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
What are capillaries?
Site of gas exchange
Connect veins and arteries
What are some adaptations of capillaries?
Thin walls for diffusion
Slow blood flow
Small 8um diameter
2 way exchange
What are the types of capillaries?
Continuous
Fenestrated
Sinusoidal
What are continuous capillaries?
Most capillaries
In skeletal and smooth muscle, connective tissue and lungs
What are fenestrated capillaries?
They have pores that penetrate the endothelial lining
Do rapid exchange of water or large solutes
Involved in absorption
What are sinusoidal capillaries?
Have spaces between endothelial cell
Have incomplete or absent basement membrane
Do exchange of large solutes like plasma proteins
Specialised lining cells
Blood moves very slowly
What are some structural adaptations of veins?
Thin walls
Predominant tunica externa
Valves to help blood flow
Easily distensible
What is the musculovenous pump?
A collection of skeletal muscles that help blood flow and increase blood return to the heart
What is the distribution of blood across the circulatory system?
70% - systemic venous system
30% - everything else, such as heart, pulmonary circuit, systemic arterial system, systemic capillaries
What is the transverse plane?
A cut horizontally, eg in humans separate chest from stomach
What is the coronal plane?
Separates the front and back, eg in humans separates the chest from the back
What is the midsagittal plane?
Separates the two sides, eg in humans separating the left half of the body from the right half
