Histo 2

Question 1

What are “tunics”?

Answer 1

3 layers of the walls of arteries and veins

Question 2

What’s to know about veins and arteries?

Answer 2

Arteries branch extensively to decrease in diameter

Veins merge repeatedly to increase in diameter

Question 3

What is the Tunica Intima?

What are the 3 layers?

what is only really in large arteries?

Answer 3

most closely associated to the lumen of the vessel.

1. It’s lined with a single layer of simple squamous endothelium
2. deep to that you have basal lamina of the endothelial cells. Located here is a thin EC layer (collagen, proteoglycans, glycoproteins)
3. Subendothelial layer –> has loose Areolar CT. link the endothelial Layer to the next layer as we move to the outside of the external vessel.

Internal elastic membrane –> sheet like layer of fenestrated elastic material w/in arteries and arterioles (this allows for rubber band functions as blood moves through)

Question 4

What is the Tunica Media?

Answer 4

In the middle

It’s going to be much thicker in arteries than in veins

this is where you have smooth muscle layers that are arranged in a circular pattern that allows the vessels to constrict down or dilate

Question 5

Within the tunica media what two membranes do you have?

Answer 5

Internal and External Elastic Membranes

The external elastic membrane has a layer of elastin that separates the tunica media from the adventitia

Question 6

What is the Tunica Adventitia?

What is this thinner in? veins or arteries

what is it composed of and why is it important?

Answer 6

Outermost layer of the vessel.

This is a thinner layer in arteries than in veins

in veins this is where they get their structural support.

This is loose CT that allows it to adhere to other structures in close proximity –> vessels like to travel with nerves (neuromuscular bundle). that gluing of those structures together is because of the tunica adventitia likes to glue it to it.

Question 7

what gives veins and arteries their structural support?

Answer 7

Veins = tunica adventitia

Arteria = Tunica media

Question 8

Especially in veins, because the blood is deoxygenated, the nutrients available from the blood to diffuse out to the walls is what?

Answer 8

lacking compared to the arteries

blood from the aorta to systemic it has tons of oxygen and the nutrients can diffuse across the arterial walls.

in veins it’s opposite so you’re not going to have much going across the vessel wall and it needs nutrients though.

Question 9

Vasa Vasorum?

Answer 9

Vasa Vasorum

additional blood vessels located in the tunica adventitia especially in large veins.

you’ll see it in larger arteries.

some of the nutrients diffuse into the lumen and we need nutrients to go to the vascular walls themselves.

this literally means “vessels of vessels”

it’s how larger vessels receive their nutrients.

Question 10

What is nervi Vasorum

Answer 10

ANS input that controls contraction of vascular contraction

Question 11

Why are large arteries also called elastic arteries?

where are these elastic fibers located.. what are they arranged in?

what do they not have? How do we make all the fibers then?

Answer 11

because of the large amount of elastin

in the super thick tunica media. arranged in lamellae

NO fibroblasts! smooth muscle makes all ECM components

Question 12

What is the purpose of fenestrations in the tunica media of the large arteries?

Answer 12

allows nutrients to pass through

Question 13

What happens with regards to lamellae as you age?

Answer 13

the amount of lamellae increases, so this makes blood pressure feedback a bit tougher.

Question 14

What do think of when you see muscular arteries?

Answer 14

things that aren’t the great vessels but also have names… i.e. brachial, axillary, femoral

Question 15

What are the muscular arteries composed of?

what is a hallmark of this?

what’s to note about the tunica adventitia?

Answer 15

more smooth muscle but less elastin. we don’t have as much blood pressure here!

Prominent Internal Elastic Membrane

also have a recognizable External Elastic Membrane

it’s thicker than usual, about the same size as the tunica media

Question 16

How do you tell the difference between a large elastic artery and a medium muscular artery?

Answer 16

Elastic has the wavy lines in the tunica media, muscular does not

Question 17

Remember, the internal elastic membrane is part o what structure?

Answer 17

Tunica Intima

Question 18

How many layers of smooth muscle are in small arteries? arterioles?

what’s in small arteries but may not be in arterioles?

Answer 18

8

1-2

internal elastic membrane

Question 19

What do small arteries drain into?

What is the key role of arterioles?

What does sympathetic innervation and parasympathetic innervation do to the tunica media of arterioles?

Answer 19

Arterioles

regulate flow into the capillary beds, vasoconstriction + vasodilation

Vasoconstriction

Vasodilation

Question 20

Capillaries do what?

what is the diameter associated with?

what are these beds surrounded by? what do they do?

Answer 20

Site of metabolic gas exchange and they form true capillary beds.

RBC

Pericytes –> contractile cells that surround the capillary vessels. they enclose the basal lamina. they can contract down on the capillary bed

Question 21

Why are pericytes important for capillary beds?

Answer 21

they don’t have a tunica media or adventitia, so the pericyte is in its place. you need the pericyte to contract down.

Question 22

What are pericytes sensitive to?

what are they helpful for?

Answer 22

Nitric Oxide

structural stability and constriction if needed.

Question 23

Endothelial Cells are found where?

Answer 23

cells that are found lining capillary beds.

in most typical capillaries they are connected by tight junctions.

Question 24

What are the 3 types of capillaries?

Answer 24

continuous
Fenestrated
Discontinuous

Question 25

What are continuous capillaries?

Answer 25

most common

widespread layer of endothelial cells lining the lumen of the capillary, surrounded by a uniform and complete basal lamina

this allows for things to not get into or out of the capillary bed unless they’re super small molecules.

Question 26

What are Fenestrated Capillaries?

Answer 26

“finistra” means window. these are open pores that allow for things of larger size to move through

The basal lamina surrounding it is also complete and continuous.

Question 27

What are Discontinuous Capillaries?

Answer 27

There is no regulation at all. the openings are large enough for cells to fit through and the basal lamina is incomplete / discontinuous.

proteins, cells, other things can move into these types.

Question 28

Where might you find discontinuous capillaries

Answer 28

Bone Marrow
Liver
Spleen

Question 29

When an artery shoves it’s blood into a capillary bed, what’s the first thing it goes through?

what is the process from here?

Answer 29

metaarteriole –> feeds into a true capillary bed which has a thoroughfare channel that has other branches that feed into this channel

leave through post capillary venules

Question 30

What allow constriction in the capillary beds?

Answer 30

Precapillary sphincters.

they can clamp down if you don’t want to do gas exchange

when it shunts the blood it just moves it to a different spot. moves quickly into the postcapillary venule.

Question 31

If we are in the GI and during Sympathetic stage, are the sphincters going to be open or closed in the capillary beds

Answer 31

closed

Question 32

What do venules do?

Answer 32

smallest veins.

they join back together to form muscular venules.

continue to combine to small veins, then medium veins, and then large veins.

Question 33

What are the features of the veins?

what about the tunics?

Answer 33

there are valves that are in the tunica intima.

the tunica are not as well distinct but the large and medium have all 3 layers

Question 34

If you see a vein and an artery in the same histo slide, how do you know it’s a vein?

Answer 34

veins have a collapsed lumen and the walls are thinner (except in large veins)

Question 35

What do medium veins travel with?

what do medium veins have that helps distinguish them from smaller arteries?

Answer 35

muscular arteries

thicker tunica media and adventitia.

it has valves!

the wall is often folded around large lumen

Question 36

What’s the difference between large veins and large arteries histologically?

Answer 36

in veins you have bundles that are there. the smooth muscle is in the adventitia rather than in the media because the media isn’t that thick.

the tunica media is what all of the elastin.

Question 37

What is the lymphatic system?

lymphatic capillaries?

Answer 37

blood leaks out of the capillary bed and it’s collected as lymph.

closed-ended tubes found among capillary beds.

they have overlapping endothelial capillaries that form 1-way valves for collecting lymph

Question 38

what do lymphatic capillaries become?

how do you know it’s a lymphatic capillary?

Answer 38

lymphatic vessels

it’s super thin in the wall, almost 1 layer thick. it looks super pale staining and a gritty looking substance.

there’s no blood in it.