BGDA Practical 7 - Week 8: Difference between revisions
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===Gastrointestinal Tract=== | ===Gastrointestinal Tract=== | ||
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| | | [[File:Stage_22_image_203.jpg|400px]] | ||
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| The gastrointestinal midgut remains herniated outside of the ventral body wall. | | The gastrointestinal midgut remains herniated outside of the ventral body wall. | ||
* midgut continues to elongate during this period. | * midgut continues to elongate during this period. | ||
* midgut will be enclosed by the growing body wall during early fetal period. | * midgut will be enclosed by the growing body wall during early fetal period. | ||
| {{Gastrointestinal stage 22 movie}} | |||
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Revision as of 08:44, 19 May 2014
Introduction
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.
Head
Oral Cavity Region
Neural
Cortex development commences
choroid plexus
Note
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Body
Lungs, thymus, musculoskeletal. | vertebral column, spinal cord. |
Limbs
- Limb upper and lower limbs rotate in different directions (upper limb dorsally, lower limb ventrally)
- see also Adult dermatomes
Gastrointestinal Tract
The gastrointestinal midgut remains herniated outside of the ventral body wall.
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Extra-embryonic Coelom
- Chorionic cavity is now lost by fusion with the expanding amniotic cavity.
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.
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Critical Periods
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. |
Detailed Week by Week
The following information is a detailed timeline of embryonic development between week 3 to 8 and content does not form part of the current practical class.
Embryo Stages and Events
Event | ||
Stage 20 |
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 | |
Gastrointestinal Tract anal (cloacal) membrane perforates | ||
Stage 21 |
Neural - cortical plate appears in the area of future insula[2] Limb upper and lower limbs rotate Intraembryonic Coelom pericardioperitoneal canals close | |
Stage 22 | 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] | |
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) | ||
Stage 23 | 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. |
References
Week 8 - Stage 22 sections
These sections provide an overview of the internal structures now present within the embryo by the end of the embryonic period.
Labeled
A1L | A2L | A3L | A4L | A5L | A6L | A7L |
B1L | B2L | B3L | B4L | B5L | B6L | B7L |
C1L | C2L | C3L | C4L | C5L | C6L | C7L |
D1L | D2L | D3L | D4L | D5L | D6L | D7L |
E1L | E2L | E3L | E4L | E5L | E6L | E7L |
F1L | F2L | F3L | F4L | F5L | F6L | F7L |
G1L | G2L | G3L | G4L | G5L | G6L | G7L |
Unlabeled
A1 | A2 | A3 | A4 | A5 | A6 | A7 |
B1 | B2 | B3 | B4 | B5 | B6 | B7 |
C1 | C2 | C3 | C4 | C5 | C6 | C7 |
D1 | D2 | D3 | D4 | D5 | D6 | D7 |
E1 | E2 | E3 | E4 | E5 | E6 | E7 |
F1 | F2 | F3 | F4 | F5 | F6 | F7 |
G1 | G2 | G3 | G4 | G5 | G6 | G7 |
Practical 6: Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 |