Circulatory System JHS 3 (Basic 9)

 

THE HUMAN CIRCULATORY SYSTEM

JHS 3 (SYSTEMS)

INTRODUCTION

The human circulatory system, also known as the cardiovascular system, consists of a network of arteries, veins, and capillaries, with the heart pumping blood through it. Its primary role is to provide essential nutrients, minerals, and hormones to various parts of the body. Alternatively, the circulatory system is also responsible for collecting metabolic waste and toxins from the cells and tissues to be purified or expelled from the body.

Crucial features of the human circulatory system

·         Blood – A fluid that carries essential substances.

·         Blood Vessels – Tubes through which blood flows (arteries, veins, and capillaries).

·         The Heart – A muscular organ that pumps blood. Features of Circulatory System

·         The human circulatory system consists of blood, heart, blood vessels, and lymph.

·         The human circulatory system circulates blood through two loops (double circulation) – One for oxygenated blood, another for deoxygenated blood.

·         The human heart consists of four chambers – two ventricles and two auricles.

·         The human circulatory system possesses a body-wide network of blood vessels. These comprise arteries, veins, and capillaries.

·         The primary function of blood vessels is to transport oxygenated blood and nutrients to all parts of the body. It is also tasked with collecting metabolic wastes to be expelled from the body.

The circulatory system plays a vital role in ensuring that oxygen and nutrients reach all body parts while removing waste products like carbon dioxide.

 

COMPOSITION AND FUNCTIONS OF BLOOD

Blood is a liquid connective tissue that makes up about 8% of body weight. It consists of:

1. Plasma (55% of Blood)

Plasma is the liquid portion of blood, composed mainly of water (90%), nutrients, hormones, proteins, and waste products.

Functions of Plasma

        i.            Transports nutrients (glucose, amino acids, vitamins).

      ii.            Carries hormones for body regulation.

    iii.            Removes waste products (carbon dioxide, urea).

    iv.            Maintains body temperature.

 

 

2. Blood Cells (45% of Blood)

Blood cells are divided into three main types:

A. Red Blood Cells (Erythrocytes)

• Biconcave shape to increase surface area for oxygen transport.
• No nucleus (to allow more hemoglobin).
• Contain hemoglobin, a protein that binds oxygen.

Functions:
✔️ Transport oxygen from the lungs to tissues.
✔️ Carry carbon dioxide back to the lungs for exhalation.

 

B. White Blood Cells (Leukocytes) – The Body’s Defense System

White blood cells fight infections and protect the body. They are larger than red blood cells but fewer in number.

Types of White Blood Cells and Their Functions:

1. Phagocytes
• Engulf and destroy bacteria through phagocytosis.
• Examples: Neutrophils, Monocytes.
2. Lymphocytes
• Produce antibodies to fight infections.
• Examples: B cells (produce antibodies), T cells (attack infected cells).
3. Basophils & Eosinophils
• Help fight allergic reactions and parasites.

C. Platelets (Thrombocytes) – Blood Clotting Cells

• Small, irregularly shaped cell fragments.
• Help clot blood and prevent excessive bleeding.

Functions

        i.            Prevent blood loss by forming clots.

      ii.            Help in wound healing.

       

 

MOVEMENT OF BLOOD IN THE BODY (CIRCULATION TYPES)

Blood moves continuously through the body in a looped pathway. There are three types of circulation:

1. Pulmonary Circulation (Lungs)

• Function: Carries deoxygenated blood from the heart to the lungs for oxygenation and back to the heart.
• Pathway:
• Right ventricle → Pulmonary artery → Lungs (oxygenation) → Pulmonary vein → Left atrium.

2. Systemic Circulation (Whole Body)

• Function: Supplies oxygenated blood to all body parts and brings back deoxygenated blood.
• Pathway:
• Left ventricle → Aorta → Body organs → Veins → Right atrium.

3. Coronary Circulation (Heart Muscles)

• Function: Provides oxygen and nutrients to the heart itself.
• Pathway:
• Aorta → Coronary arteries → Heart muscle → Coronary veins → Right atrium.

 

 PARTS OF THE CIRCULATORY SYSTEM AND THEIR FUNCTIONS

The circulatory system consists of:

1. The Heart (pumps blood).
2. Blood Vessels (carry blood).
3. Circulatory Pathways (pulmonary, systemic, and coronary circulation).

 

1. THE HEART – THE BLOOD PUMP

The heart is a muscular organ that continuously pumps blood. It is divided into four chambers:

Chamber	Function
Right Atrium	Receives deoxygenated blood from the body via the vena cava.
Right Ventricle	Pumps deoxygenated blood to the lungs via the pulmonary artery.
Left Atrium	Receives oxygenated blood from the lungs via the pulmonary veins.
Left Ventricle	Pumps oxygenated blood to the whole body via the aorta.

Valves of the Heart

• Prevent backflow of blood and ensure one-way circulation.
• Types of Valves:
• Tricuspid Valve (between right atrium and right ventricle).
• Bicuspid (Mitral) Valve (between left atrium and left ventricle).
• Semilunar Valves (at the exits of the heart).

2. BLOOD VESSELS – THE TRANSPORT NETWORK

a) Arteries (Carry Blood Away from the Heart)

• Thick, muscular, and elastic walls to handle high pressure.
• Carry oxygenated blood, except the pulmonary artery.
• Main artery: Aorta (largest artery).

b) Veins (Carry Blood Back to the Heart)

• Thinner walls with valves to prevent backflow.
• Carry deoxygenated blood, except the pulmonary vein.
• Main vein: Vena Cava.

c) Capillaries (Exchange of Gases and Nutrients)

• Very thin walls (one-cell thick).
• Allow oxygen, nutrients, and waste exchange between blood and cells.

 DISEASES OF THE CIRCULATORY SYSTEM, CAUSES, AND PREVENTION

Disease	Cause	Prevention
Hypertension (High Blood Pressure)	Stress, obesity, high salt intake, genetics	Reduce salt intake, exercise, manage stress
Atherosclerosis	Fat buildup in arteries	Eat less fat, exercise, avoid smoking
Heart Attack	Blocked coronary arteries	Healthy diet, exercise, avoid smoking
Stroke	Blocked/burst blood vessel in the brain	Blood pressure control, no smoking, exercise

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BLOOD PRESSURE AND WAYS TO MANAGE IT

What is Blood Pressure?

Blood pressure is the force exerted by blood on artery walls. It is measured as:

• Systolic Pressure (upper number) – When the heart contracts.
• Diastolic Pressure (lower number) – When the heart relaxes.

Normal blood pressure: 120/80 mmHg.

Ways to Manage Blood Pressure

·         Eat a healthy diet (low salt, high fiber).

·         Exercise regularly.

·         Reduce stress through relaxation techniques.

·         Avoid smoking and excessive alcohol.

·         Get regular health checkups.

High Blood Pressure (HBP) and Low Blood Pressure (LBP): Causes and Prevention

Blood pressure is the force exerted by circulating blood against the walls of the arteries. It is measured in millimeters of mercury (mmHg) and recorded as two numbers:

• Systolic pressure (top number): The pressure when the heart beats.
• Diastolic pressure (bottom number): The pressure when the heart rests between beats.

A normal blood pressure reading is typically around 120/80 mmHg. Any significant deviation from this can indicate a health problem.

High Blood Pressure (HBP) – Hypertension

Definition of High Blood Pressure
High blood pressure occurs when the force of blood against artery walls is consistently too high, leading to health risks like heart disease, stroke, and kidney problems.

 

Causes of High Blood Pressure

1. Unhealthy Diet – High salt (sodium), saturated fats, and processed foods.
2. Lack of Physical Activity – A sedentary lifestyle leads to poor heart function.
3. Obesity – Excess weight increases the workload on the heart.
4. Stress – Chronic stress can elevate blood pressure levels.
5. Genetics – Family history plays a role in developing hypertension.
6. Smoking and Alcohol – Nicotine and excessive alcohol raise blood pressure.
7. Chronic Conditions – Diabetes, kidney disease, and hormonal disorders.

 

Prevention of High Blood Pressure

• Healthy Diet: Eat more fruits, vegetables, whole grains, and lean proteins. Reduce salt and processed foods.
• Regular Exercise: Engage in at least 30 minutes of moderate exercise daily.
• Maintain Healthy Weight: Losing excess weight lowers blood pressure.
• Manage Stress: Practice relaxation techniques like deep breathing and meditation.
• Limit Alcohol and Avoid Smoking: Reduce alcohol intake and quit smoking.
• Regular Checkups: Monitor blood pressure regularly and seek medical advice if necessary.

 

Low Blood Pressure (LBP) – Hypotension

Definition of Low Blood Pressure

Low blood pressure occurs when blood flows through the arteries at an abnormally low pressure, causing dizziness, fainting, and shock in severe cases. Both high and low blood pressure can have serious health effects if not managed properly. A balanced lifestyle, regular checkups, and awareness of symptoms can help prevent and control these conditions effectively.

 

Causes of Low Blood Pressure

1. Dehydration – Low fluid levels reduce blood volume.
2. Nutrient Deficiency – Lack of iron, vitamin B12, and folate can cause anemia and low blood pressure.
3. Heart Problems – Weak heart function can lead to reduced blood circulation.
4. Endocrine Disorders – Hormonal imbalances (e.g., thyroid disease) can lower blood pressure.
5. Medications – Some drugs for hypertension, depression, or Parkinson’s disease can lower BP.
6. Blood Loss – Severe bleeding can lead to dangerously low blood pressure.
7. Infections – Severe infections (septicemia) can cause a drastic drop in blood pressure.

 

Prevention of Low Blood Pressure

• Stay Hydrated: Drink enough water, especially in hot weather or after exercise.
• Eat Balanced Meals: Include sufficient salt, iron, and B vitamins in your diet.
• Avoid Prolonged Standing: Standing for long periods can cause blood pooling, leading to dizziness.
• Change Positions Slowly: When getting up from sitting or lying down, do so gradually.
• Manage Underlying Conditions: Treat heart disease, diabetes, or infections that may contribute to low BP.

 

Lymphatic System

The human circulatory system consists of another body fluid called lymph. It is also known as tissue fluid. It is produced by the lymphatic system which comprises a network of interconnected organs, nodes and ducts.

Lymph is a colourless fluid consisting of salts, proteins, water, which transport and circulates digested food and absorbed fat to intercellular spaces in the tissues. Unlike the circulatory system, lymph is not pumped; instead, it passively flows through a network of vessels.

Functions of Circulatory System

The most important function of the circulatory system is transporting oxygen throughout the body. The other vital functions of the human circulatory system are as follows:

1. It helps in sustaining all the organ systems.
2. It transports blood, nutrients, oxygen, carbon dioxide and hormones throughout the body.
3. It protects cells from pathogens.
4. It acts as an interface for cell-to-cell interaction.
5. The substances present in the blood help repair the damaged tissue.

 

CONCLUSION

The human circulatory system is essential for transporting oxygen, nutrients, and waste. It consists of the heart, blood vessels, and blood, each with important functions. Proper care through a healthy lifestyle can prevent circulatory diseases like hypertension, heart attacks, and strokes.

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