Obstetrics Marrow Pg 265-274 (Fundamentals of Reproduction)
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Questions and Answers

At what age does follicle formation begin during oogenesis?

  • 5 months of intrauterine life
  • 14 weeks (correct)
  • At birth
  • At puberty

    • The fertilizable life span of ova is 24-48 hours.

    False

    What is the primary function of the syncytiotrophoblast?

  • Support fetal growth
  • Initiate embryonic development
  • Form the vascular system
  • Produce hormones for the placenta (correct)

    • The amnion is formed by the inner cell mass.

    <p>False</p> Signup and view all the answers

    What is the maximum number of follicles present in a female ovary at 5 months of intrauterine life?

    <p>6 - 7 million</p> Signup and view all the answers

    Each oogonia gives rise to ___ ova/female pronucleus.

    <p>1</p> Signup and view all the answers

    What are the three parts of the decidua?

    <p>Decidua parietalis, decidua capsularis, chorion laeve</p> Signup and view all the answers

    The _____ is the first site for fetal hematopoiesis.

    <p>Yolk Sac</p> Signup and view all the answers

    Match the following ages with the corresponding number of follicles in the ovary:

    <p>At birth = 1 - 2 million At puberty = 4 - 5 lakh At menopause = No follicles present 5 months of IU life = 6 - 7 million (max)</p> Signup and view all the answers

    Match the following fetal membranes with their characteristics:

    <p>Chorion = Outermost fetal membrane formed by chorion laeve Amnion = Innermost fetal membrane with tensile strength Yolk Sac = First site for fetal hematopoiesis Syncytiotrophoblast = Hormone-producing layer of placenta</p> Signup and view all the answers

    What is the main function of the allantois?

    <p>To connect the hindgut to the connecting stalk</p> Signup and view all the answers

    Preimplantation genetic testing can only be performed using polar body specimens.

    <p>False</p> Signup and view all the answers

    List one disease that can be tested for using preimplantation genetic testing.

    <p>Sickle cell anemia</p> Signup and view all the answers

    The layers penetrated during amniocentesis, starting from the outside, include skin, abdominal wall muscles, uterine serosa, myometrium, endometrium, chorion, and __________.

    <p>amnion</p> Signup and view all the answers

    Match the following specimens with their potential use in preimplantation genetic testing:

    <p>Polar body = Maternal inherited disorders Blastomeres = Inner cell mass Trophectoderm = Best material for testing Amnion = Amniotic fluid protection</p> Signup and view all the answers

    During which period of fetal development is teratogenic exposure considered most critical?

    <p>Embryonic period</p> Signup and view all the answers

    Exposure to less than 5 Rads during pregnancy is considered safe.

    <p>True</p> Signup and view all the answers

    What are the two main complications of radiation exposure greater than 5 Rads during pregnancy?

    <p>Congenital anomalies and intellectual disability.</p> Signup and view all the answers

    The maximum permissible radiation exposure for a pregnant woman is _____ Rads.

    <p>5</p> Signup and view all the answers

    What is the primary hormone responsible for changes in decidualization during pregnancy?

    <p>Progesterone</p> Signup and view all the answers

    Match the following imaging studies with their impact on the fetus:

    <p>USG = No effect on fetus MRI = No effect on fetus X-Ray = Avoided in pregnancy CT Scan = Avoided in pregnancy</p> Signup and view all the answers

    Superfetation is commonly seen in human pregnancies.

    <p>False</p> Signup and view all the answers

    What occurs during 14-16 weeks of pregnancy concerning the decidua?

    <p>The decidua capsularis fuses with the decidua parietalis, leading to the obliteration of the uterine cavity.</p> Signup and view all the answers

    The thickness of the endometrium in non-pregnant females during the secretory phase is ___ mm.

    <p>6</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Decidua basalis = The portion of the endometrium that forms the maternal part of the placenta. Decidua capsularis = The portion of the endometrium that surrounds the implanted blastocyst. Decidua parietalis = The part of the decidua that lines the uterine cavity. Dizygotic twin pregnancy = Two ova fertilized simultaneously after the same act of intercourse.</p> Signup and view all the answers

    What is the correct sequence of zygote development stages after fertilization?

    <p>2-cell zygote → 4-cell zygote → 8-cell zygote → 16-cell zygote</p> Signup and view all the answers

    Zygote formation occurs within 10 hours after fertilization.

    <p>False</p> Signup and view all the answers

    What happens on the 5th day after fertilization?

    <p>Zona hatching occurs, and the blastocyst forms.</p> Signup and view all the answers

    The fertilizable span of the oocyte is _____ hours.

    <p>24</p> Signup and view all the answers

    Match the causes of ectopic pregnancy with their descriptions:

    <p>Decreased peristalsis in the fallopian tube = Slower transport of the fertilized egg Immotile cilia syndrome = Cilia are unable to move the egg Blockage in the fallopian tube = Obstruction preventing normal movement Failure of contraceptive = Conception occurs despite contraceptive measures</p> Signup and view all the answers

    Which compartment of the seminiferous tubules contains spermatogonia and primary spermatocytes?

    <p>Basal compartment</p> Signup and view all the answers

    Sperms reach the fertilization site within 15 minutes after ejaculation.

    <p>False</p> Signup and view all the answers

    What is the time taken for epididymal maturation of sperms?

    <p>12-14 days</p> Signup and view all the answers

    Meiosis I in oogenesis resumes at ______ due to the LH surge.

    <p>puberty</p> Signup and view all the answers

    Match the following terms with their corresponding descriptions in oogenesis:

    <p>Oogonium = 46 (XX) cell that divides to form primary oocyte Primary oocyte = Cell arrested in prophase I Secondary oocyte = Cell that undergoes ovulation Ovum = Final product of oogenesis</p> Signup and view all the answers

    What is the primary process that sperm undergo to become capable of fertilizing the ova?

    <p>Capacitation</p> Signup and view all the answers

    The zona pellucida is a cellular membrane made of glycoprotein.

    <p>False</p> Signup and view all the answers

    What is the function of the substances released by cortical granules during fertilization?

    <p>Prevent polyspermy by hardening the zona pellucida.</p> Signup and view all the answers

    Sperm achieve mobility in the _____ and hypermotility in the _____ reproductive tract.

    <p>epididymis, female</p> Signup and view all the answers

    Match the following events with their sequence number in fertilization:

    <p>Step 1 = Capacitation Step 3 = Acrosomal reaction Step 5 = Meiotic division complete Step 6 = Zona reactions</p> Signup and view all the answers

    What is the main factor responsible for the stage of adhesion during implantation?

    <p>Integrin</p> Signup and view all the answers

    The implantation window occurs from Day 20 to Day 24 of the cycle.

    <p>True</p> Signup and view all the answers

    What is the first sign observed through ultrasound in early pregnancy?

    <p>Gestational Sac</p> Signup and view all the answers

    After implantation, the endometrium is called __________.

    <p>decidua</p> Signup and view all the answers

    Match the types of decidua with their functions:

    <p>Decidua capsularis = Separates blastocyst from uterine cavity Decidua basalis = Forms maternal side of placenta Decidua parietalis = Rest of decidua</p> Signup and view all the answers

    What happens to primordial germ cells (PGC) when the SRY gene is present?

    <p>They differentiate into spermatogonia.</p> Signup and view all the answers

    Spermatogenesis only occurs in females.

    <p>False</p> Signup and view all the answers

    What is the duration of spermatogenesis?

    <p>70-74 days</p> Signup and view all the answers

    The process of transformation from spermatids to mature spermatozoa is called __________.

    <p>spermiogenesis</p> Signup and view all the answers

    Match the stages of spermatogenesis with their corresponding descriptions:

    <p>Spermatogonia = Undifferentiated germ cells found in seminiferous tubules Primary spermatocyte = Cells undergoing meiosis I Secondary spermatocyte = Result of the first meiotic division Spermatids = Cells that have completed meiosis II</p> Signup and view all the answers

    Study Notes

    Fate of Blastocyst

    • Inner cell mass develops into the embryo proper.
    • Trophoblast forms the placenta.
    • Syncytiotrophoblast produces hormones like HCG and HPL.
    • Extravillous trophoblast prevents pregnancy-induced hypertension.
    • Chorion laeve forms the fetal membrane known as Chorion.
    • Chorion frondosum forms villi-like structures on the fetal side of the placenta.
    • Parts of the decidua include decidua parietalis, decidua capsularis, and chorion laeve.

    Fetal Membranes

    • Chorion is the outermost fetal membrane.
    • Amnion is the innermost fetal membrane.
    • Yolk sac is the first site for fetal hematopoiesis and source of α fetoprotein.

    Gametogenesis

    • Oogenesis begins in intrauterine life.
    • Size of ovum: 120 µm.
    • Fertilizable life span of ova: 12-24 hours.
    • Size of follicle just before ovulation: 18-20 mm.
    • Follicle formation begins at 14 weeks.
    • Follicle formation is complete by 22-24 weeks.
    • Each oogonia gives rise to one ova/female pronucleus.

    No. of follicles in ovary based on age:

    • 5 months of IU life: 6-7 million follicles (maximum).
    • At birth: 1-2 million follicles.
    • At puberty: 4-5 lakh follicles.
    • Every month: 1000 follicles undergo atresia.
    • At menopause: No follicles in the ovary.

    Note:

    • Germ cells are pluripotent.
    • Zygote (after 8-cell stage) is totipotent.
    • Germ cells migrate from the yolk sac to the genital ridge, ultimately forming gonads.
    • Failure of migration can lead to the formation of teratomas.

    Allantois

    • A diverticulum that connects the hindgut to the connecting stalk.
    • Membrane rupture releases PGEa, which accelerates labor.

    Layers penetrated during amniocentesis (outside to inside):

    • Skin.
    • Abdominal wall muscles.
    • Uterine serosa.
    • Myometrium.
    • Endometrium (Decidua capsularis + Decidua parietalis).
    • Chorion.
    • Amnion.

    Preimplantation Genetic Testing

    • Done in assisted reproductive techniques.
    • Indications: If one or both parents are carriers of a genetic disorder.
    • Only healthy zygotes are transferred into the uterus.
    • Diseases tested: monogenic disorders, aneuploidy, structural rearrangement of chromosomes, and HLA typing.

    Specimen:

    • Polar body: Only maternal inherited disorders can be tested.
    • Blastomeres: May harm the fetus.
    • Trophectoderm: Best material.

    As Blastocyst Grows

    • Decidua basalis forms the maternal side of the placenta.
    • Decidua capsularis separates the blastocyst from the uterine cavity.
    • Decidua parietalis makes up the rest of the decidua.

    Decidua

    • Obliteration of the uterine cavity occurs as the decidua capsularis moves closer to the decidua parietalis and fuses with it.
    • Obliteration is complete around 14-16 weeks of pregnancy.

    Dizygotic Twin Pregnancy

    • Two ova are released and fertilized at the same time by the same act of coitus.

    Superfetation

    • Not seen in humans.
    • Theoretically possible until 14-16 weeks of pregnancy.

    Changes in Decidualization

    • Hormone responsible for decidualization: Progesterone.
    • Secretory changes in the endometrium: Increased thickness due to stromal edema (most important histological finding).
    • In non-pregnant females, the thickness is 6mm during the secretory phase.

    Teratogenic Exposure of Fetus

    Fetal Growth Period & Radiation Exposure in Pregnancy

    • Fetal Growth Period: Calculated from the day of fertilization.
      • Period of fertilized ova: Up to 2 weeks after fertilization. Teratogenic exposure follows the "all or none law" (fetus either escapes injury or aborts).
      • Embryonic period: 3-8 weeks after fertilization (5th-10th week of pregnancy). Most teratogenic period.
      • Fetal period: ≥ 9 weeks after fertilization.

    Radiation Exposure in Pregnancy

    • Maximum permissible exposure: 5 Rad (0.05 Gy).

    Complications:

    • 5 Rads exposure: ↑ risk of congenital anomalies, IUGR, intellectual disability.

    • ≥ 10 Rads exposure (≥ 0.1 Gy): Fetal loss/abortion.

    Absolute Contraindications (C/I) in pregnancy:

    • Gadolinium enhanced MRI.
    • Radioactive Iodine.
    • Radio opaque/paramagnetic contrast agents.

    Avoided in pregnancy:

    • X-Ray.
    • CT Scan.

    Imaging studies with no effect on fetus:

    • USG.
    • MRI.
    • Dental X-Ray.
    • CT scan (Not involving pelvis/abdomen).

    Accidental X-Ray in pregnancy:

    • Continue the pregnancy.
    • Up to 2 X-rays: no significant adverse effects.

    Process of Fertilization

    • Fusion of male pronucleus (n) and female pronucleus (n) to form zygote (2n) occurs in the ampulla of the fallopian tube.
    • Day of fertilization = Day of ovulation.
    • Fertilizable span of the oocyte is 24 hours.
    • In IVF, the day of oocyte retrieval is equal to the day of fertilization.
    • Zygote formation occurs after 30 hours.

    Stages of Development:

    • 2-cell zygote.
    • 4-cell zygote.
    • 8-cell zygote.
    • 16-cell zygote (develops into a morula).
    • Morula enters the uterine cavity.

    Note: Ectopic Pregnancy

    • Causes: Decreased or absent peristalsis in the fallopian tube, absence of cilia in the fallopian tube, blockage in the fallopian tube (due to adhesions), immotile cilia syndrome (Kartagener syndrome), failure of contraceptive (e.g., progesterone-containing pills), smooth muscle relaxant action (decreased peristalsis).

    Morula

    • Moves towards the uterine cavity.
    • Movement is facilitated by peristalsis in the fallopian tube and movement of cilia.

    Stages After Fertilization

    • Till 3 days after fertilization: Stays in the fallopian tube (FT) for nutrition from secretory cells.
    • 4th day after fertilization (Day 18 of cycle): Enters the uterine cavity (16-celled).
    • 5th day after fertilization:
      • Zona hatching: The zona pellucida (ZP) is lost.
      • Fluids enter the morula, converting it to a blastocyst.

    Compartments of Seminiferous Tubules

    • Basal compartment: Spermatogonia + 1° Spermatocyte (early stages of development).
    • Adluminal compartment: 2° Spermatocyte + Spermatid + Sperms.

    Spermiogenesis

    • Sperms: Size of sperm: 50-60 µm; tail of the sperm has a 9+2 arrangement (formed by centriole).

    Structural Analogues

    Spermatid Sperm
    Nucleus Nucleus
    Mitochondria Mitochondria
    Golgi Apparatus Acrosomal Cap
    Centriole Axial filament/Tail
    Head
    Middle piece (Powerhouse of the sperm)

    Sperms:

    • Fertilisable span of sperm: 48-72 hours.
    • Maturity attained in the proximal epididymis.
    • Motility attained in the distal epididymis.
    • Time taken to reach fertilization site after ejaculation: 30 minutes.
    • Total time taken to form mature sperms (Spermatogenesis + maturation): 90 days.
    • Time taken for epididymal maturation: 12-14 days.

    Oogenesis

    • At puberty, meiosis I resumes due to the LH surge (Hormone dependent).
    • Ovulation: Change from 1° to 2º oocyte; meiosis II begins; meiosis II arrested.
    • Meiosis II resumes at fertilization.

    Diagram of Oogenesis:

    • The diagram shows the process of oogenesis, starting with an oogonium, through the primary oocyte, arrested 1º oocyte, 2º oocyte, ovum, and polar bodies.
    • It highlights the arrest in the dictyate stage of prophase I (absent in spermatogenesis).
    • The diagram emphasizes that tests for ovarian reserve check for the presence of adequate follicles (Ovary is a reservoir of follicles).

    Events Prior to Fertilization

    Capacitation:

    • Process where sperms become capable of fertilizing the ova.
    • Site: Female Reproductive Tract.
    • Time: 6-8 hours (In vitro: 2 hours).
    • Main site: Fallopian tube.

    Sequence of Events:

    1. Capacitation: Sperms become hypermotile.
    2. Sperm Binding: Sperms bind to the zona pellucida.
    3. Acrosomal reaction: Release of enzymes (Hyaluronidase) digests the zona pellucida.
    4. Fusion: The head of a single sperm (male pronucleus) fuses with the oolemma.
    5. Meiotic Division Completion: Meiotic division completes, forming the female pronucleus and polar body.
    6. Cortical reaction: Release of Ca2+ and other substances from cortical granules.
    7. Zona Reactions: Substances released by cortical granules harden the zona pellucida, preventing polyspermy.

    Note:

    • Polyspermy Prevention: Achieved by the cortical reaction and zona reaction.
    • Sperm Travel Time: Takes 30 minutes to reach the fertilization site.
    • Sperm Mobility: Achieved in the epididymis (distal part) and hypermotility in the female reproductive tract.

    Zona Pellucida

    • Structure: Acellular membrane made of glycoprotein.
    • Receptors: ZP3 receptor for sperm head.
    • Function: Prevents polyspermy.

    Diagram:

    • The diagram depicts a secondary oocyte with surrounding structures, including the cumulus oophorus, zona pellucida, first polar body, and perivitelline space.

    • Additional notes:*

    • Time taken for in vitro capacitation is 2 hours.

    Implantation

    • Attachment of the blastocyst to the endometrium.
    • Occurs on day 6 after fertilization (day 20 of cycle).
    • Implantation Window: The time period (day 20 - day 24) when the endometrium/uterus is most receptive for the blastocyst.
    • Interstitial implantation: Implantation deep inside the endometrium.
    • Placental/Hartmann sign: Some experience bleeding at the time of implantation.

    Applied aspect: USG in pregnancy

    • First sign seen: Gestational Sac (G.sac).

    Structures:

    • Gestational Sac (G.sac): Hyperechoic area with an echogenic rim.

    • Intradecidual sign: Presence of the G.Sac deep inside the endometrium.

    Stages of implantation:

    Stage Factor Responsible
    Stage of Apposition Selectin
    Stage of Adhesion Integrin (most important)
    Stage of Penetration Matrix metalloproteinases enzymes

    Implantation Characteristics:

    • Implantation is eccentric.
    • Piskacek sign: Growth of the uterus early in pregnancy is asymmetrical.
    • True gestational sac (of intrauterine pregnancy): Always eccentric.

    Decidualization

    • After implantation, the endometrium is called decidua.

    Types of decidua:

    • Decidua capsularis: Separates the blastocyst from the uterine cavity. Site for future placenta formation.
    • Decidua basalis: Forms the maternal side of the placenta.
    • Decidua parietalis: The rest of the decidua.

    Diagram:

    • The diagram illustrates a cross-section of the uterus, labeling the myometrium, uterine cavity, and the different types of decidua.
    • Another diagram shows a grayscale ultrasound image, detailing the location of the gestational sac (G.sac).

    Gametogenesis

    • Primordial Germ Cells: Gametogenesis begins with the primordial germ cell (PGC).
      • Derived from:
        • Epiblast.
        • Ectoderm.
      • Bipotent cells: They can form spermatogonia/oogonia.
      • Differentiation: Determined by the SRY gene (Sex related gene on chromosome Y).
      • SRY gene on the distal end of the short arm of Chr.Y:
        • Present → PGC → Spermatogonia.
        • Absent → PGC → Oogonia.

    Spermatogenesis

    • At Puberty: SRY gene +ve (XY) Spermatogonia → Type A (Divides and replenishes stores of spermatogonia)/Type B (Pale) undergoes spermatogenesis.

      • (XY) Spermatogonia → (46) Primary spermatocyte (I spermatogonia → 1° spermatocytes).
      • (Secondary spermatocyte (1 1° spermatocyte → 2 2º spermatocytes).
      • Spermatids (Each 2º spermatocyte → 4 spermatids)
      • 1° spermatocytes → 4 spermatids.
      • 1° spermatogonia → 64 spermatids.

    • Meiosis I: Chromosome number halves.

    • Meiosis II: Chromosome number remains the same.

    • Spermiogenesis: Transformation (No meiosis/mitosis)

    • Site: Seminiferous tubules in testes.

    • Spermiation: Process of release of sperm into the lumen of seminiferous tubules.

    • Spermatogenesis: Begins at puberty.

    • Time taken for spermatogenesis: 70-74 days (~72 days).

    • Time taken for spermiogenesis: 10-14 days.

    Diagram Description:

    • The diagram illustrates spermatogenesis, showing a series of cell divisions and transformations leading to the formation of spermatozoa from spermatogonia.
    • Different stages are labeled (spermatogonia, primary spermatocyte, secondary spermatocyte, spermatids, and spermatozoa).
    • The diagram also shows the location of the process within seminiferous tubules and the role of Sertoli cells.

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    Description

    Test your knowledge on human development and the process of oogenesis with this quiz. Covering key concepts like follicle formation, fetal membranes, and genetic testing, this quiz is essential for students of reproductive biology. Challenge yourself with matching questions and facts about early human life.

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