Lecture 3 Body Fluids PDF

Faculty of health sciences technology Lecture 3 Body fluids Dr. Nadia elyas BODY FLUIDS AND CELL MEMBRANE LECTURE 3 Dr. Nadia Fouad BODY FLUIDS:  About 60 percent of the adult human body is fluid, mainly a water solution of ions and other substances.  Although m...

Faculty of health sciences technology Lecture 3 Body fluids Dr. Nadia elyas BODY FLUIDS AND CELL MEMBRANE LECTURE 3 Dr. Nadia Fouad BODY FLUIDS:  About 60 percent of the adult human body is fluid, mainly a water solution of ions and other substances.  Although most of this fluid is inside the cells and is called (intracellular fluid).  about one third is in the spaces outside the cells and is called (extracellular fluid).  This extracellular fluid is in constant motion throughout the body.  It is transported rapidly in the circulating blood and then mixed between the blood and the tissue fluids by diffusion through the capillary walls. BODY FLUIDS BALANCE DISORDERS  Every part of your body needs water to function. When you are healthy, your body is able to balance the amount of water that enters or leaves your body. A fluid imbalance may occur when you lose more water or fluid than your body can take in. It can also occur when you take in more water or fluid than your body is able to get rid of. Causes:  Your body is constantly losing water through breathing, sweating, and urinating.  If you do not take in enough fluids or water, you become dehydrated.  Your body may also have a hard time getting rid of fluids. As a result, excess fluid builds up in the body. This is called fluid overload (volume overload). This can lead to edema (excess fluid in the skin and tissues).  Many medical problems can cause fluid imbalance: After surgery, the body usually retains large amounts of fluid for several days, causing swelling of the body. CAUSES:  In heart failure, fluid collects in the lungs, liver, blood vessels, and body tissues because the heart does a poor job of pumping it to the kidneys.  When the kidneys do not work well because of chronic kidney disease, the body cannot get rid of unneeded fluids.  The body may lose too much fluid due to diarrhea, vomiting, or high fever.  Lack of a hormone called antidiuretic hormone (ADH) can cause the kidneys to get rid of too much fluid. This results in extreme thirst and dehydration.  Medicines can also affect fluid balance. Membranous Structures of the Cell:  Most organelles of the cell are covered by membranes  composed primarily of lipids and proteins. These membranes  include the cell membrane, nuclear membrane, membrane of the endoplasmic reticulum, and membranes of the mitochondria, lysosomes, and Golgi apparatus. 1) The lipids of the membranes provide a barrier that impedes the movement of water and water-soluble substances from one cell compartment to another because water is not soluble in lipids. 2) protein molecules in the membrane often do penetrate all the way through the membrane, thus providing specialized pathways, often organized into actual pores, for passage of specific substances through the membrane. 3) Also, many other membrane proteins are enzymes that catalyze a multitude of different chemical reactions. Functions of Lipid Layer in Cell Membrane:  Lipid layer of the cell membrane is a semipermeable membrane and allows only the fat-soluble substances to pass through it.  Diffusion involves simple movement through the membrane caused by the random motion of the molecules of the substance.  Active transport involves the actual carrying of a substance through the membrane by a physical protein structure that penetrates all the way through the membrane.  These active transport mechanisms are so important to cell function Endocytosis:  Very large particles enter the cell by a specialized function of the cell membrane called endocytosis.  The principal forms of endocytosis are pinocytosis and phagocytosis. (1) Pinocytosis means ingestion of minute particles that form vesicles of extracellular fluid and particulate constituents inside the cell cytoplasm. (2) Phagocytosis means ingestion of large particles, such as bacteria or whole cells.  RECOMMENDED TEXT BOOKS  BruceKoeppen Bruce Stanton, Berne & Levy Physiology, 7th Edition, 29th March 2017.