GERM LAYER DERIVATES
ECTODERM
(surface)
GERM LAYER DERIVATES
ECTODERM
(neural tube)
GERM LAYER DERIVATES
ECTODERM
(neural crest)
GERM LAYER DERIVATES
MESODERM
GERM LAYER DERIVATES
ENDODERM
(epithelial)
GERM LAYER DERIVATES
ENDODERM
(parenchyma)
GERM LAYER DERIVATES
YOLK SAC
Primordial germ cells
+
early blood and blood vessels
WEEK 1
Day 1: fertilization
- spermatozoa undergoes 2 changes in female genital tract
- occurs in ampulla of uterine tube
- secondary oocyte rapidly completes meiosis II
- cortical reaction → preventing polyspermy
WEEK 1
What are the 2 changes that spermatozoa undergoes to make fertilization possible?
Capacitation
removal of proteins from plasma membrane of the acrossome of the spermatozoa
(7 hours in the female genital tract)
Hydrolytic enzymes
released by acrossome in order to penetrate the zona pellucida
(cortical reaction)
WEEK 1
First 4-5 days of week 1
Clivage
(several mitosis)
→
Blastula
→
Morula
(32-cell stage)
→
Blastocyst
WEEK 1
What are the components of blastocyst?
Embryoblast
(inner cell mass)
+
Fluid
+
Trophoblast
(outer cell mass)
WEEK 1
What is the structure derivated from trophoblast?
What are the 2 components of trophoblast?
- Placenta
- Citytrophoblast + Syncytiotrophoblast
WEEK 1
The end of first week: implantation
- degeneration of the zona pellucida
- embryonic pole first
- functional layer of the endometrium (progestional phase of the menstrual cycle)
WEEK 1
Clinical correlation: ectopic pregancy
- tubal (ampulla): most commom form (delayed transport)
- risk factors: endometriosis + pelvic inflammatory disease + tubular pelvic surgery + exposure to diethylestilbestrol (DES)
- clinical signs: sudden pain + missed menstrual period + uterine bleeding (brisk)
- diagnosis: human chorionic gonadotrophin test + sonogram
- abdominal: rectouterine pouch (pouch of Douglas)
WEEK 2
Bilaminar Embryonic Disk
Embryoblast
→
epiblast (amniotic cavity)
+
hypoblast (primary yolk sac)
obs: prechordal plate → fusion of epiblast e hypoblast cells (future mouth)
WEEK 2
Extraembryonic mesoderm
derivated from the epiblast
→
somatic
(covers the amnion + connecting stalk)
+
visceral
(covers the yolk sac)
WEEK 2
Chorionic cavity
chorion (wall of the cavity)
=
extraembryonic somatic mesoderm
+
cytotrophoblast
+
syncytiotrophoblast
(no mitoses + connection to endometrial vessels)
WEEK 2
Hematopoiesis
up to week 6 → mesoderm of yolk sac
week 6 to third trimester → liver + spleen + thymus + bone marrow
WEEK 2
Clinical correlate: human chorionic gonadotropin (hCG) and abnormal levels
- glicoprotein produced by syncytiotrophoblast
- stimulates progesteron production (corpus luteum)
- maternal blood and urine → early pregnancy test
low levels → ectopic pregnancy + spontaneus abortion
high levels → multiple pregnancy + hydatidiform mole + gestacional trophoblastic disease
WEEKS 3-8
Embryonic Period
All major organ systems begin to develop
+
Week 3 → first missed menstrual period
+
Gastrulation
WEEKS 3-8
Gastrulation
Ectoderm
(neuroectoderm + neural crest cells)
Mesoderm
(paraxial - 35 pairs of somites + intermediate + lateral)
Endoderm
Obs: primitive streak formation
WEEKS 3-8
Clinical correlate: sacrococcygeal teratoma
remnants of primitive streak
+
contains various types of tissues
(bone, hair, teeth, nerve)
WEEKS 3-8
Clinical correlate: chordoma
remnants of notochorda
+
intracranially or in the sacral region
WEEKS 3-8
Clinical correlate: hydatidiform mole
- complete/partial replacement of trophoblast to dilated villi
- high levels of hCG
- 20% develop into a malignant trophoblastic disease (including choriocarcinoma)
complete mole: paternal chromossomes only → sperm fertilizies a blighted ovum and reduplicates (46, XX)
partial mole: dispermia (69, XXY)
