Embryology

A boards-focused walkthrough of the pharyngeal apparatus — arches, pouches, clefts, and membranes — mapping each arch's cranial nerve, muscles, cartilage, and artery to the classic Step 1 syndromes (DiGeorge, Treacher Collins, branchial cleft cyst) and the recurrent laryngeal nerve.

A Step 1 walkthrough of the first three weeks of human development — fertilization, the bilaminar disc, and gastrulation — mapping each germ layer to its derivatives and the classic congenital defects (neural tube defects, sacrococcygeal teratoma, caudal regression, situs inversus) that boards test by mechanism and presentation.

Gastrulation converts the epiblast into three germ layers, each with a signature set of derivatives that boards probe through classic \"which layer?\" gotchas. This lesson maps ectoderm/mesoderm/endoderm (plus neural crest) to their derivatives and links neural-tube, neural-crest, pharyngeal-apparatus, and intermediate-mesoderm errors to the malformations Step 1 tests.

Traces cardiac development from the splanchnic-mesoderm heart tube through looping and septation, mapping each embryonic segment to its adult derivative, then ties the classic Step 1 congenital defects to the exact septation and neural-crest errors that cause them.

A Step 1 walkthrough of GI development — how the gut tube is divided into foregut, midgut, and hindgut by blood supply, what each segment becomes, and the four morphogenetic events (recanalization, herniation/rotation, pancreatic fusion, cloacal partition) whose failures produce the board-classic malformations: TEF, duodenal atresia, malrotation/volvulus, omphalocele vs gastroschisis, Meckel, and Hirschsprung — each with mechanism and presentation.

A Step 1 embryology lesson tracing the respiratory tree from the week-4 laryngotracheal diverticulum through the five stages of lung development, with the germ-layer derivatives, surfactant biology, and the board-favorite congenital defects (TEF/esophageal atresia, congenital diaphragmatic hernia, neonatal RDS, Potter-related pulmonary hypoplasia). Emphasis is on what goes wrong developmentally and how each malformation presents.

A Step 1 embryology lesson tracing CNS formation from notochord induction through neurulation, neuropore closure, and the 3→5 brain-vesicle sequence, then mapping each derivative and the board-favorite congenital malformations (NTDs, holoprosencephaly, Chiari II, Dandy-Walker) to their exact developmental mechanism and presentation.

A high-yield Step 1 walkthrough of sexual differentiation: the indifferent stage, the SRY switch, and the three hormones (AMH, testosterone, DHT) that build the male tract — with verified derivative and congenital-defect tables and paired CAIS vs. 5α-reductase vignettes.