Placenta

Q: Following ovulation and fertilization of an ovum, a blastocyst develops. Growth and differentiation occurs following implantation. Which of the following differentiated tissues will develop into the placenta?

Trophoblast. Early in development, cells in the blastocyst destined to become the placenta become trophoblasts that line a blastocystic cavity, with an inner cell mass composed of embryoblasts destined to become the fetus. Hence, the placenta is a fetal structure, not a maternal structure. ---

Q: Following birth, circulation from placenta to fetus ceases. Which of the following fetal structures that conducts blood to the inferior vena cava becomes atretic in postnatal life?

Ductus venosus. The ductus venosus extends from

Q: Which immunoglobulin is the only one capable of crossing the placenta to provide passive immunity to the fetus?

IgG. IgG is actively transported across the placenta via the neonatal Fc receptor (FcRn).

Placenta praevia or another condition in which vaginal delivery is contraindicated.

What our notes say

Placenta praevia or another condition in which vaginal delivery is contraindicated. (Junior Clerkship in Reproductive Health II CAT — October 2022)
It is used for placenta praevia, a poorly formed lower segment or a transverse back-down lie, and it needs repeat caesarean in future pregnancies. (Junior Clerkship in Reproductive Health (MBOG 4200): end of year examination, 4 )
Other acceptable complications include wound dehiscence, ileus, adhesions, transfusion-related complications and complications in subsequent pregnancies such as placenta praevia/accreta or uterine scar complications. (Junior Clerkship in Reproductive Health II CAT — October 2022)
Topics tested: physiology of pregnancy, diagnosis of pregnancy, placenta and fetal circulation, abortion, ectopic pregnancy, molar pregnancy, safe motherhood, birth plan, preconception care. (Reproductive Health 1 End of Trimester CAT: 40 MCQs and 4 short answers)
Nutrients reach the fetus only after the mother's stores, diet and metabolism have supplied them and the placenta has transferred them. (Reproductive Health 1 End of Trimester CAT: 40 MCQs and 4 short answers)
Anaesthetic complications, and uterine scar problems in later pregnancies (rupture, placenta praevia or accreta) (Reproductive Health End of Trimester 2 CAT (MBOG 4223): labour and cord prolapse)

Study material on Placenta

Images

Two placental specimens: A shows a centrally-inserted cord, B shows a cord inserting at the placental margin with a fan of vessels

Photo of an intestinal segment with a small blind-ended outpouching

Diagram of an abnormally adherent placenta with regions A and B labelled

Number 14 - several placenta specimens, normal and abnormal

Number 16 - placenta specimen with the fetal membranes doubled back at the margin

Diagram of a fetus with the umbilical cord, A, beside a placenta with an accessory lobe, B

Practice questions on Placenta

Following ovulation and fertilization of an ovum, a blastocyst develops. Growth and differentiation occurs following implantation. Which of the following differentiated tissues will develop into the placenta?

Epimere
Neural plate
Sclerotome
Trophoblast
Umbilical vesicle

Answer: D. Early in development, cells in the blastocyst destined to become the placenta become trophoblasts that line a blastocystic cavity, with an inner cell mass composed of embryoblasts destined to become the fetus. Hence, the placenta is a fetal structure, not a maternal structure. ---

Following birth, circulation from placenta to fetus ceases. Which of the following fetal structures that conducts blood to the inferior vena cava becomes atretic in postnatal life?

Azygous vein
Ductus arteriosus
Ductus venosus
Foramen ovale
Umbilical artery

Answer: C. The ductus venosus extends from

Which immunoglobulin is the only one capable of crossing the placenta to provide passive immunity to the fetus?

Answer: B. IgG is actively transported across the placenta via the neonatal Fc receptor (FcRn).