Spatial organization of extraorgan angioarchitectonics of the human placenta in normal conditions: A pilot morphological study using injection-corrosion methods

Abstract

In press

Background. Despite extensive research on the placenta, the spatial organization of its vascular bed, particularly the extraorgan compartment which influences fetal blood flow distribution and intraplacental hemodynamics, remains insufficiently understood. Elucidation of normal placental angioarchitectonics is essential for understanding the mechanisms of obstetric complications.

Aim. To investigate the features of the spatial organization of the extraorganic angioarchitecture of the normal human placenta.

Materials and Methods. The study was performed on 10 intact human placental specimens with attached umbilical cords obtained after physiological deliveries at 38–40 weeks of gestation. A polychrome injection technique using self-curing acrylic plastic ("Protakryl") was applied, followed by corrosion casting of the placental and umbilical cord vascular beds. The obtained casts were used for direct visual, topographic, and morphometric analysis and were documented by digital photography. Descriptive frequency analysis was used to summarize the observed anatomical variants. The study was a fragment of the research topic of the Department of Human Anatomy of Poltava State Medical University (Ukraine) with a state registration number 0125U002785.

Research Ethics. The study was performed on anonymized human placental specimens in accordance with the legislation of Ukraine, including Resolution of the Cabinet of Ministers of Ukraine No.999 of August 30, 2024, on the collection and use of human biological samples for research purposes.

Results. In the area of umbilical cord attachment, a short arterial anastomosis (Hyrtl's anastomosis) is often found between the umbilical arteries, which equalizes hemodynamic load and blood flow distribution in the initial segments of the arterial bed. First-order placental arteries course radially toward the periphery but lack strict topographic correspondence with veins at the same level: veins predominantly run centrally within the lobules, whereas arteries are located more laterally and often extend into adjacent cotyledons. The main vessels then transition into the vessels of anchoring villi – a transitional segment between the main bed and the hemomicrocirculatory network of the villous chorion – from which the axial vessels of stem villi arise for blood redistribution within the cotyledons.

Conclusions. The human placenta's extraorgan angioarchitectonics shows regular arterial/venous spatial organization with compensatory interarterial anastomoses at the cord insertion. Arterial and venous topography differs within lobules. Anchoring villus vessels bridge the main and microcirculatory beds. These preliminary results provide a descriptive morphological basis for future studies of placental pathology, though confirmation on a larger sample is required.

Keywords: obstetrics, experimental medicine, placenta, blood vessels, arteriovenous anastomoses, angioarchitecture.