View
235
Download
4
Category
Tags:
Preview:
Citation preview
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Lecture 1:From Fertilization to
Gastrulation
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Why Embryology?• Birth defects are the leading cause of infant mortality.
• Birth defects are a major contributor to morbidity, including physical and mental handicaps.
• All women of childbearing age are at risk of having an infant with a birth defect. The incidence rate is 6/100 births.
• Each of you will have contact with women of childbearing age; either as a friend, as a companion, or as a patient. Or you are one yourself.
• MANY BIRTH DEFECTS CAN BE PREVENTED!
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
1st Prenatal Visit: 8 Weeks
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
The First Week
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
From the Morula Stage to Compaction
Morula (3 Days) Compacted Embryo
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Formation of the Blastocyst and Implantation
Blastocyst (4-5 Days) Implanting Blastocyst (6 Days)
Syncytiotrophoblast
Cytotrophoblast
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Hydatidiform Moles
• Formed from trophoblast
• Paternal genome (genomic imprinting)
• Secrete high levels of hCG (syncytiotrophoblast)
• May become invasive (choriocarcinomas)
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
First Week of Development
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Sites for Ectopic Pregnancies
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Tubal Pregnancy
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Ectopic Pregnancy in the Rectouterine (Douglas) Pouch
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Assisted Reproductive Technologies (ART)
Fertility treatments in which both the eggs and sperm are handled in the laboratory (i.e., in vitro fertilization and related procedures). Eggs and sperm are placed in a culture medium; fertilized eggs are placed in the uterus.
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
ART Cycles Performed, Live-Birth Deliveries, and Live Babies Born Using ART—US, 1996-2002
115,392 procedures reported to CDC in 2002; 45,751 infants born after ART in US (1.1% of all births)
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Adverse Outcomes Potentially Associated with ART
• Embryo effects• Spontaneous abortions• Multiple births• Adverse perinatal outcomes: low birth weight,
preterm delivery (even among singleton births)• Birth defects• Developmental disabilities• Childhood malignancies• Longer term outcomes?
• Effects on puberty/future fertility• Effects on chronic disease risk
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
0
20
40
60
80
100
120
LBW VLBW Preterm
% a
dv
ers
e p
eri
na
talo
utc
om
es
Singletons Twins Triplets +
Percentage of Adverse Perinatal Outcomes among ART Infants by Plurality -- US, 2002
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Percent LBW among ART singletons (1996-1997) compared to all singleton births to
non-teen mothers in US (1997)
13.2
2.6
5.7
1
0
5
10
15
LBW VLBW
Per
cen
t
ART
USPopulation
Schieve et al., N Engl J Med 346:731-7, 2002
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Large Meta-Analysis Study
30-40% Increased Risk of Birth Defects from ART
From: Hansen et al., Human Reproduction, 20: 328, 2005
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Implantation with Formation of Two Layers in the Embryoblast and the Trophoblast
Implanting Blastocyst (6 Days) Implanted Embryo (7.5 Days)
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Early Trophoblast (Placental) and Embryonic Development
9 Days
12 Days
13 Days
Yolk sac cavity
Oropharyngeal
membrane
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
15 days15 Days
2nd Week = Week of Two’s
Cytotrophoblast: Syncytiotrophoblast & Cytotrophoblast
Extraembryonic Mesoderm: Visceral (splanchnic) & Parietal (somatic) Layers
Embryonic Disc: Epiblast & Hypoblast
(Parietal layer)
Extraembryonic
mesoderm (Visceral layer)
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Formation of the Primitive Streak and Establishment of the Cranial-Caudal Axis
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
BMPs: Hatched area = ventral mesoderm (kidneys and body wall) and ectoderm
BMPs (goosecoid, brachyurea T) = dorsal mesoderm (somites) and neural ectoderm
Anterior Visceral Endoderm (AVE) Induces the Cranial Region
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Overexpression of Goosecoid in Frogs Causes Double-Headed Tadpoles: Does It Cause This Defect in Humans?
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Genetic Regulation of Laterality
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Situs Inversus Kartagener syndrome (20%) Cilia malfunction with situs inversus (bronchiectasis and sinusitis)
Laterality Sequences Left or right sidedness Asplenia (right) Polysplenia (left)
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Gastrulation: Formation of the 3 Germ Layers
14 Days 16 Days
Oropharyngeal membraneOropharyngeal
membrane
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
During Gastrulation, Epiblast Cells Move Toward the Primitive Streak, Leave the Epiblast, and Create 2 New Layers
Oropharyngeal membrane
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Formation of the Prechordal Plate and Notochord
Oropharyngeal membrane
Oropharyngealmembrane
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
Formation of the Notochord
A
Cut lines for C B
Oropharyngeal membrane
Copyright © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins
The Three Germ Layers
Mesoderm
EndodermNotochord (Part of the mesoderm)
Ectoderm
• Ectoderm: skin, CNS, PNS, eyes, internal ear, neural crest cells (bones and connective tissue of the face and part of the skull)
• Mesoderm: bones, connective tissue, urogenital system, cardiovascular system
• Endoderm: gut and gut derivatives (liver, pancreas, lungs, etc.)
Recommended