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FoundSci Unit 6 > Vessel I > Flashcards

Vessel I Flashcards

1
Q

What do arterial vessels do and what do they lead to?

A

Carry blood away from the heart

Aorta -> Arteries of decreasing size -> arterioles

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2
Q

What is microcirculation and what is its path?

A

Regulates blood flow in and out of capillary beds - metarterioles and postcapillary venules

2-way fluid exchange with tissues - capillaries

Metarterioles -> capillaries -> tissue -> postcapillary venules

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3
Q

What do venous vessels do and what is their path?

A

Carry blood towards the heart

Venules -> veins of increasing size -> SVC/IVC

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4
Q

What are the 3 layers of blood vessels?

A

Tunica intima

Tunia media

Tunica externa

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5
Q

What is the function and structure of tunica intima?

A

Endothelium lines vessels - interface in direct contact with bloodstream

Subendothelial CT anchors endothelium to rest of vessel

Internal elastic lamina

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6
Q

What is the structure and function of the tunica media?

A

Middle, muscular layer

Smooth muscle and elastic CT allow the vessel to change its lumen diameter in order to restrict or accommodate volume of blood flowing through it

External elastic lamina

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7
Q

What is the structure and function of the tunica externa?

A

Outer layer or tunica adventitia

Connects/anchors vessels to surrounding tissues

Protective pathway for smaller vessels and nerves that supply the vessel wall

CT with collagen and elastic fibers

Blood vessels and nerves that supply the vessel wall run in this layer

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8
Q

What forces occur to vessels and affect their structure?

A

Distance from heart

Blood pressure

Blood flow (speed and direction)

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9
Q

What are the components of the tunica externa?

A

CT layer - mostly collagen I fibers, elastic fibers, fibroblasts, white fat cells

Blood vessels and nerves - present in all arteries/veins > 1mm diameter, vasa vasorum, nervi vasorum

Merges with loose CT surrounding vessels

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10
Q

What are the components of the tunica media?

A

Mostly smooth muscle cells in concentric layers - lumen diameter changes when smooth muscle cells in the media contract or relax

Variable # of elastic lamellae (concentric sheets of elastin) and elastic fibers

External elastic lamina (EEL) - thicker sheet of elastin outside the tunica media, fenestrated that allow nervi and vasa vasorum to contact media

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11
Q

What are the components of the tunica intima?

A

Endothelium - simple squamous epithelium + BM

Subendothelium - mostly loose CT fibroblasts, few smooth muscle cells

Internal elastic lamina (IEL) - thicker sheet of elastic outside tunica intima, fenestrated so aids in diffusion from lumen to tunica media and allows endothelial cells to contact smooth muscle cells in tunica media

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12
Q

What lines the lumen in all blood vessels?

A

Simple squamous epithelium called the endothelium - endothelial cells and tunica intima

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13
Q

What is the benefit of the long axis of endothelial cells being parallel with the direction of blood flow?

A

Streamlining reduces the amount of shear stress experienced by endothelial cells as blood flows over them

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14
Q

What are the functions of the endothelium?

A

Maintain structural integrity of the endothelium

Coordinate endothelial cell activities

Maintain a selectively permeable barrier

Regulate inflammatory and immune cell traffic

Regulate vessel formation during angiogenesis

Modulate smooth muscle activity, which determine vessel diameter and vascular resistance to blood pressure/flow

Regulates thrombus function

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15
Q

How does the endothelium maintain structural integrity?

A

Junctional complexes

Hemidesmosomes and focal adhesions

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16
Q

How does the endothelium coordinate endothelial cell activities?

A

Gap junctions

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17
Q

How does the endothelium maintain a selectively permeable barrier?

A

Regulate access to paracellular pathway

Exchange of gas and nutrients across the endothelium via pinocytotic vesicles, receptor mediated endocytosis, active transport, and diffusion

Surface receptors - for histamines, LDL, insulin

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18
Q

How does the endothelium regulate inflammatory and immune cell traffic?

A

Endothelial cells extend cell adhesion molecules that can bind specific WBCs

WBCs then work with endothelial cells to unlock cell junctions

19
Q

How do WBCs get access to underlying tissues?

A
  1. Macrophages release cytokines in response to stimulus
  2. Endothelial cells extend CAMs
  3. Circulating neutrophil binds CAMs, rolls along endothelium surface
  4. Neutrophil expresses integrins
  5. Integrins bind receptors in endothelium and junctions unlock
  6. Neutrophil enters underlying CT between endothelial cells
20
Q

How do endothelium modulate smooth muscle activity?

A

Myoendothelial junctions

Secreting chemicals that promote vasoconstriction

Secreting chemical that promote vasodilation

21
Q

What is secreted to promote vasoconstriction?

A

Endothelins - promote smooth muscle contraction

22
Q
A
23
Q

What is secreted to promote vasodilation?

A

NO and prostacyclin both promote smooth muscle relaxation

24
Q

What is the myoendothelial junction?

A

Physical connection between an endothelial cell (intima) and a smooth muscle cell (media)

Endothelial cell extends a cellular process through BM and IEL (fenestrated)

Myoendothelial junctions contain many many gap junctions

25
Q

What does increased shear stress also stimulate besides vasodilation?

A

NO production by endothelial cells

26
Q

How does the endothelium regulate thrombus formation?

A

Thrombus - clot that forms in a vessel and stays there

Release anticoagulants - prevent fibrinogen from being converted into fibrin

Release antithrombogenic substances - interfere with platelet aggregation (prostacyclin)

Release thrombolytic substances - break down clots (tissue plasminogen activator)

27
Q

What is released when a vessel is torn?

A

Endothelial cells release prothrombogenic substances that promote formation of protective clots, which seal tears and prevent blood loss (von Willebrand factor and other clotting factors)

28
Q

What are Weibel-Palade bodies?

A

Membrane-bound organelles unique to endothelial cells

Store von Willebrand factor and some proteins that mediate immune/inflammatory responses

After vessel injury, fuse with cell membrane and secrete that factor

29
Q

What is von Willebrand factor?

A

Prothrombogenic glycoprotein that promotes platelet adhesion

30
Q
A
31
Q

What is different between arteries and veins in regards to walls and lumens?

A

Arteries have thicker walls and smaller lumens vs veins of same external diameter

Arteries need thicker walls to deal with high BP and need more smooth muscle to control blood flow and resist pressure of blood on arterial walls

32
Q

List the arteries in order from largest diameter to smallest diameter.

A

Elastic (large) arteries

Muscular (medium) arteries

Small arteries

Arterioles

Metarterioles

Capillaries

33
Q

What are the elastic arteries and their function?

A

Aorta and its main branches

Transport large volumes of blood away from the heart

Ability to stretch accomodates large changes in blood volume and BP between systole and diastole

34
Q

What is the structure of elastic arteries?

A

Subendothelium - some smooth muscle cells

Tunica media - alternating layers of smooth muscle and elastic lamella

Tunica externa - type I collagen

35
Q

What are muscular arteries?

A

Distributing arteries that control the distribution of blood to major body regions

36
Q

What is the structure of muscular arteries?

A

Subendothelium - few smooth muscle cells, IEL prominent

Tunica media - elastic lamellae less prominent, EEL often prominent

Tunica externa - relatively thick

37
Q

What are small arteries?

A

Smaller distributing arteries that control the distribution of blood to smaller body regions

38
Q

What is the structure of small arteries?

A

Subendothelium - IEL usually present

Tunica media - 3-10 layers of smooth muscle, no elastic lamellae, EEL not usually visible

Tunica externa - thin, no vasa or nervi vasorum

39
Q

What are arterioles?

A

Main resistance vessels in circulation

Very vasoactive - constantly dilating or constricting

Greatly influence volume of flow to a localized area

40
Q

What is the structure of arterioles?

A

Subendothelium - very little

Tunica media - 1-2 complete layers of smooth muscle

Tunica externa - functionally absent, no vasa or nervi vasorum

41
Q

Where does most vasoconstriction occur?

A

Happens in Arterioles

42
Q

Vasoconstriction

A

Of Arterioles is stimulated by sympathetic (vasomotor) nerve fibers that discharge norepinephrine

Diffuses to smooth muscle in tunica media and causes contraction

43
Q

Vasodilation

A

Parasympathetic nerve fibers stimulate the arteriole’s endothelium to release NO

Diffuses to smooth muscle in tunica media and induces relaxation

FoundSci Unit 6 (14 decks)

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