The connecting stalk, or body stalk, is an embryonic structure that is formed by the third week of

development Development or developing may refer to: Arts *Development (music), the process by which thematic material is reshaped * Photographic development *Filmmaking, development phase, including finance and budgeting * Development hell, when a proje ...

and connects the

embryo An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sp ...

to its shell of

trophoblast The trophoblast (from Greek language, Greek : to feed; and : germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after Human fertilization, fertilization in humans. They provide nutrients to the embryo an ...

s. The connecting stalk is derived from the extraembryonic mesoderm. Initially it lies caudally to the trilaminar germ disc, but, with subsequent embryonic folding, the body stalk assume a more ventral position. Progressive expansion of the

amnion The amnion (: amnions or amnia) is a membrane that closely covers human and various other embryos when they first form. It fills with amniotic fluid, which causes the amnion to expand and become the amniotic sac that provides a protective envir ...

from the umbilical ring (surrounding the roots of the

vitelline duct In the human embryo, the vitelline duct, also known as the vitellointestinal duct, the yolk stalk, the omphaloenteric duct, or the omphalomesenteric duct, is a long narrow tube that joins the yolk sac to the midgut lumen of the developing fetus. ...

and connecting stalk) creates a tube with a covering of amniotic membrane with

allantois The allantois ( ; : allantoides or allantoises) is one of the extraembryonic membranes arising from the yolk sac. It is a hollow sac-like structure filled with clear fluid that forms part of the developing conceptus in an amniote that helps the ...

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 In Placentalia, placental mammals, the umbilical cord (also called the navel string, birth cord or ''funiculus umbilicalis'') is a conduit between the developing embryo or fetus and the placenta. During prenatal development, the umbilical cord i ...

that connects the embryo and the

placenta The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...

.Larsen's Embryology, 5th edition, p138. The root of the connecting stalk contains the

as a diverticulum of hindgut

endoderm Endoderm is the innermost of the three primary germ layers in the very early embryo. The other two layers are the ectoderm (outside layer) and mesoderm (middle layer). Cells migrating inward along the archenteron form the inner layer of the gastr ...

along with umbilical vessels. Anomalies are usually referred to as ''body stalk anomalies'' and occur in approximately 1 in 15,000 births. They are due to defects in the formation of the cephalic, caudal, and lateral embryonic body folds, that result in a reduced or absent umbilical cord.

Additional images

File:Gray17.png, Human embryo—length, 2 mm. Dorsal view, with the amnion laid open. X 30. File:Gray22.png, Human embryo of 2.6 mm. File:Gray31.png, Model of human embryo 1.3 mm. long. File:Gray32.png, Section through ovum imbedded in the uterine decidua. File:Gray40.png, Embryo between eighteen and twenty-one days.

References

External links

* Embryology {{developmental-biology-stub