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Microanatomy > Epithelium > Flashcards

Epithelium Flashcards

1
Q

Tissue

A

Aggregation go cells and extracellular substances

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2
Q

Four basic tissue types

A

Epithelial tissue
Connective tissue
Muscular tissue
Nervous tissue

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3
Q

Epithelium

A

A tissue composed of closely aggregated cells with very little extracellular substance.
3 types: Lining, Glandular, Special

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4
Q

Lining Epithelium

A

Form sheets that cover body surfaces or line luminal organs, tubular structures, and body cavities

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5
Q

Glandular Epithelium

A

have specialized cells that synthesize, story, and release various products

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6
Q

Special epithelium

A

Contain sensory nerve endings; found in the skin, ears, and on the tongue; (in nose and eyes there are modified neurons)

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7
Q

Origin

A

Ectoderm –> epidermis of skin
Mesoderm –> mesothelium (lining of body cavities), endothelium (lining of vessels and heart chambers)
Endoderm –> epithelial lining and glands of most of the GI tract, including liver and pancreas, of the respiratory system; of the urinary bladder

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8
Q

Functions of epithelial tissues

A

Protection (epidermis of skin)
Friction reduction (lining of the lumen of blood vessels and of the heart chambers)
Cleaning (internal lining of airways)
Diffusion (lining of the lumen of capillaries)
Absorption (special lining of the small intestine)
Secretion (glandular epithelia in glands)
Sensation (specialized epithelial tissue containing sensory nerve ending convey sensations from the skin, ear, and the tongue)

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9
Q

Characteristics of epithelium

A

Is a tissue with high cellular density and very little intercellular substance
Is closely associated to supporting connective tissue (CT) via basement membrane
Lining epithelium is avascular, with few nerve endings
Epithelial cells are polarized
Epithelial cells are cohesive

Epithelia are constantly renewed by a cycle of cell division

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10
Q

Low cellular density

A

Connective tissue
Lots of intracellular matriculates
Few cells

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11
Q

High cellular density

A 
Hepatic tissue (glandular epithelium)
Little intercellular matrix
High cellular density
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12
Q

Interface with CT and basement membrane

A

Epithelial and connective tissue are interfaced by an extracellular basement membrane
Small blood capillaries never enter an epithelium across it, a few nerve ending do
Usually not visible under light microscopy
Stains prominently with PAS for carbohydrates

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13
Q

Epithelial cells have

A

Apical surface
Lateral surface
Basal surface

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14
Q

Epithelial cells are cohesive

A

Epithelial tissues are subject to pressure and traction have marked intercellular adhesion
Cohesivness due to transmembrane glycoproteins, E-caherins
Folds of plasma membranes between neighboring cells form intercellular junctions

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15
Q

Three types of intercellular junctions

A

Tight junctions
Desmosomes
Gap junctions

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16
Q

Gap junctions

A

Provide cytoplasmic channels or tunnels from one cell to an adjacent cell
Consist of special membrane proteins that surround a pore, through which ions, sugar, amino acids, and other small molecules may pass
Are necessary for communication (chemical and electrical signals) between cells in many types of tissues

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17
Q

Epithelial renewal

A

Epithelial cells are constantly lost and replaced
Stem cells are present, which have high mitotic potential
Location of stem cell varies but usually is near the bB<
Cells are pushed by the new layers away from the BM and shed off

18
Q

Simple squamous epithelium

A

Composed of flat, elongated cells, with a round to oval nucleus, often centrally located
Common locations: lining of body cavities, generally called mesothelium (pleural, pericardial and peritoneal)
Alveolar walls in lungs
Inner lining of blood vessels and lymphatic vessels; called endothelium
Capsule of renal glomeruli

19
Q

Simple cuboidal epithelium

A 
Cuboidal shape, all sides are approximately the same size, cell limits are often well-defined
Examples of cuboidal epithelium: 
-lining ducts of many glands
-choroid plexus in brain
-lining follicles of thyroid gland
-lens of the eye
20
Q

Simple columnar epithelium

A

Tall, narrow, cells with ovoid nucleus located near the base of the cell
Examples of simple columnar epithelium:
-lining the luminal surface of stomach, small and large intestine, gall bladder
-lining the uterus and uterine tube

21
Q

Pseudostratified Epithelium

A

Composed of single layer of irregularly shaped and sized cells
All cells touch the basement membrane, but not all of them reach the apical surface
Ciliated
Examples:
-nasal cavity, upper respiratory tract
-male reproductive: duct of epididymis and vas deferens

22
Q

Stratified squamous epithelium

A

Epithelium composed of several layers of cells
Superficial cells determine the name= the superficial cells have a squamous shape
There are 2 types of squamous epithelium
-non-keratinized
-keratinized

23
Q

Stratified squamous epithelium, Keratinized

A

Cells on the surface lost their nuclei and are composed mainly of keratin, a protective, water-resistant protein
Cornification varies depending on how exposed and mechanically solicited the surface of a region is

24
Q

Transitional epithelium

A

Lines urinary passages

The superficial cells have a specialized plasma membrane providing an osmotic barrier between urine and tissue fluids

25
Q

Glandular Epithelium

A 
Criteria of classifications:
-number of cells in the gland
for multicellular
-shape of duct and shape of secretory units
-type of product
-mode of secretion
26
Q

Unicellular glands

A

Found in epithelial lining and glands of intestine and in the epithelial lining of the respiratory tract
Goblet cells have a “cup”- goblet shape due to presence of abundant mucinogen granules in the apical part of the cell

27
Q

Exocrine glands

A

Secretion released on body surface or internal cavity/tract
Structure: duct and adenomere
(gastric glands, uterine glands, salivary glands)

28
Q

Secretory Units

A

Secretory cells of exocrine glands are grouped in secretory units called adenomeres. This secretory unit manufactures the product, then specialized cells (my-epithelial cells) express it into a duct system

29
Q

Ducts

A

Convey products to needed location (salivary gland to oral cavity)
Ducts may be simple (one opening) or compound (many branches of duct system)

Ducts may be lined with a simple cuboidal, simple columnar, or stratified cuboidal/columnar epithelium

30
Q

Types of adenomeres

A

Tubular: straight or coiled (sweat gland, stomach gland, colon gland)
Acinar: pie-shaped, small lumen (pancreas, salivary glands)
Alveolar: larger luminal space (mammary gland, prostate, sebaceous glands)

31
Q

Compound glands and Parenchyma

A

Compound glands are very large. The collective of secretory units and ducts of a compound gland is termed parenchyma; the connective tissue framework supporting it is called stroma. Large glands are divided into lobes. These are further subdivided by the stroma into lobules. Lobules contain multiple secretory units

32
Q

Serous Gland

A

Watery product, contains enzymes (sweat)
Cells with round nuclei, the cytoplasm is basophilic in the basal portion and acidophilic in the apical part (zymogen granules)

33
Q

Cerumen

A

the secretion of modified sweat glands in the skin go the external auditory canal

34
Q

Mucous gland

A

Slick, viscous secretion (tracheal mucus)

Cells with flat heterochromatic nuclei at the base of each cell
Cytoplasm is vacuolated (frothy) and pale
Mucinogen granules are not detectable with routine stains

35
Q

Mixed glands

A

A gland producing both mucus and serous secretion (saliva)

Mucus and serous star a common duct system, mucous acing units with associated crescent of serous cells, a serous demilune

36
Q

Sebaceous gland

A

oily secretion, sebum
Centrally located nuclei
Cytoplasm is pale and foamy as lipid droplets are washed out during processing

37
Q

Merocrine secretion

A

smooth lumen, no cytoplasm lost producing secretion

Cell remains intact; contents of small secretory granules are released as the secretory product

(exocrine pancreases, salivary glands)

38
Q

Apocrine secretion

A

apex bulges, some cytoplasm is lost producing secretion

Cell bulges, a portion of cell is lost with the product
Predominant sweat gland of domestic mammals

39
Q

Holocrine secretion

A

Entire cell is the product

Disintegrated cells with contents become the secretion
Sebaceous glands

40
Q

Endocrine secretion

A

Secreted product is directed toward the blood vessels

Microanatomy (21 decks)

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