Epithelium Flashcards
Common features to all eukaryotic cells
Outer membrane, inner cytosol, cytoskeleton, membrane bound organelles and inclusions
What is the cytosol
A solution of proteins, electrolytes and carbohydrates
What are the four basic types of tissue
Epithelium, muscle, connective tissue and nervous tissue
Function of surface epithelium
Covers and lines surfaces, cavities and tubes
Function of specialised epithelial cells
Receptors for special sense organs
What are epithelia composed of
Closely aggregated, polyhedral epithelial cells with minimum intercellular space
Adhesion between epithelial cells is
Strong
Functions of epithlia
Mechanical barrier, chemical barrier, adsorption, secretion, containment, locomotion, sensation and contractility
Characteristics of epithelia
- Typically polarised
- Basal surface attached to a basal lamina
- Non-vascular
- Aggregate in sheets where the cells are closely apposed
- Cytoskeleton
- Prominent intracellular junctions
What is the cytoskeleton comprised of
Microfilaments, intermediate filaments and microtubules
What do intercellular junctions do
Link individual cells together into a functional unit
Different intercellular junctions
Occluding junctions, anchoring/adherant junction and communicating junctions
How do the filaments of the cytoskeleton work
They attach to the cell membranes and to each other by anchoring and joining proteins to form a dynamic 3D internal scaffolding in the cell
Occluding junctions
Form a diffusion barrier
Anchoring/adherent junctions
Provide mechanical strength
Communicating junctions
Allow for the movement of molecules between cells
What is a junctional complex
A close association of several types of unctions found in certain epithelial and other tissues
By what are surface epithelia classified
Cell shape, number of layers of cells, cell surface specialisations and presence of any specialised cells
Cell shape
Squamous, cuboidal and columnar
Number of layer of cells
Simple, stratified and pseudostratified
Cell surface specialisations
Microvilli, cilia and keratin
Specialised cells
Goblet cells
Microvilli
Finger-like projections of the cell membrane. They serve to increase the surface area of the cell membrane
Cilia
Motile cell processes. They serve to propel mucous or fluid over the cell surface
Keratin
Tough structural proteins. Hair, fingernails and horns are made of keratin
Exocrine glands
Product secreted towards apical end of the cell into either a lumen, duct or body surface
Endocrine glands
Product secreted towards the basal end of the cell then typically distributed by the vascular system throughout the body
Examples of exocrine glands
Lacrimal, salivary, mammary, brunner’s, sweat and sebaceuos glands, and the liver and pancreas
Examples of endocrine glands
Pituitary, thyroid, thymus and adrenal glands, and the pancreas and ovaries/testes
Examples of solid organs made of epithelium
Pancreas, liver, anterior pituitary gland, and salivary gland
