Lecture 9: Heart and Vascular II Histo

Question 1

The walls of arteries and veins are made up three layers called what?

Answer 1

tunics.

Question 2

Arteries branch extrensively, causing them to decrease in diameter.

What about veins?

Answer 2

Veins merge, causing them to increase in diameter.

Question 3

What are the names of the three layers of tunica on veins and arteries?

Answer 3

1. Tunica intima

2. Tunica media

3. Tunica adventitia

Question 4

Tunica intima is closest to the lumen where the blood flows.

What three things makes up this layer?

Answer 4

1. Endothelium, made up SINGLE layer of squamous epithelial cells
2. Basal lamina, with endothelial cells
3. Subendothelial layer, made up of loose CT and an internal elastic membrane

Question 5

The tunica media consists layers of smooth muscle.

It extend from the internal elastic membrane/lamina of the tunica intima –> _________.

it is thicker in arteries or veins?

Answer 5

It entends from the internal elastic membrane to the external elastic membrane, a layer of elastin that seperates the tunica media and adventitia

-Thick in arteries, than veins.

Question 6

The tunica adventitia/externa is collagenous tissue with a few elastic fibers that merges with the loose CT that surrounds the vessels.

Is it thicker in arteries or veins?

Answer 6

thicker in veins,

thinner in arteries

Question 7

What is vasa vasorum?

Answer 7

Vessels of tunica adventitia in large arteries and veins.

They supply the vascular wall with blood.

Question 8

What is nervi vasorum?

Answer 8

ANS input that controls the contraction of vascular smooth muscle.

Question 9

Large (elastic) arteries are the largest vessels in the arterial system.

What is located in between the muscles of large arteries?

Answer 9

Sheets of elastin.

Question 10

Large arteries do not have fibroblasts. Thus, the smooth muscle makes what?

Answer 10

Collagen, elastin, ground substance of ECM.

CEG (Collagen, elastin, ground substance from the ECM

Question 11

When are the large arterial walls expanded?

Answer 11

systole.

Question 12

What happens to the walls of large arteries during diastole?

Answer 12

Lumens size reduces the pressure and allows strong blood flow.

Question 13

Medium or muscular arteries are off the large arteris and have much [more smooth muscle] and [less elastin] than larger arteries.

What is the hallmark of this?

Answer 13

They have a prominent internal elastic membrane and the external elastic membrane can be recoginzed.

Question 14

In medium (muscular arteries), how is the smooth muscle arranged?

Answer 14

Spiral fashion

Question 15

How thick is the tunica adventita and tunica media in medium sized arteries?

Answer 15

Both are relativelty the same thickness, but still smaller in size compared to large arteries.

Question 16

Small arteries and arterioles can be distinguished by the number of smooth muscle layers in the tunica media.

How many do small arteries have and how many do arterioles have?

Answer 16

Small arteries have up to 8 layers + an internal elastic membrane

Arterioles have 1-2 layers, and the internal elastic membrane may or may not be present.

Question 17

What are arterioles and what does sympathetic/parasympathetic innvervation to the tunica _____ cause?

Answer 17

Arteries regulate blood flow to capillary beds.

Sympathetic innervation to the tunica media–> vasoconstriction

Parasympathetic innervation to the tunica media–> vasodilation

Question 18

What are the jobs of capillaries?

Answer 18

Capillaries are the smallest blood vessels and they form capillary beds.

They are the sites of nutrient exchange and have a smaller diameter than RBC.

Question 19

Capillaries are the smallest blood vessels that form capillary beds. whose diameter is smaller than a RBC. They are surrounded by pericytes which do what?

Answer 19

Pericytes are contractile cells enclosed with basil lamina that promote the stability of the capillary and help it constrict (sensitive to NO).

Question 20

Capillaries only have a tunica _____

Answer 20

tunica media

Question 21

Endothelial cells are a single layer of cells that form the innermost aspect of tunica intima, lining capillary beds. Connected via cell-cell junctions. What do they do metabolically?

Answer 21

Endothelial cells are connected by tight junctions, altering their permeability.

They support the basement membrane, produce collagen, involved with blood coagulation, thrombosis, vasodilation and constriction

Question 22

What are the three types of capillaries?

Answer 22

1. Continuous capillaries
2. Fenestrated capillaries
3. Discontinuous capillaries

Question 23

Continuous capillaries are the most common capillaries. Describe them

Answer 23

Have tight junctions and a continuous basement membrane that prevents things from entering the capillary.

Question 24

Fenestrated capillaries are located in places where nutrient exchange with blood is important. Describe them.

Answer 24

Fenestrated capillaries have tight junctions and endothelial cells with fenestrations.

It has a continuous basement membrane.

Question 25

Discontinuous capillaries have endothelial cells with large **fenestrations** and a **discontinous basement membrane**, this allows a greater exchange of material.

Question 26

Where are continuous capillaries found?

Answer 26

Continuous capillaries are found throughout the body.

Question 27

Where are fenestrated capillaries located?

Answer 27

Endocrine glands, gallbladder and kidney

Question 28

Where are **discontinuous/sinusiodal capillaries** located?

Answer 28

**Bone marrow** **Liver** **Spleen**

Question 29

\_\_\_\_\_\_ are the first branch off of arteriole. **True capillaries** branch of of these and lack smooth muscle and may or may not have pericytes.

Answer 29

**Metarterioles.**

Question 30

Arterioles branch into metarterioles, which branch into true capillaries. Blood flow into these true capillaries is regulated by what?

Answer 30

**Precapillary sphincters**

Question 31

Name: The distal end of the metarteriole that lacks smooth muscle.

Answer 31

**Thoroughfare channel.** It connects to a **postcapillary venule**

Question 32

When a precapillary sphincter is relaxed, the capillary bed **_is/is not well_** perfused. What happens when a precapillary sphincter contracts?

Answer 32

**Is well perfused** **When a precapillary sphincter contracts, it shunts blood flow into the veins, preventing exchange within true capillaries.** **This changes based on our metabolic needs.**

Question 33

What is the smallest of the venules? What is the flow of blood through the veins back to the heart?

Answer 33

**Post-capillary venules** are the smallest of the venules. Post-capillary venules are going to join to form **muscular venules,** --\> combine to form **small veins**--\> **medium veins** (represent much of the named veins)--\> **large veins,** like the *SVC, IVC, and hepatic vein.*

Question 34

In the veins, **tunics are not distinct or well defined**, however, __________ have all three layers.

Answer 34

Large and medium veins.

Question 35

What should we remember about the **tunica intima** in **veins**?

Answer 35

The tunica intima has **semilunar valves**, made up of a thin CT covered by endothelial cells.

Question 36

How do the walls and lumen of the veins compare to that of the arteries.

Answer 36

Veins--\> thinner walls, however the lumen is larger than the artery and often collapsed.

Question 37

Postcapillary venules **have no tunica media**, which drain to muscular venules which have 1-2 layers of what ?

Answer 37

**1-2 layers of smooth muscle** in the tunica media & **a thin adventitia.**

Question 38

bSmall venules have all 3 tunicas, with a thicker ______ and a 2-3 layer\_\_\_\_\_\_?

Answer 38

Thicker adventitia & 2-3 layer tunica media

Question 39

Medium veins travel with **medium (muscular) arteries.** They have a thicker \_\_\_\_\_\_- and _______ and contain valves?

Answer 39

Medium veins have a **thicker tunica media** and **tunica adventitia.**

Question 40

In large veins, the _________ is the thickest layer of the vessel wall, which contains collagen, elastics fibers and fibroblasts. Also contains longitudinal \_\_\_\_\_\_\_\_?

Answer 40

**tunica adventitia** is thickest layer contains longitudinal **smooth muscle cells**

Question 41

In large veins, the ________ and _________ are thin. Intima blends in with media, media has smooth muscle and collagen.

Answer 41

**tunica media - thin with circumferentially arranged smoooth muscle cells, collagen fibers and some fibroplasts** **tunica intima- thin and blends in with tunica media**

Question 42

Lymphatic vessels are lined with \_\_\_\_\_\_\_. What is their role?

Answer 42

Lymphatic vessels are lined by **endothelium**. Plasma leaks out of capillaries and gets picked up by the lymphatic vessels. They convey the fluid unidirectionally and it it to the venous supply.

Question 43

**Lymphatic capillaries** are **closed ended tubes** found in capillary beds. **One-way valves** are formed by overlapping endothelial cells. What holds together the openings between endothelial cells?

Answer 43

**Anchoring filaments.**

Question 44

What helps to increase permeability of a lymphatic capillary?

Answer 44

An **incomplete basal lamina**

Question 45

Lympathic capillaries drain to **lymphatic vessels** which have all tunicas and posses valves. Walls increase in thickness as vessel increases in size. _______ prevent leakage.

Answer 45

Tight junctions there are afferent and efferent lympathic vessels

Question 46

What is the flow of lymph from lymphatic capillaries to bachiocephalic vein to drain into?

Answer 46

Lymphatic capillaries--\> Lymphatic vessels --\> Lymphatic trunks --\> Right lymphatic duct (for right side head neck limb thorax) --\> Thoracic Duct (entire body + left side) --\> **brachiocephalic vein**