Transport in Animals

Module One: Life Processes in Plants and Animals

Paper Two

• Circulation in animals is important as it ensures that everything is working properly.

• Vital substances (e.g. water, oxygen, CO2, nutrients, waste, hormones) have to move about within the body.

• In simpler animals, the body is small enough for substances to diffuse from cell to cell.

• In larger, multicellular organisms, the body is too thick for diffusion to take place. Thus a circulatory system needs to collect various substances and distribute them throughout the body.

Overview

Characteristics:1. Blood – to transport dissolved gases, nutrients and waste

products around the body2. Blood vessels – in which the blood flows around the body3. Heart – pumps blood around the body4. Valves – ensure blood pumps in only one direction

Two types of circulatory systems:• Open• Closed

Circulatory Systems

• Found in invertebrate groups, including crustaceans, snails and insects

• Blood pumped at a low pressure into the body cavity – the haemocoel.

• Blood bathes organs directly and moves slowly through tissue returning to the heart by means of collecting ducts.

• This is quite inefficient, and only suitable for small organisms.

Open Circulatory System

• Found in larger animals such as segmented worms, sea urchins and all vertebrates

• The blood remains enclosed and circulates in a system of tubes called blood vessels.

• There is a separate fluid – tissue fluid – found between blood vessels and cells.

• Very effective transport system. It allows blood to travel rapidly under high pressure to wherever it is needed.

Closed Circulatory System

• We have a closed circulatory system, called the cardiovascular system (cardio = heart; vascular = blood vessels).

• The blood flows to the most distant parts of the body & back to the heart.

• The human circulatory system is a double system. The heart consists of two pumps sitting alongside one another.– The right side pumps blood to the lungs, which returns to the left side

of the heart.– The left side pumps blood to the rest of the body, which returns to the

right side of the heart.

• Blood thus flows through two distinct circulations – the pulmonary and the systemic.

Human Circulatory System

• In the pulmonary circulatory system, blood that is deoxygenated and high in carbon dioxide flows from the right side of the heart to the lungs. In the capillaries of the lungs, this blood takes in oxygen and gives off carbon dioxide. Oxygenated blood then flows from the lungs to the left side of the heart.

• In the systemic circulatory system oxygenated blood is carried from the left heart to all cells of the body. In the capillaries of body tissues, nutrients and gases are exchanged between blood and cells. This blood is deoxygenated – it then flows to the right side of the heart.

Human Circulatory System

• In the pulmonary system, gaseous exchange takes place to gather oxygen and eliminate carbon dioxide.

• In the systemic system, blood is pumped under pressure to all parts of the body to supply oxygen and nutrients and take up carbon dioxide and other waste. Blood under pressure allows:– Tissue fluid to form when blood plasma is pushed out the capillaries.

The tissue fluid is the medium through which substances move between the blood and cells.

– Oxygen to be carried quickly to all body cells for cellular respiration. This releases energy and heat.

Human Circulatory System

Double Circulatory System

The Heart• The heart is a pump that applies pressure to force blood

around the body. • It is situated in the middle of the chest thorax in a hollow

space called the mediastinum. It is protected by the ribs and sternum.

The Heart Externally

• It is surrounded by pericardium, made up of two inelastic membranes, one attached to the heart itself. Fluid is secreted between these membranes, allowing them to move easily over each other, preventing friction as the heart beats.

• Coronary arteries are visible. These supply nutrients and oxygen to the heart tissue itself. Blockage of these vessels may cause death of some of the heart muscle – resulting in a heart attack (a.k.a a myocardial infarction or coronary thrombosis). It can cause death.

• The heart may have deposits of fat.

The Heart Externally

aorta

pulmonary veins

superior vena cava

coronary artery

coronary vein

inferior vena cava

• The heart is divided into four chambers.

The Heart Internally

Right Atria* Left Atria

Right Ventricle Left Ventricle

• Atria are small and thin walled. They receive blood and push it into the ventricles.

• Ventricles have thick walls of muscle, which contract and push blood out of the heart. The left has a particularly thick wall because it must pump blood to the whole body.

• The myocardium is the layer of the heart wall made of a special tissue called cardiac muscle. This type of muscle is unique as it can pump rhythmically over and over again without getting tired.

• The right and left sides are divided by the septum.• The heart is lined with a smooth membrane, the endocardium.• The ventricles have ‘bumps’, papillary muscles, from which

tendinous chords extend.

The Heart Chambers

Two sets of valves are found in the heart. They ensure the blood flows in one direction.1. The atrioventricular valves (AV valves) are found between

the atria and ventricles.– The valve between the left atrium and left ventricle is made up of

two flaps. It is called the bicuspid mitral valve.– The valve between the right atrium and the right ventricle is made

up of 3 flaps. It is called the tricuspid valve.– They only allow blood to flow from the atria to the ventricles.– Tendonous chords anchor them and prevent them from being

pushed inside out by the great pressure when the ventricles contract.

The Heart Valves

2. Semilunar valves are found at the base of the pulmonary artery and the aorta.

– They are called the pulmonary and aortic valves respectively.– Made up of 3, half-moon-shaped membranous flaps (cusps), attached

to the internal wall of the blood vessels– As the ventricles contract, the flaps are flattened against the wall,

allowing blood to flow from the ventricles into the blood vessels.– As the ventricles relax, the flaps close under pressure of the blood

which is trying to flow backwards.

In the heartbeat, we hear ‘lub dup’. The lub is caused by the closing of the AV valves. It is the louder, longer sound. The dup is short and sharp and is caused by the closing of the semilunar valves.

The Heart Valves

septum

pulmonary artery

pulmonary veins

left atria

aortic semilunar valve

mitral bicuspid valve

tendinous chords

papillary muscle

endocardium

right ventricle

superior vena cava

aorta

pulmonary semilunar valve

tricuspid valve

tendinous chords

inferior vena cava

• The human heart beats about 70 times per minute. The cardiac cycle includes all the events that take place as the blood flows through the heart during one complete heartbeat.

• When the cardiac muscle contracts, pressure within the heart increases and blood is forced out. This is called ‘systole’.

• When the cardiac muscle relaxes, pressure within the heart decreases. This allows blood to flow into the atria and ventricles.

The Cardiac Cycle

• During this phase, the atria relax.• Blood will come in from the superior vena cava, inferior vena

cava and pulmonary veins, and will fill the atria.• The AV valves will open and the semilunar valves close.

Atrial Diastole

• During this phase, the ventricles relax.• The AV valves open due to the ventricles relaxing.• Blood from the atria are able to flow into the ventricles.• The semilunar valves remain closed.

Ventricular Diastole

• In this phase, the atria contract.• This forces blood from the atria into the ventricles. • The ventricles bulge.• The AV valves open and the semilunar valves close.

Atrial Systole (0.1 sec)

• In this phase the ventricles contract.• Deoxygenated blood from the RV is forced up the pulmonary

artery to the lungs.• Oxygenated blood is carried to the body from the aorta.• The AV valves are closed and the semilunar valves are open.

Ventricular Systole (0.3 s)

1) All muscles relax

2) Blood flows into heart

3) Semilunar valves close

4) AV valves open5) Atrial muscles contract

6) Blood passes AV valves7) Blood enters ventricles

8) Muscles of ventricles contract

9) AV valves open

10) Semilunar valves open

11) Blood enters aorta and pulmonary artery

GENERAL DIASTOLE (0.4 SEC)

ATRIAL SYSTOLE (0.1 SEC)

VENTRICULAR SYSTOLE(0.3 SEC)

Cardiac Cycle

• Most muscles rely on nerve impulses to cause them to contract. Heart muscle, however, is myogenic – i.e. its contractions arise from within the muscle tissue itself.

• Embedded in the wall of the right atrium is the sino-atrial node or SA node. This generates the heartbeat by sending out tiny electrical impulses.

• These impulses stimulate another special patch of tissue, the atrioventricular node or AV node in the lower, left hand corner of the right atrium.

• This eventually causes the contractions.• The heartbeat is also controlled chemically by a hormone called

epinephrine, or adrenaline, which increases the heartbeat during times of stress.

How the Heart Beats

SA Node

AV Node

• Increased levels of CO2 in bloodDuring exercise, CO2 in blood increases. This results in an increase in the cardiac rate so that carbon dioxide-rich blood is taken quickly to the lungs to be oxygenated.

• Increased venous return to the heartDuring exercise, blood vessels passing through the exercising muscles relax and dilate so as to carry more blood, therefore more blood flows back into the heart. The increased blood causes the SA node to be stimulated, thus increasing the cardiac rate. The blood is able to be pumped out quickly.

How Exercise Affects The Heart

• The pulse is the rate of contraction and expansion of an artery as blood is pumped through the body.

• As the heart contracts, blood is pumped into the aorta and the aorta stretches. The pulse wave passes along the walls of the aorta and into similar arteries.

Pulse

There are essentially three types of blood vessels: arteries, veins and capillaries.• Arteries take blood away from the heart• Veins carry blood towards the heart• Capillaries connect the arterial and venous systems and are

sites of exchange between the blood and tissues.As the heart contracts, blood is forced into the large arteries. The arteries branch into narrower vessels, finally reaching the capillaries. These form venules, which form veins, which return blood to the heart.

Blood Vessels

Blood Vessels

The vessel walls are essentially made up of three distinct layers surrounding a lumen. • A single inner layer of squamous endothelial* cells forms a

smooth surface that reduced friction, so that blood moves through the vessels unhindered.

• A middle layer of circularly arranged smooth muscle cells and elastic fibres. These control the diameter of the lumen according to how much blood needs to be pumped through the body.

• An outer layer of inelastic collagen fibres strengthen the vessels.

Structure of Blood Vessels

• Located deep inside the body.• Functions:

– Carry oxygenated blood away from the heart to the tissues– Act as pressure reservoirs – they keep blood moving during diastole.– Arteries and arterioles control the distribution of blood to the venous organs

by vasoconstriction and vasodilation.

• Structure:

Arteries

• Functions:– Carry deoxygenated blood to the heart from the tissues.

• Structure:– Have thin walls with a small amount of muscle tissue. They are thus

floppy with an irregular lumen.– In large veins, e.g. in legs, semilunar valves may be present.

Veins

• Functions:– Diffusion of substances between blood and body cells.– The pores allow for phagocytes to move in and out of the vessel wall.

• Structure:

Capillaries

Adaptations of Blood Vessels

• Arteries– Are not found at the surface of the body as they must be protected,

and because they must regulate body temperature.– Have a thick muscle layer to pump consistent measures of blood at a

high pressure.

• Veins – Have an irregular shape as they pump inconsistent measures of blood.

• Capillaries– Have thin walls to reduce size and allow for easy diffusion of

substances.– Pores allow for white blood cells to move in and out of capillaries.

• Blood pressure is the force exerted by blood against the walls of blood vessels.

• The factors that maintain blood pressure are:– Pumping of the heart– Narrowness of the smaller arterioles which causes peripheral

resistance to the flow of blood.

• Blood pressure in the arteries will rise and fall. – It increases due to the contractions of the ventricle (systole).– It decreases during the relaxing of heart muscle (diastole).

Blood Pressure

Systolic Blood Pressure• This refers to the maximum pressure reached in the aorta

when the ventricles contract.• The average in a healthy adult is 120mm Hg.Diastolic Blood Pressure• This refers to the lower pressure in the aorta when the

ventricles relax. • In diastole, blood is kept pumping by elastic blood vessels.• The average in a healthy adult is 80mm Hg.

Blood Pressure

• A steady pressure of blood flow ensures that cells are constantly receiving the correct amount of nutrients, oxygen, etc.

• Blood pressure in capillaries is lower than in the arterioles. This is important because:– Diffusion can thus take place slowly.– The thin walls would rupture under high pressure.

• Blood is measured with a baumanometer or electronically. The first number is the systolic BP and the second is the diastolic BP. It is recorded with the systolic over the diastolic, e.g. 120/80 mm Hg.

Blood Pressure

Blood Vessel Function

Aorta Oxygenated blood from the heart to body tissues

Carotid Artery (left) Oxygenated blood from the heart to the head

Pulmonary Artery Deoxygenated blood from the heart to the lungs

Hepatic Artery Oxygenated blood from the heart to the liver

Femoral Artery Oxygenated blood from the heart to the legs

Subclavian Artery (right) Oxygenated blood from the heart to the right arm

Renal Artery Oxygenated blood from the heart to the kidneys

The Main Arteries

The Main VeinsBlood Vessel Function

Renal Vein Deoxygenated blood from the kidneys to the heart

Femoral Vein Deoxygenated blood from the legs to the heart

Hepatic Vein Deoxygenated blood from the liver to the heart

Hepatic Portal Vein Deoxygenated blood from the gut to the liver

Inferior Vena Cava Deoxygenated blood from the lower body to the heart

Subclavian Vein (left) Deoxygenated blood from the left arm to the heart

Pulmonary Vein Oxygenated blood from the lungs to the heart

Jugular Vein Deoxygenated blood from the head to the heart

Superior Vena Cava Deoxygenated blood from the upper body to the heart

The function of blood is to transport nutrients to all body organs and tissues and carry away waste materials. An adult body contains about 5 litres of blood.It contains:• 45% blood cells including

– Red blood cells– White blood cells– Platelets

• 55% plasma consisting of– 91% water– 7% proteins– 2% other substances

Blood as a Tissue

It is a watery, straw-coloured liquid which contains:• dissolved substances like nutrients, waste materials, ions,

hormones and gases• Plasma proteins, including

– Fibrinogen (for blood clotting)– Albumen (creates the blood’s osmotic pressure)– Antibodies (to destroy germs)

Plasma transports:• Blood cells, nutrients, antibodies, CO2, urea, hormones, heat

and blood clotting factors.

Plasma

• Platelets– Smallest blood cells. They appear round but can have hair-like

filaments on their surface.– Make blood clotting occur.

• White blood cells– They are created in the spleen, lymph glands and in red bone marrow.– They are large and irregular in shape.– Fight against disease – e.g. phagocytes and lymphocytes.

• Red blood cells– Are biconcave disk-shaped cells which contain haemoglobin. – They have no nucleus and few organelles.– Their main function is to transport oxygen, but can also contain a

small amount of carbon dioxide.

Blood Cells

• Consists of lymphatic vessels, lymph nodes and other lymphoid organs and tissues, e.g. tonsils, thymus, spleen and areas in the gastrointestinal tract. These parts all contain lymph.

• The fluid lymph consists of water, solutes (of protien, salts, glucose, urea) and white blood cells. The white blood cells include:– Lymphocytes (also found in blood), including B- and T-lymphocytes. – Macrophages which trap and digest pathogens by phagocytosis.

• This is why lymph glands swell when one has an infection.

The Lymphatic System

Functions:• Helps maintain fluid balance by collecting excess tissue fluid in

the body and depositing it into the bloodstream.• Defends the body against infection with its blood cells.• Transports absorbed fat to the blood stream.Relationship between Blood and Lymph System:• The lymph system is a subsystem of the circulatory system.• Lymph is formed when blood plasma seeps out of blood

capillaries, bathes the body cells and seeps into the lymph system. It then re-enters the blood stream in the subclavian veins, near the heart.

The Lymphatic System

Blood transfusion is the transfer of blood from a donor to a recipient. It is highly effective, and used to:• Restore blood or plasma after extensive haemorrhage or

burns.• To increase the number of red blood cells in persons with

anaemia.A donor’s blood must be examined to:• Make sure that it does not contain pathogens e.g. HIV.• Find out its blood groups – incompatible combinations

result in agglutination.

Blood Transfusion

• There are four major blood groups: A, B, AB and O.• They are based on antigens, or agglutinogens found on the

surface of the red blood cells.– Blood group A has A antigens– Blood group B has B antigens– Blood group AB has AB antigens– Blood group O has no antigens

• The groups also have antibodies in the plasma. Clumping occurs when the antibody of the donors blood matches the antigen of the recipients blood. The blood cells agglutinate and can block a person’s blood vessels and become fatal.

Blood Groups

Blood Group RBC antigens Illustration Plasma antibodies

Blood that can be received

AB A and B None A, B, AB, O

A A Anti-B A, O

B B Anti-A B, O

O O Anti-A and B O

Blood Groups

• Blood has an abnormally low oxygen-carrying capacity.• Symptoms are: tiredness, shortness of breath, being pale and

being cold.• People become anaemic when:

– There is a shortage of substances needed by the bone marrow to make red blood cells. If iron is missing, it is called iron-deficiency anaemia. The sufferer needs to have iron-rich vegetables

– Disease in the mone marrow, e.g. if the bone marrow is damaged during chemo.

– Excessive breakdown of red blood cells, e.g. by malaria.– Blood loss, e.g. by heavy menstrual periods, traumas and intestinal

damage in children.

Blood Disorders: Anaemia

• Makes the white blood cells become enlarged and abnormal.• The infected person will thus be prone to infections and

fevers.• Leukaemia causes less red blood cells and platelets to be

made, while more white blood cells are created. Thus, the sufferers are tired and bleed and bruise easily.

• Treatment:– Chemotherapy: cancer cells destroyed by drugs.– Radiotherapy: cancer cells stopped from growing and multiplying by

high energy rays like X-rays.– Biological therapy: i.e. a bone marrow transplant.

Blood Disorders: Leukaemia

• Very high blood pressure: 140/90 or higher.• Can lead to:

– a stroke (blood vessel ruptures in brain due to pressure)– heart failure (as the heart is forced to work harder)– brain and kidney damage (tears in blood vessels reduce blood flow to

brain and/or kidney).

• Those most at risk:– Smokers– The obese– Type 2 diabetes sufferers– Emotionally stressed persons– The sedentary

Blood Disorders: Hypertension

• Other factors:– Increasing age, i.e. being over 40– Hereditarily predisposed– Kidney disease

• Treatment:– An improved lifestyle– Anti-hypertensive drugs

Blood Disorders: Hypertension

• Low blood pressure, systolic blood pressure under 100 mm Hg.

• This is often associated with long life and an old age free of illness.

Blood Disorders: Hypotension

• A heart attack occurs when the coronary artery taking blood to the cardiac muscle is cut or blocked.

• The muscle is starved of nutrients and oxygen, and death of tissue may occur. It may kill someone within a few minutes.

• It occurs when a plaque (collection of cholesterol molecules) forms when cholesterol molecules slip below the endothelium of the coronary arteries.

• If the plaques burst, blood clots form and block the flow of blood to the heart.

• Inflammation cause the plaques to burst easily.

Circulatory Problems: Coronary Artery

Disease

• Risk factors that can be controlled:– High BP or blood cholesterol– Smoke cigarettes– Obesity– Type-2 diabetes– Environmental stress– Sedentary lifestyle– Diet high in sugars and fats and low in vegetables

• Risk factors that can’t be controlled:– Being male– Middle-aged– Having a high-achiever personality– Being hereditarily predisposed to this condition

Circulatory Problems: Coronary

Artery Disease

Coronary artery bypass:• Most common treatment.• A section of a vein without valves, often in the leg, is grafted onto

the coronary artery so that blood can bypass the blocked area.Coronary angioplasty:• Involves using tiny balloons surrounded by a metal stent (wire

spring) to open up the blocked artery. The stent and deflated balloon is put onto the end of a long tube and inserted into the femoral artery, up the aorta and into the coronary artery.

• Once in position, the balloon is inflated to open the artery, so that blood can flow freely. The stent remains in the blood vessel wall so that the artery stays open.

Circulatory Problems: Coronary

Artery Disease

A stroke is a brain attack or cerebro-vascular accident. A thrombosis or a haemmorhage could cause a stroke. There are many different kinds of strokes:• A thrombosis in a brain artery

– Similar to a heart attack, but in the brain. Brain cells get cut off from oxygenated blood and die out.

– Symptoms include: paralysis of the limbs on one side of the body, difficulties with speech and/or swallowing, visual field disturbances and unconciousness.

• Sudden rupture of blood vessel in brain– Can cause sudden death if it occurs in the medulla oblongata area. Brain

cells are killed rapidly. – Symptoms can be the same as in cerebral thrombosis.

Circulatory Problems: Stroke

• Rupture of blood vessel inside the skull but outside the brain– Pressure against the brain will build up quickly and cause a sudden,

severe headache. – The pressure can result in the death of brain cells.– The result will depend on the amount of bleeding and the position of

the rupture in the skull.

Angina• This is a chest pain due to certain areas of the cardiac muscle

receiving insufficient blood.

Circulatory Problems: Stroke