endo-view עברית
Human Explore Simulations How we know Features About

Method and sources

How we know

Endo-View tries to show the body as it is. This page says how: what the three labels mean, where the numbers and the models come from, and what has not been checked yet.

Three labels, on every number

Measured means the number comes from studies that measured it, such as the length of a sperm cell or the acidity of the vagina. Estimate means a typical figure that varies a lot between people, such as how many sperm arrive. Drawn means it is how we chose to show something, not a measurement: most colours, and the shape of anything the research does not fix.

Where the research gives a range, we show the range. The labels are part of the page, not a footnote, and each one says its word as well as showing a colour.

True scale, slowed down to be seen

Sizes are real, with a scale bar wherever scale matters. Motion is slowed so that you can see it, and the speed control can always show it at real speed. Under a microscope most cells are almost transparent, so their colours are drawn, and the site says so.

Where the numbers come from

Every figure comes from the medical literature: studies, reference limits (such as the World Health Organization's for semen) and standard embryology textbooks. The sources are listed below, and in the About window of the app. Fuller notes on the body and the journey are kept with the project.

Where the models come from

The body is built from openly licensed models, credited and shared under the same licences: Z-Anatomy (the skeleton, muscles, organs, vessels and nerves, itself based on BodyParts3D), the Human Reference Atlas by HuBMAP (the female organs), MakeHuman (the female skin and hair) and Human Atlas (the body's systems and their descriptions). We adapt them for the web, and some parts we make ourselves: the layer of fat, the pale tendons, the underwear, and the anatomy the open model leaves out, which is marked "Modelled by Endo-View" on its card. The shape of the lower jaw comes from a CT scan of the Visible Human Project, courtesy of the U.S. National Library of Medicine.

Everything in the journey to life, the cells, the egg and the embryo, is drawn in code. Our aim is that in the end every model is ours: high quality, realistic and anatomically correct. Until a replacement meets that bar, the open part stays, with its credit.

Has an expert checked it?

Not yet. Before the site goes public, a doctor or a biology teacher is asked to check the facts, chapter by chapter. Until then every chapter says so at the top of its card: "Facts not yet checked by an expert". When a chapter has been checked, the card says who checked it (by name only if they agree) and when, and if we change its words afterwards it says that too.

Found a mistake?

Please tell us. Use "Report a problem" on a part's card, at the end of a chapter's card, or in the About window. You do not need an account.

What this is not

Endo-View is for learning. It is not medical advice, a diagnosis or a treatment plan. Bodies differ a great deal, and many things are shown simplified. For questions about your health, fertility or pregnancy, talk to a doctor or midwife.

Sources

  1. World Health Organization. WHO laboratory manual for the examination and processing of human semen, 6th ed. Geneva, 2021.
  2. Suarez SS, Pacey AA. Sperm transport in the female reproductive tract. Human Reproduction Update 2006;12(1):23–37.
  3. Kunz G, et al. The dynamics of rapid sperm transport through the female genital tract. Human Reproduction 1996;11(3):627–632.
  4. Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to ovulation. New England Journal of Medicine 1995;333:1517–1521.
  5. Lishko PV, Botchkina IL, Kirichok Y. Progesterone activates the principal Ca²⁺ channel of human sperm. Nature 2011;471:387–391.
  6. Bianchi E, Doe B, Goulding D, Wright GJ. Juno is the egg Izumo receptor and is essential for mammalian fertilization. Nature 2014;508:483–487.
  7. Duncan FE, et al. The zinc spark is an inorganic signature of human egg activation. Scientific Reports 2016;6:24737.
  8. Moore KL, Persaud TVN, Torchia MG. The Developing Human: Clinically Oriented Embryology. Elsevier.
  9. Sadler TW. Langman's Medical Embryology. Wolters Kluwer.
  10. Female body (skin, eyes, eyebrows, eyelashes, hair): made with MakeHuman / MPFB (static.makehumancommunity.org/mpfb), MakeHuman system assets, CC0. Posed and fitted by Endo-View.
  11. Female anatomy: Kristen Browne and Heidi Schlehlein, Human Reference Atlas / HuBMAP, 3D Reference Organ Set for Female v1.5 (2023), CC BY 4.0, https://doi.org/10.48539/HBM352.BTSQ.586. Simplified for the web by Endo-View.
  12. Anatomy models: Z-Anatomy (z-anatomy.com, github.com/LluisV/Z-Anatomy), CC BY-SA 4.0, based on BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International. Simplified for the web by Endo-View; the simplified models are shared under the same licence.
  13. The body's fifteen systems, their descriptions, the first organ explanations, the exploded view's layout, and the ideas of search, show-only and views: Human Atlas by ashemag (github.com/ashemag/human-atlas), MIT License, © 2026 ashemag.
  14. Hardy K, Handyside AH, Winston RML. The human blastocyst: cell number, death and allocation during late preimplantation development in vitro. Development 1989;107:597–604.
  15. Wilcox AJ, Baird DD, Weinberg CR. Time of implantation of the conceptus and loss of pregnancy. New England Journal of Medicine 1999;340:1796–1799.
  16. Wilcox AJ, et al. Incidence of early loss of pregnancy. New England Journal of Medicine 1988;319:189–194.
  17. Fox CA, Meldrum SJ, Watson BW. Continuous measurement by radio-telemetry of vaginal pH during human coitus. Journal of Reproduction and Fertility 1973;33:69–75.
  18. Yudin AI, Hanson FW, Katz DF. Human cervical mucus and its interaction with sperm: a fine-structural view. Biology of Reproduction 1989;40(3):661–671.
  19. Williams M, et al. Sperm numbers and distribution within the human fallopian tube around ovulation. Human Reproduction 1993;8(12):2019–2026.
  20. Avella MA, Baibakov B, Dean J. A single domain of the ZP2 zona pellucida protein mediates gamete recognition in mice and humans. Journal of Cell Biology 2014;205(6):801–809.
  21. Burkart AD, et al. Ovastacin, a cortical granule protease, cleaves ZP2 in the zona pellucida to prevent polyspermy. Journal of Cell Biology 2012;197(1):37–44.
  22. Bayram A, et al. Time-lapse morphokinetics of human embryos. Human Reproduction Open 2024;hoae059.
  23. Burton GJ, Jauniaux E, et al. The early placental circulation and onset of maternal blood flow. Reviews, 2016–2024.
  24. BioNumbers (Harvard): diameter of a living human neutrophil, BNID 100510.
  25. Curcio CA, et al. Human photoreceptor topography. Journal of Comparative Neurology 1990;292:497–523.
  26. Ochs M, et al. The number of alveoli in the human lung. American Journal of Respiratory and Critical Care Medicine 2004;169:120–124.
  27. Azevedo FAC, et al. Equal numbers of neuronal and nonneuronal cells make the human brain an isometrically scaled-up primate brain. Journal of Comparative Neurology 2009;513:532–541.
  28. Feldesman MR, Kleckner JG, Lundy JK. Femur/stature ratio and estimates of stature in mid- and late-Pleistocene fossil hominids. American Journal of Physical Anthropology 1990;83:359–372.
  29. Tacchino RM. Bowel length: measurement, predictors, and impact on bariatric and metabolic surgery. Surgery for Obesity and Related Diseases 2015;11(2):328–334.
  30. Wallace WHB, Kelsey TW. Human ovarian reserve from conception to the menopause. PLoS ONE 2010;5(1):e8772.
  31. Robinson HP, Fleming JEE. A critical evaluation of sonar crown-rump length measurements. British Journal of Obstetrics and Gynaecology 1975;82:702–710.
  32. Doubilet PM, Benson CB. Embryonic heart rate in the early first trimester: what rate is normal? Journal of Ultrasound in Medicine 1995;14:431–434.
  33. Cunningham FG, et al. Williams Obstetrics. McGraw Hill.
  34. Hadlock FP, Harrist RB, Martinez-Poyer J. In utero analysis of fetal growth: a sonographic weight standard. Radiology 1991;181:129–133.
  35. World Health Organization. WHO recommendations: intrapartum care for a positive childbirth experience. Geneva, 2018.
  36. WHO Multicentre Growth Reference Study Group. WHO Child Growth Standards: length/height-for-age, weight-for-age. Geneva, 2006.
  37. Betran AP, Ye J, Moller AB, Souza JP, Zhang J. Trends and projections of caesarean section rates: global and regional estimates. BMJ Global Health 2021;6:e005671.
  38. Streeter DD Jr, Spotnitz HM, Patel DP, Ross J Jr, Sonnenblick EH. Fiber orientation in the canine left ventricle during diastole and systole. Circulation Research 1969;24:339–347.
  39. Olivetti G, et al. Aging, cardiac hypertrophy and ischemic cardiomyopathy do not affect the proportion of mononucleated and multinucleated myocytes in the human heart. Journal of Molecular and Cellular Cardiology 1996;28:1463–1477.
  40. Bergmann O, et al. Evidence for cardiomyocyte renewal in humans. Science 2009;324:98–102.
  41. Strauss M, Hofhaus G, Schröder RR, Kühlbrandt W. Dimer ribbons of ATP synthase shape the inner mitochondrial membrane. EMBO Journal 2008;27:1154–1160.
  42. Davies KM, et al. Macromolecular organization of ATP synthase and complex I in whole mitochondria. PNAS 2011;108:14121–14126.
  43. Kukat C, et al. Super-resolution microscopy reveals that mammalian mitochondrial nucleoids have a uniform size and frequently contain a single copy of mtDNA. PNAS 2011;108:13534–13539.
  44. Anderson S, et al. Sequence and organization of the human mitochondrial genome. Nature 1981;290:457–465.
  45. Neubauer S. The failing heart — an engine out of fuel. New England Journal of Medicine 2007;356:1140–1151.
  46. ICRP. Basic anatomical and physiological data for use in radiological protection: reference values. ICRP Publication 89. Annals of the ICRP 2002;32(3–4).
  47. Kawel-Boehm N, et al. Reference ranges ("normal values") for cardiovascular magnetic resonance in adults and children: 2020 update. Journal of Cardiovascular Magnetic Resonance 2020;22:87.
  48. Quer G, et al. Inter- and intraindividual variability in daily resting heart rate and its associations with age, sex, sleep, BMI, and time of year. PLoS ONE 2020;15(2):e0227709.
  49. Molina DK, DiMaio VJM. Normal organ weights in men (2012;33:362–367) and in women (2015;36:182–187). American Journal of Forensic Medicine and Pathology.
  50. Glodny B, et al. Normal kidney size and its influencing factors: a 64-slice MDCT study of 1,040 asymptomatic patients. BMC Urology 2009;9:19.
  51. Bertram JF, Douglas-Denton RN, Diouf B, Hughson MD, Hoy WE. Human nephron number: implications for health and disease. Pediatric Nephrology 2011;26:1529–1533.
  52. National Institute of Diabetes and Digestive and Kidney Diseases. Your kidneys and how they work; The urinary tract and how it works. niddk.nih.gov.
  53. Dekaban AS, Sadowsky D. Changes in brain weights during the span of human life. Annals of Neurology 1978;4:345–356.
  54. Raichle ME, Gusnard DA. Appraising the brain's energy budget. PNAS 2002;99:10237–10239.
  55. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer.
  56. Standring S (ed.). Gray's Anatomy: The Anatomical Basis of Clinical Practice, 42nd ed. Elsevier, 2020.
  57. Hall JE, Hall ME. Guyton and Hall Textbook of Medical Physiology, 14th ed. Elsevier, 2021.
  58. StatPearls: Physiology, Accommodation (NBK580484) and Anatomy, Head and Neck, Eye Lens (NBK589657). National Library of Medicine, ncbi.nlm.nih.gov/books.
  59. Helander HF, Fändriks L. Surface area of the digestive tract – revisited. Scandinavian Journal of Gastroenterology 2014;49(6):681–689.
  60. Sender R, Fuchs S, Milo R. Revised estimates for the number of human and bacteria cells in the body. PLoS Biology 2016;14(8):e1002533.
  61. Hounnou G, Destrieux C, Desmé J, Bertrand P, Velut S. Anatomical study of the length of the human intestine. Surgical and Radiologic Anatomy 2002;24:290–294.
  62. Hosseinpour M, Behdad A. Evaluation of small bowel measurement in alive patients. Surgical and Radiologic Anatomy 2008;30:653–655.

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