生物化学笔记英文

WEEK 1：Overview of the cardiovascular system

Learning Objective

• explain the basic anatomy of the heart and its arrangement into 4 chambers.

• describe the location and function of the heart valves.

• list in sequence the direction of blood flow through the four chambers of the heart.

• appreciate that blood flows in series through the systemic and pulmonary circulations.

• explain what causes fluid to flow through a tube.

• understand the relationship between blood flow, pressure and resistance

• appreci ate the three factors that influence the resistance to flow through a tube.

Why do we have a circulatory system?

distribute nutrients/hormones O2

remove wastes + CO2

thermo regulation

transport antibodies and white blood cells

penile erection

Heart (pump)

Aortic and Pulmonary Valves

∙(semilunar valves)

Allow flow from ventricles into arteries (aorta or pulmonary artery)

∙but prevent backflow from arteries to ventricles

Atrioventricular Valves

∙mitral (bicuspid) valve (between left atrium and ventricle)

∙tricuspid valve (between right atrium and ventricle)

Allow flow from atria into ventricles

∙but prevent flow from ventricles back into atria

Difference in pressure causes flow

Flow is always from region of high pressure to

region of lower pressure

It is the DIFFERENCE in pressure that is important,

not the absolute pressure.

Flow is proportional to the pressure difference

(F P)

Directly proportional if flow is laminar.

What is the main anatomical difference between the femoral artery and

the popliteal artery?

Which artery has the higher peripheral resistance (PR)?

What do you think is the relationship between artery length

andperipheral resistance (to blood flow)?

Changing the radius alters the resistance to flow

Flow through a vessel increases in proportion to the fourth power of the radius of the vessel (Poiseuille’s law).

Viscosity = blood is thicker than water

% volume of blood occupied by red blood cells

Haematocrit = 45% in men

= 42% in women

Men have a slightly higher oxygen carrying capacity of their blood (more haemoglobin)

Athletes sometimes artificially elevate their haematocrit (e.g. with synthetic erythropoietin/EPO or via blood doping). What effect will this have on viscosity and blood flow in arterioles supplying the leg?

Why are athletes so tempted by ‘blood doping’?

Blood viscosity is largely determined by haematocrit:

Haematocrit is usually maintained relatively constant:

- can be abnormally low in anaemia

- abnormally high with severe dehydration or synthetic erythropoietin (EPO/blood doping)