Epithelium and Connective Tissue Flashcards
Describe an epithelial tissue
-forms barriers between the inside and outside world
-also forms between compartments within the body
-it covers exposed body surfaces
-lines organs, cavities and tubes
-not vascularized
Do epithelial cells form all glands of the body?
-yes
Describe connective tissues
-links tissues and organs together
->provides structural and metabolic support
->stores energy
->forms the immune system
What are the characteristics of epithelia
-continuous
-avascular but richly innervated
-they rest on a basal lamina
-little extracellular matrix
-polarized
->organelles are not homgenous
->apical and basolateral surfaces differ in polarity and function
Does epithelia have a high regeneration rate?
-yes
->they reproduce all the time
How do you classify epithelia
-one layer of epithelial cells=simple
-more than one layer=stratified
-shape is determined by the apical membrane layer
->shape of the epithelia determines the function
->for example, the lungs will have simple squamous epithelia for gas exchange
->columnar epithelia increases surface area and is present for villi
Describe a simple squamous epithelium
-single layer of flat cells
-lines body cavities(mesotheliu)
->secretes lubricating substance to reduce friction
-lines heart chambers and blood vessels(endothelium)
->controls vessel permeability
-lines sites of gas exchange in the lungs
->allows material to pass by diffusion
Describe simple cuboidal epithelium
-single layer of cells where height equals width
-it is found in glands and their ducts
-lines portions of the kidney
->where secretion and absorption occurs
Describe pseudostratified columnar epithelium
-nuclei appear at multiple levels
-all cells touch basal lamina but not all reach the apical surface
-they are found in the respiratory system
->function is for protection, secretion(mucus) motolity
Describe the stratified squamous epithelium
-stratified cells and outermost layer is squamous
->found where mechanical stresses are severe
-forms outer layer of skin(keratin to deal with dehydration)
->keratin is also a very hard protein
-lines oral cavity, esophagus, anus and vagina
->provides protection against abrasion, pathogens and chemicals
->anything associated with the outside world
Described the stratified cuboidal epithelium
-two to three layers of cells with outermost layer of cells of equal height and width
-it is relatively rare
->line larger ducts of glands
-found in ducts of sweat and mammary glands
->both of these glands are involved in secretion
Describe the simple columnar epithelium
-single layer of cells that are taller than they are wide
-lines the digestive tract
->provides absorption, protection and can secrete mucus and enzymes
Describe the stratified columnar epitheliym
-two to multiple layers of cells
->height of outer layer of cells greater than the width
-relatively rare intermediate location
->associated with ducts where there is change in function
Describe transitional (urinary) epithelium
-multiple layers of cells
-outermost cells large and dome shaped
-changes appearance with stretching
-these are only found in urinary tract
->expands and protects
Describe the formation of glands
-it forms at the epithelia cells
->it forms in the connective tissue and is usually cuboidal
->the cells in the gland release some sort of secretion
->if the cells are associated with a duct, it will be referred to as an exocrine gland
-if the connecting cells dissapear, secretions are released into blood vessels
->it will be referred to as an exocrine gland
