Embryology Flashcards
Embryonic age at which lip and palate form
5th-6th week
Lip and Palate formation fusions
- first pharyngeal arch splits into the upper maxillary prominence and lower mandibular prominence
- fusion of the 2 medial nasal prominences forms the midline intermaxillary segment
- left and right maxillary prominences fuse with midline intermaxillary segment forming upper lip and primary palate
* 1st test
Intermaxillary segment becomes…
philtrum of the upper lip, 4 medial maxillary teeth, and the primary palate
unilateral cleft lip
one maxillary prominence fails to fuse with intermaxillary segment
bilateral cleft lip
both maxillary prominences fail to fuse with intermaxillary segment
cleft palate development
7th-8th week of embryonic development –> maxillary prominences give rise to –> palatine shelves –> grow medially and fuse to secondary palate –> fusion of secondary palate with posterior aspect of primary palate forms complete palate
cleft formed by failure of any of these processes
Pierre-Robin sequence
hypoplasia of mandible (i.e. micrognathia) –> glossoptosis (posterior displacement of tongue prevents palatal fusion) –> u-shaped cleft palate
neural crest cells give rise to…
four pharyngeal pouches and the adrenal medulla hence why a defect in one germ-line cell can produce both medullary thyroid cancers from parafollicular c-cells and pheochromocytomas from adrenal medullary chromaffin cells
*i.e. MEN 2A AND 2B with mx in RET proto-oncogene
originate from ectoderm and are b/l paired strips of cells at the margin of the neural tube
embryologic origin of thyroid parafollicular cells
neural crest derived 4th pharyngeal pouch and later fuse with thyroid follicular cells to form thyroid
origin of thyroid follicular cells
outpouching of pharyngeal epithelium
tumors = papillary and follicular
origin of fibromas and fibrosarcomas
mesothelium –> interstitial fibroblasts –> tumors
thymus
3rd branchial pouches
lymphocytes
mesenchymal origin
Pronephros
week 4, then degenerates; first stage of kidney development
Mesonephros
functions as interim kidney for the 1st trimester –> male genital system
Metanephros
appears in 5th week
nephrogenesis lasts until 32-36th week
ureteric bud
caudal end of mesonephros, fully canalized by 10th week
Glomerulus through distal convoluted tubule embryo origin
metanephric mesenchyme following ureteric bud interaction (induces differentiation)
most common cause of fetal hydronephrosis
UPJ obstruction
male genital system
mesonephric duct
epidermis
surface ectoderm
sweat and mammary glands
surface ectoderm
Rathke’s pouch (ant. pituitary)
surface ectoderm
lens + cornea
surface ectoderm
inner ear sense organ
surface ectoderm
olfactory epithelium
surface ectoderm
nasal and oral epithelial lining
surface ectoderm
brain, spinal cord, posterior pituitary, pineal, retina
neural tube
autonomic system
neural crest
adrenal medulla
neural crest
celiac ganglia
neural crest
Schwann cells
neural crest
pia and arachnoid mater
neural crest
aorticopulmonary septum and endocardial cushions
neural crest
branchial arches (bones and cartilage)
neural crest
1st branchial arch
Meckel’s cartilage: mandible, malleus, incus, spheno-Mandibular ligament
Muscles of mastication (temporalis, Masseter, lateral and medial pterygoid), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini
CN V2 and V3
Treacher-collins syndrome
first arch neural crest fails to migrate –> mandibular hypoplasia, facial abnormalities
2nd branchial arch
Richert’s cartilage: stapes, styloid process, lesser horn of hyoid, stylohyoid
mucles of facial expression, stapedius, stylohyoid, posterior belly of digastric
CN VII
3rd branchial arch
cartilage of greater horn of hyoid
stylopharyngeus
CN IX
Congenital pharyngocutaneous fistula
persistence of cleft and pouch –> fistula between tonsillar area, cleft in lateral neck
4th-6th arches
cartilages: thyroid, cricoid, arytenoids, corniculate, cuneiform
4th = most pharyngeal constrictors, cricothyroid, levator veli palatini
6th = intrinsic muscles o larynx except cricothyroid
4th-6th arches nerve
4 = CN X superior laryngeal branch (swallow)
6 = CN X recurrent laryngeal branch (speak)
1st branchial pouch
middle ear cavity, eustachian tube, mastoid air cells, endoderm structures of ear
2nd branchial pouch
epithelial lining of palatine tonsil
3rd branchial pouch
dorsal wings - inferior parathyroids
ventral wings - thymus
4th branchial pouch
dorsal wings - superior parathyroids
mesoderm
connective tissue, muscles, bones and cartilage, serosa, CV system, blood, lymphatics, spleen, internal genitalia, kidneys, ureters, adrenal cortex
endoderm
GI tract, liver, pancreas, lungs, thymus, parathyroid, thyroid follicular cells, middle ear, bladder, urethra
