Cardiovascular Physiology

Definition of Terms.

‘Cardio’ means ‘Heart’

‘Vascular’ means ‘Blood vessels’

Cardiovascular system is a closed system of the heart (which pumps blood) and blood vessels (which allow blood to circulate to all parts of the body). 

Various components of the Cardiovascular System and their Functions.

 The Heart 

Muscular organ that pumps blood throughout the body. 

Generates and propagates the cardiac electrical impulses

 Arteries

Transports blood under high pressure and maintain blood

flow at high velocities

 Arterioles

Maintain blood flow in response to tissue demand

 Capillaries

Exchange water, gases, nutrients, hormones, cytokines and

other substances between the vascular system and

interstitium.

 Venules

Transport blood from capillaries into veins

 Veins

Transport blood under low pressure from venules into heart;

also serve as controllable blood reservoir

THE HEART

 Heart is a muscular organ that pumps blood

throughout the circulatory system.

 It weighs about 250-350grams

 Heart is located in the middle mediastinum i.e.

in between the lungs.

 It is about the size of the owner’s fist.

The Coverings of the Heart.

 Pericardium –it is a thick, membranous, fluid

filled sac which encloses, protects and nourishes the heart. The roots of the vessels that enter and leave the heart is also covered by the

pericardium.

- Outer Parietal pericardium

- Inner Visceral pericardium

- Serous fluid fills the space between the layers of

pericardium. The fluid is about 30mL.

Functions of the Pericardium

- Pericardium protects the heart from trauma, shock and stress

- Protects the heart from infections from lungs

- It supports the heart and anchors it to the mediastinum so it doesn’t move within the body.

- It lubricates the heart and prevents overloading.

Layers of the Heart

 Epicardium- Outside layer

This layer is the viscera pericardium Connective tissue layer

 Myocardium- Middle layer

Mostly cardiac muscle which is responsible for contracting the heart to pump blood.

 Endocardium- Inner layer 

simple squamous epithelium and a thin CT layer that lines the heart chambers and valves that is continuous with the endothelial lining of the blood vessel. 

The Heart Chambers.

 Right and left side act as separate pumps

Four chambers;

 Atria

Receiving chambers

  Right atrium

  Left atrium

 Ventricles

Discharging chambers

  Right ventricle

  Left ventricle

Heart Chambers

 Right Atrium (RA)- right upper chamber- receives blood from body via the superior and inferior vena cava and the coronary sinus- deoxygenated blood

 Left atrium (LA)- left upper heart.- receives oxygenated blood from lungs via the pulmonary veins and sends it to the left ventricle

 Right ventricle- (RV)- right lower chamber- receives blood from right atrium and sends it to the lungs

via pulmonary arteries.

 Left Ventricle (LV)- lower left chamber- receives blood from left atrium and sends it through the aorta

to the body. 

Valves

    Allow blood to flow in only one direction i.e. prevents back flow of blood. There are four of them in two categories.

 Atrioventricular valves – between atrium and ventricle.

1. Bicuspid/mitral valve (left)

2. Tricuspid valve (right)

 Semilunar valves between ventricle and artery

3. Pulmonary valve

4. Aortic valve

Valves 

- Tricuspid valve controls blood flow between the right atrium and ventricle

- Mitral valve controls blood flow between the left atrium and ventricle

- Pulmonary valve controls blood flow from right ventricle into pulmonary artery

- The aortic valve controls blood flow from the left ventricle to the aorta

Blood Vessels: Associated Great Vessels

 Aorta - Leaves left ventricle

 Pulmonary arteries - Leave right ventricle

 Vena cava (superior and inferior) - Enters right atrium

 Pulmonary veins (four) - Enter left atrium 

Substances Transported Within The Cardiovascular System

Blood cells e.g. erythrocytes and leucocytes

Gases such as oxygen and carbon dioxide

Food nutrients e.g. proteins, lipid, glucose, vitamins and minerals

Fluid e.g. water

Electrolytes such as sodium and potassium

Hormones

Cytokines

Waste products e.g. urea

Energy and heat

Clinical Correlates

• PERICARDITIS: Inflammation of the pericardium which may lead to adhesions between the layers or

the buildup of fluid in the pericardial cavity (cardiac tamponade)

• INCOMPETENT VALVE: Causes backflow and repump of blood

• VALVE STENOSIS: Stiffness oh the valve which causes increase contraction of heart muscles hence, increasing heart workload.