Epithelial Tissue Flashcards
What is the primary function of epithelia?
Act as a barrier and lines all body surfaces and tissues
What are the additional functions of epithelia and where are they found?
Protection from mechanical abrasion found in skin and oral cavity
Diffusion of gases, nutrients and waste between blood and surrounding tissues found in lungs and blood capillaries
Absorption of nutrients in the gastrointestinal tract/renal tubules
Secretion of sweat, mucus, enzymes, hormones in glands and ducts
How are epithelial cells arranged?
Continuous sheets of tightly bound cells. Epithelial cells are polarised. Apical surface is the top of cell, facing the external surface. Basal surface is bottom of cell, facing the internal surface. No passage through epithelia as cells are bound together.
Sit on top of basement membrane usually over a vascular connective tissue
What are desmosomes?
Desmosomes are strong junctions that anchor adjacent cells together, they ensure epithelial tissues can stretch and maintain contact
What does a tight junction do?
Tight junctions at the lateral sides of the cells can create an impermeable layer. Prevents water passage
How can epithelial structure differ?
Shape, Number of layers, Apical specialisations
Describe the three shapes
Squamous - appear flat and wide
Cuboidal - appear square with similar height and width
Columnar - taller than wider
What is the difference between desmosomes and hemidesmosomes
Desmosomes - they hold together adjacent cells
Hemidesmosomes - they hold cells to the basement membrane
What is simple epithelia?
Simple epithelia consists of a single layer of cells
They are almost always found at interfaces involving select diffusion, absorption and/or secretion
Provide little protection against mechanical abrasion so are not found at surfaces subjected to stress
What is stratified epithelia?
Epithelium consisting of two or more layers of cells
Have a protective function
Degree of stratification related to kinds of physical stresses to which the surface is exposed
Poorly suited for absorption and secretion as they are thick
What is pseudostratified?
Single layer of cells that appear stratified
Nuclei at different heights and not all cells reach apical surface
What is transitional stratified and where is it found?
Transitional stratified epithelia are where the cells are not uniform.
They support organs where organs where stretch and recoil is important such as the bladder
Where is a simple columnar ciliated found?
female reproductive tract (cilia transport ovum from ovary to uterus
Where is a pseudo stratified columnar ciliated found?
respiratory tract
What are the apical specialisations and where are they found?
Microvillifound in small intestines for absorption, it increases apical surface area
Ciliafound in respiratory tract, move mucus and matter for movement (motility)
Keratin isa strong protein with rough layer for protection. found in skin, hair and nails
