BLOOD CIRCULATION SYSTEM

• The heart and blood vessels form the circulatory system
• Blood runs in a network of blood vessels divided into three types: arteries, veins, and capillaries
• The force exerted by the blood flow through the main arteries is called blood pressure
• Arteries have strong, muscular and elastic walls that enable them to expand with each surge of blood away from heart and towards tissue
• Aorta is the largest artery in the human body
• Veins are one-way valve that keep blood flowing back to the heart. Actions of muscles around these thin-walled vessels squeezes blood through them
• Oxygenated blood is pumped out of the heart around the body. Blood that has given up its oxygen to body tissues flows back to the heart
• A network of fine blood vessels (capillaries) within the body tissues forms a link between the arteries and veins. The capillaries have thin walls and a slower blood flow to allow oxygen and nutrients to pass from the blood to the tissues, and waste products to be removed

• There are about six litres (10 pints), or 1 pint per stone (0.5 litres per 6.4 kilograms), of blood in the average adult body
• It consists of roughly 60% of clear yellow fluid (plasma) in which are suspended the red and white blood cells and platelets that make up the other 40%
• The red blood cells contain haemoglobin, a red pigment that enables them to carry oxygen
• White cells defend the body against infection
• Platelets help blood to clot

• Oxygen levels in the blood may fall if the haemoglobin in the red blood cells is reduced (anaemia), or if there is not enough oxygen in the lungs. Anaemia makes skin look pale; blood low in oxygen gives a gray-blue tinge to skin (cyanosis)
• Continuously high blood pressure, produced by conditions like hardening of the arteries (arteriosclerosis), may cause a blood vessel to burst, resulting in internal bleeding
• Poor circulation, hardened arteries, or narrowed blood vessels can cause a blood clot (thrombosis) to form. A clot may travel within the circulatory system to lodge elsewhere (embolism), and can endanger vital organs such as the lungs
• A fall in the blood pressure (as in severe bleeding) reduces blood supply, and hence oxygen, reaching vital organs

• Each beat of the heart creates a wave of pressure (the pulse) that passes along the arteries
• It can normally be felt where an artery passes close to the surface of the body
• In adults, the pulse rate is usually between 60 and 80 beats per minute. It is faster in children and may be slower in very fit adults
• The pulse rate may increase with exertion, fear, fever, blood loss, and some illnesses
• Certain heart disorders, fainting, and an increase in pressure inside the skull may slow the pulse

• The pulse can be recorded at the wrist (known as the radical pulse) or in an emergency, at the neck (carotid pulse)
• In babies, the brachial pulse, on the inside of the upper arm, may be easier to find. Check and record:
• The rate (beats per minute)
• The strength (strong or weak)
• The rhythm (regular or irregular)

• Arterial bleeding
• Richly oxygenated blood is bright red and, under pressure from the heart, spurts from a wound in time with the heartbeat
• A severed main artery may jet blood several feet high, and rapidly reduce the volume of circulating blood
• Venous Bleeding
• Venous blood, having given up its oxygen, is dark red. It is under less pressure than the arterial blood, but as vein walls are capable of great distension, blood can “pool” within them. Blood from a severed major vein may gush profusely
• Capillary bleeding
• This type of bleeding, or oozing, occurs at the site of all wounds. Capillary bleeding may at first be brisk, but blood loss is usually slight. A blunt blow may rupture capillaries under the skin, causing bleeding into the tissues (bruise)

• For good wound care, first wash hands thoroughly and cover own sores or wounds with a waterproof dressing. Avoid touching the wound with your fingers while treating it (if possible, use disposable latex gloves) and don’t talk, cough, or breathe over the wound or the dressing
• Minor bleeding is readily controlled by pressure and elevation. A small adhesive dressing is normally all that is necessary. Medical aid need only be sought if the bleeding does not stop, or if the wound is at special risk of infection
• If the wound is dirty, clean it by rinsing lightly under running water, or use an antiseptic wipe. Pat dry with a gauze swab. Temporarily cover the wound with sterile gauze. Elevate the wounded part above the level of the heart, if possible

• If possible use disposable gloves, and wash hands well in soap and water before, and after, treatment. Cover own sores or open wounds with a waterproof dressing
• Remove or cut clothing to expose the wound. Watch out for sharp objects, such as glass, that may injure you
• Apply direct pressure over the wound with your fingers or palm, preferably over a sterile dressing or clean pad – but do not waste time hunting for a dressing
• If you cannot apply direct pressure, for example, if an object is protruding, press down firmly on either side. Raise and support the injured limb above the level of the casualty’s heart
• Handle the limb very gently if the injury involves a fracture
• Lay the casualty down. This will reduce blood flow to the site of injury, and minimize shock
• Leaving any original pad in place, apply a sterile dressing. Bandage it in place firmly, but not so tightly as to impede the circulation
• If bleeding seeps through the dressing, bandage another firmly over the top. Secure and support the injured part with bandaging

The brachial artery runs along the inner side of the upper arm. Press your fingertips in beneath the biceps muscle to feel for pulsation, and press the artery firmly against the bone.

Lay the casualty down with the knee bent to locate the groin of trouser fold, feel for the femoral artery which crosses the pelvic bone, in the centre of groin crease, then press firmly with your fingers

Suspect internal bleeding if, following injury, signs of shock develop without obvious blood loss. At the site of a violent injury, there may be “pattern bruising” – discolouration with the pattern of clothes or crushing objects. There may be blood at body orifices, either fresh or mixed with the contents of injured organs. There may also be:

• Pallor
• Cold, clammy skin
• A rapid, weak pulse
• Pain
• Thirst
• Confusion, restlessness, and irritability, possibly leading to collapse and unconsciousness
• Information from the casualty that indicates recent injury or illness, previous similar episodes, or if he or she takes drugs for a medical condition

• Help the casualty to lie down, and raise and support his legs
• Loosen clothing at the neck, chest, and waist. Insulate the casualty from cold
• Monitor and record breathing, pulse, and level of response every ten minutes. Note the type, amount, and source of any blood loss from body orifices. If possible, send a sample with the casualty to the hospital

All open wounds are vulnerable to contamination by microorganisms known as germs. These can come from the wounding source, from the air, from the breath or the fingers, or from particles of clothing embedded in wound (such as with a gunshot wound). Bleeding flushes some of the dirt away and remaining germs may be destroyed by the white blood cells.

If dirt or dead tissue remain, there may be serious consequences. Germs can multiply and spread infection through the body (septicaemia), or tetanus infection can develop. A casualty with heavily contaminated or other susceptible wounds may need antibiotics or anti-tetanus injections. Wounds that do not begin to heal within 48 hours should be considered to be infected. In these cases there may also be fever.

As infection develops, there may be:

• Increasing pain and soreness
• Swelling, redness, and a feeling of heat around the injury
• Pus within, or oozing from, the wound
• Swelling and tenderness of the glands in the neck, armpit, or groin
• Faint red trails – leading to these glands – on the skin
• In advanced infection, signs of fever: sweating, thirst, shivering, and lethargy

• Cover the wound with a sterile dressing or a clean pad, and bandage it in place
• Raise and support the injured part to reduce swelling
• Tell the casualty to see his/her doctor. If the infection is advanced, call a doctor, or take or send him/her to the hospital

• A faint (also known as syncope) is a brief loss of consciousness that is caused by a temporary reduction of blood flow to the brain
• Unlike shock, the pulse become very slow, although it soon picks up and return to normal
• Recovery from a complete faint is usually rapid and complete
• A faint may be reaction to pain of fright, or the result of emotional upset, exhaustion, or lack of food
• It is more common, however, after long periods of physical inactivity, such as standing still, especially in a warm atmosphere. The inactivity causes the blood to pool in the lower part of the body, reducing the amount of oxygen available to the brain.

• A brief loss of consciousness, causing the casualty to fall down to the floor
• A slow pulse
• Pale, cold skin and sweating

Treatment for Fainting

• Lay the casualty down, and raise and support her legs
• Make sure that the casualty has plenty of fresh air; open a window if necessary
• As the casualty recovers, reassure and help the casualty to gradually sit up
• Look for and treat any injury that has been sustained through falling
• If the casualty does not regain consciousness quickly, open the airway, check breathing and pulse, and be ready to resuscitate if necessary
• Place the casualty in the recovery position

The circulatory system distributes blood round the body, so that oxygen and nutrients can pass through and “perfuse” the tissues. When the system fails, circulatory shock will develop. If this is not treated swiftly, vital organs such as the heart and brain may fail, which can lead to death. The condition can be made worse by fear and pain.

Where there is a risk of shock developing, reassuring the casualty and making him/her comfortable may be sufficient to prevent the condition from deteriorating. Do not confuse circulatory shock with psychogenic shock. This occurs when, for example, a person suffers deep emotional stress.

What causes circulatory shock?

Shock can develop if the heart fails to pump blood through the circulatory system (a common cause is a heart attack), or if the blood vessels dilate, as in severe infection or anaphylactic shock, reducing the blood pressure. Shock may also occur if the blood supply to the body’s vital organs is reduced through blood loss or loss of other bodily fluids through burns, severe diarrhoea, or vomiting. The body responds to fluid loss initially by diverting the blood supply from the surface to the vital organs. Shock develops if fluid loss is not stopped.

1. At first, the release of adrenaline causes:
• A rapid pulse
• Pale, gray-blue skin, especially inside the lips. A fingernail or earlobe, if pressed, will not regain its colour immediately
• Sweating, and cold, clammy skin
2. As shock develops, there may be:
• Weakness and giddiness
• Nausea, and possibly vomiting
• Thirst
• Rapid, shallow breathing
• A weak pulse. When the pulse at the wrist disappears, about half the blood volume will have been lost
3. As the brain’s oxygen supply weakens:
• The casualty may become restless, anxious, and even aggressive
• The casualty may yawn and gasp for air (known as “air hunger”)
• The casualty will become unconscious
• Finally, the heart will stop

• Recognize shock, treat any obvious cause, improve the blood supply to the brain, heart and lungs, and arrange removal to hospital
• Treat any cause of shock you identify (such as external bleeding)
• Lay the casualty down on a blanket to protect him/her from the cold ground, keeping her head low. Constantly reassure the casualty
• Raise and support his/her legs to improve the blood supply to the vital organs. Take care if you suspect a fracture
• Loosen tight clothing, such as braces or belts, to reduce constriction at the neck, chest, and waist
• Keep the casualty warm by covering her with coats or blankets
• Check and record breathing, pulse, and level of response. Be prepared to resuscitate if necessary

1. Give two pressure points.
2. How do you feel for a pulse?
3. What is the treatment for fainting?
4. How many liters of bloods in a human body? Do any effects on s donors after donating their blood?