1.6 Types, Structure And Functions Of Blood Vessels

Question 1

Arteries

Answer 1

Blood vessels that carry blood away from the heart. With the exception of the pulmonary arteries they carry oxygen-rich blood.
Walls contain several layers of thick elastic fibres and muscle.
Aorta is the largest and it’s thick elastic walls deal with the surge of blood leaving the heart.
Other large arteries leading to the head, arms and legs have a similar structure. As blood enters, they expand and recoil, helping to maintain the flow of blood. This is the pulse that we detect in the neck or the wrist, where these large arteries are close to the surface.
Branch into smaller distributive arteries- muscular walls so they can regulate blood flow to where it is needed- e.g. skin if we are hot, leg muscles if we run, reproductive organs during sex. If they contract too much, blood pressure can harmfully increase. Sensors in the walls normally keep blood pressure under control.

Question 2

Capillaries

Answer 2

Arteries take blood with oxygen and nutrients to capillary beds. Interconnected capillaries surround and interweave between cells and tissues.
Capillary is a microscopic tube with walls only one cell thick covered by a sieve-like basement membrane.
Supply the tissues with oxygen and nutrients whilst removing waste products such as carbon dioxide.

Question 3

Veins

Answer 3

Plasma leaves capillaries and enters small blood vessels known as venules that join together to form larger tubes or veins.
Have large internal diameters or lumens with walls much thinner than arteries that contain less muscle and elastic tissue.
Blood flowing in veins is not under pressure and, with the exception of the pulmonary veins, veins carry deoxygenated blood back to the heart- buried between body muscles so movements of the body help squeeze blood along.
To ensure blood flows in the right direction, veins have valves throughout their length that prevent backflow.
Blockages can cause varicose veins.