Ch 6

• • The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and moves it along the gut.
• • The pancreas secretes enzymes into the lumen of the small intestine
• • Enzymes digest most macromolecules in food into monomers in the small intestine.
• • Villi increase the surface area of epithelium over which absorption is carried out.
• • Villi absorb monomers formed by digestion as well as mineral ions and vitamins.
• • Different methods of membrane transport are required to absorb different nutrients.
• • Application: Use of dialysis tubing to model absorption of digested food in the intestine.
• • Skill: Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph.
• • Students should know that amylase, lipase and an endopeptidase are secreted by the pancreas.
• • Tissue layers should include longitudinal and circular muscles, mucosa and epithelium.
• • Arteries convey blood at high pressure from the ventricles to the tissues of the body.
• • Arteries have muscle cells and elastic fibres in their walls
• • The muscle and elastic fibres assist in maintaining blood pressure between pump cycles.
• • Blood flows through tissues in capillaries. Capillaries have permeable walls that allow exchange of materials between cells in the tissue and the blood in the capillary.
• • Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart.
• • Valves in veins and the heart ensure circulation of blood by preventing backflow.
• • There is a separate circulation for the lungs
• • The heart beat is initiated by a group of specialized muscle cells in the right atrium called the sinoatrial node.
• • The sinoatrial node acts as a pacemaker.
• • The sinoatrial node sends out an electrical signal that stimulates contraction as it is propagated through the walls of the atria and then the walls of theventricles.
• • The heart rate can be increased or decreased by impulses brought to the heart through two nerves from the medulla of the brain.
• • Epinephrine increases the heart rate to prepare for vigorous physical activity.
• • Application: William Harvey’s discovery of the circulation of the blood with the heart acting as the pump.
• • Application: Pressure changes in the left atrium, left ventricle and aorta during the cardiac cycle.
• • Application: Causes and consequences of occlusion of the coronary arteries.
• • Skill: Identification of blood vessels as arteries, capillaries or veins from the structure of their walls.
• • Skill: Recognition of the chambers and valves of the heart and the blood vessels connected to it in dissected hearts or in diagrams of heart structure.
• • The skin and mucous membranes form a primary defence against pathogens that cause infectious disease.
• • Cuts in the skin are sealed by blood clotting
• • Clotting factors are released from platelets
• • The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin
• • Ingestion of pathogens by phagocytic white blood cells gives non-specific immunity to diseases.
• • Production of antibodies by lymphocytes in response to particular pathogens gives specific immunity.
• • Antibiotics block processes that occur in prokaryotic cells but not in eukaryotic cells.
• • Viruses lack a metabolism and cannot therefore be treated with antibiotics. Some strains of bacteria have evolved with genes that confer resistance to antibiotics and some strains of bacteria have multiple resistance.
• • Application: Causes and consequences of blood clot formation in coronary arteries.
• • Application: Florey and Chain’s experiments to test penicillin on bacterial infections in mice.
• • Application: Effects of HIV on the immune system and methods oftransmission.
• • students should be aware that some lymphocytes act as memory cells and can quickly reproduce to form a clone of plasma cells if a pathogen carrying a specific antigen is re-encountered.
• • The effects of HIV on the immune system should be limited to a reduction in the number of active lymphocytes and a loss of the ability to produce antibodies, leading to the development of AIDS