Flashcards in Development of Midline Structures Deck (88):
Where does the pituitary gland sit?
In the sella turcica, or pituitary fossa, of the sphenoid bone
What is the pituitary gland made up of?
Anterior and posterior lobe
What is the anterior lobe of the pituitary gland also known as?
What is the embryological origin of the anterior lobe of the pituitary gland?
What kind of tissue is the anterior lobe of the pituitary gland?
What is Rathke's pouch?
Idk jono wasn't very clear
What is the posterior lobe of the pituitary also known as?
What is the embryological origin of the posterior lobe of the pituitary?
What kind of function does the posterior lobe of the pituitary have?
What is the infundibulum?
How are the embryological origins of the anterior and posterior pituitary gland related?
They have entirely separate embryological origins, which later become structurally and functionally linked.
What is the posterior pituitary gland derived from?
The developing brain
What is the first step in the development of the posterior lobe of the pituitary gland from the developing brain?
A down-growth from the dicephalon forms in the midline, called the infundibulum
What happens to the part of the dicephalon from which the infundibulum arises as development proceeds?
It becomes the floor of the hypothalamus
What does the connection between the dicephalon and infundibulum become?
The pituitary stalk
Where does the infundibulum extend?
Down towards the roof of the developing oral cavity
What does the infundibulum retain when it extends down towards the roof of the oral cavity?
It's connection with the brain
How does the infundibulum retain its connection to the brain?
By the pituitary stalk
What develops in the pituitary stalk?
Nerve fibre tracts
How do nerve fibre tracts develop in the pituitary stalk?
They grow down from the hypothalamus
What happens simultaneously to the infundibulum forming?
An out-pouching from the roof of the oral cavity grows up to meet the infundibulum
What is the out-pouching that pushes out from the roof of the oral cavity to meet the infundibulum known as?
What happens to Rathkes pouch once it has met the infundibulum?
It loses its connection with the roof of the mouth
Where does Rathke's pouch come to lie?
Anterior to the infundibulum, and wrapped around the pituitary stalk
What happens to the cells of Rathke's pouch?
They differentiate into the endocrine cells of the anterior pituitary
What functionally links the anterior lobe and posterior lobe of the hypothalamus?
A network of blood vessels, the hypophyseal portal system
What may persistent remnants of Rathke's pouch form?
When does the tongue appear in development?
What does the appearance of the tongue in development coincide with?
It is about the same time as the palate begins to form
What appears first in development of the tongue?
Two lateral lingual swellings
Three medial lingual swellings
What are the lateral lingual swellings derived from?
1st pharyngeal arch
What are the medial lingual swellings derived from?
1st, 2nd, 3rd, and 4th pharyngeal arch
What part of the tongue is derived from the 1st pharyngeal arch portion of the medial lingual swellings?
What part of the tongue is derived from the 2nd and 3rd pharyngeal arch portion of the medial lingual swellings?
What part of the tongue is derived from the 4th pharyngeal arch portion of the medial lingual swellings?
What happens to the lateral lingual swellings as development proceeds?
They over-grow the tuberculum impar
What happens to the 3rd arch component of the cupola as development proceeds?
It overgrows the 2nd arch component
How is the tongue freed from the floor of the oral cavity?
Extensive degeneration occurs
What part of the tongue is not freed from the floor of the oral cavity?
What is the general sensory innervation of the anterior 2/3 of the tongue?
Lingual nerve (CN VIII - mandibular branch of trigeminal)
Nerve of 1st pharyngeal arch
What is the general sensory innervation of the posterior third of the tongue?
Glossopharyngeal arch (CN IX)
Nerve of 3rd pharyngeal arch
What is the special sensory innervation to the anterior 2/3 of the tongue?
Chorda tympani (CN VII - facial nerve)
What pharyngeal arch is the facial nerve related to?
2nd pharyngeal arch
Where does the nerve of the 2nd pharyngeal arch pass?
Into the 1st pharyngeal arch, through the middle ear
What is the special sensory innervation of the posterior third of the tongue?
Glossopharyngeal nerve (CN IX)
What pharyngeal arch is the glossopharyngeal nerve associated with?
What are both the intrinsic and extrinsic muscles developed from?
Myogenic precursors that migrate into the developing tongue
What is the palatoglossus innervated by?
The vagus nerve (CN X)
What are all muscles of the tongue apart from the palatoglossus innervated by?
Hypoglossal nerve (CN XII)
What is the first endocrine gland to develop?
The thyroid gland
Where does the thyroid gland appear in development?
On the floor of the pharynx, between the tuberculum impar and cupola
What does the thyroid gland appear as in development?
An expansion of the mesenchyme
Where does the site of origin of the thyroid gland lie in relation to the brachial arches?
Between the 1st and 2nd
What is the site of origin of the thyroid gland marked by in the adult?
Where is the final position of the thyroid gland?
The anterior neck
How does the thyroid gland reach its final position from its embryonic origin?
At its point of origin, the thyroid bifurcates and descends as a bi-lobed diverticulum, connected by the itsthmus
What is the relationship between the thyroid gland and the tongue during its descent?
It remains connected to the tongue by the thyroglossal duct
What are the constituent cells of the thyroid gland?
Parafollicular cells (C-cells_
What do the follicular cells of the thyroid gland secrete?
Thyroxine and triiodothyronine
What are the follicular cells of the thyroid gland formed from?
The thyroid diverticulum
What is the thyroid diverticulum derived from?
1st/2nd brachial arches
What do the parafollicular cells of the thyroid gland secrete?
What are the parafollicular cells of the thyroid gland formed from?
The ultimobranchial body of the 4th pouch
What are the potential thyroid abnormalities of development?
Thyroglossal cysts and fistulae
Ectopic thyroid tissue
First arch syndrome
Where may a thyroglossal cyst lie?
At any point along the migratory path of the thyroid gland, but always near, or in, the midline of the neck
What are thyroglossal cysts/fistulae?
Cystic remnants of the thyroglossal duct
What % of thyroglossal cysts are close to, or just inferior, to the body of the hyoid bone?
What is a thyroglossal fissure?
When a thyroglossal cyst is connected to the outside by a fistulouscanal, a thyroglossal fissure
What is the usual scenario in which a thyroglossal fissure arises?
Secondarily, after a rupture of a cyst
When may a thyroglossal fistula occur, other than secondary to a rupture of a cyst?
May be present at birth
Where may ectopic thyroid tissue be found?
Anywhere along the path of descent of the thyroid gland
Where is ectopic thyroid tissue commonly found?
In the base of the tongue, just behind the foramen cecum
What pathologies is ectopic thyroid tissue subject too?
The same as the thyroid gland itself
What is First Arch syndrome?
A spectrum of defects in the development of the eyes, ears, mandible, and palate
What is First Arch syndrome thought to result from?
Failure of colonisation of the 1st arch with neural crest cells
What is the presentation of First Arch syndrome known as?
What is the inheritance pattern of Treacher-Collins syndrome?
What is Treacher-Collins syndrome characterised by?
Hypoplasia of the mandible and facial bomes
What is DiGeorge Syndrome also known as?
Congential thymic aplasia
What is the abnormality in DiGeorge syndrome?
Absence of parathyroid hormone
What causes DiGeorge syndrome?
Deletion of chromosome 22
What are the features of DiGeorge syndrome?
Cardiac abnormality (especially tetralogy of Fallot)
Abnormal facies (not a typo)
What is the abnormality in CHARGE syndrome?
CHD7 heterozygous mutation
What does the CHD7 gene code for?
Chromodomain helicase DNA-binding domain, an ATP-dependant chromatin remodeller
What is CHD7 expression essential for?
The production of multipotent neural crest cells
What are the features of CHARGE syndrome?
Retardation of growth and development
What is coloboma?
Hole in iris