Lesson Notes By Weeks and Term v5 - Grade 11
Transport systems in humans – Week 8 focus
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Transport systems in humans – Week 8 focus
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Subject: Life Sciences
Class: Grade 11
Term: 2nd Term
Week: 8
Theme: General lesson support
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The human transport system, also known as the circulatory system, is responsible for delivering oxygen, nutrients, hormones, and immune cells throughout the body and removing waste products such as carbon dioxide. A healthy circulatory system is crucial for overall health and well-being. Issues with this system, like high blood pressure, can lead to serious health problems such as heart disease and stroke, which are prevalent in South Africa. Understanding how this system works allows us to make informed decisions about our health and adopt lifestyles that promote its proper functioning.
2.1 The Human Heart: Structure and Function The heart is a muscular organ responsible for pumping blood throughout the body. It's located in the chest cavity, protected by the rib cage.
Structure: Chambers: The heart has four chambers: two atria (right and left) and two ventricles (right and left). The atria receive blood returning to the heart, while the ventricles pump blood out.
Valves: Valves ensure unidirectional blood flow, preventing backflow.
Atrioventricular (AV) valves: Located between the atria and ventricles. The tricuspid valve is on the right side, and the bicuspid (mitral) valve is on the left.
Semilunar valves: Located at the exit of each ventricle. The pulmonary valve is at the exit of the right ventricle, leading to the pulmonary artery, and the aortic valve is at the exit of the left ventricle, leading to the aorta.
Major Blood Vessels: Aorta: The largest artery, carrying oxygenated blood from the left ventricle to the body.
Pulmonary Artery: Carries deoxygenated blood from the right ventricle to the lungs.
Pulmonary Veins: Carry oxygenated blood from the lungs to the left atrium.
Superior and Inferior Vena Cava: Carry deoxygenated blood from the body to the right atrium.
Function: The heart functions as a double pump.
Right Side: Receives deoxygenated blood from the body via the superior and inferior vena cava, pumps it to the lungs via the pulmonary artery for oxygenation.
Left Side: Receives oxygenated blood from the lungs via the pulmonary veins, pumps it to the body via the aorta. The cardiac cycle involves alternating periods of contraction (systole) and relaxation (diastole). The heart sounds ("lub-dub") are produced by the closing of the valves. 2.2 Pulmonary and Systemic Circulation The circulatory system consists of two main circuits: Pulmonary Circulation: Involves the flow of blood between the heart and the lungs. Deoxygenated blood is pumped from the right ventricle to the lungs through the pulmonary artery. In the lungs, carbon dioxide is exchanged for oxygen. Oxygenated blood returns to the left atrium through the pulmonary veins.
Systemic Circulation: Involves the flow of blood between the heart and the rest of the body. Oxygenated blood is pumped from the left ventricle to the body through the aorta. Oxygen is delivered to tissues, and carbon dioxide is picked up. Deoxygenated blood returns to the right atrium through the superior and inferior vena cava. 2.3 Blood Vessels: Arteries, Veins, and Capillaries Arteries: Carry blood away from the heart. They have thick, elastic walls to withstand high pressure. They branch into smaller vessels called arterioles.
Veins: Carry blood back to the heart. They have thinner walls than arteries and contain valves to prevent backflow, especially in the limbs, countering gravity. They receive blood from venules, which are formed from capillaries.
Capillaries: Tiny, thin-walled vessels that connect arterioles and venules. They are the site of exchange of nutrients, gases, and waste products between the blood and body cells. Their walls are only one cell thick to facilitate diffusion. 2.4 Composition and Functions of Blood Blood is a connective tissue composed of: Plasma: The liquid component of blood (about 55%). It contains water, proteins (e.g., albumin, globulins, fibrinogen), electrolytes, nutrients, hormones, and waste products. Plasma transports blood cells, nutrients, and waste.
Red Blood Cells (Erythrocytes): Transport oxygen. They contain hemoglobin, a protein that binds to oxygen. They are biconcave in shape to increase surface area for oxygen diffusion and lack a nucleus to maximize hemoglobin content.
White Blood Cells (Leukocytes): Involved in the immune response. There are different types of white blood cells, each with a specific function (e.g., neutrophils, lymphocytes, monocytes). They defend the body against pathogens.
Platelets (Thrombocytes): Involved in blood clotting. They are small, cell fragments that help to stop bleeding by forming a platelet plug. 2.5 ABO and Rh Blood Group Systems ABO Blood Group System: Based on the presence or absence of A and B antigens on the surface of red blood cells.
There are four blood types: A, B, AB, and O. Blood type O lacks both A and B antigens. | Blood Type | Antigens on RBCs | Antibodies in Plasma | Can Receive Blood From | |------------|-----------------|------------------------|-------------------------| | A | A | Anti-B | A, O | | B | B | Anti-A | B, O | | AB | A and B | Neither | A, B, AB, O | | O | Neither | Anti-A and Anti-B | O | Rh Blood Group System: Based on the presence or absence of the Rh factor (D antigen) on the surface of red blood cells. Individuals with the Rh factor are Rh-positive (Rh+), and those without are Rh-negative (Rh-). Rh incompatibility can occur during pregnancy if an Rh- mother carries an Rh+ fetus.