THE CARDIOVASCULAR SYSTEM

Question 1

Structure

Answer 1

The heart is a muscular tube in the size of a fist located in the thoracic cavity. The heart consists of three

layers:
1. Inner endocardium.
2. Middle thick myocardium (a cardiac muscle).
3. Outer covering epicardium.

**In addition, the heart is surrounded by a sack called pericardium that contains pericardial fluid.

Question 2

The heart is divided into four different chambers:

Answer 2

1. The right atrium.
2. The left atrium.
3. The right ventricle.
4. The left ventricle.

Question 3

The separation is done by walls called

Answer 3

septums:
* Atrial septum – the septum that separates between the two atria.

• Ventricular septum – the septum that separates between the two ventricle.
• Atrioventricular septum – the septum that separates between the atria (upper chambers) to the
  ventricle (lower chambers)

Question 4

Valves

Answer 4

The heart contains four valves that allow unidirectional blood flows.

1. Tricuspid valve – allow blood flow from the right atrium to the right ventricle
2. Bicuspid (mitral) valve – allows blood flow from the left atria to the left ventricle.
3. Pulmonary valve – allows blood flow from the right ventricle to the pulmonary artery.
4. Aortic valve – allows blood flow from the left ventricle to the aorta.

**The pulmonary and the aortic valves are often called semi lunar valves, due to their structure.

Question 5

Blood Vessels

Answer 5

Blood vessels are connected to the blood. Each heart chamber is directly connected to one main vessel.
1. Aorta – the main artery of the body. Carrying oxygenated blood from the left ventricle. Emerges
from the left ventricle.
2. Pulmonary artery – the only artery in adults that carries deoxygenated blood. Originating from the
right ventricle.
3. Coronary Arteries – Left and right arteries that originate from the aorta and carry oxygenated
blood to the heart itself
4. Vena cava – Veins that collect blood from the body and drain it to the right atrium. There are two
types of vena cava:
* Superior – collects deoxidized blood from the upper
part of the body and returns it back to the right
atrium.
* Inferior – collects deoxidized blood from the lower
part of the body and returns it back to
the right atrium.
5. Pulmonary vein – leading blood from the lungs to the left atrium it is the only vein with oxygenated
blood

Question 6

2 types of blood circulation:

Answer 6

1. The pulmonary circulation

2. The systemic circulation

Question 7

The pulmonary circulation

Answer 7

A circulation between the heart and the lungs. Involving the right ventricle sending deoxygenated blood into the lungs and the left atrium receiving oxygenated blood from the lungs.

Question 8

The systemic circulation

Answer 8

A circulation between the heart and the body. Involving the left ventricle sending oxygenated blood to the body and the right atrium receiving deoxygenated from the body.

Question 9

Heart Phases

Answer 9

The heart is working in two phases:

1. Systole – indicating ventricular contraction (𝑏𝑙𝑜𝑜𝑑 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑖𝑠 120 𝑚𝑚𝐻𝑔).
2. Diastole – indicating ventricular relaxation (𝑏𝑙𝑜𝑜𝑑 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑖𝑠 80 𝑚𝑚𝐻𝑔)..

Question 10

During systole

Answer 10

The ventricles are contracting and blood is pushed to the aorta and the pulmonary artery.
At this stage, the semi lunar valves open, while the bicuspid and tricuspid close.

Question 11

During diastole

Answer 11

the ventricles relax and create a negative pressure that drains the blood from the atriums to the ventricles.
During diastole semi lunar valve are closed, while bicuspid and tricuspid valves open.

Question 12

Conducting System of the Heart

Answer 12

Like every muscle, the cardiac muscle requires a signal to contract. This signal is originating from the pace
make – the sinoatrial node. Found in the right atrium. The signal is then traveling through both atriums and collected by the atrioventricular node. The 𝐴.𝑉. node is sending the signal throughout the ventricles by bundle of his, the right and left bundle branches and ending in the 𝑝𝑢𝑟𝑘𝑖𝑛𝑗𝑒 fibres.

**The conducting system of the heart is made of modified cardiac tissue. It is not a nerve tissue

Question 13

Innervation of the Heart

Answer 13

The heart is affected by two aspects of the nerve system:

1. Sympathetic nerve system a.k.a. the “the fight or flight” respond. Innervating the sinoatrial node
   to increase the heart rate and the heart muscle to increase contractility.
2. Parasympathetic nerve system a.k.a. “rest and digest” respond. Innervation the sinoatrial node
   only to decrease heart rate during resting state.

Question 14

Good to know 9 facts

Answer 14

*The heart’s rate is 72 beats per minutes.
* The cardiac cycle is 0.8 seconds – 0.3 for systole, and 0.5 for diastole.
* The heart stroke volume is 80-100 ml of blood a second – up to 5-6 litres a minutes.
* The cardiac output is 4-8 litters.
* Blood pressure is 120/80 𝑚𝑚𝐻𝑔.
* A thrombus in the first branch of the aortic arch would affect the flow of blood to the right side of the
head, neck and the right upper harm.
* Hypocapnia – deficiency in carbon dioxide.
* Hypercapnia – abnormal elevation of carbon dioxide.
* Hypoxia – deficiency in oxygen.

Question 15

Pathology

Answer 15

1. Myocardial Infraction – “heart attack” – blood flow to the heart stops due to prolonged Ischemia (restriction of 𝑂2 to cardiac tissues) that causes irreversible necrosis (cell death of heart muscle)
2. Heart Arrhythmia – irregular heart beat:
   * Tachycardia – above 100 beats per minutes at rest.
   * Bradycardia - low heartbeat (below 60 beats per minutes at rest).
3. Inflammations:
   * Myocarditis – inflammation of myocardium (middle layer of the heart).
   * Endocarditis – inflammation of endocardium (inner layer of the heart).
   * Epicarditis – inflammation of epicardium (outer layer of the heart).
   * Pericarditis – inflammation of pericardium.