Lecture 2: Epithelium Flashcards
What germ layers is epithelial derived from?
mesoderm, ectoderm, endoderm (All of them)
Skin is derived from what germ layer?
ectoderm
blood vessels are derived from what germ layer?
mesoderm
Gut is derived from what germ layer endoderm?
endoderm
What are the 6 functions of epithelium?
- Protection
- Distention
- Secretion/excretion
- Absorption
- filtration
- Contraction
What are 5 characteristics of epithelia?
- strong apical - basal polarity
- avascular
- littler intercellular space
- Rests on basement membrane (LM) or basal lamina (EM)
- Has a high rate of turnover and mitosis after injury (except glands)
Describe the apical domain of the epithelium (location and cell specializations)
It is adjacent to lumen / external environment. *Microvili
- sterocilia
- cilia (motile and non motile)
Describe the lateral domain (location and cell specializations)
Adjacent to other epithelial cells.
- Occluding (tight) junctions
- Adhering junctions (belt and spot desmosomes), *Communicating (gap) juntions
Describe the basal domain of the epithelium (location and cell specializations)
Adjacent to underlying CT
- Basement membrane / basal lamina
- Hemi- desomosomes
- focal contacts
What is a brush border where is it found?
Formed by microvilli, it is in intestine and striated border in kidney tubules –> increase surface area
What is at the core of microvilli
Have core of actin filaments
Where is sterocilia found?
epididymal duct and vas deferens also sensory epithelium of the ear
Describe primary ciliary diskinesia
AKA immotile cilia syndrome –> nonfunctional/ absent dynein arms
What is the arrangement of non-motile cilia (primary cilia) and function?
9+0 –> sensor of fluid flow (mechanoreceptors) in kidney tubules
Tight juntions AKA
zonula occludens- regulates movement of materials between cells, contains occludin and claudins
Belt desmosomes AKA
zonula adherens - E-cadherin rich –> lateral adhesion between cells
FASCIA ADHERENS- cardiac muscle cells
Spot desmosomes AKA
macula adherens - localized spot attachments between cells.
Plaques - desmoplakins and plakoglobins
Crosslinkers- desmocollin and desmoglein
Communicating / Gap Junctions AKA
zonula communicantes -
connexons formed by connexins that can open and close.
What is the function of a hemi desmosome?
Anchors intermediate filaments of cytoskeleton into basal lamina
What is the function of focal contacts?
anchors actin filaments of cytoskeleton into extracellular matrix
What are the two components of basal lamina?
lamina densa and lamina rara
What is lamina densa composed of?
Type 4 collagen, entactin, nidogen, perlecan
What is lamina rara?
laminin anchored to integrin receptors
What forms the glomerular filtration barrier?
Basal lamina of endothelial cell of capillary in glomerulus fusing with basal lamina of kidney podocyte
Describe the nucleas shape in squamous, cuboidal, and columnar cells.
Squamous- flattened
cuboidal- rounded
columnar - elongate nucleus
What is the classification of respiratory epithelium?
Pseudostratified ciliated columnar
What does transitional epithelium line? (4)
Kidneys, ureters, blader, urethra (AKA urothelium)
What type of epithelium lines blood vessels and serous membranes?
Simple squamous epithelium
What type of epithelium lines ducts of glands, walls of kidney tubules, and the covering of ovary?
Simple cuboidal epithelium
What type of epithelium lines the intestine and gallbladder?
Simple columnar epithelium
Stratified squamous nonkeratinized epithelium lines what structures? (5)
oral cavity, esophagus, rectum, anal canal, vagina
What type of epithelium forms the epidermis of the skin?
Stratified squamous keratinized epithelium
What kind of epithelium lines the ducts of sweat glands?
stratified cuboidal or columnar epithelium
What is characteristic of urothelium?
umbrella cells, numerous tight junctions and discoidal vesicles (infolding of cell membrane that allow for distention)
Describe the two types of glands.
Exocrine (ducts)
Endocrine (ductless– secrete into blood vessels)
What are unicellular exocrine glands called what do they secrete?
goblet cells –> hydrophilic glycoproteins (mucus)
What are 4 mechanisms of secretion in glandular epithelium?
- Merocrine
- Apocrine
- Holocrine
- Cytocrine
Merocrine
exocytosis off apical surface in vesicles (proteins in milk)
Apocrine
Part of cytoplasm extruded with secretion (lipids in milk)
Holocrine
Cell dies –> part of secretion (Sebaceous gland)
Cytocrine
Transfers secretion to another cell (melanocyte transfers melanin into keratinocytes
