H&N 10.2- development of midline structures Flashcards
What tissue is the posterior pituitary derived from?
Neurectoderm
What is the infundibulum?
A down-growth of the forebrain during development, towards the rood of the pharynx, which goes on to form the posterior pituitary and the hypophyseal stalk
What tissue is the mature posterior pituitary made of?
neuroendocrine tissue.
What tissue is the anterior pituitary derived from?
Ectoderm.
What is Rathke’s pouch?
An out-pocketing of ectoderm at the stomatodeum.
It grows dorsally to meet the infundibulum.
Forms the anterior pituitary.
Where does the pituitary gland devleop in the foetus?
What does this go on to form?
In the developping sphenoid bone.
Becomes the sella turcica.
What is the name of the tissue connecting the tongue to the floor of the oral cavity?
Ligual frenulum.
How is the tongue anatomically divided?
What forms this division?
-into the anterior 2/3, and the posterior 1/3.
Sulcus terminalis divides these up
What is the apex of the sulcus terminalis known as?
foreamen caecum.
What is the tongue formed from?
Tissues of all the pharyngeal arches.
Broadly, what swellings are present in the developping tongue?
- 2 lateral
- 3 midline.
What are the lateral swellings of the developping tongue better known as, and what is there origin?
Lingual swellings,
Pharyngeal arch 1
What are the names of the 3 midline swellings of the developping tongue and what is their origin?
- Tuberculum impar (Ph 1)
- Cupola (Ph 2,3,4)
- Eppiglottal swelling (Ph 4)
Which swellings of the developping tongue grow the quickest?
The lateral lingual swellings.
How does the developping tongue differ from the mature tongue?
How is this achieved?
It is bound to the floor.
In the mature tongue, the only thing connecting the tongue to the floor of the mouth is the lingual frenulum.
This is achieved by extensive degeneration.
What is the sensory innervation of the tongue?
- anterior 2/3?
- posterior 2/3?
- taste buds?
- anterior 2/3. General sensory- trigeminal and glossopharyngeal.
- posteiror 1/3- general sensory- glossopharyngeal, special sensory-vagus.
- taste buds- chorda tympani (facial)
What is special about the chorda tympani nerve branch, and it’s relation to the ear, during develpoment?
It is a branch of CN VII (2nd PhA) But is passes into the 1st PhA too.
Between the 1st and 2nd PhA, there is the pharyngeal pouch, which goes on to form the middle ear in adults, hence the chorda tympani travels through the middle ear.
What is the motor innervation of the tongue?
Hypoglossal nerve.
It achieves this through migration of myogenic precursors, which innervate occipital somites.
Where does the throid gland begin it’s development?
-on the floor of the pharynx between the tuberculum impar and the cupola
Later marked by the foreamen caecum.
What does the thyroid gland do as it descends?
Bifurcates into 2 lobes connected by the isthmus.
What connects the thyroid gland to it’s beginning location?
Thyroglossal duct.
What should happen to the thryoglossal duct?
What pathologies can occur?
It should close before birth.
-thyroglossal cysts/fistula can result from fialure of the duct to close.
How can you tell a thyroglossal cyst from a thyroid nodule/lump?
The thyroglossal cyst will move on protrusion of the tongue, due to it’s direct association with the tongue.
A thyroid nodule will not move on protrusion of the tongue.
What are the 2 main constituents of the thyroid gland and where do they originate?
- follicular cells- from the thyroid diverticulum.
- parafollicular cells- from the 4th pahryngeal pouch.
How can you differentiate between ectopic thyroid tissue and a branchial cyst?
-ectopic thyroid tissue will be along the midline of the neck.
Branchial cysts follow the sterncleidomastoid muscle
