Histology Ch 2: Epithelial Tissue

What are the characteristics of epithelial tissue?

-high cellularity

-avascular

-polarity

What does it mean by high cellularity?

Made up of cells that are closely packed together with minimal intervening intercellular substance

What is avascular?

No blood vessels are present between its cells

Why is epithelial cells exhibit polarity?

The basal, lateral, apical surfaces of an epithelial cell can be determined by the location of its cytoplasmic organelles and surface modifications

What epithelial tissues covering external surfaces of the body and give examples?

Ectoderm

-skin & its appendages, cornea, mouth, anus

What epithelial tissues lining the digestive tract, except for those in the mouth and anus?

Endoderm

-liver, gallbladder, pancreas, respiratory tract, urinary bladder, urethra

Mesoderm are epithelial tissues that line the?

Heart, blood & lymphatic vessels, serous cavities, urinary system (kidneys & their ducts, except urinary bladder), male & female reproductive system

What are the basic parts of epithelial tissues?

Basement membrane, epithelial cells

It is responsible for achoring the epithelial cells to the underlying connective tissue.

Basement membrane

What layer of basement membrane that is a sheet of an amorphous material where the basal surfaces of the deepest layers of cells rest, provides structural support to the overlying epithelium, and also serves as an impermeable barrier that allows only water and small molecules to pass through & limits the contact between epithelial cells & the other cell types?

Basal lamina

In EM, Basal lamina consists of 3 layers:

-Lamina rara externa (lamina lucida)

-Lamina densa

-Lamina rara interna

What layer of basement membrane that is of extracellular material which is sandwich between the basal lamina and the underlying tissue and is a product of connective tissue specifically fibroblasts and is absent in some epithelial tissues?

Reticular lamina

What are specialized cells predominantly found lining the external & luminal surface of most organs, constitute the functional tissues of organs, excluding muscles & organs of the nervous system, capable of performing unique functions due to specialized surface and internal modifications?

Epithelial Cells

In apical surface modifications, what are short and fingerlike processes that protrude from epithelial cell’s apical surface and numerous in small intestine (striated/brush border)

Microvilli

What is the function of microvilli?

Absorption, increase surface area of cell

In apical surface modifications, what characterizes epithelial cells of the ductus(vas) epididymis and hair cells of the inner ear, and function the flow/movement of sperm cells, and in auditory & balance?

Stereocilia

In apical surface modifications, what is present only in spermatozoa, and function is the motility of sperm cells, and its absence indicates infertility?

Flagella

In lateral surface modifications, what prevents molecules from passing between adjacent cells?

Tight junctions (zonula occludens)

In lateral surface modifications, what provides stability to epithelial cells and the tissue as a whole by binding the cells together and is typically positioned near the apex of cuboidal & columnar epithelial cells?

Adherent junctions (zonula adherens)

In lateral surface modifications, what is similar to adherent junctions but are particularly well-developed in stratified squamous epithelium?

Desmosomes

In lateral surface modifications, what junctions allow movements of molecules between adjacent cells?

Gap junctions

In basal surface modifications, what anchors epithelial cells to the underlying tissue?

Hemidesmosome

In basal surface modifications, it is like microvilli but inverted, inward, found in basal cells and its function is absorption?

Basal infoldings of the plasma membrane

What are the functional classification of epithelial tissues?

Surface & Glandular Epithelium

What are the specific functions of epithelial tissues?

-Protection of underlying tissues of the body from abrasion & injury

-Transcellular transport of molecules across epithelial layers

-secretion of mucus precursor, hormones, enzymes, and other molecules

-absorption of material from a lumen

-control of movement of materials between body compartments via selective permeability of intracellular junctions between epithelial cells

-detection of sensations via taste buds, retina of the eye, and specialized hair cells in the ear

What classification of surface epithelial tissues that exhibit irregular polygonal outline that fit into each other like piece of a jigsaw puzzle?

Simple squamous epithelium

What type of of simple squamous epithelium lines the luminal surface of the heart, blood and lymphatic vessels?

Endothelium

What type of simple squamous epithelium that lines the serous cavities?

Mesothelium

What classification of surface epithelial tissues is squarish in outline and nuclei are round and centrally located, present in some segments of ducts or smaller ducts of exocrine glands, collecting tubules of kidney, follicles of the thyroid gland, surface of the ovary?

Simple cuboidal epithelium

What classification of surface epithelial tissues is consists of single layer of tall cells with nucleu usually forming a single row, and it is oval and more basal than apical?

Simple columnar epithelium

What simple columnar that lines the stomach, intestines, and large ducts of some exocrine glands?

Non-ciliated simple columnar epithelium

What simple columnar lines the uterus, oviducts, and pulmonary bronchi?

Ciliated simpel columnar epithelium

In stratified squamous epithelium, what cells are flat or plaque-like?

Superficial layer - old cells

In stratified squamous epithelium, what cells are tall cuboidal or columnar?

Deppest layer - new cells

What classification of surface epithelial tissues has the capability to withstand rubbing, forms the epidermis, lines the digestive tract from oral cavity to esuphagus, vagina, part of the urethra, and the superficial surface of conjunctiva and cornea?

Stratified squamous epithelium

What are the characteristics of Keratinized stratified squamous epithelium?

-cella in the topmost layer have no nucle

-abundant in keratin

-more resistant to friction/abrasions

-found in the skin

What are th characteristics of Non-keratinized stratified squamous epithelium?

-cells in the topmost layer are flat but have nuclei

-less resistant to friction/injury

-found in the mucous membrane

What classification of surface epithelial tissues has 2 or 3 layers of cuboidal cells, lines larger ducts of some glands (major salivary glands)

Stratified cuboidal epithelium

What classification of surface epithelial tissues has at least 2 layers of columnar cells (sometimes the deepest layer is cuboidal), lines some ducts of exocrine glands?

Stratified columnar epithelium

What classification of surface epithelial tissues is a “false stratified epithelium” and a single layer of columnar cells; nuclei are found at various levels, all cells rest on basal lamina, lines the membranous and spongy part of male urethra?

Pseudostratified columnar epithelium

What type of pseudostratified columnar lines the trachea and main bronchi?

Ciliated pseudostratified columnar epithelium (respiratory)

What classification of surface epithelial tissues is designed to withstand stretching?

Transitional epithelium

What state of transitional epithelium is the basal cells are cuboidal, the superficial cells bulge out into the lumen giving the cells a dome-shaped profile?

Contracted (relaxed) state

What state of transitional epithelium is the epithelium transforms into a thin stratified squamous epithelium?

Distented (stretched) state

What gland deliver secretions (hormones) into blood or lymph and is ductless?

Endocrine glands

What glands deliver secretions onto covering or lining epithelium and may or may not have ducts?

Exocrine glands

What type of multicellular glands covers epithelium where most cells are secretory?

Secretory epithelial sheet

What type of multicellular glands that is groups of cells that gather around a small orifice that serves as a dict and form shallow invagination within epithelial surface?

Intraepithelial gland

What type of multicellular glands possess true ducts (ex. Major salivary glands, pancreas, liver)

Exocrine glands with ducts

According to morphology of ducts, differentiate simple and compound gland

Simple gland has a single unbranched duct while

In Compound gland, duct has branches

According to the morphology of secretory units, what are the tubular, alveolar, tubulo-alveolar gland?

Tubular - blind ending tube

Alveolar (acinous/acinar) - globular/basket-like

Tobulo-alveolar - some are tubular, some are globular

According to the nature of secretion, what produce a viscous secretion that contains mucin?

Mucous

According to the nature of secretion, what produce a thin, watery secretion that often contains enzymes?

Serous

According to mode of secretion, what release secretion by exocytosis?

Merocrine glands

According to mode of secretion, what release of secretion entails destruction of secretory cells whose remnants are then discharged together with the secretions?

Holocrine glands

According to mode of secretion, what is the apical part of the secretory cells is released together with the secretory product?

Apocrine glands