending of the doublets first in one direction and then in the other and is fuelled by dynein-catalyzed conversion of ATP to ADP.
6. Ciliary movement is frequently coordinated to permit a current of fluid or particulate matter to be propelled in one direction over the epithelial surface.
7. These form the core of flagella (eg tails of spermatozoa).
1. Non-motile; known as monocilia because each cell usually possesses only one.
2. Core of microtubules arranged in 9+0 pattern.
3. Important cellular-signaling devices; function as signal receptors sensing chemical, osmotic, light, and mechanical stimuli from external environment.
Mutations in genes ADPKD1 and ADPKD2
Affect development of primary cilia leading to polcystic kidney disease (PKD). The proteins encoded by these genes, polycystin-1 and polycystin-2, respectively, are essential in the formation of the calcium channels associated with primary cilia.
1. Motile/Active rotational movement
2. Core of microtubules arranged in 9+0 pattern with motor proteins.
3. Observed in embryos - establish the left-right asymmetry of internal organs.
Mutation in dynein causing absence of dynein
Nodal cilia defect
2. Situs inversus
3. Recurrent Respiratory Tract infections
Finger-like cytoplasmic projections
Found mostly in epithelia specialized for absorption
LM: striated or brush borders
The number and shape correlate with absorptive capacity
Cytoplasmic core of microvillus which insert into the terminal web
Specialization of actin cytoskeleton lying immediately beneath the cell surface.
Microvillus inclusion disease
Inclusion containing microvilli within apical cytoplasm of the cell
MYO5B gene mutation resulting in zero absorption
infantile diarrhea which is life threatening
life span is 3-20 years which does require a transplant
Total parenteral nutrition (TPN) needed
Act more like microvilli
unusually long, immotile microvilli
Epididymis - facilitate absorption
Inner Ear - Sensory Mechanoreceptors
Core - actin microfilaments
Epithelial Tissue Functions
4. Contract (Myoepithelial cells)
5. Sense (Olfactory)
2. Blood Vessels
3. Body Cavities
5. Loop of Henle
1. Thyroid Gland
1. GI Tract
2. Gall Bladder
4. Uterine Tubes
1. Respiratory Tract
3. Vas Deferens
1. Epidermis of Skin
1. Oral Cavity
4. Anal Canal
1. Large Ducts of Exocrine Glands
1. Male Urethra
2. Urinary Bladder
Glandular Epithelium Types
1. Exocrine (into duct)
2. Paracrine (local factors)
3. Endocrine (into blood stream directly)
Exocrine Gland Types
2. Unicellular- Goblet cells are only unicellular exocrine glands (Respiratory and GI tract)
Exocrine Glands Release Mechanisms
1. Merocrine- cells secrete in a common lumen and through the duct spread out (exocytosis)
2. Holocrine- Disintegrating cells with contents becoming the secretion
3. Apocrine- Pinching off of apical portion of secretory cell (mammary glands and sweat glands)
Exocrine Glands Type of Secretion
1. Serous cells are smaller, dark staining and more basophilic than mucus cells. They produce secretion which is thin, watery, and rich in enzymes (protein).
2. Mucus cells produce viscous and slimy secretions, rich in PAS +ve mucinogen (heavily glycosylated protein) granules. Mucins, outside the cell, are hydrated to form mucus.
Protein Secreting Cell
1. Perinuclear rER
2. Golgi Complex
3. Apical Secretory Granules
1. Enzymes-gastric chief cells; pancreatic acinar cells
2. Albumin; hepatocytes
3. Hormones; chief cells: Parathyroid
Polypeptide (Hormone) Secreting Cell
1. Perinuclear rER
2. Golgi Complex
3. Basal (toward blood vessels) secretory granules
1. Glucagon- a-cells, Pancreatic Islets
2. Insulin- B-cells, Pancreatic Islets
3. Gastrin- G-cells, Pancreatic Islet; Stomach; Small Intestine
4. Somatostatin- gamma-cells, Pancreatic Islet; Stomach; Small Intestine
Steroid Secreting Cell
2. Lipid droplets
3. Mitochondria- tubular cristae instead of shelf-like
1. Testosterone- Leydig Cells, Testis
2. Estrogen- Follicular Cells, Ovary
3. Progesterone- Corpus Luteum, Ovary
4. Cortisone and Aldosterone- Adrenal Cortex
Epithelial Cell Highly Specialized for Absorption + Active Transport
Microvilli + numerous mitochondria in basal folds
Epithelial cells highly specialized for contraction
1. Finger-like processes that embrace an acinus or duct; contraction expels exocrine products.
2. Lie between the epithelial cells and their basal lamina.
3. Cytoplasm contains microfilaments, myosin, tropomyosin, and cytokeratin intermediate filaments.
4. Occur in lacrimal, salivary, mammary, and sweat glands.
1. Light-staining, Foamy Appearance (Mucus-containing Apical Vesicles)
3. Predominantly Acidophilic Staining with H&E
4. A Large Supra-nuclear Golgi Complex
5. Nuclei and sparse RER in the Base
1. Mucin- Goblet cells; Secretory Cells of Sublingual & Submandibular Salivary Glands