Epithelium

• Absorption is the process of transport from an organ or duct's lumen to capillaries near the epithelial basement membrane
• Absorption involves movement from the apical to the basolateral cell membrane
• Example of absorption

  In epithelium of intestine where it obtains water and ions from digested material
• Secretion involves the transport in the other direction from the capillaries into a lumen
• Secretion removes water from the neighboring interstitial fluid or plasma and releases it as a part of the specialized aqueous fluids in organs
• Epithelia are capable of rapid repair and replacement of apoptotic or damaged cells
• Large glands (ex. liver) mitotic activity is normally rare but is actively renewed following major damage
• When a portion of liver tissues is removed surgically or lost due to a toxic substance, undamaged cells start active proliferation to regenerate liver tissue with normal function
• Carcinoma is a malignant neoplasm of epithelial cells, a "new growth" of the body's own cells, a proliferation of cells no longer under normal physiologic control
• Benign and malignant tumor can come from most types of epithelial cells
• Adenocarcinoma is a malignant tumor that comes from glandular epithelial tissue (Ex. mucus membrane). These are the most common tumors in adults after age 45
• Most carcinomas affect organs or glands campable of secretion (Ex. breasts, lungs, colon, prostrate or bladder)
• Squamous cell carcinoma (ex. cervix, head and neck, vagina) happens in tissues with flat cells that form the surface of the skin, lining of the hollow organs of the body, and the lining of the respiratory and digestive tracts.