Epithelial Tissue Flashcards
What are the major roles of epithelial tissue? What are its defining characteristics?
Physical protection, permeability (semipermeable) , secretion, and sensation
Cellularity, polarity, attachment, avascular, innervation, and regeneration
Rests on basement membrane
What are the three surface of the epithelium?
Apical= where specialization can be, exterior
Basal= on basement membrane, anchors to CT
Lateral= communicate and attaches to adjacent cells
What are the defining features of tight/occluding junctions?
Impermeable= barrier (more tight junction less permeable)
Encircle cells near apical surface to prevent material movement
made of occludins and claudins
What are the defining features of gap/communicating junctions?
Fluid-filled channels that connect appoposed cells
- channels/pores for movement of ion, not restricted to epithelial
Made of connexin aggregate
What are the 3 types of anchoring junctions? What are their defining characteristics?
Adherens= apical
- interact with actin
Desmosomes= lateral
- cadherins and intermediate filaments
Hemidesmosomes= basal
- integrin and intermediate filaments that anchor to basal lamina, prevent epithelial tissue from ripping off
What type of junction is involved in food poisoning?
Tight
Bacteria impairs junction causing loss of tissue fluid into intestinal lumen= diarrhea
What type of junction is involved in gastric ulcers?
Tight
Helicobacter pylori bind to TJs in stomach increasing permeability
What type of junction is involved in pemphigus vulgaris?
Desmosomes
reduces cell-cell adhesion –> blisters of oral mucosa
What are the 3 apical specializations of epithelium?
Microvilli= cytoplasmic processes containing actin core
- SA up so absorption up
Stereocilia= long less mobile, only in epididymis and hair cells of inner ear
Cilia= highly mobile, long arrays of microtubules
What is the difference between simple, stratified, and pseudo-stratified?
simple= one layer
stratified= multiple layers
pseudo= looks stratified because of the different shapes but one layer
Where are simple squamous cells found? What are their functions? What do these look like?
Lining of blood and lymph (endothelium), serous membranes (mesothelium), aveoli, loop of henle (kidneys), various ducts
Exchange, barrier, lubrication
flattened single layer
Where are simple cuboidal cells found? What are their functions? What do these look like?
Kidney tubules, glands and ducts, terminal bronchioles, covering the ovary
Absorption, barrier, secretion
Single layer square shaped
Where are simple columnar cells found? What are their functions? What do these look like?
Auditory tubes, uterus, oviducts, stomach, SI/LI, gallbladder
absorption and secretion
single layer, more tall than wide
Where are pseudostratified columnar ciliated cells found? What are their functions? What do these look like
Lining nasal cavity, pharynx, trachea, bronchi
Absorption and secretion, debris and particulate movement (waving cilia)
one layer change shapes so looks multiple layers
Where is urothelium found? What are their functions? What do these look like?
Urinary bladder, ureter, urethra
barrier, distensible property
Transitional= contract when bladder full, pseudostratified
Where are non-keratinized stratified squamous cells found? What are their functions? What do these look like?
oral cavity, pharynx, esophagus, anus, vagina, urethra, cornea (multiple layers key because lots of abrasion)
barrier and protection
flat apical cells
Where are keratinized stratified squamous cells found? What are their functions? What do these look like?
Epidermis of skin
barrier and protection: keratin for waterproofing
no nuclei in outer most layer (web like)
Where are stratified cuboidal cells found? What are their functions? What do these look like?
sweat glands and ducts, ovarian follicles, salivary gland ducts
barrier and passageway
What is a mucous membrane? What does it line?
Epithelial tissue that secrete mucus
Lines body cavities and tubular organs, gut and respiratory
What is a serous membrane? What does it line?
Transparent two layered membrane, lubricated with fluid from serum
- mesothelium= simple squamous that comprises part of a serous membrane
Internal body cavities
- peritoneum. pericardium, and pleura
What is the difference between an exocrine and endocrine gland?
Exo= duct that releases product
endo= uses blood
What are the features of a unicellular gland? What is an example?
One cell with a gland like function - goblet cell= mucus secreting in intestines and respiratory tract
What is an acinus in a multicellular gland?
secretory cells, secretory portion
- supported by stroma of connective tissue (no functional components)
What is the parenchyma of a multicellular gland?
functional tissue of an organ
- does not include CT and supporting tissues
What is the release mechanism of a merocrine gland?
membrane bound vesicles to apical surface –> exocytosis
salivary
What is the release mechanism of a holocrine gland?
secretion accumulates within cell –> apoptosis so product and junk secreted
sebacous glands
What is the release mechanism of a apocrine gland?
Release of the apical portion of the cell, typically lipid base, not full cell damage
mammary gland
What is the difference between a simple and compound ducts?
simple= unbranched
compound= 2+ branches
What are the 4 features that can be used to identify an exocrine gland?
Shape of secretory portion (alveolar v tubular)
Shape of the duct system (simple v compound)
Nature of secretion (serous v mucous)
Mode of secretion (merocrine, apocrine, holocrine)
