Week 6 CVM

Question 0

Name the three layers/tunics of a blood vessel from outermost to innermost

Answer 0

1. Tunica externa/adventitia
2. Tunica media
3. Tunica interna

Question 1

What are the three major types of blood vessels?

Answer 1

Arteries, veins and capillaries

Question 2

Which blood vessel type is involved with exchange with tissues?

Answer 2

Capillaries

Question 3

Which blood vessel type carries blood away from the heart?

Answer 3

Arteries and arterioles

Question 4

Which blood vessel type carries blood to the heart?

Answer 4

Veins and venules

Question 5

Which sized veins have valves in them?

Answer 5

Medium and small veins

Question 6

What is the significance is valves in veins?

Answer 6

Prevent backflow of venous blood that can occur due to gravity. Valves are found mostly in the limbs for this reason

Question 7

What is the name of the tiny blood vessel networks that service the layers of the larger vessels themselves?

Answer 7

Vasa Vasorum

Question 8

Describe the histological make up of the tunica externa

Answer 8

Connective tissue with loose weave of collagen and elastic fibres. Contains nerves and lymphatic vessels

Question 9

Describe the histological make up of the tunica media

Answer 9

Smooth muscle( innervated by sns) and lose connective tissue.

Question 10

Describe the histological make up of the tunica interna

Answer 10

Simple squamous endothelium, connective tissue with elastin. In contact with blood

Question 11

List the two types of arteries

Answer 11

Elastic and muscular arteries

Question 12

List the 4 major controllers of flow?

Answer 12

1.metabolic
2. Neurogenic
3. Myogenic
4 . Endothelial

Question 13

Describe the flow of blood through the body winning and ending with the right atrium ?

Answer 13

• Blood ‘begins’ in right atrium
• Pumped into pulmonary artery
• Into lung, O2 exchange occurs
• Returns to left atrium
• Pumped into aorta via left ventricle
• Blood to the periphery from through arteries
• Arterioles -> capillary beds
• Fluid forced out of capillaries to interstitium
• Fluid returns to capillary beds at venous end
• Capillaries drain into venules
• Venules drain into the veins
• Veins empty in the venae cavae
• Blood travels back to the right atrium

Question 14

Describe some characteristics of elastic arteries

Answer 14

Largest arteries with diameter of 1-2.5cm
Closest to the heart
Conduct blood from heart to medium sized arteries
Thick walls but wide lumen (important for laminar blood flow )
Lots of elastin to withstand pressure of ejection from the ventricle and to dampen pressure oscillation contain the most elastin than any other vessel type
Smooth muscle opposes stretch rather than actively constricting vessel diameter.
Elastic arteries expand and recoil as heart ejects blood consequently blood flows continuously rather than starting and stopping with pulsating rhythm of heart beat

Question 15

Describe some characteristics of muscular arteries

Answer 15

Do the major redistribution of blood flow to the organs
Distal to elastic arteries , distributing blood among the organ systems
Diameter of 0.3-1cm
Thickest tunica media of all arteries contains more smooth muscle than the elastic arteries (less elastin)
Vasoactive (capable of vasodilation and constriction to modulate blood pressure and flow)
Account for the majority of arteries in the body
They are more active in vasoconstriction but less distensible than elastic (not capable of stretching)

Question 16

Describe arterioles

Answer 16

Distal to both types of arteries (muscular and elastic)
Smallest of the arteries with diameters of 10 micrometers to 0.3 mm
The smallest arteriole (terminal or resistance arterioles have no tunica adventitia and may be 1 layer of smooth muscle surrounding one layer of endothelial cells
Vasoactive with strong influence on blood pressure and flow (protective mechanism)
Basically arterioles are smooth muscle machines packed full of smooth muscle and sometimes a few scattered elastic fibers
The make local decisions of where blood is going to flow and can shut down flow to a particular capillary bed
Constriction of arterioles causes the tissues served to be largely bypassd

Question 17

Which blood vessel type do rbcs travel in single file?

Answer 17

Capillaries

Question 18

List the 3 types of capillaries and how they differ

Answer 18

1. Continuous capillaries:
   Endothelium is uninterrupted tight junctions
   These junctions are usually incomplete and leave intercellular clefts which are large enough to allow limited passage of fluids and small solutes
   Service all tissues except epithelia and cartilage
   The can also be completely impermeable(Blood brain barrier) or be able to pass water, small solutes and lipid soluble materials
   Common in the skin and muscles
2. Fenestrated Capillaries:
   Endothelium has numerous pores/fenestrations between cells to allow for easier fluid movement and movement of small proteins allows easy uptake or filtration
   Found wherever active filtration and absorption occurs eg. Intestines , kidneys
3. Sinusoidal Capillaries:
   Very leaky capillaries which are usually fenestrated
   Allow larger molecules to pass than the fenestrated capillaries allow
   Found only in liver, bone marrow , spleen (lymphoid tissues) and some endocrine organs (adrenal medulla)
   They have less tight junctions and larger intercellular clefts
   May have large and irregular lumens

Question 19

What is micro circulation

Answer 19

Blood flow from arteriole through capillaries to the Venule

Question 20

What is the metarteriole

Answer 20

Vessel that links arterioles and true capillaries

Question 21

What is a thoroughfare channel

Answer 21

Vessel that links venules and true capillaries

Question 22

In terms of the capillary bed, what is the vascular shunt?

Answer 22

metarteriole & thoroughfare channel connect directly and drain the capillaries but also may allow blood to bypass the capillaries (due to changing need) and connect the arteriole and venule directly

Question 23

What are precapillary sphincters??

Answer 23

Blood flow from metarteriole to capillary is controlled by precapillary sphincters which are cuffs of smooth muscle which surround the roots of each capillary at the metarteriole. It acts as a valve to regulate blood flow into the capillary.

When the sphincters are relaxed, blood flows through the true capillaries and takes part in exchanges with tissue cells

When the sphincters are contracted, blood flows through the shunts and bypasses the tissue cells

Question 24

List the four assist devices for venous flow of blood

Answer 24

Muscle pump,mrwspiratory pump, cardiac suction and venoconstriction

Question 25

What is an anastomoses

Answer 25

where two blood vessels merge/join together a connection between two peripheral vessels without an intervening capillary bed arteries supplying the same capillary bed often join to create arterial anastomoses (collaterals) metarteriole thoroughfare passages link arterioles and venules veins form many anastomoses

Question 26

What are the four starlings forces?

Answer 26

1. Capillary Hydrostatic Pressure Pressure of fluid within the capillary forces water and dissolved substances out of capillary ~30mmHg at arteriole end and 10mmHg at venous end 2. Plasma Colloid Osmotic (aka Oncotic) Pressure Osmotic pressure caused by blood proteins draws fluid in ~28 mmHg 3. Interstitial Fluid Pressure Hydrostatic pressure in tissues may draw or oppose flow from capillary Varies with capillary bed; positive in glomerulus, negative in loose tissues, like the skin (set average as 0 mmHg) 4. Interstitial Fluid Colloid Osmotic (aka Oncotic) Pressure Proteins in tissues causes osmosis out of capillary ~8 mmHg

Question 27

How many litres of fluid from plasma is lost per day?

Answer 27

~3L but Lymphatics return it!

Question 28

Describe true aneurysms

Answer 28

True Aneurysms: •all 3 layers/tunics are affected in the blood vessel •Defined as a 50% increase in the normal diameter of the vessel. •The artery wall can balloon out symmetrically to form a 'fusiform' aneurysm or there can be a local 'blow-out' to form a 'saccular' aneurysm.

Question 29

Describe dissecting aneurysms

Answer 29

Dissecting Aneurysms: • A split or dissection within the tunica media • Allows blood to collect and compress the lumen

Question 30

What are end arteries?

Answer 30

End Arteries: • Tissues supplied by the end arteries lack additional sources of blood and are therefore more vulnerable If that end artery was to be blocked/damaged