Lecture 26 - Cardiovascular System: Heart and Vessels

Question 1

Name 2 networks of tubes that allow blood to move from heart to peripheral tissues

Answer 1

1. Pulmonary circuit - moves blood from the heart to the lungs and back, picking up oxygen
2. Systemic circuit - moves blood from the heart to all other organs in the body and back, delivering oxygen

These 2 circuits are not directly connected except through the heart

Question 2

How does blood flow?

Answer 2

Unidirectional; heart -> arteries -> capillaries -> veins

Both true for systemic and pulmonary circuits

Question 3

How does smooth muscle in vessel wall allow arteries and veins to alter blood flow?

Answer 3

Diameter change through:

• Vasodilation: relaxation of smooth muscle cells
• Vasoconstriction: contraction of smooth muscle cells reduces lumen diameter

Smooth muscle respond to ANS (sympathetic innervation) and many different hormones

Question 4

Compare the structural differences between the types of blood vessels

Answer 4

Arteries: intermediate lumen diameter, thick smooth muscle layer, tight endothelial layer

Capillaries: smallest lumen diameter, no smooth muscle layer, leaky endothelial layer

Veins: largest lumen diameter, thin smooth muscle layer, tight endothelial layer

Question 5

Where is the heart located?

Answer 5

Thoracic cavity surrounded by the pericardium (double membrane layer with a fluid-filled space; reduces friction during heart movement), which creates the pericardial cavity

Heart is protected by the thoracic cage

Question 6

How does the heart propel blood through blood vessels and describe the function of the different sides of the heart

Answer 6

Pressure gradients

Right side receives blood from the systemic circuits and pushes it into the pulmonary circuit

Left side receives blood from the pulmonary circuit and pushes it into the systemic circuit

Question 7

Describe the cells that make up the heart

Answer 7

Consists of layers of striated cardiac muscle cells - different from skeletal muscles because they don’t have NMJ

Question 8

Describe the tissues that make up the heart from the most outer layer to the most inner layer

Answer 8

1. Pericardium
2. Myocardium
3. Endocardium

Question 9

Describe the chambers of the heart

Answer 9

It has 4 chambers, arranged in pairs. Each chamber can contract, generating pressure

The right atrium is located to the right ventricle, the left atrium is connected to the left ventricle

Question 10

Describe blood flow in the heart chambers

Answer 10

Blood flows from each atrium into the corresponding ventricles, then into arteries

Systemic veins empty into the right atrium, pulmonary veins empty into the left atrium

Question 11

T/F? Blood flows into the arteries and the atria when ventricles contract

Answer 11

False - when ventricles contract, blood only flows into the arteries, not back into the atria

Question 12

How is heart tissue supplied with blood?

Answer 12

Through coronary blood supply (its own arteries and veins), since it has high metabolic demands

Blood vessels of the heart are coronary blood vessels

Question 13

T/F? The pressures in heart chambers and the great arteries varies predictably a single heartbeat (contraction cycle)

Answer 13

True

Question 14

Function of heart valves and what are its 2 sets?

Answer 14

They control the flow of blood between chambers and into arteries. They are fibrous connective tissue structures that open is response to pressure build-up in the proximal chamber

1. Atrioventricular (AV) valves
2. Semilunar (aortic/pulmonary) valves

Question 15

What occurs when heart valves close?

Answer 15

The backflow of blood is prevented. AV valves have chordae tendineae and papullary muscles so they don’t swing back into the atria

Heart valve closing creates an audible sound when the pressure gradient reverses

Question 16

What makes up the conduction system of the heart

Answer 16

It consists of cardiac muscle cells that transmit electrical excitation from the right atrium to the rest of the heart

Question 17

How does the conductions system of the heart work?

Answer 17

Cardiac myocytes must be electrically excited to contract. Since they lack NMJs, the excitation is myogenic

Heart wall coordinates the timing of contraction by a specialized internal conduction system formed from modified cardiac muscle tissue

Question 18

Describe 2 anatomical differences between the 2 sides of the heart

Answer 18

1. The right ventricle has a thinner wall than the left
2. The great vessels of the systemic circuit are larger and thicker than those of the pulmonary circuit

The asymmetries reflect the different sizes (total vessel length and total blood volume) in the systemic circuit compared to the pulmonary circuit

Question 19

Describe the cardiac cycle

Answer 19

1. Relaxation
2. Atria contract - atrial pressure rises
3. Ventricles contract - ventricle pressure rises, AV valves close
4. Relaxation - ventricle pressure falls, SL valves close

NOTE: contraction inc. pressure, causing blood to flow into an area with lower pressure

Question 20

Define systole and diastole

Answer 20

Systole - contraction of a heart chamber

Diastole - relaxation of a heart chamber