I.
Vessels
The vessels of our circulatory system contain the blood in a closed system.
Red blood cells do not leave vessel, platelets seal tears in vessels and white
blood cells can migrate through vessel walls. Other water and dissolved substances
leave primarily at capillaries, only.
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on this image for an audio message
General sequence of vessels is: artery, arteriole, capillary, venule and vein. Except for capillary, vessels have two or three layers in their walls.
2. Tunica interna or intima
(innermost)
simple squamous epithelial
maintains smooth surface to promote flow
(in capillaries provides an easy exchange site)
3. Tunica media (middle
layer)
elastic fibers and smooth muscle
these tissues promote vasodilation and vasocontstriction
4. Tunica externa (adventitia)
mostly collagen fibers
protects blood supply from loss
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on this image for an audio message2. Larger arteries, near heart, have lots of elastic in tunica media to promote rebound keeping blood pressure continuous despite cyclical variation in blood pressure
3. Arteries function to
distribute blood via strong pressure developed by myocardial
contractions.
2. Arterioles are normally partly vasoconstricted. More ANS stimulation causes greater vasoconstriction. Less stimulation allows elastic rebound and vasodilation
3. Arterioles function to
regulate blood flow by changing vessel lumen diameter (vasodilation
& vasoconstriction ).
2. Usually a capillary next to nearly every cell in body (except epidermis, cornea and cartilage)
3. Primary function is to promote the exchange of water, transported materials & gases to cells or away from cells
2. Tend to be larger than arteries so most blood (~60%) is stored in veins and venules
3. Function to drain blood from areas serviced by capillaries
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on this image for an audio messageb. Pressure lowest near the heart (vena cavae)
c. Blood flow goes down
pressure gradient so Increased distance from heart results in decreased blood
pressure and therefore decreased blood flow.
In general, increased cardiac output = increased blood pressure = increased
flow
b. Blood vessel length
If length is increased then flow will be decreased. Normally fairly constant
c. Blood vessel diameter
(vasomotor responses)
Vasoconstriction reduces blood flow and vasodilation increases blood flow to
the following tissue or organ. Normally quite changeable, so arterioles affect
greatest change in blood flow. Regulated
via nervous system feedback with vasomotor center in medulla.
From a global point of view, global increased resitance (general vasoconstriction)
reduces flow to peripheral organs (like skin) resulting in increased blood pressure
and increased flow through rest of body (core organs like heart, lungs, liver,
brain). Reminder-shunting of blood flow during emergency, exercise, etc..
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2). decreased BP (stimulus) so less stretched baroreceptors so less stimulattion of medulla cardiovascular centers resulting in increased sympathetic stimulation (more Norepinephrine) to heart (increased HR) and vessels (increased vasoconstriction) resulting in increased BP (response)
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on this image for an audio message
2. Result of local control of arterioles allowing more/less blood flow (vasomotor responses)
3. Normal stimulus
is low [O2] or high[CO2] in skeletal muscle, brain tissue, skin
increased vasodilation of arteriole & blood flow and more O2 to tissues.
Exception is lungs
-- if low O2 levels in alveoli therefore increased vasoconstriction
promoting slower blood flow& greater gas exchange into blood
4. Chemicals produced by
tissues also affect vasomotor responses. For example, both Nitric oxide (NO)
and Histamine are vasodilators
B. Mechanisms of exchange
1. Solute exchange due to diffusion gradients
Cells require oxygen and nutrients and release carbon dioxide and nitrogenous
wastes.
b. CO2, urea and ammonia out of ECF
b. Osmotic pressure
blood OP high because of dissolved solutes in blood & low in EC
constant from arterial to venous sides of capillary
( promotes tendency for fluid to stay in vessels =reabsorption).
c. Balance
BP > OP at arterial end
of capillary
BP < OP at venous end
of capillary
As such, fluid tends to
leave at arterial end and fluid is reclaimed (almost all) at venous end
excess ECF fluid is removed by lymph vessels and
returned to veins via
lymphatic circulation.
if too little blood
drains from interstitial areas then it swells to cause edema
Compare and
contrast the exchange methods (and direction of flow) of the following: water,
ions, glucose, amino acids, oxygen, carbon dioxide, ammonia (urea).
2. Right side upper body
Branching off the
aortic arch,
Brachiocephalic artery (R only) which continues to the two following arteries:
R common carotid artery
(supplies neck, head, face) and
R subclavian artery (supplies shoulder), which continues to
R axillary artery (supplies armpit, arm) which continues to
R brachial artery (supplies arm) which continues to
R radial & ulnar arteries (supplies hand)
3. Left upper body
Also branching off
the aortic arch,
L common carotid artery
branches off aortic arch (supplies
neck, head, face)
L subclavian artery branches off aortic arch and continues to
axillary, brachial & radial arteries (same as R side)
4. Thorax, abdomen, legs
Aorta descends to
become
thoracic artery (supplies chest muscles) which
continues to
abdominal artery
(supplies abdominal organs. i.e., liver through hepatic artery , stomach via
gastric artery, small intestine via mesenteric artery , spleen via splenic artery,
kidneys via renal arteries) which continues to
common iliac artery (supplies pelvic organs genitalia, urinary bladder, colon) which continues to
femoral artery ( supplies thighs) which continues to
popliteal artery (supplies knees, legs) which continues to
tibial artery (supplies lower legs, feet)
5. Lungs
R Ventricle to pulmonary artery (poorly oxygenated blood, hgh in CO2)
R Atrium receives blood from superior vena cava, inferior vena cava and corornary vein/sinus
2. Upper Body (thorax)
superior vena cava receives blood from
brachiocephalic vein which receives blood from following two veins:
jugular vein (drains face
and neck) , and
subclavian vein which
receives blood from
axillary vein, which receives blood from
brachial vein, which receives blood from
radial and ulnar veins
3.Lower Body
inferior vena cava receives
blood from
common iliac veins, which receives blood from
femoral veins, which receives blood from
popliteal veins, which receives blood from
tibial veins
4. Hepatic portal system
hepatic portal system drains intestine, stomach and spleen through
liver before going back to heart via hepatic veins, hence "portal"
liver uses nutrients (carbs and proteins) before they get into CV system
also detoxifies chemicals before CV system
5. Head
brain of sinuses fill & then drain into jugulars
7. Lungs
pulmonary veins to L Atrium (highly oxygenated blood, low in CO2)
Construct the various arteries and veins that supply and drain, respectively, each body region and organ.
From vessels that supply the liver, infer the liver's various functions.
b. Umbilical artery (from iliac A) takes waste-laden & unoxygenated blood to placenta
c. Most blood goes through fetal liver shunt (ductus venosus) \ little blood in fetal liver
b. Ductus arteriosis - shunt
between pulmonary artery and aorta so
avoids pulmonary circulation
Human Anatomy and Physiology Courses
at St. Petersburg College
St. Petersburg/Gibbs Campus
5/2008