Blood Vessels Flashcards
What blood vessel has a different structure than the rest?
Capillaries
What is the normal structure of the blood vessels?
Consists of a three layered wall
What are the three walls?
Tunica intima (inner most layer), tunica media (middle layer) and tunica Adventitia (outer layer)
What does the intima layer consist of?
A single sheet of endothelial cells resting on a thin layer of connective tissue
What is the main barrier to plasma proteins?
Endothelial and secretes many vasoactive products
Describe the media
Consists of a later of smooth muscle of varying thickness in a matrix of elastin and collagen
What does the media later supply?
Mechanical strength, elasticity and contractile power to the vessel
Describe the adventitia
A connective tissue sheath with no distinct outer boarder
What is the main role of the adventitia?
To tether vessels loosely in place
What is found in large arteries?
Contains a blood vessel network called the vasa vasorum which is responsible for nourishing the media
What do some large arteries penetrate?
The outer tunica media
What do some large vessels also contain?
Small diameter nocicpetive sensory fibres and sympathetic nerve plexi
What are nociceptive sensory fibres?
A receptor (like the skin) for nocicpetive stimuli (a pain sense organ)
Describe elastic arteries
Diameter of 1-2cm, walls are very distensible
How are the walls distensible in elastic arteries?
The walls expand during systole to receive the stroke volume of ventricular ejection and recoil during diastole to create an almost constant flow in more distal tissues
What is diastolic blood pressure?
The blood pressure created by the elastic recoil
What are some examples of elastic arteries?
Aorta, pulmonary artery and iliac arteries
Describe the conduit (muscular) arteries
Diameter 0.1-1cm, tunica media is thicker relative to the lumen of the vessels, media contains more smooth muscle and are highly innervated by the autonomic nervous system
Why is it good that the media contains smooth muscle?
As it prevents collapse at sharp ends such as the elbow
What do muscular arteries play a big role in?
Limitation of blood loss in major trauma
What are examples of muscular arteries?
Radial, cerebral and coronary arteries
Describe arterioles
Diameter less than 0.1 and are the main site of blood flow regulation to tissues
Why are arterioles the main resistance vessels?
Because of their narrow lumen and large numbers of
Describe proximal arterioles
Have many layers of smooth muscle and are richly innervated by sympathetic (vasoconstrictor) nerve fibres
