Chapter 21
General Embryology
---a science which study the processes and
regulations of development of human
fetus.(from 1 cell(zygote) to (5-7)X1012 cells )
---total 38 weeks:
preembryonic period,before 2 weeks
embryonic period,3-8 weeks
fetal period,after 9 weeks
*perinatal stage,26 weeks to birth
*Teratology,abnormal development of fetus
1.Fertilization
---definition,the process by
which the male and
female gametes(sperm
and ovum) unite to give
rise to zygote
---place,in the ampullary
region of the fallopian
tube
---conditions:
1) maturation of oocyte
2) maturation of spermatozoon:
/ductus epididymus,2-3 weeks,forward
motility protein
3) capacitation of spermatozoa:
decapacitation factor,exist in
epididymus,to inhibit the release of
acrosome enzymes
capacitation factor,secreted by epi.
cells of oviduct,capacity of releasing
acrosome enzymes
4) quality and quantity of spermatozoa:
2-6 ml,100,000,000/ml,
<1.5 ml; or <10,000,000; abnormal
sperm >30%; or capacity for mobile<
70%
5) meeting of sperm and ovum
sperm,20-24h
ovum,15-18h(1-3ds)
---processes of fertilization:
1) acrosome reaction:
/hyaluronic acidase,dissolve corona radiate
* interact with ZP3(receptor glycoprotein,exist
in zona pellucide) molecules,release
/acrosin,dissolve zona pellucide
/enter perivitelline space
2) spermatozoa fuse with the membrane of
ovum,nucleus enter cytoplasm of ovum
3) monospermy:
cortical reaction,cortical granules(located in
cytoplasm of ovum) are released into
perivitelline space,and cause
zona reaction,change of ZP3 molecules in
zona pellucide
4) formation of zygote(fertilized ovum)
secondary meiosis complete,form second
polar body
male pronucleus fuse with female
pronucleus,to restore the 2n chromasome
---significance of fertilization:
1) a new life begin(initiation of cleavage)
2)restoration of the diploid number of
chromosomes,cross-over
3) determination of the sex of the new individual:
ova(22+X) + X-bearing spermatozoon = girl
ova(22+X) + Y-bearing spermatozoon = boy
*klinefelter’s syndrome,47XXY,48XXXY
2,Blastocyst formation and implantation
1) cleavage and blastocyst formation
① cleavage
---blastomere,cells formed by cleavage
/30h,2
/40h,4
/72h,12-16- morula
② formation of blastocyst,by 5th day,
blastomere reach to 107,small space appear
between them
---blastocoele,filled with liquid
---trophoblast
---inner cell mass
---polar trophoblast
2) Implantation
---definition,the process by which the
blastocyst is embedded in endometrium
---time,5th –6th day begin; 11th –12th day
complete
---processes,zona pellucide disappear → polar
trophoblast touch the endometrium→secrete
proteolytase →dissolve the endometrium →
embedded into endometrium→coagulation plug
seal the space
* trophoblast become into two layers when
blastocyst is embedding into endometrium
syncytiotrophoblast
cytotrophoblast
---place:
/posterior wall of fundus and body of uterus
placenta praevia
ectopic pregnancy
---decidual response of endometrium
/stroma cell→predecidual cell→decidual
cell(cell become larger and rich in glycogen
and lipid droplet)
/endometrium →decidua,
-decidua basalis
-decidua capsularis
-decidua parietalis
---conditions:
/endometrium is in secretory phase
/morula reach the cavity of uterus on time
/zona pellucide disappears in time
3,Formation and differentiation
of trilaminar germ disc
1) formation of endoderm and ectoderm,early
of 2 weeks,inner cell mass differentiate into
two layers of cells
---bilaminar germ disc,epiblast(columnar)
+hypoblast(cuboidal)
---epiblast,primary ectoderm
/amniotic membrane,amnioblast
/amniotic cavity
/amniotic fluid
/amnion
---hypoblast,primary endoderm
/extraembryonic endoderm→exocoelomic
membrane→primary yolk sac →
exocoelomic vesicle
/extraembryonic mesoderm,→ extraembryonic
cavity,chorionic cavity
-visceral layer
-parietal layer
/secondary yolk sac,yolk sac
---body stalk,formed by extraembryonic
mesoderm
2) formation of mesoderm,early of 3 weeks
---primitive streak,cells of epiblast proliferate to
form a longitudinal arranged cell cord
---primitive groove
---primitive node
---primitive pit
---mesoderm,intraembryonic mesoderm
---endoderm,hypoblast cells are replaced by
epiblast cells
---ectoderm,epiblast changed the name into
ectoderm
* trilaminar germ disc,endoderm + mesoderm +
ectoderm
* determination of head and tail of germ disc
---head process→notochordal tube → notochord
---buccopharyngeal membrane
---cloacal membrane
3)differentiation of trilaminar germ disc,4th –8th
weeks
---differentiation,same cells which are
primordial and inmuture differentiate into
different cells which have specific structure
and function
---induction,some tissues effect the
differentiation,and determine the
differentiating orientation of another tissue
① differentiation of ectoderm,from 18th –19th days
---neural plate,neuro-epithelium(neural ectoderm):
pseudostratified columnar epi.
---neural fold
---neural groove
---neural tube,→CNS
/anterior neuropore,closed by 25th days
/posterior neuropore,closed by 27th days
---neural crest(mesoectoderm),two lines of cell
cords→ganglion
② differentiation of mesoderm,17th days
---paraxial mesoderm
somite,20th days,3 pairs/per day,42-44 pairs
by the end of 5th weeks
-sclerotome,→bone,cartilage
-myotome,→skeletal muscle
-dermatome,dermis and hypodermis
---intermediate mesoderm,→kidney and
reproductive gland
nephrotome,segmentation
nephrogenic cord:
---lateral mesoderm:
intraembryonic coelom,→body cavity
somatic or parietal mesoderm,→muscle,CT,
parietal layer of pleura,peritoneum and
pericardium
splanchnic or visceral mesoderm,→muscle,CT of
digestive tract,visceral layer of pleura,peritoneum
and pericardium
---mesenchyme,→cardiovascular and lymph system
③ differentiation of endoderm:
---primitive gut,→digestive,respiratory
and urinary system
4,The
development
of fetal
membrane
and placenta
1) chorion:
---formed by
trophoblast and
extraembryonic
mesoderm
---primary stem villus,projections of cytotrophoblast
and syncytiotrophoblast
---secondary stem villus,extraembryonic mesoderm
enter the primary stem villus
* chorionic plate,trophoblast + extraembryonic
mesoderm
* chorion,secondary stem villus + chorionic plate
---tertiary stem villus,extraembryonic mesoderm
differentiate into CT and BV
free villus,branches
anchoring villus
---cytotrophoblastic cell column:
→cytotrophoblastic shell
---chorion leave,6 weeks later
---chorion frondosum
---hydatidiform mole
---chorion carcinoma
2) yolk sac:
---blood island,primitive blood cell- derived from
extraembryonic mesoderm on the wall of yolk
sac
---primordial germ cell,derived from endoderm
of yolk sac
3) amnion:
---amniotic membrane,amniotic epi,+
extraembryonic mesoderm
---amniotic fluid:
/secrete by amniotic epi.
/slight basic fluid,500-1000ml
-polyhydramnios,>2000 ml,abnormal
digestive system or CNS
-oligohydramnios,<500 ml,abnormal urinary
system
/function:
-intraenvironment
-protecting
-preventing from adherence
-wash germ tract
4) allantois
---allantoic A,paired,→umbilical A
---allantoic V,paired
right,degenerate
left,umbilical V
5) umbilical cord
---cylindrical structure
---surface,amniotic membrane
---cord,mucous CT,umbilical A,V,yolk
sac and allantois
---40-60 cm long,1.5-2.0 cm in D
---> 80 cm,or < 35 cm
6) placenta:
---the structure by which exchange of material
between fetus and mother takes place
---size,round,disc-shaped,15-20 cm in D,2.5
cm thickness,500g in weight
fetal surface,smooth,
covered by amniotic
membrane
mother surface,rough,
15-30 cotyledons
---structure:
/chorionic plate
/chorion and chorion space
-chorion,60 chorion stalks→branches
-chorion space,space between chorion,
filled with mother blood
/basal plate,cytotrophoblastic shell +
deciduas
-placental septa,separate the chorion into
cotyledon
---blood circulation of placenta
fetus,umbilical A →cap, of chorion
→umbilical V
mother,spiral A → chorion space →
uterus V
* placental barrier:
/the structure between fetal and
maternal blood
/components:
-endothelium of chorion capillary and its
basal lamina
-CT in the core of the villus
-trophoblast epithelium and its basal
lamina
---function:
a,the exchange of material between the
maternal and fetal blood streams
b,defense barrier
c,the production of hormones:
/human chorionic gonadotropin,HCG:
-begin,end of 2nd week
-highest lever,9th –11th week
-lowest lever,20th week,until birth
/human placental lactogen,HPL
-similar to HGH
-highest lever,36th –37th week
/human placental progesterone,HPP and
human placental estrogen,HPE
-begin,4th month
/other hormones,human chorionic
thyrotropin,HCT; human chorionic
adrenocorticotrophic hormne,HCATH;
prostaglandin
General Embryology
---a science which study the processes and
regulations of development of human
fetus.(from 1 cell(zygote) to (5-7)X1012 cells )
---total 38 weeks:
preembryonic period,before 2 weeks
embryonic period,3-8 weeks
fetal period,after 9 weeks
*perinatal stage,26 weeks to birth
*Teratology,abnormal development of fetus
1.Fertilization
---definition,the process by
which the male and
female gametes(sperm
and ovum) unite to give
rise to zygote
---place,in the ampullary
region of the fallopian
tube
---conditions:
1) maturation of oocyte
2) maturation of spermatozoon:
/ductus epididymus,2-3 weeks,forward
motility protein
3) capacitation of spermatozoa:
decapacitation factor,exist in
epididymus,to inhibit the release of
acrosome enzymes
capacitation factor,secreted by epi.
cells of oviduct,capacity of releasing
acrosome enzymes
4) quality and quantity of spermatozoa:
2-6 ml,100,000,000/ml,
<1.5 ml; or <10,000,000; abnormal
sperm >30%; or capacity for mobile<
70%
5) meeting of sperm and ovum
sperm,20-24h
ovum,15-18h(1-3ds)
---processes of fertilization:
1) acrosome reaction:
/hyaluronic acidase,dissolve corona radiate
* interact with ZP3(receptor glycoprotein,exist
in zona pellucide) molecules,release
/acrosin,dissolve zona pellucide
/enter perivitelline space
2) spermatozoa fuse with the membrane of
ovum,nucleus enter cytoplasm of ovum
3) monospermy:
cortical reaction,cortical granules(located in
cytoplasm of ovum) are released into
perivitelline space,and cause
zona reaction,change of ZP3 molecules in
zona pellucide
4) formation of zygote(fertilized ovum)
secondary meiosis complete,form second
polar body
male pronucleus fuse with female
pronucleus,to restore the 2n chromasome
---significance of fertilization:
1) a new life begin(initiation of cleavage)
2)restoration of the diploid number of
chromosomes,cross-over
3) determination of the sex of the new individual:
ova(22+X) + X-bearing spermatozoon = girl
ova(22+X) + Y-bearing spermatozoon = boy
*klinefelter’s syndrome,47XXY,48XXXY
2,Blastocyst formation and implantation
1) cleavage and blastocyst formation
① cleavage
---blastomere,cells formed by cleavage
/30h,2
/40h,4
/72h,12-16- morula
② formation of blastocyst,by 5th day,
blastomere reach to 107,small space appear
between them
---blastocoele,filled with liquid
---trophoblast
---inner cell mass
---polar trophoblast
2) Implantation
---definition,the process by which the
blastocyst is embedded in endometrium
---time,5th –6th day begin; 11th –12th day
complete
---processes,zona pellucide disappear → polar
trophoblast touch the endometrium→secrete
proteolytase →dissolve the endometrium →
embedded into endometrium→coagulation plug
seal the space
* trophoblast become into two layers when
blastocyst is embedding into endometrium
syncytiotrophoblast
cytotrophoblast
---place:
/posterior wall of fundus and body of uterus
placenta praevia
ectopic pregnancy
---decidual response of endometrium
/stroma cell→predecidual cell→decidual
cell(cell become larger and rich in glycogen
and lipid droplet)
/endometrium →decidua,
-decidua basalis
-decidua capsularis
-decidua parietalis
---conditions:
/endometrium is in secretory phase
/morula reach the cavity of uterus on time
/zona pellucide disappears in time
3,Formation and differentiation
of trilaminar germ disc
1) formation of endoderm and ectoderm,early
of 2 weeks,inner cell mass differentiate into
two layers of cells
---bilaminar germ disc,epiblast(columnar)
+hypoblast(cuboidal)
---epiblast,primary ectoderm
/amniotic membrane,amnioblast
/amniotic cavity
/amniotic fluid
/amnion
---hypoblast,primary endoderm
/extraembryonic endoderm→exocoelomic
membrane→primary yolk sac →
exocoelomic vesicle
/extraembryonic mesoderm,→ extraembryonic
cavity,chorionic cavity
-visceral layer
-parietal layer
/secondary yolk sac,yolk sac
---body stalk,formed by extraembryonic
mesoderm
2) formation of mesoderm,early of 3 weeks
---primitive streak,cells of epiblast proliferate to
form a longitudinal arranged cell cord
---primitive groove
---primitive node
---primitive pit
---mesoderm,intraembryonic mesoderm
---endoderm,hypoblast cells are replaced by
epiblast cells
---ectoderm,epiblast changed the name into
ectoderm
* trilaminar germ disc,endoderm + mesoderm +
ectoderm
* determination of head and tail of germ disc
---head process→notochordal tube → notochord
---buccopharyngeal membrane
---cloacal membrane
3)differentiation of trilaminar germ disc,4th –8th
weeks
---differentiation,same cells which are
primordial and inmuture differentiate into
different cells which have specific structure
and function
---induction,some tissues effect the
differentiation,and determine the
differentiating orientation of another tissue
① differentiation of ectoderm,from 18th –19th days
---neural plate,neuro-epithelium(neural ectoderm):
pseudostratified columnar epi.
---neural fold
---neural groove
---neural tube,→CNS
/anterior neuropore,closed by 25th days
/posterior neuropore,closed by 27th days
---neural crest(mesoectoderm),two lines of cell
cords→ganglion
② differentiation of mesoderm,17th days
---paraxial mesoderm
somite,20th days,3 pairs/per day,42-44 pairs
by the end of 5th weeks
-sclerotome,→bone,cartilage
-myotome,→skeletal muscle
-dermatome,dermis and hypodermis
---intermediate mesoderm,→kidney and
reproductive gland
nephrotome,segmentation
nephrogenic cord:
---lateral mesoderm:
intraembryonic coelom,→body cavity
somatic or parietal mesoderm,→muscle,CT,
parietal layer of pleura,peritoneum and
pericardium
splanchnic or visceral mesoderm,→muscle,CT of
digestive tract,visceral layer of pleura,peritoneum
and pericardium
---mesenchyme,→cardiovascular and lymph system
③ differentiation of endoderm:
---primitive gut,→digestive,respiratory
and urinary system
4,The
development
of fetal
membrane
and placenta
1) chorion:
---formed by
trophoblast and
extraembryonic
mesoderm
---primary stem villus,projections of cytotrophoblast
and syncytiotrophoblast
---secondary stem villus,extraembryonic mesoderm
enter the primary stem villus
* chorionic plate,trophoblast + extraembryonic
mesoderm
* chorion,secondary stem villus + chorionic plate
---tertiary stem villus,extraembryonic mesoderm
differentiate into CT and BV
free villus,branches
anchoring villus
---cytotrophoblastic cell column:
→cytotrophoblastic shell
---chorion leave,6 weeks later
---chorion frondosum
---hydatidiform mole
---chorion carcinoma
2) yolk sac:
---blood island,primitive blood cell- derived from
extraembryonic mesoderm on the wall of yolk
sac
---primordial germ cell,derived from endoderm
of yolk sac
3) amnion:
---amniotic membrane,amniotic epi,+
extraembryonic mesoderm
---amniotic fluid:
/secrete by amniotic epi.
/slight basic fluid,500-1000ml
-polyhydramnios,>2000 ml,abnormal
digestive system or CNS
-oligohydramnios,<500 ml,abnormal urinary
system
/function:
-intraenvironment
-protecting
-preventing from adherence
-wash germ tract
4) allantois
---allantoic A,paired,→umbilical A
---allantoic V,paired
right,degenerate
left,umbilical V
5) umbilical cord
---cylindrical structure
---surface,amniotic membrane
---cord,mucous CT,umbilical A,V,yolk
sac and allantois
---40-60 cm long,1.5-2.0 cm in D
---> 80 cm,or < 35 cm
6) placenta:
---the structure by which exchange of material
between fetus and mother takes place
---size,round,disc-shaped,15-20 cm in D,2.5
cm thickness,500g in weight
fetal surface,smooth,
covered by amniotic
membrane
mother surface,rough,
15-30 cotyledons
---structure:
/chorionic plate
/chorion and chorion space
-chorion,60 chorion stalks→branches
-chorion space,space between chorion,
filled with mother blood
/basal plate,cytotrophoblastic shell +
deciduas
-placental septa,separate the chorion into
cotyledon
---blood circulation of placenta
fetus,umbilical A →cap, of chorion
→umbilical V
mother,spiral A → chorion space →
uterus V
* placental barrier:
/the structure between fetal and
maternal blood
/components:
-endothelium of chorion capillary and its
basal lamina
-CT in the core of the villus
-trophoblast epithelium and its basal
lamina
---function:
a,the exchange of material between the
maternal and fetal blood streams
b,defense barrier
c,the production of hormones:
/human chorionic gonadotropin,HCG:
-begin,end of 2nd week
-highest lever,9th –11th week
-lowest lever,20th week,until birth
/human placental lactogen,HPL
-similar to HGH
-highest lever,36th –37th week
/human placental progesterone,HPP and
human placental estrogen,HPE
-begin,4th month
/other hormones,human chorionic
thyrotropin,HCT; human chorionic
adrenocorticotrophic hormne,HCATH;
prostaglandin
