Embryology

Question 1

Embryonic age at which lip and palate form

Answer 1

5th-6th week

Question 2

Lip and Palate formation fusions

Answer 2

1. first pharyngeal arch splits into the upper maxillary prominence and lower mandibular prominence
2. fusion of the 2 medial nasal prominences forms the midline intermaxillary segment
3. left and right maxillary prominences fuse with midline intermaxillary segment forming upper lip and primary palate
   * 1st test

Question 3

Intermaxillary segment becomes…

Answer 3

philtrum of the upper lip, 4 medial maxillary teeth, and the primary palate

Question 4

unilateral cleft lip

Answer 4

one maxillary prominence fails to fuse with intermaxillary segment

Question 5

bilateral cleft lip

Answer 5

both maxillary prominences fail to fuse with intermaxillary segment

Question 6

cleft palate development

Answer 6

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

Question 7

Pierre-Robin sequence

Answer 7

hypoplasia of mandible (i.e. micrognathia) –> glossoptosis (posterior displacement of tongue prevents palatal fusion) –> u-shaped cleft palate

Question 8

neural crest cells give rise to…

Answer 8

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

Question 9

embryologic origin of thyroid parafollicular cells

Answer 9

neural crest derived 4th pharyngeal pouch and later fuse with thyroid follicular cells to form thyroid

Question 10

origin of thyroid follicular cells

Answer 10

outpouching of pharyngeal epithelium

tumors = papillary and follicular

Question 11

origin of fibromas and fibrosarcomas

Answer 11

mesothelium –> interstitial fibroblasts –> tumors

Question 12

thymus

Answer 12

3rd branchial pouches

Question 13

lymphocytes

Answer 13

mesenchymal origin

Question 14

Pronephros

Answer 14

week 4, then degenerates; first stage of kidney development

Question 15

Mesonephros

Answer 15

functions as interim kidney for the 1st trimester –> male genital system

Question 16

Metanephros

Answer 16

appears in 5th week

nephrogenesis lasts until 32-36th week

Question 17

ureteric bud

Answer 17

caudal end of mesonephros, fully canalized by 10th week

Question 18

Glomerulus through distal convoluted tubule embryo origin

Answer 18

metanephric mesenchyme following ureteric bud interaction (induces differentiation)

Question 19

most common cause of fetal hydronephrosis

Answer 19

UPJ obstruction

Question 20

male genital system

Answer 20

mesonephric duct

Question 21

epidermis

Answer 21

surface ectoderm

Question 22

sweat and mammary glands

Answer 22

surface ectoderm

Question 23

Rathke’s pouch (ant. pituitary)

Answer 23

surface ectoderm

Question 24

lens + cornea

Answer 24

surface ectoderm

Question 25

inner ear sense organ

Answer 25

surface ectoderm

Question 26

olfactory epithelium

Answer 26

surface ectoderm

Question 27

nasal and oral epithelial lining

Answer 27

surface ectoderm

Question 28

brain, spinal cord, posterior pituitary, pineal, retina

Answer 28

neural tube

Question 29

autonomic system

Answer 29

neural crest

Question 30

adrenal medulla

Answer 30

neural crest

Question 31

celiac ganglia

Answer 31

neural crest

Question 32

Schwann cells

Answer 32

neural crest

Question 33

pia and arachnoid mater

Answer 33

neural crest

Question 34

aorticopulmonary septum and endocardial cushions

Answer 34

neural crest

Question 35

branchial arches (bones and cartilage)

Answer 35

neural crest

Question 36

1st branchial arch

Answer 36

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

Question 37

Treacher-collins syndrome

Answer 37

first arch neural crest fails to migrate --> mandibular hypoplasia, facial abnormalities

Question 38

2nd branchial arch

Answer 38

Richert's cartilage: stapes, styloid process, lesser horn of hyoid, stylohyoid mucles of facial expression, stapedius, stylohyoid, posterior belly of digastric CN VII

Question 39

3rd branchial arch

Answer 39

cartilage of greater horn of hyoid stylopharyngeus CN IX

Question 40

Congenital pharyngocutaneous fistula

Answer 40

persistence of cleft and pouch --> fistula between tonsillar area, cleft in lateral neck

Question 41

4th-6th arches

Answer 41

cartilages: thyroid, cricoid, arytenoids, corniculate, cuneiform 4th = most pharyngeal constrictors, cricothyroid, levator veli palatini 6th = intrinsic muscles o larynx except cricothyroid

Question 42

4th-6th arches nerve

Answer 42

4 = CN X superior laryngeal branch (swallow) 6 = CN X recurrent laryngeal branch (speak)

Question 43

1st branchial pouch

Answer 43

middle ear cavity, eustachian tube, mastoid air cells, endoderm structures of ear

Question 44

2nd branchial pouch

Answer 44

epithelial lining of palatine tonsil

Question 45

3rd branchial pouch

Answer 45

dorsal wings - inferior parathyroids ventral wings - thymus

Question 46

4th branchial pouch

Answer 46

dorsal wings - superior parathyroids

Question 47

mesoderm

Answer 47

connective tissue, muscles, bones and cartilage, serosa, CV system, blood, lymphatics, spleen, internal genitalia, kidneys, ureters, adrenal cortex

Question 48

endoderm

Answer 48

GI tract, liver, pancreas, lungs, thymus, parathyroid, thyroid follicular cells, middle ear, bladder, urethra