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242 - 18 & 19 > 19 1-8 > Flashcards

19 1-8 Flashcards

1
Q

C+C Arteries and Veins

A
  1. LUMEN DIAMETER small large
  2. WALL THICKNESS Thick Thin
  3. CROSS SECTION SHAPE Cylindrical Elongated
  4. Blood flow Away fr heart To heart
  5. BP RANGE 93-35 mmHg 20-0 mmHg
  6. Valves No Yes
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2
Q

Tunica intima

A

Innermost layer

STRUCTURE: composed of endothelium and a subendothelial layer (areolar ct), continuous with the endocardium

FUNCTION: provides smooth surface to reduce friction between the vessel wall and the blood, releases local chemicals (Endothelins - vasoconstrictors and NO/vasodilator), blood clotting

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3
Q

Tunica media

A

Middle layer

STUCTURE: composed of smooth muscle and elastic fibers, innervated by ANS

FUNCTION: controls vasoconstriction/dilation of vessels, blood flow to tissues

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4
Q

Tunica Externa

A

(adventitia)

STUCTURE: Areolar ct, elastic and collagen fibers. Has vasa vasorum in very large vessels.

FUNCTION: Protects, reinforces, anchors the vessel to surrounding structures.

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5
Q

Vasa Vasorum

A

Network of small arteries in the tunica externa of very large blood vessels (nourish external tissue)

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6
Q

Vasodilation

A

Lumen diameter increases as smooth muscle relaxes

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7
Q

Vasoconstriction

A

Lumen diameter decreases as smooth muscle contracts

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8
Q

Elastic/conducting arteries

A

STRUCTURE: Contain large amounts of elastin

FUNCTION: Pressure reservoirs, Conduct blood away from the heart, Stretch and recoil

Ex. Aorta

Expand and recoil as the heart ejects blood - has a pressure smoothing effect blood flows continuously instead of stopping or starting with the heartbeat. Must have low compliance.

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9
Q

Muscular/distributing arteries

A

STRUCTURE: More smooth muscle and less elastic than Elastic arteries.
Greatest proportion of tunica media
Elastic membrane on each face of the tunica media.

FUNCTION: Distributing arteries, Deliver blood to specific body organs/tissues, Active in vasoconstriction, less distensible.

I.e. Brachial artery

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10
Q

Arterioles/resistance vessels

A

STRUCTURE: Smallest of the arteries, highly innervated by ANS

FUNCTION: Resistance vessels - vasoconstriction/vasodilation - shunting. Regulate blood flow into capillary beds through vasodilation/constriction.

Level of resistance can be regulated neurally/hormonally/by local influence.

Usually slightly constricted, a phenomena called vasomotor tone or arteriolar tone (partially contracted in the absence of any external factors).

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11
Q

Aneurysm

A

Thinning and ballooning out of an arterial wall often seen in elastic and muscular arteries.

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12
Q

aortic dissection

A

A tear in the inner wall of the aorta that causes blood flow between the layers of the wall.

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13
Q

Capillaries

A

GENERAL STRUCTURE: Thin tunica intima, lumen diameter just large enough for RBCs to pass.

GENERAL FUNCTION: Allow for the exchange of substances between the blood and interstitial fluid. All cells in the body must be within 1mm of a capillary for adequate diffusion. Exchange vessels

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14
Q

Continuous capillaries

A

Most common.

LOCATION: skin, muscles, lungs, CNS.

STUCTURE: Tight junctions, with some gaps (intercellular clefts). Exception is BBB which is continuous.

FUNCTION: Least permeable of capillaries, Intercellular clefts allow for transport processes of diffusion/pinocytosis/bulk flow.
Permeable to water-soluble substances having small molecular size and lipid soluble substances.

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15
Q

Fenestrated capillaries

A

LOCATION: small intestine, ciliary processes of eye, chorois plexus, endocrine glands, kidneys.

STRUCTURE: Have oval pores/fenestrations

FUNCTION: Active absorption and filtration. More permeable than continuous caps, allow small intestine to absorb food, filtration in kidneys, hormones to enter blood.

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16
Q

Sinusoid capillaries

A

LOCATION: liver, bone marrow, spleen, some endocrine glands.

STRUCTURE: Highly modified, leaky capillaries. Large usually fenestrated lumens, basement membrane with large gaps.

FUNCTION: Allow large molecules and even blood cells to pass between blood and surrounding tissues.
Blood flows sluggishly through the tortuous channels allowing time for it to be modified.

17
Q

Pericytes

A

Smooth muscle like cells that stabilize capillaries.

18
Q

Capillary bed

A

Interweaving network of capillaries consisting of a metarteriole thoroughfare channel and true capillaries.

A terminal arteriole feeding the bed leads into a metarteriole which connects with the postcapillary venule that drains the bed.

True caps branch off at the proximal end of the metarteriole and rejoin at the distal end.

Precapillary sphincters surround the roots of the true caps and act as valves to regulate blood flow into the capillary.

19
Q

Metarteriole thoroughfare channel

A

A short vessel that directly connects the arteriole and venule at opposite ends of a capillary bed.

20
Q

True capillaries

A

Branch off the metarteriole and are the true exchange vessels.

21
Q

Perfusion

A

The amount of blood entering capillaries per time unit/per gram of tissue.

22
Q

Venules

A

STRUCTURE: small ones are all endothelium, larger sized have one or two layers of smooth muscle cells and a thin tunica externa. Postcapillary venules are extremely porous.

FUNCTION: carry blood away from cap beds. Allow fluid and WBCs to move easily btw blood/tissue

23
Q

Veins

A

STRUCTURE: Large diameter. Have valves. Have three distinct tunics. Little smooth muscle and elastin in the tunica media which is thin. Tunica externa is the heaviest layer with thick collagen and elastic networks.

FUNCTION: Carry blood to the heart. Capacitance vessels/Blood reservoirs.

24
Q

Venous valves

A

Formed from folds of the tunica media. Prevent blood from pooling. Abundant in limbs, absent from thoracic/abdominal/CNS.

25
Q

How are veins blood reservoirs?

A

Veins can hold 55-65% of the body’s blood at one time.

Large lumens and thin walls give veins high compliance so that a small amount of pressure can cause a large degree of expansion.

Storage in important because blood may be shunted from one area to another to meet the body’s needs.

26
Q

Venous system adaptations

A

Structural: 1. large diameter 2. valves.

Functional: 1. Skeletal muscle pump (skel musc contraction milks blood toward heart)
2. Respiratory pump (shifting pressure between ab cavity and thoracic cavity)

27
Q

Simple pathways vs. Alternative pathways

A

Simple pathway: artery → arteriole → capillary bed → venule → vein Alternatives…..

Anastomoses: Joining of vessels. Arterial - arteries supplying the same area often merge providing alternate pathways (collateral channels). Arteriovenous - metarteriole channel shunts. Veins - connect freely and often (blocked vein rarely causes tissue death.)

Portal system: two capillary beds connected by a vein.

28
Q
  1. Explain the distinguishing features of the tunics found in arteries, capillaries and veins.
A

Caps: only endothelium.

Veins: thicker tunica externa. fibrous tissue is more than smooth muscle, very little elasticity

Arteries: thicker tunica media. significant amount of elastic fibers so they can stretch and recoil, but also significant smooth muscle.

29
Q

C+C Pressure reservoir vs. Blood reservoir

A

Vessel type: Arteries Veins

Structure: Elastic Large lumen/thin walls

Compliance: low High

Mechanism: By clamping down/recoiling, arteries maintain pressure.
By expanding, veins can hold a large amount of blood.

30
Q

Compliance

A

How easy it is to inflate something. Low compliance = hard to stretch, High compliance = easy to stretch

31
Q

Vasomotor tone

A

Most arterioles are under vasomotor tone - they are slightly constricted by the ANS.

Usually slightly constricted, a phenomena called vasomotor tone or arteriolar tone (partially contracted in the absence of any external factors).

32
Q

Two ways to regulate flow in cap beds?

A

Arterioles/sympANS, precapillary sphincters

33
Q

Vasomotion

A

Precapillary sphincter responding to local conditions

34
Q

Types of capillaries

A

Continuous, fenestrated, sinusoidal

35
Q

Types of arteries

A

Elastic/conducting
Muscular/distributing
Arteriole/resistance

36
Q

Arteriole resistance can be controlled by?

A

Level of resistance can be regulated neurally/hormonally/by local influence.

242 - 18 & 19 (8 decks)

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