2010 BGD Practical 6 - Week 3: Difference between revisions

Revision as of 15:27, 13 May 2010

Introduction

Introduction

Key events of human development during the third week (week 3) following fertilization or Clinical week 5 (LMP). Note that during this time the conceptus cells not contributing to the embryo are contributing to placental membranes and the early placenta.

Somitogenesis

The later migration of cells forms the mesoderm germ layer. An embryonic connective tissue (mesenchyme) which forms nearly all the connective tissues of the body (the head is different). Somitogenesis is when part of this layer segments during week 3 to form balls of mesoderm called somites.

Neurogenesis

The remaining cells that do not migrate from the epiblast layer remain and form the ectoderm. An epithelial layer of cells which contributes all neural (brain, spinal cord, peripheral nervous system) and the external epithelium (surface layer of the skin) of the embryo. Neurogenesis begins towards the end of week 3, when the neural tissues separate from this germ cell layer.

Folding

There are two major folding processes that take place during this time.

Folding of the ecoderm will form a neural groove, then closing to form a neural tube, separating the neural ectoderm from the embryo surface ectoderm.

Folding of the whole embryonic disc ventrally, separates the endoderm to form the epithelial lining of the gut.

Embryo Stages and Events

Day	Stage	Event
15
16	Stage 7	Primitive node (Hensen's node, primitive knot) The small circular region located at the cranial end of the primitive streak, where gastrulation occurs, and is a controller of this process. The second role is to act as an initial generator of the left-right (L-R) body axis.
17
18	Stage 8	Neural neurogenesis, neural groove and folds are first seen
19
20	Stage 9	Musculoskeletal somitogenesis, first somites form and continue to be added in sequence caudally Neural the three main divisions of the brain, which are not cerebral vesicles, can be distinguished while the neural groove is still completely open Neural Crest mesencephalic neural crest is visible PMID: 17848161
21		Heart cardiogenesis, week 3 begins as paired heart tubes.

Week 2 and 3 Movies


Implantation	Mesoderm	Chorionic Cavity	Amniotic Cavity	Week 3

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

2010 BGD: Lecture 1 | Lecture 2 | Practical 3 | Practical 6 | Practical 12

Cite this page: Hill, M.A. (2024, May 17) Embryology 2010 BGD Practical 6 - Week 3. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/2010_BGD_Practical_6_-_Week_3

What Links Here?

@@ Line 5: / Line 5: @@
 Key events of human development during the third week (week 3) following fertilization or Clinical week 5 (LMP). Note that during this time the conceptus cells not contributing to the embryo are contributing to placental membranes and the early placenta.
+==Somitogenesis==
+The later migration of cells forms the mesoderm germ layer. An embryonic connective tissue (mesenchyme) which forms nearly all the connective tissues of the body (the head is different). Somitogenesis is when part of this layer segments during week 3 to form balls of mesoderm called somites.
+==Neurogenesis==
+The remaining cells that do not migrate from the epiblast layer remain and form the ectoderm. An epithelial layer of cells which contributes all neural (brain, spinal cord, peripheral nervous system) and the external epithelium (surface layer of the skin) of the embryo. Neurogenesis begins towards the end of week 3, when the neural tissues separate from this germ cell layer.
+==Folding==
+There are two major folding processes that take place during this time.
+Folding of the ecoderm  will form a neural groove, then closing to form a neural tube, separating the neural ectoderm from the embryo surface ectoderm.
+Folding of the whole embryonic disc ventrally, separates the endoderm to form the epithelial lining of the gut.
+==Embryo Stages and Events==
 {| class="prettytable"
 | width= "50px" |'''Day'''