Animal Anatomy & Physiology

Functions of the Cardiovascular System:
 delivers vital nutrients (e.g., oxygen) to all body cells
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 eliminates waste products and carbon dioxide transports chemical messengers (e.g., hormones) from one part of the body to another helps to maintain a constant body temperature

Open Circulatory System – Hemolymph (mix of blood and tissue fluid) is pumped directly into the body cavity.
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Closed Circulatory System – Blood is separate from the rest of the body in a network of tubes.

Single-circuit circulatory system – Only one track the blood can travel
Two-circuit circulatory system - Circulation to the lungs is separated from circulation to the rest of the body.

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The Heart : a muscular organ that continuously pumps blood through the body, generating blood flow.
The Blood Vessels : a system of hollow tubes through which the blood moves.
The Blood : The fluid that transports nutrients, O and many other materials throughout the body.
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Circulation to the lungs is separated from circulation to the rest of the body.
 pulmonary circuit : the part of the circulatory system that
 delivers blood to the lungs systemic circuit : the part of the circulatory system that delivers blood around the body

 Has four chambers
 Atria: the two top chambers that fill with blood returning from the body or the lungs
(singular atrium).
 Ventricles: two bottom chambers that receive blood from the atria and pump it out to the body or the lungs.

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The tricuspid valve separates the right atrium from the right ventricle
The mitral (bicuspid) valve separates the left atrium from the left ventricle
The pulmonary (semilunar) valve separates the right ventricle from the pulmonary artery
The aortic (semi-lunar) valve separates the left ventricle from the aorta

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The vena cavae bring oxygen-poor blood from the body to the right atrium .
The oxygen-poor blood flows from the right atrium into the right ventricle .
The right ventricle pumps the oxygen-poor blood to the lungs through the pulmonary arteries .

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The pulmonary veins bring oxygen-rich blood from the lungs back to the heart through the left atrium .
Oxygen-rich blood flows from the left atrium to the left ventricle.
The left ventricle pumps the oxygen-rich blood to the body through the aorta .

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Valves prevent the blood from flowing backwards.
The “ LUB ” sound is caused by the closing of the atrioventricular (AV) valves
(tricuspid & mitral valves) as blood is pumped from the atria to the ventricles.
The “ DUB ” sound is caused by semilunar valves (pulmonary & aortic), as blood is pumped from the ventricles into the arteries

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A bundle of specialized muscle tissue, called the sinoatrial (SA) node , stimulates the muscle cells to contract and relax rhythmically .
Also referred to as the pacemaker , because it sets the pace for cardiac activity
Located in the wall of the right atrium .

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The SA node generates an electrical signal that spreads over the two atria and makes them contract simultaneously.
As the atria contract, the signal reaches another node, called the atrioventricular
(AV) node .

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The AV node transmits the electrical signal through a bundle of specialized fibers, called
Purkinje fibres , that run down the septum and up around the ventricles
This initiates the almost simultaneous contraction of all cells of the right and left ventricles .

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Force of the blood on the walls of the arteries.
Normal BP 120/80 mm Hg; decreases as you move away from the heart.
 Systole (120 mmHg): Pressure of contraction
 Diastole (80 mmHg): Pressure at relaxation (re-filling of heart)
Stroke Volume : volume of blood leaving heart (L)
Heart Rate : number of beats
(contractions) per minute
(bpm)

Two factors determine BP:
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Cardiac Output (CO) : amount of blood pumped from the heart each minute = Heart
Rate (HR) x Stroke Volume
(SV)
 ⇡ CO = ⇡ BP
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 increase CO by ⇡ HR or ⇡
Stroke Volume (stronger heart)
Arteriolar resistance : diameter of the arteriole determines the amount of blood flow
 ⇡ diameter = ⇣ BP

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Diameter of blood vessels regulated by the medulla oblongata .
Vasoconstriction : nerve impulses cause muscle to contract, reducing diameter of vessel, reduces flow to tissue, increases pressure
Vasodilation : nerve impulses cause muscles to relax, increasing diameter of vessel, increases flow to tissue, decreases pressure