Blood & Blood Vessels

—> the human cardiovascular system is a double circulatory system

—> this means that for every complete circulation of the body, the blood passes through the heart twice

Features :

• Thick wall containing lots of smooth muscle and elastin fibres
• to withstand high pressure of blood from the left ventricle of the heart.
• Elastin allows recoil after pulsation of blood as pressure changes
• (higher systolic pressure just after heart has contracted, lower diastolic pressure between contractions).
• Small lumen.

Features :

• thin walls as blood flow has low pressure.
• large lumen to reduce friction to blood flow.
• semi-lunar valves present to prevent back flow of blood.

Features :

• link arteries and veins and run through tissues.
• site of exchange of materials between the blood and tissues by diffusion.
• walls are one endothelial cell thick giving a short diffusion pathway.

—> blood is comprised of 3 different types of cells

—> the liquid they are in is called plasma

• platelets
• fragments of larger cells
• blood clotting and wound repair

• red blood cells
• biconcave shape
• no organelles
• contain haemoglobin
• transport of oxygen

• white blood cells
• contain a nucleus
• protect against pathogens

• straw-yellow liquid
• carries cells
• dissolved oxygen and nutrients

—> is determined by antigens on the cell surface membrane of red blood cells
—> and antibodies in the plasma.

—> normally the antigens and antibodies don’t match

—> could lead to a blood transfusion being incompatible
—> could cause complications if blood groups aren’t matched before.

—> as well as the A and B antigens that can be on the surface of the red blood cells,
—> there’s also D antigens
—> whether they are present or not determines whether you are Rh+ or Rh-.

Rh- = you can have
Rh+ = you can have your own type, O+ & O-