Question

A full-term fetus typically has a mass of 3.50 kg.

(a) What pressure does the weight of such a fetus create if it rests on the mother’s bladder, supported on an area of 90.0 cm^2?
(b) Convert this pressure to millimeters of mercury and determine if it alone is great enough to trigger the micturition reflex (it will add to any pressure already existing in the bladder).

Answer 1

The weight of the fetus on the mother's bladder creates a pressure of 3.82 × 10^5 Pa, which can be converted to 2866.69 mm Hg. The pressure alone may be great enough to trigger the micturition reflex, depending on the specific threshold of the reflex. It can also add to any existing pressure in the bladder.

Step-by-step explanation:

To calculate the pressure created by the weight of the fetus on the mother's bladder, we can use the formula:

Pressure = Weight/Area

Given that the mass of the fetus is 3.50 kg and the area supporting it is 90.0 cm², we can calculate the pressure as follows:

Pressure = (3.50 kg)(9.8 m/s²) / (0.0090 m²) = 3.82 × 10^5 Pa

To convert this pressure to millimeters of mercury (mm Hg), we can use the conversion factor:

1 mm Hg = 133.32 Pa

Therefore, the pressure in millimeters of mercury is:

3.82 × 10^5 Pa * (1 mm Hg / 133.32 Pa) = 2866.69 mm Hg

Whether this pressure alone is great enough to trigger the micturition reflex depends on the specific threshold of the reflex, which varies for individuals. However, the pressure created by the weight of the fetus is significant and can contribute to triggering the reflex when combined with any existing pressure in the bladder.