Epithelium Research Paper

EPITHELIUM

It is a tightly adhesive sheet of cells covering the body surface or lining a body cavity. It also constitutes many of the body’s glands. Epithelium can be simple, having one cell layer, or stratified, having multiple cell layers. Epithelial cells can be squamous or cuboidal or columnar based on their shape and each cell has apical surface and basal surface. Depending on its location in the body, simple epithelial cells can have different types of apical surface modifications like cilia, stereo cilia and, microvilli; another special feature seen in simple columnar epithelium is presence of goblet cells.

1. Simple squamous epithelium

Made of flat cells with disc-shaped central nuclei, it makes up the endothelial lining of all blood

In kidneys, it lines some convoluted tubules. Surface proteins on cuboidal cells helps facilitate absorption and transportation of materials filtered by kidneys. In proximal convoluted tubules, apical surface of epithelium has microvilli which aids in transportation of substances by brushing them in one direction in the lumen. Ovarian surface is also lined by this epithelium; since cuboidal epithelial cells tend to divide rapidly and grow, any defects in ovulation occurring on this surface are repaired. Simple cuboidal epithelium also lines respiratory bronchiole walls and may be ciliated in some portions, creating a transitional zone for both air conduction and gas

There are three types of cartilage:

 Hyaline cartilage: Firm, viscous matrix containing chondrocytes and collagen fibers. It is flexible and resists compressive stress, and forms embryonic skeleton. It’s present in joints, between bones, in nose, trachea and larynx due to its supporting and cushioning properties.

 Fibrocartilage: It’s similar to hyaline cartilage but less firm because of more collagen fibers. It’s found between intervertebral discs, pubic symphysis, and knee joint as it can resist pressure and compression.

 Elastic cartilage: Also similar to hyaline cartilage, but has more elastic fibers in matrix. It can maintain shape of a structure but is also bendable; it’s found in outer ear, larynx and epiglottis.

MUSCLE TISSUE

It helps to produce movements, generate heat, move substances, and maintain posture. It can be of three types:

1. Skeletal muscle tissue: It has striations, multinucleate cells and under voluntary control; found near bones and help in body movement due to muscle contraction facilitated by sliding filament