3.1 Structure and Function of Blood Vessels Flashcards
How much blood do we have (in litres, and as a percentage of our bodyweight)
~5 litres (7-8% bodyweight)
Is there more blood in veins or arteries and arterioles?
Veins
What is meant by systemic circulation?
Everything except lungs
What percentage of blood is in the heart and lungs?
About 16%
Do veins or arteries have more smooth muscle? Why does this make sense?
- Arteries have more smooth muscle
- They carry blood which is at much higher pressures
What is the tunica intima? What is the name of the connective tissue within the tunica intima?
- Endothelium on inside of blood vessels
- Connective tissue is called lamina propria
(Tunica = latin for coat)
What is the tunica media? What does it contain?
- Smooth muscle
- Elastic fibres (give elasticity to the blood vessel)
- Connective tissue (supplies oxygen and nutrients to muscle cells)
What is the tunica adventitia? What does it contain?
- Connective tissue
- Nerve fibres (control diameter)
Where are substances exchanged throughout the cardio system?
Capillaries
What is transmural pressure?
Pressure gradient across a vessel wall - stiffer wall means lower elasticity and higher transmural pressure.
What is hydrostatic pressure?
The pressure exerted due to the density and gravity of the fluid.
Why are arteries like highways?
- You can transport quick, but you cannot stop and exchange goods.
Diameter of arteries
from mm to 100s of micrometer
What are the two types of large arteries? Give some examples of each.
- Elastic (aorta, pulmonary arteries)
- Muscular (femoral artery, radial & brachial arteries)
How do the composition of the tunica media differ between muscular and elastic arteries?
Elastic: more elastic fibres in tunica media
Muscular: more smooth muscle in tunica media
Explain systole vs diastole
Systolic pressure is exerted on blood vessels when the heart pushes blood around the body.
Diastolic pressure is less than systolic pressure, and occurs when the ventricles relax and refill with blood
Explain the Windkessel effect
During systole, the (elastic) aorta expands and stores some blood which is released during diastole, thus maintaining constant flow.
Diameter of arteriole
5-30 micrometer
How many layers of smooth muscle in arteriole?
1-4
How do arterioles regulate blood pressure
Changes in diameter (can have a huge effect)
Why does blood flow slowest at the capillaries?
Most time for exchange of goods
Is the pressure of pulmonary circulation smaller or greater than that of systemic circulation? How does this effect the size of the aorta vs pulmonary artery?
Pulmonary circulation is much lower in pressure. Therefore, the pulmonary artery does not need as much smooth muscle as the aorta.
Relationship between blood flow and pressure difference (delta P)
Proportional
Relationship between radius and blood flow
Proportional to the fourth power of the radius
Relationshio between blood flow and vessel length (L)
Inversely proportional
Relationship between blood flow and viscosity
Inversely proportional
What blood vessels are involved in microcirculation?
Arterioles, capillaries, venules
How do veins overcome the hydrostatic pressure to get blood back to the heart?
They are next to muscles, and the muscles get the blood flowing when they contract. This is why you shouldn’t sit all day
Why do veins need valves?
So that blood cannot flow back.
What does it mean that lymphatic vessels start “blind”
They start somewhere, they are not continuous
What goes into lymphatic vessels (in terms of the cardiovascular system)?
Everything that is filtered from the capillaries, but not reabsorbed in the venules
Do lymphatic vessels have valves?
Yes
Where does afferent lymph drain?
Into “home lymph node” (like a local pub), where they are filtered.
Where does lymph go once it leaves the lymph nodes?
Drains via an efferent lymphatic vessel into the right lymphatic duct (right superior area) or the thoracic duct (everywhere else)
