Cell Modification PDF

A. Apical Modification A. Apical Modification 1. Cilia– Cilia are projections, usually short, hairlike structures and a type of organelle seen on the apical surface of epithelial cells. This assists in the movement of material over the epithelial surface in a manner parallel with the surface of t...

A. Apical Modification A. Apical Modification 1. Cilia– Cilia are projections, usually short, hairlike structures and a type of organelle seen on the apical surface of epithelial cells. This assists in the movement of material over the epithelial surface in a manner parallel with the surface of the epithelium. The figure shows an epithelial tissue of the trachea with prominent cilia on the apical surface. A. Apical Modification 2. Flagella –Flagella are long, whip-like structure that are formed by microtubules protruding from the cell body of bacteria and some eukaryotic cells. The primary function of a flagellum is that of locomotion example is for sperm cell A. Apical Modification Villi and microvilli – Villi are finger-like projections that arise from the epithelial layer in some organs. They help to increase surface area, allowing faster and more efficient absorption. Microvilli are smaller projections than villi which functions primarily on the efficient absorption of molecules. A. Apical Modification The figure shows microvilli that are present on the apical aspect of the columnar epithelium of the duodenum. Pseudopods – Temporary, irregular lobes formed by amoebas and some other eukaryotic cells. It bulges outward to move the cell or engulf the prey. It primarily consist of actin filaments and may also contain microtubules and intermediate filaments. Pseudopods are used for motility and ingestion. Extra Cellular Matrix (ECM) – A compound secreted by the cell on its apical surface. The cell wall is the extracellular structure in plant cells that distinguishes them from animal cells. The plant cell wall is made up of molecules secreted by the cell called cellulose, a polysaccharide compose of glucose units. Cellulose assembles into fibers called microfibrils as shown in the diagram Extra Cellular Matrix (ECM) – A compound secreted by the cell on its apical surface. The extracellular matrix helps cells attach to, and communicate with, nearby cells, and plays an important role in cell growth, cell movement, and other cell functions. B. Basal Modification - Cell modification found on the basal surface of the cell basement membrane. B. Basal Modification Hemidesmosomes – attach the epithelial cell to the basement membrane. C. Lateral Modification -Cell modification found on the lateral surface (side) of the cell. These are tight junctions, adhering junctions and gap junctions. These structures consist of protein complexes and induce connectivity between adjacent epithelial cells, between cell and ECM. They can contribute to the barrier function of epithelia and control the paracellular transport. C. Lateral Modification 1. Gap Junction gap junctions are channels between neighboring cells that allow for the transport of ions, water, and other substances C. Lateral Modification 2. Tight Junction Not all junctions between cells produce cytoplasmic connections. Instead, tight junctions create a watertight seal between two adjacent animal cells. The purpose of tight junctions is to keep liquid from escaping between cells, allowing a layer of cells (for instance, those lining an organ) to act as an impermeable barrier. For example, the tight junctions between the epithelial cells lining your bladder prevent urine from leaking out into the extracellular space. C. Lateral Modification 3. Adherens/ adhering Junction Adhering junctions provide cementing to keep neighbouring cells together.