L1/L2 Epithelium & Glands Flashcards
What are the four basic tissue types?
Epithelium, connective, muscle and nervous
Origin of ectoderm epithelia
skin; sweat glands; oral cavity; vagina; anus
Origin of mesoderm epithelia
endothelium; mesothelium (lining of body cavities); genital and urinary systems
Origin of endoderm epithelia
Esophagus, GI tract; liver; pancreas; respiratory system
Primary functions of epithelia
provide a boundary layer through which movement of substances can be regulated; cover or line all body surfaces, except joint cavities (line all passages that connect directly or indirectly to exterior)
Diverse functions of epithelia
protection, lining, absorption, secretion, sensation, contractility
How long does it take for intestinal epithelia to renew? Epidermal epithelia?
Intestines: 2-3 days; Epidermis: 28 days
What does epithelia contain that allows for self renewal?
stem cells, pluripotent cells w/ the capacity to divide asymmetrically, producing copies of itself and more differentiated daughter cells
What are the 5 morphological characteristics of epithelia?
- Continuous sheets, solid organs or glands held together by specialized junctions with little to no intercellular material (closely apposed)
- avascular
- basal surface sits on basal lamina
- polarized
- numerous apical PM modifications
What kinds of junctions exist in epithelia?
Zonula occludens, zonula adherens, desmosomes, and gap junctions
Function of zonula occludens
barrier
Which epithelial junctions function to provide adhesion?
zonula adherens & desmosomes
Function of gap junctions
communication
functionality of cytokeratins
insert into desmosomes and confer strength to the tissue
What must nutrients do as a result of epithelia’s avascular property?
pass from blood vessels through underlying connective tissue or lamina propria
What is the basal lamina
extracellular structure that underlies epithelia and is visible only by EM
What is the composition of basal lamina
either lamina desna alone or lamina desna AND lamina lucida; electron dense & 20 to 100mm thick
Where are the proteins that make up Basal Lamina? Where are they secreted from?
Type IV collagen, laminin, entactin & proteoglycans; the epithelial cell
How do epithelia attach to basal lamina?
via actin-integrin-laminin-type IV collagen connections
Why is it important that hemidesmosomes are strengthened? What are they strengthened by?
They are exposed to high levels of stress (ex. skin); cytokeratin-integrin-laminin-type IV collagen connections.
Where and how to basal lamina attach?
Reticular lamina va anchoring fibrils composed of type VII collagen
What are the (5) functions of basal lamina?
structural support; filter for molecules and cells; req. for cells to maintain polarity & organize mem. proteins; bind growth factors to promote differentiation and proliferation; pathway for cell migration (ex. wound healing)
