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Medical Physiology > Cardio 2 histo (physio) > Flashcards

Cardio 2 histo (physio) Flashcards

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USMLE® Step 1 flashcards
1
Q

The walls of medium and large blood vessels are generally described in terms of 3 concentric layers or tunics. Starting from the innermost layer, these tunics are:

A
  1. Tunica Intima
  2. Tunica Media
  3. Tunica Adventitia
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2
Q

Tunica Intima is the thinnest layer. It is comprised of………….., which is a layer of simple squamous epithelium, and…………., which is a thin loose connective tissue layer with occasional smooth muscle cells.

A

Endothelium

Sub endothelial connective tissue

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3
Q

Each endothelial cell is arranged in……………. to the lumen of the vessel, and are attached to one another by tight junctions and occasional gap junctions. The endothelium rests on a……………..

A

parallel

basal lamina

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4
Q

Tunica Media is the middle layer. What is it comprised of?

A
  • circumferentially arranged smooth muscle cells
  • extra cellular matrix components
  • elastic fibers
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5
Q

Tunica Adventitia covers the outer surface of blood vessels and is primarily composed of what 3 things?

A
  • collagen fibers
  • elastic fibers
  • fibroblasts
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6
Q

What are the FUNCTIONS OF ENDOTHELIUM?

A
  1. Endothelium is specialized epithelium that acts as a semipermeable membrane between blood and the interstitial fluid.
  2. The endothelium presents a non thrombogenic surface.
  3. The endothelial cells regulate local vascular tone and blood flow by secreting a number of factors that stimulate smooth muscle contraction (ex: ACE) or relaxation (ex: NO).
  4. Under various conditions it secretes various growth factors , including proteins that promote proliferation of specific white blood cell lineages and cells that make up the vascular wall.
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7
Q

The endothelium presents a………………… surface.

A

non thrombogenic

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8
Q

Nitric oxide (NO) causes…………………. of blood vessels.

A

dilation/relaxation

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9
Q

Arteries carry blood from the heart to the body tissues. They are classified according to their size into what 3 categories?

A
  • Large elastic arteries
  • Muscular arteries
  • Arterioles
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10
Q

Which are the large elastic arteries?

A

Include aorta, large branches from the aortic arch (common carotid and subclavian ), common iliac arteries and pulmonary trunk.

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11
Q

Large elastic arteries are conducting vessels, bringing blood to periphery or the lungs. The presence of……………….. helps withstand the……….. pressure , thereby preventing excessive blood pressure in the arterial system.

A

elastic fibers

systolic

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12
Q

When ventricular pressure decreases during diastole, the elastic recoil of the………………. of large elastic arteries helps maintain arterial pressure.

A

elastic lamellae

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13
Q

Regarding the layers of large elastic arteries, tunica intima, tunica media, and tunica adventitia, which is the thickest?

A

tunica media

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14
Q

The tunica intima of large elastic arteries consists of………. and a……………………. of loose connective tissue with occasional smooth muscle cells, both oriented longitudinally .
The………………… marks the outermost boundary of intima and is a signature characteristic of arteries . It is composed of elastin and is fenestrated to permit diffusion of nutrients. It is specifically prominent in large arteries.

A

endothelium
sub endothelial layer
Internal elastic lamina

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15
Q

The tunica media of large elastic arteries is a thick layer with up to 70…………. arranged………………. lamellae, which increases with age. Elastic tissue is present in abundance, and gives it a yellowish appearance in situ.
Smooth muscle cells are………….. arranged and extra cellular matrix separates each lamella .

A

concentrically
fenestrated elastic
circularly

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16
Q

The tunica adventitia of large elastic arteries is typically about half of the thickness of the tunica media and is composed of a…………… arrangement of………….. and……….. fibers.
Fibroblasts and……………. are also present.

A

loose, irregular
elastic and collagen
vas vasorum

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17
Q

Muscular arteries are……………. arteries.

A

distributing

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18
Q

The tunica intima of muscular arteries consists of the endothelium, plus a thin…………… layer with a few smooth muscle fibers.

A

sub endothelial

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19
Q

The outer most boundary of muscular arteries tunica intima is defined by………….., which is very distinct and causes undulations of tunica intima.

A

internal elastic lamina

20
Q

The tunica media is a hallmark characteristic of muscular arteries. Why?

A

They have MORE smooth muscle and LESS elastic fibers in the tunica media compared to the elastic arteries. The smooth muscle is arranged concentrically.

21
Q

The……………….. marks the outer boundary of tunica media in muscular arteries.

A

external elastic lamina

22
Q

Is the external elastic lamia of the muscular arteries more or less distinct than the internal elastic lamina?

A

It is far less distinct.

23
Q

The tunica adventitia of muscular arteries is variable in thickness, about 1 /2 the thickness of tunica media! It is primarily composed of what fibers?
How it it oriented?

A

collagen fibers

longitudinally

24
Q

What else is present in the tunica adventitia of muscular arteries?

A

Vasa vasorum and free nerve endings.

25
Q

Smooth muscles of the tunica media of muscular arteries controls what?

A

The blood flow to an organ

26
Q

Arterioles are…………….. vessels. They are final terminal branches of arteries. They regulate the distribution of blood to different capillary beds by vasoconstriction or vasodilation in localized regions.

A

resistance

27
Q

Underneath the endothelium of arterioles is a very thin connective tissue layer. Arterioles have how many muscle layers in their tunica media?
The diameter of arterioles is less than one millimeter, and their adventitia is very thin and poorly defined.

A

one to a few smooth muscle layers

28
Q

Capillaries usually form a highly branched interconnected network. They arise from the end of arterioles and are formed by how many layers of endothelial cells?

A

a single layer

29
Q

What are pericytes?

A

cells located on the outside of the capillaries (and venules) that have numerous cytoplasmic extensions wrapping around the capillaries.

30
Q

What is the role of pericytes?

A

They regulate blood flow through the capillaries and are also responsible for division and formation of new vessels.

31
Q

What are the MAJOR FUNCTIONS OF CAPILLARIES?

A
  1. Selective permeability
  2. Synthetic/metabolic activity
  3. Antithrombogenic function
32
Q

What are the types of capillaries?

A

Continuous capillaries
Fenestrated capillaries
Sinusoidal ( discontinuous) capillaries

33
Q

Which type of capillaries is most abundant?

A

Continuous capillaries

34
Q

Continuous capillaries have no fenestrations in their endothelial cells. They are found extensively in what types of tissues?

A

muscle tissue, connective tissue, nervous tissue and exocrine glands.

35
Q

Fenestrated capillaries occur in tissues where rapid exchange occurs between blood and tissues, such as:

A

intestines, endocrine glands and kidneys.

36
Q

Sinusoidal (discontinuous) capillaries are larger in diameter and slow down circulating blood flow.
What is distinct about sinusoidal (discontinuous) capillaries?

A

Their endothelial wall is discontinuous and the endothelial cells have pores.
Specialized cells, such as macrophages, may be present along the endothelium.

37
Q

Where are sinusoidal (discontinuous) capillaries found?

A

liver, spleen, lymph organs, bone marrow and some endocrine glands.

38
Q

What do veins exhibit as they approach the heart?

A

a progressively larger lumen and thicker wall

39
Q

Veins normally run alongside corresponding arteries.

About ………..% of total blood volume is in venous circulation. Veins are capacitance or reservoir vessels.

A

70

40
Q

Vein walls are……….. and less elastic than those of arteries.

A

thinner

41
Q

Venules and small veins have thin walls, ……………lumens, and few smooth muscle cells. Their endothelium is simple squamous epithelium.

A

large

42
Q

Medium veins constitute the majority of veins in the body.
Their tunica intima consists of simple squamous endothelium with a very thin layer of sub endothelial connective tissue .
They have……………, which are delicate, thin leaflets formed from the tunica intima.

A

valves

43
Q

The tunica media of medium veins has a loose circular arrangement of smooth muscle fibers, with some collagen fibers and fibroblasts.
Their tunica………………. is the thickest tunic and has elastic fibers, collagen fibers and some smooth muscle cells arranged longitudinally.

A

adventitia

44
Q

Large veins are the major vessels returning blood back to the heart (ex: vena cavae & pulmonary veins).
They have a tunica……….. which is comparable to medium sized veins, but sub endothelial connective tissue which is thicker.

A

intima

45
Q

The tunica………. is poorly defined in large veins, however pulmonary veins have a considerable amount of circular smooth fibers.

A

media

46
Q

The tunica……………… in large veins is thick and well developed, and has many elastic fibers and longitudinally arranged collagen fibers. Vasa vasorum are also present here.

A

adventitia

47
Q

The lymphatic system collects excess tissue fluid (lymph) and returns it to the CVS. Lymph slowly moves through the system, propelled by movements of surrounding muscles and organs. Lymph vessels have unidirectional valves in the tunica…………….

A

intima

Medical Physiology (21 decks)

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