Epithelial Tissue Flashcards
Avascular tissue is composed of cells that: (4)
o cover the exterior body surfaces
o line the internal closed cavities including the vascular system
o line body tubes that communicate with the exterior (GIT, urogenital and respiratory tracts)
o form secretory portions and ducts of glands
What are the defining characteristics of epithelial tissue?
- Cells are in close apposition and have little extracellular matrix
- Functional and morphologic polarity
o Cells have 3 domains- apical domain, lateral domain and basal domain - Cells adhere strongly by specialized cell junctions
- Cell basal surface attaches to basement membrane
What is epithelioid tissue? (2)
o Cells that are closely apposed and have a basement membrane but lack a free surface
o Present as most endocrine glands
How does epithelium function as a selective barrier?
Epithelia covering and lining surfaces form a sheet-like cellular investment that separates underlying connective tissue from the external environment, internal cavities or fluid connective tissue (blood or lymph)
What are the functions of epithelia? (5)
How does the classification of epithelial tissue take place?
Simple squamous:
Image
Locations
Functions
Simple cuboidal:
Image
Locations
Functions
Simple columnar:
Image
Locations
Functions
Pseudostratified columnar:
Image
Locations
Functions
Stratified squamous:
Image
Locations
Functions
Stratified cuboidal:
Image
Locations
Functions
Transitional (urothelium):
Image
Locations
Functions
- Epithelia may also be classified according to its _____ specialisations if present
- Some exocrine glands have cells that are _____ in shape
- These cells are still classified as either columnar or cuboidal
apical
pyramidal
In stratified epithelium:
o The cell ____ and ____ vary from layer to layer
o Only the shape of the cells that form the surface layer is used in classification.
height
shape
What are the SPECIAL classifications of epithelia? (2)
- Pseudostratified epithelium
o Nuclei are at different levels and some cells do not reach the free surface
o Since all cells rest on the basement membrane, it is regarded as a simple epithelium - Transitional epithelium (urothelium)
o Stratified epithelium with special
Simple squamous epithelia in specific locations:
1. Endothelium-
2. Endocardium-
3. Mesothelium-
lining of the blood and lymphatic vessels
lining of the ventricles and atria of the heart
lining of the walls of the abdominal, pericardial and pleural cavities
- Specific _____ characteristics are associated with each cell surface
- The free apical domain is always directed toward the exterior surface of the lumen of an enclosed cavity or tube
- The lateral domain ________ with adjacent cells and has specialised attachment areas
- The basal domain rests on the ______ _____ anchoring the cell to underlying connective tissue
biochemical
communicates
basal lamina
What are the Apical Domain Specializations? (3)
- Microvilli
- Stereocilia (stereovilli)
- Cilia
What are microvilli? (5)
- Cytoplasmic processes containing a core of actin filaments
- Functions in increasing surface area for absorption
- In kidney tubules- brush border
- In GIT- striated border
- Also located in brain ependyma
What are Stereocilia (stereovilli)? (3)
- Microvilli of unusual length (very long)
- Functions in facilitating absorption and mechanoreception
- Limited to male reproductive system and sensory hair cells in the ear
What are cilia? (4)
- Motile cytoplasmic processes
- Contains the motor protein dynein
- Core of microtubules in 9+2 pattern
- Functions in transportation
Where are cilia found? (4)
o Oviducts
o Trachea and bronchi
o Brain ependyma
o Olfactory epithelium
Zonula Occludens (tight junction):
Image
Cytoskeleton Component
Functions
Zonula Adherens:
Image
Cytoskeleton Component
Functions
Macula Adherens (desmosome):
Image
Cytoskeleton Component
Functions
Focal adhesions vs Hemidesmosomes
Image
Cytoskeleton Component
Functions
Gap junction (nexus)
Image
Cytoskeleton Component
Functions
True or false
Basement membrane
* Visible on light microscope with Periodic Acid-Schiff staining technique as magenta
True
What is the structure and composition of the basal lamina? (2)
o Structural attachment site for overlying epithelial cells and underlying connective tissue
o Composed of laminins, type IV collagen, proteoglycans and glycoproteins
What is the function of basal cell membrane infoldings? (4)
- Increase surface area of basal domain
- Allows for more transport proteins and channels to be present
- Prominent in cells that participate in active transport of molecules (kidney tubules and salivary
glands) - Orientation of mitochondria together with infoldings results in striated appearance
What are the staining techniques?
What are the types of Glandular Epithelium?
Classification by mode of secretion: (3)
- Merocrine secretion
- Apocrine secretion
- Holocrine secretion
What is Merocrine secretion? (4)
- Delivered in membrane-bound vesicles to the apical surface
- Vesicles fuse with cell membrane
- Contents are extruded via exocytosis
- Most common mode of secretion
What is Apocrine secretion? (3)
- Product is release in apical portion of the cell
- A thin layer of cytoplasm within an envelope of cell membrane pinches off from the cell
- Found in lactating mammary gland and armpit and groin area
What is Holocrine secretion? (4)
- Product accumulates within the maturing cell
- The cell undergoes apoptosis and lyses
- Product and cell debris is released into the lumen of the gland
- Found in sebaceous glands and tarsal (Meibomian) glands of the eyelid
What are the types of simple glands?
What are the types of compound glands?
Simple tubular gland:
Image
Typical Location
Features
Simple coiled tubular gland:
Image
Typical Location
Features
Simple branched tubular gland:
Image
Typical Location
Features
Simple alveolar gland:
Image
Typical Location
Features
Simple branched alveolar gland:
Image
Typical Location
Features
Compound tubular gland:
Image
Typical Location
Features
Compound alveolar gland:
Image
Typical Location
Features
Compound tubulo-alveolar gland:
Image
Typical Location
Features
What is mucus secretion? (6)
What is serous secretion? (5)
Where is Mucoserous found?
Found in submandibular (tubule-alveolar) glands
What are Myoepithelial cells? (6)
- Contractile
- Have actin filaments
- Surround SEPs
- Located in between basement membrane and basal part of secretory cells
- Have a squashed appearance
- Stain darkly
