Lecture 4 Flashcards
Epithelia can be defined by what two surfaces?
- An unattached free surface
2. Basal surface
What can the unattached free surface be exposed to?
The environment or internal body cavity
What is the basal surface of epithelia attached to?
The basement membrane
Epithelia has one or more layers of closely adhering cells that form a _____ sheet.
flat
By what two ways do epithelial cells get nutrients?
- Nutrients are diffused from capillaries in the underlying CT.
- A “moist” free surface
Why can a paper cut into the epithelia of a finger hurt but not bleed?
Epithelia is innervated but avascular (no blood supply)
What type of neurons innervate epithelia?
sensory
The basement membrane is a layer of _____ and ______ proteins that anchors epithelium to underlying _______ tissue.
Collagen; adhesive; connective
What kind of permeability does the basement membrane possess?
Semi-permiability
The basement membrane is composed of ______ lamina and ______ lamina.
Basal; reticular
What two sources supply the basal lamina with its complex mixture of proteins?
(Overlying) epithelial cells and (underlying) fibroblasts
What is the main cell of all connective tissues?
Fibroblast
Fibroblasts are skinny, non-descript cells that can be described metaphorically as the ______ of tissues, since they grow everywhere.
weeds
Fibronectin and proteoglycans are structural molecules produced by what connective tissues cell?
Fibroblast
What proteins do the basal epithelial cells contribute to the basal lamina?
Laminin, entactin, and type IV collagen
How does type IV collagen differ from most collagens?
Most collagens are fibrous, but type IV collagen is gelatinous.
The gelatinous nature of type IV collagen allows it to act as a ______ in the basal lamina.
selective barrier or filter
T/F. The reticular lamina is part of the basement membrane of all epithelial tissues
False. Only some epithelia have the reticular lamina.
What two fibers is the reticular lamina composed of?
Composed of long straight collagen fibers and branched reticular fibers
What is above and what is below the reticular lamina?
The basal lamina is above and the lamina propria is below.
What is the name of the light staining thin layer of the basal lamina? The dark staining layer?
Lamina lucida.
Lamina densa
The lamina lucida contains the extracellular portions of what transmembrane cell adhesion proteins?
Laminin, entactin, fibronectin
T/F. Laminin is a glycoprotein secreted by epithelial cells.
True
What transmembrane glycoprotein bridges the lamina lucida and lamina densa to the plasma membrane?
Laminin
What type of collagen is the lamina densa composed of?
Type IV collagen
The lamina densa is the structural attachment site for anchoring fibrils that extend to what fibers in the CT under the epithelium?
Reticular fibers
The basal lamina and the reticular lamina are joined together by type ____ and type ______ collagen fibrils that weave through loops of type _____ collagen anchoring fibrils.
I; III; VII
What is the difference between a fibril and a fiber?
A fibril is a fine fiber
What number collagen fibril is the strongest?
Type I collagen
Which number collagen fiber attaches both of its ends to the basal lamina and loops down into the reticular lamina around larger collagen fibers?
Type VII collagen
Hemidesmosomes connect the basal lamina to what cytoskeletal structures?
Tonofilaments
What are two functions of simple squamous epithelium?
It allows rapid diffusion of gases.
Can secrete serous fluid
Membranes covering body cavities and organs are made of what type of epithelium?
Simple squamous epithelium
What are three functions of simple cuboidal epithelium?
absorption, secretion and conduction
Mammary glands and salivary glands are what kind of epithelium?
Simple cuboidal epithelium
T/F. Stratified cuboidal epithelium is rare.
True
The intestines and uterus are lined with what kind of epithelium?
Simple columnar epithelium
The simple columnar epithelium of the uterus lining contains what mucous producing single-celled bodies?
Goblet cells
Which epithelium type has a mix of short basal cells and taller goblet cells?
Pseudostratified epithelium
What is the function of pseudostratified epithelium?
To secrete and propel respiratory mucus
What are three major components of mucous membranes?
- Mucous-producing epithelium
- Lamina propria
- Muscularis mucosae
What is the lamina propria?
An underlying layer of vascular connective tissue
What is the muscularis mucosae found underlying the lamina propria?
A thin layer of smooth muscle
What kind of passageways are lined with mucous membranes?
Passageways that open to the exterior: digestive tract, respiratory tract, urinary tract, and reproductive tracts
What is the benefit of mucous in the digestive tract?
It can lubricate passing food
What does mucus do in the respiratory, urinary, and reproductive tracts?
Traps foreign particles or pathogens
What cells produce mucus in the epithelium?
Goblet cells
What produces mucus in the lamina propria?
Multicellular glands
Why is the upper respiratory tract and the fallopian tube ciliated?
To sweep mucus out of the body
What is stratified epithelia named for?
The shape of the surface cells
The source of replacement cells for epithelium comes from the deepest that sit on what membrane?
Basement
Keratinized epithelium has a surface layer of _____ cells that contain abundant ______ protein.
Dead; keratin
Dead cells of epithelia usually lack a _______ and are coated with ______ that reduce water loss.
nucleus; lipids
Para- and Ortho-keratinized Epithelia have ________ characteristics of keratinization.
intermediate
What kind of epithelium forms an abrasion-resistant, moist, slippery layer?
Nonkeratinized stratified squamous epithelium
Where is nonkeratinized stratified squamous epithelium found?
Oral mucosa, esophagus, vagina
In keratinized stratified squamous epithelium, the keratinized layer retards _____ loss and is a barrier to ______ and ______.
water; irritants; pathogens
What kind of stratification does transitional epithelium have?
It is pseudostratified
A key characteristic of transitional epithelium is that its surface cells are covered with what?
protein plaques
What is the purpose of the protein plaques on top of transitional epithelia?
To protect the tissues from over-stretching.
What shape do the plaques of transitional epithelium take when the bladder is filled with urine?
The plaques become dome shaped. Otherwise they’re flat
T/F. All cells, except blood cells, are anchored to other cells or to the matrix surrounding them by intercellular junctions.
True
Which junction seals together neighboring cells in an epithelial sheet to prevent leakage between cells?
The tight junction
What do adhesive junctions bind to on the inside of a cell?
Actin bundles in one cell to actin bundles in an adjacent cell
Desmosomes bind to _______ filaments in one cell to those in an adjoining cell.
intermediate filaments
Which cell junction allows passage of small, water-soluble molecules from one cell into another?
Gap junctions
Desmosomes and hemidesmosomes both bind to what cytoskeletal structures?
Intermediate filaments
Unlike desmosomes, hemidesmosomes only bind one end to intermediate filaments and the other to the _______ ________.
Basal lamina
A desmosome is also called a macula adherens. What does the term “macula” describe about this kind of cell junctions?
Macula describes junctions that are in specific spots, like spot welds, rivets, or patches.
The tight junction is also known as zonula occludens and the adhesive junction the zonula adherens. What does the term “zonula” describe about these kinds of cell junctions?
Zonula describes junctions that completely encircle a cell, like sweat bands around a person’s head.
T/F The apical end of cell junctions is found close to the free surface of cells.
True
Tight junctions completely encircle a cell at which side of the cell? (apical or basolateral)
apical
Which cell junctions create a quilted pattern?
Tight junctions
Tight junctions are composed of which transmembrane adhesive proteins?
Claudin, occludin, and other cell junctional adhesion molecules (JAM)
T/F Adhesive proteins such as claudin, occludin, and JAMs will bind to the same protein in an adjacent cell.
True
Which cell junction is principally composed of the calcium ion dependent cadherin transmembrane proteins
Adhesive junction
What would happen to an adhesive junction if it is treated with EDTA?
It would lose its cell to cell connection since EDTA would chelate the Ca++ needed for the a junction to stay interconnected
Which cell junction hold cells together against mechanical stresses like shearing forces and weight lifting?
Demosomes
Attachment plaques of desmosomes are linked to intermediate filaments of the cytoskeleton, like keratin, and to integral membrane proteins like ________
Cadherin
How do desmosomes help to distribute shearing forces from one cell to another?
By linking the cytoskelelton of one cell to another
T/F Hemidesmosomes link intermediate filaments of a cell to collagen fibers in the basement membrane and not any deeper.
False. Laminin further links the basal lamina to underlying connective tissue.
Where are some of the places that gap junctions are abundant in?
Embryos, cardiac muscle and smooth muscle
What do gap junctions conduct from one cell to another?
small solutes and electrical signals
A connexon is made of how many connexin transmembrane protein monomers?
Six
T/F Gap junctions are made of a single connexon channel.
False. They are made of clusters of connexons
What tissue are glands predominantly composed of?
epithelial
Which type of gland secretes its products through a duct? Which type directly into blood or intercellular tissue?
Exocrine is via a duc
Endocrine directly into blood
Which three organs are both exocrine and endocrine?
Pancreas, liver, and gonads
What are the two types of exocrine glands called?
Simple and compound
What do compound exocrine glands have that simple exocrine glands do not?
Branched ducts
What are the three shapes of ducts?
Tubular
Acinar
Tubuloacinar
What is an acinus?
A dilated sac of secretory cells
What are secretory cells found in a duct called?
tubular
Tubuloacinar glands have secretory cells in both _____ and _______ regions
ductal and acinar
What kind of secretions do serous glands produce?
Thin, watery secretions
What are some examples of serous secretions?
sweat, milk, tear, and digestive juices
What do mucous glands produce?
The produce mucus
What is mucus made of?
Mucin, a glycoprotein that aborbs water to form a sticky secretion
Whole cells are released by what type of glands?
Cytogenic glands (testis release sperm, ovaries release ova)
What are the two basic mechanisms of glandular secretions?
Merocrine and holocrine
Which secretion mechanism is most common?
Merocrine
In merocrine secretion how do secretory granules get past the secreting cell’s membrane?
Via exocytosis - fuse with the inside of the secretory cell’s membrane and then open on the outside of the cell
Is there any loss of cytoplasm with merocrine secretion?
No
Which secretion type sacrifices the whole cell in order to secrete it’s contents?
Holocrine
Are sebacious glands holocrine or merocrine?
holocrine
Is sweat released by holocrine or merocrine secretion mechanisms?
Merocrine
