# Check — Developmental Anatomy (Foundations, lecture 2 of 4)

Checked 2026-10-19. 54 claims checked; 10 corrected; 4 softened or removed.

Length 2137 → 1998 words (budget 2000, per the task's override of the brief's ±5%). Cuts were connective tissue only; every deck objective, figure, name and quotation is still present. Markup intact after edits: 15 `##` slides (one per beat), two `? ` paragraphs, two `> ` paragraphs, no lists, no parentheses or slashes, no `[+]`/`[fixed]` markers left (22 resolved), lecturer not named anywhere in the narration (pronoun "her" and "the course director" / "the lecturer" only). Script parses cleanly with the `_segment.py` paragraph logic.

## Corrections (script changed)
- Slide 2 (Establishing a shared lexicon): the tiger quotation was attributed to "a modern commentary on Aristotle"; the deck cites only "[3]". Source found: Stanford Encyclopedia of Philosophy, "Aristotle's Metaphysics" (S. Marc Cohen and C. D. C. Reeve), §7 "Substance and Essence", which opens "It is important to remember that for Aristotle, one defines things, not words…" Attribution now names the SEP entry. Wording of the quote (trimmed to under 40 words) matches the entry. Source: https://plato.stanford.edu/entries/aristotle-metaphysics/ (not the "Aristotle's Logic" entry, which was checked and does not contain it).
- Slide 5 (Eight embryos in a row): the plate described (fish, salamander, tortoise, chicken, pig, cow, rabbit, human; three rows) is Haeckel's *Anthropogenie* (1874) plates 4–5, usually reproduced as the single eight-column Romanes 1892 copy. Haeckel is documented to have exaggerated the early-stage likeness (Richardson et al. 1997; Wikipedia: drawings "often overemphasized similarities"). Added one hedged caution sentence (artist unnamed, since the deck's slide 7 is image-only and the writer inferred the image), and removed "The deck let that question sit in the room." Sources: https://ncse.ngo/node/6301 ; https://en.wikipedia.org/wiki/Haeckel%27s_embryos ; https://www.the-scientist.com/embryonic-evolution-through-ernst-haeckels-eyes-31585
- Slide 8 (Far more alike than different): "99.9 percent … identical" (deck) is the single-nucleotide figure; NHGRI's current fact sheet puts any two genomes at ~99.6% identical / ~0.4% different once insertions, deletions and structural variants are counted (~27 million nucleotides). Script now says "Letter for letter … 99.9 percent … counting insertions, deletions and larger rearrangements, nearer 99.6." Source: https://www.genome.gov/about-genomics/educational-resources/fact-sheets/human-genomic-variation
- Slide 8: "Nearly all human variation is in just 12 million base pairs" (deck) + writer's "That is roughly 3 million letters between any two people [+]". The deck's number has no identifiable source; the nearest established figure is HapMap's "on the order of ten million" common SNPs across the human population, which is a population-wide catalogue, not a two-person difference. A single genome differs from the reference at 4.1–5.0 million sites (1000 Genomes 2015) / ~5 million SNVs (NHGRI). Reworded: the 12 million "are not the gap between two people but the order of the common variant sites catalogued across the whole population; one person differs from the reference genome at about 4 to 5 million of them." The "3 million letters" sentence was removed. Sources: https://embryo.asu.edu/pages/international-hapmap-project-2002-2016 ; https://orca.cardiff.ac.uk/84393/1/1006.pdf (1000 Genomes, Nature 2015, "4.1 million to 5.0 million sites") ; https://www.genome.gov/about-genomics/educational-resources/fact-sheets/human-genomic-variation
- Slide 8: X chromosome "roughly 800 protein-coding genes [+]" → "roughly 900" (NHGRI ~900; MedlinePlus "900 to 1,400"; Wikipedia ~800). Y "fewer than 100 [+]" → "a few dozen by most counts" (NHGRI ~55; Wikipedia 106 including repeats, ~42 distinct protein-coding; MedlinePlus's older "70 to 200" is the outlier). Sources: https://www.genome.gov/es/about-genomics/fact-sheets/hoja-de-datos-del-cromosoma-y ; https://medlineplus.gov/genetics/chromosome/x/ ; https://medlineplus.gov/genetics/chromosome/y/ ; https://en.wikipedia.org/wiki/Y_chromosome
- Slide 8: "the rest of that list is done by hormones acting on genes every human carries [+]" was wrong for "sperm": the Y carries the AZFa/b/c regions (USP9Y, DDX3Y, DAZ1–4 and others) required for spermatogenesis; deletions cause Y-chromosome infertility. Added "plus a cluster of genes needed to make sperm" and closed the metaphor with "It turns one page, and keeps a few of its own." SRY as the testis-determining gene verified. Sources: https://medlineplus.gov/genetics/chromosome/y/ ; https://en.wikipedia.org/wiki/Y_chromosome
- Slide 10 (Our genes are not a foregone conclusion): "The deck closes with a news item on wild frogs that reversed sex" — the deck's slide 14 is image-only, so what it shows cannot be verified from the source text. Rewritten as a stand-alone, checked example: Lambert et al., *PeerJ* 2019, found sex-reversed green frogs (*Rana clamitans*) in 12 of 16 populations (2–16% of individuals), in forest as well as suburban ponds. Also "In many amphibians, reptiles and fish … [+]" → "In many reptiles and fish, and some amphibians": temperature-dependent sex determination is characteristic of all crocodilians, many turtles and some teleosts; amphibians have genetic sex determination with temperature-induced sex reversal in some species. Sources: https://peerj.com/articles/6449 ; https://www.nationalgeographic.com/animals/article/frogs-reverse-sex-more-often-than-thought ; https://en.wikipedia.org/wiki/Temperature-dependent_sex_determination ; https://pmc.ncbi.nlm.nih.gov/articles/PMC11240705
- Slide 11 (Internal genital homologies): "Every adult carries small remnants [+]" → "Adults commonly carry small remnants." Remnants (appendix testis, prostatic utricle; Gartner's duct, epoophoron) are common, not universal. Source: https://en.wikipedia.org/wiki/Development_of_the_reproductive_system ; https://en.wikipedia.org/wiki/Paramesonephric_duct
- Slide 12 (External genital homologies and the shared floor): "served by the same nerves [+]" → "with the same sacral nerve supply." The superficial perineal muscles and external anal sphincter are pudendal (S2–S4); levator ani is supplied by direct S3–S4 branches, with a pudendal contribution that is debated (Barber 2002 found none; Grigorescu 2008 found pudendal branches in most specimens). "Same sacral nerve supply" is true across bodies without implying one nerve. Sources: https://en.wikipedia.org/wiki/Levator_ani ; https://www.kenhub.com/en/library/anatomy/bulbospongiosus-muscle ; https://www.kenhub.com/en/library/anatomy/ischiocavernosus-muscle
- Slide 13 (The messengers and the receivers): "In androgen insensitivity an X Y fetus … takes the path that needs no androgen [+]" → "In complete androgen insensitivity"; the partial form produces a range of external phenotypes. Source: https://medlineplus.gov/genetics/condition/androgen-insensitivity-syndrome/

## Verified (unchanged)
- Slide 1: the course director's teaching "emphasizes developmental patterns, evolutionary theory, inclusive care, and the translation of complex science" — matches source slide 2; the three objectives match source slide 3.
- Slide 3 (homo sapiens): *Homo* is Latin *homō*, "human of either sex"; Greek *homos* "same" is a different word. The deck's "Homo from Greek for 'Same' or Latin meaning 'Human'" is reported as the deck's framing and the script resolves it to Latin (the writer's `[+]`, verified). *Sapiens*: Latin "wise/knowing" (Wikipedia: "wise man"/"knowledgeable man"); the deck's "one who knows" is an acceptable gloss. Source: https://en.wikipedia.org/wiki/Homo_sapiens
- Slide 4 (Lumpers and splitters): "more and more unwieldy definition, with members having less and less mutually in common" and "distinctions without difference, ornate and fussy categories, and failure to see underlying similarities" — the deck's text is verbatim from Wikipedia's "Lumpers and splitters"; the script paraphrases it faithfully. Source: https://en.wikipedia.org/wiki/Lumpers_and_splitters
- Slide 5: species order and three rows match Haeckel plates 4–5 / Romanes copy (fish, salamander, turtle, hen; hog, calf, rabbit, man). The Scientist lists "dog" in place of rabbit; NCSE and Wellcome give rabbit. "arches at the neck and a ladder of segments" = pharyngeal arches and somites, standard for the vertebrate pharyngula stage (writer's `[+]`, verified). Sources as above.
- Slide 6: arm / bat wing / whale flipper as homologous forelimbs — textbook homology (Owen 1843). "two lectures from now" = lecture 4, The Testosterone-Exposed System, per `class.json`. Source: https://en.wikipedia.org/wiki/Homology_(biology)
- Slide 7 (A genetic reminder): 22 autosome pairs plus two sex chromosomes; 47,XXY Klinefelter; 45,X Turner including mosaic and partial-deletion forms — match MedlinePlus. Sources: https://medlineplus.gov/genetics/condition/klinefelter-syndrome/ ; https://medlineplus.gov/genetics/condition/turner-syndrome/
- Slide 8: "approximately 3.2 billion base pairs" (deck) — NHGRI gives "about 3 billion" per haploid copy; 3.1–3.2 Gb is the standard figure. Left as the deck's "approximately".
- Slide 8: SRY, "the sex-determining region", tells the gonad to become a testis (writer's `[+]`, verified). Sources: NHGRI Y fact sheet; MedlinePlus Y chromosome.
- Slide 9 (Greater than the sum of our parts): quotation is Aristotle, *Metaphysics* Book VIII (Eta) ch. 6, 1045a8–10, W. D. Ross translation, verbatim for the clause quoted. Source: http://classics.mit.edu/Aristotle/metaphysics.8.viii.html (Part 6)
- Slide 10: epigenetics gloss ("chemical marks on DNA and its packaging that change which genes are read without changing the sequence") is the standard definition. Generational trauma kept as "the proposition that…", attributed to the course. Pluripotency, quiescence, variable expression — standard definitions, deck terms.
- Slide 11: "Homology … from Greek homos 'same' and logos 'relation'" — the deck's etymology is Wikipedia's exactly; the script attributes the "relation" gloss to the deck, which reads fairly. Source: https://en.wikipedia.org/wiki/Homology_(biology)
- Slide 11: paramesonephric (Müllerian) ducts form in week 6; gonad sexually indifferent until about week 7 (writer's "Around the sixth week … undecided gonad and two pairs of ducts", verified). Sertoli-cell AMH → Müllerian regression; Leydig-cell testosterone → Wolffian → epididymis, vas deferens, seminal vesicles (plus ejaculatory ducts); Müllerian → fallopian tubes, uterus, cervix, upper vagina. Sources: https://en.wikipedia.org/wiki/Paramesonephric_duct ; https://en.wikipedia.org/wiki/Development_of_the_gonads ; https://en.wikipedia.org/wiki/Development_of_the_reproductive_system ; https://www.urology-textbook.com/embryology-testis.html
- Slide 12: external genitalia indifferent "until about the ninth week"; tubercle → glans and body of clitoris / glans and shaft of penis; urogenital folds → labia minora / ventral penis enclosing the urethra; labioscrotal swellings → labia majora / scrotum (writer's `[+]`s, verified). Raphe = midline fusion seam (perineal raphe from the urogenital folds, continuing as the scrotal raphe). Sources: https://en.wikipedia.org/wiki/Development_of_the_reproductive_system ; https://en.wikipedia.org/wiki/Perineal_raphe
- Slide 12: DHT, made locally by 5α-reductase (type 2) from testosterone, drives glans/corpora from the tubercle, corpus spongiosum from the urethral folds and scrotum from the labioscrotal swellings; "testosterone alone cannot accomplish these steps." Sources: https://www.glowm.com/section-view/heading/Male%2520Pseudohermaphroditism%2520Due%2520to%2520Androgen%2520Insensitivity%2520or%25205%25CE%25B1-Reductase%2520Deficiency/item/348 ; https://www.ncbi.nlm.nih.gov/books/NBK539904/
- Slide 12: Skene's (paraurethral) glands homologous to the prostate; Bartholin's (greater vestibular) to the bulbourethral glands, both from the urogenital sinus. Source: https://en.wikipedia.org/wiki/Development_of_the_reproductive_system
- Slide 12: pelvic-floor muscle list (bulbospongiosus, ischiocavernosus, transverse perineal muscles, levator ani, external anal sphincter) present in all bodies; superficial perineal muscles innervated by the perineal branch of the pudendal nerve (S2–S4). Sources: Kenhub pages above.
- Slide 13: GnRH → LH/FSH → testosterone/estradiol — standard. GnRH, LH and FSH receptors are G-protein-coupled; steroid receptors are intracellular ligand-activated transcription factors (writer's `[+]`, verified). Source: https://www.frontiersin.org/articles/10.3389/fendo.2012.00162/full
- Slide 13: the fetal adrenal is "almost as large as the fetal kidney" at mid-gestation; its fetal zone secretes DHEA/DHEA-S as the major precursor for placental estrogen; it involutes rapidly after birth (writer's `[+]`, verified). Sources: https://www.endotext.org/wp-content/uploads/pdfs/adrenal-androgens.pdf ; https://utsouthwestern.elsevierpure.com/en/publications/the-human-fetal-adrenal-gland-a-review-of-its-function-and-develo
- Slide 13: CAIS — 46,XY, testes present (undescended), uterus absent, female-typical external genitalia, AR gene variants. CAH — 21-hydroxylase deficiency is ~95% of CAH; excess adrenal androgens; in classic forms 46,XX external genitalia "do not look clearly male or female"; internal organs female. Sources: https://medlineplus.gov/genetics/condition/androgen-insensitivity-syndrome/ ; https://medlineplus.gov/genetics/condition/21-hydroxylase-deficiency/ ; https://www.iss.it/en/-/deficit-di-21-idrossilasi-en-
- Slide 14 (Critical periods): weeks 0–2 all-or-none (lethal or unaffected); weeks 3–8 greatest sensitivity, major malformations; weeks 9–38 fetal period, functional defects and minor anomalies (writer's `[+]`s, verified). Brain sensitive through the fetal period. External genitalia remain androgen-sensitive after week 12: exposure through ~week 12 can fuse the labioscrotal folds; later exposure causes clitoral enlargement only. Sources: https://fpnotebook.com/OB/Fetus/TrtgnExpsr.htm ; https://www.getoncourse.ai/lessons/us-medical-pg/step-1/anatomy/embryology/teratogens-and-critical-periods/ ; https://en.wikipedia.org/wiki/Progestin-induced_virilization ; https://www.glowm.com/section-view/heading/Congenital-Adrenal-Hyperplasia-Female-Pseudohermaphroditism-and-Virilization/item/347
- Slide 15: "We are so much more same than different / Differentiation events are variable / Attention to differences is most helpful when there is a specific problem to solve" — match source slide 22. "next lecture, on puberty" matches `class.json`.

## Could not verify (softened or removed)
- Slide 10: what the deck's image-only slide 14 shows (writer: "a news item on wild frogs"). Sentence rewritten so it no longer claims what the slide shows; the frog example now stands on the 2019 PeerJ study.
- Slide 8: "That is roughly 3 million letters between any two people" — removed; replaced with the sourced 4–5 million sites versus the reference.
- Slide 8: the deck's "12 million base pairs" has no traceable source; kept as the deck's number, reframed as a population-wide catalogue figure.
- Slide 5: that the deck's image-only slide 7 is in fact the Haeckel/Romanes plate the script describes. Kept, with the artist unnamed and a caution added.

## Beats changed
- None. All 15 subjects checked against the envelope: every subject says no text/letters/numbers; no human figures at all (so no likeness, nudity, restraint or distress questions arise); anatomical plates (brain, karyotype, blastocyst, duct systems, pelvic floor musculature, membrane receptor, embryo-to-fetus row) are structures, not symptoms; the tiger and frog are natural-history plates; the atlas, desk trays and bookshelf are still lifes. `beats.json` parses, 15 beats, slide numbers 1–15 in order matching the 15 `##` headings.

## For the editor's attention
- Two image-only deck slides were given content by the writer: slide 7 ("Which of these is the beginning of human life?") is described as the Haeckel/Romanes eight-column embryo plate, and slide 14 as a frog sex-reversal news item. Neither can be confirmed from the extracted text. The embryo description is almost certainly right for that question; the frog sentence has been made free-standing so it is true regardless. If the deck's slide 14 shows something else, the frog sentence and beat 10 ("Frog At Rest") are a defensible illustration of variable expression but could be swapped.
- Haeckel's embryo drawings are a famous case of exaggerated similarity. The script now carries a one-sentence caution without naming him; the teaching point (shared early plan, arches and somites) survives it. If the lecturer uses a modern photographic comparison instead, the caution can be dropped.
- The deck's "99.9 percent identical" is the common simplification; NHGRI now teaches ~99.6%. The script gives both with the distinction. The deck's "12 million base pairs" has no clear source and is most charitably HapMap's ~10 million common SNPs; the editor may prefer to drop the number from the slide.
- The deck's "Homo from Greek for 'Same' or Latin meaning 'Human'" conflates two words; the genus name is Latin only. The script keeps the deck's framing attributed and resolves it, since the Greek echo is the lecturer's bridge to "homology". Fix on the slide if revised.
- The deck's "logos ('relation')" is Wikipedia's gloss; *logos* more broadly means word, account, reason or ratio. Attributed to the deck in the script, so fair.
- Levator ani innervation is genuinely contested (direct S3–S4 branches vs. pudendal). "Same sacral nerve supply" is deliberately general; do not sharpen it to "pudendal".
- Gene counts for X and Y vary by counting method (X 800–1,400; Y 42–200 across NHGRI, MedlinePlus, Wikipedia). The script uses NHGRI's ~900 and "a few dozen"; any precise Y number will be contradicted by some reference.
- The deck's own wording "externally set gonads" is kept as the deck's description of the Y.
- Beat 12 (pelvic floor from below) is a muscular plate and necessarily frames the perineum. The subject is clinical and asks for musculature only; check the render for stray detail.