embryology

• Week 1 = implantation (as a blastocyst)
• Week 2 = 2 cell types of embryoblast: epiblast (--> amniotic sac) & hypoblast (--> yolk sac). In other words, it's a bilaminar disk.

Gastrulation (3 germ cell layers), neurulation (form notochord, which induces ectoderm to become neuroectoderm --> neural plate). Also, blood islands form from mesodermal (mesenchymal) cells this week.

Heart begins to beat, limb buds form. Pronephros degenerates after Week 4.

Fetal movement; fetus looks like baby.

External genitals look male or female.

• Foramen cecum... or, if not obliterated, then pyramidal lobe of thyroid.
• If parts of duct persist: thyroglossal duct cyst = moves w/swallowing, unlike persistent cervical sinus.

2 intermaxillary segments, medial nasal prominences.

2 palatine shelves (forms the palatine raphe)

Failure of primary palate to fuse (more anterior than secondary palate).

Failure of secondary palate structures to fuse (further posterior).

• 1 = maxillary A; 2 = stapedial & hyoid A's
• 3 = common & internal carotid A's
• 4 = (L) aortic arch & (R) subclavian A
• 6 = proximal pulmonary arteries, ductus arteriosus (L)

• Begin = duodenum, just past the common bile duct
• End = after first 2/3 of transverse colon

• Upper = urorectal septum separating the cloaca (end of gut tube)
• Lower = ectoderm

Forms the: pancreatic head, uncinate process (lower 1/2 of head), & main pancreatic duct.

Occlusion of bile duct (connects the hepatic diverticulum to foregut) --> pale stool, dark urine, jaundice.

• Endoderm: front wall of foregut.
• Visceral pleura: from mesoderm covering outside of bronchi
• Parietal pleura: from mesoderm of body wall

Forms ureters, collecting ducts, calyces, pelvis

Forms bladder, allantois, urethra.

Bilateral renal agenesis (b/c malformed ureteric bud) --> oligohydramnios, limb & face malformations b/c fetus is pushed up against uterine wall.

Inferior poles of both kidneys fuse. As kidneys ascend upward, they get "stuck" on inferior mesenteric artery & stay low in abdomen... but at least the kidneys function normally.

Connects ovaries to uterus (the place where fallopian tube meets uterus)

Connects ovary to labia majora.

Women = obliterated. Men = becomes tunica vaginalis... if it stays wide open (patent), then congenital inguinal hernia --> intestines can herniate into scrotum or labia majora (less common).

Incomplete fusion of paramesonephric ducts. Infertility, urinary tract abnormalities. It could also be true that 1 of the paramesonephric ducts is rudimentary.

• Male = glans penis, corpus spongiosum
• Female = clitoris, vestibular bulbs

• Bladder, urethra, allantois is true for both genders
• Male = Cowper's glands (bulbourethral), prostate gland
• Female = Bartholin's glands (greater vestibular), urethral & paraurethral glands

• Female = labia minora
• Male = ventral shaft of penis (underside)

• Female = labia majora
• Male = scrotum

Urethra opens on ventral side (underside) of penis; UTI's. More common than epispadias. Failure of urethral folds to close.

Pee shoots up to ceiling: urethra opens onto dorsal side of penis, b/c faulty positioning of genital tubercle (responsible for glans penis).

ZPA --> A-P axis.

Controls dorsal --> ventral patterning: DAER (apical ectodermal ridge).

Eyes, ears, nose, mouth, skin = epithelial linings. Lens of eye, adenohypophysis. Glands: sweat, saliva, mammary.

Brain, SC, & optic vesicle --> retina, iris, ciliary body. 2 types of neural cells: neuroblasts & glioblasts (for "everything else").

Everything associated with brain & SC. PNS, CN's, dorsal root ganglia, pia & arachnoid mater. Also: chromaffin cells of adrenal medulla, parafollicular (C) cells of thyroid, melanocytes, AP septum.

Epithelium (lining) of gut tube... plus lungs, liver, thymus, parathyroid, pancreas. NOT kidneys.

• Kidneys, urogenital structures, adrenal cortex, cardiovascular/blood/lymphatics, spleen (from foregut mesentery).
• Also: muscle, bone, CT, serious linings of body cavities (ex. peritoneum; sclera, choroid, & anterior chamber for eye).

Auto recess. Abnormally motile cilia (or not at all). Bronchiectasis, female infertility, sinusitis, situs inversus. (If cilia don't move at all, then a 50/50 chance of situs inversus.)

Fetal addiction, developmental defects, placental abruption

Causes clear cell vaginal adenocarcinoma

Hypothyroidism or goiter

Spontaneous abortion (just like w/measles), cardiac abnorm's & cleft palate

Flipper limbs

Placental abnormalities, preterm labor. Also IUGR, ADHD

Inhibit bone growth, discolored teeth

Abortion, fetal hemorrhage, bone deformities

Missing fingers (mnemonic: count the diff types of agents on your fingers)

• Microcephaly, hydrocephalus, facial abnormalities
• Limb dislocation, heart & lung fistulas
• May be abnormal cell migration.

• The most common setup for identical twins. Separate amniotic sacs, but same chorion & placenta.
• Vs. Siamese twins: 1 amniotic sac, too