Human Anatomy and Physiology I

• Immunology was discovered first in 430 BC in Athens, where plague survivors were thought to be immune from a second attack by a disease agent
• When defences are overcome due to injury or contamination, the immune response shifts to red alert, starting with an acute inflammatory response at the site of infection
• We fight invaders effectively through antibodies circulating in our bloodstream and immune cells in areas rich in white cells such as the bone marrow, thymus, spleen, and lymph nodes
• Effective physical defence barriers include skin, nasal and gut secretions, and cilia lining the trachea
• The biggest threat to our health without an immune system would be microbes including bacteria, fungi, viruses, and parasites
• Most infectious agents are prevented from entering the body by biochemical and physical barriers such as skin, mucous membranes, and their secretions
• Biochemical and physical barriers

  • Skin
  • Mucous membranes
  • Secretions
• Cells of the Immune System

  • Consist of white cells (leukocytes) and specialised areas called lymphoid tissues (lymph nodes)
  • Lymphocytes circulate within both the lymph vessels and the blood vessels and are part of the adaptive immune response
  • Granulocytes, macrophages, and neutrophils are cells of the innate immune system
• Myeloid cells responsible for the innate immunity in the body (2)

  1. Neutrophils are the most abundant white cell in the blood and are phagocytic

  2. Eosinophils are involved in causing damage to parasitic worms and have a role in asthma during an allergic response
• Natural killer cells (NK cells)

  1. Can kill intracellular infections by bacteria and viruses by destroying the infected cell

  2. Can target and kill tumour cells in the body
• The body tolerates a number of commensal organisms which compete effectively with many potential pathogens
• A variety of biochemical and physical barriers prevent infectious agents from entering the body
• The production of all cell types found in the immune system starts from a self-renewing bone marrow stem cell
• T and B lymphocytes (lymphoid lineage)

  T and B cells are part of the adaptive immune system
• Myeloid cells responsible for the innate immunity in the body (3)

  1. Basophils help produce an inflammatory response within the surrounding tissues during an allergic reaction or attack by parasites

  2. Mast cells can release granules during an inflammatory or allergic response that contain histamine and other active agents
• Myeloid cells responsible for the innate immunity in the body (1)

  1. Macrophages are important phagocytic cells and present antigens to T cells of the adaptive immune response

  2. Dendritic cells are the most important antigen-presenting cells of the body and can activate resting T cells
• The yellow areas in this diagram show the areas that either produce the white cells (bone marrow) or help in their development (thymus). The spleen and lymph nodes are shown in blue. The Peyer’s patches in the small intestine are clusters of immune cells which detect pathogens in the gut
• Comparison of the innate and adaptive immune systems

  • Major elements: Soluble factors - Lysozyme, complement, interferon
  • Cells - phagocytes, natural killer cells
  • Response to microbial infection: First contact - +, Second contact - +, Non-specific response - No memory of previous encounter, Resistance not improved by repeated contact
  • Major elements: Antibody, cytokines
  • Cells - T lymphocytes, B lymphocytes
  • Response to microbial infection: First contact - ++, Second contact - ++++, Specific response - Memory of a previous encounter, Resistance improved by repeated contact
• Humans are very polymorphic in their MHC molecules expressed on all body cells of the body (except erythrocytes). Of all human genes sequenced, the MHC is the most polymorphic of all. A total of 35 million phenotype permutations are possible which is good for fighting infections. However, this makes tissue typing donor and recipient before a kidney transplant in the hope of a 100 % match almost impossible to achieve!
• Mate selection and MHC in mice. Genetic information about MHC status is relayed by androgen-based pheromones in mammals. Numerous studies in rodents have now established that MHC genotype is involved in odour production, and such odours are used in individual discrimination. House mice learn the MHC identity of their family during development and avoid mating with individuals carrying familial MHC genes; they do so through the use of odour cues from urine. This is great for maintaining MHC diversity!
• The primary lymphoid organs: (a) the spleen
• Innate and adaptive (aka acquired) immunity must work together to destroy microorganisms
• The first heart transplant takes place

  December 3rd, 1967
• Circulating lymphocytes meet antigen in lymph nodes local to the infected site. Lymphocytes that have never seen antigen (naïve lymphocytes) recirculate constantly between the lymph nodes of the body. If they encounter a pathogen within the draining lymph node they become activated and return to the bloodstream to find the infected tissue to destroy the infectious agent. This whole process takes 4-6 days! Luckily the innate immune response is already tackling the infection from day 1
• Cytokines

  Local factors produced by cells
• Local cytokines

  Affect local blood vessels by making them "leak," allowing cells and fluid to move into the area
• The inside of a resting cell membrane is negatively charged
• The equilibrium potential at 37°C for Na+ is -58 mV
• Permeability is a property of membranes
• The protein whose production is affected in the disease Duchenne muscular dystrophy is dystrophin
• The simplest cell-cell junction is called a gap junction
• The correct labelling sequence for the missing labels in the schematic of a typical neuron is 1) Axon Hillock, 2) Dendrites, 3) Axon, 4) Myelin Sheath, 5) Synapse
• One function of epithelia is NOT storing energy reserves
• The two types of glial cell which form myelin are Schwann cells and oligodendrocytes
• What happens to the membrane potential of a cell that suddenly becomes more permeable to Na+?

  It becomes more positive
• Which statement about the NA+/K+ is FALSE?

  It transports NA+ and K+ in a 1:1 ratio.
• The afferent and efferent neurons together form the peripheral nervous system.
• CF is an inherited disease. How is CF passed down through the families?


  Both parents are carriers of the CF gene
• Which of the following is not a type of cell junction?

  Loose junctions
• Which statement about the resting membrane potential is TRUE?

  It results, in part, from the concentration gradients for Na+ and K+