ANAT2341: Week 1 and 2

Dr Annemiek Beverdam – School of Medical Sciences, UNSW Wallace Wurth Building Room 234 – A.Beverdam@unsw.edu.au

Resources ANAT2341:http://php.med.unsw.edu.au/embryology/

Larsen’s Human EmbryologyThe Developing Human: Clinically Oriented Embryology

Week 1/2 Lecture overview

Dr Annemiek Beverdam – School of Medical Sciences, UNSW Wallace Wurth Building Room 234 – A.Beverdam@unsw.edu.au

Resources:http://php.med.unsw.edu.au/embryology/

Larsen’s Human EmbryologyThe Developing Human: Clinically Oriented Embryology

Fertilization

Cleavage stages

Morula formation

Blastocyst formation

Implantation

Generation of bilaminar embryo and matyernal decidua

Endometriosis

Twinning

Week 1

Week 2

Week 1/2

Fertilization/Zygote formation

Spermatozoa Sperm Binding (SED1/ZP3)

Acrosome Reaction Membrane Fusion

OocyteMembrane Depolarization

Cortical Reaction Meiosis II

Zygote FormationDiploid cell

Male and Female pronuclei First mitotic division within 24h

http://php.med.unsw.edu.au/embryology/images/c/c0/Fertilization_001.mp4

Cleavage stages - Day 1-5Blastomeres

No growth (G1/G2) stagesCompaction

Trophoblast/inner cell massSynchronous/asynchronous cell division

Blastocoel formation (Na+/K+ pump)Zona Pellucida

Fig 1-16 Larsen’s

Blastomere contacts and communicationTight and adherens junctions, and desmosomes: seal Gap junctions: communication

Hatching of the Blastocyst – Day 5

Fig 1-16 Larsen’s

Blastocyst hatching

Hatching (day 5)Multiple roles for zona pellucida

Ectopic pregnancies

http://php.med.unsw.edu.au/embryology/images/a/ae/Human_blastocyst_day_3-6.mp4

http://php.med.unsw.edu.au/embryology/images/b/b4/Week1_001.mp4

Week 1 of development

Fig 1-16 Larsen’s

Week 2: Implantation: Menstrual Cycle

hypothalamus:GnRH

Pituitary:LH - FSH

Endometrial growth

Follicle maturation

Estrogen

LH surge

Ovulation

Fertilization:

Corpus luteum

Progesterone(in response

to hCG)

Maintenance of endometrium

Nofertilization:

Corpus albicans

No Progesterone

Loss of endometrium

Implantation Menses

Week 1-2 Week 3-4

Week 2: Implantation: Uterus

Uterine wall consists of:- Endometrium (cycling)- Myometrium (parturition)- Perimetrium (tunica serosa)

Endometrium consists of:- Basilar zone (not lost, own blood supply)- Functional (spongy) zone, ovarian gland bodies,

cycles)- Compact zone: columnar epithelium, stromal

cells, ovarian gland necks: implantation

Week 2: Implantation: Endometrium

Endometrial receptivity window: 6-10 days after fertilization

Decidual reaction: Endometrial transformation (stroma)Spreads from implantation siteFacilitates implantation

Endometrial Receptivity

window

Decidual reaction

Week 2: Implantation: EmbryoDuring receptivity window of menstrual cycle

Adplantation: day 6-7 (Decidual reaction)Note orientation of blastocyst!

Implantation: days 8-9

Ectopic pregnancy

http://php.med.unsw.edu.au/embryology/images/a/a6/Week2_001.mp4

endometrialstroma

Adplantation Implantation

Week 2: Implantation: EmbryoTrophoblast: syncytiotrophoblast and cytotrophoblast

Inner cell mass: epiblast and hypoblast

Generation of bilaminar embryoAmniotic cavity and primary yolk sac

Start of placentation

Syncytiotrophoblast produces:Proteolytic enzymes

Human chorionic gonadotropin (hCG) hormone

http://php.med.unsw.edu.au/embryology/images/a/a6/Week2_001.mp4

endometrialstroma

Adplantation Implantation

Bilaminar Embryo and CavitationDay 10-13

http://php.med.unsw.edu.au/embryology/images/c/c1/Chorion_001.mp4

Bilaminar Embryo and CavitationDay 12-13

Extraembryonic mesoderm forms chorionic cavity (embryonic)Epiblast forms amniotic cavity (embryonic)

Blastocoel cavity becomes definitive yolk sac (embryonic) Endometrium forms the decidua (Maternal)

Bilaminar EmbryoDay 13-14

DeciduaDecidua Basalis: forms placenta

Decidua Capsularis: surrounds chorionic cavityDecidua Parietalis: rest of uterine mucosa

Endometriosis Ectopic endometrial tissue (ovaries, fallopian tubes)

Cycles in response to LH and progesterone

Twinning

Monozygotic twinning: identical genetic material

Type of monozygotic twin isdetermined by the timing of embryonic division:

A: 0-4 dpf: embryo splits in 2dichorionic, diamniotic

B: 4-8 dpf: ICM splits, distant embryoblastsMonochorionic, diamniotic

C: 8-12 dpf: ICM splits, Close embryoblastsMonochorionic, mono-amnionic

D: 8-12 dpf: ICM splits partiallyMonochorionic, mono-amnionicConjoined twins

ImplantationWeek 2

Week 1/2 Lecture overview

Dr Annemiek Beverdam – School of Medical Sciences, UNSW Wallace Wurth Building Room 234 – A.Beverdam@unsw.edu.au

Resources:http://php.med.unsw.edu.au/embryology/

Larsen’s Human EmbryologyThe Developing Human: Clinically Oriented Embryology

Fertilization

Cleavage stages

Morula formation

Blastocyst formation

Implantation

Generation of bilaminar embryo and matyernal decidua

Endometriosis

Twinning

Week 1

Week 2

Labs Relevant to this Lecture

Preimplantion, early implantation and gastrulation (Lab 1)

Assisted Reproductive Technology (Lab 2)

Genetic modification of mice (Lab 4)