fizikal- jantung

8/9/2019 fizikal- jantung

1/6

1.1 MAMMALIAN CIRCULATION

1) Contraction of the right ventricle pumps bloods to the lungs via 2) the pulmonary

arteries. As the blood flows through 3) capillary beds in the left and right lungs. It

loads O2 and uploads CO2. Oxygens rich bloods return from the lungs via the

pulmonary veins to 4) the left atrium of the heart. Next, the oxygen rich blood flows

into 5) the left ventricle, which pumps the oxygen rich blood out to body tissues

through the systematic circuit. Blood leaves the left ventricle via 6) the aorta, which

conveys blood to arteries leading throughout the body. The first branches from the

aorta are the coronary arteries, which supply blood to the heart muscle itself. The

branches lead to 7) capillary beds in the heads and arms ( forelimbs ). The aorta then

descends into the abdomen, supplying oxygen rich blood to arteries leading to 8)

capillary beds in the abdominal organs and legs ( hind limbs ). Within the capillaries,

there is a net diffusion of O2 from the blood to the tissues and of CO2 produced by

cellular respiration into the blood. Capillaries rejoin, forming venules, which convey

blood to veins. Oxygens poor blood from the head, neck, and forelimbs is

channelled into a large vein, 9) the superior vena cava. Another large vein, 10) the

inferior vena cava, drinks blood from the trunk and hind limbs. The two cavae empty

their blood into 11) the right atrium, from which the oxygens poor blood flows into

the right ventricle.


2/6

1.1.1 The mammalian cardiovascular systems : an overview.


3/6

1.3 BLOOD PRESSURE AND GRAVITY

Blood pressure is generally measured for an artery in the arm at the same height as the

heart. For a healthy 20 years old human at rest, arterial blood pressure in the systematic

circuit is typically about 120 millimetres of mercury (mm Hg) at systole and 70mm Hg at

diastole, a combination designated 120/70 ( Arterial blood pressure in the pulmonary circuit

is six to ten times lower).

Gravity has a significant effect on blood pressure. When you are standing, for

example your head roughly 0.35 m higher than your chest, and the arterial blood pressure in

your brain is about 27 mm Hg less than that near your heart. If the blood pressure in your

brain is too low to provide adequate blood flow, you will likely faint.

Systolic pressure is pressure in your blood vessels is at its peak when your heart

contracts to squeeze blood into the arteries. This systolic pressure, measured when the

doctor or nurse first hears the sound of your heartbeat, reflects the work of your heart and

can vary a lot depending on what you are doing. In a healthy person, the systolic pressure is

normally between 120 and 140 millimetres of mercury, written as 120 or 140 mmHg.

The pressure in your blood vessels is at its lowest when your heart relaxes and fills

with blood called as Diastolic pressure. This is known as the diastolic blood pressure, which

the doctor or nurse records at the last sound of your heart beating. In a healthy person, the

diastolic pressure is around 80mmHg.

Normally, when the systolic pressure is raised, the diastolic pressure is too, and vice

versa. It used to be believed that raised diastolic pressure was more important than raised

systolic pressure, because it is a sign that the medium-sized or small arteries have become

stiff and narrowed. Research has now shown, however, that if you are over 40 a raised

systolic pressure, which indicates how hard your heart has to work, is also significant

especially in predicting whether you will develop heart disease.

Gravity is also consideration for blood flow in vein, especially those in the legs.

Although blood pressure in veins is relatively low, several mechanisms assist the return of

venous blood to the heart. First, rhythmic contractions of smooth muscles in the walls and

veins aid in the movement of the blood. Second, the more important, the skeletal muscles

during exercise squeeze blood through the veins toward heart ( figure 1.3.1 ). This is why
http://www.peacemotivate.com/2006/05/19/understanding-heart-disease/http://www.peacemotivate.com/2006/05/19/understanding-heart-disease/


4/6

periodically walking up and down the aisle during a long airplane flight helps prevents

potentially dangerous. Third, the change in pressure within the thoracic ( chest ) cavity

during inhalation causes the vanae cavae and other large veins near the heart to expand

and fill with blood.

1.3.1 An example of blood measurement reading.

1.3.2 Blood flow in vein.


5/6

1.3.1 HOW BLOOD PRESSURE IS MAINTAINED

The maintenance of blood pressure within the arteries is a complex physiological process

that basically depends on three factors which, under nervous control, keep the pressure

relatively constant.

First, the beating of the heart is continually pumping blood into the aorta. The blood

flows along the large arteries and into the smaller vessels, where it replaces the blood

escaping through the capillaries into the veins. In this way the volume of blood in the arterial

system is maintained.

Secondly, the walls of the arteries contain muscle and elastic fibres. Each time that

the heart beats and discharges blood into the arterial system, these fibres stretch to

accommodate the influx of blood. When the heart relaxes, on the other hand, the fibres in

the walls of the vessels contract, and by so doing they not only reduce the capacity of the

circulatory system but also maintain the pressure.

Thirdly, and lastly, the minute arterial vessels, the arterioles, which lead from the

smallest arteries to the capillaries, have muscular walls. Contraction of these muscles

reduces the blood flow through the capillaries, and so controls the rate at which it escapes

from the arterial system, through the capillaries, and into the veins.
http://www.daviddarling.info/encyclopedia/A/artery.htmlhttp://www.daviddarling.info/encyclopedia/A/aorta.htmlhttp://www.daviddarling.info/encyclopedia/V/vein.htmlhttp://www.daviddarling.info/encyclopedia/A/artery.htmlhttp://www.daviddarling.info/encyclopedia/A/aorta.htmlhttp://www.daviddarling.info/encyclopedia/V/vein.html


6/6

References

Neil, A. C. & Jane, B. R. (2008). Biology with Mastering Biology. International

Version. Sansome Street: San Franscisco.

fizikal- jantung

Documents