Consists of 3 parts:

• heart

• blood vessels

• blood

Blood Vessels

Arteries

• copy part of fig. 19.6p. 141

• carry blood away from the heart

• thick muscular layer in wall to withstand high pressures

• pulsate due to pumping of heart

Arterioles – smaller branches of arteries

Venules – smaller branches of veins

Capillaries

• wall only 1 cell thick

•Allow exchange of materials between blood and tissue

• a network covers each organ

Veins

• copy part of fig. 19.6 p.141

• carry blood towards the heart

• thin muscular layer as blood is at lower pressure

• wide lumen to reduce resistance to blood flow

• valves present to prevent backflow of blood

Tissue Fluid

• blood arrives at arteriole side of capillary bed at high pressure

• blood is then forced into capillaries

• causes some plasma to be squeezed out of capillaries => pressure filtration

• liquid is called tissue fluid

• every cell bathed in tissue fluid

• tissue fluid contains dissolved substances, e.g., glucose ions, no protein

• nutrients taken up by cell, waste from cell dissolved in tissue fluid

• tissue fluid returns to blood vessels by osmosis => higher water concentration than plasma due to lack of protein

• some tissue fluid taken up by lymphatic vessels to become lymph (see later)

The Hearthttp://texasheart.org/HIC/Anatomy/Anatomy.cfm

• stick in diagram

• pumps blood around the body

• 4 chambers; 2 atria, and 2 ventricles

• right atrium receives deoxygenated blood from body via venae cava

• left atrium receives oxygenated blood from lungs via pulmonary vein

• both atria contract, pumping blood to ventricles

• right ventricle pumps deoxygenated blood to lungs via pulmonary artery

• left ventricle pumps blood to body via aorta

• left ventricle has a thick muscular wall, as it pumps blood to the whole body

• right ventricle has thinner wall as it is pumping a short distance to the lungs

• heart has 4 valves to prevent the backflow of blood

http://www.vesalius.com/cfoli_frms.asp?VID=200&StartFrame=7&tnVID=363

Heart Valves

• atrio-ventricular (AV) valves – between atria and ventricles

• tricuspid valve between right atrium and ventricle (made of 3 flaps)

• bicuspid (mitral) valve between left atrium and ventricle (made of 2 flaps)

• semi-lunar valves are between the ventricles, and the pulmonary artery, and the aorta

Circulation

Pulmonary circulation – blood circulated heart to lungs to heart

Systemic circulation – blood circulated heart to body to heart

Aorta branches to supply oxygenated blood to all body parts.

Stick in and label circulation diagram

Coronary Heart Disease

Any disease resulting in blockage or restriction of coronary blood supply to the heart.Atherosclerosis (fig. 19.15 p.146)

• formation of atheroma in arteries

• atheroma is a fatty plaque of lipid and cholesterol, hardened by calcium

• reduces blood flowhttp://www.vesalius.com/cfoli_frms.asp?VID=200&StartFrame=10&tnVID=363

Angina

• crushing pain in centre of chest

• caused by narrowing of coronary arteries as a result of atherosclerosis

• if heart beat increases, blood is forced through narrow arteries which results in angina

Coronary Thrombosis (fig. 19.16 p.147)

• atheromas make surface uneven

• blood clot can form

• if the clot breaks loose and gets trapped, causing restricted blood flow, or blockage

=> coronary thrombosis (heart attack)

• coronary bypass can help – aorta joined to coronary artery by part of vein from leg (fig. 19.17 p.147)

Reduce risk by:

• no smoking

• less stress

• avoid excessive cholesterol and saturated fats

• normal weight

• exercise

Cardiac Cycle

• pattern of contraction and relaxation

Systole – contraction

Diastole - relaxation

http://anatimation.com/cardiac/intro.html

1. Atrial systole – atria contract, AV valves open, 0.1s

2. Ventricular systole – AV valves close, ventricles contract, SL valves open, 0.3s

3. Ventricular diastole – ventricles relaxed, SL valves close, 0.4s

Whole cycle – 0.8s

1. AV valves open due to high blood pressure (BP) in atria

2. As BP in ventricles exceeds that of atria, AV valves close – ‘lubb’ sound

3. SL valves open due to high BP in ventricles

4. As BP in arteries exceeds that of ventricles, SL valves close – ‘dupp’ sound

Conducting System of the Hearthttp://www.vesalius.com/cfoli_frms.asp?VID=200&StartFrame=4&tnVID=363

• pacemaker controls heart beat – sino-atrial node (SAN)

• SAN initiates electrical impulse, which causes contraction

• impulse spreads from SAN across atria causing atrial systole

• impulse picked up by atrio-ventricular node (AVN)

• impulses pass from AVN, down conducting fibres to heart apex

• impulse spreads upwards across ventricles causing ventricular systole

•http://anatimation.com/cardiac/intro.html

Electrocardiogram (ECG)

• pattern of electrical activity of the heart

•Sketch fig. 20.6 p.152

P wave = electrical impulse spreading across atria

QRS complex – electrical impulse spreading across ventricles

T wave – electrical recovery of ventricles

Blood Pressure

• generated by ventricle contraction

• related to blood volume in arteries – increased volume = increased pressure

• arterial pressure varies as heart goes through systole and diastole

• systolic blood pressure – pressure when ventricles contract – 120mmHg

• diastolic blood pressure – pressure when ventricles relaxed – 80mmHg

• decreases as blood moves into arterioles, and further as it moves to capillaries, venules and veins

• valves in veins prevent backflow

• elastic walls of arteries can stretch and recoil to ease blood flow (fig. 20.9 p.153)

• measured using a sphygmomanometer

• blood also has to overcome resistance caused by friction between blood and vessels (peripheral resistance)

• increased rate and force of contraction, can increase blood pressure

• stress and excess salt can raise blood pressure

• high pressure can lead to:

1. increased risk of atherosclerosis

2. damaged blood vessels (stroke if in cerebrum)