Week 2: Difference between revisions

Revision as of 14:48, 22 July 2010

Introduction

Key events of human development during the second week (week 2) following fertilization or Clinical week 4 (LMP).

Week 2 Links: Lecture - Week 1 and 2 | Implantation

Timeline

Day	Stage	Event
8		Implantation
9
10
11
12
13	Stage 6	Chorionic Cavity
14

Week 2 and 3 Movies


Implantation	Mesoderm	Chorionic Cavity	Amniotic Cavity	Week 3

Implantation

The second week of human development is concerned with the process of implantation and the differentiation of the blastocyst into early embryonic and placental forming structures.

implantation commences about day 6 to 7
Adplantation - begins with initial adhesion to the uterine epithelium
- blastocyst then slows in motility, "rolls" on surface, aligns with the inner cell mass closest to the epithelium and stops
Implantation - migration of the blastocyst into the uterine epithelium, process complete by about day 9
coagulation plug - left where the blastocyst has entered the uterine wall day 12

Normal Implantation Sites - in uterine wall superior, posterior, lateral

Week 2 Abnormalities

Abnormal Implantation

Ectopic tubal pregnancy

Ectopic Pregnancy | Movie - Ectopic pregnancy ultrasound

Abnormal implantation sites or Ectopic Pregnancy occurs if implantation is in uterine tube or outside the uterus.

sites - external surface of uterus, ovary, bowel, gastrointestinal tract, mesentry, peritoneal wall
If not spontaneous then, embryo has to be removed surgically

Tubal pregnancy - 94% of ectopic pregnancies

if uterine epithelium is damaged (scarring, pelvic inflammatory disease)
if zona pellucida is lost too early, allows premature tubal implantation
embryo may develop through early stages, can erode through the uterine horn and reattach within the peritoneal cavity

Monoygotic Twinning

Monozygotic twins (identical) produced from a single fertilization event (one fertilised egg and a single spermatazoa, form a single zygote), these twins therefore share the same genetic makeup. Occurs in approximately 3-5 per 1000 pregnancies, more commonly with aged mothers. The later the twinning event, the less common are initially separate placental membranes and finally resulting in conjoined twins.

Week		Week 1							Week 2
Day	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
Cell Number	1	1	2	16	32	128				bilaminar
Event	Ovulation	fertilization	First cell division	Morula	Early blastocyst	Late blastocyst Hatching	Implantation starts			X inactivation

Monoygotic Twin Type		Diamniotic Dichorionic			Diamniotic Monochorionic			Monoamniotic Monochorionic			Conjoined

Table based upon: Twinning. Hall JG. ^[1]

References

↑ <pubmed>12957099</pubmed>

Carnegie Stages: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | About Stages | Timeline

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Cite this page: Hill, M.A. (2024, June 3) Embryology Week 2. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Week_2

What Links Here?

[1] <pubmed>12957099</pubmed>

[1]

@@ Line 67: / Line 67: @@
 |-
 |}
+== Implantation ==
+The second week of human development is concerned with the process of implantation and the differentiation of the blastocyst into early embryonic and placental forming structures.
+*  implantation commences about '''day 6 to 7'''
+* '''Adplantation''' - begins with initial adhesion to the uterine epithelium
+** blastocyst then slows in motility, "rolls" on surface, aligns with the inner cell mass closest to the epithelium and stops
+* '''Implantation''' - migration of the blastocyst into the uterine epithelium, process complete by about '''day 9'''
+* '''coagulation plug''' - left where the blastocyst has entered the uterine wall '''day 12'''
+'''Normal Implantation Sites''' - in uterine wall superior, posterior, lateral
 ==Week 2 Abnormalities==
+===Abnormal Implantation===
+[[Image:Tubal pregnancy.gif|thumb|Ectopic tubal pregnancy]]
+[http://embryology.med.unsw.edu.au/Notes/week2_2.htm Ectopic Pregnancy] | [http://embryology.med.unsw.edu.au/Movies/usoundab/Ectopic1.htm Movie - Ectopic pregnancy ultrasound]
+Abnormal implantation sites or Ectopic Pregnancy occurs if implantation is in uterine tube or outside the uterus.
+* sites - external surface of uterus, ovary, bowel, gastrointestinal tract, mesentry, peritoneal wall
+* If not spontaneous then, embryo has to be removed surgically
+'''Tubal pregnancy''' - 94% of ectopic pregnancies
+* if uterine epithelium is damaged (scarring, pelvic inflammatory disease)
+* if zona pellucida is lost too early, allows premature tubal implantation
+* embryo may develop through early stages, can erode through the uterine horn and reattach within the peritoneal cavity
 ===Monoygotic Twinning===
@@ Line 190: / Line 211: @@
 Table based upon: Twinning. Hall JG. <ref><pubmed>12957099</pubmed></ref>
 ==References==