Heart & Blood Vessels

What is the role of the heart in the CVS?

It pumps the blood around the body.

What is the role of blood vessels in the CVS?

They transport blood, which carries nutrients, gases, waste products, hormones, immune cells, ect.

What is the pulmonary circuit?

The pathway of blood that moves between the heart & lungs.

What is the systemic circuit?

The pathway of blood that moves between the heart & the rest of the body.

Where in the body is the heart located?

In the mediastinum - behind the sternum and angled slightly to the left.

What is the heart surrounded by?

The perichardium, which consists of fibrous pericardium and serous pericardium.

What is the serous layer of the perichardium?

It consists of the parietal (outer) layer and visceral (inner layer).

What is the function of the pericardium?

1. To protect the heart.

2. Anchor the heart in position.

3. Prevent overfilling of the heart with blood.

4. Fluid within the perichardial fluid provides a ‘friction-free‘ environment.

What are the three layers of the heart?

1. Epicardium.

2. Myocardium.

3. Endocardium.

What is the epicardium?

• Outer layer (visceral perichardium).

• Supports blood vessels and nerves.

What is the myocardium?

• Middle layer.

• Made of cardiac muscle.

What is the endocardium?

• Inner layer

• Made of squamous epithelium - continuous with endothelial linings of blood vessels.

What is the basic structute of the heart?

1. Four chambers.

2. Two sets of valves.

3. 2x atria.

4. 2x ventricles.

5. 2x atrioventricular valves.

6. 2x semilunar valves.

What is the heart seperated by?

An interventricular septum.

What does the right ventricle do?

It pumps blood to the lungs.

What does the left ventricle do?

It pumps blood to the body.

What does pulmonary circulation require?

Lower pressure

What does systemic circulation require?

Higher pressure.

What is the function of valves?

To prevent the backflow of blood.

What are the different AV valves?

• Ticuspid.

• Bicuspid.

Where are the AV valves located?

Between the atria and ventricles.

What are the different SL valves?

• Pulmonary.

• Aortic.

Where are the SL valves located?

Between the ventricles and arteries leaving the heart.

What do valves open and close in response to?

Pressure changes → helps to ensure unidirectional flow.

What are the two heart sounds?

‘Lub‘ and ‘dub‘.

What is ‘lub‘?

The closing of the AV valves/

What is ‘dub‘?

The closing of the SL valves.

What is the role of arteries?

They carry blood away from the heart.

What is the role of the veins?

They carry blood towards the heart.

How many layers (tunicas) do arteries and veins have to their walls?

3: tunica externa, tunica media, tunica intima.

What is the tunica externa?

The outer layer: a connective tissue rich in collagen.

What is the tunica media?

Middle layer: made up of smooth muscle and elastic fibres.

What is the tunica intima?

Inner layer: made up of a simple squamous epithelia.

What are the three types of arteries?

• Elastic.

• Muscular.

• Arterioles.

What are the properties of elastic arteries?

• Elastic or conducting arteries are thick walled, close to the heart.

• Large amounts of elastic tissue.

• Allows for expansion and contraction, causing blood to flow smoothly.

What are the properties of muscular arteries?

• Smaller, branch from the elastic arteries.

• More muscular tunica media → allows blood flow to be controlled.

What are the properties of arterioles?

• Mostly made up of smooth muscle (media) surrounding the endothelium.

• Held together by an outer layer of collagen fibres.

• Smooth muscle → allows regulation of blood flow through vasoconstriction and vasodilation.

What is vasocontriction?

When the smooth muscle in the arterioles is contracted and the lumen of the vessel is smaller so less blood can flow to the capillaries.

What is vasodilation?

When the smooth muscle in the arterioles is relaxed and the lumen of the vessel is larger and more blood can flow to the capillaries.

What is the smallest of the blood vessels?

Capillaries.

What are the properties of capillaries?

• Thin walled → often just the tunica intima (squamous epithelia).

• Provide acces to all of the cells of thebody and are sites of exchange.

• Blood flow is much slower to allow exchange to take place, and capillaries create a large surface area.

What can blood flow through capillaries be regulated according to?

Need.

When open, what can pass into the capillaries?

Nutrients can pass into the surrounding cells and wastes can be removed.

How are venules formed?

By capillaries joined.

How are veins formed?

By venules joining together.

What is the blood pressure in the veins in comparison to the arteries?

It is much lower: the walls of the veins are much thinner.

What are the different mechanisms that aid in the return of blood in the heart.

1. Pressure in the veins is slightly higher than that in the right side of the heart (creates pressure difference).

2. Valves ensure the one way flow of blood.

3. Skeletal muscle pump (when muscles contract, they squeeze on blood vessels, forcing blood to move in the correct direction).

4. Respiratory pump ().

What is a pulse?

The pressure wave felt in an artery that lies close to the surface of the body.

What is the pressure wave in a pulse the result of?

The left ventricle contracting (systolic pressure).

How can you count the heart rate?

By counting the pulse rate?

How does the heart get nourishment?

Through coronary circulation.

What do the coronary arteries divide into?

The left and right coronary arteries.

What does the left coronary artery divide into?

→ Anterioe interventricular artery.

→ Circumflex artery.

What does the right coronary artery divide into?

→ Right marginal artery.

→ Posterior interventricular artery.

Where are the coronary arteries located?

In the epicardium, and they branch inwards to supply the myocardium.

What happens in the coronary veins?

• Venus blood is collected by the cardiac veins.

• These veins join to form the coronary sinus, which empties blood into the right atrium.

What is the structure of the coronary sinus?

It has three large tributaries:

→ Great cardiac vein.

→ Middle cardiac vein.

→ Small cardiac vein.

What do several anterior cardiac veins also do?

Empty directly into the right atrium.

What do the capillaries allow plasma to do?

Leave and enter the surrounding tissue to become interstitial (tissue) fluid. This fluid needs to be returned to the blood to maintain blood volume → the role of the lymphatic system.