Leaving Certificate Agricultural Science

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Leaving Certificate Agricultural Science
The Circulatory System
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Functions of the Circulatory System

• To carry digested food from the small intestine
  to all areas in the body which need it.
• To carry oxygen from the lungs to the rest of the
  body.
• To aid in the disposal of all wastes from the
  body.
• To distribute heat.
• To fight diseases by using white blood cells to
  fight off infection.

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Composition of Blood

• The blood is made up of different types of cells
  and a liquid medium for which they are
  transported.
• The cells in the blood are Red Blood Cell
  (Corpuscles), White Blood Cells and Platelets.
• Plasma is the liquid medium of blood.
• Red Blood Corpuscles are technically not cells at
  all, as they do not contain a nucleus.
• Their red colour is from a substance known as
  haemoglobin.
• Haemoglobin binds with oxygen so it is the red
  blood corpuscles that carry oxygen in the body.

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Blood Cells (Video)
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Composition of Blood 2

• White Blood Cells are largest and not as
  plentiful in the blood as corpuscles.
• These cells are used to fight infection.
• Foreign bodies are either devoured by the cells
  or the cells produces antibodies, which in turn
  attack the infection.
• Platelets are small fragments of cells, and are
  responsible for blood clotting.
• A Haemophiliac (someone who cannot clot) doesnt
  have any platelets.
• Plasma is the medium in which all the cells are
  maintained.
• It contain water, proteins (fibrinogen), food,
  wastes (e.g. CO2), Antibodies and Hormones.

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The Heart

• The heart is a four-chambered hollow muscle, used
  to pump blood all over our bodies.
• It is divided into four compartments, the left
  and right ventricles and the left and right atria
  (atrium in singular).
• The right side of the heart pumps blood low in
  oxygen (de oxygenated) to the lungs.
• The left side of the heart pumps blood rich in O2
  (oxygenated blood) all over the body.

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The Heart Beat

• Blood enters the heart through the superior and
  inferior Vena Cava and into the right atrium.
• The tricuspid valve opens and the blood is moved
  into the right ventricle.
• The walls of the right ventricle contract and the
  blood is pumped up to the lungs (through the
  pulmonary artery) where oxygen replaces CO2 in
  the blood.
• The oxygenated blood enters the heart from the
  lungs through the left atrium (via the pulmonary
  vein).
• Again a valve opens and the blood moved into the
  left ventricle.
• The walls of the ventricle contract and the blood
  is pumped all over the body via the Aorta.
• The rate of beat is controlled by the pace maker
  in the septum.

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Arteries and Veins

• Arteries
• Carry blood away from the heart always.
• Have thick muscular walls
• Have a pulse
• Deep under the skin
• Have no valves
• Veins
• Carry blood to the heart.
• Have thin walls
• Do not have a pulse
• Near surface of the skin
• Have valves to stop back-flow of blood.
• Capillaries are small blood vessels acting as
  veins and arteries.
• The walls of capillaries are only one cell thick
  so substances (Food or cells) can easily get
  through them and into the blood or out.

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Hepatic Portal Vein

• The Hepatic portal system is a transport system
  between the small intestine, the liver and the
  heart.
• It consists of the hepatic portal vein, the
  hepatic artery and the hepatic vein.
• The hepatic artery carries oxygenated blood to
  the liver for use and the collection of wastes.
• The hepatic vein carries the used blood back to
  the heart.
• The Hepatic Portal Vein carries blood from the
  small intestine to the liver.
• This blood is low in O2 but rich in Glucose and
  other food types.
• The Glucose is converted to Glycogen in the Liver
  and stored there.

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Hypertension

• Hypertension (or high blood pressure) is caused
  by the blood vessels becoming narrow because of
  the build up of fat or from stress.
• The heart therefore needs to pump harder to get
  the blood through the narrow vessels.
• This can cause the left ventricle to grow, and
  can lead to the heart not functioning properly.

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Heart Attack Stroke

• The heart also needs a supply of blood and gets
  from the coronary arteries.
• If these arteries get blocked, a heart attack
  occurs.
• A stroke is caused by a blockage or leak of blood
  vessels in the brain.
• Every year in Ireland, 10,000 people die of heart
  attack or stroke.

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Risk Factors of Heart Disease

• The risks factors of heart attack and stroke are
• Smoking nicotine can also block the arteries.
• Obesity more fat deposits in the blood vessels
• Regular exercise can reduce the risk of heart
  disease.
• Stress increases the risk of heart attacks.