Epithelial Tissue Flashcards
What are the functions of the skin?
- Protect body from foreign material and pathogens
- Prevents loss of body fluid
- Thermorégulation through heat retention and dissipation
- Protects body from predators (frog’s poisonous skin)
- Sensory abilities like touch
- Communication through visual and pheromonal signals
- Appendages: hair, nails, sebaceous glands, sweat glands
How would you classify skin?
Stratified squamous keratinized epithelium
What are the three main layers of the skin?
Epidermis, dermis, hypodermis
What are the layers of the epidermis?
Basement membrane
Stratum germinativum
Stratum spinosum
Stratum granulosum
Stratum corneum
Is the basement membrane stained?
No
Describe the cells in the stratum germinativum
Singular layer of columnar cells
What do the cells in the stratum germinativum do?
Either divides and creates copy of itself in the same layer or differentiates
Describe the cells in the stratum spinosum
Polygonal shape, has spines between cells
What is special about the cells in the stratum granulosum?
They have keratohyalin granules
What is the function of keratohyalin granules?
Makes skin waterproof
Describe the cells in the stratum corneum?
Flat cells (dead because they burst and released granules)
What are the different types of simple epithelia?
Simple squamous (flat)
Simple cuboidal (cube)
Simple columnar (column)
What are the types of stratified epithelia?
Stratified squamous (keratinized and non-keratinized)
Transitional
What is transitional epithelium?
Tissue changes when expanding
What type of epithelia looks stratified but is only one layer?
Pseudostratified columnar
What is the basement membrane made of?
Proteoglycans, glycoproteins and collagen
What is under the basement membrane?
Reticular fibers
What is the proteoglycan made of?
50% sugar and 50% protein
What is the function of proteoglycan?
The glycosaminoglycan are negatively charged and hold water
What is a glycoprotein made of?
10% sugar and 90% protein
How many sugars are there in a proteoglycan?
3 (link trisaccharide)
What are the three types of glycoproteins?
Laminin
Nidogen
Fibronectin
What is laminin?
Cross shaped glycoprotein
Links surface of epithelial cells to the basement membrane
What is nidogen-1?
A small glycoprotein
Essential components for basement membranes
What is fibronectin
Adhesive glycoprotein
Binds plasma membrane of the epithelial cells to heparan sulfate
What types of collagens can be found in the basement membrane?
Type IV: synthesized by epithelial cells
Type VII: anchoring filaments
Type III: Reticular fibers
What is another name for basement membrane
Basal lamina
What are the functions of the basement membrane?
- Structural attachment of epithelial cells to connective tissue.
- Compartmentalization
- Filtration: movement of molecules is regulated by ionic charges
- Helps maintain polarity of epithelial tissues
- Tissue scaffolding: helps to scaffold regeneration
What are the characteristics of all epithelial tissues?
- Cells are closely associated with little extracellular space
- Cells are strongly attached via intracellulaire junctions.
- Line body surfaces and body cavities
- Specialization: absorption, secretion, sensation, contractility
- Cells are polarized
- Epithelial tissues rest on a basement membrane
What can be found in the stratum germinativum (or basale)?
Stem cells
What can be found in the stratum spinosum?
Desmosomes
Where can melanocytes be found?
Between basement membrane and stratum germinativum
What do melanocytes do?
Sends melanin granules through finger-like projections and gets phagocytosed by stratum spinosum. Melanin protects the nucleus of the cells
What are the two types of melanin?
Eumelanin (brown)
Pheomelanin (red)
What are the two layers of the dermis?
Papillary layer
Reticular layer
