Histology of Epithelial Tissue Flashcards
Epithelial tissue is composed of aggregates of _ that are tightly connected by different types of intercellular junctions; these aggregates rest on a supportive structure called the _
Epithelial tissue is composed of aggregates of epithelial cells that are tightly connected by different types of intercellular junctions; these aggregates rest on a supportive structure called the basement membrane
_ is epithelial tissue that lines the blood vessels
Endothelium is epithelial tissue that lines the blood vessels
Aggregates of epithelial cells rest on a supportive structure called the _ ; this separates them from an underlying layer of loose connective tissue that contains blood vessels
Aggregates of epithelial cells rest on a supportive structure called the basement membrane ; this separates them from an underlying layer of loose connective tissue that contains blood vessels
Where do epithelia get their oxygen, nutrients, and signaling molecules from?
Epithelia are avascular, so the blood vessels in the underlying connective tissue are their source of oxygen, nutrients, signaling molecules, and other proteins
* Must pass through connective tissue and across the basement membrane
Epithelial tissue can either be organized into layers that line or cover surfaces (like skin) or into _ that specialize in secreting different products into the body or external environment
Epithelial tissue can either be organized into layers that line or cover surfaces (like skin) or into glands that specialize in secreting different products into the body or external environment
The underlying connective layer in most of our internal organ system is called _
The underlying connective layer in most of our internal organ system is called lamina propria
The underlying connective layer in the skin is called the _
The underlying connective layer in the skin is called the dermis
The (apical/ basolateral) side of the polar epithelial cell faces away from the basement membrane
The apical membrane side of the polar epithelial cell faces away from the basement membrane
The _ is the bottom-most layer or floor of the epithelial tissue
The basement membrane is the bottom-most layer or floor of the epithelial tissue
The basement membrane is composed of the _ and the _
The basement membrane is composed of the basal lamina and the reticular lamina
The basal lamina has two zones: _ and _
The basal lamina has two zones: lamina lucida and lamina densa
The lamina _ has specialized glycoproteins called laminins
The lamina lucida has specialized glycoproteins called laminins
* This layer is right next to the epithelial cells’ plasma membrane
* Laminins bind to hemidesmosomes and also help guide development, maintain structural architecture, aid in wound development and invasion of cancer cells
The lamina _ contains type IV collagen
The lamina densa sits beneath the lamina lucida and contains type IV collagen (plus various glycoproteins and proteoglycans)
The layers of the basement membrane are _ , _ , _ (superficial to deep)
The layers of the basement membrane are:
Lamina lucida (superficial)
Lamina densa (middle)
Reticular lamina (deep)
The reticular lamina is beneath the basal lamina and is derived from connective tissue
_ epithelial cells are a single layer of columnar cells that all rest on the basal lamina but falsely appear to be stratified
Pseuodostratified epithelial cells are a single layer of columnar cells that all rest on the basal lamina but falsely appear to be stratified
There is a special type of stratified epithelium called _ that is seen in tissues that need to stretch, like the bladder, or parts of the urinary tract
There is a special type of stratified epithelium called transitional epithelium that is seen in tissues that need to stretch, like the bladder, or parts of the urinary tract
* Cells in the lowest layer are cuboidal or columnar
* Cells in the upper layer vary in appearance (cuboidal without stretch, squamous when stretched)
Simple columnar epithelium in the rectum (still part of absorptive intestine) are important in transporting water
Anus is part of the outside world so it has tough stratified squamous epithelia
_ are tightly spaced finger-like extensions of cells that are commonly found in the renal tubules and GI tract because they increase the cell’s surface area and aid in absorption and secretion
Microvilli are tightly spaced finger-like extensions of cells that are commonly found in the renal tubules and GI tract because they increase the cell’s surface area and aid in absorption and secretion
* Epithelial cells with microvilli are sometimes said to have a brush boarder
The microvilli contain a core of actin filaments that are cross-linked by a protein called _
The microvilli contain a core of actin filaments that are cross-linked by a protein called villin
_ are thin, highly motile extensions of the apical membranes on some columnar and pseudostratified epithelial cells ; they are commonly found in the respiratory tract and fallopian tube
Cilia are thin, highly motile extensions of the apical membranes on some columnar and pseudostratified epithelial cells ; they are commonly found in the respiratory tract and fallopian tube
Each cilium has a specific structure of nine pairs of peripheral microtubules that surround two central microtubules, called _
Each cilium has a specific structure of nine pairs of peripheral microtubules that surround two central microtubules, called an axoneme
_ proteins are the molecular motors of cilia
Dynein proteins are the molecular motors of cilia
What is the purpose of cilia in the respiratory tract? In the fallopian tube?
Respiratory tract cilia help to remove inhaled particles from the environment
Fallopian tube cilia help guide the egg from ovary to uterus and help sperm get to the epididymis for maturation
Immotile cilia syndrome (Kartagener syndrome)
Immobile cilia syndrome is an autosomal recessive disorder that causes a defect in cilia
* The cilia’s axonemes lack dynein
* Associated with sterility, infertility, lower respiratory tract infections
Stereocilia are not actual cilia; instead they are _ and are found in only a few places such as _ and _
Stereocilia are not actual cilia; instead they are unique, long microvilli specialized for absorption and are found in only a few places such as male reproductive tract and sensory components of the inner ear
Epithelial cells can also form glands which are _
Epithelial cells can also form glands which are collections of cells that release substances into the body or the external environment
* Can either be endocrine or exocrine
Endocrine glands secrete their products to _
Endocrine glands secrete their products into space around the cells from which nearby blood vessels take up the hormones to circulate throughout the bloodstream
* Endocrine = into blood stream = to target tissues
Exocrine glands secrete their product onto _
Exocrine glands secrete their product onto epithelial surfaces such as onto the skin or into the GI tract
(True/False) Exocrine glands are secreting hormones
False; exocrine glands are not secreting hormones
* We cannot call their products hormones because they are not circulating in the bloodstream
Name some exocrine gland examples
- Mammary glands
- Sweat glands
- Secretory glands of the stomach and pancreas for digestion
How do we classify exocrine glands?
Exocrine glands can be:
* Unicellular or multicellular
* Serous, Mucous, or Mixed seromucous
* Eccrine, Apocrine, Holocrine
Unicellular exocrine glands are commonly called _ cells; they secrete their product via _
Unicellular exocrine glands are commonly called goblet cells; they secrete their product via exocytosis
* They are found interspersed within the columnar cells lining the intestinal and respiratory tracts
How do multicellular exocrine glands make and release their product?
Multicellular exocrine glands make their product in a multicellular secretory unit and then transport the secretion through a duct –> release it to the epithelial surface
* Ex: sweat glands, mammary glands
Serous glands release a _ kind of substance
Serous glands release a watery, proteinaceous kind of substance
* Often contains enzymes
* Ex: chief cells of the stomach that secrete digestive enzymes in the stomach
Mucous glands secrete a _ kind of substance
Mucous glands secrete a viscous, slippery kind of substance (aka mucus)
* It is good at lubricating
* Ex: esophageal glands
Mixed seromucous glands secrete both _ and _
Mixed seromucous glands secrete both proteins and mucus
* This includes most salivary glands because saliva contains enzymes + mucus
Eccrine glands secrete via _
Eccrine glands secrete via exocytosis only
* Product is packaged into vesicles –> transported to the cell surface –> fuse to cell membrane –> release into duct
Examples of eccrine glands
Examples of eccrine glands: salivary glands and eccrine sweat glands
Aprocrine glands secrete via _
Apocrine glands secrete “A Piece”; they secrete their product along with a piece of the apical cell cytoplasm
Examples of apocrine glands
Mammary glands, apocrine sweat glands of the armpit
Holocrine glands secrete via _
Holocrine glands secrete the Hole thing; they first accumulate their secretions and then the cell dies and becomes part of the secretion
Examples of holocrine glands
Sebaceous glands in the skin are examples of holocrine glands
Sweat glands in the armpit are known as _ sweat glands; sweat glands on the skin are _ sweat glands
Armpit: apocrine
Skin: eccrine
Apocrine glands function to _
Apocrine sweat glands function to release pheromones (sexual attraction)
Eccrine sweat glands function to _
Eccrine sweat glands function to cool the body
Sebaceous glands are found on the _ and they secrete _
Sebaceous glands are found on the skin and they secrete sebum which functions to lubricate and waterproof the skin
Binding of epithelial cells is done by _ ; allows for formation of sheets and glands
Binding of epithelial cells is done by desmosomes ; allows for formation of sheets and glands
* There are two types: belt and spot desmosomes
The scientific name for belt desmosomes is _
The scientific name for belt desmosomes is zonulae adherens or adherens junctions
The scientific name for spot desmosomes is _
The scientific name for spot desmosomes is maculae adherens
_ wrap around cells like a belt and connect epithelial cells together; example: they anchor to actin filaments inside the cells
Belt desmosomes wrap around cells like a belt and connect epithelial cells together; example: they anchor to actin filaments inside the cells
Belt desmosomes are helpful in resisting _ forces; like would happen when food moves down the GIT
Belt desmosomes are helpful in resisting shearing forces; like would happen when food moves down the GIT
The bridges formed by belt desmosomes are formed by _ proteins
The bridges formed by belt desmosomes are formed by cadherin proteins
_ are small, disk-shaped, adhesive plaques that are anchored to intermediate filaments in epithelial cells
Spot desmosomes are small, disk-shaped, adhesive plaques that are anchored to intermediate filaments in epithelial cells
Spot desmosomes are commonly found in regions like _
Spot desmosomes are commonly found in regions like the bladder where tissue needs strength
* They are strong intercellular binders
* These bridges are also formed by cadherin proteins like desmoglein and desmocollin
_ is a rare blistering skin disease in which antibodies form agains the protein desmoglein and disrupts spot desmosomes
Pemphigus vulgaris is a rare blistering skin disease in which antibodies form agains the protein desmoglein and disrupts spot desmosomes
Hemidesmosomes provide the attachment between _ and _
Hemidesmosomes provide the attachment between epithelial cells and basement membrane
Hemidesmosomes contain proteins called _ that extend from the base of the hemidesmosome into the lamina lucida
Hemidesmosomes contain proteins called integrins that extend from the base of the hemidesmosome into the lamina lucida where they connect with laminin
_ is a rare autoimmune disease that is caused by autoantibodies binding to a component of the hemidesmosomes
Bullous pemphigoid is a rare autoimmune disease that is caused by autoantibodies binding to a component of the hemidesmosomes –> leads to poor attachment of epithelial cells to the basement membrane –> blistering
Gap junctions are essential to cell communication; they have a unique hexagonal array of proteins called _ that form a cylindrical _
Gap junctions are essential to cell communication; they have a unique hexagonal array of proteins called connexins that form a cylindrical connexon
What would happen if we did not have tight junctions?
Without tight junctions we might see molecules leaking passively and randomly between the epithelial cells; tight junctions are meant to seal in the neighbor cells’ plasma membrane to one another and prevent large molecules from passing through the intercellular space
Tight junctions have special transmembrane proteins called _ and _
Tight junctions have special transmembrane proteins called claudins and occludins which are anchored to the cell’s actin cytoskeleton by zona occluden proteins
