1 lesson 2 zblood vessels zcardiac cycle zheart sounds
TRANSCRIPT
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Lesson 2
Blood vesselsCardiac cycleHeart Sounds
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Blood vessels
There are three types of blood vessels:ArteriesCapillariesVeins
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Blood vessels
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Arteries
Carry blood away from the heartThick muscular wall to withstand
high pressure of bloodNarrow lumenMost collagen (tough fibrous
protein)- tough and durableElastic fibres and smooth muscle-
allows stretch & recoil
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Arteries… cont
No valvesBranch into smaller and smaller
vessels- arteriolesContraction of smooth muscle of
arterioles allows blood to be diverted to different parts of the body
e.g. fight or flight more blood to skeletal muscles and less to digestive system
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Arteries… cont
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Capillaries
Tiny vessels- 1 cell thick wall 10m in diameter
Exchange of nutrients and waste with tissues occurs here
Extensive branching network (capillary bed) throughout body tissues
Only certain capillary beds open at one time to allow shunting of blood from one area to another
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Capillaries… cont
Most numerous type of blood vessel in the body
Permeable wallsCarry blood at low pressure and low flow
rate Reduces fluid loss through permeable
capillary walls Allows sufficient time for exchange of
materials
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Veins
Carry blood back to the heartThin muscular wall as blood at low
pressureWide lumen- reduces resistance to
blood flowLess collagen, elastic fibres and
smooth muscle
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Veins… cont
Have valvesBlood at low pressure- return blood
against gravity- so lie close to muscles- when muscle contract they squeeze the veins to temporarily increase the blood pressure
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Veins… cont
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Describe three things that this graph shows.
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Major Blood VesselsNB heart muscle itself
is supplied with blood by coronary arteries
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Cardiac Cycle
A pattern of contraction (systole) and relaxation (diastole) by heart in 1 heart beat
Lasts about 0.8 seconds (based on heart rate of 75bpm)
Chambers alternately contract and relaxBlood always flows towards low pressure
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Cardiac Cycle…cont
3 phases to the cycle:1. Atrial systole2. Ventricular systole3. Diastole
Decrease in volume
Increase in pressure
Blood forcedout
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Atrial systole
Blood flows into LA and RA under low pressure
LA & RA contract simultaneously AV (bicuspid & tricuspid) valves
open Blood forced into LV & RV At this point LV & RV in diastole & SL
valves closed
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Ventricular systole
0.1 secs later AV (bicuspid & tricuspid) valves
close Blood forced into LV & RV which
contract & push blood through open SL
valves to arteries High pressure in ventricles
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Diastole
Atria & ventricles relax Elastic recoil of relaxing heart walls
lowers pressure in atria & ventricles Blood under high pressure in
arteries drawn back into heart from veins
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Heart Sounds
Lub dub Lub- closing of AV valves Dub- closing of SL valves
Human heart sounds
Feline heart sounds