Beginnings, Growth and Development - Frequently Asked QuestionsOK, these are questions that have come up time and again. Try the following first...before you leap to your email.
1. I would always suggest that you initially look at the lecture/lab handouts and slides for the answer.
2. Next go to your trusty embryology Textbook, which will definitely have your answer!
3. Still stuck? Search the online NCBI Bookshelf or Developmental Biology (Gilbert).
If it is simply a term or definition you need then use the Glossary. The questions below are in no particular order.
Page Links: Introduction | What is Mesenchyme? | What are the embryonic origins of the layers in the GIT? | What does the Y chromosome SRY do? | What is a diverticulum? | What are the 3 paired ducts? | What are the main GIT embryological parts? | Do I need to know all the exact days? | What about endocrine heart, GIT and kidney? | Do I need to know GIT organ development? | Quick Lecture Links | Glossary
Mesenchyme is embryonic connective tissue. It is also used to describe the spread, unorganised cellular nature (mesenchymal) of this tissue. Mesenchyme is can be mesodermal or neural crest in origin.
The gastrointestinal tract (GIT) epithelial lining, including its glands, is endoderm in origin. It is surrounded connective tissue, muscle, blood vessels are splanchnic mesoderm in origin, which formed from the portion of lateral plate mesoderm closest to the endoderm and beneath the intraembryonic ceolom. The 2 neural plexuses muscularis mucosa (= Meissner) and myenteric (= Auerbach) are neural crest in origin.
SRY, Sex related Region on the Y chromosome, encodes a transcription factor that is expressed in support cells, sertoli cells, in the developing male gonad and leads to their differentiation and has several effects.
Sertoli cells then:
(See Molecular Biology of the Cell - Influence of Sry on gonad development.)
A diverticulum (Latin = by-road) is used to describe usually an epithelial blind tubular process, or sac/pouch in an organ or tissue. (This answer can also be found in the Glossary diverticulum)
The 3 paired ducts refers to the ducts that form during kidney and gonad differentiation.
The mesonephric ducts (= Wolffian) form first in association with the intermediate kidney (mesonephros) and connect to
the urogenital sinus region that will form the primitive bladder. These ducts form in both male and female embryos and a lateral branch from these ducts form
The nephric ducts that will eventually form the ureters, connecting the final kidney (metanephros) with the bladder. The paramesonephric ducts (= Müllerian) form beside (hence "para") the mesonephric ducts and their further development
is inhibited in the male, continues in the female to form the uterus. (See the Sexual Differentiation Practical- Internal Genitalia) The developing gastrointestinal tract (GIT) is generally divided into 3 main regions that are continuous with each other: foregut, midgut and
hindgut each forming different specific parts of the adult tract. Note that this describes the tract itself, not the associated
organs.
The foregut commences at the buccopharyngeal membrane (= oral, = stomedeal) as the pharynx and runs down behind the heart, ending at the
septum transversum. The midgut continues from the septum transversum and is initially a large ventral cavity in the embryo (continuous with the
yolk sac lying outside the embryo) and ends at the lower umbilical region. The hindgut continues down and ends at the cloacal membrane. This region also has a ventral portion, the allantois,
that forms a diverticulum into the connecting stalk. Note the foregut and hindgut both later are seperated (septated) into separate regions. See the GIT Practical- Fore-, Mid- Hind-) I hate these negative questions, tha always start with "do I need to know?" My answer would always be yes you do need to know, otherwise why would you be here?
But in this case, I will break my rule, at this point you do not need to know the exact day by day timings (a general understanding will do).
The point is to identify what is happening when in development, the sequence,
and eventually you can build a bigger picture of what is happening in the embryo/fetus at different times.
This is relevant when we start considering "critical periods" of development when maternal effects can have serious effects on specific systems and leave others relatively untouched.
These organs do have an endocrine role as well as their actual organ function. At this point just be aware that they have an endocrine
function, it is more important to understand the development of the specific endocrine organs I covered in the lecture: pineal, hypothalamus,
hypophysis, thyroid, parathyroid, pancreas, adrenal and gonad (covered again in sexual differentiation). It is more about the organ development and
developmental function, rather than the complete physiological function that should have been covered elsewhere.
(See the Lecture - Endocrine Gland Development)
Yes. Do I need to know.....
(See the Lecture - GIT Development)
Lecture - Embryology of the Gastro-Intestinal Tract (27 Jul 9-10am Clancy)
Lecture - Sexual Differentiation (30 Aug 9-10am Clancy)
Lecture - Endocrine Gland Development (24 Aug 9-10am Clancy)
Practical - Embryology of the Gastro-Intestinal Tract (25, 27 28 Jul G2/G4 Wallace Wurth)
Practical - Embryology of the face and ear (10 11 12 Aug G2/G4 Wallace Wurth)
Practical - Sexual Differentiation (31 Aug, 1 2 Sept G2/G4 Wallace Wurth)
Urogenital Development notes look at both Kidney and Genital development. Endocrine Development look at gonad and Hypothalamus/Pituitary notes. Oogenesis mainly covers mature ovary. Spermatogenesis mainly covers mature ovary. These are movies shown in the Lecure slides. Note that movies require quicktime to be installed on your computer. Urogenital Movies link takes you to a page with movies shown in the Lecture. A
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What is a diverticulum?
What are the 3 paired ducts?
What are the main GIT embryological parts?
Do I need to know all the exact days?
What about endocrine heart, GIT and kidney?
Do I need to know GIT organ development?
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This page is a brief coverage of some FAQs that have come up in Lecture or Practical or Expert Tutorial or by Email.
Note: Inclusion of an FAQ on this page does not relate to whether or not the material will be examined or assessed! (I am assuming that you really want to know the answer)
Please contact me with your question (after you have followed my rules in the introduction) by email to have an answer posted here.
These notes and linked materials have been prepared for Educational purposes only.
Please email Dr Mark Hill if you wish to make a comment about this current project.