Biology Grade 11: Circulation.

Circulation is the process by which blood is pumped around the body by the heart, delivering oxygen and nutrients to cells and removing waste products. The circulatory system consists of the heart, blood vessels, and blood.

The heart is a muscular organ that pumps blood throughout the body. It is divided into four chambers: the right atrium, right ventricle, left atrium, and left ventricle. Blood enters the heart through the atria and is pumped out through the ventricles.

Blood vessels are the tubes that carry blood throughout the body. There are three main types of blood vessels: arteries, veins, and capillaries. Arteries carry oxygen-rich blood away from the heart, veins carry oxygen-poor blood back to the heart, and capillaries are tiny blood vessels where oxygen and nutrients are exchanged with cells.

Blood is composed of red blood cells, white blood cells, platelets, and plasma. Red blood cells carry oxygen to cells and remove carbon dioxide, white blood cells help fight infection, platelets help with blood clotting, and plasma is the liquid portion of blood that carries nutrients and waste products.

The circulatory system is essential for maintaining homeostasis in the body, as it helps regulate body temperature, pH levels, and fluid balance. It also plays a crucial role in the immune response, as white blood cells help fight off pathogens and foreign invaders.

Overall, circulation is a vital process that ensures the proper functioning of all cells and organs in the body.

Circulation

Definition:
Circulation refers to the movement of fluids throughout the body, primarily blood and lymph. It is responsible for transporting nutrients, oxygen, hormones, and waste products to and from cells.

Components of the Circulatory System:

1. Heart:
- A muscular organ that pumps blood throughout the body.
- Consists of four chambers: two atria (upper chambers) and two ventricles (lower chambers).

2. Blood Vessels:
- Arteries: Carry oxygenated blood away from the heart.
- Veins: Carry deoxygenated blood back to the heart.
- Capillaries: Tiny, thin-walled vessels that allow exchange of materials between the blood and tissues.

3. Blood:
- A fluid tissue that contains red blood cells, white blood cells, platelets, and plasma.

4. Lymph Vessels:
- A network of vessels that collect fluid and debris from tissues.

Types of Circulation:

1. Systemic Circulation:
- The main circuit that carries blood from the heart to the body's organs and tissues and back.
- Begins in the left ventricle of the heart and ends in the right atrium.

2. Pulmonary Circulation:
- A smaller circuit that carries blood from the heart to the lungs and back.
- Begins in the right ventricle of the heart and ends in the left atrium.

Function of Circulation:

- Transport: Transports nutrients, oxygen, hormones, and waste products throughout the body.
- Regulation: Regulates body temperature, pH, and fluid balance.
- Protection: Helps protect the body against infection and disease through white blood cells and antibodies.
- Waste removal: Removes waste products from cells and transports them to the kidneys and lungs for excretion.

Control of Circulation:

- Cardiac Center: A group of cells in the heart that regulates the heart rate.
- Autonomic Nervous System: Controls the diameter of blood vessels to regulate blood pressure.
- Hormones: Stimulate the heart to increase or decrease the heart rate and blood pressure.

Disorders of the Circulatory System:

- Cardiovascular disease: A group of disorders that affect the heart and blood vessels, such as heart attack, stroke, and hypertension.
- Anemia: A deficiency of red blood cells that leads to fatigue and shortness of breath.
- Leukemia: A cancer of white blood cells.
- Varicose Veins: Enlarged, twisted veins that can cause pain and swelling.