Download The circulatory system The cardiovascular system consists of two

The circulatory system
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The circulatory system
The cardiovascular system consists of two circuits of blood circulation, both originating
and ending in the heart.
 Pulmonary circulation: (Right side of the heart)
o The movement of blood from the heart, to the lungs, and back to the heart
again.
 Systemic: (Left side of the heart)
o The movement of blood from the heart, throughout the body, and back to
the heart again.
Systemic circuit:
1. The oxygen-rich blood passes from the left atrium through a one-way valve into
the left ventricle.
2. The forceful contraction of the heart's left ventricle forces the blood into the aorta
which then branches into many smaller arteries which run throughout the body.
3. The inside layer of an artery is very smooth, allowing the blood to flow quickly.
4. The outside layer of an artery is very strong, allowing the blood to flow forcefully.
5. The oxygen-rich blood enters the capillaries where the oxygen and nutrients are
released.
6. The waste products are collected and the waste-rich blood flows into the veins in
order to circulate back to the heart where pulmonary circulation will allow the
exchange of gases in the lungs.
7. The veins bring waste-rich blood back to the heart, entering the right atrium
throughout two large veins called vena cavae.
End of systemic circuit.
Start of pulmonary circuit
The circulatory system
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8. The right atrium fills with the waste-rich blood and then contracts, pushing the
blood through a one-way valve into the right ventricle.
9. The right ventricle fills and then contracts, pushing the blood into the pulmonary
artery which leads to the lungs.
10.
In the lung capillaries, the exchange of carbon dioxide and oxygen takes
place.
11.
The fresh, oxygen-rich blood enters the pulmonary veins and then returns to
the heart, re-entering through the left atrium.
Regulation of Circulation:
1. As blood seeps through the consumer organ (muscle) via capillaries, the pressure
differential from the arterial side to the venous side maintains the transport of
blood through the capillary bed.
2. Here the exchange of O2, nutrients, and metabolic by products between the
working tissue and blood take place.
3. If the lack of O2 or the accumulation of metabolites require high blood flow,
smooth muscles that encircle the fine blood vessels remain relaxed, allowing the
pathways to remain open. [allowing more blood to flow].
4. The large cross-sectional opening reduces blood flow velocity and blood pressure,
allowing nutrients and O2 to enter extracelluar space of the tissue and permitting
the blood to accept metabolic by-products from the tissue.
5. Constriction of the capillary bed by tightening the encircling smooth muscle
reduces the local blood flow so that other organs in more need of blood may be
better supplied.
6. Signals from the Central Nervous System (CNS) can trigger the constriction of
other les important vessels supplying the blood to organs
7. This leads to quick redistribution of the blood supply, which favors skeletal
muscles over the digestive system principle (muscle over digestion)
The circulatory system
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8. Even in heavy exercise, the systemic blood flow is so controlled that the arterial
blood pressure is sufficient for an adequate blood supply to the brain, heart, and
other vital organs.
9. To accomplish this, neural vascoconstrictive commands can override local dilatory
control
10.
For example: the temperature--regulating center in the hypthalmus can
affect vasodilation in the skin if this is needed to maintain a suitable body
temperature. even if it means a reduction of blood flow to the working muscles
(skin over muscles)
11.
Such compression of the capillary bed can also occur if the striated muscle
itself contracts strongly, at more than about 20% of its maximal capacity.
12.
If this contraction is maintained, the muscle hinders or shuts off its own
blood supply, and cannot continue the contraction.
13.
Thus, sustained strong static contraction is self-limiting.
14.
A typical example:
a. Overhead work, wherein muscles must keep the arms elevated. After a fairly
short time one must let them hang down to allow muscle relaxation and
renewed blood flow.