Epithelium Flashcards
4 basic types of tissues
Epithelial
Connective
Muscle
Nervous
Location of Epithelium
Covers surfaces
Extends into all complex invaginations
Mostly cells
Parenchyma vs. Stroma
Parenchyma: Essential/Functional
Stroma: non-essential (connective tissue, blood vessels, ducts)
Functions of epithelium
Protection (chemical and mechanical)
Control of transport (absorption and secretion)
Epithelium Characteristics
Uninterrupted layer of cells
avascular (no vessels)
Polarized
Apical
⇅
Basal
*Basal layer undergoes mitosis
Where is the basement membrane? What is it also called?
Basement membrane (aka Basal Lamina )
Between epithelium and connective tissue
Basal cell layer of epithelium
Stem cells that reside closest to the basal lamina (undifferentiated)
Mitosis (renewal/turnover)
Progenitor cells (division)
Metaplasia
Adaptation of mature tissue to physical or chemical stress
Stem cells alteration
✰Can lead to cancer (neoplasia)
Paracellular vs. Transcellular transport
Paracellular - Between two cells
Transcellular - Through a singular cell
Junctions of epithelium
*Tight: Seal
- proteins: occludens, claudins, ZO proteins
*Adherens: Anchor
- proteins: actin filaments and cadherins.
*Desmosomes: anchor (velcro) mechanical stress
- proteins: Desmogleins, desmoplakin, plakoglobin
*Gap junctions: communication
- protein: Connexin.
*hemidesmosomes: anchor to basal lamina
- proteins: integrins/laminins
*blistering disorder
Classification: epithelial types
Simple (single layer) vs. Stratifies (multi-layered)
Cuboidal, columnar, squamous (low)
keratinized vs non-keratinized
Pseudostratifies columnar
Urothelium (kidneys, ureters, bladder, urethra)
-stratified
-Stretch and leak prevention
T/F: Mast cells are resident cells of connective tissue that contain many granules rich in histamine and heparin.
TRUE
mast cells are key players in the inflammatory response.
eosinophils are associated with… and …
eosinophils are associated with INFLAMMATORY RESPONSE and ASTHMA
fibroblasts secrete most of the ___
ECM
adipocytes store energy and regulate ____
metabolism
aquaporins
channels that allow water transport when they are inserted in the cell membranes
tight junctions
control paracellular transport
gap junctions
cell to cell communication
which connective tissue component is located in the ECM but not in the ground substance?
Collagen bundles!
ECM: ground substance and collagen fibers
Ground substance: fills space with fibers (collagen fibers), water, organic molecules (GAGS), proteoglycans, and glycoproteins (fibronectin, laminin).
what cell type produces hormones important for metabolism and stores energy?
adipocytes
adipocytes store energy in the form of lipid molecules
adipocytes have important endocrine and metabolic roles
- secreting hormones (adipokines- regulate energy balance)
- food intake and satiety
- inflammatory response
- metabolism of steroid hormones
what cell is involved in adhesion to the basement membrane?
Integrins
Integrins are receptors
Fibrilin and laminin are ligands (bind with integrins)
desmoplakin
component of desmosomes which mediate cell to cell attachment
cadherins
component of adherens junctions which mediate cell to cell attachment
fibrillin
component of elastic fibers
glycoprotein
secreted by fibroblasts
occludens
proteins associated with tight junctions
T/F: all epithelia will have some attachment to a basal lamina and express desmosomes
TRUE
what structural feature of the epithelial cells contributes to selective permeability and surface specialization?
polarity
apical and basal surfaces
macrophages defend against infection via ____
phagocytosis and presenting antigen to T cells
secrete cytokines and chemokines to recruit immune cells, promote inflammation, tissue repair/healing, clear dead cells/debris
what characteristic of epithelia cells gives the protective function?
tight junctions between cells that create a continuous barrier
junctions and their protein(s)
tight junctions: occludens, claudins, ZO proteins
adheren junctions: cadherins and actin filaments
desmosomes: desmogleins and desmoplakin
hemidesmosomes: integrins and laminins
gaps junctions: connexin
how do molecules pass the epithelial membrane?
