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47 Cards in this Set

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Define epithelium and 2 main types
group of functionally related cells. 1) boundary epithelial- cover lining of body surfaces and cavities 2) glandular- serve as functional group in secretory glands
functions of epithelial cells
protection, absorption, transport, secretion from glands, excretion, facilitate diffusion, lubrication
describe intercellular contacts
epithelial cells are cohesively attached to each other by adhesion molecules and junctions
how are nutrients delivered to epithelium?
by diffusion from blood vessels in adjacent connective tissue since they lack their own blood supply
what is the basal lamina (basement membrane)?
A sheet of extracellular matrix to which the epithelial cells are anchored.
Which surface is apical? Which is basal?
Surface facing the lumen is apical,other side is basal.
Which epithelial cells can divide?
Typically only those attached to basement membrane?
Name 4 types of cell layering.
simple
stratified
pseudostratified
transitional
What is the difference between stratified and pseudostratified layers?
In stratified layers each level is separate and distinct, however in pseudostratified, the cells are all attached to the basement membrane.
Describe transitional layering.
a form of stratified epithelium which is highly specialized to accomodate stretching. Found in urinary tract. Has features of both squamous and cuboidal epithelials.
Name 3 shapes of Epithelial
cuboidal- cube shaped
squamous-flattened
columnar- taller than it is wide
What are 3 specializations of the apical epithelial surface?
Microvilli
Cilia
Stereocilia
Describe Microvilli
small projections at the apical surface specialized for absorption. Looks like a short fat comb.
Describe Cilia
contains microtubules, has coordinated movements, and is specialized to transport materials.
Desce Stereocilia
Non motile, long microvilli, specialized for absorption. Looks like a hair pick.
Define Zona Occludens
continuous band that seals the apical surface of one epithelial membrane to another. From side view looks like gum stuck between cells, from top looks like 1920s floor tiles.
Define Zona Adherens
continuous bands for the mechanical attachment of cytoskeletal elements (actin)
Define Macula Adherens (desmosomes)
Spots of cell adhesions, attachment site of cytoplasmic intermediate filaments (keratins)
Define Gap Junction
a communication junction between cells with tiny pores that allow passage of small signaling molecules among cells
Define integrins
transmembrane proteins that bind tri-peptide RGD sequence of ECM proteins that is used by epithelial cells to bind components of the basement membrane
Define E-cadherin
Transmembrane protein that binds E-cadherin molecules expressed by adjacent cells.
How are glands derived from epithelial cells?
exocrine- outgrowth of epithelials that keeps its connection to other epithelials-products released to surface. endocrine-loses connection so product released to blood.
Describe 2 duct patterns
Simple- unbranched
compound- branched
Exocrine glands have 2 main parts. Name them
secretory and duct portions
Name and describe 3 types of secretory compartments
tubbular- looks like tube
acinar- looks like cluster of grapes
tubuloacinar- has tubular and acinar components
What's a goblet cell and where are they found?
modified columnar epithelial cells that make and secrete mucous scattered througout respiratory and intestinal lining
Name the types of exocrine glands and what they produce.
Serous- protein product
Mucous- carbohydrate product
Describe Merocrine Secretion
Secretion is exocytosed into lumen
Describe Apocrine Secretion
Pinching off of apical cytoplasm with product
Holocrine Secretion
Shedding of whole cell.
What is mesothelium
Epithelials derived from mesoderm. These simple squamous cells cover external surfaces of digestive organs, lungs and heart
What are parenchyma?
functionally specialized cells
How are epithelials renewed?
Subject to wear and tear. Only those in contact with basement membrane can be regenerated. Replacement occurs by division of remaining cells. Rapid in intestine, slow in glands
What are the roles of pseudostratified and stratified epithelial cells?
pseudo- secretion,transport, sensory reception
stratified- protection
simple- secrete, absorb, filter
What are regression, metaplasia and neoplasia
-thinning or loss
-transformation of one tissue type into another
-formation of new cell type
What is stroma?
Supportive framework in cells
What is absorption
cells taking up materials such as gases, nutrients and sugars
what is basal lamina composed of?
type IV collagen, proteoglycans and other extracellular proteins
DEscribe myoepithelial cells
Branched epithelial cells with myosin and lots of actin filaments. Specialized for contraction.
what are hemidesmosomes?
These are present in a contact zone and bind a epithelial cell to the basal lamina. Hemisdesmosomes are made of integrin proteins.
What is a cornified layer?
The top dead layer with no visible cell nuclei.
What are tonofilaments?
Keratin bundles that insert into desmosomes.
What is the basal layer?
The surface of a cell lying on the basement membrane.
What are flagella?
Similar to cilia, found in sperma and limited to one flagellum per cell
What is the brush border?
An orderly array of microvilli in lining of absorptive tissues.
What is keratinized?
Epithelial cells in which the surface cells are dead with no discernable nuclei
What is an axoneme?
The core of cilia and flagella comprised of 9 pairs of microtubules that surround 2 central microtubules.