1. THE EPITHELIAL CELL By
Billy Rodriguez

3. Organelles of an Epithelial Cell

4. Organelle Functions
Nucleus: The nucleus is the main control center of the cell. It produces mRNA in order for protein synthesis to take place. It contains genetic information for the cell in the form of DNA and chromosomes. It aslo assembles ribosomes.
Mitochondria: Mitochondria produce ATP from respiration. The amount of mitochondria present depends on the metabolic activity level.
Smooth E.R: It synthesizes, stores, and then transports carbohydrates and lipids.
Rough E.R: It provides a pathway for the transportation of materials throughout the cell. In addition, it provides a large surface area for protein synthesis and glycoproteins. It also contains ribosomes.
Golgi apparatus: The golgi apparatus stores and modifies proteins by adding carbohydrates and forming glycoproteins. It also produces secretory enzymes, lysosomes, and secrets carbohydrates.
Ribosomes: These organelles are protein macromolecules. They assist in protein synthesis, where they pair each codon of the mRNA strand with the appropriate amino acid.
Lysosomes: They release enzymes to destroy material outside the cell, break down material ingested by phagocytes in phagocytosis, and digest/remove used up organelles so chemical can be reused. They also break down cells after they have died (autolysis).

5. Main Structure and Function
Epithelium cells are densely packed and leave little intracellular space.
These cells form continuous sheets that are attached to each other by specific junctions called tight junctions, adherens junctions, and desmosomes.
The epithelial cells rest on a basement membrane that’s is selectively permeable, meaning it determines which substances may and may not enter the epithelium.
The main functions of epithelial cells are to protect their surroundings from radiation, toxins, invasion by pathogens, etc. It is also to regulate and exchange chemicals between underlying tissues and a body cavity. Another main function is the secretion of hormones into the blood vascular system, and the secretion of products that are delivered to the cells by ducts glandular epithelium. The last main function is to provide sensation.