Chapter 4 Flashcards
What are tissues?
Groups of cells similar in structure that perform common or related function
What are the 4 types of tissue?
Nervous
Muscle
Epithelial
Connective
How would you prepare a tissue specimen for microscopy?
Thinly sliced and preserved to allow enough light transmission
Stained with dyes that bin to different parts of the cell in slightly different ways (so you can tell the anatomical structures apart)
What are the two ways epithelium would occur in the body?
Covering/ lining epithelium
Glandular epithelium
Where would you find covering epithelium?
On external and internal surfaces
Where would you find glandular epithelium?
Secretory tissue in glands
What functions does the epithelium do for the body? (6 of them)
Protection Absorption Filtration Excretion Secretion Sensory Reception
How do epithelium exhibit polarity?
By having an upper free apical surface and a lower attached basal surface
What components are found on the apical surface of the epithelium and what do they do?
Microvilli (brush border in intestines) - increase surface area
Cilia (some have it to move mucus out) - move particles up and out
For cilia think of the lining of the trachea (if you get dust into your windpipe you cough it out as mucus because the cilia are moving it out of the lining)
What is the basal surface of the epithelium called and what does it do?
Basal lamina
Adhesive sheet with selective filter (remember that the lamina in the nucleus allows the chromatin to anchor onto it or stick to it so this is the same concept)
Scaffolding for cell migration in wound repair (cells are mitotically active in the basal layer and die as they go towards the apical surface)
How are epithelial tissues arranged?
They fit closely together with little space between cells and hence form continuous sheets
What type of junctions would connect the epithelial cells in a tissue?
Tight junctions and desmosomes
(think about skin - desmosomes are like velcro to keep skin from tearing)
(for tight junctions there needs to be a controlled closed barrier to keep water from escaping the skin to prevent dehydration)
What defines the epithelial boundary and keeps the epithelium from tearing when stretched?
Basement membrane
contains the basal lamina and the reticular lamina which is connective tissue that supports the epithelium
Is the epithelial vascular?
No it is avascular
What supplies the epithelium with nourishment through diffusion and the sense of touch?
Nerve fibers (they are innervated) and the underlying connective tissues (they are avascular)
What stimulates regeneration of the epithelial tissue?
Loss of Apical-basal polarity and a loss of
lateral contacts
How would you classify epithelia?
By the number of cell layers and the shape of the cell
If an epithelial tissue has a single layer of column shaped cells, what would be its classification?
Simple Columnar Epithelium
If an epithelium was multilayered and had flat cells, what would be its classification?
Stratified squamous epithelium
What are the three shapes of an epithelial cell?
Squamous (flat)
Cuboidal (like a cube)
Columnar (looks cylindrical and like a column)
What does simple epithelia function in?
Absorption, Secretion, Filtration
it is a single layer of cells
Is the cytoplasm vast in a simple squamous cell?
No it is sparse
Where would you find simple squamous epithelium?
In the kidneys and lungs
(they function in rapid diffusion so glomerulus in kidneys and alveoli in the lungs)
You might also find them in the endothelium (lining of vessels and heart)
and the mesothelium (ventral serous membranes)
What are the main functions of simple cuboidal cells?
Secretion and absorption
forms the walls of smallest ducts of glands and many kidney tubules
Where would you find simple columnar epithelium and why?
The digestive tract because their primary function is absorption and secretion
(Might also find the ciliated type in the reproductive tract and respiratory tract to move mucus out of body)
How does pseudo-stratified columnar epithelium get its name?
It is made up of columnar epithelium that varies in height that gives the illusion that there is more than one layer but there is not. (same functions as the simple columnar)
What is the major role of stratified epithelial tissue?
Protection (more than one layer and cells regenerate from the bottom up so is much more sturdy than the simple epithelium)
What is the most widespread stratified epithelium?
The stratified squamous epithelium
think about how it covers the external parts of the skin and the skin is the largest organ in the body
What is the composition of stratified squamous epithelium?
The top layers are flattened squamous that are keratinized and less viable while the deeper layers that are mitotically active are cuboidal or columnar
What is the function of stratified squamous epithelium?
Protect the underlying tissues in areas subjected to abrasion (again think of skin)
Where would you find non-keratinized stratified squamous epithelium?
Linings of the esophagus, mouth and vagina
Where would you find stratified columnar epithelium in the body?
Pharynx, male urethra, lining of some glandular ducts
Where would you find stratified cuboidal epithelium in the body?
In the ducts of some of the larger glands
What is the main function for transitional epithelium and what is it composed of?
Mainly for allowing stretching in areas like the bladder. Resembles both the stratified squamous and stratified cuboidal (shape can change based off stretching)
What is a gland?
One or more cells that makes and secretes an aqueous fluid called a secretion (leaving)
How would you classify glandular epithelium?
By the site of product release (exocrine or endocrine)
Number of cells forming the gland (unicellular or multicellular)
Which glands are ductless and secrete hormones directly into the lymph or blood stream?
Endocrine
What type of vesicular transport does endocrine glands use?
Exocytosis (secretory vesicles out of cell into the blood or lymph to a target)
Explain the key points of exocrine glands (do they use ducts, where are the secretions released, are they more or less numerous than endocrine glands, give examples of some secretory products that would be released by them)?
Exocrine glands secrete their products into ducts
These secretions are released from ducts onto body surface or into body cavities
They are much more numerous than endocrine glands
SWEAT, OIL, SALIVA, MUCOUS