Ch. 6 - Transport in the Body (Circulatory System)

• The Circulatory/Transport system is made up of:

  • Blood
  • a system of tubes or blood vessels
  • the heart, which is needed to pump blood through blood vessels
• Blood is made up of 4 parts, or components:


  1. Plasma
  2. Red blood cells
  3. White blood cells
  4. Platelets
• Plasma

  • the liquid part of the blood
  • pale yellow colour
  • mostly made of water
• Plasma pt. 2

  • Transports many dissolved chemicals around the body. These chemicals may be:
  • useful materials, such as food and water
  • wastes, such as carbon dioxide and salts

  Plasma also transports heat from one part of the body to another.
• Plasma also carries

  1. red blood cells
  2. white blood cells
  3. platelets
• Heat is produced by chemical reactions in all our body cells. By transporting heat, our blood plays an important role in maintaining our body temperature at 37 degrees Celsius.
• How plasma affects body temperature

  1. Blood vessels in skin expand (dilate) when too hot

  2. Extra blood (plasma) sent to skin, especially face, causing redness

  3. More heat passes out of body, cooling down

  4. Blood vessels in skin become smaller when too cold

  5. Blood moves from extremities to core

  6. Less heat lost from body
• When we are too hot

  Blood vessels in our skin expand (dilate)
• Blood vessels in skin expanding


  Extra blood (plasma) is sent to our skin (especially to the face, causing it to go red)
• Extra blood (plasma) sent to skin


  Allows more heat to pass out of our body and we cool down
• When we are ill


  Our body temperature may rise (we have a fever)
• The high temperature helps to destroy the bacteria and viruses that are causing us to be ill
• When we are too cold


  Blood vessels in our skin become smaller
• Blood vessels in skin becoming smaller


  Blood also moves from our extremities to our core
• Blood moving from extremities to core


  We lose less heat from our body
• Red Blood Cells


  • red blood cells are made in bone marrow located in the centre of the bones
  • contain a red coloured chemical (or pigment) called haemoglobin
  • to make haemoglobin, we need iron
  • our blood contains huge numbers of red blood cells
  • haemoglobin (and therefore red blood cells) carries oxygen
• The Path of Oxygen


  1. Oxygen enters our red blood cells in the lungs.
  2. It attaches to haemoglobin in the red blood cells.
  3. When blood reaches cells in other parts of our body (such as our muscles or the brain), haemoglobin releases the oxygen into these cells.
• White Blood Cells


  • are also made in bone marrow
  • white blood cells fight infection:
  • some white blood cells surround microorganisms (such as bacteria and viruses) and destroy them
  • Other white blood cells form proteins called antibodies
  • Antibodies help to destroy microorganisms that have entered the body
  • antibodies are very important in fighting infection
• Platelets


  • are formed in bone marrow when large cells break down into smaller pieces
  • They help to form blood clots
  • In this way, they help to prevent:

  1. Loss of blood
  2. microorganisms entering the body
• Functions of the 4 parts of the blood


  1. Plasma:

  • transports materials such as foods and wastes
  • Transports heat around the body

  2. Red blood cells:

  • transport oxygen

  3. White blood cells:

  • fight infection

  4. Platelets

  • clot the blood
• The 3 main types of blood vessel


  1. Arteries
  2. Veins
  3. Capillaries
• Arteries


  Arteries carry blood away from the heart.

  (Remember 'a' is for artery and for away.) As a result of carrying blood away from the heart, there is a strong flow of blood in arteries. We say that the blood in arteries is under high pressure.
• Veins


  Veins carry blood to the heart. The blood flow, or pressure, in a vein is lower than in an artery.
• Capillaries


  • tiny blood vessels.
  • They are found between arteries and veins.
  • There is a huge number of capillaries in the human body.
  • The walls of a capillary are very thin.
  • They allow materials to pass into and out of the capillaries.

  For example, in our intestines food passes into blood capillaries. This food is carried by the bloodstream to all the cells of the body. The food later passes out of the capillaries to enter the body cells.
• The Heart


  The heart is about the size of a clenched fist. It is located between the middle and the left-hand side of the chest.

  The heart contracts in order to pump blood around our body in blood vessels. The force of this blood in an artery causes a pulse. When we are resting, the average rate of an adult heartbeat is 70 beats per minute. When we exercise, the heart beats faster. This causes blood and the materials it carries to move faster around our body.
• Cardiac Muscle


  • The heart is made of a special type of muscle called cardiac muscle
  • Cardiac muscle is very strong and does not tire easily
  • 'Cardiac' means anything related to the heart
• Structure of the Heart

  • Chambers: the heart contains four chambers. The top two are the right atrium and the left atrium (plural atria) the bottom two are the right and left ventricles.
  • Septum: the two sides of the heart are separated by a muscular wall called the septum
  • Heart valves: valves in the heart make sure that blood can flow only in one direction. In this way, they are similar to valves in a car tyre or football (which let air pass in, but not out)
• How blood flows through the heart

  1. Blood from the arms, legs and other parts of the body enters the right atrium of the heart through the vena cava

  2. The right atrium contracts to pump the blood down through a valve into the right ventricle

  3. When the right ventricle contracts, the valve shuts to prevent the blood from going back into the right atrium

  4. Blood is pumped out of the heart in the pulmonary artery to the lungs

  5. In the lungs, the blood gains oxygen (and also loses carbon dioxide and water vapour)

  6. Blood from the lungs flows back into the left atrium of the heart through the pulmonary vein

  7. The left atrium contracts to pump the blood through a valve and into the left ventricle

  8. The left ventricle contracts, the valve snaps shut and blood is forced out of the heart through the aorta

  9. The blood then passes all around the body

  10. Eventually this blood will lose oxygen to the body cells and return to the heart in the right atrium

  11. The cycle then starts all over again
• Blood from the arms, legs and other parts of the body

  Low in oxygen
• Blood from the lungs

  Rich in oxygen
• Pulmonary Artery & Vein

  • Most of the arteries in the body carry oxygen-rich blood. However, the pulmonary artery is an exception to this rule as it carries blood low in oxygen.
  • Most of the veins in the body carry blood low in oxygen. However, the pulmonary vein is an exception to this rule as it carries oxygen-rich blood.
• The 2 Blood Circuits


  The circulatory system consists of two circuits:

  • In the lung circuit, blood flows from the heart to the lungs and back to the heart
  • In the longer body circuit, blood flows from the heart to the rest of the body and back to the heart again.
• Pulse

  • when blood is pumped through the arteries, the pressure causes the arteries to expand
  • This wave of pressure is called a pulse
  • A pulse can be felt in areas of the body where the arteries are close to the surface, for example at the wrist and in the neck
  • The pulse rate is used to measure the rate of heartbeat
• How Exercise Affects Pulse Rate

  • when we exercise, the cells in the body (especially in the muscles) need increased supplies of food and oxygen.
  • In addition, the cells need to get rid of extra amounts of carbon dioxide and heat
  • As a result, exercise causes the heart to beat faster and our pulse rate increases
• What happens to blood in different parts of the body?

  
• What pathway around the body does the blood take?