[BIO] Chapter 7 - Transport in Humans

© Hee Xin Wei (Copyrighted) Topic 7: Transport in Humans

Chapter Analysis FOCUS EXAM WEIGHTAGE •commonly tested in both MCQ and structured •tested every year in the past 5 years •Constitute to around 9% in Paper 2 in the past 5 years •Heavy content •Knowledge on circulation system is linked to other chapters

Components of blood Blood group Key Concept

components and roles of blood (1) role of blood in transport Cells 45% Plasma 55% 1.90% water: essential in transporting blood cells and dissolved substances 2.10% a mixture of dissolved substances: •Soluble plasma proteins such as fibrinogen, prothrombin and antibodies. Fibrinogen and prothrombin play an important part in the clotting of blood. These proteins are made in the lever. Antibodies help to fight diseases. •Dissolved mineral salts, for example, hydrogencarbonates, chlorides, sulfates and phosphates of calcium, sodium and potassium. All these occur as ions in the plasma. Calcium is essential for blood clotting. •Food substances, for example, glucose, amino acids, fats and vitamins. •Excretory products, for example, urea, uric acid and creatinine. Carbon dioxide is present as hydrogencarbonate ions. •Hormones, for example, insulin. •Vitamins •red blood cells •white blood cells •platelets

red blood cells 1.The oxygen diffuse from the lung into the blood and bind reversibly with haemoglobin in red blood cells to form oxyhaemoglobin. 2.When blood is transported to oxygen-poor respiring tissues, oxyhaemoglobin releases its oxygen which then diffuses into tissue cells. (more will be discussed in the respiration chapter) Adaptation of RBC to its function: •Contains haemoglobin, an iron-containing protein which is able to bind reversibly with oxygen, which enables red blood cells to transport oxygen from the lungs to other body parts •Mature red blood cells do not possess a nucleus, enabling it to carry more haemoglobin and thus more oxygen. •Flattened, biconcave shape which increasing the surface area to volume ratio for faster diffusion of oxygen •Flexibility to turn bell-shaped in order to pass through the narrow lumen of the capillaries (2) role of blood in transporting oxygen

white blood cells IMMUNE FUNCTIONS (i)Phagocytes have lobed nuclei and granular cytoplasm. They engulf and digest foreign particles such as bacteria (phagocytosis) (ii)Lymphocytes have a large rounded nucleus and a small amount of cytoplasm. They produce antibodies to protect the body from pathogens. TISSUE REJECTIONS 1.Tissue rejection occurs when the transplanted tissue is not accepted by the body of the transplant recipient. 2.This because the tissues of the transplanted organ are treated as foreign bodies by the recipient’s immune system and are attacked by phagocytes. 3.Prevention of tissue rejection: (a)Required tissue can be transplanted from genetically-similar donors (family members) (b)Tissue can be transplanted from one part of the body to another, e.g. skin grafting, as the tissue will be recognised as the recipient’s own tissue. (c)Immunosuppressive drugs can be taken to suppress the immune system of the recipient. •However, this means that patients will suffer from lowered resistance to infection and they have to continue taking the drugs for their entire lifespan (3) role of blood in immune function and (4) tissue rejection

platelets •Blood platelets or thrombocytes are not true cells. They have no nucleus and they are membrane-bound cell fragments •They play a part in the blood clotting 1.Where there is an injury such as a cut, blood vessels are damaged and platelets are activated, releasing clotting factors like thrombokinase. 2.Thrombokinase converts plasma protein, prothrombin, into thrombin in the presence of calcium and vitamin K. 3.Thrombin converts soluble fibrinogen to insoluble fibrin 4.Fibrin forms a mesh across the damaged surface and traps red blood cells, forming a clot. 5.The clot prevents further blood loss, and also restricts the entry of pathogens into the blood. (5) role of blood in blood clotting

ABO blood groups Blood Group Antigen on red blood cells Antibody in blood plasma A Antigen A Antibody B B Antigen B Antibody A O No antigen Antibody A and Antibody B AB Antigen A & Antigen B No antibodies Donor Receipient A B O AB A ✓ ✘ ✘ ✓ B ✘ ✓ ✘ ✓ O ✓ ✓ ✓ ✓ AB ✘ ✘ ✘ ✓ ✓ - blood transfusion is accepted ✘ - blood transfusion is rejected •Blood group O is known as the universal donor as there are no antigens on the donor’s red blood cells and thus will not react with the recipient’s antibodies thus no agglutination will occur •Blood group AB is known as the universal acceptor as there are no antibodies in the plasma of the recipient, thus will not react with donor’s red blood cells antigens thus no agglutination will occur •Blood group classification is based on the antigens present on the cell surface membrane of red blood cells •Blood plasma contains antibodies which can recognise the antigens as either foreign or self •An immune response will occur where antibodies in the blood plasma of recipient would react with the antigens of red blood cells of donor, causing agglutination or clumping of red blood cells •The clumps may block up small blood vessels and prevent the flow of blood, which is very dangerous.

artery, veins, capillaries tissue fluid Key Concept

Blood Capillaries artery and veins Artery Vein Connective tissue Lumen Lumen endothelium smooth muscles and elastic fibres endothelium ARTERY Function: •Arteries are blood vessels which carry blood away from the heart, thus need to withstand the high pressure of blood pumped out of the heart. •All arteries carry oxygenated blood with the exception of the pulmonary arteries. Structure and adaptations: •Thick, muscular and elastic walls •Thick walls allow arteries to withstand immense pressure of blood that was just pumped out of the heart •Elasticity of wall allows arteries to stretch and recoil under high pressure and push blood along arteries VEINS Function: •Veins transport blood back to the heart •All veins carry deoxygenated blood with the exception of the pulmonary veins. Structure and adaptations: •Middle wall contains much less smooth muscle and elastic fibres. Hence they are not as thick, muscular or elastic as arteries as the blood pressure is lower •Large lumen offer low resistance to blood flow, blood can flow smoothly back to the heart •Semi lunar vales are present which will close to prevent backflow of blood to ensure flow of blood in one direction.