1.2 The heart (structure, blood pressure) --> Part 1

Oxygenated blood

The state of the blood when oxygen has been absorbed into red blood cells and binds with haemoglobin molecules.

Deoxygenated blood

The state of the blood when much of the oxygen has left the red blood cells to be used by other cells for respiration.

Normal adult heart bpm

60 - 100 bpm

Double Circulatory System

The blood passes through the heart twice during one complete circuit of the body, via two separate loops.

The two circuits involved in the blood circulatory system

• Pulmonary circuit

• Systemic circuit

Pulmonary Circuit

Carries blood from heart to lungs and back

Systemic circuit

Carries blood from heart to body and back

Function of the double circulatory system

It allows oxygenated blood to be pumped at a much higher pressure than deoxygenated blood, ensuring rapid delivery to tissues

Major arteries of the heart

• Aorta

• Pulmonary artery

• Coronary arteries

Major veins of the heart

• Superior Vena Cava

• Inferior Vena Cava

• Pulmonary Veins

• Cardiac Veins (Coronary Veins)

The right side of the heart

Handles blood returning from the body that needs oxygen

The left side of the heart

Handles oxygenated blood returning from the lungs for systemic distribution

The blood vessels in the heart

• Superior vena cava

• Inferior vena cava

• Pulmonary veins

• Pulmonary artery

• Aorta (artery)

Superior vena cava

Carries deoxygenated blood from the upper body to the right atrium

Inferior vena cava

Transports deoxygenated blood from the lower body to the right atrium

Pulmonary veins

Carries oxygenated blood from the lungs to the left atrium

Pulmonary artery

Carries deoxygenated blood from the right ventricle to the lungs

Aorta

The largest artery, which supplies oxygenated blood from the left ventricle to all parts of the body

How the aorta supplies oxygenated blood to all organs of the body

It has smaller arteries that branch off it, to supply blood to the different organs of the body

The number of chambers in the heart

Four

The chambers of the heart

• Right atrium

• Left atrium

• Right ventricle

• Left ventricle

Right atrium

Receives deoxygenated blood from the vena cava, which then passes into the right ventricle.

Left atrium

Receives oxygenated blood from the pulmonary veins, which then passes into the left ventricle.

Right ventricle

Receives blood from the right atrium and contracts to pump deoxygenated blood out of the heart, through the pulmonary artery, to the lungs.

Left ventricle

Receives blood from the left atrium and contracts to pump oxygenated blood out of the heart, through the aorta to the rest of the body.

Singular form of atriums

Atrium

Another plural form of atrium

Atria

Valves

It ensures a one-way blood flow, preventing blood backflow by responding to pressure changes.

The two main types of Valves

• Atrioventricular (AV) valves

• Semilunar (SL) valves

Atrioventricular valves

Heart valves located between an atrium and the ventricle below it

The two Atrioventricular valves

• Tricuspid valve

• Bicuspid valve

Tricuspid valve

Located between the right atrium and right ventricle

Function of the tricuspid valve

Prevents backflow of blood from the right ventricle to the right atrium, so that it goes through the pulmonary artery and to the lungs

Bicuspid valve

Located between the left atrium

Function of the bicuspid valve

Prevents backflow of blood from the left ventricle to the left atrium, so that it goes through the aorta and around the body

Another name for bicuspid valve

Mitral valve

Semilunar valves

Located at the base of the main arteries and consist of three pockets of connective tissue, which open to allow forward blood flow and close tightly when blood tries to flow the wrong way (preventing backflow into the ventricles).

The two Semilunar valves

• Aortic valve

• Pulmonary valve

Aortic valve

Located at the base of the aorta

Function of the aortic valve

Prevents backflow from the aorta back, into the left ventricle

Pulmonary valve

Located at the base of the pulmonary artery

Function of the pulmonary valve

Prevents backflow from the pulmonary artery, back into the right ventricle

Septum

Thick wall of tissue that separates the right and left side of the heart

Function of the septum

Prevents oxygenated blood from the left side of the heart, mixing with deoxygenated blood from the right side of the heart

What it means for the heart muscle to be myogenic

That the heart generates its own pulses

Myocardium

The thick, muscular middle layer of the heart wall, that contracts to pump blood

Cardiac tissues

Involuntary muscle throughout the walls of the heart

Function of the cardiac tissues

Responsible for the heart’s ability to contract rhythmically and pump blood throughout the heart

Coronary arteries

They supply the myocardium with oxygenated blood

Cardiac Veins

They remove waste CO₂

The cardiac cycle

The processes which occur during one beat of the heart

What is involved in the cardiac cycle

It involves:

• The parts of the heart that are contracting or relaxing

• The direction in which the blood is flowing

• Which heart valves are open or closed at each stage

Key phases of the cardiac cycle

• Atrial systole

• Ventricular systole

• Diastole

Diastole

When the heart is relaxing and filling with blood.

Systole

When the heart is contracting and pushing blood into the arteries.

Diastole

• The atria and ventricles relax.

• Then the SL valves at the base of the two arteries shut, preventing backflow into the ventricles.

• Simultaneously, blood flows into both atria from the vena cava and pulmonary veins.

• Then the AV valves open, to allow some blood flow from the atria to the ventricles.

Atrial Systole

• The atria contract, pushing blood into the ventricles that are relaxed.

• The SL valves at the base of the two arteries stay closed.

Ventricular Systole

• The ventricles are full so they contract.

• The pressure of the blood closes the AV valves, preventing backflow of blood into the atria.

• The SL valves open.

• Blood is then forced past the open SL valves and into the aorta and pulmonary arteries.

Lub

This is the sound of the AV valves when they shut, producing the first heart sound.

Dub

This is the sound of the SL valves when they shut, producing the second heart sound.

Blood pressure

A measure of the force that the heart uses to pump blood around the body.

How blood pressure is measured

Recording the two types of blood pressure

Systolic pressure

The higher number and measures the pressure in the arteries when the heart pumps blood.

What causes systolic pressure to rise

Systolic phase

Diastolic pressure

The lower number and measures the pressure in the arteries when the heart relaxes between heart beats.

What causes diastolic pressure to rise

Diastolic phase

Low range blood pressure

70/40 to 90/60

Ideal blood pressure

90/60 to 120/80

Pre-high blood pressure

120/80 to 140/90

High blood pressure

140/90 to 190/100

Another name for low blood pressure

Hypotension

Another name for high blood pressure

Hypertension