BGDA Practical 7 - Week 8

From Embryology

Introduction

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Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8


Key Events of Human Development during the eighth week (week 8) following fertilization or clinical week 10 (GA week 10).

There are 4 Carnegie stages that show external embryo development during this week. This page will give an overview of limb and neural development and look at other system organization compared with the earlier stages. Use the embryo surface views, histological sections, virtual slides and movies to identify the overall developmental anatomy at the end of the embryonic period.

Week 8 - Embryo Stage 23

The following MRI movies show details of the external and internal structure of the human embryo at the end of embryonic development.

Embryo Stage 23 MRI Movies
Stage23 MRI 3D01 icon.jpg
 ‎‎Embryo Surface
Page | Play
Stage23 MRI 3D02 icon.jpg
 ‎‎Embryo CNS
Page | Play
Stage23 MRI S02 icon.jpg
 ‎‎Sagittal Embryo
Page | Play
Stage23 MRI S04 icon.jpg
 ‎‎Sagittal GIT
Page | Play
Stage23 MRI T01 icon.jpg
 ‎‎Trans. Embryo
Page | Play
Stage23 MRI 3D04 icon.jpg
 ‎‎Embryo Surface
Page | Play
Stage23 MRI C01 icon.jpg
 ‎‎Coronal Embryo
Page | Play
Stage23 MRI S01 icon.jpg
 ‎‎Sagittal Head
Page | Play
Stage 23 Links  
Stage 23 MRI Movies: Surface | Central Nervous System | CNS (labeled) | Sagittal | Sagittal (labeled) | Transverse | Transverse (labeled) | Coronal | Sagittal Head (labeled) | Sagittal GIT (labeled) | Carnegie stage 23


Week: 1 2 3 4 5 6 7 8
Carnegie stage: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23


Stage 23 Links: Week 8 | System Development | Lecture - Limb | Lecture - Head Development | Lecture - Sensory | Science Practical - Head | Science Practical - Sensory | Science Practical - Urogenital | Historic - Skull Development | Carnegie Embryos | Madrid Embryos | Category:Carnegie Stage 23 | Next Fetal Development
  Historic Papers: 1954 Stage 19-23




Week 8 - Stage 23 Movies  

Click Here to play on mobile device

Embryo Surface Carnegie Stage 23

This movie shows an unlabeled MRI 3D volume embryo surface scan around the Kyoto embryo (stage 23, week 8).


Note:

  • Size of head relative to trunk.
  • Position and size of limbs.
  • Herniated midgut outside ventral body wall.
Embryo Surface Carnegie Stage 23

This is a second surface view of the stage 23 embryo from photomicrographs.

Compare this to the above MRI view.

Click Here to play on mobile device

Central Nervous System

This movie shows a MRI 3D volume scan inside the Kyoto embryo (stage 23, week 8).

The labelled sagittal head section movie show further detail.


Note:

  • Surface size and position of the CNS within the embryo.
  • Growth of the cortex (telencephalon)
  • Neural flexures forming large IV ventricular space.

Click Here to play on mobile device

Midgut Herniation

This movie shows an extract from the whole embryo sagittal MRI scan (left to right) through a Kyoto embryo (stage 23, week 8).

The extracted region shows the midgut (intestines) lie outside the ventral body wall (midgut herniation) at the end of the embryonic period.

This herniation will not be lost until the early fetal period.

Abnormalities can arise from either abnormal body wall development or from gastrointestinal tract development.

(More? Ultrasound Gastroschisis | Omphalocele)

Stage23 MRI 3D01 icon.jpg
 ‎‎Embryo Surface
Page | Play
Stage23 MRI 3D02 icon.jpg
 ‎‎Embryo CNS
Page | Play
Stage23 MRI S04 icon.jpg
 ‎‎Sagittal GIT
Page | Play
Stage 23 MRI Movies: Surface | Central Nervous System | CNS (labeled) | Sagittal | Sagittal (labeled) | Transverse | Transverse (labeled) | Coronal | Sagittal Head (labeled) | Sagittal GIT (labeled) | Carnegie stage 23


Week: 1 2 3 4 5 6 7 8
Carnegie stage: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23


Stage 23 Links: Week 8 | System Development | Lecture - Limb | Lecture - Head Development | Lecture - Sensory | Science Practical - Head | Science Practical - Sensory | Science Practical - Urogenital | Historic - Skull Development | Carnegie Embryos | Madrid Embryos | Category:Carnegie Stage 23 | Next Fetal Development
  Historic Papers: 1954 Stage 19-23




BGDA Week 4 Movies | BGDA Week 6 Movies | BGDA Week 8 Movies

Head

Oral Cavity Region

Stage 22 image 219.jpg

Sensory

Parts of each sensory system formed from placode origins and each system also has a complex embryonic origin. These images show eye development at the end of the embryonic period.

Stage 22 image 155.jpg
Stage 22 - Eye

Stage 22 image 008-eye.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides

Neural

Stage 22 image 217.jpg

Cortex development commences

  • Ventricular layer (stem cells) proliferate.
  • Differentiating cells migrate away from ventricular layer.
  • Migrating cells stop at the region where the cortex will form.
  • Cells are layered from the inside outwards.

choroid plexus

  • modified vascular structure lying in the ventricles.
  • secretes CSF.

Note

  • All layers between ventricular and developing cortex are only developmental structures.
  • Neurons are formed first, glia are formed later.
  • blockage of narrow ventricular spaces/channels can lead to hydrocephalus.
Stage22 embryo and brain 01.jpg
Stage22-CNS-icon.jpg
 ‎‎Stage 22 Neural
Page | Play

Body

Intraembryonic Coelom the pericardioperitoneal canals close, generating the 3 separate body cavities.


Stage 22 image 200.jpg Stage22 vertebra and spinal cord 1.jpg
Lungs, thymus, musculoskeletal. vertebral column, spinal cord.

Limbs

Week 8 Limb Development
Stage19- limb rotation.jpg

Human Embryo (Stage19) limb rotation

Week 8 (GA week 10) limbs rotate relatively in different directions (Humans Stage 20-23)



Limb Upper Lower
Rotates dorsally (laterally) ventrally (medially)
Rostral thumb toe
Outward elbow faces outward knee faces outward
Extensor muscles   lateral and posterior of limb    anterior aspect of limb
  Links: image | limb | dermatomes | spinal nerve table



This distinctive embryonic rotation establishes the future neural sensory dermatomes pattern, that is segmentally patterned before this rotation.

Stage20-23 limbs.jpg


Links: Limb Development | Limb Abnormalities | Thalidomide

Gastrointestinal Tract

Stage 22 image 203.jpg Gray0986.jpg
The gastrointestinal midgut remains herniated outside of the ventral body wall.
  • midgut continues to elongate during this period.
  • midgut will be enclosed by the growing body wall during early fetal period.
  • cloacal membrane perforates.
Stage22-GIT-icon.jpg
 ‎‎GIT Stage 22
Page | Play
Stage23 MRI S04 icon.jpg
 ‎‎Sagittal GIT
Page | Play

Genital

  • Testis - mesenchyme, interstitial cells (of Leydig) secrete testosterone, androstenedione.
  • Genital 8 to 12 Weeks - hCG stimulates testosterone production.
    • required for internal and external genital tract development.


Human Embryo Male Testis (stage 22)
Stage 22 image 302.jpg Stage 22 image 301.jpg


Human Stage 22: Testis - labeled overview | Testis - unlabeled overview | Testis - unlabeled detail | Testis - labeled detail | testis | Carnegie stage 22 | Movie - Urogenital stage 22


Genital Development will be covered in detail in BGDB.

Extra-embryonic Coelom

  • Chorionic cavity is now lost by fusion with the expanding amniotic cavity.

Placenta cartoon.jpg


Covered in more detail in the Placenta practical.

Other Embryo Systems

Movies - Embryo Carnegie stage 22 - These are rotating animations based upon reconstruction of a human embryo (stage 22) serial slice images.

Stage22 ALL3d.jpg
 ‎‎Systems
Page | Play
Stage22-GIT-icon.jpg
 ‎‎GIT Stage 22
Page | Play
Stage22-CVS-icon.jpg
 ‎‎Cardiovascular
Page | Play
Stage22-CNS-icon.jpg
 ‎‎Stage 22 Neural
Page | Play
Stage22-CNS-icon.jpg
 ‎‎Urogenital
Page | Play
Stage22-CNS-icon.jpg
 ‎‎Skeletal
Page | Play

Critical Periods

The term "critical period" refers to the specific times during human development when exposure to environmental teratogens can cause congenital abnormalities. In general, the effects for each system are more severe (major anomalies) in the embryonic period during organogenesis in the first trimester. Later teratogen exposure are less severe (minor anomalies) in the fetal period during continued growth and differentiation in the second and third trimester. Different systems have different critical periods.


Critical Periods of Human Development
Conceptus Embryonic development (weeks) Fetal period (weeks)
1
2
3
4
5
6
7
8
9
16
20-36
38
Early zygote.jpg Week2 001 icon.jpg Stage9 sem4c.jpg Stage13 sem1c.jpg Stage15 bf1c.jpg Stage17 bf1c.jpg Stage19 bf1c.jpg Stage23 bf1c.jpg
Neural
Stage2.jpg Heart
Upper limbs
Lower limbs
Ear
Eye
CSt3.jpg Palate
Teeth
Week2 001 icon.jpg External genitalia
Loss Major abnormalities Functional and Minor abnormalities
  Critical Period Links: critical period | abnormal development | Critical Periods table | Image - Critical Periods table | Genital | Opioids | Neural | Thalidomide | Environmental


Week 8 Interactive Component

Attempt the Quiz - Week 8  
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Here are a few simple Quiz questions that relate to Week 8 (GA week 10) from the lecture and practical.







  

1

Which of the following statements about neural development is incorrect:

  the ventricular layer contains neural stem cells
  the migrating neural cells stop in the region where the cortex will form
  neurons and not glia differentiate from ventricular neural stem cells
  the cortex neuronal layers develop from the inside outwards
  the differentiating neural cells migrate away from ventricular layer

2

Which of the following structures develops in the extra-embryonic coelom?

  lung buds
  the pancreas
  the spleen
  the ileum
  none of the above

3

Which of the following statements about limb development during week 8 is incorrect:

  the upper limb rotates dorsally
  the lower limb rotates ventrally
  the upper limb rotates laterally
  the lower limb rotates medially
  skin dermatomes are established after limb rotation

4

Which of the following statements about abnormal development is most correct.

  all developmental abnormalities are either genetic or environmental in origin.
  teratogens refer to factors that alter DNA structure.
  teratogens causing major environmental abnormalities mainly during the embryonic period
  none of the above

5

Which of the following systems has the longest critical period window?

  neural
  limb
  heart
  teeth
  none of the above


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Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8


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Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8


Additional Information

Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.

Timeline

Week 8 - Human Embryo Stages and Events (GA week 10) 
Embryo Week: Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 | Week 9
Day
Stage
Event
50
Stage 20 Stage20 bf1c.jpg

Head scalp vascular plexus visible

limb upper limbs begin to rotate ventrally

neural - amygdaloid body has at least four individual nuclei[1]

oculomotor nerve shows a dorsolateral and a ventromedial portion

rhombic lip (rhombencephalon) formation of the cerebellum (intermediate layer) and of the cochlear nuclei

cerebellum cell layer (future Purkinje cells) develops

choroid plexuses of the fourth and lateral ventricles

51
  Gastrointestinal Tract anal (cloacal) membrane perforates
52
Stage 21 Stage21 bf1c.jpg

neural - cortical plate appears in the area of future insula[2]

limb upper and lower limbs rotate

Intraembryonic Coelom pericardioperitoneal canals close

53
   
54
Stage 22 Stage22 bf1c.jpg

neural - neocortical fibres project to epithalamus, to dorsal thalamus, and to mesencephalon[2]

limb fingers and toes lengthen

Sense - Smell Stage 22 to early fetal period - migratory streams of neurons from the subventricular zone of the olfactory bulb towards the future claustrum[3]

55
Genital 8 Weeks Testis - mesenchyme, interstitial cells (of Leydig) secrete testosterone, androstenedione

Genital 8 to 12 Weeks - hCG stimulates testosterone production

Tongue Week 8 - nerves penetrate epitheilai basal lamina and synapse with undifferentiated, elongated, epithelial cells (taste bud progenitor cell)

56
Stage 23 Stage23 bf1c.jpg Stage 23 defines the end of the embryonic (organogenesis) period

mesoderm heart prominence, ossification continues

Head nose, eye, external acoustic meatus, eyelids, external ears, rounded head

Body - straightening of trunk, heart, liver, umbilical cord, intestines herniated at umbilicus

limb upper limbs longer and bent at elbow, hands and feet turned inward, foot with separated digits, wrist, hand with separated digits

Extraembryonic Coelom chorionic cavity is now lost by fusion with the expanding amniotic cavity

neural - rhombencephalon, pyramidal decussation present, nuclei and tracts similar to those present in the newborn cerebellum present as only a plate connected to midbrain and hindbrain through fibre bundles[4]

axial skeleton vertebral column 33 or 34 cartilaginous vertebrae (20-33 mm in total length), vertebral pedicles, articular and transverse processes identifiable (no spinous processes)[5]

 
Week 8 stomach - Week 8 - Gastrin containing cells in stomach antrum. Somatostatin cells in both the antrum and the fundus.
Note - the day timing of stages is only approximate, system names link to first page of that specific system, and events are based upon the literature cited below.
References
  1. Müller F & O'Rahilly R. (1990). The human brain at stages 18-20, including the choroid plexuses and the amygdaloid and septal nuclei. Anat. Embryol. , 182, 285-306. PMID: 2268071
  2. 2.0 2.1 Müller F & O'Rahilly R. (1990). The human brain at stages 21-23, with particular reference to the cerebral cortical plate and to the development of the cerebellum. Anat. Embryol. , 182, 375-400. PMID: 2252222
  3. Müller F & O'Rahilly R. (2004). Olfactory structures in staged human embryos. Cells Tissues Organs (Print) , 178, 93-116. PMID: 15604533 DOI.
  4. Müller F & O'Rahilly R. (1990). The human rhombencephalon at the end of the embryonic period proper. Am. J. Anat. , 189, 127-45. PMID: 2244584 DOI.
  5. O'Rahilly R, Muller F & Meyer DB. (1980). The human vertebral column at the end of the embryonic period proper. 1. The column as a whole. J. Anat. , 131, 565-75. PMID: 7216919


first trimester timeline


Week 8 - Stage 22

These sections provide a detailed histological overview of the internal structures present within the embryo by the end of the embryonic period.

Stage 22 - Eye and Nose

Stage 22 image 008.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Eye

Stage 22 image 008-eye.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Oral Cavity and Inner Ear

Stage 22 image 011.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Larynx and Medulla

Stage 22 image 015.jpg

 ‎‎Mobile | Original

Stage 22 | Embryo Slides
Stage 22 - Neck

Stage 22 image 017.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Atria and Lungs

Stage 22 image 025.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Liver and Ductus Venosus

Stage 22 image 034.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Pelvis

Stage 22 image 048.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Spinal Cord

Stage 22 image 033-spinal-cord.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides
Stage 22 - Spinal Cord (rotated)

Human Stage22 spinal cord03.jpg

 ‎‎Mobile | Desktop | Original

Stage 22 | Embryo Slides


Selected Embryo Histology - Week 8 (Stage 22)  
Links: Carnegie stage 22 | Week 8
All Stage 22 Sections
These are low resolution histology images, the section images start at the head (cranial) end of the embryo and run to the caudal (tail) end. There are available both labelled and unlabelled versions of each section.
Stage 22L serial labeled images
Stage 22 image 050.jpg Stage 22 image 051.jpg Stage 22 image 052.jpg Stage 22 image 053.jpg Stage 22 image 054.jpg Stage 22 image 055.jpg Stage 22 image 056.jpg
A1L A2L A3L A4L A5L A6L A7L
Stage 22 image 057.jpg Stage 22 image 058.jpg Stage 22 image 059.jpg Stage 22 image 060.jpg Stage 22 image 061.jpg Stage 22 image 062.jpg Stage 22 image 063.jpg
B1L B2L B3L B4L B5L B6L B7L
Stage 22 image 064.jpg Stage 22 image 065.jpg Stage 22 image 066.jpg Stage 22 image 067.jpg Stage 22 image 068.jpg Stage 22 image 069.jpg Stage 22 image 070.jpg
C1L C2L C3L C4L C5L C6L C7L
Stage 22 image 071.jpg Stage 22 image 072.jpg Stage 22 image 073.jpg Stage 22 image 074.jpg Stage 22 image 075.jpg Stage 22 image 076.jpg Stage 22 image 077.jpg
D1L D2L D3L D4L D5L D6L D7L
Stage 22 image 078.jpg Stage 22 image 079.jpg Stage 22 image 080.jpg Stage 22 image 081.jpg Stage 22 image 082.jpg Stage 22 image 083.jpg Stage 22 image 084.jpg
E1L E2L E3L E4L E5L E6L E7L
Stage 22 image 085.jpg Stage 22 image 086.jpg Stage 22 image 087.jpg Stage 22 image 088.jpg Stage 22 image 089.jpg Stage 22 image 090.jpg Stage 22 image 091.jpg
F1L F2L F3L F4L F5L F6L F7L
Stage 22 image 092.jpg Stage 22 image 093.jpg Stage 22 image 094.jpg Stage 22 image 095.jpg Stage 22 image 096.jpg Stage 22 image 097.jpg Stage 22 image 098.jpg
G1L G2L G3L G4L G5L G6L G7L


Stage 22 serial unlabeled images
Stage 22 image 001.jpg Stage 22 image 002.jpg Stage 22 image 003.jpg Stage 22 image 004.jpg Stage 22 image 005.jpg Stage 22 image 006.jpg Stage 22 image 007.jpg
A1 A2 A3 A4 A5 A6 A7
Stage 22 image 008.jpg Stage 22 image 009.jpg Stage 22 image 010.jpg Stage 22 image 011.jpg Stage 22 image 012.jpg Stage 22 image 013.jpg Stage 22 image 014.jpg
B1 B2 B3 B4 B5 B6 B7
Stage 22 image 015.jpg Stage 22 image 016.jpg Stage 22 image 017.jpg Stage 22 image 018.jpg Stage 22 image 019.jpg Stage 22 image 020.jpg Stage 22 image 021.jpg
C1 C2 C3 C4 C5 C6 C7
Stage 22 image 022.jpg Stage 22 image 023.jpg Stage 22 image 024.jpg Stage 22 image 025.jpg Stage 22 image 026.jpg Stage 22 image 027.jpg Stage 22 image 028.jpg
D1 D2 D3 D4 D5 D6 D7
Stage 22 image 029.jpg Stage 22 image 030.jpg Stage 22 image 031.jpg Stage 22 image 032.jpg Stage 22 image 033.jpg Stage 22 image 034.jpg Stage 22 image 035.jpg
E1 E2 E3 E4 E5 E6 E7
Stage 22 image 036.jpg Stage 22 image 037.jpg Stage 22 image 038.jpg Stage 22 image 039.jpg Stage 22 image 040.jpg Stage 22 image 041.jpg Stage 22 image 042.jpg
F1 F2 F3 F4 F5 F6 F7
Stage 22 image 043.jpg Stage 22 image 044.jpg Stage 22 image 045.jpg Stage 22 image 046.jpg Stage 22 image 047.jpg Stage 22 image 048.jpg Stage 22 image 049.jpg
G1 G2 G3 G4 G5 G6 G7

Week 8 - Stage 23

Embryo Stage 23 MRI Movies
Stage23 MRI 3D01 icon.jpg
 ‎‎Embryo Surface
Page | Play
Stage23 MRI 3D02 icon.jpg
 ‎‎Embryo CNS
Page | Play
Stage23 MRI S02 icon.jpg
 ‎‎Sagittal Embryo
Page | Play
Stage23 MRI S04 icon.jpg
 ‎‎Sagittal GIT
Page | Play
Stage23 MRI T01 icon.jpg
 ‎‎Trans. Embryo
Page | Play
Stage23 MRI 3D04 icon.jpg
 ‎‎Embryo Surface
Page | Play
Stage23 MRI C01 icon.jpg
 ‎‎Coronal Embryo
Page | Play
Stage23 MRI S01 icon.jpg
 ‎‎Sagittal Head
Page | Play
Stage 23 Links  
Stage 23 MRI Movies: Surface | Central Nervous System | CNS (labeled) | Sagittal | Sagittal (labeled) | Transverse | Transverse (labeled) | Coronal | Sagittal Head (labeled) | Sagittal GIT (labeled) | Carnegie stage 23


Week: 1 2 3 4 5 6 7 8
Carnegie stage: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23


Stage 23 Links: Week 8 | System Development | Lecture - Limb | Lecture - Head Development | Lecture - Sensory | Science Practical - Head | Science Practical - Sensory | Science Practical - Urogenital | Historic - Skull Development | Carnegie Embryos | Madrid Embryos | Category:Carnegie Stage 23 | Next Fetal Development
  Historic Papers: 1954 Stage 19-23



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Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8