Transport Systems in Mammals

Re-purposed by Trischa Pretorius

Why are Transport Systems Needed?

• Many invertebrates rely on diffusion to supply its cells with oxygen. However diffusion is only efficient over short distances.• In large animals such as humans

more oxygen are required for respiration in our muscles and so we need a more effective way of delivering large quantities of oxygen quickly – hence our circulatory system.

The Types of Circulatory System

Open Circulatory system (as seen in insects)

Closed circulatory system (as seen in worms)

Open Circulatory System

• In an open circulatory system the blood enters and circulates in the interstitial spaces (spaces between the tissues).• The exchange of materials between the cells and the blood is done directly. • There are few blood vessels but they are not extensive.

• The blood vessels are open-ended as they open into the common cavities called the haemocoel.

Closed Circulatory System

• In a closed circulatory system the blood always remains inside the blood vessels and never comes in direct contact with the cells. • The materials enter and exit the blood

vessels through the walls. • The blood flows in the blood vessels under high pressure such that it reaches all the parts of the body in good time. • The blood vessels are branched into fine capillaries which are actually involved in the exchange of materials.

Double Circulatory System

• In a double circulatory system, blood travels in two circuits around the body.

•Pulmonary circuit: Deoxygenated blood travels from the heart to the lungs where it gains oxygen and returns to the heart.

•Systemic circuit: Oxygenated blood travels from the heart to all parts of the body and back to the heart

Blood passes through heart TWICE per complete circuit

• Blood returning to the heart is low in oxygen and high in carbon dioxide.• This blood is said to be deoxygenated.

• Blood leaving the heart is high in oxygen and low in carbon dioxide• This blood is said to be oxygenated.

Oxygenated and deoxygenated blood

Different types of blood vessels

• Arteries• Veins• Capillaries

Arteries

• Arteries carries blood away from the heart, and towards organs.

• Blood travels at high pressure and is usually oxygenated.• The artery has thick muscular walls to

withstand the high pressure.• Some major arteries are:

AortaPulmonary ArteryHepatic ArteryRenal Artery

Veins

• Veins take blood to the heart and away from organs.

• Blood travels at low pressure therefore veins have valves to prevent blood going backwards - if the blood goes backwards (i.e. towards the valves) this will cause them to close and thus preventing further movement.• The blood inside veins is usually deoxygenated.

Veins

• Some major veins are:Vena CavaPulmonary ArteryHepatic Portal VeinRenal Vein

Capillaries

• Capillaries are microscopic vessels that connect arterioles to venules.• Walls are only 1 cell thick and allow substances to be exchanged between blood and body cells.

The Heart and Associated Blood Vessels

• The heart consists of 4 chambers.• The upper chambers receive blood

and are called atria.• The lower chambers pump blood out of the heart and are called ventricles.

• There are valves situated between the chambers and at the points where blood leaves the heart.• Valves are present to ensure that

blood only travels in one direction.

The Heart and Associated Blood Vessels• Between the atria and the ventricles are atrioventricular valves, which prevent back-flow of blood from the ventricles to the atria. • The left valve has two flaps and is called the bicuspid (or mitral) valve, while the right valve has 3 flaps and is called the tricuspid valve. • The valves are held in place by valve tendons (“heart strings”) attached to papillary muscles, which contract at the same time as the ventricles, holding the valves closed.

The Heart and Associated Blood Vessels

There are also two semi-lunar valves in the arteries (the only examples of valves in arteries) called the pulmonary and aortic valves. These valves prevent the blood flowing back to the ventricles.

When the blood reaches the alveoli, oxygen diffuses into the blood and carbon dioxide diffuses

into the alveoli.

1

6

5

4

3

2

7

1

23

4

5

6

7

Blood travels in the pulmonary artery to the lungs.

The right ventricle contracts and forces blood through the

pulmonary valve.

Blood enters the right ventricle.

The right atrium contracts and forces blood through the tricuspid

valve.

Blood enters the right atrium.

Blood returns back to the heart through the vena cava.

The Heart and Associated Blood Vessels

8

13

12

11

10

9

14

1

23

4

5

6

7

When the blood reaches the body cells, oxygen diffuses into the cells and carbon dioxide diffuses into

the blood.

Blood travels in the aorta to the body.

The left ventricle contracts and forces blood through the aortic

valve.

Blood enters the left ventricle.

The left atrium contracts and forces blood through the bicuspid valve.

Blood enters the left atrium.

Blood returns back to the heart through the pulmonary vein.

8

91011

12

13

14

The Heart and Associated Blood Vessels

The External Structure of the Human Heart

The Internal Structure of the Human Heart

(Bicuspid valve)

Blood Flow through the Heart

Cardiac Cycle

• There is a sequence of events at each heartbeat called the cardiac cycle.• There are two phases – contraction (systole) and relaxation (diastole). Blood enters the atria from the veins. • Contraction of the muscles of the atrial wall forces blood into the ventricles.• Blood is pumped out of the heart by contraction of the ventricle muscles.

Cardiac Cycle

• Contraction of the atrial muscles is called atrial systole.• Contraction of the ventricular muscles

is called ventricular systole.• Relaxation of the heart muscle is

called diastole.• The pulse is a pressure wave

caused by contraction of the left ventricle.

Cardiac Cycle

Cardiac Cycle: Electrocardiogram (ECG)

Electrodes are placed on the skin over opposite sides of the heart, and the electrical potentials generated recorded with time. The result is an ECG.P wave = electrical activity

during atrial systole

QRS complex = electrical activity during ventricular systole

T wave = ventricular repolaristion (recovery of ventricular walls)

Q-T interval – contraction time (ventricles contracting)

T-P interval – filling time – ventricles relaxed and filling with blood

3) The impulse is passed from the AV node down the bundle of His. The bundle of

His fibres as inside the septum. They take the

electrical impulse down to the apex of the heart. The bundle of His fibres are insulated so the ventricles don’t start to

contract.

4) The Purkinje fibres make the left and right ventricles

contract. The electrical impulses travel UP the Purkinje

fibres from the apex of the heart. This makes the ventricles

contract from the apex of the heart. This squeezes blood UP

and out of the heart.

2) The electrical impulse reaches the AV node. The

AV node delays the electrical impulse. This is to give enough time for all of the blood to move from the

atria into the ventricles.

1) The SA Node = ‘Pacemaker’ The SA node gives off an

electrical impulse that causes the left and right

atrium to contract.

Controlling the cardiac cycle

1

2

344

Summary of events during the cardiac cycle

Lymphatic System

• Most tissue fluid is returned to the blood plasma via the capillaries. • Remaining tissue fluid enters the lymph vessels – drain back into the veins close to the heart.

• This fluid is now called lymph.• Lymph nodes filter lymph and play an

important role in the body’s defence.

Lymphatic System

Diseases of the Heart and Circulatory System• Cardiovascular Diseases are caused by a build-

up of cholesterol fibres, dead muscle cells and platelets on the inside of the coronary artery, called an atheroma which reduces the flow of blood and therefore oxygen to the tissues.

Diseases of the Heart and Circulatory System

• If the atheroma breaks through the endothelium (cells lining the inside of the artery) it forms a rough surface that interrupts the smooth flow of blood. This may result in formation of a blood clot or thrombus.

• This is known as thrombosis. The thrombus may block the blood vessel reducing or preventing blood supply to the tissues (cardiac muscle).

Diseases of the Heart and Circulatory System• The plaque weakens the

wall of the artery. The weakened points swell to form a balloon-like structure called an aneurysm. • If the wall is particularly

weak it may burst causing a haemorrhage or blood loss and possibly death.

Diseases of the Heart and Circulatory System

• Any cardiac cells that are supplied by this blood vessel will be starved of oxygen and glucose and therefore cannot respire.

• These cells will die – this is called a myocardial infarction or heart attack.

Diseases of the Heart and Circulatory System

• A stroke occurs if an artery in the brain bursts and blood leaks into the brain tissue or when an artery supplying the brain becomes blocked.

• The brain tissue becomes starved of oxygen and dies. Strokes can be fatal or very mild and may affect speech, memory and control of the body.

Diseases of the Heart and Circulatory System• High blood pressure increases the risk of an aneurysm and stimulates thickening of artery walls, increasing the risk of thrombosis. • Prolonged stress, diet and lack of exercise can

all increase blood pressure.• High blood pressure increases the risk of heart disease because: Higher pressure in arteries means the heart

has to work harder to pump blood into them – therefore increases risk of failure.

To resist higher pressure the walls of the arteries thicken, which restricts the blood flow.

Re-purposed from

Circulatory System of a Mammal. Retrieved 3 April, from http://www.tes.co.uk/teaching-resource/Circulation-Blood-Vessels-and-Tissue-Fluid-6070763/

Controlling the Heartbeat. Retrieved 3 April, from http://www.tes.co.uk/teaching-resource/Controlling-the-heartbeat-ELSS-Biology-6412761/

Heart and Heart Diseases. Retrieved 3 April, 2014, from http://www.tes.co.uk/teaching-resource/AQA-3-1-5-AS-Biology-Heart-and-amp-Heart-Diseases-6380648/

The Circulatory System. Retrieved 3 April, 2014, from http://www.tes.co.uk/teaching-resource/The-Circulatory-System-6345574/

Transport in Animals. Retrieved 3 April, 2014, from http://www.tes.co.uk/teaching-resource/Transport-in-Animals-6400934/