Human Circulatory System Heart and Blood Vessels

Contents In single celled organisms In small multicellular organisms Circulatory system Types of Circulatory System The Human Circulatory System Blood vessels Exchange of materials Portal blood system The Heart Valves in heart Systole & Diastole Heartbeat Blood Pressure Healthy Circulatory System The Lymphatic System Blood and Lymph vessels – diagram Lymph System Composition The Lymph System Lymph nodes Functions of the Lymph System

In single celled organisms All cells need to take in various nutrients e.g. oxygen All cells need to get rid of waste products e.g. carbon dioxide Single celled organisms e.g. Amoeba, achieve this by diffusion

Exchange of materials in Amoeba

In small multicellular organisms Small multicellular organisms e.g. flatworms have bodies only a few cells thick They too can exchange materials with their environment by diffusion

Exchange of materials in a flatworm

Circulatory system Larger multicellular animals need a circulatory system as the distance from the body surface to the centre is too great for diffusion A circulatory system consists of: - A fluid called blood A pump called a heart Tubes or vessels to carry the blood to the cells of the body

Types of Circulatory System Two types Open Circulatory System Closed Circulatory System

Open Circulatory System Blood not always found in blood vessels Heart pumps blood into open ended vessels and into body cavity Body cells bathed in blood – exchange of materials takes place Blood passes back into blood vessels and back to heart This type of circulatory system is found in insects

Open circulatory system Go to Slide 58

Closed Circulatory System Blood remains in blood vessels Exchange of materials possible – smallest blood vessels have thin walls Materials diffuse from the blood into the tissue fluid and then into the body cells All cells are surrounded or bathed in a fluid called tissue fluid (E.C.F.) – a medium for the exchange of materials Found in earthworms and vertebrates – a more efficient system

Closed Circulatory System

The Human Circulatory System Humans have a double circulatory system i.e. blood is pumped from the heart to the lungs and back to the heart This is pulmonary circulation and from the heart to the body and back to the heart This is systemic circulation

Double circulation in humans

Separate systems Heart divided by a muscular wall into left and right sides Right side pumps deoxygenated blood to the lungs (pulmonary) Left side pumps oxygenated blood to the body (systemic) Advantage of double circulatory system is adequate blood pressure ensured for both systems.

Blood vessels Three types Arteries Veins Capillaries

Arteries Thick-walled Small lumen (central cavity) Carry blood away from the heart Blood under pressure from heart

T.S. Artery and Vein

Veins Thinner walls than arteries Larger lumen Have valves – for what? Carry blood to the heart Less pressure – not under influence of heart Contraction of body muscles squeeze veins and push blood back to heart

Branching network Arteries branch into smaller arterioles Arterioles branch into capillaries

Capillaries Are the smallest blood vessels Are thin-walled – one cell thick Lie close to nearly every cell in the body – ensuring efficient exchange of material Allow exchange of substances between blood and body cells Reunite to form venules and veins which returns blood to the heart

Exchange of materials

The structure of the blood vessels

Differences between arteries, veins & capillaries Artery Vein Capillary Structure Function Blood flow Thick, three-layered wall of muscle & elastin Thin, three-layered wall of muscle & elastin Wall only one cell thick Extremely narrow lumen Narrow lumen Large lumen No valves Valves present No valves Carry blood away from heart Carry blood to heart Allows exchange of materials between … Rapid under pressure from heart Sluggish under low pressure Pressure reducing Blood flows in pulses Blood flows steadily

Portal blood system (1/3) The pulmonary and systemic circulatory systems begin and end in the heart. Pulmonary System (refer to a diagram) Heart  Pulmonary Artery  Arterioles  Capillaries in lungs  Venules  Pulmonary Vein  Heart

Portal blood system (2/3) Systemic System Heart  Aorta  Arterioles  Capillaries in body organs  Venules  Veins  Heart The Portal System begins and ends in capillaries e.g. hepatic portal system Capillaries (in stomach & intestines)  Venules  Hepatic Portal Vein  Venules  Capillaries (in the liver)

Portal blood system (3/3) Usually blood flows Artery  capillary  vein The portal system is an exception to this

The human circulatory system showing the portal system

The Heart Hollow muscular organ Slightly to the left of the sternum Above the diaphragm Size of clenched fist – 300g

Cardiac muscle Surrounded by fluid filled chamber (friction free movement) and protective sac = pericardium Heart wall made of cardiac muscle Contracts without nervous stimulation Will not fatigue

Cardiac Blood Supply Consists of the coronary blood vessels i.e. Coronary arteries bringing nutrients to the cardiac tissue from the aorta, and Coronary veins carry deoxygenated blood back to the right atrium Emerging from the heart are the aorta, vena cava, pulmonary arteries and veins.

External view of human heart

Internal structure of heart Four chambers – 2 upper & 2 lower Two upper atria – thin walled Two lower ventricles – thick walled and larger than atria Divided vertically into left and right by wall – septum Blood does not flow through the septum

Diagram of internal heart structure

Questions Describe the direction of blood flow through the heart. Why is the wall of the left ventricle thicker than that of the right ventricle? Why are atrial walls thinner than ventricle walls?

Valves in heart Found at the exits of each chamber Four chambers  four valves Function: to prevent a back flow of blood

Operation of valves in the heart

How to draw the heart (1/6)

How to draw the heart (2/6)

How to draw the heart (3/6)

How to draw the heart (4/6)

How to draw the heart (5/6)

How to draw the heart (6/6)

Systole & Diastole systole: contraction phase of cardiac cycle during which the chambers discharge the blood. diastole: relaxation phase of cardiac cycle during which the chambers fill with blood.

Heartbeat (1/2) Pacemaker (S-A node) located in right atrium sends out wave of impulses to muscles of both atria causing atria to contract. This is Atrial systole. The impulses are picked up by the atrio-ventricular node (A-V node)

Heartbeat (2/2) and transmitted to the ventricles via the Purkinje fibres - causing the ventricles to contract. This is Ventricular systole. While the atria are contracting and emptying (atrial systole) the ventricles are relaxing and filling with blood (ventricular diastole) and vice versa

Heartbeat – diagram

Heartbeat sound The lupp-dup sound, heard through a stethoscope, is caused by the closing of the valves of the heart

The Pulse When the ventricles contract blood is forced through the aorta and into the arteries. This causes the arterial walls to expand and contract rhythmically. This is the pulse and can be felt where an artery is near the body surface e.g. wrist, temple, neck.

Blood Pressure Is caused by the pumping action of the heart. Needs to be reasonable high to keep the blood moving. Highest pressure is where the blood is forced into the aorta by contraction of the left ventricle = systolic pressure Lowest pressure is when the ventricles relax = diastolic pressure

Taking blood pressure Use a B.P. machine = sphygmomanometer Measures pressure required to stop the blood flow in artery of upper arm Contraction and relaxation pressures recorded Expressed as a fraction Systolic pressure Diastolic pressure

Blood pressure readings e.g. healthy young adults B.P. = 110/75 mmHg Hypertension = abnormally high blood pressure i.e. > 140/90 mmHg Hypotension = abnormally low blood pressure.

Healthy Circulatory System Effects of Exercise, Diet and Smoking on the circulatory system

Exercise When we exercise the heart beats faster. Makes the heart muscle stronger and more efficient at pumping blood Improves the oxygen supply to the cardiac muscle and Reduces blood pressure

Diet Too much cholesterol from animal fats can build up on the inner walls of the arteries and reduces the rate of flow of the blood e.g. a blockage in the cardiac artery prevents blood and oxygen getting to the cardiac muscle and will cause a heart attack Eating fewer fatty meats and fatty dairy products can reduce the risk of heart disease

Smoking Major cause of heart disease Tobacco smoke contains nicotine and carbon monoxide (CO) Nicotine increases blood pressure CO interferes with the transport of oxygen to the body cells High levels cause hardening of the arteries

The Lymphatic System

The lymphatic system Forms part of the transport system and the immune system Collects excess tissue fluid (see slide 10) and transports it back to the bloodstream Tissue fluid = similar to blood plasma but without the plasma proteins. When tissue fluid enters the lymph system it is called lymph.

Blood and Lymph vessels

Lymph System Composition Composed of: a fluid = lymph, and a system of tubes = lymph vessels

Lymph A fluid containing: lymphocytes (white blood cells) proteins and fats

Lymph vessels Similar to veins – thin walled Form a one way system Have valves – function = ? No heart – no pumping – lymph moves by contraction of body muscles Empty lymph back into bloodstream at subclavian veins Volume of circulating fluid in body remains fairly constant

The Lymph System

Lymph nodes Small rounded structures found along the lymph vessels produce antibodies - destroy invading pathogens and produce and store lymphocytes (white blood cells) Lymph nodes filter the lymph as it flows through trapping and destroying bacteria

Functions of Lymph System Return excess ECF to blood system - maintain balance of fluids in body = HOMEOSTASIS. Absorb and transport fatty acids and glycerol from intestines - lacteals. Produce lymphocytes. Produce antibodies. Remove and destroy bacteria. Transport hormones.

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