The Circulatory System

The Circulatory System

While small organisms may rely on diffusion and osmosis, large organisms need a transport system to distribute food and oxygen and to collect wastes efficiently.

The mammalian circulatory system is made up of blood, blood vessels and the heart

Blood

Red Blood Cells Produced in the red bone marrow. The cells lose their nuclei becoming tiny, circular, discs. The biconcave structure made up of spongy cytoplasm in an

elastic cell membrane is extremely flexible and enables them to squeeze through tiny spaces.

The cytoplasm contains heamoglobin (protein plus iron) which gives blood its red colour

High O2 content Heamoglobin + oxygen oxyheamoglobin

(darker red) Low O2 content (bright red)

Red Blood Cells

Each cell lives for about 4 months. It breaks down to give a yellow pigment

(removed in the bile) and iron (stored in the liver).

200,000 million red blood cells are replaced each day!

White Blood Cells

Made in the bone marrow. They are larger than red cells and in the

ratio of 1 wbc:600 rbc. Many white blood cells require

development and maturation in spleen, lymph nodes and thymus.

White blood cells

Majority are phagocytes They move by the flowing of cytoplasm

and can squeeze out of blood capillaries into surrounding tissues.

They collect at wounds, ingest (engulf) and digest bacteria and cell debris.

White blood cells

Lymphocytes produce antibodies against antigens (any substance-usually foreign - that stimulates antibody production).

Antibodies (a kind of protein) are specific in their action eg flu antibodies only effective against flu virus

Lymphocytes

Antibodies are released into the blood and

♦ destroy antigens

♦ become attached to their surface so

that they are more easily ingested

by phagocytes or

♦ clump antigens together so that they

cannot function.

Lymphocytes

Lymphocytes also produce anti-toxins (chemicals that neutralize poisonous substances produced by bacteria).

Lymphocytes are produced quickly when the body is being attacked

Immunity- White blood cells, lymph nodes, spleen and thymus make up the immune system.

Types of Immunity

Innate immunity: from mother’s milk to baby. Passive immunity

Natural acquired immunity: eg person who has had chicken pox unlikely to get it again. Active

Artificial acquired immunity: vaccination. Active

Passive immunity: Antibodies extracted from plasma and used to treat patients at risk

Organ Transplants

Immune response protects our body against bacteria, viruses and any foreign proteins

All cells carry antigens (proteins) on their surface. Different people have different antigens and so have different ‘tissue types’ (cf fingerprints). Close relatives may have similar but not identical tissue types

In transplant surgery, donated tissue is foreign and attacked and destroyed by white blood cells.

Immunosuppressive drug, eg Cyclosporine A, must be given to transplant patients to suppress their immune response. This protects the transplant but leaves him vulnerable to attack by disease organisms

Platelets

Fragments of cells budded off in the bone marrow. They clot blood over wounds

Platelets and damaged cells produce thrombokinase, an enzyme that changes the protein prothrombin into thrombin. This enzyme converts soluble fibrinogen into fibrin, which forms a network of fibres across wound.

Red blood cells trapped and forms clot (Ca++ and vitamin K needed)

Haemophilia?

Haemophilia, a heredity disease has an impaired blood clotting mechanism.

Defect impairs the production of the plasma protein, fibrinogen.

Plasma Mainly water with ♦ many mineral ions: K+, Na+, Ca++, Cl-, HCO3- ♦ proteins: fibrinogen, albumins, globulins, prothrombin ♦ food substances: glucose, aa, fats ♦ wastes : urea ♦ hormones Composition kept constant by liver and kidneys

The Heart

The Heart

A pump made of cardiac muscle Two atria, two ventricles pulmonary vein (oxygenated blood from lungs) vena cava (deoxygenated blood from body) aorta pulmonary artery valves tendons (usually join muscles to bone)

The Heart

The Heart

Heart Valves

Tricuspid Valve

Heart

Cardiac muscle – never tired

Hole in the heart?

Double Circulation in Mammals

High pressure systemic circulation (thicker wall of left ventricle compared to right ventricle) and

lower pressure pulmonary circulation

DoubleCirculation

Heart beat

The two atria contract together and then the two ventricles

Cardiac muscle has a natural rhythmic contraction rate and a ‘pacemaker’; keeps heart rate at 50-100 beats/minute

Heartbeat varies with sex, exercise, age, emotions

Blood Pressure

Pumping action of the heart produces blood pressure.

Varies with age, health

Coronary heart disease

Deposits of fats may be laid down in wall of arteries – atheroma.

Patches become more numerous and spread with age, small blood clots may occur on inner surface of arteries.

Reduced blood flow causes pain in chest – angina - especially during exercise.

Atheroma may block important artery eg coronary arteries, producing a heart attack or coronary thrombosis. (A thrombosis in brain produces a stroke)

CoronaryArteries

Artherosclerosis and THrombosis

Causes of CHD

Smoking. Smokers 2 to 3 times more likely to die from heart attack. CO and other chemicals in cigarette smoke may damage the lining of arteries and allow atheroma formation

Fatty diet. Atheroma contains cholesterol, lipids and protein. Eating animal fats lead to raised cholesterol levels

Stress. Stress raises blood pressure which may increase atheroma formation

Lack of exercise. Regular, vigorous exercise reduces the chances of a heart attack by improving coronary blood flow

Blood Vessels

Blood Vessels -Arteries

Carry blood away from heart. Walls with elastic and muscle fibres;

can withstand blood flow under high pressure.

Blood flow in pulses or waves. Arteries with oxygenated blood except

pulmonary arteries

Blood Vessels - Arterioles

Arterioles are smaller arteries. When muscle in arteriole wall contract,

arterioles narrow and restrict blood flow so that blood flow to different parts of body controlled

Blood Vessels

TS Artery and Vein

Blood Vessels - Capillaries

Tiny vessels, wall one cell thick and partially permeable.

Form dense network in body. Blood pressure forces part of plasma

through walls producing tissue fluid which bathes all living cells and supplies them with food and oxygen. Seeps back into capillaries with wastes

Capillary

Blood Vessels - Veins

Carry blood to heart. Larger diameter than arteries, walls thinner,

less elastic and muscular. Valves present to prevent backflow. Blood

pressure is steady and low. Contraction of skeletal muscles around veins

squeezes the thin-walled veins and pushes the blood along.

Carry deoxygenated blood except pulmonary veins - less food, more CO2

Movement ofBlood in Vein

Venules are small veins

Valves in Veins

Varicose Veins

Lymphatic system

Not all tissue fluid return to capillaries. Some enter blind-ended, thin walled lymphatic vessels. (Lacteals in small intestine part of lymphatic system)

Valves present Movement of lymph helped by contraction of

skeletal muscles around them. Lymph similar to tissue fluid.

Rejoin blood circulation in thorax.

The LymphaticSystem

Lymphatic System

Blood and Lymph

Lymphatic system

Swellings or lymph nodes store lymphocytes, some phagocytes, filter off disease organisms from lymph.