mechanism of urine formation in mammalian nephrons

• Filtration


  Transfer of soluble components like water, glucose urea, salts, and waste from the blood that was filtered by the glomerulus
• Reabsorption


  Absorption of materials that the body still needs like molecules and ions, going back to the blood between the capillaries and the network of tubules by diffusion and active transport
• Secretion


  Transfer of removed substances like potassium ion, hydrogen ions, drugs, and toxins from the blood into the collecting duct and added to the filtrate
• Excretion


  Exit of urine into the ureter, urinary bladder, and urethra
• Antidiuretic hormone (ADH)


  Promotes water conservation, secreted from the hypothalamus through the pituitary when osmoreceptors detect an increase in the osmolarity of body fluids
• Acid-base balance


  Maintained by controlling hydrogen ions through buffer systems, respiration, and excretion by the kidneys, eliminating excess hydrogen ions and restoring bicarbonate buffering ions to the blood
• Plants do not have adaptive immune system and no immune system cells but have protein on their surface that recognizes different molecules from a variety of pathogens. The ability of plants to recognize and resist specific attackers is hard wired into genes.
• Types of immunity in animals

  • Natural or innate immunity
  • Adaptive or acquired immunity
• Natural or innate immunity


  • Non-specific, general immunity against a pathogen
  • Important barriers are the skin and mucous membranes
  • Lysozyme in tears, sweat and saliva degrades cell walls of bacteria and microorganisms
  • Innate immune response gives signals of real threat to be eliminated
  • Includes antimicrobial agents, phagocytic cells, natural killer cells, inflammation and fever
• Adaptive or acquired immunity


  • Recognition of traits specific to pathogens using a huge range of receptors
  • Second line of defense activated when pathogen is not destroyed by nonspecific defenses
  • Includes humoral response (antibody production) and cell-mediated response (cytotoxic cells)
• Antibody


  Protein molecule produced by lymphocytes, protects organisms by binding and eliminating foreign molecules by activating immune system mechanisms
• Antigen


  Substance or part of pathogen that stimulates production of a specific antibody
• B cells


  • White blood cells that develop and mature in the bone marrow, activated when they encounter antigen in the lymph nodes
  • Produce antibodies that recognize and bind to specific antigens
• Major Classifications of Antibodies

  • IgD
  • IgM
  • IgG
  • IgA
  • IgE
• T cells


  • White blood cells made in the bone marrow and mature in the thymus, activated when they meet antigens in the lymph nodes
  • Need to distinguish antigen in the context of self-molecules called major histocompatibility complex (MHC) molecules
  • Include cytotoxic T cells, helper T cells, and regulatory T cells
• Natural or innate immunity


  Non-specific, general immunity against a pathogen
• Skin


  First line of defense against infection
• Mucous


  Traps many of the microorganisms before they can able to penetrate the lungs
• Lysozyme


  Present in tears, sweat and saliva, degrades the cell wall of bacteria and other microorganisms
• Innate immune response


  Gives signals that there is real threat to the body that must be eliminated
• Internal defenses

  • Antimicrobial Agents
  • Phagocytic cells
  • Natural Killer cells
  • Inflammation and fever
• Antimicrobial Agents


  Includes Interferon, Interleukins Lactoferrin and transferrin and complement system
• Phagocytic cells


  • Engulf particles and microorganisms in the digestive vacuoles and then break down the cell by the lysozyme
• Types of phagocytic cells

  • Stationary phagocytes or macrophages
  • Wandering phagocytes
• Stationary phagocytes or macrophages


  Made in the bone marrow, monocytes circulate in the bloodstream and become macrophages when they stop circulating and become localized
• Wandering phagocytes


  White blood cells that circulate in the blood stream (neutrophils and monocytes)
• Natural Killer cells (NK)


  Not phagocytic, but they are attached to cell surface and produce enzymes that destroy cells that have infected with viruses
• Indications of inflammation

  • Fever
  • Swelling
  • Redness
  • Pain
  • Loss of function in the infected areas
• Fever


  High body temperature kills some bacterial pathogens and promotes phagocyte activity that speeds up an acquired immune response, it also reduces the concentration of iron in the blood which weakens and eventually kills microorganisms
• Inflammation and fever


  Non-specific antimicrobial response to infection and microorganisms
• The adaptive immune response is made possible because of:

  a.    Humoral response

  b.    Cell mediated response
• Humoral response is the production and secretion of antibodies against specific antigens (a protein, a foreign body like pollen, bacteria, dust, virus). 
• Cell mediated response occurs when cytotoxic cells defend the body against infection.   
• ·         IgD - Present on surface of many B cells, but function is uncertain. 

   
• • IgM - Found on surface of B cells and plasma. It acts as a B cell surface receptor for antigens secreted early in primary response.
• ·         IgG - Most abundant immunoglobulin in the blood plasma, approximately 75% of antibodies are in this class. 
• ·         IgA - Produced by plasma cells in the digestive, respiratory and urinary systems, where it protects the surface linings by preventing attachment of bacteria to surfaces of epithelial cells. 
• IgE - It activates mast cells and leads to the production of histamine responsible for allergic reactions, such as hay fever and asthma.
• T cells need to distinguish an antigen in the context of self-molecules called major histocompatibility complex (MHC) molecules. This is to assure that the immune system will only be activated when there is a real infection in the body.
• 1.    Cytotoxic T cells are effectors that kill infected cells, tumor cells, and foreign cells by a touch-kill mechanism.