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Cardiology > Histology of Blood Vessels > Flashcards

Histology of Blood Vessels Flashcards

1
Q

Why does velocity of blood flow decrease along the arterial tree?

A

Greater and greater branches increase overall cross sectional area of blood flow despite smaller individual vessels

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2
Q

Where is there higher arterial pressure: systemic or pulmonary circulation?

A

systemic

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3
Q

What are the three basic layers of blood vessels?

A

intima, media, adventitia

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4
Q

Which basic blood vessel layers are present in capillaries?

A

only intima

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5
Q

4 substructures of the tunica intima

A

endothelial cells, basal lamina, subendothelial connective tissue, internal elastic lamina (arteries and veins)

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6
Q

3 substructures of the tunica media

A

smooth muscle cells, elastic fibers, collagen

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7
Q

5 substructures of the tunica adventitia

A

external elastic lamina in arteries, smooth muscle cells in large veins, loose connective tissue, vasa vasorum, nerves/nervi vascularis

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8
Q

Why do large conduit arteries contain so many elastic fibers?

A

to create tension that can “snap” and propel blood through conduit to smaller arteries/arterioles

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9
Q

Boundary between intima and media

A

internal elastic lamina

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10
Q

Arteries tend to have thicker/thinner walls relative to their luminal diameter than corresponding veins

A

thicker

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11
Q

In comparison to arteries of similar size, veins tend to have narrower/wider lumens, thinner/thicker walls with adventitia thicker/thinner than media.

A

wider lumens, thinner walls, thicker adventitia than media (vs arteries)

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12
Q

Role of muscular arteries

A

distributing vessels that control regional blood flow as needed (e.g. exercise, meal)

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13
Q

Defining features of muscular arteries

A

media: spiral smooth muscle with collagen fibers and fewer elastic fibers than elastic arteries w/o organized lamellae

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14
Q

How is blood flow regulated in muscular arteries?

A

by controlling luminal diameter and resistance to flow by contraction/relaxation of vascular smooth muscle under control of ANS, catecholamines (adrenal medulla), and local mediators

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15
Q

Role of small arteries/arterioles

A

resistance vessels that are the major determinant of arterial resistance to blood flow and therefore blood pressure (esp diastolic) and to control flow to microvascular bed

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16
Q

What regulates contraction/relaxation of medial smooth muscle in arterioles?

A

ANS, adrenal catecholamines, angiotensin II, local factors (e.g. NO, prostacyclin), pH, oxygen, carbon dioxide, adenosine

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17
Q

Role of capillaries

A

exchange vessels

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18
Q

Ultrastructure of capillaries

A

thin attenuated endothelial cells with a basal lamina that may be shared with pericytes

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19
Q

Role of pericytes

A

contractile function to modulate capillary flow, progenitors of vascular smooth muscle during angiogenesis

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20
Q

3 modes of exchange between capillary lumen and extravascular space

A
  1. passive diffusion
  2. active transport (pinocytic vessels or receptor mediated pinocytosis)
  3. passage between adjacent cells
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21
Q

Are all capillaries receiving blood flow at the same time in a given bed?

A

No. there is a smooth muscle sphincter for each capillary that regulates when it gets blood

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22
Q

What component of capillary beds always are perfused?

A

thoroughfare channels

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23
Q

3 classes of capillaries

A

continuous < fenestrated < discontinuous (with relation to exchange-ability)

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24
Q

Most common type of capillary

A

continuous

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25
Q

How are continuous capillaries sealed?

A

tight junctions, continuous basal lamina –> requires direct diffusion of gases or channel-mediated pinocytosis (carrier or active transport)

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26
Q

Where do we find fenestrated capillaries?

A

gut, kidney, hormonal structures

27
Q

Where do we find discontinuous capillaries?

A

spleen, liver, lymph nodes

28
Q

Do fenestrated capillaries have a complete basal lamina?

A

yes. only discontinuous has incomplete lamina

29
Q

T/F veins and venules can store variable volume of blood

A

T –> capacitance vessels can readily distend

30
Q

Do venules have an internal elastic lamina?

A

no

31
Q

Do veins have an internal elastic lamina?

A

may be incomplete

32
Q

Do veins/venules have an external elastic lamina?

A

no

33
Q

Do veins/venules have a vasa vasorum?

A

only largest veins

34
Q

What kind of capillaries are sinusoids?

A

disocntinuous

35
Q

What are the 2 exceptions to normal microcirculation principles?

A
  1. renal portal circulation: afferent arteriole –> cap bed –> efferent arteriole –> cap bed –> vein
  2. portal venous circulation: liver, hypothalamic venous circulation
36
Q

What structures prevent backflow in veins?

A

semilunar valves

37
Q

Smaller veins have higher/lower pressure than larger veins

A

higher

38
Q

Defining histologic features of veins

A

smaller media, larger adventitia than artery

39
Q

____ are an ultrastructural marker of endothelial cell differentiation.

A

Weibel-palade bodies: contain VWF (factor VIII) –> exposure during injury promotes platelet adherence and activation

40
Q

How do endothelial cells promote platelet adherence and activation during injury?

A
  1. reduced prostacycline and thrombomodulin

2. increased vWF and tissure factor exposure

41
Q

How do endothelial cells modulate immune cell migration?

A
  1. alteration of surface adhesion molecules (E-selectins and ICAMs) under influence of cytokines from other inflammatory cells (TNF alpha, IL1)
  2. alteration of immune cell function by release of PDGF and cytokines 1,6,8
42
Q

What products of endothelial cells promote vessel relaxation?

A

NO, prostacyclin

43
Q

What products of endothelial cells promote vessel contraction?

A

endothelin

44
Q

Can vascular smooth muscle contract tonically?

A

yes it has to –> constant tension –> constant stimulation by sympathetic ANS

45
Q

How does smooth muscle differ from striated muscle?

A
  1. consists of individual spindle cells with single nuclei
  2. no organized sarcomeres, z lines, t tubules, or troponin
  3. capacity to maintain tension for long periods with little energy expense
  4. slower contraction/relaxation
  5. longer time of linking of actin/myosin cross bridges
46
Q

How does smooth muscle contract?

A

intracellular calcium –> activates myosin –> move along actin filaments anchored to dense bodies ( which themselves are tethered to the cell membrane by intermediate filaments) scattered in cell cytoplasm

47
Q

What structure replaces z bands in smooth muscle?

A

dense bodies attached to actin filaments

48
Q

What tethers dense bodies in smooth muscle?

A

intermediate filaments connect dense bodies to cell membrane and to each other –> are compressed during contraction and provide restorative force during relaxation

49
Q

What feature of smooth muscle allows for greater degrees of contraction and maintenance of maximal contractile force at various cell lengths?

A

the actin:myosin ratio is higher than in striated muscle, which allows myosin to switch between actin filaments as it progresses –> thereby increasing it’s ability to “travel” along the muscle –> greater contraction distance

50
Q

How do myosin differ between smooth and striated muscle?

A

in smooth muscle myosin heads form sidepolar cross bridges with one actin filament per head –> contraction pulls two actin filaments in opposite directions

51
Q

How does calcium activate contraction of smooth muscle?

A

combines with calmodulin which activates myosin light chain kinase (MLC kinase) –> phosphorylates the MLC in the myosin head –> changes the shape of the head activating the actin binding site of the head and the atpase site

52
Q

What is required for ATP binding and actin binding in smooth muscle?

A

MLC phosphorylation

53
Q

What allows smooth muscle to hold tension without extensive energy burn?

A

slower cross bridge cycling means myosin head holds onto actin longer than in striated muscle (where atp releases the head faster) == latch state

54
Q

What can trigger vascular smooth muscle contraction?

A
  1. electromechanical coupling (AP)
  2. pharacochemical coupling (G proteins for norepi, angiotensin II, vasopressin, thromboxane A2)
  3. stretch channels
55
Q

What inactivates myosin in vascular smooth muscle?

A

MLC phosphatase

56
Q

What activates myosin in vascular smooth muscle?

A

MLC kinase

57
Q

What determines vascular smooth muscle tone?

A

balance of MLC kinase/phosphatase

58
Q

What mechanisms promote relaxation of vascular smooth muscle by regulating the balance of MLC kinase/phosphatase activity?

A
  1. reduction of intracellular calcium –> decrease MLC kinase activity
  2. stimulation of g proteins (b2 for epi, histamine receptors),
  3. NO mediated increase in cGMP and consequent activation of MLC phosphatase
59
Q

T/F there is a net loss of fluid as blood moves across capillary beds

A

T –> this is the liquid picked up by lymph vessels

60
Q

Do lymphatic capillaries have complete basal lamina?

A

no –> incomplete lamina without tight junctions –> kept open by anchoring filaments –> drain into larger vessels with one way valves (valves divide lymphatic vessels into segments called lymphangions) –> think lock system for boats (fill one lymphangion first and then push it all into the next)

61
Q

What is chylous lymph?

A

lymph with high lipid content (normally clear w/o red blood cells)

62
Q

Where do the thoracic duct and right lymphatic duct end?

A

left and right innominate veins

63
Q

What is the source of force that propels lymph through the lymphatics?

A

skeletal muscle or arterial contraction/external compression

Cardiology (41 decks)

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