Lecture 5: Epithelium Cont Flashcards
Two ways of classifying lining epithelia
- Number of layers
2. Shape of surface cells
Three types of “number of layer” classification
Simple - 1 layer
Stratified - 2 or more
Special case: transitional epithelium
Four types of “shape of surface cell” classification
Squamous
Cuboidal
Columnar
Stratified cuboidal/columnar (uncommon)
Squamous nucleus
flat, on top
Cuboidal nucleus
Middle
Columnar nucleus
Close to basal membrane
Simple squamous epithelium is composed of
flat, elongated cells, with round to oval nuclei, often centrally located
Simple squamous epithelium common locations (4)
- Lining of moist internal surfaces such as pleural, pericardial and peritoneal cavities. This general structure is known as mesothelium
- Alveolar walls
- The luminal surface of blood vessels and lymphatic vessels, cells known as endothelial cells
- Capsule of renal glomeruli
Simple cuboidal epithelium
Cuboidal shape, all sides are approximately the same sixe, cell limits are often well defined
4 examples of simple cuboidal epithelium
- Lining ducts if many glands
- Choroid plexus in brain
- Lining follicles of thyroid glands
- Lens of the eye
Simple columnar epithelium
Tall, narrow cells with ovoid nucleus located near the base of the cell
Examples of simple columnar epithelium (2)
- Lining the luminal surface of stomach, small and large intestine, gall bladder
- Lining the surface of the uterus and the uterine tube
Psuedostratified epithelium
- Composed of a single layer of irregularly shaped and sized cells
- All cells contact the underlying basement membrane, but not all of them reach the surface
Examples of psuedostratified epithelium (3)
- Nasal cavity
- Upper respiratory tract
- Male reproductive: duct of the epididymis and ductus deferns
Psuedostratified columnar epithelium
All cells touch basement membrane but all cells are not of the same height and some cells don’t reach the surface
Kartagener’s Syndrome
- Congenital inherited malformation
- Dyein arms are missing in axonema of cilia and sperm tails
Two problems that come with Kartagener’s Syndrome
- Chronical respiratory infection - due to absence of cleansing activity of cilia in upper airways
- Male sterility - resulting from non-motile sperm cells
Stratified squamous epithelium
- Composed of several layers of cells
- Superficial cells determine the name = superficial cells have squamous shape
Two types of squamous epithelium
Keratinized
Non-keratinized
Examples of nonkeratinized stratified squamous epithelium (4)
- Cornea
- Esophagus
- Oral cavity
- Vagina
Examples of keratinized stratified squamous epithelium (4)
- Epidermis
- Proventricles
- Oral cavity
- Vagina in estrus
Examples of stratified cuboidal/columnar epithelium (2)
- Ducts of some glands
- Conjuctiva
Example of transitional epithelium
Lining of urinary tract
Stratified keratinized squamous epithelium
Cells on the surface lost their nuclei and are composed mainly of keratin
Keratin
A water-resistant protein, provides protection
Do stratified squamous keratinized epithelium have nuclei?
No
Transitional epithelium
- Superficial cuboidal cells bulge into lumen
- Superficial cells become flattened or squamous when organ is distended
- Superficial cells have a specialized plasma membrane providing an osmotic barrier between urine and tissue fluids
Glandular epithelium produce
saliva, mucus, sweat, enzymes, acid, sebum, tear film, milk, hormones, cerumen, oil
5 ways to classify glandular epithelium
- According to the number of cells in the gland = unicellular vs multicellular
- Shape of duct
- Shape of adenomera
- Type of product
- Mode of secretion
Unicellular gland
Found in epithelial lining, glands of intestine, and in the respiratory tract
Example of unicellular gland
Goblet cells (only one) Have a cup shape due to the presence of abundant mucinogen granules
In a goblet cell, where are the mucinogen droplets seen?
In the apical part of the cell
Do exocrine cells have ducts?
Yes
Do endocrine cells have ducts?
No
Adenomere
- Cells of the exocrine secretory end-piece
- Secretory unit that manufactures the product
What cells express product of adenomeres into the duct system?
Myoepithelial cells
Purpose of ducts
Convey products to needed location
Two types of ducts
Simple - one opening draining the gland
Compound - duct branches many times
What kind of epithelial cells can ducts be lined with?
- Simple cuboidal
- Simple columnar
- Stratified cuboidal/columnar epithelium
Large glands are typically subdivided into
lobules
Three ways to classify based on the shape of adenomeres
- Tubular
- Acinar
- Alveolar
Tubular adenomere
straight or coiled
Examples: sweat gland, stomach glands, colon glands
Acinar adenomere
pie-shaped, small lumen
Examples:
pancreas, salivary glands
Alveolar
large lumen
Examples: mammary gland, prostate, sebaceous glands
Simple tubular glands placement
Diaphram and small intestine
Tubular adenomere placement
Intestinal glands in large intestine
Simple coiled tubular glands example
diagram and sweat gland
Acinar shape corresponds to what unit
rounded secretory unit
4 ways to classify according to product
- Serous
- Mucous
- Mixed
- Sebaceous
Serous
Watery product, contains enzymes
Ex. sweat
Mucous
slick, viscous secretion
Mixed
A gland producing both mucus and serous secretion
Sebaceous
oily secretion, often known as sebum
Serous gland
cells with rounded nuclei, the cytoplasm is basophilic in the basal portion and acidophilic in the apical part (zymogen granules)
Mucus gland
- 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
Mixed gland
Mucous and serous cells sharing a common duct system, mucous acinar units with associated cresent of serous cells, a “serous demilune”
Sebaceous gland
- Centrally located nuclei
- Cytoplasm is pale and “foamy” as liquid droplets are washed out during processing
Four modes of secretion
- Merocrine
- Apocrine
- Holocrine
- Endocrine
Merocrine
Smooth lumen, no cytoplasm lost producing secretion
Apocrine
apex bulges, some cytoplasm is lost producing secretion
Holocrine
entire cell is the product
Endocrine
secreted product is directed
Myoepithelial cells
contractile, associated with salivary, mammary, and sweat glands
4 types of “Other” epithelium
Sensory
pigmented
germinal
seminiferous
Epithelial cells repair
- They’re constantly lost and replaced
- Stem cells are present which have high mitotic potential
- Location of stem cell varies depending on type of epithelium and function
