Transcript Circulatory System - Mercer Island School District

Circulatory
( or cArdiovascular)
System
Blood Composition
Plasma (55%): Fluid portion of blood
Red blood cells (44%): Carry oxygen
White blood cells: Defend against pathogens
Platelets: Cell fragments, form blood clots
Red Blood Cells
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Hemoglobin: Iron-containing molecule
Loosely binds O2 in lungs (high concentration)
Releases O2 in body tissue (low concentration)
Shape of RBC’s allows them to travel through
narrow capillaries more easily
Red Blood Cell Lifespan
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Produced in the marrow
Only type of body cell without a nucleus
Old RBC destroyed in liver, spleen
Average lifespan 120 days
Blood Types
RBC Marker Proteins
A- A protein
B- B protein
AB- both A and B proteins
O – neither A nor B proteins
Another marker protein is Rh factor.
Rh +: has Rh factor; Rh - : no Rh factor
Immune system produces antibodies against foreign
antigens (any protein etc. not produced in the body)
AB + is the universal receipient
O – is the universal donor
Blood Vessels
Arteries  Arterioles (thinner arteries) 
Capillaries  Venules (thinner veins)  Veins
Arteries
 Carry blood away from the heart
 Most arteries contain oxygenated blood
 Blood is under greater pressure (most arteries
protected deeper within body)
 Thick walled vessels
 Muscular walls expand/ contract to help move blood
Capillaries: Site of
Gas/Nutrient Exchange
Microscopic blood vessels
 Lining is 1 cell thick
 Allows oxygen and nutrients to diffuse into
body cells
 Waste from cells diffuses into blood
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Veins
Carry blood back to the heart
 Most veins carry deoxygenated blood
 Since many veins travel against gravity,
equipped with one-way valves to prevent
back-ups
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Artery: Thicker layer of
smooth muscle
Vein: One way valves
Heart
Mainly cardiac muscle
 Cells have numerous mitochondria
 Mammalian hearts have 4 chambers
• 2 Upper Chambers: Atria
 Receiving chambers
• 2 Lower Chambers: Ventricles
 Pump blood out of heart
 Left and right sides separated by solid
wall (septum) to create two pumps
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Video on Flow of Blood in the Heart: click once to start video
http://www.youtube.com/watch?v=gn6QmETEm8s
https://www.youtube.com/watch?v=PgI80Ue-AMo
Video:Blood Flow through the Body
Pathway of Blood
Oxygen poor blood returning
from body enters right atrium
Right atrium  right ventricle 
pulmonary artery  lungs 
pulmonary vein  left atrium 
left ventricle aorta  arteries
 capillaries  veins 
vena cavae
Amphibians and reptiles have a 3 chambered heart
rather than four chambered heart, which allows mixing
of oxygenated and deoxygenated blood.
Mammals and birds have a four chambered heart which
keeps oxygenated and deoxygenated blood separated
and allows for more efficient transport of oxygen.
Discuss with your table partner why amphibians (such as
frogs) and reptiles (such as crocodiles) do not require as
efficient a heart as mammals and birds.
Mammals and birds are warm-blooded (endotherms.)
A large expenditure of energy (ATP) is used to keep the
body warm. This ATP is provided by cellular respiration,
which requires both food and oxygen.
Endotherms require a larger amount of both food and
oxygen.
Amphibians and frogs are cold-blooded (ectotherms).
Their body temperature changes with the outside
temperature, and they do not require energy for heating.
Heartbeat regulation
Region of heart called the sinoatrial node acts
as pacemaker, regulating the heart rate through
electrical impulses that spread through the
heart.
Medulla oblongata regulates the pacemaker,
speeding or slowing the heart rate as
necessary.
Systolic and Diastolic Pressure
Systolic pressure is the pressure exerted
when the heart beats.
Diastolic pressure is the lowest pressure,
when your heart relaxes between beats.