Anatomy: First Week of Pregnancy Development

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Questions and Answers

What is the normal site of fertilization?

Fallopian tube

Uterus

Ovary

Ampullary region of the uterine tube (correct)

What is the result of the acrosome reaction?

Release of hormones to stimulate ovulation

Release of enzymes needed to penetrate the zona pellucida (correct)

Activation of the oocyte's meiotic spindle

Formation of the male pronucleus

During which stage of development does the fertilized egg begin to implant in the uterus?

Gastrulation Stage

Fetal Stage

Zygotic Stage (correct)

Embryonic Stage

What is the function of capacitation in sperm?

To facilitate penetration of the corona radiata Signup and view all the answers

During which day of a regular 28-day menstrual cycle does ovulation occur?

14th day Signup and view all the answers

What is the term for the process of fertilization?

Fusion Signup and view all the answers

What is the purpose of the zona pellucida?

To facilitate fertilization by blocking polyspermy Signup and view all the answers

What is the term for the stage of development from 2-8 weeks?

Embryonic Stage Signup and view all the answers

What is the primary function of syncytiotrophoblasts during implantation?

To erode the endometrium and allow the blastocyst to burrow into the compact layer Signup and view all the answers

During which days does the process of implantation occur?

5th to 10th day Signup and view all the answers

What is the name of the membrane that forms from the hypoblast layer?

Exocoelomic membrane Signup and view all the answers

What is the most common type of ectopic pregnancy?

Tubal pregnancy Signup and view all the answers

What is the name of the cavity that forms from the epiblast layer?

Amniotic cavity Signup and view all the answers

What is the name of the structure that closes the entrance to the blastocyst in the uterine cavity?

Closing plug Signup and view all the answers

What is the characteristic of cells until the 8-cell stage?

They are totipotent Signup and view all the answers

What is the stage of development when the cells are arranged in a hollow sphere?

Blastocyst Signup and view all the answers

What is the outer layer of the blastocyst that will eventually form the placenta?

Trophoblast Signup and view all the answers

At what stage does the zona pellucida disappear?

By day 5-6 Signup and view all the answers

What is the stage of development when the cells are in a compact, solid ball of cells?

Morula Signup and view all the answers

What is the rate of cell division after 72 hours?

32 cells Signup and view all the answers

What is the structure that surrounds the oocyte and the early embryo?

Zona pellucida Signup and view all the answers

When does the morula reach the uterus?

By day 3 Signup and view all the answers

What is the primary function of the syncytiotrophoblasts during implantation?

Secreting proteolytic enzymes to erode the endometrium Signup and view all the answers

During which stage of the uterine endometrium does implantation typically occur?

Secretory phase Signup and view all the answers

What is the primary function of human chorionic gonadotropin (hCG) produced by the syncytiotrophoblasts?

Sustaining the corpus luteum Signup and view all the answers

What is the term for the fluid-filled cavity that forms during blastocyst formation?

Blastocele Signup and view all the answers

What is the primary function of the trophoblast during blastocyst formation?

Forming the epithelial wall of the blastocyst Signup and view all the answers

At which stage of embryonic development have the cells not yet specialized for function?

Undifferentiated stage Signup and view all the answers

What is the rare location where an ectopic pregnancy may fall into?

Pouch of Douglas Signup and view all the answers

What is the timeframe by which Early Pregnancy Factor (EPF) appears in maternal serum?

24-48 hours Signup and view all the answers

What is the stage at which a zygote is transferred to the uterine cavity during In Vitro Fertilization?

4-8 cell stage Signup and view all the answers

What is the result of dispermy during fertilization?

Triploidy Signup and view all the answers

What is the purpose of hormonal stimulation during In Vitro Fertilization?

To form several mature follicles Signup and view all the answers

What is the timeframe by which pregnancy can be confirmed using ultrasonogram?

By the end of 5th week Signup and view all the answers

What is the type of ectopic pregnancy that can secondarily attach to mesenteric blood vessels?

Abdominal pregnancy Signup and view all the answers

What is the type of implantation that occurs at the internal os?

Cervical implantation Signup and view all the answers

Study Notes

Stages of Prenatal Development

Divided into three stages: Zygotic (0-2 weeks), Embryonic (2-8 weeks), and Fetal (9-40 weeks)

Ovulation

Event in which a mature oocyte is expelled from the ovary, occurring on the 14th day of a regular 28-day menstrual cycle

Fertilization

Process by which male and female gametes fuse, occurs in the ampullary region of the uterine tube
Phases of fertilization:
- Penetration of the corona radiata
- Penetration of the zona pellucida
- Fusion of the oocyte and sperm cell membranes
Capacitation: only capacitated sperm can pass through the corona cells and undergo the acrosome reaction, releasing enzymes needed to penetrate the zona pellucida

Cleavage

Mitotic division resulting in blastomeres, with totipotency until the 8-cell stage
Rate of cell division:
- 36 hours: 2 cells
- 48 hours: 8 cells
- 72 hours: 32 cells
- 96 hours: 70 cells

Blastocyst Formation

Fluid begins to penetrate through the zona pellucida into the intercellular spaces of the inner cell mass, forming a single cavity, the blastocele
The embryoblast is at one pole, and the outer cell mass, or trophoblast, flattens and forms the epithelial wall of the blastocyst
The zona pellucida has disappeared, allowing implantation to begin

Implantation

The trophoblastic cells over the embryoblast pole begin to penetrate between the epithelial cells of the uterine mucosa around the sixth day
Syncytiotrophoblasts secrete proteolytic enzymes which erode the endometrium to implant and human chorionic gonadotropin (hCG) which sustains the corpus luteum

Uterus at Time of Implantation

The uterine endometrium passes through three stages during the menstrual cycle: menstrual phase, proliferative phase, and secretory phase

Ectopic Pregnancy

Most common type is tubal pregnancy, which may secondarily attach itself to mesenteric blood vessels and continue as abdominal pregnancy
Rarely, it may fall into the pouch of Douglas

Pregnancy Tests

Early Pregnancy Factor (EPF) appears in the maternal serum by 24 to 48 hours
Assay of hCG and progesterone by the end of the second week
Confirmation of pregnancy by ultrasonogram by the end of the fifth week

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Description

This quiz covers the stages of development from ovulation to implantation in the first week of pregnancy, including fertilization, cleavage, and implantation.