U7 - circulatory system Flashcards
Circulatory system
- delivers oxygen and nutrients to body cells
- remove carbon dioxide and other waste products
- circulates cells of the immune system
- closed system
arteries
- blood flows out of the heart into the arteries
- walls are thick and elastic: contain a layer of muscle
- carry blood from heart to tissues
Arterioles
- small arteries branch into arioles
- small ver of arteries: muscle walls
- carry blood from arteries to cappillaries
Capillaries
- arterioles lead to networks of capillaries
- narrow vessels to fit single blood cells
- thin walls, only a cell layer
- carry blood from arterioles to venules within the tissues
Venules
- cappillary beds drain into venules
- walls are thin because they contain less muscle then arterioles
- carry blood from capillaries to veins
Veins
- many venules drain into a larger vein
- contain less muscle then arteries
- contain valves
- carry blood from venules to heart
Portal systems
- portal veins are special vessels that carry blood between capillary beds
- have thin walls and valves like veins
Heart
- muscle is involuntary
- heart cells contract on their own
- two pumps, right (lungs), left (body)
- each pump made of two chambers atrium, and ventricle
- septum divides them
Right side of the heart
- venous blood returns
- anterior, posterior vena cava connect to right atrium
- blood is pumped out of right ventricle into pulmonary trunk which splits into right and left pulmonary arteries
Left side of the heart
- blood returns from lungs
- right, left pulmonary veins connect to the left atrium
- blood is pumped out of left ventricle into aorta
AV valves
- prevent back flow from ventricles to atria
- valves open when atria contracts
- when ventricle contracts valves close
semi lunar valves
- prevent back flow from aorta and pulmonary trunk into ventricles
- open when ventricles contract
- close when ventricles relax
external anatomy
- on the front and sides of the heart are
vessels which give it a rich blood supply
blood flows to both sides of the heart through
right and left coronary arteries, and drains
into the right and left coronary veins
Pulmonary vs systematic circulation
-pulmonary: venous blood is pumped into right side to lungs release CO2 and pick up O2
-systematic: – oxygenated blood is
pumped from the left side to the body
tissues to release O2 and pick up CO2
path of blood cells
aorta → body → vena cava → R atrium → right AV valve → R ventricle → pulmonary semi-lunar valve → pulmonary artery → lungs → pulmonary vein → L atrium → left AV valve → L ventricle → aortic semi-lunar valve → aorta
heartbeat is coordinated to three special nerve regions
sinoatrial (SA) node – in the upper wall of
the right atrium; sets the rhythm, causes
atria to contract, and stimulates AV node
atrioventricular (AV) node – in the base of
the right atrium, delays signal slightly before
stimulating Purkinje fibers
Purkinje fibers – within the septum and the
ventricles, cause ventricle contraction
sequence of heartbeat
SA node begins heartbeat signal every 0.85
seconds (~70 per minute), causing atria to
contract
when this signal reaches the AV node it is
slightly delayed for the atria to empty
signal passes into Purkinje fibers, which
cause the ventricles to contract from the
bottom to the top
blood pressure in lungs
systolic – higher pressure caused by heart
contraction
diastolic – lower pressure caused by heart
relaxation (and artery elasticity)
normal B.P. = 120/80 (systolic/diastolic)
abnormal blood pressure
hypertension – blood pressure is too high
systolic > 140 or diastolic > 90
caused by many factors: obesity, excessive salt,
and genetics
hypotension – blood pressure is too low
systolic < 90 or diastolic < 60
caused by low blood volume, weak heart
contraction and dilation of the blood vessels
Measurement of arm blood pressure
blood pressure is measured by an inflatable
cuff around the arm
when the pressure in the cuff matches
systolic pressure, blood supply is cut off
the cuff is then deflated until blood begins
flowing again, this is the diastolic pressure
major arteries
aorta – carries blood from the left ventricle
to the rest of the body
L+ R coronary arteries – carry blood from
the aorta to the sides of the heart
L+R carotids – carry blood from the aorta
to the sides of the head
L+R subclavians – carry blood from the aorta to arms
major arteries
mesenteric – carries blood from the aorta
to the organs of the digestive system
L+R renal – carry blood from the aorta to
the kidneys
L+R iliac – carry blood from the aorta to the
legs
L+R pulmonary – carry blood from the right
ventricle to the sides of the lungs
major veins
L+R jugular – carry blood from the sides of
the head to the subclavian vein
L+R subclavian – carry blood from the
arms to the anterior vena cava
L+R coronary – carry blood from the sides
of the heart to the vena cava
A+P vena cava – carry blood from the head
and arms (anterior) and lower body
(posterior) to the right atrium of the heart
major veins
L+R iliac – carry blood from the legs to the
posterior vena cava
L+R renal – carry blood from the kidneys to
the posterior vena cava
hepatic – carry blood from the liver to the
posterior vena cava
hepatic portal – carry blood from the small
intestine to the liver
pulmonary – carry blood from the lungs to
the left atrium
Arteries blood flow
- bp is highest in aorta
- ## total cross sectional area of arterioles is greater than arteries, and the BP decreases
Capillaries blood flow
- huge TCA, blood pressure and velocity plummet
- gives time for nutrients to be exchanged
Vein blood flow
- blood returns to TCA, and Bp increases
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