1. The Heart and blood vessels
Clinical Science Team
School of Nursing and Midwifery

2. The Heart and blood vessels
Learning outcomes:
The learner should be able to..
State the function of the heart and blood vessels
Label a diagram of the heart, indicating its gross anatomical features
State the function of the right and left sides of the heart
State the function of the valves within the heart
Describe the blood flow through the heart
Outline the hearts electrical conduction pathway
Describe the pressure changes that occur in the ventricles during the cardiac cycle
Outline the neural and hormonal control of the heart

3. The Heart and blood vessels
Learning outcomes:
Compare the structure of an artery and a vein
Explain how the structure of an artery and a vein relates to its function
Describe the structure of a capillary and explain the physiological significance of this structure

4. The circulatory system
List the components of the circulatory
system: 1. 2. 3. 4.
What are its main functions?
a) b) c)

5. The circulatory system
The circulatory system consists of the following components:
The Heart
The blood vessels
The blood
The lymphatic system

6. Functions of the Circulatory System
The circulatory system has the following main functions:
Transportation
Regulation
Protection

7. Functions of the Circulatory System
Transportation:
Respiratory: transports oxygen to the tissues and carbon dioxide back to the lungs
Nutritive: Absorbed digested products are transported to the liver and to tissues
Excretory: Waste products from metabolism are transported to the kidneys for excretion in urine

8. Functions of the Circulatory System
Regulation:
Hormonal: Hormones are carried from the endocrine glands to their target tissues
Temperature: The blood can be diverted to warm or cool the body

9. Functions of the Circulatory System
Protection:
Clotting: Blood contains clotting factors and platelets- when activated prevent blood loss through clot formation
Immune: Blood contains leucocytes (white blood cells), cytokines, and complement which protects against infective pathogens

10. The Heart
Describe the Heart
What is its function?

11. The Heart

12. The Heart

13. The Heart

14. The Heart Slightly larger than the size of a fist
Contains four chambers
Right side supplies the pulmonary circulation
Left side supplies the systemic circulation
Two sides are separated by a muscular wall called the septum
Atria and ventricles are separated by a dense layer of fibrous tissue- the fibrous skeleton

15. The Heart wall

16. Myocardial tissue

17. The Heart: Valves The Heart contains four valves
The Tricuspid valve opens from the R atrium into the R ventricle
The Pulmonary (semilunar) valve opens from the R ventricle into the pulmonary artery
The Mitral valve opens from the L atrium into the L ventricle
The Aortic (semilunar) valve opens from the L ventricle into the Aorta

18. The Heart: Valves Function of the valves
Situated at the entrance and exit of the ventricles
Ensure that blood moves only in one direction…Forward
Blood flows though the valves as a result of pressure changes

19. Roche

20. The Cardiac Cycle
Refers to the repeated pattern of contraction and relaxation of the heart.
Phase of contraction is called systole,
Phase of relaxation is called diastole
The heart has a two step pumping action: the atria contract simultaneously, followed approx seconds later by the ventricles.

21. The Cardiac cycle cycle
5. Ventricles contract, about two thirds of the volume they contain is ejected, leaving one third called the end systolic volume
cycle
1. Atria fill with blood
4. Atria contract
Contributing approx 20%
To end diastolic volume
2.AV valve opens when
pressure in atria exceeds ventricle
3. Blood flows from atria
to ventricles through
open AV valve. This
contributes approx 80% of
end diastolic volume
The Cardiac cycle

22. The Hearts conduction pathway

23. Nerve supply to the heart
The heart is influenced by autonomic nerves originating in the cardiovascular centre in the medulla oblongata
Consisting of sympathetic and parasympathetic nerves with antagonistic effects
The vagus nerves (parasympathetic) supply the SA node, AV node and atrial muscle. Parasympathetic stimulation decreases HR and force of contraction
Sympathetic nerves supply the SA node, AV node and the myocardium of the atria and ventricles. Sympathetic stimulation increases HR and force of contraction

24. Factors affecting Heart Rate
Gender
Autonomic nerve activity
Age
Circulating hormones e.g adrenaline, thyroxine
Activity and exercise
Temperature
The baroreceptor reflex
Emotional states
Waugh and Grant (2006)

25. Summary
The heart is a four chambered pump, which is effectively two pumps working together
The heart contains valves which function to ensure no backflow of blood
The wall of the heart is made up of the following layers: epicardium, pericardium, myocardium, endocardium
The heart has ‘autorhythmicity’ it will beat without outside nervous input
The heart has a specialist conduction pathway- ensuring a smooth coordinated contraction,
Cardiac muscle contains large numbers of mitochondria, and the heart has an excellent blood supply

26. Blood vessels
“ a tubular network throughout the body that permits blood to flow from the heart to all living cells of the body and then back to the heart. Blood leaving the heart passes through vessels of progressively smaller diameters, referred to as arteries, arterioles, and capillaries. Capillaries are microscopic vessels that join the arterial flow to the venous flow. Blood returning to the heart passes through vessels of progressively larger diameters, called venules and veins” Fox (2004) p 390

27. Blood vessel structure
Walls of arteries and veins are composed of three coats or tunics:
Tunica externa (composed of connective tissue)
Tunica media (composed of primarily of smooth muscle)
Tunica intima or interna (composed of three distinct layers, a) endothelium, b) basement membrane, c) internal elastic lamina)

28. Blood vessel structure

29. Differences between arteries and veins

30. Why do we have different types of blood vessel?
Large arteries e.g. aorta are elastic arteries
Smaller arteries are resistance arteries
Capillaries can be continuous, fenestrated or discontinuous, exchange takes place in these vessels
Veins are the capacity vessels, approx 64% of blood is here

31. Blood flow through the vessels
vessels is directly
proportional to the
difference in pressure
between the ends
of the tube

32. Blood flow through the vessels
Is inversely proportional to the resistance in the vessels.
Resistance- determined by blood viscosity, vessel length & vessel radius.
Blood viscosity & vessel length rarely change, radius can be changed by vasoconstriction (reducing radius) or vasodilation (increasing radius)

33. Blood flow through the vessels

34. Blood flow through vessels
Normally laminar, with the blood components arranged in layers
The plasma forms the outer layer & slides smoothly along the endothelium
Blood cells form the ‘axial’ layer in the centre of the blood stream
This allows the blood to flow smoothly, layers slide over each other, axial part moves fastest.

35. Blood flow through vessels
When we take a blood pressure the sounds we here are caused by turbulent flow of blood
Turbulent flow -caused by change in vessel diameter, increase in velocity, & low blood viscosity