Embryonic development of the mouth

Question 1

What two layers compose the primitive gut in the embryo?

Answer 1

Splanchnic mesoderm (outer) and endoderm (inner)

Question 2

What does the dorsal mesentery derive from?

Answer 2

Mesoderm

Question 3

Name four structures that derive from the foregut

Answer 3

Mouth
Oesophagus
Pharynx
Liver and pancreas
Stomach
Most of the SI

Question 4

Name three structures that derive from the hindgut

Answer 4

Ileum
Large intestine
Cloaca

Question 5

What depression in the cranial embryo indicates the developing oronasal cavity?

Answer 5

Stomodaeum

Question 6

What is another name for the oral plate? What forms it? What structures in the adult indicate where it used to be?

Answer 6

A.k.a the pharyngeal membrane
Formed from ectoderm of stomodaeum and endoderm of foregut

Pharyngeal arches

Question 7

What layer is the inner lining of the mouth derived from? From which point along the GIT does this change?

Answer 7

The ectoderm - from the laryngopharynx onward is endoderm

Question 8

Where do the pharyngeal arches come from? How many are there, and what do they form?

Answer 8

They are migrating cells of the neural crest
Six in total, though number 5 usually atrophies
Form structures of the head and neck

Question 9

Which arches become cartilage of the larynx?

Answer 9

4 and 6

Question 10

Which arches become the hyoid bones?

Answer 10

2 and 3

Question 11

Which arch becomes the maxilla + mandible?

Answer 11

1

Question 12

Which four structures does arch 1 form initially?

Answer 12

Left and Right maxillary and mandibular processes

Question 13

What develops immediately above the maxillary process?

Answer 13

The frontonasal prominences

Question 14

What does the frontonasal prominence include?

Answer 14

Frontal process

Left and right naso-lateral and naso-medial processes

Question 15

What fuses to form the upper jaw?

Answer 15

The L and R nasomedial and maxillary processes

Question 16

What fuses to form the nose?

Answer 16

The L and R frontal processes and nasolateral processes

Question 17

What fuses to form the lower jaw?

Answer 17

The L and R mandibular processes

Question 18

What fuses to form the nasolacrimal duct?

Answer 18

The lateral nasal prominence and the maxillary prominence - endoderm between canalises to create the duct

Question 19

What produces the interspecies variation in the upper lip (philtrum vs no philtrum)

Answer 19

Variation in degree of fusion of medial nasal prominences

Question 20

What is the term for ‘long’ faced (normal)

Answer 20

Dolocephalic

Question 21

What determines face length?

Answer 21

The growth of the maxillary and mandibular processes - everything else will follow

Question 22

Which two processes failed to fuse in ‘facial cleft’?

Answer 22

Maxillary and nasolateral processes (nasolacrimal duct failed to form)

Question 23

Which two processes failed to fuse in cheiloschisis?

Answer 23

Maxillary and nasomedial processes

Question 24

What are the three parts that fuse to form the palate?

Answer 24

Left palatine process
Right palatine process
Median palatine process/intermaxillary palatine process

Question 25

What structure exists at the point where the three palatine constituents meet?

Answer 25

The incisive foramen - leads to vomeronasal organ

Question 26

What is palatoschisis?

Answer 26

Failure of the palatine processes to fuse

Question 27

What do the pharyngeal pouches form?

Answer 27

Auditory tube, fossae of tonsils, parathyroid thymus and thyroid glands

Question 28

From which structure is the torus in ruminants derived?

Answer 28

The median tongue swelling

Question 29

What does the proximal tongue swelling form? what about the two distal swellings?

Answer 29

Distal swellings together with the median swelling will form tongue body, proximal swelling will form tongue root

Question 30

How do the multiple origins of the tongue relate to its innervation?

Answer 30

It is innervated by severeal different cranial nerves as it arises from several different places

Question 31

Which germ layer are the oesophageal glands derived from?

Answer 31

Endoderm

Question 32

Which germ layer is the oesophegeal muscle derived from?

Answer 32

Splanchnic mesoderm

Question 33

Which mesentery of the developing stomach will become the great mesentery?

Answer 33

The mesogastrium - it is stretched when the stomach moves away from midline

Question 34

Describe the development of the intestines

Answer 34

Grow much faster than embryo body length, forms a loop
Get physiological herniation into the umbilical stalk
The cranial mesenteric artery will develop from the middle of the loop
Intestinal loop twists on itself once, and the cranial arm coils extensively to form the small intestine

Question 35

What is the pancreas derived from? Which part becomes which lobe?

Answer 35

The dorsal and ventral primordia

Dorsal => left
Ventral => right

Question 36

Which structure grows to separate the urogenital from anorectal canal?

Answer 36

The urorectal septum

Question 37

What is the name for the anal area membrane?

Answer 37

Proctadeum

Question 38

What does the septum transversum form? What other structures contribute?

Answer 38

Contributes to the diaphragm, along with the two pleuropericardial folds