Pregnancy physiology I | Reproductive system physiology | NCLEX-RN | Khan Academy

Summary

This script delves into the remarkable physiological changes the body undergoes during pregnancy, emphasizing the cardiovascular, respiratory, and renal systems. It highlights how blood volume surges by 40-50% to nourish the fetus, despite blood pressure dropping due to progesterone's vasodilatory effects and the placental circuit. The heart's workload increases, with a faster beat and higher stroke volume. Respiratory adjustments include increased oxygen consumption and minute ventilation, managed by progesterone's influence on brain centers, leading to a slightly alkalotic blood pH. The kidneys experience heightened filtration rates due to increased blood flow, and the urinary system faces challenges like frequency and susceptibility to infections due to ureter dilation and pressure from the growing uterus.

Takeaways

• 🤰 Pregnancy is a complex process that involves significant changes across every organ system to support the growth and development of the fetus.
• 🩸 The cardiovascular system experiences a 40-50% increase in blood volume to meet the oxygen and nutrient demands of the fetus.
• 💓 The heart works harder during pregnancy, beating faster and increasing its stroke volume to pump more blood per minute.
• 📉 Despite the increased cardiac output, blood pressure tends to decrease due to the vasodilatory effects of progesterone and the low-resistance placental circuit.
• 🚫 Progesterone's relaxation of smooth muscle causes blood vessels to dilate, contributing to the drop in blood pressure.
• 🤷‍♀️ Supine Postural Hypotensive Syndrome occurs when the enlarged uterus compresses the inferior vena cava, leading to decreased blood return to the heart and low blood pressure.
• 👶 The respiratory system adapts to pregnancy by increasing oxygen consumption and minute ventilation to meet the needs of the mother and fetus.
• 🌬️ Progesterone influences the central respiratory centers to increase the volume of air inhaled with each breath, without the mother needing to take deeper breaths intentionally.
• 🔄 The kidneys experience increased blood flow and filtration rate due to the overall increase in blood volume and vasodilation during pregnancy.
• 💧 Pregnant women urinate more frequently due to increased urine production and pressure from the enlarging uterus on the bladder.
• 🚨 The pressure from the uterus on the ureters can lead to dilatation and urinary stasis, increasing the risk of kidney infections like pyelonephritis.

Q & A

How does the body demonstrate teamwork during pregnancy?

During pregnancy, the body demonstrates teamwork by having every organ system undergo significant changes to support the growth and development of the fetus while ensuring the mother's body meets its own needs.

What is the primary reason for the increase in blood volume during pregnancy?

The primary reason for the increase in blood volume during pregnancy is to carry more oxygen and nutrients to the fetus, which increases by about 40 to 50 percent.

How does the heart adapt to the demands of pregnancy?

The heart adapts by beating more quickly, increasing the stroke volume, and thus the cardiac output, to supply more blood to meet the demands of the fetus.

Why does blood pressure decrease during pregnancy despite the increased cardiac output?

Blood pressure decreases due to the relaxing effect of progesterone on smooth muscle, including blood vessels, causing dilation and lowered blood pressure. Additionally, the placenta acts as a low-resistance circuit, contributing to the decrease.

What is Supine Postural Hypotensive Syndrome and how is it related to pregnancy?

Supine Postural Hypotensive Syndrome occurs when the enlarged uterus compresses the inferior vena cava in the supine position, leading to decreased blood return to the heart and causing low blood pressure and lightheadedness.

How does oxygen consumption change during pregnancy?

Oxygen consumption increases during pregnancy due to the fetus's needs and the mother's body changes, leading to an increase in minute ventilation to bring in more oxygen.

What role does progesterone play in respiratory changes during pregnancy?

Progesterone acts on the central respiratory centers in the brain to increase minute ventilation, causing pregnant women to take in more air with each breath.

How does the body maintain blood pH balance when carbon dioxide levels decrease due to increased ventilation?

The body maintains blood pH balance by increasing the secretion of bicarbonate, a base, from the kidneys to counteract the decrease in carbon dioxide, an acid.

What anatomical changes occur in the respiratory system during pregnancy?

The enlarging uterus pushes the diaphragm upwards, but the chest wall becomes more mobile and flexible, and the chest wall circumference increases to compensate for the upward shift of the diaphragm.

How does pregnancy affect the kidneys and the urinary system?

Pregnancy increases blood flow to the kidneys, leading to an increased rate of filtration. Pregnant women also urinate more frequently due to increased urine production and pressure from the uterus on the bladder. The ureters may dilate, which can lead to urinary stasis and a higher risk of kidney infections.