Body Fluids

• The average adult body contains 42 L of fluids, which make up about 2/3 of the total body weight.
• located inside the cells (about 28 L, ~70%). This is the medium in which vital life-maintaining reactions occur


  Intracellular fluids
• located outside the cells. These fluids provide a constant environment for cells and transports substances to and from cells.

  Extracellular fluids
• fills the space between tissue cells and moves in lymph vessels (10.5 L, 20%)

  Interstitial fluids
• the liquid portion of the bloodstream (3.5 L, 7%)

  Plasma
• Other body fluids include urine, digestive juices, and cerebrospinal fluid.
• • The principal cation is potassium (K+ ). (98% of the body’s potassium is found inside cells).
  • The principal anion is phosphate (mainly HPO4 2- )
  • Has more than 4x as much protein as plasma


  Intracellular fluid
• • The principal cation is sodium (Na+ ).
  • The principal anion is chloride (Cl- ).
  • Interstitial fluid has very little protein; plasma contains an appreciable amount of protein.

  Extracellular fluid
• Blood is a body fluid that delivers substances such as nutrients and oxygen to the cells and transports metabolic waste products away from the cells
• Blood has an density of ~1.06 g/mL, and comprises 8% of the human body weight. The average adult has ~5 liters (1.3 gal) of blood
• Blood is circulated around the body through blood vessels by the pumping action of the heart
• Plasma constitutes 55% of blood fluid. It is mostly water (92%), along with proteins, CO2 , and other materials.
• Plasma circulates dissolved nutrients, such as glucose, amino acids, and fatty acids, and removes wastes, such as CO2 , urea, and lactate.
• The blood cells (45% of blood fluid) are RBC, WBC, and Platelets
• Red Blood Cells (erythrocytes) contain hemoglobin, which facilitates O2 transport by reversibly binding O2 and increasing its solubility in blood. They contain no cell nucleus or other organelles
• White Blood Cells (leukocytes) are involved in the body’s immune responses to infections and foreign materials, and remove discarded cells and debris
• Platelets (thrombocytes) are responsible for blood clotting (coagulation)
• Blood supplies oxygen to tissues
• Blood supplies nutrients
• Blood removes wastes such as CO2, urea, and lactic acid
• Blood's immunological functions, including circulation of white blood cells, and detection of foreign material by antibodies
• Blood is for Coagulation (blood clotting after an open wound in order to stop bleeding)
• Blood is for messenger functions, including the transport of hormones and the signaling of tissue damage
• Blood regulates body pH
• Blood regulates core body temperature
• Blood is also for hydraulic functions
• Small polysaccharide chains covalently bound by glycosidic links to –OH or – NH2 groups on proteins act as biochemical markers on cell surfaces
• If human blood from one donor type (A, B, AB, or O) is transfused into a recipient with another blood type the red blood cells clump together, or agglutinate
• Agglutination results from the presence of polysaccharide markers on the surface of the cells
• a combination of oxygen and hemoglobin

  Oxyhemoglobin
• the non-oxygenated form (often simply referred to as hemoglobin)

  Deoxyhemoglobin
• Hemoglobin is a conjugated protein containing four protein chains (the globin portion of the molecule) and four heme groups
• The heme group consists of a flat porphyrin-ring with four nitrogen atoms pointing in towards a central cavity, which bind an Fe2+ ion.
• The iron atom is also bound to a histidine group in the protein
• The sixth bond to the Fe2+ ion is to an O2 molecule.
• Because there are four heme groups in a hemoglobin molecule, one hemoglobin can bind a total of four O2 molecules
• When one of the four heme groups binds an O2 , the affinity of the other heme groups for O2 is increased.
• When an O2 binds to the Fe2+ the histidine residue is pulled towards the heme group.
• When CO2 is present, hemoglobin can combine with it to form carbaminohemoglobin.
• The walls of the capillaries act as selectively permeable membranes