Embrology Flashcards
Kidney development types
Pronephros (non functional)
Mesonephros (transient and functional)
Metonephros (permanent kidney)
Rudimentary, transient kidneys (nephrotomes) have cavities (nephrocoeles) developing craniocaudally
Mesonephros
Appears at 3 weeks, drains into mesonephric duct. Communication breaks down at 8 weeks
Urine formation begins?
Weeks 11-12
XY development
Week 7 - > Testis determining factor stimulates sex cord (coelomic epithelium)/sertoli.
Week 8 - leydig cells (intermediate mesenchyme) make T.
Tunica albuingea formed (int. meso)
Cord breadk down - >rete testis
Anti-mullarian hormone (sertoli cells) causes paramesonephric to degrade (utriculus prostaticus) and mesonephric duct - > ductus deferens, epidiymus, ejaculatory duct and seminal vesicles.
Week 10 - > phallus elongates, UG folds approach to cover urethra
XX development
Week 6, paraseonephric duct appears and pinches off.
In absence of AMH, forms uterine tubes, uterus, upper 1/3 of vagina.
Week 8: No TFD then sec cords regress, vascular stroma in medulla (further development in 4th month)
Week 9: mesonephric degrade, but can remain as cysts (Garter’s ducts)
Week 10: genitalial develop (but UG folds never fuse)
Undifferentiated gonads
Week 3 v- > yolk sac to genital ridge (medial on coelomic epithelium)
Undifferentiated until week 6.
Gonadal descent
3rd month
Testes goes through inguinal canal. Testes have anteriro double payer of peritoneum (tunica vaginalis).
Ovaries remain intraperitoneal.
Gubernaculum becomes round ligament in XX
Renal agenesis
Ureteric bud fails/regresses. Incompatible with life
Horseshoe kidney
Inferior poles fuse together
UG/rectum separation
Week 8, but still membrane covered.
Median umbilical ligament
Remnant of alantois, fibrous cord. Can be patent (urachal fistula) with urine leaking out of umbilicus
Medial umbilical ligament
Remnant of umbilical vein
ureteric bud gives
Ureter, renal pelvic, major/minor calyx and collecting duct
Metanephros gives
Nephron 9other than CD)
Neural groove driver
Notocord secretes chordin (morphogen inhibits BMP/TGF beta, they drive epidermal development)
Somites make
Skeletal muscle, vertebrae, cartilage
Date of gastrulation
15
Timing of differentiation of neuro ectoderm and ectoderm
4th week
Neural crest cell migration
Week 5
PNS neural crest cells
Neurons, sensory/sympathetic/parasympathetic ganglia, plexi, neuroglial cells, scwann cells
Endocrine neural crest
Adrenal medulla
Pigment neural crest cells
melanocytes
Facial bone/cartilage neral crest
Anterior and facial skull cartilage and bone
Connective tissue neural crest
Cornea, tooth paillae, dermis, smooth muscle adopse tissue of skin/head/neck
Gland connective tissue
Connective tissue/smooth muscle of aortic arch arteries
Trunk cells
Can remain in somite - DRG
If through somite then sympathetic/adrenal medulla
Vagal/sacral NC
Enteric ganglia
MElanocytes
Dosrolateral neural crests between ectoderm and somites
Cardial NC
Form endothelial lining of aortic arches, endocardial cushion, aorticopulmonary septum
Cranial NC influenced by
Rhombomeres.
Forms craniofacial mesenchyme, cranial neurons, glia.
Middle ear/jaw bone formed from
Pharyngeal arches
Viscerocranium
NC cell derived. Makes frontal, nasal, lacrimal, zygomatic, maxilla, incisive, mandible, sphenoid and SQUAMOUS temporal
Neurocranium
Paraxial mesoderm (somites). Has parietal, petrous temporal and occipital
Laryngeal cartilages
MEsenchyme from lateral plate mesoderm
Neuropore closure
Anterior at day 25, posterior at day 28
Brain veiscles form
Weeks 3-4
Rhombencephalon
Hindbrain - becomes metencephalon (pons/cerebellum, 4th ventricle) and myeloncephalon (medulla/4th ventricle)
Metencephalon
Pons/ cerebellum/ 4th ventricle)
Myeloncephalon
Medulla/4th ventricle
Mesencephalon
Midbrain
Procsencephalon
Becomes telencephalon (cerebrum, basal nuclei, lateral ventricles) and diencephalon (dicenephalon, retina, 3rd ventricle)
Telencephalon
cerebrum, basal nuclei, lateral ventricles)
Dicencephalon
Diencephalon, retina, 3rd ventricle)
Brain flexures
Cerical flexure is between hindbrain and spinal cord (transient)
Cephalic flexure is at midbrain - remains in adults
Stem cell source for spinal cord neurons?
Ependymal layer (neuroepthelial layer/neuroblast layer)
Spinal cord development
Marginal layer (white matter) with mantle layer (cell bodies)
Mantle layer
Alar plate (sensory reception from NC DRG) and basilar plate (motor cell bodies from mantle)
Neuroblasts and glioblasts
Neuroblasts give neurons, glioblasts give astrocytes and olgiodendrocytes
Oligodendrocytes come from
Neuroepithelium (ependymal layer)
Sulcus limitans
Groove preventing cell bodies migrating accross
Spinal cord development complete by
Week 6
Neural tube defects seen
Weeks 3-4
Spina bifida is
Failure of vertebral arch fusion
Spina bifida grading
Minor is occulta, exposed cauda equina but fat pad protects
Spina bifida cystica can be meningocoele (meninges protrude) or myelomeningocoele (meninges plus cauda equina)
SB diagnosis
MS-AFP and U/S
Encephalocele, anencephaly, hydrocephalus
Encephalocoele is failure of posterior skull fusion
Anencephaly is failure for anterior to fuse
Hydrocephalus is fluid accumulation in brain - associated with spina bifida
