Circulatory System(closed system)

Circulatory System

• Circulatory System: The body system consisting of the heart, blood vessels, and the blood that is responsible for the transportation of material around the body and plays a major role in the regulation of body temperatures.

• Appears to be connected to all other systems.• All cells in the body are within 2 cells of a blood cell.

Four Main Functions

1. Transportation of oxygen and carbon dioxide.

2. Distribution of nutrients and transportation of wastes.

3. Maintenance of body temperature.

4. Circulation of hormones.

Made up of 2 Systems:

1. Pulmonary Circuit: the system of blood vessels that carries deoxygenated blood to the lungs and oxygenated blood back to the heart.

2. Systemic Circuit: the system of blood vessels that carries oxygenated blood to the tissues of the body and deoxygenated blood back to the heart.

Blood• Your body contains about 4 to 6 L of blood.

• Your blood has several functions that are essential to good health.– transports oxygen, water, nutrients, and other

chemicals to your cells– removes waste products from the tissues– helps to regulate body temperature, fight

infection, and heal wounds.

Components of Blood

– Plasma– Red blood cells– White blood cells– Platelets

Plasma:• 90 % water• remaining 10 % is made of proteins, dissolved

nutrients, and wastes

Red Blood Cells• 45 % of blood volume consists mostly of red blood cells. • Red blood cells carry oxygen from the lungs to all the tissues

of the body. • Each RBC contains about 250 million molecules of

hemoglobin– Protein that binds oxygen in the lungs and releases it

throughout the body.• RBC transport carbon dioxide to the lungs.• produced in bone marrow at the rate of two million per

second in a healthy adult.

• Shape: flat disk that curves inward in the middle on both the top and bottom.

• Mature RBC have no nucleus– it cannot grow, or divide.

• The typical lifespan of a red blood cell is between 100 and 120 days.

White Blood Cells• guard against infection, fight parasites, and attack

bacteria. • do not have to stay within the blood vessels. • when infection invades your body, the number of

white blood cells dramatically increases.– For example, if you get a cut, white blood cells

gather at the cut to fight bacteria.

• Pus is a combination of white blood cells and dead bacteria.

• white blood cells are produced in the bone marrow. • white blood cells keep their nuclei and can live for

years.

Platelets• The clotting process depends on plasma proteins and

cell fragments called platelets. • Each cubic millimetre of blood contains between 250

000 and 500 000 platelets.

• Clotting begins when platelets stick to the site where the blood vessel is damaged.

• They break apart and release clotting factors. – The clotting factors make other nearby platelets sticky and

activate a series of reactions– These reactions result in the formation of a strand-like

protein called fibrin. • Fibrin threads trap red blood cells and platelets. • forming a patch that stretches over the torn tissue. • This patch dries into a scab

Electron Micrograph of Blood

Blood Vessels

3 types of blood vessels:• Arteries• Capillaries• veins

ArteriesArteries are large blood vessels that carry blood from the heart to the tissues. • The blood in arteries is under pressure. This pressure helps to ensure that

blood flows only in one direction• The arteries branch into smaller and smaller vessel called arterioles which

flow into capillaries.

Veins• The muscle layer in veins is thinner than that in arteries because the blood

in veins is under very little pressure• A series of valves allows blood to only move in one direction (towards the

heart or UP)• Small veins called venuoles merge together into larger veins.

Capillaries Capillaries are microscopic blood vessels with a high surface area.• The nutrients and oxygen pass out of the blood, and waste products pass

into the blood here

Blood Vessels• Blood vessels that carry the blood from the heart to the cells of the body

and back:

heart aorta (largest artery) other Arteries arterioles capillaries venuoles veins vena cave (largest veins) heart

Where would blood pressure be the highest? Lowest?

Colour• Vein colour is determined in large part by the color of venous blood, which

is usually dark red (and not blue as is commonly believed) as a result of its low oxygen content. Veins appear blue because the subcutaneous fat absorbs low-frequency light, permitting only the highly energetic blue wavelengths to penetrate through to the dark vein and reflect back to the viewer. A recent study found the colour of blood vessels is determined by the following factors: the scattering and absorption characteristics of skin at different wavelengths, the oxygenation state of blood, which affects its absorption properties, the diameter and the depth of the vessels, and the visual perception process.