Please feel free to chat amongst yourselves until we begin at the top of the hour. 1

Seminar Agenda Unit Material Self Assessment Questions Questions & Answers 2

Blastocyst formation 3

Attachment of the blastocyst to the endometrial epithelium 4

Implantation of the blastocyst 5 As blastocyst implants (6-10 days), more trophoblast contacts the endometrium and differentiates into: Cytotrophoblast – layer of cells that are mitotically active and forms new cells that migrate into the increasing mass of syncytiotrophoblast, where they fuse and lose their cell membrane Syncytiotrophoblast – a rapidly expanding multinucleated mass in which no cell boundaries are discernable.

Syncytiotrophoblast invade the endometrial connective tissue. The also produce human chorionic gonadotrophin hormone (hCG) – actually enters the maternal blood and maintains the corpus luteum. 6

Question What is hCG (human chorionic gonadotrophin) used to detect? 7

Question What is hCG (human chorionic gonadotrophin) used to detect? Answer: Pregnancy. hCG is detected in pregnancy tests. 8

Days 10 and 12: 9 Embryonic disc forms: Epiblast – thick layer of high columnar cells related to amniotic cavity Hypoblast – small cuboidal cell adjacent to the exocoelomic cavity These line the umbilical vesicle or yolk sac Lacunar network – provides embryo with nutrients from mother Epiblast Hypoblast Closing plug is closed; there is a small elevation in the endometrial surface.

At 12-days, there is a small elevation in the endometrial surface due to the implanted conceptus. 10

Section of a 12- day embryo 11

Days 13 and 14 At 13 days, there is a decrease in relative size of the primary umbilical vesicle and the early appearance of primary chorionic villi. At 14 days, there is newly formed secondary umbilical vesicle and the location of the prechordal plate. 12

Development of the chorionic sac at day 14 13

Endovaginal sonogram of an early chorionic sace 14

Day 14 Embryo 15

Origin of Embryonic Tissues 16

Ectopic pregnancy 17

Implantation Sites of Blastocysts 18

A tubal pregnancy 19

Third Week: Gastrulation Embryo referred to as gastrula. Each of the three germ (ectoderm, mesoderm and endoderm) layers give rise to specific tissues and organs: Embryonic ectoderm gives rise to the epidermis, central and peripheral nervous systems, the eye, and inner ear, and, as neural crest cells, to many connective tissues of the head. 20

Third Week: Gastrulation Embryonic endoderm is the source of the epithelial linings of the respiratory and alimentary (digestive) tracts, including the glands opening into the gastrointestinal tract and the glandular cells of associated organs such as the liver and pancreas. 21

Third Week: Gastrulation Embryonic mesoderm gives rise to all skeletal muscles, blood cells and the lining of blood vessels, all visceral smooth muscular coats, the serosal linings of all body cavities, the ducts and organs of the reproductive and excretory systems, and most of the cardiovascular system. In the trunk, it is the source of all connective tissues, including cartilage, bones, tendons, ligaments, dermis, and stroma of internal organs. 22

Third Week: Gastrulation The bilaminar embryonic disc is converted into a trilaminar embryonic disc. 23

Week 2: SA Question 1 The bilaminar blastoderm (embryonic disc or germ disc) consists of: A. Mesoderm and hypoblast B. Mesoderm and ectoderm C. Epiblast and ectoderm D. Epiblast and hypoblast E. Epiblast and mesoderm 24

Week 2: SA Question 1 Answer The bilaminar blastoderm (embryonic disc or germ disc) consists of: A. Mesoderm and hypoblast B. Mesoderm and ectoderm C. Epiblast and ectoderm D. Epiblast and hypoblast CORRECT ANSWER E. Epiblast and mesoderm 25

Days 10 and 12: 26 Embryonic disc forms: Epiblast – thick layer of high columnar cells related to amniotic cavity Hypoblast – small cuboidal cell adjacent to the exocoelomic cavity These line the umbilical vesicle or yolk sac Lacunar network – provides embryo with nutrients from mother Epiblast Hypoblast Closing plug is closed; there is a small elevation in the endometrial surface.

Week 2: SA Question 2 Which part of the embryonic disc that develops as a localized thickening of hypoblast and marks the future cranial end of the embryo called? A. Zona pellucida B. Extraembryonic coelom C. Precordal plate D. Chorionic sac E. Amnion 27

Week 2: SA Question 2 Which part of the embryonic disc that develops as a localized thickening of hypoblast and marks the future cranial end of the embryo called? A. Zona pellucida B. Extraembryonic coelom C. Precordal plate CORRECT ANSWER D. Chorionic sac E. Amnion 28

Days 13 and 14 At 13 days, there is a decrease in relative size of the primary umbilical vesicle and the early appearance of primary chorionic villi. At 14 days, there is newly formed secondary umbilical vesicle and the location of the prechordal plate. 29

Week 2: SA Question 3 __________ develops from a ruptured ovarian follicle: A. Corpus luteum B. Zona pellucida C. Prechordal plate D. Ectopic implantation E. Chorionic sac 30

Week 2: SA Question 3 Answer __________ develops from a ruptured ovarian follicle: A. Corpus luteum CORRECT ANSWER B. Zona pellucida C. Prechordal plate D. Ectopic implantation E. Chorionic sac 31

Week 2: SA Question 4 ________________ surrounds embryo, amnion and umbilical vesicle (yolk sac): A. Corpus luteum B. Zona pellucida C. Ectopic implantation D. Prechordal plate E. Chorionic sac 32

Week 2: SA Question 4 Answer ________________ surrounds embryo, amnion and umbilical vesicle (yolk sac): A. Corpus luteum B. Zona pellucida C. Ectopic implantation D. Prechordal plate E. Chorionic sac CORRECT ANSWER 33

Development of the chorionic sac at day 14 34

Week 2: SA Question 5 ___________ forms the ventral layer of the embryonic disc: A. Corpus luteum B. Prechordal plate C. Chorionic plate D. Epiblast E. Hypoblast 35

Week 2: SA Question 5 Answer ___________ forms the ventral layer of the embryonic disc: A. Corpus luteum B. Prechordal plate CORRECT ANSWER C. Chorionic plate D. Epiblast E. Hypoblast 36

Days 13 and 14 At 13 days, there is a decrease in relative size of the primary umbilical vesicle and the early appearance of primary chorionic villi. At 14 days, there is newly formed secondary umbilical vesicle and the location of the prechordal plate. 37

Week 2: SA Question 6 __________ is the most common site of an ectopic pregnancy. A. Uterus B. Cervix C. Uterine tube D. Peritoneal cavity E. Ovary 38

Week 2: SA Question 6 Answer __________ is the most common site of an ectopic pregnancy. A. Uterus B. Cervix C. Uterine tube CORRECT ANSWER D. Peritoneal cavity E. Ovary 39

Week 2: SA Question 7 Human chorionic gonadotrophin is secreted by the: A. Epiblast B. Exocoelomic membrane C. Cytotrophoblast D. Syncytiotrophoblast 40

Week 2: SA Question 7 Answer Human chorionic gonadotrophin is secreted by the: A. Epiblast B. Exocoelomic membrane C. Cytotrophoblast D. Syncytiotrophoblast CORRECT ANSWER 41

Week 2: SA Question 8 Lacunar networks: A. Form in the syncytiotrophoblast B. Are the primordial of the intervillous space of the placenta C. Both A and B D. Neither A nor B 42

Week 2: SA Question 8 Answer Lacunar networks: A. Form in the syncytiotrophoblast B. Are the primordial of the intervillous space of the placenta C. Both A and B CORRECT ANSWER D. Neither A nor B 43

Week 2: SA Question 9 During morphogenesis, populations of cells can do the following: A. Increase in number owing to mitosis B. Decrease in number owing to apoptosis C. Change their position by migrating D. All of the above E. None of the above 44

Week 2: SA Question 9 Answer During morphogenesis, populations of cells can do the following: A. Increase in number owing to mitosis B. Decrease in number owing to apoptosis C. Change their position by migrating D. All of the above CORRECT ANSWER E. None of the above 45

Questions 46