Epithelial tissue Flashcards
Name the seven functions of skin
1) Protection – Skin acts as a barrier to block foreign material from entering the body and resists abrasion
and penetration
Containment – Loss of body fluid is prevented by skin
Thermoregulation – Skin facilitates both heat retention and heat dissipation by controlling the transfer of
heat across the body’s surface
Immunological Defense – Skin harbors may immune cells that defend against pathogens
Sensory Abilities – Skin allows for the sensation of many stimuli, such as pressure
Communication – Visual (i.e., blushing) and pheromonal signals are released by skin
Appendages – The skin is host to many appendages such as hair, nails, sebaceous glands, and sweat
glands
Classify skin and the four layes of cells in the basement membrane from most basal to most apical
Skin is classified as stratified squamous keratinized epithelium
The four layers of cells are the stratum germinativum,
stratum spinosum, stratum granulosum, and stratum corneum
How to stain the Basement Membrane ?
By using the P.A.S reaction (Periodic acid - schiff stain)
F[SO4H]2 reacts with Aldehyde to produce magenta reaction - revealing the Basement
Membrane
Composition of Basement Membrane
○ Proteoglycans
○ Glycoproteins
○ Collagen
○ Layer of Reticular fibers that underlies Basement membrane
■ This is what keeps the Basement Membrane in place
Is the Basement Membrane a Connective Tissue?
○ No - to be a connective tissue the tissue must originate from a specific part of the embryo
○ What is it then?
■ It is its own type of structure and not classified as any specific type of tissue
what is the composition Proteoglycan
○ 50% sugar; 50% protein
○ Core protein attached to a link trisaccharide attached to a glycosaminoglycan
■ The glycosaminoglycan (GAG)
● Function: GAGs are polar and holds water
● Different GAG = Different proteoglycan; GAGs give
proteoglycans specificity
what is the composition of glycoproteins ?
10% sugar; 90% protein
Examples of Glycoproteins
Laminin
■ Structure: cross shaped
■ Function: Connects epithelial cells to the basement membrane
○ Nidogen-1
■ Structure: Small Glycoprotein
■ Function: important part of the basement membrane
○ Fibronectin
■ Function: adhesion, connects the plasma membrane of epithelial cells to heparan
sulfate
Collagens of the Basement Membrane
○ Type IV - made by epithelial cells
○ Type VII - anchoring filaments, anchors Basement Membrane to the lamina propria
(Connective Tissue)
○ Type III collagen - reticular fibers
○ Note: Collagens that are made are dependent on the cells that make them
■ In other words if the cell that makes that specific type of collagen is not present that
type of collagen will not be present
Why is there no extracellular space in the Epithelium?
Presence of Desmosomes, Hemidesmosomes, and GAP junctions
Functions of the Basement Membrane
○ Attachment of Epithelial cells to the CT (Dermis)
○ Compartmentalization - isolating epithelial cells and muscle cells
○ Filtration - based on ionic charges; really important in the kidney
○ Helps maintain polarity in epithelial tissues - indicator of where apical and basal are
○ Tissue scaffolding - provides the scaffolding for tissue during regeneration
■ Example: if there is injury to epithelial tissue
Characteristics of Epithelial Tissue
Cells are closely associated with little extracellular space - because of the intracellular junctions
Cells are strongly attached via extracellular junctions
Line body surfaces and cavities
o Note: Epithelial tissue is only keratinized if it lines body surfaces outside of the body -
epithelial tissue on the inside of the body is non-keratinized
Specialization - absorption, secretion, sensation, contractility
o We will learn where these specializations occur
Cells are polarized - Indicates apical/basal so that the cells can know which way to grow
Epithelial tissues rest on a basement membrane - Always!!!
