Netter's Atlas of Human Embryology

318 Pages·2016·25.74 MB·English

by  Netter F.H.

w w w . m e d i c a l m c q s d o w n l o a d . b l o g s p o t . c o m
m
AN OVERVIEW OF DEVELOPMwENnTlAoLa EVdE.NbTSl o, PgROsCpESoSEt .Sc, o
ANmD cABqNsORdMoALITIES: TIMELINE
m e d i c a l Prenatal Time Scale (Months)
w .
w
w
First 2 weeks
Main Period
This is a period of cell proliferation
from the zygote to the morula,
blastocyst, and formation of the Weeks 3 to 8 is the dynamic period of
bilaminar embryonic disc. Birth defects gastrulation, folding of the embryo, and
do not originate in this period because the formation of all the organ systems.
body systems and structures have not Because this is the most active period
yet developed. Teratogens usually of development and differentiation, the
cause the loss of the entire conceptus. embryo in weeks 3 to 8 is most
vulnerable to major birth defects.
Fetal Period
Months 3 to 9 (full term) are mainly
characterized by the growth of all the
major structures that have already
appeared. Birth defects in this period
are usually not as severe or obvious
and include small size, mental
retardation, and defects in the eyes,
ears, teeth, and external genitalia.
m
The Firwst Wneleok a d . b l o g s p o t . c o
m c q s d o
m e d i c a l
w .
w
w
Early morula Four-cell stage
(approx. 80 hr) (approx. 40 hr)
Two-cell stage
(approx. 30 hr)
Endometrium----,\
Advanced
morula (4 days)
Ovary
Blastocyst
(approx. 5 days)
Fertilization
Early implantation (12to24 hr)
Developing
(approx. 6 1/2 days)
follicles
Mature
follicle
Inner cell mass Discharged
(embryoblast) ovum
m
The Secownd nWleoeka d . b l o g s p o t . c o
m c q s d o
m e d i c a l
w .
w
w
=::·e~ ======~~;~~~~~
cavity ---
Epiblast ----~
¥---:::---- --Hypoblast - - -.....,.,t!,
Heuser's membrane- -
---·Prim yolk sac ---
Extraembryonic mEtsoder·m --~
Approximately 12th day
Approximately 7 1/2 days
plah<~~~~""""
Prechordal
Yolk sac:...._
lntraembryonic
mesoderm
coelom
-:----. Endometrium
'--Exocelomic cyst Approximately 17th day
Approximately 15th day
m
The Embryownicn Pl eorioadd . b l o g s p o t . c o
m c q s Ddorosal Views
m e d i c a l
w .
w
w
Cranial
Somi tes appear
Neural
neuropore
20)
Late closure
Early closure
of neural tube
of neural <uuc ./
(day 22)
(day
I I
1.8mm 2.0- 2.1 mm
Caudal
neuropore
Week 3 (late) Week 4 (early)
m
The Embryownicn Pl eoriaodd . b l o g s p o t . c o
m c q sSdagiottal Views
m e d i c a l
w .
w
w
Pharyngeal arches Maxillary prominence
appear (day 26) of 1st pharyngeal arch
Mandibular portion of
1st pharyngeal arch
1st pharyngeal arch
2nd pharyngeal arch
pharyngeal arch
/ ~ 3rd pharyngeal arc~
pharyngeal arch
~ -4th pharyngeal
P
": \ arch
.....
''
Lens placode
Heart
L""'u
buds appear
/l (days 28-29)
Umbilical cord
I
..,. 5.0 nun
4.0mm
Tail
Week 4 (middle) Week 4 (late)
m
The Embryownicn Pl eoriaodd . b l o g s p o t . c o
m c q s d o
m e d i c a l
w .
w
w
1st pharyngeal groove
Developing eye
/ 'External ear
1
(optic cup)
Digital
rays
develop\--.:::::... _ _.
Elbow
T
~13.4mm
,
10.5mm
Week 5 (late) Week 6 (early)
External
Eyelids ear
Separated
digits
Webbed
digits
I
•
30mm
20mm
Umbilical
hernia
Week 7 Week 8
m
The Fetawl Pnerilood a d . b l o g s p o t . c o
m c q s d o
m e d i c a l
w .
w
w
Intestines return to abdomen
(week 10) N ote: CRL=5 crown
to-rump length
Sex distinguishable
(week 12) Hair appears
(week 20)
Early fetal period
(week 8-week 16
CRL 5.0-14 em)
Eyes open
(week '" ,.-
Fingernails appear
(week 24) ----....;:,;~
Toenails appear
(week
Firm grasp
(week 36) --.__,..~-
Fetus is thin with
little body fat. Fetus
Middle fetal period
viable by week 22
(week 17-week 30
CRL 15-28 em)
Testes in .._• .
scrotum or
inguinal canal
(week 38)
Rapid weight gain and fat
deposition beginning in week 32
results in typical "plump"
appearance of term fetus late fetal period
(week 31 -week 38
CRL28-36 em)
m
His to logicawl Cnonlcoepatsd . b l o g s p o t . c o
Blastomcystc wiqth esmdbryoo within the uterine mucosa
m e d i c a l
w .
w
w
Loose connective tissue
Simple tall columnar epithelium
Simple cuboidal epithelium
Primitive yolk sac
Maternal blood vessels
Simple squamous epithelium
Approximately 7 1/2 days
m
Histologicawl Cnonlcoepatsd . b l o g s p o t . c o
mLocoseq ansd ddenose connective tissue
m e d i c a l
w .
w
w
Monocyte
Mast cell
Red blood cell
Endothelial cell
Pericyte
-
Eosinophil
/ l)l
Plasma cell
Longitudinal bundles
of collagen and/or
elastic fibers
•
Tendon sectioned longitudinally
Transverse fibers of
and transversely
Fibroblast nuclei loose connective tissue