L21-22: Pharynx, Digestive System, Respiratory System

Question 1

pharyngeal arch structure

Answer 1

mesenchyme core
covered by ectoderm
inside lined w/ endoderm

separated from each other by grooves

components:
artery/aortic arch
cranial nerve
skeletal component

Question 2

pharyngeal endoderm uses Tbx1 to ?

Answer 2

cause expression of FGF8 to induce pharyngeal arch formation

Question 3

what is the only muscle derived from pharyngeal arch 3

Answer 3

stylopharyngeus muscle

Question 4

1st pharyngeal arch

Answer 4

mandibular arch
trigeminal CN V
derivatives:
–meckel’s cartilage

Question 5

2nd pharyngeal arch

Answer 5

hyoid arch
facial CN VII
derivatives:
--reichert's cartilage (hyoid, stapes, styloid process)
--muscles of facial expression

hoxa2 required for arch development

Question 6

3rd and 4th pharyngeal arches

Answer 6

glossopharyngeal CN IX
vagus CN X
derivatives:
--part of hyoid, upper pharynx
--stylopharyngeus muscle
--4th: muscles/cartilages of larynx and lower pharynx

Question 7

derivatives of pharyngeal grooves

Answer 7

external auditory meatus – 1st groove

cervical sinus – 2nd/3rd grooves
**this is a temporary structure

Question 8

pharyngeal pouch derivatives

Answer 8

1st
tympanic cavity, auditory tube

2nd
fossa for tonsils

3rd
inferior parathyroids (shh)
thymus (BMP4)

4th
superior parathyroids

Question 9

beginning of thyroid development

Answer 9

1. begins as node of cells btwn 1st/2nd pharyngeal arches
2. induced via signals from underlying mesenchyme
3. thyroid cells express:
   hhex, nkx2-1, pax8, foxe1

Question 10

define foramen cecum

Answer 10

the thyroglossal duct connects the thyroid diverticulum to the pharynx

the opening of this duct persists as a small pit at the base of the tongue = foramen cecum

Question 11

lateral lingual swellings

Answer 11

located in ventral parts of 1st arch

Question 12

tuberculum impar

Answer 12

ventral swelling btwn 1st/2nd arches

Question 13

copula

Answer 13

ventral swelling btwn 3nd/4rd arches

**foramen cecum is located btwn tuberculum impar and copula

Question 14

patterning of ant/post domains of the gut

Answer 14

ant = nodal
post = FGF4 w/ strong expression near the foregut/midgut boundary

Question 15

how do the following factors effect the foregut or hindgut?
cdx2
pdx1
FGF10

Answer 15

2 — hox gene expression in mid and hindgut

1 — sets apart midgut

10 — establishes cecum

Question 16

stages in development of esophagus

Answer 16

1. circular layer of sm
2. longitudinal layer of sm
3. stratified columnar epi
4. large vacuoles appear
5. lumen recanalizes
6. ciliated columnar epi
7. epi replaced w/ stratified squamous epi

sm derived from splanchnic mesoderm
skeletal muscles derived from paraxial mesoderm

Question 17

initial induction of gut endoderm to form liver

Answer 17

septum transversum — BMP

cardiac mesoderm — FGF

Question 18

transition from simple cuboidal to pseudostratified columnar in liver formation requires ?

Answer 18

Hhex activity

Question 19

formation of hepatic cords

Answer 19

requires loss of E-cadherins and proliferation of cells
Hhex
prox1
tbx3
HNF6

Question 20

bipotential of hepatoblasts

Answer 20

they can become
hepatocytes or
cholangiocytes

Question 21

pancreas arises from 2 primordia

Answer 21

dorsal pancreas:
dorsal gut endoderm

ventral pancreas:
depends on Ptf-1a activity

Question 22

initial site for the development of the respiratory system

Answer 22

the floor of the pharynx/ventral foregut

site is marked by TF nkx2.1

the respiratory bud is primordium for the trachea

Question 23

what arches are the superior laryngeal and recurrent laryngeal nerves associated w/?

Answer 23

sup – 4th arch

recurrent – 6th arch

Question 24

formation of the bronchial tree

Answer 24

pair of buds form at distal end of tracheal bud = bronchial bud

this forms the primary bronchi

and the primary buds give off additional buds to form the rest of the tree

Question 25

syndecan

Answer 25

maintains stability of epi sheets and ducts

Question 26

tenascin

Answer 26

EC matrix protein

interacts w/ syndecan

Question 27

epimorphen

Answer 27

mesenchymal factor that helps epi cells maintain polarity

Question 28

other factors involved in epi branching of the respiratory system development

Answer 28

syndecan
tenascin
epimorphen

Question 29

list the stages of lung development

Answer 29

embryonic stages
wk 4-7

psedoglandular stage
wk 8-16

canalicular stage
wk 17-26

terminal sac stage
wk 26-birth

Question 30

embryonic stage of lung development

Answer 30

formation of respiratory diverticulum up to major bronchopulmonary segments

Question 31

pseudoglandular stage of lung development

Answer 31

formation and growth of duct systems

beginning of formation of pulmonary duct system

Question 32

canalicular stage of lung development

Answer 32

formation of respiratory bronchioles

intense ingrowth of BVs into developing lungs
–close association of capillaries and walls of bronchioles

Question 33

terminal sac stage of lung development

Answer 33

formation of alveoli

epi dif into type I/II alveolar cells

formation of surfactant

Question 34

postnatal stage of lung development

Answer 34

90% of alveoli are formed after birth

Question 35

septum transversum

Answer 35

separates heart from developing liver

partial partition btwn pericardial and peritoneal cavities

gives rise to large ventral portion of diaphragm

Question 36

diaphragm

Answer 36

bulk of it is formed from pleuroperitoneal folds