connecting stalk

{{Short description|Embryonic structure}}

{{Infobox embryology

| Name = Connecting stalk

| Latin = pedunculus connectans

| Image = Gray27.png

| Caption = Diagram showing the expansion of amnion and delimitation of the umbilical cord

| Image2 = Gray21.png

| Caption2 = Section through the embryo

| precursor = Extraembryonic mesoderm

}}

The connecting stalk, or body stalk, is an embryonic structure that is formed by the third week of development and connects the embryo to its shell of trophoblasts. The connecting stalk is derived from the extraembryonic mesoderm.{{Cite book |last1=Schoenwolf |first1=Gary C. |url=https://books.google.com/books?id=XQuqBAAAQBAJ |title=Larsen's Human Embryology: with STUDENT CONSULT Online Access |last2=Bleyl |first2=Steven B. |last3=Brauer |first3=Philip R. |last4=Francis-West |first4=Philippa H. |date=2012-05-07 |publisher=Elsevier Health Sciences |isbn=9781455727919 |page=57 |language=en}} Initially it lies caudally to the trilaminar germ disc, but, with subsequent embryonic folding, the body stalk assume a more ventral position.{{Cite journal |last1=Heil |first1=Jenna |last2=Bordoni |first2=Bruno |date=2022-04-21 |title=Embryology, Umbilical Cord |url=https://www.statpearls.com/articlelibrary/viewarticle/32458/ |journal=StatPearls |pmid=32491422 |language=en}} Progressive expansion of the amnion from the umbilical ring (surrounding the roots of the vitelline duct and connecting stalk) creates a tube with a covering of amniotic membrane with allantois and umbilical vessels as its content and mesoderm of the connecting stalk as the ground substance. This extraembryonic mesodermal ground substance forms the future Wharton's jelly. The amniotic membrane and its contents form the umbilical cord that connects the embryo and the placenta.{{cite book |last1=Sadler |first1=T. W. |title=Langman's medical embryology. |date=2010 |publisher=Lippincott William & Wilkins |location=Philadelphia |isbn=9780781790697 |pages=64–65 |edition=11th}}Larsen's Embryology, 5th edition, p138.

The root of the connecting stalk contains the allantois as a diverticulum of hindgut endoderm along with umbilical vessels.{{cite book |last1=Larsen |first1=William J. |title=Human embryology |date=2001 |publisher=Churchill Livingstone |location=New York |isbn=0443065837 |page=138 |edition=3rd}}

Anomalies are usually referred to as body stalk anomalies and occur in approximately 1 in 15,000 births.{{cite book|author=Asim Kurjak|title=Donald School Textbook of Transvaginal Sonography|url=https://books.google.com/books?id=xYuIWZE1Se4C&pg=PA28|date=30 June 2013|publisher=JP Medical Ltd|isbn=978-93-5090-473-2|pages=28}} They are due to defects in the formation of the cephalic, caudal, and lateral embryonic body folds,{{cite book|author1=Diana W. Bianchi|author2=Timothy M. Crombleholme|author3=Mary E. D'Alton|title=Fetology: Diagnosis & Management of the Fetal Patient|url=https://books.google.com/books?id=53Csy-mr1bsC|date=1 January 2000|publisher=McGraw Hill Professional|isbn=978-0-8385-2570-8}} that result in a reduced or absent umbilical cord.{{cite journal |last1=Kocherla |first1=K |last2=Kumari |first2=V |last3=Kocherla |first3=PR |title=Prenatal diagnosis of body stalk complex: A rare entity and review of literature. |journal=The Indian Journal of Radiology & Imaging |date=January 2015 |volume=25 |issue=1 |pages=67–70 |doi=10.4103/0971-3026.150162 |pmid=25709170|pmc=4329692 |doi-access=free }}