Placenta

PLACENTA

Q. 1

Which hormone produced by the human placenta has LH-like activity?

 A

Progesterone

 B

Testosterone

 C

Human chorionic gonadotropin

 D

Luteinizing hormone

Q. 1

Which hormone produced by the human placenta has LH-like activity?

 A

Progesterone

 B

Testosterone

 C

Human chorionic gonadotropin

 D

Luteinizing hormone

Ans. C

Explanation:

Human chorionic gonadotropin (hCG) is produced in large quantities by the human placenta.

It is used as a pregnancy indicator around 2-weeks post copulation.

This hormone is composed of an alpha and a beta subunit.

Like other gonadotropins, hCG is also glycosylated which influences biological activity.

Human chorionic gonadotropin (hCG) is often used as an exogenous source of LH to try and induce ovulation in some of the domestic species.
 
Ref: Taylor R.N., Badell M.L. (2011). Chapter 16. The Endocrinology of Pregnancy. In D.G. Gardner, D. Shoback (Eds), Greenspan’s Basic & Clinical Endocrinology, 9e. 

Q. 2

The placenta secretes a hormone that participates in stimulation of ductal growth in the mammary gland during pregnancy. This hormone is:

 A

Endothelial growth factor (EGF)

 B

Human chorionic gonadotropin (HCG)

 C

Human chorionic somatotropin (HCS)

 D

Relaxin

Q. 2

The placenta secretes a hormone that participates in stimulation of ductal growth in the mammary gland during pregnancy. This hormone is:

 A

Endothelial growth factor (EGF)

 B

Human chorionic gonadotropin (HCG)

 C

Human chorionic somatotropin (HCS)

 D

Relaxin

Ans. C

Explanation:

All of these hormones are produced by the placenta, but hCG is the hormone that maintains the corpus luteum of pregnancy.

The synthesis and secretion of hCG begins about day 6 of pregnancy, presumably from the trophoblast cells.

Pregnancy tests utilize the measurement of hCG for detection of the embryo. Endothelial growth factor (EGF) is synthesized by the cytotrophoblast cells in the early placenta, then is synthesized by the syncytiotrophoblast cells later (6-8 week old placenta).

EGF maintains the trophoblasts.

Relaxin is synthesized by decidual cells at the time of parturition and acts to “soften” the cervix and pelvic ligaments.


IGF act similarly to EGF by stimulating differentiation of the cytotrophoblast cells. HCS(Human chorionic somatotropin) is synthesized by syncytiotrophoblast cells and will promote general growth.

It is essential in the stimulation of mammary duct proliferation in development of the breast during pregnancy.
 
Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 3. Implantation, Embryogenesis, and Placental Development. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e. 

Q. 3

Which one of the following viruses is least likely to cross placenta?

 A

Rubella

 B

Herpes Simplex Virus

 C

HIV

 D

HBV

Q. 3

Which one of the following viruses is least likely to cross placenta?

 A

Rubella

 B

Herpes Simplex Virus

 C

HIV

 D

HBV

Ans. D

Explanation:

Considering all the above given options, the hepatitis B virus is least likely to cross the placenta due to its larger molecular size (virion of 42nm in diameter) which gives it less access through the placenta. It is not teratogenic.
 
Ref: Dutta Textbook of obstetrics 6th edition, Pages 292, 299-300; Medical disorders in pregnancy: an update By Hiralal Konar, Pralhad Kushtagi, Pages 67-74.

Q. 4

Placenta develops from which of the following embryologic structures ?

 A

Placenta frondosum

 B

Decidua basalis

 C

Chorion

 D

Both A and B

Q. 4

Placenta develops from which of the following embryologic structures ?

 A

Placenta frondosum

 B

Decidua basalis

 C

Chorion

 D

Both A and B

Ans. D

Explanation:

The placenta is developed from two sources.

The principal component is fetal which develops from the chorion frondosum and the maternal component consists of decidua basalis.


Q. 5

All of the following are components of placental barrier, EXCEPT:

 A

Trophoblast

 B

Fetal capillary endothelium

 C

Mesoderm

 D

Amnion

Q. 5

All of the following are components of placental barrier, EXCEPT:

 A

Trophoblast

 B

Fetal capillary endothelium

 C

Mesoderm

 D

Amnion

Ans. D

Explanation:

The fetal and maternal blood is never in contact.

They are separated by the placental barrier or placental membrane, which consists of:

  • Syncytiotrophoblast
  • Cytotrophoblast
  • Basement membrane
  • Mesoderm
  • Endothelium of the fetal capillaries

This thins out as term approaches due to attenuation of the syncytiotrophoblast.

These thinned out areas, offer better exchange between the mother and fetus.

Ref: Textbook of Obstetrics Sheila Balakrishnan, 1st Ed, page 75


Q. 6

Until the end of the 16th week, the placenta grows. At term, ratio of weight of fetus to weight of placenta is:

 A

3 : 1

 B

4 : 1

 C

6 : 1

 D

8 : 1

Q. 6

Until the end of the 16th week, the placenta grows. At term, ratio of weight of fetus to weight of placenta is:

 A

3 : 1

 B

4 : 1

 C

6 : 1

 D

8 : 1

Ans. C

Explanation:

  • Placenta at term is a circular disc with diameter 15-20 cm and thickness of 2.5 cm. Its weight is 500 gm. 
  • The proportion of weight of the fetus to the weight of the placenta is roughly 6:1 at term and occupies about 30% of the uterine wall. 
  • At term, about four-fifths of the placenta is of fetal origin.
Ref: Textbook of Obstetrics by D C Dutta, 6th edition, Page 29.

Q. 7

Normal placenta contains fetal and maternal part. Which is the MOST inner part of placenta?

 A

Decidua basalis

 B

Nitabuch layer

 C

Cytotrophoblast

 D

Syncytiotrophoblast

Q. 7

Normal placenta contains fetal and maternal part. Which is the MOST inner part of placenta?

 A

Decidua basalis

 B

Nitabuch layer

 C

Cytotrophoblast

 D

Syncytiotrophoblast

Ans. D

Explanation:

The placenta is limited internally (fetal aspect) by the amniotic membrane and chorionic plate; externally (maternal aspect) by the basal plate.

Basal plate consists of following structures from outside inwards;
  • Part of the compact and spongy layer of the decidua basalis
  • Nitabuch’s layer of fibrinoid degeneration of the outer syncytiotrophoblast at the junction of the cytotrophoblastic shell and decidua
  • Cytotrophoblastic shell
  • Syncytiotrophoblast
 
Ref: Textbook of Obstetrics by D C Dutta, 6th edition, Page 30.

Q. 8

In the placenta, maternal blood comes in direct contact with:

 A

The syncytiotrophoblast

 B

The cytotrophoblast

 C

Endothelial cells of fetal capillaries

 D

Connective tissue cells of secondary villi

Q. 8

In the placenta, maternal blood comes in direct contact with:

 A

The syncytiotrophoblast

 B

The cytotrophoblast

 C

Endothelial cells of fetal capillaries

 D

Connective tissue cells of secondary villi

Ans. A

Explanation:

The syncytiotrophoblast forms the surface layer of the chorionic villi and is bathed by maternal blood flowing through the intervillous space.

The syncytiotrophoblast is a product of division infusion of cells in the underlying cytotrophoblast.

Fetal capillaries course through the fetal connective tissue that forms the core of all orders of villi, and thus have no contact with maternal blood when placental structure is intact.

As the syncytiotrophoblast is a derivative of the embryonic trophoblast layer, it is incorrect to state that maternal blood has no contact with fetally derived cells.
 
Ref: Cunningham F.G., Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (2010). Chapter 3. Implantation, Embryogenesis, and Placental Development. In F.G. Cunningham, K.J. Leveno, S.L. Bloom, J.C. Hauth, D.J. Rouse, C.Y. Spong (Eds), Williams Obstetrics, 23e.

Q. 9

All of the following are placental hormones, EXCEPT:

 A

Chorionic gonadotropin

 B

Chorionic thyrotropin

 C

Chorionic corticotropin

 D

Chorionic calcitonin

Q. 9

All of the following are placental hormones, EXCEPT:

 A

Chorionic gonadotropin

 B

Chorionic thyrotropin

 C

Chorionic corticotropin

 D

Chorionic calcitonin

Ans. D

Explanation:

Many hormones are secreted by the syncytiotrophoblast of the chorion, and a few additional hormones are produced by the decidual cells. Placental hormones include,

  • Chorionic gonadotropin
  • Chorionic thyrotropin
  • Chorionic corticotropin
  • Estrogens
  • Progesterone
  • Prolactin
  • Placental lactogen
Ref: Paulsen D.F. (2010). Chapter 23. Female Reproductive System. In D.F. Paulsen (Ed), Histology & Cell Biology: Examination & Board Review, 5e.

Q. 10

True about placental hormone is WE

 A

hCS is diabetogenic

 B

hCG rise 1/t nausea

 C

Progesterone production require fetal steroidogenic tissue

 D

Luteal – placental shift at 8-10 weeks

Q. 10

True about placental hormone is WE

 A

hCS is diabetogenic

 B

hCG rise 1/t nausea

 C

Progesterone production require fetal steroidogenic tissue

 D

Luteal – placental shift at 8-10 weeks

Ans. C

Explanation:

C i.e. Progesterone production require f eta steroidogenic tissue


Q. 11

Weight of placenta at term:          

March 2013

 A

300 grams

 B

400 grams

 C

500 grams

 D

600 grams

Q. 11

Weight of placenta at term:          

March 2013

 A

300 grams

 B

400 grams

 C

500 grams

 D

600 grams

Ans. C

Explanation:

Ans. C i.e. 500 grams



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