Objectives:* Describe one way flow of blood around the body.** Describe the structure and function of a heart*** Describe the cardiac cycle

Starter:1.What components make up the circulatory system?2. What are the substances carried by this system ? Name the route of each substance.

1.Blood, heart and blood vessels.

2. Oxygen from lungs to cells digested food from small intestine to cells CO2 from cells to lungs waste materials from cells to kidneys.

Double circulation• Like all mammals,

humans have a double circulation

• The right side of the heart sends blood to the lungs (pulmonary circulation)

• Blood returns from the lungs to the left side of the heart which pumps it into the systemic circulation supplying the rest of the body.

• Blood passes twice through the heart.

Double circulation• What is the

advantage of a double circulation?

Double circulation• A double circulation has the

advantage of providing all body organs with oxygenated blood at high pressure and at low pressure to the lungs as they are spongy tissue.

In the single circulation of a fish, blood is pumped

Heart

GillsOrgans

Most of the pressure generated by the heart is lost in the gills, and the organs receive low pressure oxygenated blood.

Pulmonary circulation

Systemic circulation

Double circulation• Double circulation is

made possible by the complete division of the heart into separate left and right sides

• The left side receives oxygenated blood(red) from the lungs, and pumps it to the systemic circulation; the right side receives deoxygenated blood (dark red) from the body, and pumps it to the lungs.

Heart

Body

Lungs

Blood circulation

The heart pumps blood to the blood vessels. Arteries take blood away from the heart to different organs and veins bring them back to the heart. The smallest blood vessels that connect arteries to veins are capillaries. The circulatory system allows one way blood flow. The capillaries has very thin walls so to reduce the pressure of blood flow small muscular blood vessels called arterioles receive the blood to reduce the pressure before blood enters capillaries.

Most arteries contain oxygenated blood and most vein deoxygenated blood but not all.

You can get instructions for a heart dissection here

• http://heartlab.robarts.ca/dissect/dissection.html

Structure of the heartThe diagram shows the heart at diastole – relaxed, between contractions.

Right atrium

Right ventricle

Left ventricle

Left atrium

Superior vena cava

Inferior vena cava

Pulmonary artery

Pulmonary veins

Aorta

Septum

Left atrio-ventricular valve (bicuspid valve)

Right atrio-ventricular valve (tricuspid valve)

Papillary muscle

Semilunar valves( has 3 pockets and half moon shaped)

Tendon

Remember your rt is the body’s left

The cardiac cycle

At diastole (0.4 s):

the heart muscle is relaxed;

the atrioventicular valves are open, and blood flows passively from atria into ventricles;

the semilunar valves are closed, because arterial pressure is higher than ventricular pressure.

At atrial systole (0.1 s):

the atria contract;

the vein openings are constricted, preventing backflow into the veins

blood is forced from atria into ventricles through the open atrioventicular valves;

the semilunar valves remain closed, because arterial pressure is still higher than ventricular pressure.

At ventricular systole (0.3 s):

the ventricles contract;

ventricular pressure rises above atrial, closing the atrioventicular valves;

ventricular pressure rises above arterial, opening the semilunar valves;

blood is forced from ventricles into the pulmonary artery and aorta.

Papillary muscles adjust tension in valve tendons

Animation of the cardiac cycle

Try to identify the three stages of the cardiac cycle in this animation.

Note which valves are open and closed at each stage.

The cardiac cycle1. Heart muscle relaxed; ________ valves open,

allowing blood flow from ________ to ________. Semilunar valves ________ to prevent backflow from ________ to ________.

2. ________ contract, opening ________ valves and forcing blood from ________ into ________ .

3. ________ contract, closing ________ valves and opening ________ valves: blood pumped from ________ into ________ .

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The Heart1. Deoxygenated blood (i.e. blood without oxygen) enters through the vena cava into the right atrium

2. It’s then pumped through the tricuspid valve into the right ventricle

3. It’s then pumped through the semi-lunar valve up to the lungs through the pulmonary artery

4. Oxygenated blood from the lungs enters through the pulmonary vein into the left atrium

5. It’s then pumped through the bicuspid valve into the left ventricle

6. It’s then pumped out of the aorta to the rest of the body

Blood Vessels

Objectives:

*Name blood vessels and describe their structure

** Explain how structures are related to their functions

*** Explain the role of valves in heart and blood vessels

Lesson 2: starter questions

1. Identify the stage of the cardiac cycle shown in the diagram. Give two reasons for your answer.

(3 marks)

2. Identify the blood vessels labelled A, B and C.

(3 marks)

3. Explain the difference in thickness of the muscular wall at X and Y.

(2 marks)

AB

C

X

Y

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The Circulatory systemThe circulatory system is responsible for pumping ______ around the body. We need blood to be taken around the body because blood contains ________ and _______. These are needed so that all the ____ in our bodies can produce _____ through _________.

The main organs in the circulatory system are the _____, the lungs and the kidneys.

Words – energy, heart, blood, glucose, respiration, oxygen, cells

Blood vessels

• Arteries carry blood from the heart towards capillary beds, veins carry blood from capillary beds towards the heart

• Arteries do not always carry oxygenated blood, nor veins deoxygenated: the pulmonary and umbilical arteries carry deoxygenated blood, the pulmonary and umbilical veins oxygenated blood

ArteriesArteries characteristically have:

a narrow lumen, maintaining high pressure

a thick wall to withstand high pressure

a corrugated inner lining (endothelium), allowing stretching during systole

extensive elastic tissue, which absorbs some of the energy given to the blood at systole and then returns it by recoiling during diastole

muscle fibres, allowing the artery to be constricted or dilated to control the amount of blood flowing through it (NB this muscle does not propel the blood)

VeinsVeins characteristically have:

a wide lumen, giving minimum resistance to low pressure flow

a smooth endothelium, again giving minimum resistance

little elastic or muscular tissue

valves to prevent backflow of low pressure blood

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Arteries, veins and capillariesArteries carry high pressure blood away

from the heart. They have smaller lumen and no valves.

Veins carry low pressure blood back to the heart. They have thinner, less elastic walls and have valves to prevent backflow of

blood.

Capillaries have thin walls (one cell thick) to allow glucose and oxygen to pass through. Also used to connect

arteries to veins.

“Lumen”

Animation of the cardiac cycle

Try to identify the three stages of the cardiac cycle in this animation.

Note which valves are open and closed at each stage.

Action of valves in veins

Looking at valves in veinsTry this simple experiment to show valves in the veins of your hand. Hold your arm down by your side. This helps to fill the veins in your hand with blood and make them easier to see.Find the vein shown in the picture that runs down the middle of the back of your hand.With your other hand, gently press your index finger onto the top of the vein and push it downwards, towards your knuckles. This forces the blood in the vein against the direction it normally flows.

Notice that the vein does not fill up with blood from higher in your arm. This is because the vein contains a valve by your wrist. This valve prevents blood from the section of vein higher up in your arm from flowing back down and refilling the section of the vein in your hand.When you stop pressing with your finger the vein refills with blood flowing from your fingers.

Arteries, capillaries and veins

As arteries branch and become smaller, their muscle and elastic layers are reduced.

Arterioles still have muscle and a nerve supply, and control the blood supply to capillary beds

Capillaries have no muscle or nerve supply, only a single cell layer (the endothelium)

As capillaries rejoin they form venules, which reunite to form veins

Capillary structureThe capillary wall is a single layer of very flat cells.

It is highly permeable, with gaps between cells and holes through cells: capillary beds are where exchange occurs between blood and tissues.

The lumen of a capillary is about 5 m in diameter: red blood cells (diameter 7 m) pass through in single file, squashed against the capillary wall.

Nucleus of squamous epithelial cell

Capillary lumen

Red blood cell

Basement membrane of squamous epithelial cell – allows small molecules through, keeps plasma proteins in

Name the most important arteries and veins

Vessel O R G A N S

Heart Lungs Liver Kidneys

Bringing blood to organ

Taking blood away from organ

Vena cava to rt atrium pulmonary vein to lt atrium

From rt ventricle to pulmonary artery from lt ventricle to aorta

pulmonary artery

pulmonary vein

Hepatic artery, hepatic portal vein

Hepatic vein

Renal artery

Renal vein

Coronary Heart Disease(CHD)

Objectives:* State and explain the effect of physical activity on pulse rate**Describe the nature of coronary heart disease***Describe the possible causes and preventative measures of CHD

Practice questions1. Identify the type of blood

vessel shown and give two reasons for your answer.

(3 marks)

2. Name two kinds of tissue you would expect to find in the layer labelled X, and state one function for each.

(2 marks)

The micrograph shows a blood vessel in transverse section

X

Investigating pulse rate( the number of pulse beat /min=heart rate)

1. Sit still and get you partner to measure you pulse rate2. Try doing step ups for 1 min (light exercise)and sit down and count the

pulse rate again.3. Wait till your pulse rate comes to the resting rate4. Do step ups for 3 mins (heavy exercise) and sit down and count the

pulse rate again.5. You can repeat and calculate an average but wait for 5 mins before

each repeat.6. Ensure the same person is doing the exercise.7. Explain your results in terms of supplying substances to your muscles

and removing the wastes.

During exercise your muscle needs more energy from respiration to contract. Do heart beats faster and arteries supplying muscles dilate. These increase the blood flow to muscles resulting in:1.An increase in supply of oxygen and glucose2.An increase in removal of carbondioxide

Coronary circulation

The muscular wall atria and ventricles of the heart is provided with high-pressure oxygenated blood by the coronary arteries, arising from the base of the aorta just above the semilunar valves.

Aorta

Slow FlowHealthy arteries has smooth lining letting the blood flow easily. However c………… which is made in the liver can stick to the wall making it n……….. Which will slow down the flow. This condition is known as atherosclerosis. The artery walls can become rough which can cause the blood to c……… and block the vessel. The blockage is called thrombosis.

These conditions can cause chest pains especially when the heart is working hard. This condition is called angina when enough o………… does not get to the heart muscle. Angina or thrombosis can lead to a heart attack. Parts of the heart can be damaged or it may stop beating altogether causing cardiac arrest.

Risk fcatorsFactors that can be avoided:1. Diet with too much saturated (animal)fat increases concentration of cholesterol in the blood.2. Overweight3.Smoking4.Taking little or no exercise5. Stress

Factors cannot be avoided:1.Genes that control the metabolism of fat and cholesterol2.Age increases with age3.Sex men are more likely than women

Taking care

1.Diet – Eat more poultry and fish fresh fruit and vegetables. Cut down on fried foods, red meat.

2.Take regular exercise

3.Do not smoke