Download mesodermal

Differentiation of
the mesoderm.
Muscular system
BLUE ectoderm - WHITE amnion YELLOW - endoderm
parallel happenings!
RED - mesoderm
GASTRULATION
The extraembryonic central
mesoderm
- somatopleura
(parietal mesoderm)
- splanchnopleura
(visceral mesoderm)
becomes continuous with
the newly formed
intraembryonic mesoderm
axial mesoderm (notochord)
paraaxial mesoderm
lateral plate mesoderm
dorsal aorta
cavity between the layers
intraembryonic
coelomic cavity
paraaxial mesoderm
intermediate mesoderm
SAME
lateral plate,
NAMES!!!
somatopleura
lateral plate,
splanchnopleura
PARAAXIAL MESODERM - SEGMENTS
beginning of 3rd week
- somitomeres
in cephalic region
- somites (from day 20)
- Occ 4
-C8
- T 12
-L5
-S5
- Coc 8-10 (...41-43)
day 21 - 4-7
day 25 - 17-20
day 30 - 34-35
Based on the number of somites we can compare different creatures!
intraembryonic
mesoderm
axial mesoderm
paraxial mesoderm
intermediate mesoderm
lateral mesoderm
somatopleura
splanchnopleura
mesoderm
extraembryonic
mesoderm
central mesoderm
somatopleura
splanchnopleura
connecting stalk- mesoderm
chorion mesoderm
(peripheral mesoderm)
ectoderm
removed
1. dermatome
2. myotome
dermomyotome
(each has its own segmental nerve!)
3.
sclerotome
later
PARAAXIAL MESODERM
earlier
intermediate mesoderm
“gononephrotome”:
( .. later pro-, meso-, and metanephros...)
- cervical, upper thoracic
segmented (nephrotomes)
- caudally unsegmented
nephrogenic cord
LATERAL PLATE
parietal mesoderm (somatopleura): serous membrane
and c.t. of body wall (overlying ectoderm will give epidermis)
visceral mesoderm (splanchnopleura):
serous membrane, c.t., and
smooth muscle of gut
(endoderm will give epithelium
and glands)
Beginning of 3rd week:
wall of yolk sac, chorion,
connecting stalk:
angioblasts
- endothelial cells
- blood cells
(later also within the embryo
→ fusion,
→ placental circulation)
Muscular system
from mesodermal germ layer
-paraaxial mesoderm
- skeletal
-splanchnic mesoderm
- smooth
- cardiac
- somatopleura
- m. arrector pili
Skeletal muscle:
Myotome cells
myoblasts
fusion
Somitomeres + 4 occipital somites: muscles for the head
(eye, jaw, larynx, tongue - cranial nerves!!)
Somites: limbs and trunk (axial muscles, body wall)
MYOTOME
epimere (dorsal rami of spinal nerves)
hypomere
(ventral rami)
upper: C4 – T2
lower: L2 – S2
muscle in
limb bud
motor and
sensory
innervation
of myotomes
and
dermotomes
5th week
7th week
neural tube
VERTEBRAL COLUMN
sclerotome
notochord
spinal nerve
segmental - myotome
- nerve
nucleus pulposus in
intervertebral disk
notochord
*
V
V
1
2
3
*
S
S
S
ectodermal
- epidermis and its
appendices
- neural crest, placodes
- central and peripheral
nervous system
mesodermal
- c.t. and supportive tissue
- all muscles
- heart, blood, lymph vessels,
spleen
- urogenital tract (most)
- cortex of suprarenal gland
endodermal
- lining of intestinal and
respiratory tract
- parenchyma of thyroid,
parathyroids, liver, pancreas
- lining of urethra and bladder
- lining of tympanic cavity
and auditory tube