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Lecture 27

Physiology 3120 Lecture Notes - Lecture 27: Pulmonary Vein, Inferior Vena Cava, Superior Vena Cava

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Tom Stavraky

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Lecture 27 Cardiovascular System
- Heart beats 3.5 billion times in an average (70 year) life
- It begins on the 23rd day of fetal development
- At rest it pumps 5-6 L of blood/min
- During exercise it can reach 20-40 L/min
- Average heart rate at rest is roughly 70 bpm
- Max heart rate = 220 age
- 160,000 km of blood vessels
Functions of the CV system
Role as a transport system
- Maintains homeostasis - maintenance of relatively constant conditions in the internal
- Transports oxygen and nutrients to the tissues (tissues need oxygen to make ATP)
- Transports carbon dioxide and waste products from the tissues to the external environment
(by product of making ATP is carbon dioxide)
- Regulates body temperature (by transporting excess heat out of the body or conserving
o Done by the blood vessels diverting blood away from skin and to the core of the
body when one is cold
o Sends heat to the skin so body can sweat when it is hot
- Transports and distributes hormones and other substances within the body
Components of the transport system include
a) Central pump the heart
b) Closed system of blood vessels
- 2 circulatory systems in our body separated by the heart
c) The fluid medium, blood, through which various substances are transported
General organization
Two circulatory systems:
1. Pulmonary circulation
- Blood going TO the lungs to pick up oxygen and drop off carbon dioxide from the blood
- Do not get rid of all the carbon dioxide in the lungs we still keep some
- Blood returns to the heart
- Exchange of gases between the atmosphere and the blood
2. Systemic circulation
- Sends blood to the rest of the body (other than the lungs)
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Blood flow
- Blood returns to the right atrium of the heart
- When the heart contracts, both atria contract at the same time and blood from the right
atrium is pumped to the right ventricle
- When the heart contracts, both ventricles contract at the same time and the blood from the
right ventricle is pumped to the pulmonary artery
- ARTERY: blood AWAY from the heart
- VEINS: return blood BACK to the heart
- Common misconception: arteries contain blood that is high in oxygen and low in carbon
dioxide this is not the case
- Pulmonary artery contains blood that is high in carbon dioxide and low in oxygen
- PULMONARY ARTERY: beginning of the pulmonary circulation
- Pulmonary artery divides into smaller and smaller arterioles which divide into smaller
pulmonary capillaries (which is where gas exchange takes place)
- Capillaries: gas exchange vessels
o In the lungs, they drop of some carbon dioxide and pick up oxygen
o = have blood high in oxygen and low in carbon dioxide
- Exchange of gas in the lungs is extremely efficient blood that leaves the lungs is almost
95% saturated with oxygen
o Even during maximal exercise, blood is still saturated with oxygen
- Capillaries venules veins pulmonary vein
- Blooding coming back to the heart returns through the pulmonary vein to the left atrium
- When the left atrium contracts, blood is pumped to the left ventricle, the ventricles contract
and blood is pumped out to the aorta
- AORTA: beginning of the systemic circulation
o Divides into arteries arterioles capillaries in tissues bed
- Opposite occurs at these capillaries: oxygen is dropped off and carbon dioxide is picked up
- After leaving capillaries, veins reunite into venules and venules reunite into veins which
return to the right atrium through superior and inferior vena cava
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- Blood is always red
o Oxygenated blood is brighter red and deoxygenated blood is darker red
o Misconception: veins stand out as being blue (it is not actually blue, it is red)
It is because of light and how it is absorbed by the skin and reflected back by
the veins
- Right Atrium Right ventricle Pulmonary artery Pulmonary Capillaries
- Picks up O2 as it passes through the lungs and drops off some CO2
- Pulmonary Vein Left Atrium Left Ventricle Aorta Arteries Arterioles
- The capillaries are exchange vessels where O2 and nutrients diffuse into the tissues and CO2
and waste products are picked up.
- Capillaries Venules Veins Right Atrium
Series and parallel circuits
- Vascular (capillary) beds are arranged in parallel and/or in series
o Parallel: arranged side by side, e.g. capillary beds in the arms and head/brain are
arranged in parallel to each other
o Series: one after another e.g. in the kidney glomerular capillaries are in series with
the peritibular capillaries, digestive tract is joined by the hepatic vein in the liver
which has capillary beds that are also in series
- There are not many places with capillary beds in series most are in parallel
- GC Glomerular capillaries
- PTC Peritubular capillaries
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