Functions and Components of the Circulatory System

Junior Science

Lesson Objectives

List the components of the Circulatory System.

Know the Functions of the Circulatory System

Explain the difference between an Artery, Vein and Capillary.

Organs

Heart

Vessels

Arteries

Capillaries

Veins

Tissues

Blood

(Blood cells and Plasma)

Cells

White blood Cells

Red Blood Cells

Platelets

Components of the Circulatory System

Blood Vessels

Blood flows throughout our body in blood vessels. There are three main categories of vessels:

Arteries thick, muscular walls carry blood away from the heart

Veins thin, stretchy, muscular walls return blood to the heart

Capillaries tiny blood vessels connect arteries and veins carry blood to the cells of the body

Linking the Vessels of the Circulatory System

Anatomy ofArteries

and Veins

Muscles movement and veins

Because veins have thin walls they need support to get blood back to the heart.

This is achieved through muscle action as the muscles help to push the blood back towards the heart.

The valves in veins prevent blood flowing backwards.

Veins

If the valves or the wall of the veins weaken, blood may flow backwards resulting in Varicose veins

Lesson Objectives

Know that blood is a tissue and list the cell types which compose blood.

List and explain the transport and defense functions of blood.

Give the functions of Plasma, Red Blood Cells, White blood cells and Platelets.

Function of the Blood

Transportation oxygen from lungs to tissues. carbon dioxide from tissues to lungs. waste products (Urea) from the liver to the

kidneys Nutrients from the small intestine to the tissues. Distribution of hormones. Acts as a heat and temperature regulator.

Defence Protects the body against infection and foreign

material Forms clots

What is Blood?

Blood is a tissue composed of Plasmaand Blood cells.

Plasma (55%) and Blood cells are (45%)

It travels around the body in over 75,000 miles of arteries, veins and capillaries.

Plasma is a pale yellow fluid that consists of about 92% water and 8% other substances, such as proteins, hormones, nutrients, gases, and waste products.

Plasma carries nutrients, hormonesand water to all parts of the body.

Red Blood Cell

White Blood Cell

Platelet

Plasma

Red Blood Cells

Red blood cells carry oxygen around the body.

This is helped by a special protein haemoglobin on the surface of the cell.

1 cm3 of human blood contains about 5 million red blood cells.

They are formed in the bone marrow.

The average life span is 120 days,

White Blood Cells

White blood cells kill bacteria ,combat infections / allergies

Ratio of red to white Cells 600 : 1.

Formed in bone marrow, the spleen, liver, and lymph nodes.of white

Life span 13 to 20 days.

Platelets

Platelets are small round fragments of cytoplasm with no nucleus.

Ratio of red to platelets 20:1

About one-third the size of red blood cells.

They are formed in the bone marrow.

Life Span 10 days

Summary

The circulatory systems include – the heart, arteries, veins, capillaries and blood.

The functions of the circulatory system include transportation of oxygen, waste product, hormones and nutrients. It also helps for clots and protects from for foreign bodies.

Blood consists of cells (red and white blood cells) platelets and plasma.

Veins carry deoxygenated blood back to the heart.

Arteries carry oxygenated blood around the body

Capillaries carry oxygen to the tissues of the body and remove carbon dioxide and waste from cells.