Session 11 - Embryology

Question 1

Where can the pituitary gland be found?

Answer 1

Pituitary fossa of the sphenoid bone?

Question 2

What are the two main components of the pituitary?

Answer 2

Anterior lobe

Posterior lobe

Question 3

Outline the
Type pituitary
Origin
and Function

Anterior pituitary

Answer 3

 Andenohypophysis
 Rathke’s Pouch
 Ectoderm Origin
 Endocrine

Question 4

Outline the
Type pituitary
Origin
and Function

Posterior pituitary

Answer 4

 Neurohypophysis
 Infundibulum
 Neuroectoderm Origin
 Neuroendocrine Function

Question 5

What is Rathke’s pouch?

Answer 5

Out-pocketing of stomatodeum (envagination of the roof of the oro-pharynx)

Question 6

Where does the posterior lobe of the pituitary come from?

Answer 6

The Posterior Lobe is derived from the developing brain. A downward-growth from the Diencephalon forms in the midline, called the Infundibulum.

The part of the Diencephalon from which the Infundibulum arises becomes the floor of the hypothalamus.
The connection between the Diencephalon and the Infundibulum becomes the Pituitary Stalk.

The Infundibulum extends down towards the roof of the developing oral cavity, retaining its connection with the brain (pituitary stalk). Nerve fibre tracts develop in the stalk, growing down from the hypothalamus.

Question 7

Outline the development of the anterior pituitary

Answer 7

At the same time as the infundibulum is forming, an out-pushing from the roof of the oral cavity (stomatodeum) grows up to meet it. It is known as Rathke’s Pouch.
It loses its connection with the roof of the mouth and comes to lie anterior to the infundibulum and wrap around the pituitary stalk. Separated from oropharynx by ossification of sphenoid bone.
The cells of Rathke’s pouch differentiate into the endocrine cells of the anterior pituitary.

Question 8

What links hypothalmus and pituitary

Answer 8

A network of blood vessels, the Hypophyseal Portal System, functionally links the anterior lobe to the hypothalamus and posterior lobe.

Question 9

What pathology is associated with rathke#s pouch?

Answer 9

Cysts

Question 10

When does tongue begin to develop?

Answer 10

4th week

Question 11

What is the tongue made up of embryologically?

Answer 11

Two Lateral Lingual Swellings
o	1st Pharyngeal Arch
Three Medial Lingual Swelling
o	1st Pharyngeal Arch
	Tuberculum Impar
o	2nd and 3rd Pharyngeal Arches
	Cupola
o	4th Pharyngeal Arch
	Epiglottal swelling

Question 12

What grows over what in tongue development?

Answer 12

The Lateral Lingual Swellings over-grow the Tuberculum Impar.

The 3rd Arch component of the Cupola overgrows the 2nd Arch component.

Question 13

How does the tongue free itself from floor of pharynx?

Answer 13

Extensive degeneration occurs, freeing the tongue from the floor of the oral cavity, except from the Lingual Frenulum.

Question 14

Where does tonuge lie?

Answer 14

Partly in oral cavity, partly in pharynx

Question 15

What is boundary between anterior 2/3rds and posterior 1/3?

Answer 15

Sulcus terminalies and foramen cecum (important for thyroid)

Question 16

Outline the sensory innervation of the tongue

Answer 16

o	Anterior Two Thirds
	Lingual Nerve (CN V3 – Mandibular Branch of the Trigeminal)
	Nerve of 1st Pharyngeal Arch
o	Posterior Third
	Glossopharyngeal Nerve (CN IX)
	Nerve of 3rd Pharyngeal Arch

Question 17

Where is sensory innervation of the tongue derived from?

Answer 17

First and third arches

Question 18

Outline the special sensory innervation of the tongue

Answer 18

o	Anterior Two Thirds
	Chorda Tympani (CN VII – Facial Nerve)
	Nerve of 2nd Pharyngeal Arch, but passes into the 1st Pharyngeal Arch through the middle ear
o	Posterior Third
	Glossopharyngeal Nerve (CN IX)
	Nerve of 3rd Pharyngeal Arch

Question 19

Where do the intrinsic and extrisic muscles of the tongue develop from?

Answer 19

myogenic precursors that migrate into the developing tongue. Derived from occipital somites

Question 20

What is the motor innervation of the tongue?

Answer 20

o Palatoglossus
 Vagus nerve (CN X)
o All other muscles of the tongue
 Hypoglossal Nerve (CN XII)

Question 21

Where does thyroid gland appear?

Answer 21

Appears in floor of the pharynx, between tuberculum impar and the cupola.
This point if between 1st and 2nd branchial arches and is marked by foramen cecum in adult

Question 22

Where is final position of the thyroid?

Answer 22

Anterior neck

Question 23

What does thyroid do at point of origin and in what from does it descend?

Answer 23

At its point of origin the Thyroid bifurcates and descends as a bi-lobed diverticulum, connected by the Isthmus.

Question 24

What is thyroid connected to throughout its descent?

Answer 24

Thyroglossal duct

Question 25

Give two common thyroid abnormalities

Answer 25

Thyroglossal cyst and fistulae

Question 26

How does a thyroglossal cyst occur?

Answer 26

Cystic remain of thryoglossal duct?

Question 27

Where can thyroglossal cysts be found?

Answer 27

any point along the migratory path of the thyroid gland, but is always near or in the midline of the neck. 50% close to or just inferior to hyoid bone.

Question 28

What is a thyroglossal fistulae?

Answer 28

Cyst connected to outside by fistulous canal.

Question 29

Give two ways thyyroglossal fistulae arises

Answer 29

Rupture of cyst | From birth

Question 30

What is first arch syndome?

Answer 30

First arch syndrome is a spectrum of defects in the development of the eyes, ears, mandible and palate

Question 31

What is cause of first arch syndrome?

Answer 31

Failure of colonisation of the 1st Arch with Neural Crest cells.

Question 32

What is the presentation of first arch syndrome?

Answer 32

Treacher-Collins Syndrome, an Inherited, Autosomal Dominant condition, which is characterised by hypoplasia of the mandible and facial bones.

Question 33

What is Di-George syndrome?

Answer 33

o Congenital Thymic asplasia o Absence of parathyroid glands o Deletion on Chromosome 22 causing a variety of defects

Question 34

What are symptoms Di-George?

Answer 34

```  Cardiac Abnormality (especially tetralogy of Fallot)  Abnormal facies  Thymic aplasia  Cleft palate  Hypocalcaemia / Hypoparathyroidism ``` 22 (deletion on chromosome 22 there)

Question 35

What is CHARGE syndrome caused by?

Answer 35

ALCOHOL o CHD7 Heterozygous Mutation  Chromodomain Helicase DNA-binding domain, ATP-dependant chromatin remodeller o CHD7 expression is essential for the production of multipotent neural crest cells

Question 36

What is the presentation of CHARGE?

Answer 36

```  Coloboma (hole in iris)  Heart defects  Atresia (Choanal) (blockage of posterior nasal cavity)  Retardation of growth and development  Genital hypoplasia  Ear defects ```

Question 37

What is pituitary also known as?

Answer 37

Hypophysis cerebri