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Anatomy > Ch 20 > Flashcards

Ch 20 Flashcards

1
Q

what is the difference between arteries, veins and capillaries

A

Arteries: carry blood away from heart

Veins: carry blood back to heart

Capillaries: connect smallest arteries to smallest veins

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2
Q

what are the three layers of the walls of arteries and veins

A

tunica interna,
tunica media,
tunica externa

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3
Q

describe the tunica interna

A

lines the blood vessel and is exposed to blood

Endothelium: simple squamous epithelium overlying basement membrane and sparse layer of loose connective tissue

  • Acts as a selectively permeable barrier
  • Secretes chemicals that stimulate dilation or constriction of the vessel
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4
Q

describe the tunica media

A

middle layer

consists of smooth muscle, collagen, and elastic tissue

strengthens vessels and prevents blood pressure from ruptureing them

regulated diameter of blood vessel

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5
Q

tunica externa (tunica adventitia)

what is the vasa vansorum

A

outermost layer

consists of loose connective tissue that often merges with that of neighboring blood vessles, nervous or other organs

anchors the vessel and provides passage for small nerves and lymphatic vessels

vasa vansorum: small vessles that supply blood to outer part of large vessels

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6
Q

what are arteries called

A

resistance vessels because of their strong resilient tissue structure

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7
Q

how are arteries classified and what are the different arteries

A

they are classified by size and consist of

  1. conducting arteries (elastic or large)
  2. distributing artereies (muscular or medium)
  3. resistance arteries (small)
  4. metaerterioles
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8
Q

what do conducting (elastic or large) arteries do

A

Biggest arteries

Aorta, common carotid, subclavian, pulmonary trunk, and common iliac arteries

Have a layer of elastic tissue, internal elastic lamina, at the border between interna and media

External elastic lamina at the border between media and externa

Expand during systole, recoil during diastole

Expansion takes pressure off smaller downstream vessels

Recoil maintains pressure during relaxation and keeps blood flowing

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9
Q

what are distributing arteries (muscular or medium)

A

Distributes blood to specific organs

Brachial, femoral, renal, and splenic arteries

Smooth muscle layers constitute three-fourths of wall thickness

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10
Q

Resistance (small) arteries

A

Arterioles: smallest arteries

Control amount of blood to various organs

Thicker tunica media in proportion to their lumen than large arteries and very little tunica externa

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11
Q

what are metarterioles

A

In some places, short vessels that link arterioles to capillaries

Muscle cells form a precapillary sphincter around entrance to capillary

Constriction of these sphincters reduces blood flow through their capillaries

Diverts blood to other tissues

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12
Q

what is an aneurysm

A

weak point in artery or heart wall

Forms a thin-walled, bulging sac that pulsates with each heartbeat and may rupture at any time

Dissecting aneurysm: blood accumulates between tunics of artery and separates them, usually because of degeneration of the tunica media

Most common sites: abdominal aorta, renal arteries, and arterial circle at base of brain

Can cause pain by putting pressure on other structures

Can rupture causing hemorrhage

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13
Q

what can cause an anuerysm

A

Result from congenital weakness of blood vessels, trauma, or bacterial infections

Most common cause is atherosclerosis and hypertension

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14
Q

what are capillaries

what are they composed of

what are they absent in

A

exchange vessels: site where gases, nutrients, wastes, and hormones pass between the blood and tissue fluid

The “business end” of the cardiovascular system

Composed of endothelium and basal lamina

Absent or scarce in tendons, ligaments, epithelia, cornea, and lens of the eye

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15
Q

what are the three capillary types and how do you distinguish between them

A

Three capillary types distinguished by ease with which substances pass through their walls (permeability):

continuous capillaries,

fenestrated capillaries,

sinusoids

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16
Q

Describe continuous capillaries

A

occur in most tissues

Endothelial cells have tight junctions forming a continuous tube with intercellular clefts

Allow passage of solutes such as glucose

Pericytes wrap around the capillaries and contain the same contractile protein as muscle

Contract and regulate blood flow

17
Q

describe fenestrated capillaries

A

kidneys, small intestine

Organs that require rapid absorption or filtration

Endothelial cells riddled with holes called filtration pores (fenestrations)

Spanned by very thin glycoprotein layer

Allow passage of only small molecules

18
Q

describe sinusoids

A

discontinuous capillaries:
liver, bone marrow, spleen

Irregular blood-filled spaces with large fenestrations

Allow proteins (albumin), clotting factors, and new blood cells to enter the circulation

19
Q

describe capillary beds

A

are networks of 10-100 capillaries

Usually supplied by a single arteriole or metarteriole

At distal end, capillaries transition to venules

20
Q

describe veins

A

Greater capacity for blood containment than arteries

Thinner walls, flaccid, less muscular and elastic tissue

Collapse when empty, expand easily

Have steady blood flow

Merge to form larger veins

Subjected to relatively low blood pressure

21
Q

what are the three (4) types of veins

A

postcapillary venules

medium veins

venous sinuses

large veins

22
Q

describe post capillary venules

A

smallest veins

Even more porous than capillaries so also exchange fluid with surrounding tissues

Tunica interna with a few fibroblasts and no muscle fibers

Most leukocytes emigrate from the bloodstream through venule walls

23
Q

describe medium veins

  • what are the layers of it in proportion to eachother
  • what disrupts part of this function
  • what helps propel blood back to heart

-

A

—up to 10 mm in diameter

Thin tunica media and thick tunica externa

Tunica interna forms venous valves

Varicose veins result in part from the failure of these valves

Skeletal muscle pump propels venous blood back toward the heart

24
Q

what are things that can create issues with veins

A

Hereditary weakness, obesity, and pregnancy also promote problems

25
Q

____________ are varicose veins of the anal canal

A

hemorrhoids

26
Q

describe venous sinuses

A

Veins with especially thin walls, large lumens, and no smooth muscle

Dural venous sinus and coronary sinus of the heart

Not capable of vasomotor responses

27
Q

describe large veins

A

diameter larger than 10 mm

Some smooth muscle in all three tunics

Thin tunica media with moderate amount of smooth muscle

Tunica externa is thickest layer

Contains longitudinal bundles of smooth muscle

Venae cavae, pulmonary veins, internal jugular veins, and renal veins

28
Q

what is the simplest and most commone circulatory route for blood

A 
heart
arteries 
arterioles
capillaries
venules
veins

Passes through only one network of capillaries from the time it leaves the heart until the time it returns

29
Q

what is the portal system

A

an exception to the common circulatory route

Blood flows through two consecutive capillary networks before returning to heart (happens for….

  • Between hypothalamus and anterior pituitary
  • In kidneys
  • Between intestines to liver
30
Q

what are anastomosis

and name the different types

A

convergence point between two vessels other than capillaries

types
-anteriovenous anstomosis

  • venous anastomosis
  • arterial anastomosis
31
Q

describe Arteriovenous anastomosis (shunt)

A

Artery flows directly into vein, bypassing capillaries

32
Q

describe Venous anastomosis

A

Most common

One vein empties directly into another

Reason vein blockage is less serious than arterial blockage

33
Q

describe arterial anasomosis

A

two arteries merge

Provides collateral (alternative) routes of blood supply to a tissue

Coronary circulation and common around joints

34
Q

what controls the blood flow to capillaries

describe result of contraction or relaxed state

A

Most control of flow involves constriction of arterioles that are upstream from the capillaries\

Within the capillary bed, precapillary shincters control flow

When sphincters are relaxed, capillaries are well perfused with blood

When sphincters contract, they constrict the entry to the capillary and blood bypasses the capillary

35
Q

at any given time, _________ of bodys capillaries are ___________

A

At any given time, three-fourths of body’s capillaries are shut down

36
Q

what are varicose veins

A

Varicose veins - Blood pools in the lower legs of people who stand for long periods stretching the veins
\
Cusps of the valves pull apart in enlarged superficial veins, further weakening vessels

Blood backflows and further distends the vessels, their walls grow weak and develop into varicose veins

talked about in medium veins

Anatomy (20 decks)

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