Epithelium Flashcards
Location of epithelial tissue
_Exterior surface _lines intestinal cavities _Secretory portion of glands & ducts
Characteristics of epithelial tissue
_Mainly has an exposed free surface _cells are close together and have strong adhesion _Avascular: get nutrients through diffusion
Apical Layer
_Touches the external aspect of the layer _Where secretory vesicles are located
Microvilli
_Core formed by actin filaments bound by actin binding proteins _Anchored by lateral anchoring proteins (myosin I) to villin
Villin
Amorphous apex that the actin filament are anchored to
Stereocilia
_Modified microvilli _Actin filament core _long (sometimes branching) projections _absorption in epididymus, sensory receptors in the cochlea
Cilia
_Move substances along the surface of the epithelium _Made up of axoneme and a basal body base
Primary Ciliary Dyskinesia
_Genetic defect causing malformation of cilia skeleton _Uncoordinated or absent cilia beating _Signs: Dextrocardia, impaired skull air sinuses, lack of mucus removal from lungs, infertility
Lateral Domain
Defined by the presence of cell junctions
Terminal bars
Junctional complexes visible with a microscope
Occluding cell junctions
_Typically apical portion of cell _ form sealing strands of transmembrane proteins of 2 adj cells _Typically in cells with secretory or absorption role
Zonula occludens
_Only type of occluding junction _Virtually impermeable
Anchoring cell junctions
_Provides mechanical strength and stability _Connects adj cells’ cytoskeletons
Adherens
_Anchoring junctions (Zonula & Macula)
Zonula adherens
_belt-like junction that connect actin filaments _Actin-binding proteins: vinculin & _-actinin _Catenin (peripheral protein) _ Transmembrane link protein (part of Cadherin family)
Cadherin Family
_Ca__ dependent protein that plays in important role in cell behavior control _Loss of protein associated with metastasis
Macula Adherens
_Aka desmosome _Connects intermediate filaments _provides mechanical strength, particularly in skin _Desmoplakin: the intercellular plaque that the filaments of thru _Cadherins: transmembrane proteins
Pemphigus
Autoimmune disease that attacks the desmosomes, preventing normal adhesion_causes blistering and skin falling apart
Gap Junctions
_Allow diffusion of small molecules and ions b/t cytoplasm of adj cells for communication _Intercellular channels: where diffusion occurs _Connexons: pair forms a channel _Connexins: protein subunit (6=1connexon) _Typically occur in patches
Basal Domain
_Faces the basement membrane _interacts with underlying tissue _Basement membrane + Anchoring junctions
Basement membrane
_Separates epithelium from underlying connective tissue _Basal lamina + Reticular lamina
Basal lamina
_Most external layer _Mostly collagen type IV and laminin
Reticular lamina
_Deeper layer _Mostly thin collagen fibers
Basement membrane anchoring junctions
_Focal adhesions _Hemidesmosome
Focal adhesions
_Attach actin cytoskeleton to extracellular matrix _ Actin-binding proteins (Vinculin, _-actinin) attach to MF _Peripheral protein (talin): actin-binding protein to transmembrane protein _Transmembrane protein (integrin family)
Hemidesmosome
_Connects intermediate filaments _Desmoplakin: the intermediate plaque that attaches to the ends of the IFs _Transmembrane protein (integrin family)
Simple squamous
Used as barrier, diffusion of oxygen/CO _Lining of vascular system, body cavities, parietal layer of Bowman’s capsule, alveoli
Endothelium
_Special simple squamous _lines the inner blood vessel walls and the heart
Mesothelium
_Special simple squamous _covers internal organs
Simple Cuboidal
_Barries (ducts), secretion (thyroid), absorption (kidney) _walls of ducts, kidney tubules, germinal epithelium of ovary, thyroid follicles
Simple Columnar
_Non-ciliated: GI tract, gallbladder _Ciliated: oviduct lining _Can have striated(microvilli) border _Absorption, secretion, lubrication, transport
Pseudostratified columnar
_Basal cells: rounded cells that do not reach the apical surface _Ciliated: found in respiratory tract _Non-ciliated: has stereocilia, found in epididymus (absorption)
Stratified squamous
_Barrier _Keratinized: nucleus-lacking epithelial cells on apical side _Non-Keratinized: GI and vagina
Stratified cuboidal
_Barrier/conduit _sweat glands
Stratified columnar
_barrier, conduit _Larger ducts of glands (parotid/submandibular salivary glands)
Transitional
_aka urothelium _only found in urinary system _has ability to stretch and relax
Endocrine
_product diffuses to the intercellular space/underlying connective tissue _No ducts
Exocrine
Secrete into ducts/spaces lined with epithelium
Unicellular glands
Individual secretory cells within non-secretory epithelium
Multicellular glands
_Glands composed of more than one cell _Secretory + duct
Alveolar/Acinar gland
Shaped like a flask
Tubular gland
Shaped like a tube (often mucous)
Tubuloalveolar gland
Tube with a flask-shaped dilation
Myoepithelial gland
_Contractile cells with contractile proteins (myosin) _contract to expel secretions out of gland _Sweat, salivary, mammary gland
Merocrine gland
_Membrane bound vesicles take substances to plasma membrane (exocytosis)
Serous product
_Thin, watery, protein-rich secretion _Acini are more rounded in shape _Pancreas/parotid salivary gland
Mucous product
_Made of mucins: long chains of negatively charged carbs attached to a protein core _Lubrication and protection _Acini typically tubular _Goblet cells, soft palate glands, Brunner’s gland
Seromucous gland
_Both serous and mucous product _have mucous tubules capped with serous demilunes
Apocrine
_Pinching of apical cytoplasm _Mammary glands
Holocrine
_Whole cell goes through apoptosis to realize all contents _Sebaceous glands of the skin
Carcinoma
Cancer from barrier epithelium
Adenocarcinoma
Cancer from glandular epithelium
Goblet Cells
Unicellular mucous glands present in GI tract and trachea, pale granular cytoplasm/arrowhead-shaped nuclei
Crypts of Lieberkühn
Simple, tubular glands that extend to the lumen
Brunner’s gland
Branched tubular glands in the submucosa of the duodenum
