Types of tissue and their functions in the human body

by demiparker__ (student)

Epithelial tissue

Simple squamous:

Simple squamous epithelial cells are thin and flat (the thinnest of all epithelial cell-types), which allows them to have a large surface area that is exposed to the lumen on one side (the apical surface), and to the basement membrane on the other basolateral surface. The cells, scale-like in appearance, tend to have larger, elliptically-shaped nuclei. As a simple type of epithelium, simple squamous epithelium is one cell-layer thick, and thus every cell of the tissue comes in direct contact with the basement membrane. As with other types of epithelia, simple squamous epithelial cells are bound together by tight junctions, forming a selective barrier, which is crucial to its function. Simple squamous epithelial cells function as mediators of filtration and diffusion. Due to their simple and thin construct, they allow for easy transmembrane movement such as across the membrane, and through the cell of small molecules. Some molecules, such as oxygen and carbon dioxide diffuse freely across the simple squamous epithelia according to concentration gradients. Other molecules, such as ions, utilize transmembrane protein channels to diffuse across the cells; therefore, the types of proteins that are present in a given simple squamous epithelial tissue partially determine the function of that tissue. Therefore, the simple squamous epithelia help to determine what is able to move from the lumen and into the bloodstream the capillary bed is under the basement membrane, and vice versa.

Stratified squamous:

Stratified epithelium is also lining the tissue which provides protection for underlying tissues. Stratified epithelia are normally found in places where there is a great deal of wear and tear. Frequently, the outer surface of these epithelia is sloughed off and replaced by cells below it. Thus, the deeper layers of such epithelia are mitotically active. One of the most common types of stratified epithelium is stratified squamous. There are two types of stratified squamous epithelium. In areas where the tissue is subjected to drying it may be keratinized. In keratinized stratified squamous epithelium the outermost layer is composed of tightly packed dead cells filled with the protein keratin. Keratin is the same protein which makes up hair and fingernails. The layer of keratin-filled cells acts as water-proofing. The stratified squamous epithelium you will look at in human skin is keratinized. Later in the semester you will look at non-keratinized stratified squamous epithelium in the esophagus.

Simple cuboidal:

The term ‘cuboidal’ might seem confusing if you were to look at the apical surface of cuboidal epithelial cells and only see hexagonal shapes. Despite this external appearance, a cut that is perpendicular to the surface of the cells would show that the cells are equally wide as they are tall, creating a square profile with a spherical nucleus at its centre. Simple cuboidal cells are classified as simple since they consist of only a single layer of cells. Depending on their location, some simple cuboidal cells, such as the ones lining the surface of the lines the lumina of convoluted tubules in the kidney, may have microvilli on their surface (not shown in figure). By lining the surface of various ducts of various glands and organs, simple cuboidal cells are able to provide a layer of protection from abrasion, foreign particles, invading bacteria and excessive water loss due to its selective permeability to the underlying tissue. In the kidney tubules, the cells aid in the absorption and transport of filtered substances. In the kidney tubules, the cells aid in the absorption and transportation of filtered substances.

Connective tissues

The blood:

Blood is a combination of plasma which is a watery liquid and it is also has cells that float about in it which is why it is called a connective tissue. It is a specific bodily fluid that supplies essential nutrients and substances for our body such as oxygen, sugar and hormones to our cells, and carries waste away from those cells. This waste is finally flushed out of the body in urine, sweat and the lungs. Blood also contains clotting agents; this is caused by platelets clumping together when we bleed ...