Blood Vessels Flashcards
How many different types of capillaries are there?
3 types
What are the three different types of capillaries?
Continuous
Fenestrated
Sinusoidal
What is the most common type of capillary?
Continuous capillaries
Write a note on continuous capillaries.
4
No pores
No gaps
Tight junctions between cells
Diffusion across the wall
Name one place where continuous capillaries are found.
Gas exchange near alveoli
Write a note on fenestrated capillaries.
4
Have pores than span the endothelial lining
Permit rapid diffusion of H2O, small peptides and such solutes
Present in the brain (choroid plexus - CSF), hypothalamus, pituitary gland and thyroid gland
Present in GIT absorptive surface and renal filtration sites
Where are fenestrated capillaries found?
6
GIT absorptive surfaces
Renal filtration sites
Brain
Hypothalamus
Pituitary gland
Thyroid gland
What is the main function of fenestrated capillaries?
They permit rapid diffusion of H2O
Write a note on sinusoidal capillaries.
4
Large gaps in the endothelial cells
May have macrophages associated with them
Found in the liver
Have an absence of a basement membrane
What are the three types of blood vessels?
Arteries
Capillaries
Veins
What runs parallel to veins?
Lymph vessels
How many different types of arteries are there?
Three
What are the three different types of arteries?
Elastic arteries
Muscular arteries
Arterioles
Write a note on elastic arteries.
3
Stretchy
Mostly wall is elastic and collagen (little muscle)
Also called windkessel vessels
Give two examples of elastic arteries.
Aorta
Corotic artery in neck
What are elastic arteries also called?
Windkessel vessels
Describe the windkessel effect on the aorta.
5
It ensures smooth blood flow
The aorta is stretchy
The aorta fills as the heart pumps blood out
When the heart starts filling again the aorta recoils which pushes blood towards the arteriole
Blood leaves heart at a constant flow
Define the windkessel effect.
A rhythmic fluid ejection from the heart is transformed into a fairly uniform flow in the arteries with reduced pressure oscillations (reduced pulse strength)
What fibre type in the wall of the aorta allows the windkessel effect to happen?
Elastin fibres
What happens to our elastic arteries as we get older?
2
As we get older we loose electricity
As this happens we lose compliance which is important in the heart and lung tissue
What happens if our arteries loose their compliance?
It results in higher blood pressure
Write a note on muscular arteries.
4
Three tunica
They are not completely open
Often called resistance vessels
They can change their radius
What are muscular arteries also called?
Resistance vessels
What does a change in the radius of a muscular artery determine?
Flow to any one area (often organs)
Hydrostatic pressure in capillaries
What are the three tunica of a muscular artery?
Internal elastic lamina
Tunica media
Tunica externa
What is the tunica media of muscular arteries?
A big thick muscular layer
What is a tunica externa in a muscular artery?
A connective tissue layer
What happens when you change the radius of a muscular artery?
(2)
It determines blood pressure into capillaries
It determines how much blood goes into any organ
What is atherosclerosis?
Plaques of fat in vessels wall between intima and media lamina
What is a stent?
2
wire mesh put in an artery to keep it open
A balloon catheter widens the artery and opens the mesh
Write a note on arterioles.
6
Resistance vessels
Determine size of capillary exchange area
Local factors control the number of capillaries receiving blood
Thick muscular layer
Branch off from muscular arteries
Control where we send blood
What do arterioles control?
Where we send blood
What are veins also called?
Capacitance vessels
What percentage of blood is in the veins?
64%
What do all veins do?
They return blood to the heart
They help us deal with a sudden loss of blood by acting as a reservoir
What two organs are good stores of blood?
Liver and spleen
How much of your blood can you loose before it becomes a medical emergency?
We can loose about 1/5th of our blood
In relation to the heart what are veins called?
They are called the adjustable forechamber of the heart
Why are veins called the adjustable forechamber of the heart?
They can decrease or increase flow back to the heart
What percentage of blood volume is venous reserve?
About 20% of blood volume
What veins have valves?
Veins in the limbs and the neck
Why do veins have valves?
2
To return the blood to the heart against gravity
To compartmentalise blood (distribute its weight)
What are varicose veins?
The valves in limbs don’t work correctly
How do veins differ from arteries?
Larger in diameter than arteries
Have thinner walls than arteries
Have lower blood pressure
How many tunica do veins have?
Three tunica
What three tunica do veins have?
Internal
Tunica Media
Tunica Externa
What is the internal elastic media of veins made of?
Epithelia and connective tissue
What is the tunica media of veins made of?
Smooth muscle and elastic
What is the tunica externa of veins made of?
Connective tissue
What are the three types of veins?
Venules
Medium-sized veins
Large veins
What are venules?
2
Very small veins
Collect blood from capillaries
What are medium-sized veins?
2
Thin tunica media and few smooth muscle
Tunica externa with longitudinal bundles of elastic fibres
What are large veins?
3
Veins with three tunica layers
Thick tunica externa
Thin tunica media
What are venous valves ?
Folds of the tunica intima
What do venous valves do?
They prevent blood from flowing backwards
Compression - push blood towards the heart
Where are large veins found?
In between skeletal muscle
What happens when we exercise our skeletal muscle?
Our skeletal muscle works harder which forces blood up the veins harder
Where do lymphatic vessels begin?
In the peripheral tissue
Where do lymphatic vessels end?
They end by emptying into great veins
What do lymphatic vessels do with their contents?
They return their fluid and solutes to general circulation
What is the function of lymph vessels?
They transport fats from GIT to liver
How do lymph vessels differ from veins?
Lymph vessels have more valves than veins
What are shunt vessels?
Vessels joining arteries and veins, bypassing capillaries
What is the function of shunt vessels?
They are important in thermoregulation
