TissueDB/Tissues/Placental Tissue
Placental tissue is the vascular, disc-shaped organ that interfaces between maternal and fetal circulation. The umbilical arteries branch on entering it into "chorionic vessels", which divide into arterioles and distribute blood to the chorionic villi — the fetal component of the placenta — where capillary networks coalesce into the venules that merge to form the umbilical vein.[1] In simulation the placenta plays an unusual role: it is the substrate rather than the target. Human and bovine placentas are used as ex-vivo tissue for microvascular anastomosis and cerebral bypass training, where "placental vessels provide a high degree of dimensional agreement with certain human brain vessels and can be perfused to model circulation".[2] The published models cited below use the tissue itself and describe no substitute for it, so no simulant material is listed.
Things to Look Out For
Placental arteries are not cerebral arteries under the microscope. The published comparison of bypass training models lists as a limitation of the placental model that, "unlike cerebral arteries, placental arteries lack internal elastic lamina and elastic fibers in the media". The match is dimensional, not histological — a suture bite that behaves correctly here need not behave the same in a vessel with an elastic lamina.[2]
There is no circulation unless you build one. The same comparison records "lack of circulation" among the placental model's drawbacks. Perfusion is possible — the tissue can "be perfused to model circulation" — but it is a setup step, not a property of the tissue as it arrives.[2]
Getting hold of it is the hard part, and it is not the same problem in every country. The recorded obstacles are "local regulations may reduce or prohibit use of human placenta for science", "difficult to acquire bovine placenta", and a "burdensome tissue preparation process". A model that works in one institution can be unavailable in another for reasons that have nothing to do with the tissue.[2]
It carries an infection risk, and that risk is why several groups chose something else. Infection risk is listed against the placental model, and one team states plainly that it preferred chicken and turkey wings "because they do not present an infection risk, are inexpensive, can be reused for an extended period, and do not involve ethical concerns".[2][3]
It reproduces the vessel, not the operation. "Placental models do not recapitulate spatial components of" cerebral bypass surgery "such as the depth and width of the surgical field". Training that depends on working down a narrow corridor needs something else to supply the corridor.[2]
- Umbilical Cord — spans from the fetal umbilicus to the centre of the placenta; its two arteries and one vein are continuous with the placental circulation[1]
- Blood Vessel — the chorionic vessels and fetal surface arteries are what the microsurgical models actually use
- Brain — the tissue those placental vessels stand in for, in cerebral bypass training
Simulation Requirements
| Domain | Requirements |
|---|---|
| Visual | The recorded fidelity claim is dimensional and vascular, not visual in the ordinary sense: "strong dimensional agreement between placental vessel and specific human brain vessel correlates", and fetal surface arteries from human placentas "have been used to mimic side-to-side ACA-ACA bypass".[2] Neither paper describes a placental-tissue substitute, so no appearance target for one is given. |
| Tactile | Not measured. The nearest statement either paper makes is that "fresh human and bovine placentas are also highly suitable materials due to tissue compatibility and the possibility of numerous microanastomoses" — a suitability judgement rather than a measurement, and the same authors chose poultry wings instead.[3] Neither paper reports a stiffness, burst-pressure or suture-hold figure for placental tissue. |
References
[edit source]- ↑ 1.0 1.1 Brahmandam G, Lipsett BJ. "Anatomy, Abdomen and Pelvis: Umbilical Cord." StatPearls. StatPearls Publishing, Treasure Island (FL). NCBI Bookshelf NBK557389.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Cikla U, Rowley P, Jennings Simoes EL, Ozaydin B, Goodman SL, Avci E, Baskaya MK, Patel NJ. "Grapefruit Training Model for Distal Anterior Cerebral Artery Side-to-Side Bypass." World Neurosurgery 2020;138:39–51. DOI: 10.1016/j.wneu.2020.02.107. PMID: 32109640.
- ↑ 3.0 3.1 Akdag BA, Akdag B, Ikizoglu E, Husemoglu B, Kizmazoglu C, Aydin HE, Ozer E. A Novel Training Model for Superficial Temporal Artery–Middle Cerebral Artery Anastomosis Using Microsurgical Techniques. World Neurosurgery 2024;190:e665–e674. DOI 10.1016/j.wneu.2024.07.200. PMID 39098505.