Development of the mammalian embryonic vascular system — interactive 3D model

Development of the mammalian embryonic vascular system — interactive 3D model

This is an interactive teaching model of how the mammalian cardiovascular system develops, from the first blood islands to the circulatory changes at birth. It is written for veterinary and biomedical students and their teachers. The dog is the reference species; switching to pig, ruminant (bovine) or horse shows where the outcome differs. The model is a single HTML file that runs in any modern web browser, with no installation.

The model has four linked views.

• Embryo (3D): five stages, from vasculogenesis through the heart tube and looping, remodelling of the arteries and veins, and the fetal circulation, to the transition at birth and the adult remnants. Stages are timed in dog days of gestation and crown–rump length. The embryo body is translucent, so the vessels, heart, liver, lungs, yolk sac, placenta and umbilical cord are visible. Vessels form, fuse, regress and become ligaments in their developmental order. Blood-flow particles are coloured by oxygen saturation, and a species switch shows differences in the branching of the aortic arch and in the azygos system.
• Heart 3D: the heart develops from the straight tube through dextral looping and ballooning of the chambers to the four-chambered heart, and beats throughout. Two cut-away views open it: a frontal cut, in the same plane as the heart section, shows the cavities, septa, wall thickness and the flap valve of the foramen ovale; a cut through the arterial roots shows the aortic and pulmonary valves.
• Heart section (2D): an animated frontal section whose chamber outlines are slices of the 3D heart. It shows the endocardial cushions, atrial septation (septum primum and secundum, and the foramen ovale as a flap valve), ventricular septation, the atrioventricular and semilunar valves, the division of the outflow tract and the great arteries. Blood flow follows atrial and ventricular systole, and the fetal shunts close at birth.
• Aortic arches (2D): a ventral schematic after Rathke's diagram. It shows the craniocaudal formation and regression of the pharyngeal arch arteries, colour-coded by their definitive derivatives, together with the recurrent laryngeal nerves, the heart and blood flow. It ends with the species-specific branching of the aortic arch.

Each stage carries an explanatory text with its molecular basis, species notes, clinical correlates and references. Labels sit outside the drawing with leader lines and can be hidden. The model can be rotated, panned and zoomed with a mouse, trackpad, touch or keyboard, and has settings for the heartbeat and rendering quality.

Scientific basis. Morphology follows standard veterinary and medical embryology texts: Hyttel, Sinowatz & Vejlsted 2010; McGeady et al. 2017; Noden & de Lahunta 1985; Sadler 2019. Adult anatomy follows Dyce, Sack & Wensing 2010, Evans & de Lahunta 2013 and König & Liebich 2020. Chamber formation follows Christoffels et al. 2000 and Moorman & Christoffels 2003, and fetal circulation Rudolph 2009. The full reference list is inside the model. The model is schematic and not to scale; dog timings and vessel calibres are approximate.

Authorship. Scientific content, design decisions and validation by the author; code generated with AI assistance (Claude, Anthropic) under the author's direction.

Licensing. Scientific and pedagogical content: CC BY-NC-SA 4.0. Source code: MIT License. The three.js library (MIT) is loaded from a CDN, so an internet connection is needed when the file is opened. The Egas Moniz logotype is excluded from both licences.

Version 1.1, 2 October 2026.
SHA-256: 49ad91bbfde22040efd28e8bf8e52068ac6203e566f7cf06d83af1dbfa232ab0