3D models of the early human umbilical vasculature.tif

3D models of the early human umbilical vasculature. (A) A Carnegie stage (CS)9 embryo with an attached connecting stalk (precursor to umbilical cord and feto-placental vasculature, yellow) with arterial vessels (red), which is earlier than previously thought (O'Rahilly and Müller, 1987). The human allantois is shown in cyan. The human allantois is a separate structure to the mouse allantois. The ‘allantois’ or ‘allantoic diverticulum’ in humans is a separate structure from the umbilical cord vessels and ‘feto–placental’ vessels that derive from the connecting stalk. The human allantois forms a singular extension from the hindgut, which exists temporarily between the two umbilical arteries. It regresses from the umbilical cord to connect the hindgut to the cloaca and eventually becomes the ‘urachus’ or ‘umbilical ligament’ (O'Rahilly and Müller 1987, Kruepunga et al. 2018). The connecting stalk is equivalent to the mouse allantois. (B) A CS11 embryo without a connecting stalk/early umbilical cord but containing arterial vessels near the umbilical-embryonic junction (yellow line). (C) A CS15 embryo, with arterial (red) and venous (green) vasculature and allantois (cyan) in the umbilical cord. Human embryo image stacks (CS9/CS11) taken from DREM Carnegie collection (The Virtual Human Embryo, 2019). High Resolution Episcopic Microscopy (HREM) CS15 stack came from Wellcome Trust DMDD project. 3D models were created using Amira software (Life & Biomedical Sciences version 2019.4, Thermo Fisher Scientific).