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ER Exam 2 > Fertilization and implantation > Flashcards

Fertilization and implantation Flashcards

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1
Q

When does fertilization typically occur during the menstrual cycle?

A

Day 15-16

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2
Q

About how many sperm actually reach the oviduct?

A

200 out of 300 million

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3
Q

Clinically, what sperm count per millimeter of ejaculate is considered infertile?

A

<20 million

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4
Q

What is estrogen’s effect on sperm transport in the cervix and uterus?

A

Cervix - production of watery mucus for aid of motile sperm

Uterus: Contraction of myometrium to help propel sperm

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5
Q

During capacitation of the sperm, where are the inhibitory factors of the head washed away?

A

Uterine and fallopian tubes

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6
Q

What are the 3 layers the sperm must breach during fertilization?

A

Corona radiata

Zona pellucida

Oocyte membrane

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7
Q

What do the sperm cells bind in the zona pellucida?

A

ZP3 glycoproteins

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8
Q

What is the purpose of the cortical reaction? Where is it initiated and what occurs?

A

Prevent polyspermy

Initiated by increased Ca2+ inside oocyte

Release enzymes that cause zona pellucida proteins to harden

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9
Q

What does the increase in calcium cause in the oocyte after the cortical reaction?

A

Completeion of 2nd meiotic division and formation of the second polar body (Haploid)

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10
Q

What event represents the end of fertilization and beginning of embryonic development?

A

Mingling of chromosomes

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11
Q

What day is the morula formed? How many cells?

A

Day 3, 16 cells

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12
Q

On what day does the embryo reach blastocyst stage?

A

Days 4, 5

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13
Q

What are the connections between outer cells of the morula?

A

Desmosomes and gap junctions

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14
Q

What causes formation of the blastocyst cavity within the morula?

A

Active transport of Na+ from trophoblast cells and osmosis of water

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15
Q

What is a pinopod and when does it appear?

A

Small-fingerlike protrusions on endometrial cells that endocytose macromolecules and uterine fluid and absorb most of the fluid in the lumen of the uterus

Day 19-21 (luteal phase)

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16
Q

What inhibits development of pinopods?

A

Estrogens

17
Q

How does hCG signal to the mother’s body that she is pregnant?

A

Sustains function of corpus luteum => prevents menstruation and produces progesterone levels necessary to sustain pregnancy

18
Q

What type of endocrine factor is hCG?

A

Autocrine

19
Q

What hormone is closely associated with hCG?

A

LH

20
Q

What event initiates implantation?

A

Contact between blastocyst and uterine wall

21
Q

What is the role of syncytiotrophoblast in interstitial implantation? During what phase of implantation?

A

Adhesion-supported invasion and migration of syncytiotrophoblastic cells into endometrium

Breaks down extracellular matrix with matrix metalloproteases and other hydrolytic enzymes

During invasion phase

22
Q

What steroid hormone does syncytiotrophoblast synthesize?

A

Progesterone, assists in maintaining pregnancy independent of corpus luteum

23
Q

What is hatching of the blastocyst? When?

A

Lytic factors in endometrial cavity that dissolve the zona pellucida

6-7 days after ovulation

24
Q

What are the 3 stages of implantation?

A

Apposition

Adhesion

Invasion

25
Q

What occurs during the apposition phase of implantation? How is the blastocyst oriented?

A

Blastocyst makes contact with a small crypt in the endometrium

Apical side (with ICM) pointing towards endometrium

26
Q

What transmembrane glycoprotein may be involved with apposition? Where is it located?

A

MUC1

Located on apical surface of endometrium

27
Q

What occurs during the adhesion phase of implantation? Through what interactions?

A

Trophoblast attaches to uterine epithelium (zona compacta) through microvilli of trophoblast

Ligand-receptor interactions

28
Q

During the invasion phase of implantation, the syncytiotrophoblast protrusions secrete what?

A

TNF-a, which inhibits cadherins and B-catenin

29
Q

How far do the syncytiotrophoblast protrusions reach?

A

Through basement membrane of uterine epithelial cells to the uterine stroma

30
Q

Uterine stromal cells transform during what phase of implantation and are then known as what?

A

Invasion phase

Decidual cells (become rich in lipids and glycogen)

31
Q

What is decidualization?

A

Formation of decidua cells into an epithelial-like sheet with adhesive junctions that prevent migration of implanting embryo

ER Exam 2 (16 decks)

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