review of the normal physiology of the heart and the cardio vascular system

7/24/2019 Review of the Normal Physiology of the Heart and the Cardio Vascular System

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1. REVIEW OF THE NORMAL PHYSIOLOGY OF THE HEART AND THE CARDIO

VASCULAR SYSTEM ANATOMIC FEATURES OF THE SYSTEM

BLOOD TRANSPORT

CARDIAC OUTPUT

PRELOAD

AFTERLOAD

ANATOMIC FEATURES OF THE SYSTEM

**Blood vessel !"es

Blood Vessels: Arteries, Capillaries & More

In this lesson, you will take a trip around the circulatory system and encounter the various blood

vessels, including arteries, veins, and capillaries. Come along as we follow the path to every cell of

your body.

Blood Vessels

Blood flows through blood vessels, which form the closed system called the circulatory system. Like

a system of roads, the circulatory system has its highways, back roads, and alleyways, which we call

arteries, veins, and capillaries. In this lesson, we will learn about blood vessels and how they

transport blood throughout the body.

Arteries and Arterioles

Each time your heart beats, blood is forced into large arteries.Arteriesare blood vessels that carry

blood away from the heart to other tissues. An easy way to jog your memory when thinking about

arteries is to remember thatarteries carry bloodaway from the heart. Because arteries are the first

vessels that the heart pumps blood through, they experience the highest blood pressure, so they
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have thick elastic walls to withstand the high pressures. These large arteries expand when the

pressure of the blood rises and then recoil when the heart relaxes between beats to provide a

smooth flow of blood through your body.

From the large arteries, blood starts its one-way journey around the body, moving into smaller and

smaller arteries and then intoarterioles. Small arteries, such as arterioles, are less elastic and havemore smooth muscle than the larger arteries. These smaller, muscular arteries do not expand as

much when blood enters them and therefore provide the greatest resistance to blood flow through

the arterial system, which helps regulate your blood pressure.

The miles of arteries and arterioles in your body are simply transportation vessels and can be

thought of as the highways and back roads of your circulatory system.

Capillaries

Only the microscopiccapillariesserve as the location for the exchange of gases and nutrients

between blood and tissue cells. The capillary walls are very thin and composed of a single layer

ofendothelial cells,which are very thin flattened cells that line the inner walls of all of the blood

vessels. Capillaries are the alleyways that extend and branch into every tissue of your body, ensuring

that every cell has a blood supply. It is here, in the capillary beds, that your cells pick up oxygen and

nutrients and drop off carbon dioxide and wastes.

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Ve#(s &(d Ve(les

The blood is now ready for its return trip to the heart through more transportation vessels. After

leaving the capillary beds, blood starts its trip back to the heart by first enteringvenules, which are

groups of capillaries that unite to become small vessels that drain the capillary beds. These small

vessels in turn empty into larger vessels calledveins.Veins are blood vessels that carry blood
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toward the heart from various tissues. Veins are far from the initial pressure of the heartbeat and

therefore under low pressure. Their walls are thinner than those of the corresponding arteries, and

their inner diameter tends to be larger.

Because blood pressure is usually too low to force the blood back to the heart, veins require a little

help. This help comes from one-way valves inside veins that prevent backflow. These valves mightnot seem too important, but if they were not there, your blood would not be able to counter the

effects of gravity and would pool up in your legs every time you stood up. This would drop your blood

pressure to dangerously low levels.


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ANATOMY OF THE HEART


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How Blood Flows Through the Heart


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review of the normal physiology of the heart and the cardio vascular system

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