1. The Transport System
IB topic 6.2

2. The transport system Mammals have a closed circulation
Blood is pumped by the heart and circulated in a continuous system of arteries, veins, and capillaries
Under pressure
The heart has four chambers
The heart is divided into right and left sides
Blood flows from the right side of the heart to the lungs, then back to the left side of the heart
From here, it is pumped around the rest of the body and back to the right side of the heart
Blood passes twice through the heart in every single circulation of the body (double circulation)

3. Features of the circulatory system
Advantages in mammalian circulation:
Simultaneous high pressure delivery of oxygenated blood to all regions of the body
Oxygenated blood reaches respiring tissues

4. Blood Blood is tissue Consists of: Liquid medium called plasma
Erythrocytes (RBC)
Involved in transport of respiratory gases (O2, CO2)
Leucocytes (WBC)
Combat infection
Lymphocytes
Form antibodies
Phagocytes
Ingest bacteria or cell fragments
Platelets
Blood clotting mechanism

5. Blood break-down Blood is: 55% plasma 45% cells Plasma is:
90% water
10% dissolved substances (proteins, salts, lipids)
45% cells
RBC, WBC, platelets

6. Blood transports … Nutrients Oxygen Carbon dioxide Hormones Antibodies
Urea
Heat

7. The plumbing of the circulation system
There are three types of vessels:
Arteries: carry blood away from the heart
Veins: carry blood back to the heart
Capillaries: fine networks linking arteries and veins
Both arteries and veins have strong, elastic walls
Arteries are very much thicker and stronger
Strength: collagen
Elastic: smooth muscle fibers
Capillaries
Endothelium (inner layer)
Branch
No cell is far from a capillary

8. Why the differences? Blood leaving the heart is under high pressure
Thick arteries
By the time blood reaches the capillaries , the pressure has decreased greatly
Thinner capillaries and veins
Also, low pressure may mean backflow, which is why veins have valves
Valves are opened by blood pressure from behind

9. Differences Capillary – site of exchange
Artery – carries blood away from heart under high pressure
Vein – carries blood back to heart under low pressure
Outer Layer (collagen)
Absent
Present
Middle Layer (elastic fibers and involuntary muscle fibers)
Thick layer
Thin layer
Inner layer (or endothelium)
Valves

10. The arrangement of arteries and veins
The right side
Pumps deoxygenated blood to the lungs
Arteries, veins, capillaries = pulmonary circulation
The left side
Pumps oxygenated blood to the rest of the body
Arteries, veins, capillaries = systemic circulation
Aorta (artery)

11. Process The branching sequence of circulation:
Aorta  artery  arteriole  capillary  venule  vein  vena cava
Vena cava carries blood back to the heart

12. The Heart
About the size of a clenched fist

13. The heart as a pump Divided into 4 chambers
Upper: thin walled atria (atrium = singular)
Receive blood into the heart
Lower: thick walled ventricles
The left is much thicker than the right
The volumes are identical
Pump blood out of the heart
You should know the flow of blood

14. The heart as a pump
Coronary arteries supply the walls of the heart with oxygenated blood
Valves prevent backflow
Atrio-ventricular valves prevent backflow from ventricles to atria
Right side: tricuspid valve
Left side: bicuspid or mitral valve
Tendons are attached to prevent folding back
Semi-lunar valves separates the ventricles from pulmonary artery (right side) and aorta (left side)

17. Animations
Penn health cardiology and cardiac surgery