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Cell Bio Exam 3 > 25 - Vascular biology I > Flashcards

25 - Vascular biology I Flashcards

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1
Q

Overview of blood vascular system

A

Peripheral tissues

  • Arteries deliver blood to peripheral tissues
  • Microcirculation is where nutrient exchange occurs
  • The vena cava returns peripheral circulation to the heart

Pulmonary circulation

  • Consists of microcirculation in the lungs
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2
Q

Lymphatic vascular system - What is the most important protein in the blood? Is there a net loss or net gain of fluid from the tissues during circulation?

A

Works in concert with the blood vascular system

  • Albumin is an important plasma protein because it exerts colloid osmotic pressure
  • As blood moves through microcirculation, various pressures cause blood to move in and out
    • There will ALWAYS be a net LOSS of fluid into the tissues
    • To prevent excess blood accumulation in the tissues, the lymphatic system picks up the extra fluid and returns lymph to venous circulation
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3
Q

What is the general structure of a blood vessel?

A

3 layers:

  1. Intima: creates the lumen of the blood vessel - innermost layer
  2. Media: middle layer
  3. Adventitia: outermost layer, AKA externa
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4
Q

How many layers are in the tunica intima? What are they?

A

4 layers

  1. Endothelium of tunica intima (innermost)
  2. Basal lamina
  3. Subendothelial connective tissue
  4. Internal elastic membrane (outer most layer)
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5
Q

Endothelium of tunica intima

A

Endothelium of tunica intima = Innermost layer of tunica intima

  • Has DIRECT contact with blood
  • Contains an epithelial layer of simple squamous cells
  • These are called endothelial cells when they are associated with the vascular system
  • The endothelium is connected to the basal lamina
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6
Q

Basal lamina of the tunica intima

A

Connected to the innermost layer, the endothelium of the tunica intima, and is therefore the second innermost layer

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7
Q

Subendothelial connective tissue of the tunica intima

A

Subendothelial connective tissue of the tunica intima

  • External to the basal lamina
  • Contains the extracellular matrix plus the cells that synthesize that matrix
  • Occasionally smooth muscle cells are found here, but this is generally a precursor to atherosclerosis
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8
Q

Internal elastic membrane of the tunica intima

A

Internal elastic membrane of the tunica intima

  • Outer most layer of the tunica intima
  • This layer is fenestrated, meaning that there are tiny openings within this layer
  • The purpose of this is to move gas and nutrients
  • Blood will mvoe externally out
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9
Q

What is the tunica media comprised of?

A

Tunica media

  • The bulk of the tunica media is smooth muscle cells
  • There are also variable amounts of elastin - this depends on the type of vessel
  • The outermost component of the tunica media is an external elastic lamina (this will appear as a bluish line at the microscopic level)
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10
Q

What is the tunica adventitia (externa) comprised of?

A

Tunica adventitia (externa)

  • Blood vessels and nerve fibers are transmitted in this layer
    • The vasculature sends branches through fenestrations of external elastic membrane to the outer layer of tunica media
    • The walls of the vessels are supplied by blood in the lumen
    • Externally, they are supplied by vasa vasorum (“vessels of the vessels”)
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11
Q

When are vasa vasorum required?

A

Required for vessels greater than 1 mm

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12
Q

How can you differentiate between arteries and viens by looking at only the vasa vasorum?

A

There is a difference between the depth of penetration of vasa vasorum toward the tunica intima

  • Vasa vasorum in veins will penetrate much deeper, and closer to the tunica intima than in arteries
    • This is because the veins are carrying deoxygenated blood
  • Oxygenated blood carried by the arteries is able to “feed” the tunica intima in arteries
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13
Q

What is the relationship between vasa vasorum and inflammation? What are some examples of this?

A

Inflammation

  • The vasa vasorum contributes to inflammation
  • Examples
    • Angiogenesis is seen in atherosclerosis
    • Syphylis also shows changes in teh vasa vasorum
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14
Q

What are the effects of syphilis on the vasa vasorum of the ascending aorta?

A

Endarteritis and periarteritis

  • Degeneration of elastic tissue and smooth muscle
  • Inflammatory cells are observed around the vasa vasorum
    • Dark specs will show up - these are inflammatory cells
  • Syphilis will lead to inflammation of the ascending aorta and eventually, the wall of the aorta will begin to degenerate
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15
Q

What is nervi vasorum (vascularis)?

A

Nerves that supply the walls of blood vessels

  • Nervi vasorum translates to the “nerves of the vessels”
    • These are found in the tunica aventitia (external)
    • Can also be called “nervi vascularis”
  • Most of these nerves are soley sympathetic
    • Some also have parasympathetics
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16
Q

What is meant by the “light halo” of the nervi vasorum?

A

The light halo = sympathetic nerve endings external to the tunica media, forms a “halo” around the tunica adventitia

  • These nerve endings do NOT penetrate the tunica media
  • They innervate the OUTER part of smooth muscle
  • Once acitvated by sympathetic activation, they can communicate through gap junctions to smooth muscle cells
  • They release norepinephrine
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17
Q

Describe endothelial cells

A

Endothelial cells are flattened cells

  • Oriented in the direction of blood flow
  • Elongated in the direction of blood flow

Junctional complexes connect two endothelial cells

  • Lumen is above, where the blood flow is
  • Microvili will, on occasion, be found in the apical domain of endothelial cells
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18
Q

How are nutrients absorbed from the circulation into the tissues?

A

Numerous pinocytotic vesicles

  • Important transport process of enothelial cells of the vascular system
  • Transport from the lumen of the blood vessel across the cytoplasm and into the subendothelial tissue compartment of the tunica intima
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19
Q

What is a myoendothelial junction? What is the result?

A

Myoendothelial junction

  • The myendothelial junction is the junction between the endothelium and the smooth muscles
  • The shear stress that is exerted by the blood flow produces endothelial cell hyperpolarization
    • Increased flow through the vascular system increases the level of stress on the endothelial cells
  • Hyperpolarization communicates through gap junctions to the smooth muscles, causing hyperpolarization of smooth muscles as well
  • This results in vasodilation - an increase in the diameter of the vessel
20
Q

What are Weibel-Palade (WP) granules?

A

Weibel-Palade (WP) granules

  • The storage granules of endothelial cells, the cells that form the inner lining of the blood vessels and heart
  • They store and release two principal molecules, von Willebrand factor and P-selectin, and thus play a dual role in hemostasis and inflammation
21
Q

What is von Willebran factor important for?

A

Coagulation!

  • A deficiency in von Willebrand factor will result in a hemorrhagic disease
22
Q

What is P-selectin important for?

A

P-selectin

  • Important for allowing leukocytes to connect to endothelial cell membranes and facilitate migration through the wall of vasculature
23
Q

What are the 6 main functions of endothelial cells?

A
  1. Produce prostacyclin
    • Prostacyclin is a vasodilator, so it increases blood flow
    • Also inhibits blood clotting
  2. Act as a chemical mediator
    • Functions in both vasodilation and vasoconstriction
    • Nitrate oxide is a potent vasodilator
  3. Produce endothelin I
    • Potent vasoconstrictor of the walls of the vessels
  4. Control vascular growth
    • Angiogenesis
  5. Inhibit or promote blood clot formation
    • Important to prevent excessive blood loss
  6. Regulate movement of inflammatory cells from the lumen into the tissues
    • Selectin is an important adhesion molecule to allow inflammatory cells to recognize the membrane
24
Q

What are the segmental characteristics of blood vessels?

A

When looking at different vessesls, there are segmental differences in hwo the tunics are arranged

  • High pressure vessels
    • Arterial circulation
    • Walls are thick and the tunica media is prominent
  • Low pressure
    • Thinner walls
25
Q

Why do we see segmental characteristics?

A

Segmental characteristics are due to form-fuction relationships

***VERY IMPORTANT***

26
Q

What are the segmental characteristcs of high pressure environments?

A

High pressure environments

  • A lot of smooth muscle and elastic elements
  • The wall of the aorta is elastic, so it can stretch with ejection of blood and will recoil with diastoel to maintain driving pressure
  • You will see diminishing amounts of smooth muscle and elastic materials in smaller arteries
  • Less elastic elements in arterioles
27
Q

What are the segmental characteristcs of the microcirculation?

A

Microcirculation is where there are capillaries and pericytic venules

  • Endothelium and basal lamina ONLY
  • No extra tunics are present because they would interrupt the exchange of gas and nutrients
  • This is a very thin component
  • Metabolic factors determine the framework/structure of the wall
28
Q

What are the segmental characteristcs of venous components?

A

Venous components

  • A lot of connective tissue
  • Not a lot of change in the amount of smooth muscle from large vessels to small vessels
  • Pick up elastic components again
29
Q

Architecture of an artery vs. vein

A

Signature features of Arteries:

  • Prominent elastic membrane
  • Internal or external elastic membrane indicates arterial side
  • Thick muscular tunica media

Signature features of Veins:

  • Do NOT hae a prominent internal or external lamina
  • Thin tunica media compared to arteries
  • Tunica adventitia has a lot of connective tissue and is therefore the thickest layer of the vein
    • The wall of the vein does not have as much connective tissue
30
Q

What are some examples of elastic arteries?

A

Aorta, brachiocephalic trunk

31
Q

Describe the tunica media of an elastic artery

A

Tunica media of an elastic artery

  • Alternating smooth muscle and elastic lamellae that are fenestrated
  • Soley elastin in elastic lamellae (no elastin)
32
Q

Describe the tunica adventitia of an elastic artery

A

Tunica adventitia of an elastic artery

  • Mylinated nerve fiber
  • Connective tissue cells
  • Fibroblasts
33
Q

Describe Marfan syndrome

A

Marfan syndrome

  • A genetic disorder of human connective tissue
  • It has various expressions ranging from mild to severe effects… The most serious complications are defects of the heart valves and aorta, which often lead to early death
  • In the tunica media, elastic lamellae are connected and supported by true elastic fibers
    • This is what’s dysfunctional in Marfan’s
    • There is a “state of disarray” because the elastic fibers have microfibrils
    • There is a loss of structural integrity of the aorta due to the loss of interconnections in teh elastic fibers
34
Q

How does the aorta change over a lifetime?

A

From birth to adulthood

  • M lamellae increase with age, as needed
  • Adipose tissue is seen in newborns
  • Tunica media is much thicker in adults
35
Q

Effects of aging on the aorta

A

Age changes features of the aorta

  • The subendothelial compartment is more robust/thicker than normal
  • Moderal intimal fibrosis occurs, which is a normal effect of aging
  • The tunica media undergoes minor fragmentation of the elastic lamellae, which is also a normal change with age
36
Q

Age-related changes in muscular arteries

A

Young muscular artery

  • Internal elastic membrane appears scalloped
  • A huge vasa vasorum is visible

Elderly, less-muscular artery

  • Some fragmentation and intimal hyperplasia
  • Duplication of the internal elastic membrane
37
Q

What is meant by the ratio of unity in arterioles?

A

Arterioles

  • The wall-to-lumen ratio is 1, meaning that the opening of the lumen is the same size as the wall of the arteriole
  • The wall will contain one or two smooth muscle layers
  • Arterioles are the main resistance vessels
38
Q

What is microcirculation?

A

Microcirculation is the circulation between arterioles and venules

  • Arteriole: a small diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries
  • Venule: a very small blood vessel in the microcirculation that allows blood to return from the capillary beds to drain into the larger blood vessels, the veins
39
Q

What mechanism is utilized by the microcirculation to control volumes of blood flow?

A

Sphincter mechanism

  • The sphinters are located on metarterioles (branches of arterioles)
  • They control the volume of blood flow from arterioles to the microcirculation
  • Relaxes sphinters allow for more blood flow into the microcirculation
  • Sphinters are controlled by tissue metabolism
    • Active tissues will have relaxes sphincters
    • Relaxed sphincters allow for more blood flow into the microcirculation
  • Contracted sphinters limit the amount of blood flow through the microcirculation
    • This occurs in less active tissues
40
Q

What type of tissues will have relaxed sphincters of the microcirculation? What type of tissues will have contracted sphincters?

A

Active tissues

  • Relaxed sphincters
  • More blood flow
  • More delivery of oxygen and nutrients

Less active tissues

  • Contracted sphincters
  • Less blood flow
  • Lower need for oxygen and nutrient delivery
41
Q

What are the 3 classes of capillaries?

A
  1. Continuous
  2. Fenestrated (two subclasses)
    • With diaphragms in fenestration openings
    • Without diaphragms in fenestration openings
  3. Sinusoid
42
Q

What is a pericyte?

A

Pericyte

  • Undifferentiated mesenchymal cells that are contractile in nature that can differentiate into smooth muscle cells or fibroblasts under the appropriate stimuli
  • Help control the diameter of the microcirculation
  • Associated with capillaries and pericytic venules
43
Q

Describe a the cause of a cerebral aneurysm

A

Cerebral aneurysm

  • Bifurcation and branching points in circle of Willis are points of weakness and have the potential for aneurysms
  • Aneurysms in the cerebral cortex are found at the anterior communicating artery 30% of time
  • Aneurysms of the circle of Willis differ in etiology of that in, for example, the abdominal aorta
44
Q

Why are branching points prone to aneurysms?

A

Lack of smooth muslce

  • At points of bifurcation, there is a gap in smooth muscle because the smooth muscle that developed along the main artery didn’t fill in the gap
  • Lack of smooth muscle degreases the structural integrity at the point of bifurcation
  • A breakdown of the wall of the artery at the point of bifurcation will lead to an aneurysm
45
Q

How can you tell if someone is living with an aneurysm?

A

You can’t!

  • Aneurysms are silent
  • People can live with them until they rupture, at which point it may be too late to save their life

Cell Bio Exam 3 (8 decks)

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