Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Describe the structure of the heart and trace blood flow.
• Explain the composition and functions of blood.
• Describe the structure and function of arteries, veins, and capillaries.
• Explain the structure and functioning of the lymphatic system.
• Understand how the circulatory and lymphatic systems maintain homeostasis.

Lesson summary

The transport system in humans is a vital network responsible for carrying essential substances like oxygen, nutrients, hormones, and immune cells throughout the body while removing waste products like carbon dioxide and urea. This system ensures that every cell in our body receives what it needs to function properly and gets rid of harmful byproducts. Understanding this system is crucial because malfunctions can lead to serious health problems, many of which are prevalent in South Africa. For example, understanding hypertension (high blood pressure) and its link to cardiovascular disease, a leading cause of death in South Africa, is directly related to the study of transport systems.

Lesson notes

2.1 The Heart: The Central Pump The heart is a muscular organ responsible for pumping blood throughout the body. It is located in the thoracic cavity, protected by the rib cage.

Structure: The heart has four chambers: Atria (right and left): The upper chambers that receive blood. The right atrium receives deoxygenated blood from the body, and the left atrium receives oxygenated blood from the lungs.

Ventricles (right and left): The lower chambers that pump blood out of the heart. The right ventricle pumps deoxygenated blood to the lungs, and the left ventricle pumps oxygenated blood to the body.

Valves: These prevent backflow of blood.

Atrioventricular valves (AV valves): Located between the atria and ventricles. The right AV valve is the tricuspid valve, and the left AV valve is the bicuspid (mitral) valve.

Semilunar valves: Located at the exit of each ventricle. The pulmonary valve is located between the right ventricle and the pulmonary artery, and the aortic valve is located between the left ventricle and the aorta.

Blood Vessels: Aorta: The largest artery in the body, carrying oxygenated blood from the left ventricle to the rest of 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.

Vena cava: The largest vein in the body, carrying deoxygenated blood from the body to the right atrium.

There are two vena cavae: the superior vena cava (from the upper body) and the inferior vena cava (from the lower body).

The Cardiac Cycle: This is the sequence of events in one complete heartbeat.

Systole: The contraction phase when the heart chambers pump blood.

Diastole: The relaxation phase when the heart chambers fill with blood.

Example: Trace the flow of blood through the heart, starting from the superior vena cava: Deoxygenated blood enters the right atrium. The right atrium contracts, forcing blood through the tricuspid valve into the right ventricle. The right ventricle contracts, forcing blood through the pulmonary valve into the pulmonary artery, which carries it to the lungs. In the lungs, blood releases carbon dioxide and picks up oxygen. Oxygenated blood returns to the heart through the pulmonary veins, entering the left atrium. The left atrium contracts, forcing blood through the bicuspid (mitral) valve into the left ventricle. The left ventricle contracts, forcing blood through the aortic valve into the aorta, which distributes it to the rest of the body. 2.2 Blood: The River of Life Blood is a connective tissue composed of plasma and formed elements (cells).

Plasma: The liquid component of blood, consisting mainly of water, dissolved proteins (e.g., albumin, globulins, fibrinogen), glucose, amino acids, hormones, electrolytes, and waste products. Plasma transports nutrients, hormones, and waste products.

Red Blood Cells (Erythrocytes): Biconcave disc-shaped cells without a nucleus. They contain hemoglobin, a protein that binds to oxygen, enabling oxygen transport. They are produced in the bone marrow. A low red blood cell count can lead to anemia, common amongst menstruating women in South Africa due to iron deficiency.

White Blood Cells (Leukocytes): Involved in the immune response.

There are several types: Neutrophils: Phagocytize bacteria and other pathogens.

Lymphocytes: Involved in specific immunity (T cells and B cells).

Monocytes: Develop into macrophages, which phagocytize pathogens and cellular debris.

Eosinophils: Involved in allergic reactions and parasitic infections.

Basophils: Release histamine, involved in inflammatory responses.

Platelets (Thrombocytes): Cell fragments involved in blood clotting. They are produced in the bone marrow.

Example: A person is diagnosed with a bacterial infection. Which type of blood cell would increase in number to fight the infection?

Answer: Neutrophils would increase in number. Neutrophils are phagocytes, meaning they engulf and destroy bacteria. The bone marrow would increase production of neutrophils in response to the infection. 2.3 Blood Vessels: The Highways Blood vessels form a network that carries blood throughout the body.

There are three main types: Arteries: Carry blood away from the heart. They have thick, elastic walls to withstand high pressure. The aorta is the largest artery.

Veins: Carry blood towards the heart. They have thinner walls and valves to prevent backflow. The vena cava is the largest vein.

Capillaries: Tiny, thin-walled vessels that connect arteries and veins. They are the site of exchange of nutrients, gases, and waste products between the blood and body tissues. Their thin walls (single layer of endothelial cells) allow for efficient diffusion.

Example: Explain the difference in structure between arteries and veins, and how this relates to their function.

Answer: Arteries have thicker, more elastic walls than veins. This is because arteries carry blood under high pressure directly from the heart.