Epithelia Flashcards by Berina Karisik

What are some characteristics of epithelia?

Cellularity, polarity, attachment, avascular, innervation and regeneration

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What is the basement membrane?

A thin extracellular, felt like sheet of macromolecules that epithelial tissue rests on

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Epithelium that is primarily involved in secretion is often arranged as what?

Glands

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What are the three surfaces of an epithelium that create its polarity?

Apical, lateral and basal

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What makes epithelium have polarity?

Organelles and proteins are unevenly distributed

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What is the apical surface?

Exposed to the lumen of a tube or external environment

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What is the lateral surface?

Right or left surface of the cell and can be attached

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What is the basal surface?

Attached to underlying basement membrane and on the opposite side of the lateral surface

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What are tight/occluding junctions?

Impermeable junctions that allow cells to function as a barrier
Encircle cells near most apical surface

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Which proteins are involved with tight/occluding junctions?

Occludins and claudins

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What are gap/communicating junctions?

Fluid filled channels that connect apposed cells

Proteins: connexin aggregates

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What are the three main examples of anchoring junctions?

Adherens, desmosomes and hemidesmosomes

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What are adherens?

Lateral adhesins involving cadherin:actin filament interactions

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What are desmosomes?

Lateral adhesins involving cadherins:intermediate filament interactions

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What are hemidesmosomes?

Basal adhesions involving integrins:intermediate filament interactions

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What is the clinical relevance for tight junctions?

Bacteria that causes food poisoning target TJs in the intestine —> impairs junctions —> loss of tissue fluid into intestinal lumen
Helicobacter pylori causes gastric ulcers —> binds TJs in the stomach, increasing permeability

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What is the clinical relevance for desmosomes?

Autoimmune disease pemphigus vulgaris -> abnormal desmosome function -> reduces cell to cell adhesion -> blisters of oral mucosa

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What is the function of the basement membrane?

Selective barrier between tissues that permits diffusion of nutrients

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What are microvilli?

Cytoplasmic processes containing an actin core
Specialized for absorption
Number and shape correlate to the cell’s absorptive capacity

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What is the clinical importance for microvilli?

Celiac disease -> loss of microvilli on absorptive cells in the SI

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What are stereocilia?

Microvilli of an unusual length
Long and less mobile with an actin core
Increased surface area for absorption/secretion
Restricted location: epididymis and hair cells of inner ear

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What are cilia?

Long highly motile structures containing internal arrays of microtubules
Can be motile, primary or nodal

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What are motile cilia?

Beat in a wave like fashion to propel substances across the tissue

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What are primary cilia?

Immotile, function as chemosensors, osmosensors and mechanosensors

What are nodal cilia?

Embryonic | Have a role in L/R axis determination

What is the location of simple squamous epithelium?

Lining of blood and lymphatic vessels (endothelium), lining of serous membranes (mesothelium), lining of alveoli in lungs, loop of Henle in kidney and various ducts

What is the function of simple squamous epithelium?

Exchange, barrier and lubrication

What is the location of simple cuboidal epithelium?

Kidney tubules, glands and associated ducts, terminal bronchioles and covering of the ovaries

What is the function of simple cuboidal epithelium?

Absorption, barrier and secretion

What is the location of simple columnar epithelium?

Auditory tubes, uterus, oviducts, stomach, SI/LI and gallbladder

What is the function of simple columnar epithelium?

Absorption and secretion

What is the location of pseudostratified ciliated columnar epithelium?

Lining of nasal cavity, pharynx, trachea and bronchi

What is the function of ciliated pseudostratified columnar epithelium?

Absorption, secretion, debris and particular movement

What is the location of urothelium?

Urinary bladder, ureters and urethra

What is the function of urothelium?

Barrier and distensible property

What is the location of nonkeratinized stratified squamous epithelium?

Oral cavity, portion of the pharynx, esophagus, anus, vagina, urethra, cornea

What is the function of nonkeratinized stratified squamous epithelium?

Barrier and protection

What is the location of keratinized stratified squamous epithelium?

Epidermis of the skin

What is the function of keratinized stratified squamous epithelium?

Barrier and protection

What is the location of stratified cuboidal columnar epithelium?

Sweat glands and ducts, ovarian follicles, salivary gland ducts

What is the function of stratified cuboidal columnar epithelium?

Barrier and passageway

What are mucous membranes?

Epithelial tissue that secretes mucus | Lines many body cavities and tubular organs including the gut and respiratory passages

What are serous membranes?

Epithelial tissue that lines internal body cavities Forms a smooth, transparent, two layered membrane Lubricated by a fluid derived from serum Includes the peritoneum, pericardium and pleura

What is mesothelium?

Simple squamous epithelium that comprises part of a serous membrane**

What are unicellular glands?

Single, secretory cells distributed among non-secretory cells

What is a goblet cell?

Mucus secreting cell lining the intestines and respiratory tract

What are exocrine glands?

Multicellular glands comprised of secretory cells grouped as an acinus Produced is secreted into a system of ducts for release

What is parenchyma?

Functional tissue of an organ (not the CT and other supporting tissues)

What is stroma?

CT support of secretory units

What is septa?

Partitions the exocrine gland into separate lobules | May enclose the entire gland as a capsule

What is merocrine secretion?

Secretion is delivered in a membrane bound vesicle to the apical surface and undergoes exocytosis

What is holocrine secretion?

Secretion accumulates within the cell —> apoptosis | Secretion and cell debris are released

What is apocrine secretion?

Release of apical portion of the cell, surrounded by cytoplasm within a plasma membrane

Glands can be classified into what?

Simple (unbranched ducts) or compound (2+ branches)

What are compound glands?

Can have branching ducts with numerous secretory portions (tubular, acinar and tubuloacinar)

What is a compound tubular gland?

Coiled secretory portion

What is a compound acinar gland?

Saclike secretory units

What is a compound tubuloacinar gland?

Tubular and acinar secretory units

What are the secretory portions of a gland?

Tubular or acinar | May be branched even if duct is not