The Human Heart

Question 1

What is the heart?

Answer 1

• muscular organ the size of your fist and located in the middle of the chest
• breastbone protects the front, spine protects the back
• surrounded by the pericardium (fluid-filled sac that anchors heart,opaque and manages pressure…

Question 2

4 chambers of the heart

Answer 2

2 types of chambers:

Right atrium, left atrium
right ventricle, left ventricle

Blood flows from atrium to ventricle (top to bottom)

Question 3

Heart is called the “double pump” because…?

Answer 3

The right side pumps blood to the lungs, the left pumps blood to the body

Question 4

Mammalian Circulatory System

Answer 4

Cardiac/coronary circulation: high demand for oxygen and nutrients, hearts own supply of blood vessels

Pulmonary Circulation: pumps deoxygenated blood to the lungs, returns oxygenated blood to the heart

Systemic circulation: pumps blood around the body, returns it to the heart

If one branch is blocked it can cause a heart attack

Question 5

How the heart pumps blood

Answer 5

1. Deoxygenated blood from the body enters the Right Atrium thru Superior and Inferior vena cava
2. … and blood flows into the Right Ventricle thru tricuspid valve
3. The right ventricle pumps the blood into the lungs (via Pulmonary Arteries)
4. From the lungs, oxygen-rich blood returns to Left Atrium (via Pulmonary veins)…
5. …and flows into the Left Ventricle thru mitral valve
6. The left ventricle pumps oxygen-rich blood into the body via the Aorta.

Question 6

4 heart valves

Answer 6

2 Atrioventricular valves – prevent blood from entering atria when the heart beats (tricuspid (right side) and bicuspid/mitral (left side) valves)

Aortic valve – (semilunar valve) prevents blood from moving from the aorta into the left ventricle when the heart is NOT beating

Pulmonary valve – (semilunar valve) prevents blood from moving from the pulmonary artery into the right ventricle when the heart is NOT beating

Question 7

How does the heartbeat work

Answer 7

Sounds like “lubb-dubb”

Lubb:
first heart sound
atrioventricular valves closing as ventricles begin to contract

Dubb:
second heart sound
pulmonary and aortic valves closing as ventricles relax

Measured using a Stethoscope

Question 8

Why listen to the heartbeat

Answer 8

• listen for abnormal sounds (arrhythmias)
• heart valve(s) failing to close properly can be heard as the sound of blood leaks past through the valve = heart murmur

Question 9

The heartbeat definition

Answer 9

• Heartbeat initiated in cluster of cells in RA called sinoatrial node (SA)
• Gives signals to set normal rhythm of heartbeat (pacemaker)
• Signals reach atrioventricular node (AV)
• From AV node special conducting fibres called Purkinje fibres run down septum and throughout heart’s muscles cells

Question 10

Electrocardiograph (EKG)

Answer 10

• Heartbeat is electrically stimulated
• Electrocardiograph detects electrical activity of heart through electrodes placed on body’s surface
• ECG tracing shows strength and duration of electrical signals from heart.