C L9.1 Programming and Reprogramming

Question 1

Pregnancy is the greatest physiological challenge facing women, what are some of the adapations?

Answer 1

• Adaptations required to:
  
  • ↑CO and BV (have another organ - the placenta)
  • Maintain uteroplacental perfusion
  • Maintain fetal demands
• Duration = 40 weeks (from last menstrual period); 38 weeks from fertilisation

Question 2

Metabolic adaptations during pregnancy

Answer 2

• Weight gain
• Altered body shape
• Uterus, breast, BV, maternal stores
  
  • To support and accommodate growing fetus
  • Exponential fetal growth in late gestation
• ↑Metabolic rate, O2 consumption, fat stores
  
  • Breast tissue and uterine muscle are major O2 consumers

Question 3

Glucose

Answer 3

• Maternal hypoglycaemia in late gestation despite insulin resistance by tissue
  
  • Due to b-cell proliferation and hypertrophy (accommodate ↑ insulin)

Question 4

Blood

Answer 4

• Blood loss:
  
  • Vaginal delivery = 500-600
  • Caesarean = 800-1200
• Changes needed to support maternal and fetal circulation and tissues
• ↑BV (30-50%)
  
  • Begins at 6 weeks, peaks at 32 weeks

Question 5

Plasma vol and red cell mass

Answer 5

• Plasma vol
  
  • ↑40-50%
• ↑Red cell mass (25-30%)
  
  • Not as great as plasma or BV
  • Physiological anemia and hemodilution
    
    • RBC increase is slower than plasma vol

Question 6

White blood cells

Answer 6

• ↑25-30%
• ↓platelets due to hemodilution
• ↓total plasma proteins
  
  • ↓albumin

Question 7

Lipids

Answer 7

• ↑40-60%
  
  • ↑cholestorol 40% (essential precrsor for estrogen and progesterone)

Question 8

Coagulation

Answer 8

• ↑BF and coagulaton during pregnancy
• Limit blood loss at delivery

Question 9

Output adaptations

Answer 9

• LV hypertrophy → Increase CO
  
  • ↑SV at 8 weeks
  • ↑HR at 5 weeks
  • ↑Fluid retention/oedema

Question 10

BP

Answer 10

• ↓BP → promote uterine circulation
• ↑renin & ANG II but regractory (no ↑BP)
• May have postural hypertension

Question 11

ECF & kidneys

Answer 11

• ECF = plasama + interstitium
• ECF vol needs to stay constant for homeostatic mech
• Kidneys are the main factors for ECF
  
  • Pregnancy resets vol sensors → altered renal BF, GFR

Question 12

Renal adaptations

Answer 12

• ↑Renal blood flow (↑40-80%)
• GFR (↑30-50%)
  
  • Creatinine clearance used for indication of GFR
• ↑Kidney size ↑by 1cm - ↑RBF & glomerular hypertrophy
• Renal hyperfiltration

Question 13

What does increase RBF and GFR lead to?

Answer 13

• ↑ filtration of water & solutes
• ↑ urine flow and vol
• But tubules retain Na & water to maintain BV and plasma vol

Question 14

Placental adaptations

Answer 14

• Substitutes for fetal organs
  
  • Lungs
  • Kidneys
  • GIT
• Provides fetus with O2 and nutrients

Question 15

Umbilical cord

Answer 15

• Umbilical V → brings O2 to fetus
• Umbilical A → brings waste to mother

Question 16

Fetal cardiovascular adaptations

Answer 16

• Adults have 2 separate circulatory system (pulmonary & systemic)
• Fetal heart → 1 system (L & R ventricles function in parallel to perfuse body and placenta)

Question 17

Fetal hemoglobin affinity

Answer 17

• Much lower PO2
• Lower O2 saturation
• Higher hemoglobin conc
  
  • Carry more O2 from mother
  • Higher affinity for oxygen
  • O2 consumption is high

Question 18

4 unique fetal shunts

Answer 18

• Ductus venosus
  
  • Abdominal umbilical V to IVC → via R atrium → formane ovale
• Foramen ovale
  
  • Bypass R atrium → L atrium
• Ductus arteriosus
  
  • R vent → pulmonary A → straight to descending aorta
• Umbilical circulation
  
  • 1 vein brings O2 blood placenta to fetus
  • 2 arteries remove deO2 blood

Question 19

Adaptations at birth - umbilical circulation

Answer 19

• Clamped umbilical cord (lose umbilical A & V)
• Vessels bringing deO2 blood disintegrate

Question 20

Adaptations at birth - Ductus venosus

Answer 20

• Closed 1-3 weeks after birth (later in premature babies)
  
  • Trigger unknown

Question 21

Adaptations at birth - Foramen ovale

Answer 21

• Mechanical atrial pressure
• Baby takes first breath → pressure gradient change → mechanical pressure close forman ovale

Question 22

Adaptations at birth - ductus arteriosus

Answer 22

• Pressure gradient closes it → pulmonary A becomes dominant
• Closes 2 days after birth
• O2 mediated prostagladin inhibition
• Patent ductus (when it stays open) → deO2 blood mixed with O2 blood from the lungs