Form 5 Biology (chapter 1: Transport) 1b5s

Biology Form 5: Chapter 1

1.2 The Circulatoy System 1. Components: a) Blood b) Heart c) Blood vessels

Blood and haemolymph 1. Blood is the medium of transport in animals and humans. 2. Haemolymph is a blood-like nutritive fluid found in insects. The functions of blood 1. Tranports oxygen from the lungs to the cells throughout the body. 2. Tranports carbon dioxide from the cells to the lungs. 3. Tranports nutrients, hormones and waste products. 4. Regulate the pH of body fluid. 5. Regulate body temperature. 6. Regulate water content. 7. Blood clotting. 8. Protects the body against diseases. The functions of haemolymph 1. Transports water, inorganic salts and organic compounds. The composition of human blood 1. Made up of 55% plasma and 45% cellular components. 2. Plasma is the main transport medium in the body. 3. Cellular components of blood: a) red blood cells (erythrocytes) b) platelets c) white blood cells (leucocytes).

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Biology Form 5: Chapter 1

Erythrocytes (RBC)

1. Biconcave disc shaped provides large surface area/volume ratio for gaseous exchange. 2. Matured cells do not have nucleus. 3. Contains haemoglobin. 4. Haemoglobin is an oxygen carrying protein pigment which gives the RBC the colour red. 5. Hb contains haem groups which contains iron. It is the site of oxygen binding. 6. Each haemoglobin molecules can bind up to four oxygen molecules. 6. Lifespan of erythrocyte is 120 days. 7. Destroyed in the liver and spleen. 8. Manufactured in the bone marrow.

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Biology Form 5: Chapter 1

Leucocytes (WBC) 1. Colourless and have a nucleus. 2. Larger than RBC. 3. Made from stem cells in bone marrow.

Neutrophil

Basophil

Eosinophil

Monocyte

Lymphocyte

4. Leucocytes can fight infectious diseases in the interstitial fluid. 5. Neutrophils and monocytes are phagocytes. 6. Eosinophils and basophils release enzymes that combat inflammation in allergic reactions and kill parasitic worms. 7. Lymphocytes produce immune response against foreign substances. Platelets

1. Cell fragments from the bone marrow. 2. No nucleus. 3. Involved in blood clotting.

Human blood vessels Arteries 1. Blood vessels that carry blood away from the heart. 2. Transport blood quickly at high pressure (due to heart’s pumping action). 3. To withstand such a high pressure, the walls of the aorta must be thick. 4. The muscle tissue enables the artery to constrict and dilate. 5. Aorta is the main artery. 6. The blood pressure in the human aorta is about 120 mm Hg. 7. Arteries branch into smaller vessels called arterioles.

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Biology Form 5: Chapter 1

Capillaries 1. Thin walled vessels (one cell thick). 2. Allow rapid gaseous exchange between the blood and cells via diffusion. Veins 1. Brings back blood to the heart. 2. Smooth muscle layer in veins are thinner than that in arteries. 3. Large lumens and valves that maintain the one-way flow of blood.

The human heart The structure and function of the human heart. 1. Heart is situated between the two lungs in the thoracic cavity. 2. Pumps blood. 3. Four chambers; a) two upper chambers (atria) – receive blood returning to the heart b) two lower chambers (ventricle) – pump blood out of the heart 4. The muscular wall of the left ventricle is thicker than the right because the left ventricle needs to pump blood to all the parts of the body. 5. Valves are present to allow blood to flow in only one direction. 6. Bicuspid and tricuspid valve prevent blood from flowing back into the atria. 7. Semi lunar valves prevent blood from flowing back into the ventricles when the ventricle relax. 8. Oxygenated blood from the lungs enters the left atrium via the pulmonary veins. 9. Deoxygenated blood from the rest of the body enters the right atrium via the vena cava.

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Biology Form 5: Chapter 1

10. As blood fills the atria, the atria contract and push the blood into the two ventricles. 11. When the ventricles begin to contract, the bicuspid and tricuspid valves are closed, and blood is pushed out through the semi-lunar valves into the pulmonary arteries and the aorta. 12. Deoxygenated blood is pumped to the lungs through the pulmonary arteries while oxygenated blood is pumped through the aorta to the rest of the body. 13. The first sound lub is caused by the closing of the bicuspid and tricuspid valves. 14. The second sound dub is caused by the closing of the semi-lunar valves.

The circulation of blood in humans The pumping of the heart 1. The heart is made up strong cardiac muscle. 2. Cardiac muscle is myogenic (contract and relax without the need to receive impulses from the nervous system). 3. The cardiac muscles are interconnected enabling electrical signals to be conducted rapidly through the heart, and at the same time stimulate the cardiac muscle to contract in a coordinated way.

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Biology Form 5: Chapter 1

Bundle of His fibres

Bundle branches Purkinje fibres

4. The coordination of the heart is initiated and coordinated by a pacemaker (cluster of cells that sets the rate at which the heart contracts). 5. Pacemaker: a) located at the wall of the right atrium. b) generates electrical impulses. c) made of sinoatrial node (SA) node and atrioventricular (AV) node d) regulated by parasympathetic (slows down) and sympathetic (speeds up) nerves. e) controlled by adrenaline or epinephrine (increases heartbeat rate during moments of fear or threat).

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Biology Form 5: Chapter 1

6. SA node generates electrical impulses which spread rapidly over the walls of both atria, causing both atria to contract. 7. From the SA node, the impulses reach the AV node. 8. From the AV node, specialized muscle fibres (bundle of His, bundle branches and Purkinje) conduct the signals to the apex of the heart and throughout the walls of the ventricles. 9. This causes the ventricles to contract and push blood out to the lungs and body. Contraction of skeletal muscle around veins

1. When skeletal muscle contract, they squeeze the veins and push blood through the veins. 2. The veins have one-way valves that allow blood to flow only towards the heart.

How blood pressure is regulated 1. Blood pressure: a) Pressure exerted on the wall of the blood vessel. b) Force that drives blood through the arteries and capillaries. c) Highest in aorta and large arteries during systole (the contraction of ventricles when blood is pumped out of the aorta and pulmonary artery). d) 120 (systolic) /80 (diastolic)mmHg e) Regulated by negative mechanisms. 2. Baroreceptor (arch of aorta) and carotid arteries in the neck detect blood pressure and send impulses to the medulla oblongata (cardiovascular centre). Blood pressure Increase Decrease Impulse Sent at faster rate Sent at a slower rate Cardiac muscle Weaker Stronger contraction Smooth muscle of artery Relax Contract Resistance of blood flow Decrease Increase Blood vessels Widen (Vasodilation) Narrow (Vasoconstriction) 7

Biology Form 5: Chapter 1

3. This brings the bp to normal value.

The circulatory system in humans, fish and amphibians 1. Flatworm does not need a circulatory system because oxygen and digested materials can diffuse directly to all its body cells.

Circulatory system Heart Circulatory system

Insects Open

Human

Fish

Amphibians Closed

Four chambers Double

Two chambers Single

Three chambers Double

Insects

1. One or more hearts pump the heamolymph through vessels and into the haemocoel. 2. Haemocoel contains soft internal organs and is filled with haemolymph. 3. Here, chemical exhange occurs between the haemolymph and body cells. 4. Haemolymph flows out from the hearts into the haemocoel when the hearts contract. 5. When the hearts relax, haemolymph is drawn back into the hearts through pores called ostia. Fish

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Biology Form 5: Chapter 1

1. A heart with two main chambers, one atrium and one ventricle. 2. Blood leaving the ventricle will travel to the gill capillaries where gaseous exchange occurs. 3. The gill capillaries converge into a vessel that carries the oxygenated blood to the body (systemic) capillaries. 4. In the systemic capillaries, oxygen diffuses into the tissues while carbon dioxide diffuses out of the tissues and into the capillaries. 5. The deoxygenated blood then returns to the atrium of the heart via veins. 6. Single circulatory system - blood flows in only one direction. Amphibians

1. Three chambered heart, consisting of two atria and one ventricle. 2. Deoxygenated blood from the body is delivered into the right atrium and oxygenated blood from the lungs is delivered into the left atrium. 3. Blood from both atria then enters a single ventricle. 4. Although there is some mixing of oxygenated and deoxygenated blood inside the ventricle, most of the oxygenated blood remains in the left portion of the ventricle. 5. The ventricle then pumps blood through the a) pulmocutaneous circulation – leads to the gas exchange tissues, which are the lungs and skin. - gaseous exchange occurs. - oxygenated blood returns to the left atrium of the heart. b) systemic circulation. - carries oxygenated blood to body tissues and then returns deoxygenated blood to the right atrium via the veins. 6. Double circulatory system – blood flows through the heart twice. Humans 1. Four chambered heart, two atria and two completely separated ventricles. 2. Deoxygenated blood and oxygenated blood do not mix. 3. Pulmonary circulation: a) Deoxygenated blood is pumped into the pulmonary arteries. 9

Biology Form 5: Chapter 1

b) Theses arteries carry the blood to the lungs, where it es through the blood capillaries. c) This enables the release of carbon dioxide and the uptake of oxygen from the air. 4. Systemic circulation: a) Blood is carried from the heart to all parts of the body except the lungs. b) The oxygenated blood from the lungs return to the left atrium and flows into the left ventricle. c) Blood is then pumped to the body tissues through the aorta. 5. Double circulatory system – blood flows through the heart twice.

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