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BLASTULATIO N, IMPLANTATION , FORMATION OF THE ECTODERM AND EN D ODERM. Dr. Andrea D. Székely. CAVITATION OF THE MORULA. 4 days after the ovulation early blastocyst formation 0.1 - 0.2 mm BLASTOCYST - continuous mitotic divisions cavity formation ( blastocoel )

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Presentation Transcript
slide1

BLASTULATION, IMPLANTATION,

FORMATION OF THE ECTODERM AND ENDODERM

Dr. Andrea D. Székely

slide2

CAVITATION OF THE MORULA

  • 4 days after the ovulation
  • early blastocyst formation
  • 0.1 - 0.2 mm
  • BLASTOCYST
  • - continuous mitotic divisions
  • cavity formation (blastocoel)
  • the cells start to compact and flatten
  • BUT the zona pellucida does not enlarge
  • -2 cell types will differentiate:
  • - embryoblast (inner)
  • - trophoblast (outer)

EARLY BLASTOCYSTS

slide3

BLASTULATION

Within the BLASTOCYST an inner cell mass (ICM) is separated, this contains the EMBRYOBLASTS

The surrounding cells will be the TROPHOBLASTS, responsible for

the formation of the chorion.

slide4

HATCHING OF THE BLASTOCYST

  • - enters the uterus 0.1 - 0.2 mm
  • „hatches" from the zona pellucida
  • The implantation starts 5 - 6 days
  • after the ovulation, the blastula descends in the uterine cavity, then adheres to the endometrium (the trophoblasts produce enzymes which pierce the endometrium)
  • APPOSITION (the embryo turns towards the endometrium with
  • the ICM being deep)
  • The superficial proteoglycans bind
  • to the cells
  • - hCG, progesterone release grows
  • Pregnancy test!!
  • The glands enlarge
  • The endometrium thickens
  • A richer vascular network grows
slide6

STEPS OF IMPLANTATION

APPOSITION – the ICM faces the endometrium

ADPLANTATION – the endometrial cells grow processes

(they swell and catch the blastocyst - reversible binding)

ADHESION – the microvilli of the trophoblasta interact with the cells of the

endometrium (proteoglycans) irreversible binding

DIFFERENTIATION - trophoblast derivatives - syncytiotrophoblast

- cytotrophoblast

IMPLANTATION – the syncytiotrophoblasts form a syncytiumot and penetrate the membrana basalis as well as the endometrium

DECIDUAL REACTION – apoptosis within the endometrial cells, then the stroma cells undergo an epitheloid transformation.

The extracellular vacuoles will be filled with blood and merge to form the LACUNAE

the invasive growth will be stopped by the zona compacta

By week 2. the pregnency can be tested from urine too.

slide9

EMBRYOGENESE

Extraembryonic

structures

= Hypoblast

Cindy C Lu*, Jane Brennan† and Elizabeth J Robertson‡

Current Opinion in Genetics & Development 2001, 11:384–392

slide12

EMBRYONIC DISK, HYPOBLAST – EPIBLAST

2. week

the blastocyst partially is implanted, the primitive yolk sac is

formed from the blastocoel

EMBRYOBLASTS: FORM THE EMBRYONIC DISK

hypoblast- cuboidal cells, line the primitive yolk sac

epiblast - tall cylindrical cells lining the amnion cavity

D 11-12. a minimal enlargement of the implanted embryo – bulges into the uterine cavity

extraembryonic mesoderm – formed between the trophoblasts and amnion, or yolk sac –

the cavities here merge to form the extraemberyonic coelom which surrounds the embryonic disk (except for the site of the body stalk „allantois” – later umbilical cord

D 13. the endometrium is completely sealed

Hypoblasts form the secondary or definitive yolk sac

So the extraembryonic coelom will turn to the cavity of the chorion

CRANIAL changes a thickening forms - praechordal plate (BPM)

CAUDAL changes a similar fusion - cloaca membrane,

Similar to the praechordal plate, it is formed by the adjacent layers of

hypo- and epiblast cells

slide13

IN VITRO FERTILIZATION

HSG

ICSI – „intracytoplasmic sperm injection”

Ovarian stimulation (FSH)

„assisted hatching”

Embryo biopsy

Ultrasound assisted

harvesting of the oocyte

slide14

FURTHER MOVIES

http://www.visembryo.com/baby/index.html

http://embryo.soad.umich.edu/

www.advancedfertility.com

http://www.med.uc.edu/embryology/contents.htm