Lesson Notes By Weeks and Term v3 - Senior Secondary 1
Blood circulatory system
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Blood circulatory system
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Physical Education
Class: Senior Secondary 1
Term: 3rd Term
Week: 4
Theme: Basic Human Anatomy And Physiology In Relation To Physical Activities
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Watch on YouTubedescribe the composition of blood state functions of blood. differentiate between the two types of circulation.
This topic covers the composition of blood, its various functions, and the two major types of circulation within the human body. A. Composition of Blood Blood is a specialized connective tissue that circulates throughout the body.
It consists of two main components: plasma and blood cells.
1. Blood Plasma (approximately 55% of blood volume): This is the liquid component of blood, yellowish in colour. It is mostly water (about 90-92%), which serves as a solvent and transport medium.
Components dissolved in plasma: Plasma Proteins: Albumin (maintains osmotic pressure), Globulins (antibodies for immunity, transport proteins), Fibrinogen (essential for blood clotting).
Nutrients: Glucose, amino acids, fatty acids, vitamins, and minerals absorbed from the digestive system.
Hormones: Chemical messengers from endocrine glands.
Gases: Small amounts of oxygen, carbon dioxide, and nitrogen.
Electrolytes (Salts): Sodium, potassium, calcium, magnesium, chloride, bicarbonate ions – crucial for nerve and muscle function, and maintaining pH balance.
Waste Products: Urea, uric acid, creatinine, lactic acid – transported to excretory organs (kidneys, liver) for removal.
2. Formed Elements / Blood Cells (approximately 45% of blood volume): These are the cellular components suspended in the plasma.
Red Blood Cells (Erythrocytes): Most numerous blood cells (about 4.5-5.5 million per cubic millimetre of blood). Biconcave disc shape, increasing surface area for gas exchange. Lack a nucleus when mature, which allows more space for haemoglobin.
Contain Haemoglobin: an iron-containing protein that binds to oxygen, giving blood its red colour. Produced in the red bone marrow. Life span of approximately 120 days.
Main function: Transport oxygen from the lungs to the body tissues and transport a small amount of carbon dioxide from tissues back to the lungs.
Nigerian context example: Anaemia, a common condition in Nigeria often caused by iron deficiency, results from a reduced number of red blood cells or insufficient haemoglobin, leading to fatigue and weakness. Malaria also destroys red blood cells, causing anaemia.
White Blood Cells (Leukocytes): Fewer in number than red blood cells (about 4,000-11,000 per cubic millimetre). Larger than red blood cells and possess a nucleus. Irregular shape, capable of amoeboid movement to engulf pathogens. Classified into different types (e.g., neutrophils, lymphocytes, monocytes, eosinophils, basophils), each with specific immune functions.
Main function: Defend the body against infection by identifying and destroying foreign invaders (bacteria, viruses, fungi) and removing dead cells. They are crucial for the body's immune response.
Platelets (Thrombocytes): Not complete cells, but cell fragments derived from large cells called megakaryocytes in the bone marrow. Small, irregular, and anucleated.
Main function: Essential for blood clotting (hemostasis) to prevent excessive blood loss from injuries. They aggregate at the site of injury and initiate the clotting cascade. B. Functions of Blood Blood performs several critical functions to maintain homeostasis (internal stability) in the body:
1. Transportation: Gases: Transports oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs.
Nutrients: Carries absorbed nutrients (glucose, amino acids, vitamins, minerals) from the digestive tract to body cells.
Hormones: Transports hormones from endocrine glands to their target organs.
Waste Products: Carries metabolic waste products (e.g., urea, uric acid) from tissues to the kidneys and liver for excretion.
2. Regulation: Body Temperature: Distributes heat throughout the body, helping to maintain a stable core temperature (e.g., dissipating heat to the skin surface in hot environments common in Nigeria). pH Balance: Contains buffer systems (e.g., bicarbonate buffer) that help maintain the body's optimal pH level (slightly alkaline, 7.35-7.45).
Fluid and Electrolyte Balance: Plasma proteins and salts help regulate water balance between blood and tissues.
3. Protection: Blood Clotting (Hemostasis): Platelets and plasma clotting factors prevent excessive blood loss from injuries. This is critical in preventing fatal haemorrhage.
Immunity: White blood cells and antibodies (plasma proteins) protect the body against pathogens (bacteria, viruses) and foreign substances, thus fighting infections and diseases. C. Two Types of Circulation The human circulatory system is a closed double-circuit system, meaning blood passes through the heart twice for each complete circuit of 7.35-7.45).
Fluid and Electrolyte Balance: Plasma proteins and salts help regulate water balance between blood and tissues.
3. Protection: Blood Clotting (Hemostasis): Platelets and plasma clotting factors prevent excessive blood loss from injuries. This is critical in preventing fatal haemorrhage.
Immunity: White blood cells and antibodies (plasma proteins) protect the body against pathogens (bacteria, viruses) and foreign substances, thus fighting infections and diseases. C. Two Types of Circulation The human circulatory system is a closed double-circuit system, meaning blood passes through the heart twice for each complete circuit of the body. The heart acts as a powerful pump, ensuring blood flow.
The two main types of circulation are:
1. Pulmonary Circulation: Purpose: To transport deoxygenated blood from the heart to the lungs to pick up oxygen and release carbon dioxide, then return the freshly oxygenated blood to the heart.
Pathway: Deoxygenated blood from the body enters the right atrium of the heart. It then flows into the right ventricle. The right ventricle pumps this deoxygenated blood into the pulmonary artery (the only artery that carries deoxygenated blood). The pulmonary artery branches into smaller arteries and capillaries within the lungs. In the lung capillaries, gas exchange occurs: carbon dioxide is released from the blood into the air sacs (alveoli) and exhaled, while oxygen is absorbed from the inhaled air into the blood. The now oxygenated blood collects into the pulmonary veins (the only veins that carry oxygenated blood). The pulmonary veins return this oxygenated blood to the left atrium of the heart.
2. Systematic Circulation: Purpose: To transport oxygenated blood from the heart to all body tissues (except the lungs) to deliver oxygen and nutrients, and to collect deoxygenated blood and waste products to return to the heart.
Pathway: Oxygenated blood from the lungs enters the left atrium of the heart (via pulmonary veins). It then flows into the left ventricle. The left ventricle, the strongest chamber, pumps this oxygenated blood with high pressure into the aorta (the body's largest artery). The aorta branches into major arteries, which further divide into smaller arteries (arterioles) and then into a network of tiny capillaries throughout all body tissues and organs (e.g., brain, muscles, liver, kidneys, skin). In the tissue capillaries, oxygen and nutrients diffuse from the blood into the tissue cells, while carbon dioxide and metabolic waste products from the cells diffuse into the blood. The now deoxygenated blood collects into small veins (venules), which merge into larger veins. These veins eventually merge into the superior vena cava (collecting blood from the upper body) and the inferior vena cava (collecting blood from the lower body). The vena cavae return the deoxygenated blood to the right atrium of the heart, completing the systemic circuit and restarting the pulmonary circuit.
Teacher Activities: Introduction (10 minutes): Begin by asking students to brainstorm what they know about blood and its importance. Use open-ended questions like, "What do you think happens when someone gets a cut and bleeds?" or "Why do people sometimes need blood transfusions?" Introduce the topic: "The Blood Circulatory System" and state the learning objectives in clear, simple terms for the students. Show a large, clear diagram of the human body highlighting the circulatory system, or a model of the heart, if available. Explanation of Blood Composition (20 minutes): Explain the two main components of blood (plasma and formed elements). Elaborate on plasma and its contents, using simple analogies (e.g., plasma as the "river" carrying various items). Discuss red blood cells, white blood cells, and platelets individually. Use a microscope slide of blood (if available) or detailed diagrams to show their appearance. Relate red blood cells to anaemia and malaria in Nigeria, and white blood cells to fighting common infections. Facilitate a short Q&A session to check understanding. Explanation of Blood Functions (15 minutes): Categorize blood functions into transportation, regulation, and protection. Provide specific examples for each category (e.g., oxygen transport, temperature regulation in Nigeria's climate, clotting for wounds, fighting diseases). Encourage students to provide their own examples of how blood helps the body. Explanation of Types of Circulation (25 minutes): Introduce the concept of a "double circulation" system. Explain pulmonary circulation step-by-step, perhaps using a diagram and tracing the path of blood with a coloured marker or pointer. Emphasize the role of the lungs. Similarly, explain systemic circulation step-by-step, highlighting its role in delivering oxygen/nutrients to all other body parts.
Use an analogy: "Think of the heart as a bus terminal. One bus route (pulmonary) goes to the fuel station (lungs) to get fuel (oxygen), and another bus route (systemic) delivers passengers (oxygen, nutrients) to all parts of the city (body tissues)." Lead a comparative discussion: "What is the key difference in what blood carries to and from the heart in each circuit?" Activity - Diagram Drawing (10 minutes): Instruct students to draw a simplified diagram of the heart and the two circulatory pathways, labelling the key organs and vessels. This can be a quick sketch to consolidate understanding.
Conclusion (5 minutes): Summarize the key takeaways of the lesson, reinforcing the composition, functions, and types of blood circulation. Address any remaining questions.
Student Activities: Participate in brainstorming sessions and answer introductory questions. Take notes as the teacher explains. Observe diagrams, charts, or models of the circulatory system. Engage in Q&A sessions, asking and answering questions about blood components and functions. Participate in group discussions comparing and contrasting the two types of circulation. Draw a simplified diagram of the circulatory system, tracing the path of blood in both pulmonary and systemic circulation. Share examples of the importance of blood in daily life and health. The teacher should guide students through these questions, providing support and clarification as needed.
Question 1: List four components of blood and briefly state one role for each.
Solution 1: Plasma: Acts as a transport medium for nutrients, hormones, and waste products.
Red Blood Cells: Primarily transport oxygen from the lungs to the body tissues.
White Blood Cells: Defend the body against infection and foreign invaders.
Platelets: Initiate and facilitate blood clotting to prevent blood loss.
Commentary: This question assesses the students' foundational knowledge of the constituents of blood and their basic roles. It checks their ability to recall and associate function with structure.
Question 2: Identify three vital functions blood performs in the human body.
Solution 2: Transportation: Blood transports essential substances such as oxygen, nutrients, hormones, and waste products throughout the body.
Regulation: Blood helps regulate body temperature by distributing heat, maintains pH balance, and controls fluid levels in the body.
Protection: Blood protects the body through clotting to prevent blood loss from injuries and through white blood cells and antibodies that fight infections and foreign substances.
Commentary: This question evaluates the students' understanding of the broad categories of blood's functions. It requires them to generalize and identify core roles rather than minute details.
Question 3: Explain the primary difference in the destination and purpose of pulmonary circulation versus systematic circulation.
Solution 3: Pulmonary Circulation: The blood's primary destination is the lungs. Its purpose is to pick up oxygen and release carbon dioxide, thereby oxygenating the blood.
Systematic Circulation: The blood's primary destination is all other body tissues and organs (excluding the lungs). Its purpose is to deliver oxygen and nutrients to these tissues and collect carbon dioxide and waste products from them.
Commentary: This question requires students to differentiate between the two types of circulation based on their distinct routes and physiological goals, which is a key learning objective.
Health Education and Lifestyle Choices: Understanding the circulatory system is fundamental to appreciating the importance of a healthy lifestyle. For instance, knowing that blood transports nutrients and oxygen highlights why a balanced diet (e.g., iron-rich foods to prevent anaemia, common in Nigerian children and pregnant women) and regular physical exercise (to strengthen the heart and improve circulation) are crucial for preventing non-communicable diseases like hypertension and heart disease, which are on the rise in Nigeria.
First Aid and Emergency Response: Knowledge of blood composition and clotting is vital in basic first aid. Students can learn why applying pressure to a bleeding wound helps, how different types of injuries affect blood loss, and the importance of professional medical care in cases of severe bleeding or shock, a common scenario in accident sites across Nigerian roads.
Blood Donation and Transfusion: The lesson provides a context for understanding the importance of voluntary blood donation in Nigeria. Explaining blood components (e.g., that someone needing red blood cells due to anaemia or accident trauma may not need plasma) helps students grasp why blood transfusions save lives, particularly for accident victims, during childbirth complications, and for patients with conditions like sickle cell anaemia prevalent in some Nigerian communities. This understanding can encourage responsible citizenship and community contribution.