Okay, today we will discuss on organism's basic unit of structure and function. In life structural hierarchy, cell is the smallest unit of organization that can perform all activities required for life. In fact, the actions of organism are all based on the functioning of cells.
Cells are organized into tissue, groups of cells with a similar appearance and a common function. Different types of tissues are further organized into functional units called organs. Groups of organs that work together, providing an addition level of organization and coordination, make up an organ system.
The specialized and complex organ systems of animals are built from limited set of cell and tissues types. There are four main types of animal tissues which is ; epithelial, connective, muscle, and nervous. However, today we will be exploring more on epithelial tissues :)
Occurring as sheets of cells, epithelial tissues or epithelia cover the outside of the body and the line organs and cavities within the body. Because epithelial cells are closely packed, often with tight junction, they function as a barrier against mechanical injury, pathogens, and fluid loss. Epithelia also form active interfaces with the environment. For example, the epithelium that lines the nasal passages is crucial for olfaction, the sense of smell.
Stratified Squamous Epithelium.
A stratified squamous epithelium is multi layered and regenerates rapidly. New cells formed by division near the basal surface push outward, replacing cells that are sloughed of. This epithelium is commonly found on surface subject to abrasion, such as the outer skin and the linings of the mouth, anus, and vagina.
Pseudostratified Columnar Epithelium.
A pseudostratified epithelium consists of a single layer of cells varying in height and the position of their nuclei. In many vertebrates, a pseudostratified epithelium of a ciliated cells forms a mucous membrane that lines portions of the respiratory tract. The beating cilia sweep the film of mucus along the surface.
Simple Squamous Epithelium.
The single layer of platelike cells that form a simple squamous epithelium functions in the exchange of material by diffusion. This type of epithelium, which is thin and leaky, lines blood vessels and the air sacs of the lungs, where diffusion of nutrients and gases is critical.
Simple Columnar Epithelium.
The large, brick shaped cells of simple columnar epithelium are often found where secretion or absorption is important. For example, a simple columnar epithelium lines the intestines, secreting digestive juices and absorbing nutrients.
Cuboidal Epithelium.
A cuboidal epithelium, with dice shaped cells specialized for secretion makes up the epithelium of kidneys tubules and many glands, including the thyroid gland and salivary glands.
So, I think that is all for today on epithelial tissues. I will get back to you soon with the new thing to be discuss about, InshaAllah. So, see yaa Assalamualaikum :)
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