Fetal Circulation, Gestation, and Birth

Question 1

maternal and fetal blood…

Answer 1

cannot mix because the two may be different blood types

Question 2

how do nutrients, gases, and wastes get exchanged in the placenta?

Answer 2

diffusion
partial pressure gradients

Question 3

HbF

Answer 3

• fetal hemoglobin
• enhances transfer of oxygen into fetal circulation
• greater affinity for oxygen than HbA
• waste material and carbon dioxide move in opposite direction

Question 4

how the placenta protects the fetus

Answer 4

• crossing of antibodies across placental membrane
• acts as an endocrine organ because it produced estrogen, progesterone, and hCG which are needed to maintain pregnancy

Question 5

umbilical arteries

Answer 5

carry blood away from the fetus towards the placenta
deoxy blood

Question 6

umbilical vein

Answer 6

• carries blood toward the fetus from the placenta
• carries oxygenated blood

Question 7

pathogens that can cross the placental barrier

Answer 7

TOxoplasma
Rubella
Cytomegalovirus
HErpes
Hiv
Syphilis

Question 8

Which 2 organs are unused until parturition?

Answer 8

• lungs and liver
• gas, nutrient, and waste exchange occurs at the placenta
• detoxification and metabolism is done by mothers liver

Question 9

how does the fetal body protect the underdeveloped lungs and liver in utero?

Answer 9

3 shunts to direct blood away from them: foramen ovale, ductus arteriosus, ductus venosus

Question 10

foramen ovale

Answer 10

• one-way valve connecting r atrium and l atrium
• redirects blood entering RA (higher pressure) into LA into systemic circulation instead of RV

Question 11

ductus arteriosus

Answer 11

• shunts leftover blood from pulmonary artery to the aorta

Question 12

ductus venosus

Answer 12

• shunts blood returning from the placenta via umbilical vein directly into IVC
• the liver still receives some blood supply from smaller hepatic arteries in the systemic circulation

Question 13

first trimester

Answer 13

• major organs begin to develop
• 22 days in there’s heartbeat
• quickly after eyes, gonads, limbs, and liver start to form
• by week 5 embryo is 10 mm in length, and by week 6 it has grown to 15 mm
• 7th week cartilaginous skeleton begins to harden into bone
• 8th week most organs have formed, brain fairly developed and now embryo is a fetus
• ends first trimester at about 9 cm long

Question 14

second trimester

Answer 14

• tremendous growth
• moves within amniotic fluid
• faces begins to look human
• fingers and toes elongate
• 30-36 cm long

Question 15

third trimester

Answer 15

• rapid growth and further brain development
• antibodies are transported by highly selective active transport from the pregnant individual to the fetus for protection against foreign agents in prep for life outside the womb (occurring since beginning but happens most ninth month)
• growth rate then slows and fetus move around less (less room)

Question 16

birth

Answer 16

• vaginal birth parturition
• rhythmic contraction of uterine smooth muscle coordinated by prostaglandins and the peptide hormone oxytocin
• phase 1: cervix thins, amniotic sac ruptures, water breaks
• phase 2: strong uterine contractions result in birth
• phase 3: placenta and umbilical cord expelled