Session 11 Flashcards
Where is the pituitary gland?
slide 4 lec 1
Why is the pituitary gland a “two in one gland”?
• a.k.a. hypophysis or hypophysis cerebri • Closely related to the hypothalamus • Two lobes • Posterior • neuroendocrine • Anterior • endocrine
• The pituitary has ectoderm AND neurectoderm origins
• Rathke’s pouch • Ectoderm • Anterior pituitary • Infundibulum • Neurectoderm • Posterior pituitary
slide 5 lec 1
Infundibulum
- Neural tube component • Downward out-growth of the forebrain
- grows towards the roof of the pharynx
Rathke’s pouch
• Out-pocketing of ectoderm of the stomatodeum • An evagination of the roof of the (oro-) pharynx • Grows dorsally towards the developing forebrain
Derivation of the pituitary gland
Rathke’s puch - anterior pituitary
infundibulum - pituitary stalk and posterior pituitary
Describe location of tongue, and whats its made of?
• Lies partly in the oral cavity & partly in the pharynx • Highly mobile • Lingual frenulum • Comprised of intrinsic & extrinsic muscles
Describe the development of the tongue
- Primordia of the tongue appear at about the same time as the palate begins to form • Receives a component from each of the Pharyngeal arches
- 2 lateral lingual swellings • Ph Arch 1 • 3 median lingual swellings • Ph Arch 1 • Tuberculum impar • Ph Arch 2 & 3 (+4) • Cupola • Ph Arch 4 • Epiglottal swelling
- Lateral lingual swellings over-grow the tuberculum impar • The 3rd arch component of the cupola over-grows the 2nd arch component • Extensive degeneration occurs, freeing tongue from the floor of the oral cavity • lingual frenulum
Describe the sensory innervation of the tongue and how it relates to its development
• Mucosa of anterior 2/3s derived from Ph As 1 & 3 • General sensory innervation CN V & IX • Posterior 1/3 derived from Ph A 3 (& 4) • General & special sensory CN IX & X • taste buds develop in papillae • Special sensory innervation CN VII
Chorda tympani and the tongue
• branch of CN VII, nerve of second arch • BUT • passes into first arch • THEREFORE • passes through middle ear
Motor innervation of the tongue in relation to its development
• Both intrinsic & extrinsic muscles of the tongue develop from myogenic precursors that MIGRATE into the developing tongue •CN XII
The thyroid gland and its development
• Primordium of the thyroid gland appears in the floor of the pharynx between the tuberculum impar and the cupola • Final position is anterior neck
Descent of the thyroid • Point of origin for the descent of the thyroid is later marked by foramen cecum • Bifurcates and descends as a bi-lobed diverticulum connected by the isthmus
Thyroglossal duct
• During its descent the thyroid gland remains connected to the tongue by the thyroglossal duct • Pyramidal lobe • Approx 50% of population
Thyroid abnormalities from development
• Thyroglossal cysts & fistulae • Ectopic thyroid tissue
Summary I: the midline structures development
• Pituitary • Ectoderm (Rathke’s pouch) + neurectoderm (infundibulum) • Tongue • Forms in the floor of the pharynx with contributions from all 5 Ph Arches • Thyroid • Midline diverticulum in floor of pharynx • Migrates anterior to pharyngeal gut, hyoid bone & laryngeal cartilages
What embryonic structures contribute to the development of the face?
panopto