Session 11 - Embryology Flashcards
Where can the pituitary gland be found?
Pituitary fossa of the sphenoid bone?
What are the two main components of the pituitary?
Anterior lobe
Posterior lobe
Outline the
Type pituitary
Origin
and Function
Anterior pituitary
Andenohypophysis
Rathke’s Pouch
Ectoderm Origin
Endocrine
Outline the
Type pituitary
Origin
and Function
Posterior pituitary
Neurohypophysis
Infundibulum
Neuroectoderm Origin
Neuroendocrine Function
What is Rathke’s pouch?
Out-pocketing of stomatodeum (envagination of the roof of the oro-pharynx)
Where does the posterior lobe of the pituitary come from?
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.
Outline the development of the anterior pituitary
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.
What links hypothalmus and pituitary
A network of blood vessels, the Hypophyseal Portal System, functionally links the anterior lobe to the hypothalamus and posterior lobe.
What pathology is associated with rathke#s pouch?
Cysts
When does tongue begin to develop?
4th week
What is the tongue made up of embryologically?
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
What grows over what in tongue development?
The Lateral Lingual Swellings over-grow the Tuberculum Impar.
The 3rd Arch component of the Cupola overgrows the 2nd Arch component.
How does the tongue free itself from floor of pharynx?
Extensive degeneration occurs, freeing the tongue from the floor of the oral cavity, except from the Lingual Frenulum.
Where does tonuge lie?
Partly in oral cavity, partly in pharynx
What is boundary between anterior 2/3rds and posterior 1/3?
Sulcus terminalies and foramen cecum (important for thyroid)
Outline the sensory innervation of the tongue
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
Where is sensory innervation of the tongue derived from?
First and third arches
Outline the special sensory innervation of the tongue
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
Where do the intrinsic and extrisic muscles of the tongue develop from?
myogenic precursors that migrate into the developing tongue. Derived from occipital somites
What is the motor innervation of the tongue?
o Palatoglossus
Vagus nerve (CN X)
o All other muscles of the tongue
Hypoglossal Nerve (CN XII)
Where does thyroid gland appear?
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
Where is final position of the thyroid?
Anterior neck
What does thyroid do at point of origin and in what from does it descend?
At its point of origin the Thyroid bifurcates and descends as a bi-lobed diverticulum, connected by the Isthmus.
What is thyroid connected to throughout its descent?
Thyroglossal duct
Give two common thyroid abnormalities
Thyroglossal cyst and fistulae
How does a thyroglossal cyst occur?
Cystic remain of thryoglossal duct?
Where can thyroglossal cysts be found?
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.
What is a thyroglossal fistulae?
Cyst connected to outside by fistulous canal.
Give two ways thyyroglossal fistulae arises
Rupture of cyst
From birth
What is first arch syndome?
First arch syndrome is a spectrum of defects in the development of the eyes, ears, mandible and palate
What is cause of first arch syndrome?
Failure of colonisation of the 1st Arch with Neural Crest cells.
What is the presentation of first arch syndrome?
Treacher-Collins Syndrome, an Inherited, Autosomal Dominant condition, which is characterised by hypoplasia of the mandible and facial bones.
What is Di-George syndrome?
o Congenital Thymic asplasia
o Absence of parathyroid glands
o Deletion on Chromosome 22 causing a variety of defects
What are symptoms Di-George?
Cardiac Abnormality (especially tetralogy of Fallot) Abnormal facies Thymic aplasia Cleft palate Hypocalcaemia / Hypoparathyroidism
22 (deletion on chromosome 22 there)
What is CHARGE syndrome caused by?
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
What is the presentation of CHARGE?
Coloboma (hole in iris) Heart defects Atresia (Choanal) (blockage of posterior nasal cavity) Retardation of growth and development Genital hypoplasia Ear defects
What is pituitary also known as?
Hypophysis cerebri
