ASVAB Test Blog

Feb 1st, 2021

ASVAB Biology | Heart, Blood, and Circulation!

asvab biology cardiovascular

Heart, Blood, and Circulation!

Biology is an important part of the ASVAB general science exam. The heart, blood, and circulation are just one small part of that subtest.

Biology is the study of the natural sciences. It seeks to understand living organisms – whether they be trees or humans or fungi; establishing the structure and function of how the biological world works.

For the ASVAB exam, candidates are expected to have a broad and comprehensive understanding of the biological sciences – including ecology, cell biology, and human biology.

Here in this brief study guide, we review one specific topic: heart, blood, and circulation.

Remember – on the CAT ASVAB general science exam, you must answer 15 ASVAB exam questions in 10-minutes and, for the paper ASVAB test, 25 questions in 11-minutes. Given the wealth of knowledge you must learn for biology and every other part of the general science exam, scoring high can become a tall order.

The Heart

The heart is an important organ for the body, with four key functions:

  • To pump oxygenated blood around the body.
  • To pump hormones and other substances around the body.
  • To receive de-oxygenated blood and pump it to the lungs for removal.
  • To maintain blood pressure.

The average heart pumps around 2,000 gallons of blood each day and can continue beating even when disconnected from the body (for a short time).

Each heart has four chambers, two atria (on top) and two ventricles (on bottom).

  • Left atria
  • Right atria
  • Left ventricle
  • Right ventricle

As we have learned, one of the key functions of the heart is to pump oxygenated blood around the body. Oxygen (O2) is essential for cells all throughout the body, assisting their metabolic functions.

When you breathe in oxygen from the air, it enters the lungs and goes through small pockets, known as alveoli, that line the lung. There, blood passes by line a running stream – and oxygen from the lung jumps into this stream to oxygenate the blood. Now, oxygen-rich blood (oxygenated) can return to the heart where it is pumped all throughout the body – feeding cells with the oxygen they need.

Eventually though, these cells run out of oxygen – and waste produce of carbon dioxide (CO2) builds up inside cells (deoxygenated blood). Blood picks up this carbon dioxide and returns to the heart where it is it redirected to the lung once more. Here, the process repeats: carbon dioxide is removed from the blood and exhaled from our lungs, meanwhile blood picks up even more oxygen so the same process can repeat once more.

You may be asked ASVAB test questions on this system, so whilst it may seem complex, let’s break it down a little.

We can see two circuits: systemic and pulmonary. Systemic simply refers to the systemic circulation – the network of blood vessels that traverse the body. The pulmonary system refers to any system that affects the lungs. The process of breathing in/out to absorb oxygen and remove CO2 is known as respiration. For this reason, the pulmonary system is often referred to as the respiratory system.

As we have learned, blood low in oxygen (blue) passed through veins to return to the right-atria, down through the right-ventricle – and up to the lungs. There, the gas exchange takes place: where carbon dioxide is eliminated, and oxygen is restored to blood. Now, the blood returns (red) to the heart through the left atria, down to the left ventricle – and pumped throughout the rest of the body through the aorta and arteries.

Always remember that veins pump blood (deoxygenated) to the heart whereas arteries pump blood (oxygenated) away from the heart. As we can see from the diagram above, it is small structures – called capillaries – where gas exchange takes place.

Constituents of Blood

So far in our study guide of the heart, blood, and circulation – we have discussed the circulatory system and how blood circulates throughout the body and how gas exchange takes place.

Now we need to spend some time learning about the constituents of blood itself.

When we spoke about blood taking in oxygen and removing carbon dioxide, what we are really talking about is red blood cells.

  • Red blood cells – which are more technically known as erythrocytes – are the cells that absorb oxygen and remove carbon dioxide as they slide along the lung. On average, a red blood cell lives for about 120-days before it dies and is broken down by an organ known as the spleen. The spleen takes what is valuable from the red blood cell, such as iron, and discards the rest to be eliminated by the body.
  • White blood cells are also a constituent of blood, which are more technically known as leucocytes. White blood cells help to fight infection.
  • Platelets are tiny cells that play a key role in clot formation. When you suffer a cut and start bleeding, the broken tissue triggers a reaction by the body to throw as many platelets as possible at the wound to clog it and prevent any further loss of blood.

Red blood cells, most white blood cells, and platelets are manufactured inside stem cells found inside bone marrow – the soft tissue found inside bone cavities. ASVAB test questions routinely ask about blood cell types. Make sure you know the functional differences between each of these cells!

Take Home Points

This concludes our review of the heart, blood, and circulation. In this review guide, you have learned:

  • The structure and function of the circulatory system.
  • The purpose and process of gas exchange in the pulmonary system.
  • The structure and four functions of the heart.
  • Cardiovascular structures: arteries, veins, and capillaries.
  • Role of alveoli in gaseous exchange.
  • Function of red blood cells; and the role of the spleen.
  • White blood cells and how they fight infection.
  • The role of platelets in blood clot formation.
  • The function of bone marrow in the production of blood cells.

By knowing these essential facts about the cardiovascular system, you should have confidence of answering any questions on this topic should it appear on your ASVAB exam.

Check back to ASVAB Test Practice soon for even more tips, tricks, and study guides to help you master the 2022 exam and make it through to boot camp!

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