The-heart-and-cardio-vascular-system

Published on 28th November 2016

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
o    Capillaries
o    Veins
o    Arteries
•    Blood

THE HEART
•    Cardiac Muscle
o    Self stimulating
o    Never fatigues
o    Receives own blood supply via coronary arteries
•    Double Pump
o    Left side pumps blood around body (systemic circulation)
o    Right side pumps blood to lungs (pulmonary circulation)
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
o    Transport oxygen to tissues
o    Formed in bone marrow
o    No nucleus
o    Lifespan of 120 days
o    4.8-5.4 million per mm3
o    Require iron, vitamin C, vitamin B12, folic acid for formation
•    White cells called LEUCOCYTES
o    Defence and protection
o    Ingest bacteria – Phagocytes
o    Formed mainly in bone marrow, except lymphocytes (formed in lymph nodes and spleen)
o    Lifespan hours - months
o    Numbers increase during period of infection, 5,000-10,000 per mm3
 

•    Platelets also called THROMBOCYTES
o    Prevent haemorrhage
o    Repair damaged blood vessels
o    Formed in bone marrow
o    Lifespan about four days
o    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:
o    Greatest as left ventricle contracts (systole)
o    Lowest as left ventricle relaxes (diastole)

•    Blood pressure affected by:
o    Cardiac output
o    Blood volume
o    Blood viscosity
o    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

 

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