1. The Circulatory system
Objectives
1. To learn the role and structure of the heart
2. To understand the double circulatory system of humans
3. To learn the key features of the three main types of blood vessels.
4. To know what can go wrong and why.

2. Human circulatory system

3. Key features 1. It is double 2. The heart pumps blood around it
3. It carries materials around the body
4. Systemic system takes oxygenated blood round the body and returns deoxygenated blood to the heart
5. Pulmonary system takes deoxygenated blood to the lungs and returns oxygenated blood to the heart

4. Blood vessels
1. Chemicals exchange into and out of the blood in capillaries
2. Arteries lead away from the heart
3. Veins lead to the heart

5. What the blood carries O C G A F M V

6. The Heart

7. The journey of blood
Blood flows along pulmonary artery to lungs
(Back flow prevented by tricuspid valve)
Right ventricle contracts and blood pushed into pulmonary artery
Right atrium contracts and blood pushed to right ventricle
Deoxygenated blood enters heart in right atrium from vena cava.

8. Journey of blood contd. Gas exchange in the capillaries of the alveoli
(Backflow prevented by bicuspid valve)
Left ventricle contracts and blood enters the aorta to travel to the rest of the body
Left atrium contracts blood flows to left ventricle
Blood enters left atrium
Oxygenated blood flows from lungs to heart in pulmonary vein
Gas exchange in the capillaries of the alveoli

9. Structures of the heart
Left and right side separated by solid septum to prevent mixture of oxygenated and deoxygenated blood
Left wall much thicker as it has to pump blood all round body. (right wall only pumps to lungs)
In baby septum, is open because it gets oxygen from placenta not lungs. Septum closes at birth
Failure to do so leads to hole in the heart or blue baby.-

10. Additional features
Valves held in place by tendons called Heartstrings
Semi lunar valves prevent blood from arteries flowing back into ventricles.
Heart muscle supplied with food and oxygen by cardiac artery
Blockage of cardiac artery leads to cell death and heart attacks.

11. Rhythmic contraction of heart muscle
Heart beat
This travels to the atrio-ventricular (AV) node which stimulates the contraction of the ventricle
Atrium contraction led by sino-atrial (SA) node – also called the cardiac pacemaker
Stimulated by nodes
Cardiac muscle is the only muscle that can initiate its own contractions
Rhythmic contraction of heart muscle

12. Heart beats
Volume and speed can vary dependent upon need. Regulated by the nervous system.
On average about 5.25L pumped per minute – approximately your total body volume.
An electrocardiogram showing the impulses of a normal heart beat.
P shows the initiation of the contraction from the SA node
R shows the initiation of ventricular contraction

13. Cardiac cycle Systole refers the period of contraction- High pressure
Time
Atria
Ventricles
0.15 secs
Systole
Diastole
0.3 secs
0.4 secs
Systole refers the period of contraction- High pressure
Diastole refers to the period when the chambers of the heart are relaxed – low pressure

14. Blood vessels

15. Arteries Take blood from the heart
Oxygenated blood (pink)in systemic system
Deoxygenated blood (brown) in pulmonary system
Thick muscular walls with elastin layer
Narrow lumen
Have pulse
Blood at high pressure
Arterioles have less elastic tissue but proportionally more muscular tissues to allow for vaso-constriction.
This can control flow to skin surface and thus control heat loss/conservation

16. Veins Take blood to the heart
Valves prevent backflow.
Blood at low pressure
No pulse
Much larger lumen
Elastin layer in walls
Thinner muscle layer in walls
Deoxygenated in the systemic system and oxygenated in the pulmonary system
Take blood to the heart

17. Capillaries 1. Walls one cell thick
2. Cells in wall can pull apart making them leaky
3. Site of movement of chemicals into and out of the blood and cells.
4. Lumen diameter wide enough to allow one rbc to pass through

18. Our major vessels

19. These are not correct! Blood flows down one leg and up the other;
Three kinds of blood vessels are arteries, vanes and caterpillars

20. What can go wrong
1. With time our arteries become blocked with plaques
2. These are a build up of fatty deposits.
3. They restrict blood flow raising blood pressure.
4. This is known as hardening of the arteries or atherosclerosis
5. Eventually lead to blockages.

21. Blockages (Thrombus) Prevent oxygen and food reaching body cells.
Leads to cell death.
In heart muscle leads to heart attack
In brain leads to stroke
Elsewhere in body just referred to as an infarction.

22. Risk factors Aging High levels of LDL Low density blood cholesterol
Fatty diets
Obesity
Smoking
Diabetes
Inactivity
Use of steroids
Possibly the pill
Genetic predisposition

23. Preventative measures
Vegetarian food
Onions, garlic and a little red wine
Fruit, vegetables and a high fibre diet
At least 20 minutes aerobic exercise regularly
Avoid transfats

24. Plenary questions Which blood vessels lead from the heart?
Which blood vessels have strong muscular walls?
In which part of the system do the veins carry oxygenated blood?
The contraction of which part of the heart raises our blood pressure to its maximum?
Describe what happens during a heart attack.