Week 10.0 - Development of midline structures Flashcards
What is the sella turcica?
-The bony pocket where the pituitary sits
What is the infundibulum with regards to pituitary development?
-A downward outgrowth of the forebrain which gives rise to the posterior pituitary and the neural stalk
What is rathke’s pouch?
-An outpocketing of ectoderm of the stomatodeum which grows dorsally towards the developing forebrain and becomes the anterior pituitary after ossification of the skull
Describe how the pharayngeal arches contribute to the development of the tongue
1) Mesenchyme proliferations in each of the pharyngeal arches appear in the floow of the oral cavity at the same time as the palate develops
- Ph A1-> two lateral swellings and medial tuberculum impat
- Ph A2,3 and 4 -> cupola
- Ph A4 (6) -> epiglottal swelling
2) Lateral swellings overgrow TI and the 3rd arch copula overgrows the 2nd
3) Extensive degeneration by apoptosis occurs freeing the tongue from the oral cavity (lingual frenulum)
What tethers the tongue to the floor?
-Lingual frenulum
What/where is sulcus terminalis?
-grooves on the posterior 1/3 of the tongue
What/where is foramen cecum?
-Demarkation on the tongue where sulcus terminalis meet. denotes the point of descent of the thyroid
Describe the sensory innervation to the tongue
- Ant 2/3 -> special sensory = chorda tympani (VII), general sensory = V3 (lingual branch)
- Post 1/3 gen and special = CNIX (small section by CNX)
Through what part of the ear does chorda tympani pass? What is the clinical significance of this?
- Middle ear
- Can affect taste in otitis media and other middle ear infections
From where do the muscles of the tongue develop?
-Myogenic precurors of occipital somites which migrate into the developing tongue
Describe the motor innervation of the tongue
-Hypoglossal
Where does the primordia of the thyroid gland appear?
-In the floor of the pharynx between tuberculum impar and cupola
Describe the descent of the thyroid gland
- Begins at what is later the foramen cecum and bifurcates and descends as a bi-lobed diverticulum connected by an isthmus
- Remains connected to tongue during descent by thyroglossal duct
- Looses patency after developed
What is a pyramidal lobe of the thyroid?
-Normal variant which remains in 50% of the population and is associated with a remnant of the thyroglossal duct
What is a thyroglossal cyst?
-Cyst which forms in a persistent thyroglossal duct
Why can the development of the thyroid gland make it possible to get ectopic thyroid tissue?
- Remnants of the thyroglossal duct
- Failed descent of all or part of the thyroid
Name some differentials of swellings in the neck (not tumour)
- Branchial cyst
- Thyroid goitre
- Cerivcal lymphadenopathy
- Thyroglossal cyst
What is the cause of a cleft lip and palate?
-Failed fusion of the FNP with the palatal shelves of the maxillary prominence of the 1st Ph A
What is first arch syndrome?
-A spectrum of defects in development involving the eyes, ears mandible and palate as a result of failed colonisation of the 1st Ph A with neural crest cells
What is treacher-collins syndrome?
- Form of first arch syndrome which is an autosomal dominant condition
- Characterised by hypoplasia of the mandible and facial bones
What is di-george syndrome?
-Disorder of the pharyngeal pouches resulting in congenital thymic aplasia and absence of the parathyroid gland due to abnormal development of neural crest cells CATCH 22 (deletion of Chromosome 22) -Cardiac abnormality -Abnormal facies -Thymic aplasia -Cleft palate -Hypoparathyroidism
