Cardiovascular system: Blood vessels

Question 1

What are the different types of arteries?

Answer 1

Elastic arteries, muscular arteries and arteriole

Question 2

Where are elastic arteries found?

Answer 2

Just off the heart (where the pressure is highest FYI)

Question 3

What is a unique property of elastic arteries compared to other types of arteries?

Answer 3

They are elastic and expand when the pressure increases

Question 4

What makes the elastic arteries elastic?

Answer 4

They are made of sheets of elastin in the middle tunic (i.e. the middle layer)

Question 5

When do the elastic arteries stretch?

Answer 5

During the contraction of the left ventricle

Question 6

Why do the elastic arteries stretch when the heart beats?

Answer 6

The ventricle pumps blood faster than blood can flow therefore the arteries convert some energy into elastic energy

Question 7

What is the benefit of the elastic arteries absorbing some of the energy from the heart beat?

Answer 7

During relaxation the elastic artery release the elastic energy and pumps more blood therefore smoothing out the pulses of pressure so there is a more continuous flow of blood

Question 8

What is the function of muscular arteries?

Answer 8

distribution blood around the body at a high pressure and in the lungs at a medium pressure

Question 9

What is the structure of muscular arteries?

Answer 9

Collagen layer of outer tunic (for binding to surrounding tissue), layers of smooth muscle in the middle tunic and a layer of endothelial cells on the inner tunic

Question 10

How do the muscular arteries control blood pressure?

Answer 10

The smooth muscle can vasoconstrict or dilate to increase or decrease blood pressure

Question 11

How is flow rate proportional to radius?

Answer 11

By the fourth power (i.e. flow ~ r^4)

Question 12

When doing exercise, how will the muscular arteries respond?

Answer 12

They will vasodilate for the muscles to allow for increased blood flow and vasoconstrict for the digestive system as it isn’t necessary

Question 13

What is the function of the arteriole?

Answer 13

It controls blood flow into the capillary beds

Question 14

How doe she muscular wall of the arteriole compare relatively to the other arteries?

Answer 14

It is the thickest muscular wall of any artery

Question 15

Why is the muscular wall of the arteriole much thicker relatively?

Answer 15

They have to protect the capillaries by reducing the pressure to the arteries the most therefore experience the greatest resistance.

Question 16

Why do the arterioles have to protect the capillaries?

Answer 16

Because the capillaries are very thin walled (singled layer of endothelial cells) and are unable to control blood pressure

Question 17

What does the degrees of construct of the arterioles throughout the body determine?

Answer 17

total peripheral resistance which in turn affects the mean arterial blood pressure

Question 18

What is the structure of arteriole’s?

Answer 18

A layer of endothelial cells on the inside and layers of smooth muscle surround the lumen

Question 19

What is the function of capillaries?

Answer 19

Allow exchanges of gases, nutrients and wastes between blood and the surrounding tissue fluid

Question 20

What is the structure of capillaries?

Answer 20

A single cell thick layer of endothelial cells

Question 21

How do the capillaries affect the shape of the red blood cells? What does this result in?

Answer 21

Capillaries are so narrow that they cause the red blood cells to bend

This causes significant damage to the cells which requires them to be replaced frequently

Question 22

How do nutrients get in and out of the capillaries?

Answer 22

The capillaries are leaky so plasma can flow out of the capillaries containing nutrients (but goes back into capillaries due to osmotic gradient FYI) and the blood cells stay in the capillaries and diffuse their gases

Question 23

What is the process of nutrients from the capillaries to the cells?

Answer 23

Capillary –> interstice fluid –> cells

Question 24

What is the function of a venule?

Answer 24

Drains capillary beds and during infection and inflammation venules are where the white blood cells leave the blood to attack bacteria

Question 25

How are venules able to perform their functions?

Answer 25

• draining capillary beds: lower pressure than surrounding tissue therefore excess interstitial fluid re-absorbed
• white blood cell response: slow blood movement therefore they can move in and out of vessel as needed

Question 26

What are venules similar to? How are they different?

Answer 26

They are very similar to capillaries (thin walled of endothelium) except they have connective tissue (capillaries have none)

Question 27

What is the function of veins? What is the exception to this rule?

Answer 27

To drain blood back to the heart and as a reservoir of blood

Portal veins, drain blood between different capillary beds (i.e. intestine to liver)

Question 28

What is the structure of a vein?

Answer 28

Thin elastic walls with bicuspid valves (mailing in the legs) lining all along the wall of the vein

Question 29

What is the function of the bicuspid valves? Why are they needed

Answer 29

Prevent the back flow of deoxygenated blood down the vein, in particular in the legs

The blood pressure in the veins is very low and without the valves, un-oxygenated blood would drain back into capillary beds

Question 30

How do veins act as a reservoir of blood?

Answer 30

During rest they can expand and store more blood as the body doesn’t need as much oxygenated blood (FYI at rest 64% of blood in veins, 13% in arteries)

Question 31

How do the veins react when you start to exercise?

Answer 31

The veins constrict which put more blood into the arterial system

Question 32

How do the muscles help blood move up the veins? Where is this particular important and why?

Answer 32

As the muscle contract it squeezes the veins. Due to the bicuspid valves it prevents the blood from flowing backward so the blood can only go forward therefore acts as a venous pump

Importnat in the legs as the blood has to go a long way back up the body

Question 33

What is the function of the coronary arteries?

Answer 33

Supply the heart with oxygen

Question 34

Why does the heart need coronary arteries even though it has so much blood around it?

Answer 34

The heart muscle is thick, in particular the left ventricle, and diffusion along is not fast enough to supply all the heart with oxygen therefore vessels to supply the cells directly are needed. Also the right side of the heart is pumping deoxygenated blood and it needs a supply of oxygenated blood

Question 35

What is atheroma?

Answer 35

Degeneration of the arteries by scar tissue and fatty deposits

Question 36

If a coronary artery is narrowed to about 20% of its normal cross-section by atheroma, what does this cause? During exercise what can this cause?

Answer 36

Causes significant obstruction to blood flow

The myocardium (heart tissue) supplied by the artery runs low on oxygen causing iscehmia resulting in chest pain (angina). Severe iscehmia result in death of a local area of myocardium (infarction)

Question 37

What is a response by the body to atheroma?

Answer 37

Different arterial vessels join up and widen slowly so that ischaemic myocardium can be supplied by a different artery (that is further away FYI)