TISSUES Flashcards
(19 cards)
Mention one disease that affects Tissues
Gluten enteropathy also called celiac disease. This happens as a result of an inappropriate immune response to gluten (protein found in wheat and grains). Basically diarrhea because the intestinal lining is unable to absorb water and nutrients.
Describe the general make up of a tissue.
A tissue is a group of cells with similar structure and function that have similar extracellular substances located between them.
The microscopic study of tissues is called
Histology
Changes in tissues can result in what
Development, growth, aging, trauma or disease.
Give examples of tissue changes
Skeletal muscles enlarge because skeletal muscle cells increase in size in response to exercise. Also reslduced elasticity in blood vessel walls in old people results from gradual changes in connective tissues. Also cancer is an example of changes in tissues that can only be identified by microscopic examination
What are the 4 basic types of tissues
Epithelial
Connective
Muscle
Nervous
Describe or explain the Epithelial tissue or Epithelium
It is responsible for covering the the external and internal surfaces of the entire body. example the outer layer of the skin and the lining of the cavities like the digestive tract, the airways and the blood vessels.
What is the basement membrane
It can function as a filter and as a barrier, to the movement of cells. Example if some Epithelial cells are converted to cancer cells the basement membrane can for some time prevent the spread of the cancer into the underlying tissue.
What are the functions of the Epithelial tissue
1.Protecting underlying structures eg. The outer layer of the skin and the Epithelium of the oral cavity.
2. Acting as a barrier eg. Epithelium prevents many substances from moving through it. The Epithelium of the skin acts as a barrier to water and reduces water loss from the body.
3. Permitting the passage of substances eg it allows many substances to move through it. Oxygen and carbon dioxide are exchanged between the air and blood by diffusion through the Epithelial tissue in the Lungs.
4. Secreting substances eg. Sweat glands, mucous glands and enzyme-secreting portion of the Pancreas are all composed of Epithelial cells.
5. Absorbing substances eg. The cell membranes of certain Epithelial tissues contain carrier proteins that regulate the absorption of materials. The Epithelial cells of the intestines absorb digested food molecules, vitamins and ions.
How is the Epithelia or Epithelial tissue classified
It is classified according to cell layers and the shape of cells
Types of classification of Epithelial tissue
Based on Number
Simple Epithelium: consists of a singular layer of cells.
Stratified Epithelium: consists of more than one layer of Epithelial cells sitting on top of others.
Based on shape
Squamous (flat)
Cuboidal (cubelike)
Columnar (tall and thin)
example of an Epithelial tissue name could be “simple squamous”
Explain a simple squamous Epithelium
A single layer of thin flat cells. Some substances easily pass through and others do not. Example Aveoli consists of simple squamous epithelium allowing oxygen from the air to diffuse into the body and carbon dioxide to diffuse out of the body into the air. Also the the Kidneys contain filtration membranes that forms thin barriers that allows only small molecules to pass through but not large molecules. This allows water from blood to be filtered through these barriers which is a major step in urine formation. The large molecules such as proteins and blood cells remain in the blood vessels of the Kidneys.
It also prevents abrasion or damage from friction between the surfaces of organs by producing a fluid secretion that lubricates the outer surfaces of organs.
Explain the simple cuboid epithelium
A single layer of cubelike cells that carry out active transport, facilitated diffusion and secretion. It is bigger ( has a greater volume) than the simple squamous epithelium and contains more cell organelles. The kidney tubules has a large portions of their walls composed of simple cuboidal epithelium. These cells secrete waste products into the tubules and reabsorb useful materials from the tubules during urine formation. Also responsible for moving mucus over the free surface.
Explain the simple columnar epithelium
Is a single layer of tall thin cells. These cells are large and contain organelles that enable them to perform complex functions. It is responsible for the production and secretion of mucus and digestive enzymes.
The columnar cells then absorb the digested foods by active transport, facilitated diffusion or simple diffusion.
Explain pseudostratified columnar epithelium
It is a special kind of simple epithelium that appears stratified but is not. It consists of one layer of cells, with all the cells attached to the basement membrane. But it looks like two or more layers of cells because some of the cells are tall and reach the free surface while others are short and do not reach the free surface. It is found in the auditory tubes and the Airways like the nasal cavity, nasal sinuses, pharynx, trachea and bronchi. It secretes mucus which covers its free surface. Cilia (hair-like structures) on the free surface move the mucus and debris that accumulates example is when mucus is moved down the throat where it is swallowed.
Explain the of stratified squamous epithelium
structure:
It is a thick epithelium because it consists of several layers of cells that are cuboidal in the basal layer and progressively flattened toward the surface. The epithelium can be non-keratinized or keratinized. (In the non-keratinized stratified epithelium the surface cells retain a nucleus and cytoplasm. In the keratinized stratified epithelium the cytoplasm of the cells at the surface is replaced by a protein called keratin and the cells are dead.
Function:
Protects against abrasion, forms a barrier against infection and reduces loss of water from the body.
Location:
Keratinized - outer layer of the skin.
Nonkeratinized - mouth, throat, larynx, esophagus, vagina, anus, inferior urethra and corneas.
Explain the transitional epithelium
Structure:
Stratified cells appear cuboidal when the organ is not stretched and squamous when the organ is stretched by fluid
Function:
Accommodates fluctuations in the volume of fluid in an organ. Protects against the caustic effects of urine.
Location:
Lining of urinary bladder, ureters and superior urethra
What are the structural and functional relationships of cells
Functions of layers:
Controlling the passage of materials through the epithelium and protecting the underlying tissues.
example the simple epithelium with its single layer of cells is found in organs that primarily function to move materials. Like the diffusion of gasses across the wall of the aveoli of the Lungs, filtration of fluids across the filtration membranes in the Kidneys, secretion from the glands and Nutrient absorption by the intestines.
The stratified epithelium on the other hand, has many layers and is well adapted for its protective functions. Example the stratified squamous epithelium is found in areas of the body where abrasion can occur, such as in the skin, anal canal and vagina.
Functions of shape:
Cells are normally flat and thin when the function is diffusion such as in the alveoli of the Lungs or filtration such in kidney glomeruli.
Cell with a cuboidal or columnar shape mainly function for secretion or absorption. They are larger because they contain more organelles. Example the stomach is lined with simple columnar epithelium and they contain many secretory vesicles filled with mucus. This protects the stomach lining against the the digestive enzymes and acid produced in the stomach. When this mechanism fails ulcer occurs.
Explain the free surface
The free surface faces away from the underlying tissues. The free surface can be either smooth or lined with microvili or cilia.
A smooth free surface reduces friction as materials move across it. For example the lining of blood vessels is simple squamous epithelium with a smooth surface which reduces friction as blood flows through the vessels.
