The Cardiovascular System

Published on 14th April 2018

THE CARDIOVASCULAR SYSTEM

FUNCTION

Transport system carrying nutrient, gases, hormones and waste products to and from the body tissues
Helps prevent disease
Helps regulate body temperature

ANATOMY

Heart
Vessels
- Capillaries
- Veins
- Arteries
Blood

THE HEART

Cardiac Muscle
- Self stimulating
- Never fatigues
- Receives own blood supply via coronary arteries
Double Pump
- Left side pumps blood around body (systemic circulation)
- Right side pumps blood to lungs (pulmonary circulation)

THE STRUCTURE OF THE HEART

Four chambers
- Right and left atria
- Right and left ventricles
Valves
Septum
Pericardium
Myocardium
Endocardium

ARTERIES

Carry blood away from the heart
Carry oxygenated blood- except pulmonary artery
Thick-walled, muscular and elastic tissue
Under high pressure
Divide into smaller vessels called arterioles, and then into capillaries

CAPILLARIES

Tiny vessels
Permeable
Exchange of gases/nutrients and waste materials
Unite to form venules and venules form veins

VEINS

Return blood from tissues to heart
Carry de-oxygenated blood - except pulmonary veins
Thin walls
Contain valves
Under low pressure

BLOOD

Blood consists of cells suspended in a clear fluid called plasma

COMPOSITION OF BLOOD

PLASMA = 55% of blood volume

Plasma is made up of 90% water +

Plasma Proteins Salts Fats

Enzymes Urea/uric acid Hormones

Amino Acids Vitamins Glucose

Minerals Gases

CELLS

Red cells called ERYTHROCYTES
- Transport oxygen to tissues
- Formed in bone marrow
- No nucleus
- Lifespan of 120 days
- 4.8-5.4 million per mm3
- Require iron, vitamin C, vitamin B12, folic acid for formation
White cells called LEUCOCYTES
- Defence and protection
- Ingest bacteria – Phagocytes
- Formed mainly in bone marrow, except lymphocytes (formed in lymph nodes and spleen)
- Lifespan hours - months
- Numbers increase during period of infection, 5,000-10,000 per mm3
Platelets also called THROMBOCYTES
- Prevent haemorrhage
- Repair damaged blood vessels
- Formed in bone marrow
- Lifespan about four days
- 250,000-5000,000 per mm3

BLOOD PRESSURE

As blood flows it exerts pressure on the walls of the blood vessels.

Varies rhythmically with heartbeat:
- Greatest as left ventricle contracts (systole)
- Lowest as left ventricle relaxes (diastole)
Blood pressure affected by:
- Cardiac output
- Blood volume
- Blood viscosity
- Blood vessel size and elasticity

The rate at which the heart beats can be determined by taking the pulse. Normal rates in adults at rest are between 65–75 but obviously vary according to many things such as emotion, general health and stimulants such as caffeine. Very fit people such as athletes may well have resting pulse rates below 60

Additional Information for VTCT Qualification

Sometimes during bodily processes there needs to be a diversion of blood away from the areas not involved in order to provide a better blood supply to those areas that are active.
By causing the small arterioles to constrict or dilate a considerable alteration in blood flow to the area they supply occurs, e.g. during digestion blood is diverted to those organs involved such as the stomach and intestines and away from areas such as the skeletal muscles. This is why exercising too soon after eating may cause cramps.

Erythema

Erythema is the reddening of the skin caused by vasodilation in the arterioles which then causes congestion in the tiny capillaries.
It can happen during massage but also due to exercise, infection, allergies and radiotherapy treatment

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