Lab -Tissues Flashcards
Four primary tissue types and their roles
the EPITHELIAL tissue:
covers the body surfaces; lines hollow organs, ventral body cavities and ducts and forms glands.
the CONNECTIVE tissue:
protects and supports the body and its organs, binds organs together, stores energy and provides immunity.
the MUSCLE tissue:
is responsible for movement and the generation of force.
the NERVOUS tissue:
carries information very quickly from one side of the body to the other.
2 basic types of epethilium
covering and lining epithelia
glandular epithelia
Where you can find Covering-lining epethilial cells :5 places
form a continuous layer over all the free surfaces of the body:
o the outer layer of the skin;
o the inner surface of the digestive and respiratory cavities;
o the inner surface of the heart and blood vessels;
o the walls and the organs of the closed ventral body cavities;
o the ducts of the exocrine glands.
What are the histological characteristic common to all epethilial tissues
- They are made of many cells close to each other (there is little extracellular material between epithelial cells).
- Several types of junctional specializations unite adjacent epithelial cells (tight junctions, desmosomes and gap junctions).
- With the exception of endocrine glands, o All epithelia have one free surface, called the apical surface, which is exposed at the body surface or at the lumen (space) of the body cavity, duct, tube or vessel.
o The lower surface of an epithelium (or basal surface) rests on a basement membrane: a non-living adhesive material secreted by the epithelium and the underlying connective tissue.
o There are no blood vessels within the epithelial layer.
o These cells are often characterized by frequent cell division because they are exposed to wear and tear and injury, necessitating replacement
Covering epethilium functions
- Epithelia protect underlying tissues against physical damage, drying out, chemical injury and infection.
- Epithelia allow and regulate the passage of materials (diffusion, absorption, filtration, secretion, excretion) into and out of the deeper tissues of the body which they cover or line. Oxygen, water, food, and waste must pass through one or more epithelial layers.
- Specialized epithelia form sensory parts of organs such as the eye, ear, mouth (taste buds), and nose (olfactory epithelium).
WHat is the material secreted by mot glands and some examples of products
The material secreted is usually a watery fluid containing substances such as salts, enzymes, hormones, mucus, fats, etc. The functions of glandular secretions are exceedingly diverse. Milk, insulin, sweat, saliva, calcitonin, tears and bile are all products of glands.
The classification of covering and lining epithelium is based on two or three features ___
- The number of cell layers
- The shape of cells
- Specialization of their cell surfaces (cilia, microvilli,etc.)
Two subsclasess in number of cell layers
one layer: simple epithelium
o several layers: stratified epithelium.
Classification of epethilium according to its shape
flat: squamous epithelium,
o square: cuboidal epithelium,
o rectangular: columnar epithelium,
o if the shape changes depending of the degree of stretching of the tissue: transitional epithelium.
Most often, it is very hard to distinguish the cell’s boundary on a light photomicrograph.. Nuclei are flat and parallel to the free surface: type of epithelium?
Squamous epithelium
Nuclei are oval and parallel to the axis of the cell and situated at its base: type of epithelium
Columnar
the nuclei are round and situated in the middle of the cell: type of epithelium
cuboidal epithelium.
Describe simple epithelium: how many cell layers, where found, function
Being composed of one layer of cells only, they are very thin. They are found in areas of minimum wear and tear. Their main function is to allow passage of substances between the lumen and the surrounding tissues.
Describe stratified epithelium: how many cell layers, function
Being composed of several layers of cells, they are very thick. Their main function is to protect the tissues that they cover. The shape of the cells closest to the basement membrane is quite different from that of the cells at the top, near the lumen.
how can you further classify the stratified epithelia? if they have different type of cells in the base and int he lumen
stratified epithelia are further classified according to the shape of the cells at the free surface.
Simple squamous epithelium has how many layers, what nucleus
One layer of flat cells (one flat nucleus)
Where simple squamous epithelium is found
in the alveoli of the lungs, in the kidney glomeruli, in the lining of the heart, blood vessels and lymphatic vessels and in the lining of the ventral body cavities
Structure of simple squamous epithelium allows it (function)
Because this epithelium is the thinnest of all, it is well adapted for diffusion (for example gas exchange between alveoli and blood in the lung or exchange of waste and nutrients between blood and surrounding tissues), filtration (of plasma in the kidney glomeruli to produce urine), and secretion (of a lubricating substance in the lining of the body cavities).
Simple cuboidal epithelium is composed of
one layer of cuboidal cells (having one round nucleus).
Where simple cuboidal epithelium is found
small glands, kidney tubules and ovary surface.
Function of simple cuboidal epithelium
adapted for secretion and absorption of substances (for example to give urine its final composition, it moves substances in and out of the kidney tubule).
Structure of simple squamous epithelium
composed of one layer of columnar cells (having one oval nucleus). They can be ciliated or non-ciliated.
What structure does non-ciliated simple columnar epithelium has and what is its function
The non-ciliated, simple columnar epithelium contains microvilli on the apical surface of its cells. Microvilli increase the surface area of the epithelium
Where non-ciliated simple columnar epithelium is found
lining the digestive tract and is involved in absorption of digested food products and in secretion of mucus, enzymes and other substances. It is also found lining the ducts of some glands.