Human Anatomy and Physiology : Defining Anatomical Orientations

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

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Example Question #31 : Defining Anatomical Orientations

If an individual has a blood pH of 6.8, then they should __________.

Possible Answers:

breathe faster to intake excess O2

breathe faster to remove excess CO2

eat more acidic foods

breathe slower to minimize loss of CO2

breathe slower to maximize use of O2

Correct answer:

breathe faster to remove excess CO2

Explanation:

Normal blood pH is about 7.4 in most tissues (it is a bit lower in veins since they carry waste products, which are acidic). To get back to the physiological set point of pH = 7.4, we want to remove the acid from the blood. The major blood buffer system is shown in the following equation: 

As we know, carbon dioxide is one of the major byproducts of respiration, and is considered waste for our bodies. Combined with water and catalyzed by carbonic anhydrase, it is converted into carbonic acid. Carbonic acid is a weak acid and will partially dissociate into hydrogen ions and bicarbonate ions. Thus, overall, carbon dioxide and water yields acid (hydrogen ions). As a result, excess carbon dioxide in the blood will lower the pH.

In order to increase the pH, we must stop this equation from proceeding in the forward direction; thus, (remember Le Chatelier's principle) we must remove carbon dioxide from the left side. This will push the reaction in the reverse direction, quenching hydrogen ions (acid) and removing them from the blood, increasing blood pH back to normal.

Since we want to get rid of excess carbon dioxide, we breathe faster. Oxygen does not have any effect on blood pH. Furthermore, the atmospheric oxygen level (21%) is plenty for our bodies to utilize, as when we exhale there is about 15% oxygen left over, meaning we only use about 25% of the oxygen we breathe (this is why CPR works!).

Example Question #32 : Defining Anatomical Orientations

In anatomical position, palms are oriented in which direction?

Possible Answers:

facing up

facing down

pressed together

pointed to the left

Correct answer:

facing up

Explanation:

In anatomical position, the thumbs are pointed away from the body. In order to have this orientation, the palms must be facing up. 

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