unit #5b: vessels and circulation

ch.22: cardiovascular vessels and circulation

name the 3 layers of the blood vessel wall. describe the subparts/composition of the layers.

* outer layer → tunic externa
* collagen fibers, elastic connective tissue
* middle layer → tunica media
* smooth muscle (allows vasoconstriction & vasodilation); site of external elastic membrane
* inner layer → tunica intima
* internal elastic membrane, endothelium

for artery vs. vein, describe their differences in:

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1. lumen size/shape
2. wall thickness
3. endothelium pattern
4. valves (present or not?)

artery


1. small, circular lumen
2. thick walls
3. pleated endothelium (for vessel extension)
4. NO valves

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vein


1. large, collapsed lumen
2. thin walls
3. smooth endothelium
4. valves present

what are the 3 types of arteries?

* elastic arteries
* muscular arteries
* artrioles

for elastic arteries, describe their:

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1. endothelium of tunica intima presence
2. internal elastic membrane of tunica intima thickness
3. tunica media thickness
4. tunica externa thickness
5. lumen size
6. example/location

1. present endothelium
2. thick internal elastic membrane
3. mediumly-thick tunica media
4. thick tunica externa
5. large lumen size (1.5\~2.5cm)
6. found in pulmonary a., aorta

for muscular arteries, describe their:

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1. endothelium of tunica intima presence
2. internal elastic membrane of tunica intima thickness
3. tunica media thickness
4. tunica externa thickness
5. lumen size
6. example/location

1. present endothelium
2. mediumly-thick internal elastic membrane
3. thick tunica media
4. mediumly-thick tunica externa
5. medium lumen size (4mm)
6. found in brachial a., femoral a.

for artriole arteries, describe their:

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1. endothelium of tunica intima presence
2. internal elastic membrane of tunica intima thickness
3. tunica media thickness
4. tunica externa thickness
5. lumen size
6. example/location

1. present endothelium
2. thin internal elastic membrane
3. thin tunica media
4. thin tunica externa
5. small lumen size (0.03mm)
6. found next to capillary beds

for capillaries, describe their:

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1. endothelium of tunica intima presence
2. internal elastic membrane of tunica intima thickness (or presence?)
3. tunica media thickness (or presence?)
4. tunica externa thickness (or presence?)
5. lumen size
6. example/location

1. present endothelium
2. no internal elastic membrane
3. no tunica media
4. no tunica externa
5. very small lumen size (0.01mm)
6. found in capillary beds, alveoli in lungs

what are 3 types of capillaries? how many and what type of cells typically make up capillary lumen?

* continuous capillaries
* fenestrated capillaries
* sinusoids

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* 1\~3 simple squamous epithelium cells

describe continuous capillaries. how common is this type of capillary?

* complete endothelium (little/no gaps)
* most common; found across body

describe fenestrated capillaries. where are they located?

* perforated/porous-walled endothelium; allows transfer of larger molecules (polypeptides and small proteins) to/from lumen
* located in choroid plexus, endocrine glands, kidney

describe sinosoid-type capillaries. where are they located?

* perforated capillaries that allow movement of even larger proteins or blood cells to cross endothelium
* located in liver, bone marrow, spleen

define capillary beds. what type of exchange do they allow?

* sites of capillaries in which all blood to travel between artery and vein
* site of gas exchange

describe autoregulation. what parts of the capillary bed are involved in this process?

* autoregulation: controls flow of blood thru capillary beds depending on metabolic needs, bodily movements, etc.
* ex. lessen blood to flow thru if resting
* involves:
* anastomoses
* thoroughfare channels
* metarterioles (with precapillary sphincters)

describe the various parts of the capillary bed:

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1. anastomoses
2. thoroughfare channels
3. metarterioles (with precapillary sphincters)

1. anastomoses: connect artery to artery, artery to vein, or vein to vein; allows blood to bypass capillary bed due to blockages
2. thoroughfare channels: connect arterioles to venules across/thru capillary beds (w/o sending blood thru capillaries)
3. metarterioles (with precapillary sphincters): vessels within capillary beds w/ smooth muscles “valves” that can shut on/off blood flow to regions of bed

describe veins. how much volume does it hold? what does it make up? in terms of venoconstriction, what is its cause and what does it do to blood?

* veins: carry blood at low pressure; return blood to heart
* 65\~70oz of blood volume
* makes up blood reservoir
* sympathetic stimulation → venoconstriction → returns blood back to circulation

what are the 3 types of veins?

* venules
* medium-sized veins
* large veins

describe venules.

postcapillary venules; smallest vessels on “return side” of capillary beds

define medium-sized veins. what pushes the blood toward the heart? what prevents backflow of blood?

* make up most deep veins in blood (radial, popliteal, etc.); merging of venules
* blood is pushed toward heart by skeletal muscle pump (contraction of skeletal muscles during walking, breathing, etc.)
* extensions of epithelium forms “parachute shaped” one-way valves to prevent backflow of blood

describe large veins. do they have valves?

* merging of medium-sized veins; includes superior and inferior venae cavae
* no valves present

describe the hepatic portal system. what are the 4 hepatic portal veins?

* hepatic portal system: set of veins that drain blood from organs in peritoneal cavity and deliver it to liver before returning to general circulation; substances absorbed from food → processed by liver
* hepatic portal vein → gastric v., inferior mesenteric v., superior mesenteric v., splenic v.

blood leaves the liver through the what? and immediately drains into the what?

blood leaves liver thru hepatic vein and almost immediately drains into inferior vena cava

what supplies the fetus with oxygen and nutrients? blood bypasses most of the what?

* oxygen and nutrients supplied by placenta
* most blood bypasses pulmonary circuit (lungs)

describe the pathway of oxygenated blood in fetal circulation.

1. oxygenated blood enters umbilical vein
2. flows into ductus venosus (near liver)
3. into inferior vena cava
4. up to right atrium

* 75%: right ventricle → pulmonary trunk → ductus arteriosus → aorta
* 25%: foramen ovale → left atrium


5. out of body

how does deoxygenated blood return to the placenta in a fetus?

returns to placenta thru umbilical arteries (2; near internal iliac arteries)

at birth, what does the:

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1. foramen ovale
2. ductus venosus
3. ductus arteriosus

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turn into?

1. foramen ovale → fossa ovalis
2. ductus venosus → ligamentum venosum
3. ductus arteriosus → ligamentum arteriosum