Transcript Chapter 12: The Circulatory System

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Anatomy Bowl prep study guide by Kush Bhorania
*Overview:
Understand…
1) Basic components of the circulatory system.
2) Understand what it means to have a closed
circuit of blood vessels.
3) Understand anatomy of heart, blood supply
to the heart muscle, cardiac cycle,
conducting system of heart, structure &
function of blood vessels.
4) Understand circulation, blood pressure, and
pulse.
Anatomy of Heart
* Left atrium  lies anterior to esophagus.
* Right atrium and right ventricle make up most of the
anterior view in anatomical position.
* Apex  formed by the left ventricle.
* Covering sac is called pericardium and is fibrous.
* Three major walls:
a) myocardium – thick cardiac muscle.
b) endocardium – inner lining that is very smooth. For
example, it lines the muscles that close the mitral valve.
c) epicardium- layer making up the heart itself.
Questions to think about:
1) What are the implications of having a fibrous sac around
the heart?
2) Why is it important for endocardium to be a smooth
layer? What would happen if it was not smooth layer?
Understand the role of the
valves during cardiac cycle
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Blood is brought into the right atrium from superior vena cava and inferior vena cava.
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Oxygenated blood is returned to the heart (left atrium, specifically) via the pulmonary
veins.
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Blood is then directed into the left ventricle by mitral valve . The left ventricle contracts
and pushes blood through aortic valve into the aorta.
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Things to consider
The blood is then directed into the right ventricle by tricuspid valve.
Blood is then pumped into pulmonary trunk from which deoxygenated blood is carried to
the right and left lungs via pulmonary artery.
What is the significance of superior and inferior vena cava.
Why is the blood directed as opposed to simply flowing through the valves of heart?
Why is the aorta so massive?
What would happen to left ventricle if mitral valve stopped working?
Systole vs Diastole ?
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Ventricular systole refers to contraction of ventricle, closure of
Atrioventricular valves, and opening of aortic and pulmonic valves.
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Ventricular diastole refers to contraction of atrium, but ventricular
relaxation, and opening of Atrioventricular valves but closure of aortic and
pulmonic valves.
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Something to consider:
Blood pressure against aorta is highest in this artery during which cycle
systole or diastole? Why?
Blood fills right and left coronary arteries during diastole. Can you see why?
Conducting System of Heart
*Understand that the SA node initiates the
contraction of the heart and that the nervous
system only regulates this contraction.
*SA node  AV node  AV bundle (bundle of His)
 Purkinje fibers.
*SA node is located near superior vena cava.
*AV node is located near opening of coronary
sinus.
*Understand that there is a delay in signal
through the initial part of conduction system so
that proper flow of blood is maintained.
Structure of arteries, veins, and capillaries
* Tunica adventitia is outermost layer.
* Tunica media of arteries and veins is different in
thickness. Understand why.
* Why are the capillaries only one layer? So that
maximum gas exchange is allowed.
* Things to consider:
1) Pressure gradient in arteries vs veins vs
capillaries.
2) Where is blood volume the greatest? Why?
3) Which have valves?
Circulation overview:
*Pulmonary circulation
*Systemic circulation
*Hepatic circulation
*Fetal circulation
Pulmonary circulation
* Blood enters superior and inferior vena cava which is then
received by right atrium.
* The opening of inferior vena cava into right atrium has a valve but
the opening of superior vena cava does NOT have a valve. This is
because the inferior vena cava must work against gravity whereas
the blood in superior vena cava is moved by the help of gravity.
* Blood from right atrium is DIRECTED into right ventricle by opening
of tricuspid or right atrioventricular valve. The pulmonic valve is
closed at this time.
* Blood from right ventricle is then DIRECTED into pulmonary trunk
via pulmonic valve that is open. At the same time, the tricuspid
valve is closed. The closing of this valve is directed by muscles in
right ventricle (called papillary muscles).
* Blood from pulmonary trunk moves through pulmonary arteries to
lungs. Note that the blood in pulmonary artery is deoxygenated.
The oxygenated blood is picked up by pulmonary veins and
returned to left atrium.
Systemic Circulation
* (from previous slide)…blood in left atrium is oxygenated.
This
blood is directed into left ventricle by mitral or bicuspid valve.
During this stage the aortic valve is closed and right ventricle
is filling with blood (diastole).
* Blood from the left ventricle is then directed into aorta by
aortic valve (open during ventricular systole). The mitral valve
is close at this time so that left atrium may collect blood from
pulmonary veins.
* The aorta has three parts: Ascending part, Arch, and
Descending part.
* The ascending part delivers blood to the heart itself via the
coronary arteries.
* The arch of aorta delivers blood to head, neck, and upper
extremity.
* The descending part delivers blood to everything below the
level of heart.
Consider: How would the pressure in systemic circulation differ
from pressure in pulmonary circulation? Is there any difference?
Hepatic Portal
Circulation
* The veins carrying the blood from spleen, stomach, pancreas,
gallbladder, and intestines do NOT pour directly into inferior vena
cava. The blood first goes through the liver in order to maintain blood
glucose level and to detoxify poisonous substances that may be
present in blood.
Fetal Circulation
*Lungs in fetus are NOT functional until the baby
takes its first breath outside the uterus.
*The primary source of nutrients to the fetus is
from the placenta. However, there is NO mixing
of blood between the fetus and mother. There is
gas exchange via capillaries.
*Be sure to understand the role of shunts: ductus
venosus, foramen ovale, and ductus arteriosus.