The circulatory system carries blood and dissolved

substances to and from different places in the body. The Heart has the job of pumping these things around

the body. The Heart pumps blood and substances around

the

body in tubes called blood vessels. The Heart and blood vessels together make up the

Circulatory System.

What is the circulatory system?

Lungs

Body cells

Our circulatory system is a double circulatory system.

This means it has two parts parts.

the right side of

the system

deals with

deoxygenated

blood.

the left side of

the system

deals with

oxygenated

blood.

Two circulatory paths

Pulmonary

Systemic

The double pump

The Heart

These are arteries. They carry blood away from the heart.

This is a vein. It brings blood from the body, except the lungs.

Coronary arteries, the hearts own blood supply

The heart has four chambers

2 atria

2 ventricles

now lets look inside the heart

The Heart

Left Ventricle

Left AtriumRight Atrium

Right Ventricle

valve

Vein from Lungs

Artery to Head and BodyArtery to Lungs

Vein from Head and Body

valve

II.Circulatory System Components

• Heart - divided into four chambers– right atrium, right ventricle, left atrium,

left ventricle

Heart Chambers and Valves

How does the Heart work?

blood from the body

blood from the lungs

The heart beat begins when the

heart muscles relax and blood

flows into the atria.

STEP ONE

The atria then contract and

the valves open to allow

blood

into the ventricles.

How does the Heart work?

STEP TWO

How does the Heart work?

The valves close to stop blood

flowing backwards.

The ventricles contract forcing

the blood to leave the heart.

At the same time, the atria are

relaxing and once again filling with

blood.The cycle then repeats itself.

STEP THREE

Right Heart Chambers: Pulmonary Circuit

• Right Atrium (forms most of posterior of heart)– Receives O2-poor

blood from body via IVC, SVC,

• Right Ventricle– Receives O2-poor

blood from right atrium through tricuspid valve

– Pumps blood to lungs via Pulmonary Semilunar Valve in pulmonary trunk

Left Heart Chambers: Systemic Circuit

• Left Atrium– Receives O2-rich blood

from 4 Pulmonary Veins

• Left Ventricle (forms apex of heart)– Receives blood from

Left Atrium via bicuspid valve

– Pumps blood into aorta via Aortic Semilunar Valve to body

Heart Valves: Lub*-Dub**• *Tricuspid Valve: Right AV valve

– 3 Cusps (flaps) made of endocardium and CT

– Flow of blood pushes cusps open– When ventricle in diastole (relaxed),

cusps hang limp in ventricle– Ventricular contraction increases

pressure and forces cusps closed• *Bicuspid (Mitral) Valve: Left AV

valve– 2 cusps anchored in Lft. Ventricle

by chordae tendinae– Functions same as Rt. AV valve

• **Semilunar valves: prevents backflow in large arteries– Pulmonary Semilunar Valve: Rt

Ventricle and Pulmonary Trunk– Aortic Semilunar Valve: Left

Ventricle and Aorta

blood from the heart gets around

the body through blood vessels

There are 3 types of blood vessels

a. ARTERY

b. VEIN

c. CAPILLARY

• Three types of blood vessels – arteries carry blood away

• thicker walls to withstand the pressure of blood being pumped from heart

– veins - toward heart• lower pressure• one-way valves to prevent blood from flowing

backwards away from heart

– capillaries • tiny links b/w arteries and veins where oxygen

and nutrients diffuse to body tissues• smallest of blood vessels, are only visible by

microscope ten capillaries lying side by side are barely as thick as a human hair.

The ARTERY

thick muscle and elastic fibres

Arteries carry blood Away from the heart.

the elastic fibres allow the artery to stretch under

pressure

the thick muscle can contract to push the blood

along.

The VEIN

Veins carry blood towards the heart.

thin muscle and elastic fibres

veins have valves which act to stop the blood from going in the wrong direction.

body muscles surround the veins so that when they contract to move the body, they also squeeze the veins and push the blood along the vessel.

The CAPILLARY

Capillaries link Arteries with Veins

the wall of a capillaryis only one cell thick

they exchange materials between the blood and other body cells.

The exchange of materials between the blood and the body can only occur through capillaries.

• Arteries, veins, and capillaries - divided into two systems:– Systemic - carries oxygenated blood from heart to

all tissues in body except lungs and returns deoxygenated blood carrying waste products, such as carbon dioxide, back to heart.

• oxygen-rich blood ejected under high pressure out of heart's main pumping chamber (L. ventricle) through largest artery (aorta) • smaller arteries branch off from aorta to various parts of the body• smaller arteries in turn branch out into even smaller arteries

(arterioles) • arterioles become progressively smaller eventually forming

capillaries - blood pressure is greatly reduced

• interstitial fluid fills the gaps between the cells of tissues or organs– dissolved oxygen and nutrients then enter the cells from interstitial fluid

by diffusion– carbon dioxide and other wastes leave the cell via interstitial fluid, cross

capillary walls, and enter blood. • after delivering oxygen to tissues and absorbing wastes,

deoxygenated blood in capillaries then starts the return trip to heart

• capillaries merge to form tiny veins, called venules• venules join together to form progressively larger

veins • veins converge into two large veins:

– inferior vena cava-brings blood from the lower half of body

– superior vena cava-brings blood from upper half– Both join at the right atrium of heart

FYI– Varicose Veins

• pressure is dissipated in arterioles and capillaries• blood in veins flows back to heart at very low pressure,

often running uphill when a person is standing• Flow against gravity allowed by one-way valves

– several centimeters apart in veins• Veins with defective valves (allow the blood to flow

backward) become enlarged or dilated to form varicose veins

Varicose veins

– Pulmonary Circulation• deoxygenated blood returning from organs and tissues travel

from R. atrium to R. ventricle. • pushed through pulmonary artery to lung• pulmonary artery divides forming pulmonary capillary region • microscopic vessels pass adjacent to alveoli (air sacs) - gases

are exchanged across thin membrane• oxygen crosses membrane into blood while carbon dioxide

leaves blood through same membrane• newly oxygenated blood then flows into pulmonary veins and is

collected by L. atrium of the heart (collecting pool for L.ventricle)

• contraction of L. ventricle sends blood into aortacompleting circulatory loop

L. LUNGR. LUNG

HEART

AORTIC ARCH

SUP. VENA CAVA

INF. VENA CAVA AORTA

PUL. ARTERY

PUL. VEINS

Artery/Vein differencesArteries (aa.) Veins (vv.)

Direction of flow

Blood Away from Heart

Blood to Heart

Pressure Higher Lower

Walls THICKER: Tunica media thicker than tunica externa

THINNER: Tunica externa thicker than tunica media

Lumen Smaller Larger

Valves No valves Valves (see next)

what’s in

red blood cells

white blood cells

platelets

plasma

carbon dioxide

digested food

waste (urea)

hormones

oxygen

The Blood

plasma

red blood cell

white blood cell

platelets

Red Blood Cells

contain haemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it.

can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries.

a biconcave disc that is round and flat without a nucleus

White Blood Cells

there are many different types and all contain a big nucleus.

the two main ones are the lymphocytes and the macrophages.

some lymphocytes fight disease by making antibodies to destroy invaders by dissolving them.

other lymphocytes make antitoxins to break down poisons.

macrophages ‘eat’ and digest micro-organisms .

`

PlateletsPlatelets are bits of cell broken off larger cells.

Platelets produce tiny fibrinogen fibres to form a net. This net traps other blood cells to form a blood clot.

Plasma

A straw-coloured liquid that carries the cells and the platelets which help blood clot.

• carbon dioxide

• glucose

• amino acids

• proteins

• minerals

• vitamins

• hormones

• waste materials like urea.

It also contains useful things like;

Heart Chambers and Valves