Lecture 5 - Blood vessels Flashcards
What are some key features blood vessels must have?
Resilience
Flexibility
Always remain open
What is the structure of all blood vessels?
They have the lumen, tunica intima, tunica media and tunica adventitia
What is the tunica intima?
Innermost layer of the blood vessel
Has a simple squamous epithelium
Subendothelial connective tissue, has tiny blood vessels in it that feed the endothelium
What is the tunica media?
Middle layer of the layers of the blood vessel
Smooth muscle fibres in loose connective tissue
May have elastic fibres
What is the tunica adventitia?
Outer layer of blood vessel
Made up of connective tissue
Merges with the surrounding connective tissue
May contain vaso vasorum
What are vaso vasorum?
Tiny blood vessels that supply larger blood vessels
What are some features of arteries?
Have a small lumen
Thick outer wall to withstand high pressure
What are the different types of arteries?
Elastic
Muscular
Arterioles
What are elastic arteries?
EG aorta
Diameter up to 2.5 cm
Withstand pressure changes
Thick tunica media
Many elastic fibres and few smooth muscle cells
What are muscular arteries?
Known as distributing arteries
eg Brachial
Diameter from 0.5mm-0.4 cm
Distribute blood to muscles and organs
Do vasodilation and vasoconstriction to control rate of blood flow
Lots of smooth muscle cells in tunica media
Has distinct internal and external elastic laminae
What are arterioles?
Control blood flow to organs
Blood pressure control
Diameter of around 30um
Do vasoconstriction and vasodilation
One or two layers of smooth muscle cells in tunica media
Poorly defined tunica externa
What are some components of capillaries?
Capillary beds
Precapillary sphincter
Arteriovenous anastomoses
What are capillary beds?
Capillaries are organised into groups, capillary beds
One capillary bed is supplied by one metarteriole
What is the precapillary sphincter?
Guard the entrance to a capillary to further regulate blood flow
Each capillary has one
What is the arteriovenous anastomoses?
Form direct communication between the arteriole and the venule
When dilated, blood bypasses capillary bed and flows straight into venous circulation