Head/Neck Dev't. Flashcards
Describe the Treacher-Collins Syndrome.
This is caused by a defect in the first pharyngeal arch where somites of the paraxial mesoderm in this region do not complete the formation of associated facial structures.
What are the muscles of the 1st pharyngeal arch derivatives in an adult?
Muscles of mastication: Temporalis, Masseter, Medial and Lateral Pterygoids; Mylohyoid, Anterior Digastric, Tensor Tympani, Tensor Veli Palatini “MATT”
What is the blood supply and the cranial innervation for the muscles of the 1st pharyngeal arch?
Blood supply: Maxillary Artery
Innervation: CN V-3 Mandibular division
What are the muscles of the 2nd pharyngeal arch in an adult? What are they innervated by?
Muscles of facial expression, Posterior digastrics, Stylohyoid, Stapedius “SPS”;
CN VII, Facial Nerve
What muscle is derived from the 3rd pharyngeal arch and what is it innervated by?
Stylopharyngeus muscle lies below the glossopharyngeal nerve (CN IX), which it is innervated by.
What are the muscles of the 4th pharyngeal arch and what are they innervated by?
Soft palate muscles (except tensor), Cricothyroid, Pharyngeal muscles; Innervated by the Superior laryngeal branch of the vagus nerve (CN X)
What are the muscles derived from the 6th pharyngeal arch and what are they innervation by?
Intrinsic laryngeal muscles (except cricothyroid), esophageal muscles are innervated by the recurrent laryngeal branch of the vagus nerve (CN X).
The aortic arch arteries of the 3 pharyngeal arch are the _________ and ________ ________ arteries. This is associated with the _________ nerve within that arch.
Common and internal carotid arteries. Glossopharyngeal nerve (CN IX)
There are 5 pharyngeal arches numbered: _______. There are ___ pharyngeal clefts which are invaginations of _________ around the pharynx.
pharyngeal arches: 1,2,3,4 and 6;
Clefts are invaginations of Ectoderm
Define the oropharyngeal membrane.
This is the place where the ectoderm and mesoderm meet at the stomodeum (future mouth). This disintegrates in embryologic development to form the lumen for a continuous GI tract.
The anterior 2/3 of the tongue has general sensation relayed through the ___________ nerve (V-3); whereas, special (taste) sensation is relayed through the _____________.
Lingual nerve (V-3); Chorda tympani (VII)
The posterior 1/3 of the tongue has its general sensation of the mucosa innervated by the __________; while the taste sensation is innervated by _________ and some _______.
CN IX;
CN IX and some CN X
Define Mesenchyme bumps.
These are structures that underlying the endoderm of the ventral midline-pharyngeal wall. They proliferate during development.
Myoblasts migrate from the ____________ somitomeres within the _______ mesoderm to the developing tongue mesenchyme.
Occipital somitomeres;
Paraxial mesoderm
The thyroid gland originates from the 2nd arch within the ________ _______, but migrates down toward the 4th pouch where the ___________ glands lay.
Foramen cecum;
Parathyroid glands
Within the 1st arch related to the developing tongue, the 2 lateral lingual swellings must fuse, otherwise that person is born with __________.
Ankyloglossia where the tongue is tied since the frenulum is attached to the tip. The tongue has limited or no ability to protrude out of the mouth.
Rostral to the 1st arch is the ________ prominence. The mesoderm portion of the 1st arch forms the 2 _________ prominences and 2 _________ prominences.
Superior to 1st arch = Frontonasal prominence;
1st arch mesoderm = 2 maxillary + 2 mandibular prominences
The front nasal prominence is innervated by the _________ nerve. It consists of what embryonic structures?
CN V1 (ophthalmic division) innervates nose midline, superior line of nasal septum, lateral nasal folds and the frontal prominence (which forms the forehead and upper eyelids).
The maxillary prominence is innervated by the ________ nerve and forms what structures in the adult?
CN V2 which innervates the lower eyelid, upper cheeks and secondary palate (which forms the inferior nasal cavity) in the adult.
The mandibular prominence in the embryo is innervated by the _______ nerve and what adult structures?
CN V3 (mandibular division) which innervates the lower cheeks, mandible and lip.
The Hypopharyngeal eminence is formed at what two pharyngeal arches?
3rd and 4th pharyngeal arch.
In the development of the embryonic face what do the nasolacrimal groove and nasal placode pit form?
The nasolacrimal groove forms the nasolacrimal duct and lacrimal sac. Meanwhile, the nasal placode pit, near the stomodeum, forms the oral and nasal epithelium.
The anterior portion of the hard palate, anterior to the incisive foramen is the _____ palate whereas the bony-soft, _____ palate is located posterior.
Primary palate is anterior to the incisive foramen, while the secondary palate is posterior to that.
The primary palate is derived from the ______ _____ prominences while the secondary palate is derived from the _______ ______. The nasal septum forms the _________ palate.
Medial nasal prominences;
Palatine shelves;
Definitive palate
The ______ cleft deformity is caused from the incomplete development of the palatine shelves which came from the _____ palate. This deformity is characterized by being able to see the _______ _____ through the roof of the oral cavity.
Posterior cleft, secondary palate;
Open nasal cavity
What cleft deformity forms from the incomplete fusion of the mandibular prominences?
Chin Cleft deformity.
This cleft deformity lies between the lateral nasal prominence and maxillary prominences in the nasolacrimal groove.
Oblique Facial Cleft
The posterior part of the pituitary gland is made of axon terminals from the neurons of the hypothalamus. What is this part called?
This differs from the _________ which is the glandular part made up of the ectodermal diverticulum of the stomodeum.
Posterior Hypophysis;
Adenohypophysis (anterior pituitary)
Describe the structures that the 1st pharyngeal cleft makes. What of the 2nd, 3rd and 4th clefts?
1st cleft = external auditory meatus;
2nd-4th clefts = temporal cervical sinus + lateral cervical cyst (temporary)
What are placodes and how do they relate to the special senses?
Placodes are thickening of surface ectoderm which make up the adult structures that help us perceive senses such as smell (nasal), vision (lens) and hearing/balance (cochlear).
What are the 4 pharyngeal pouches and what do they form?
Pharyngeal pouches are invaginations of endoderm.
1st pouch = inner tympanic membrane, middle ear cavity and auditory tube.
2nd pouch = palatine tonsils (lymphocytic infiltrate)
3rd pouch = inferior parathyroid gland + thymus
4th pouch = superior parathyroid gland + parafollicular cells of thyroid
What is a cause of ectopic parathyroid tissue such as an ectopic thymus?
Improper migration of the 3rd or 4th pharyngeal pouches along a migratory path may lead to this congenital anomaly.
Describe Chromosome 22q11 Deletion.
Aka “DiGeorge Syndrome” this congenital syndrome is marked with immunodeficiency and features including: Cleft palate, Abnormal face, Thymic aphasia, Cardiac defects, Hypocalcemia.
“Catch 22!”
If the thyroglossal duct does not recede during development this would lead to what?
Thyroglossal duct cyst that is movable when the tongue is protruded or an ectopic thyroid.
Define the Foramen cecum and its significance in formation of the thyroid.
The foramen cecum is an evagination near the tongue root. The thyroid diverticulum should descend to the location anterior to the trachea while keeping a constant connection to the foramen cecum through the thyroglossal duct (that should disintegrate).
A person deviates his mandible to the right side while chewing. What muscles are working on the right side, how about the left side of the head?
Right side: masseter and temporalis muscles
Left side: lateral and medial pterygoids
A deviation of the mandible to the left can be caused by a loss of function of the ________ lateral pterygoid muscle or a spasm of the _______ lateral pterygoid muscle.
Left mandible deviation caused from:
loss of left lateral pterygoid OR spasm of right lateral pterygoid.
What is the embryological significance of the ectodermal placodes?
Surface thickenings of the ectoderm in the embryonic head are derivatives of special sensory structures in adults. These include the nasal (smell), lens (sight) and otic (hearing/balance) placodes.
