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Histology Epithelial Tissue

Marissa Alvarez Histology Graduate Englisch 33 Karten

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1Where is this epithelium found, what are its important features and how does it function within its organ?Esophagus & oral cavity
stratified squamous
**lubricated protective lining
2Extent of epithelial tissue (epithelial tissue is EVERYWHERE)Epidermal outer surface of skin
Entire GI track
Entire airway
Urinary track
Reproductive tracks
Dispersed small glands
Major internal organ glands, including liver and pancreas
Lines entire blood vessel and lymphatic systems
Lines internal body cavity and many organs
3Major Functions of Epithelium**Protection**
Secretion
Sensory Reception
Absorption
Excretion
Reproduction
4Diseases directly related to epitheliaCancer:
Pancreatic ductal adenocarcinoma
Breast cancer from the lactiferous duct
Basal cell carcinoma of the epidermis
Metastatic melanoma of epidermal melanocytes
Influenza:
infection of respiratory epithelium
Reflux disease:
acid erosion of esophageal epithelium
Renal failure:
damage to epithelial filtration barrier
Cystic fibrosis:
genetic defect in chloride channel
5General Features of Epithelial TissuesCovers surfaces or lines cavities
Rests on a basement membrane
Lacks direct vascular supply
Contains little or no extracellular matrix
Cells linked by junctional complexes
Polarized
Forms exocrine and endocrine glands
6Classification of Epithelia1. Cell Layers
2. Cell Shape
71. Number of cell layersOne layer: simple
Two or more layers: stratified
All cells rest on basement membrane but not all cells reach the surface: pseudostratified
Specialized multilayer: transitional
82. Cell Shape Shapes of cells in SIMPLE epitheliumSquamous
Cuboidal
Columnar
9Shapes of cells in SIMPLE epithelium SQUAMOUS-lining of blood vessels
-FLAT, long-hollow cell
-Larger, flat nuclei
ex: endothelium of arteriole
10Shapes of cells in SIMPLE epithelium CUBOIDAL-cube shaped
ex: renal collecting tuble
11Shapes of cells in SIMPLE epithelium COLUMNARTall cells
ex: Gall bladder
12REMEMBER! Epithelia are named based on the cell shape of thesuperficial / OUTSIDE layer
13Shape of cells in STRATIFIED epithelia Stratified squamous
14Shape of cells in STRATIFIED epithelia Stratified cuboidal
15Shape of cells in PSEUDOstratified epithelia
16Shape of cells in TRANSITIONAL epithelia***Transitional epithelium is an exception: the name is derived from a functional change in height, not the shape of the surface cells.
"pillow top"
17Major types of epithelia SIMPLE Squamous Endothelium VS Mesothelium
18Major types of epithelia Stratified squamous, keratinized: SKIN
19Major types of epithelia SIMPLE Cuboidal Kidney tubules, thyroid gland (ducts)
20Major types of epithelia Simple columnar with BRUSH border and GOBLET cells: (small intestine)
21Apical Cell surface specializations: Microvilli (short, straight, and stiff, filled w/actin)Microvilli are NON-MOTILE and only 0.5-1.0 µm in length
Internal actin microfilaments
are linked to each other,
the membrane and the
terminal web
Cells of the small intestine
and renal proximal tubule
have thousands of microvilli
per cell creating a BRUSH OR
STRIATED BORDER
**The main role of microvilli is
to INCREASE SURFACE AREA
22Apical Cell surface specializations: Cilia (much longer, can MOVE, strong, & diff. composition)Cilia are found on many cell types especially in the UPPER AIRWAY and oviduct
Cilia are up to 10 µm long and usually beat in one direction
MOTILITY
23Sensory Specialization: Taste Buds
24How do epithelial cells attach and communicate?Epithelial cells are joined at the lateral surfaces by the JUNCTIONAL COMPLEX
Tight junctions (TJ): more narrow, barrier b/w inside & outside of cell
Zonula adherens (ZA): belt of actin
Desmosomes (D): a well, prevents from sloughing off
are often found near the apex of the cell
Hemidesmosomes (HD) anchor the epithelia to the basement membrane (BM)
25Gap junction (communicating junction)Gap junctions provide 1nm gated
channels between adjacent cells
Small molecules and ions <1.5 kDa
can pass through open channels
**Connexins!
26GLANDS Specialized epithelial structures Exocrine VS EndocrineExocrine:
secrete products via DUCTS onto the epithelial surface from which they originated
EX: Pancreas
Endocrine:
ductLESS; secrete products into blood vessels, lymphatic vessels, or surrounding space for distribution
27Formation and classification of glandsEpithelial structures specialized for secretion
Exocrine defined by BOTH duct and secretory unit
Endocrine are ductLESS glands
28Single-cell EXOcrine gland: the goblet cell-secretes mucous
-uses ducts
29MORE EXOcrine Gland examples Tubular gland of colon & Sweat Gland
30Example of Branched Exocrine Gland: Tracheal glands-more complex, specialized
-dual exocrine gland (mucous and protein)
31Endocrine Single Cell endocrine, paracrine, autocrine, intracrine
32ENDOcrine Multicellular Pancreas Islet (no secretory ducts, blood vessels present) & Thyroid (simple cuboidal epithelium)
33Exam Question What Type of Epithelium is this? A. Stratified squamous B. Simple cuboidal C. Simple squamous D. TransitionalB. Simple cuboidal
(kidney tubules & thyroid gland)