4 - Tissues Flashcards
Define tissue.
A tissue is a group of cells with similar structure and function that have similar extracellular substances located between them.
What is the name of the microscopic study of tissues.
Histology.
There are four basic types of tissue. Name them.
- Epithelial
- Connective
- Muscle
- Nervous
Where in the body can you find epithelial tissue?
Epithelium covers external and internal surfaces throughout the body. Surfaces on the body include the outer layer of the skin and the lining of cavities. It also forms most glands.
There are two surfaces to epithelial tissue.
The free surface, which is not in contact with other cells, and the basal surface which is adjacent to a basement membrane.
What is the basement membrane?
It consist of a meshwork of protein molecules with other molecules bound to them.
What produces the basement membrane.
Usually both the epithelium and the underlying tissues.
What is the function of the basement membrane?
It can function as a filter and as a barrier to the movement of cells. Blood vessels also do not cross this membrane.
What are the major functions of epithelia?
- Protecting underlying structures.
- Acting as a barrier
- Permitting the passage of substances
- Secreting substances
- Absorbing substances.
One of the functions of epithelia is Protecting underlying structures. , elaborate.
Examples include the outer layer of the skin and the epithelium of the oral cavity, which protects the underlying structures from abrasion.
One of the functions of epithelia is Acting as a barrier , elaborate.
Epithelium prevents many substances from moving through it. For example, the epithelium of the skin acts as a barrier to water and reduces water loss from the body. The epithelium of the skin also prevents many toxic molecules and microorganisms to enter the body.
One of the functions of epithelia is Permitting the passage of substances , elaborate.
Epithelium also allows many substances to move through it. For example oxygen and carbon dioxide are exchanged between the air and blood by diffusion through the epithelium in the lungs.
One of the functions of epithelia is Secreting substances , elaborate.
Sweat glands, mucous glands, and the enzyme-secreting portion of the pancreas are all composed of epithelial cells.
One of the functions of epithelia is Absorbing substances. , elaborate.
The cell membranes of certain epithelial tissues contain carrier proteins that regulate the absorption of materials. For example, the epithelial cells of the intestines absorb digested food molecules, vitamins, and ions.
How is epithelia classified?
Epithelia are classified according to the number of cell layers and the shape of the cells.
Which different layer types of epithelium are there?
- Simple (single layer of cells)
- Stratified (more than one layer)
- Pseudostratified (modification of simple epithelium)
- Transitional (modification of stratified epithelium)
Simple epithelium can have different cell shapes. Which?
Squamous, cuboidal or columnar.
Stratified epithelium can have different cell shapes. Which?
Squamous (nonkeratinized or keratinized), cuboidal (rare) or columnar (rare).
Pseudostratified epithelium can have different cell shapes. Which?
Only columnar. You’ll see: pseudostratified columnar epithelium.
Transitional epithelium can have different cell shapes. Which?
Roughly cuboidal to columnar when not stretched, and squamouslike when stretched.
A squamous cell has a …. shape
flat!
A duboidal cell has a …. shape
cubelike
A columnar cell has a … shape
tall and thin, columnar…
What is the structure of simple squamous epithelium?
Single layer of flat, often hexagonal cells; the nuclei appear as bumps when viewed in cross section because the cells are so flat.
What is the function of simple squamous epithelium?
Diffusion, filtration, some secretion, and some protection against friction.
What is the location of simple squamous epithelium?
Lining of blood vessels and the heart, lymphatic vessels, alveoli of the lungs, portions of the kidney tubules, lining of serous membrane of body cavities.
What is the structure of simple cuboidal epithelium?
Single layer of cube-shaped cells; some cells have microvili (kidney tubules) or cilia (terminal bronchioles of the lungs).
What is the function of simple cuboidal epithelium?
Secretion and absorption by cells of the kiney tubules; secretion by cells of glands and choroid plexuses; movement of particles embedded in mucus out of the terminal bronchioles by ciliated cells.
What is the location of simple cuboidal epithelium?
Kidney tubules, glands and their ducts, choroid plexuses of the brain, lining of terminal bronchioles of the lungs, and surfaces of the ovaries.
What is the structure of simple columnar epithelium?
Single layer of tall, narrow cells; some cells have cilia (bronchioles of lungs, auditory tubes, uterine tubes, and uterus) or microvili (intestines).
What is the function of simple columnar epithelium?
Movement of particles out of the bronchioles of the lungs by ciliated cells; partially responsible for the movement of oocytes through the uterine tubes by ciliated cells; secretion by cells of the glands, the stomach and the intestine; absorption by cells of the intestine.
What is the location of simple columnar epithelium?
Glands and some ducts, brochioles of the lungs, auditory tubes, uterus, uterine tubes, stomach, intestines, gallbladder, bile ducts, and ventricles of the brain.
What is the structure of pseudostratified columnar epithelium?
Single layer of cells; some cell are tall and thin and reach the free surface, and oither do not; the nuclei of these cells are at different levels and appear stratified; the cells are almost always ciliated and are associated with goblet cells that secrete mucus onto the free surface.
What is the function of pseudostratified columnar epithelium?
Synthesize and secrete mucus onto the free surface and move mucus (or fluid) that contains foreign particles over the surface of the free surface and from passages.
What is the location of pseudostratified columnar epithelium?
Lining of the nasal cavity, nasal sinuses, auditory tubes, pharynx, trachea, and bronchi of the lungs.
What is the structure of stratified squamous epithelium?
Sever layers of cells that are cuboidal in the basal layer and progressively flattened toward the surface; the epithelium can be nonkeratinized (moist) or keratinized; in nonkeratinized stratified squamous epithelium, the surface cells retain a nucleus and cytoplasm; in keratinized stratified epithelium, the cytoplasm of cells at the surface is replaced by a protein called keratin, and the cells are dead.
What is the function of stratified squamous epithelium?
Protects against abrasion, forms a barrier against infection, and reduces loss of water from the body.
What is the location of stratified squamous epithelium?
Keratinized - outer layer of the skin; nonkeratinized - mouth, throat, larynx, esophagus, anus, vagina, inferior urethra, and corneas.
What is the structure of transitional epithelium?
Stratified cells that appear cuboidal when the organ or tube is not stretched and squamous when the organ or tube is stretched by fluid.
What is the function of transitional epithelium?
Accomodates fluctuations in the volume of fluid in an organ or a tube; protects against the caustic effects of urine.
What is the location of transitional epithelium?
Lining of the urinary bladder, ureters, and superior urethra.
Cells with the major function of diffusion are usually..
Flat
Cells with the major function of secretion or absorption are usually
cuboidal or columnar.
Why, most likely, are the cells with the major function of secretion or absorption usually cuboidal or columnar?
Because these tissue types have bigger cells that can hold more organelles - this makes them able to hold such functions.
What is the difference between microvili and cilia?
Microvili are cylindrical extensions of the cell membrane that increases the free surface area. Cilia propel materials along the free surface of cells.
What are tight junctions?
Epithelial cells are connected to one another in several ways, one of these is through tight junctions. They bind adjacent cells together and form permeability barriers. In this way, materials that pass through the epithelial layer must pass through the cells.
What are gap junctions?
Small channels that allow small molecules and ions to pass from one epithelial cell to an adjacent one.
What is a gland?
A gland is a structure that secretes substances onto a surface, into a cavity, or into the blood. Most glands are composed primarily of epithelium and are multicellular.
Two categories of glands exist. Which?
Exocrine and endocrine
What are exocrine glands?
Exocrine cells have ducts for secretion.
Exocrine glands can also be classified according to how products leave the cell. Which types?
- Merocrine secretion
- Apocrine secretion
- Holocrine secretion