IB Biology Topic 6_ Human Physiology.pdf - Topic 6 Human Physiology The Human Digestive System The Small Intestine ● ● ● ● ● Waves of muscle

IB Biology Topic 6_ Human Physiology.pdf - Topic 6 Human...

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Topic 6: Human Physiology The Human Digestive System The Small Intestine Waves of muscle contractions called peristalsis pass along the intestine Contraction of circular muscle behind the food constricts the gut to prevent food from being pushed back to the mouth Enzymes digest most macromolecules in food into monomers in the small intestine (protein, starch, glycogen, lipids, nucleic acids) Cellulose remains undigested The pancreas secretes three types of enzymes into the small intestine Lipids (fats and oils) are digested by lipase into fatty acids and glycerol Polypeptides are digested by endopeptidase into shorter peptides Starch is digested by amylase into maltose Intestinal Villi Absorption - process of taking substances into cells and the blood In human digestive systems, nutrients are absorbed by the epithelium in the small intestine Absorption occurs in the small intestine Surface area of epithelium is increased by villi, which are small finger-like projections of the mucosa on the inside of the small intestine wall Villi absorbs mineral ions and vitamins and also monomers Methods of Absorption Simple diffusion - nutrients pass down the concentration gradient between phospholipids in the membrane Facilitated diffusion - nutrients pass down the concentration gradient through specific channel proteins in the membrane Active transport - nutrients are pumped through the membrane against the concentration gradient by pump proteins Endocytosis - small droplets of fluid are passed through the membrane by means of vesicles Modelling Absorption with Dialysis Tubing E.g. Cola drink is placed in dialysis tubing, and water outside is to be tested to see if substances in the cola have diffused through the dialysis tubing Expected results were that glucose and phosphoric acids will diffuse through the tubing but polymers of sugar will not
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The Cardiovascular System Harvey and the Circulation of Blood William Harvey is credited with the discovery of the circulation of blood He showed that the heart pumps blood out in the arteries and that it returns in veins The Double Circulation Pulmonary circulation - for the lungs Systemic circulation - for other organs in the body Heart is a double pump with left and right sides Right side pumps deoxygenated blood to the lungs via pulmonary artery Left side pumps oxygenated blood to all organs of the body aside from lungs via the aorta Deoxygenated blood is carried back to the right side of the heart in the vena cava Structure and Function of Blood Vessels Arteries - blood pumped out at a high pressure by the ventricles of the heart, carry blood tissue to the body Capillaries - carry blood through tissues, they have permeable walls that allow exchange of materials between the cells of 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
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