Head And Neck Session 10 Flashcards
What does the pituitary gland sit within?
Sells turcica
Why is an alternate name for the pituitary gland hypophysis Cerebri?
It is an extension of the cerebrum
What type of embryonic tissue forms the posterior pituitary gland?
Neuroectoderm
What type of embryonic tissue forms the anterior pituitary gland?
Ectoderm
What is Rathke’s pouch?
Outpouching of stomatodeum
Describe the development of Rathke’s pouch.
Grows dorsally, losing connection with oral cavity by the end of the 2nd month
What happens to the anterior wall cells of Rathke’s pouch?
They proliferate rapidly to form the anterior pituitary lobe and pars tuberalis
Describe the growth of pars tuberalis.
From anterior wall cells of Rathke’s pouch growing along stalk of infundibulum to surround it
What happens to the posterior wall cells of Rathke’s pouch?
Form pars intermedia
Does pars intermedia have significance in humans?
No
What is the infundibulum in pituitary gland development?
Downward extension of the diencephalon
In which direction does the infundibulum grow in pituitary gland development?
Down towards the roof of the pharynx
What does the infundibulum form in pituitary gland development?
Posterior lobe and stalk
What are the posterior lobe and stalk of the pituitary made up of?
Neurological cells and nerve fibres from the hypothalamic area
When does the primordia of the pituitary gland arise?
Third week
When does the primordia of the tongue arise?
4th week (at the same time as the palate)
Do all of the pharyngeal arches contribute to the development of the tongue?
Yes
What are the contributions from PA1 to the tongue?
2 lateral swellings and 1 median swelling (tuberculin impar)
Describe the development of the PA1 contributions to tongue development.
2 lateral swellings overgrow tuberculum impar and merge together to form the body of the tongue
What is the cupola in tongue development?
Mesenchyme proliferation from PA2, 3 &4
Describe the development of cupola.
Tissue from PA3 overgrows that of PA2 to form the root of the tongue
What is the contribution of PA4 to the development of the tongue?
Forms epiglottal swelling to create the epiglottis and extreme posterior portion of the tongue
What provides general sensory innervation to the body of the tongue?
CNV3 and glossopharyngeal
What explains the general sensory innervation of the body of the tongue?
The majority of its mucosa comes from PA1&3 therefore cranial nerves associated with these dominate
What gives general sensory innervation to the root of the tongue?
Glossopharyngeal and vagus
What gives general sensory innervation to the epiglottis and extremes posterior part of the tongue?
Superior laryngeal nerve
Why does chorda tympani give special sensory innervation to the body of the tongue despite not being the cranial nerve associated with PA1?
It passes into the arch through the middle ear
What gives special sensory innervation to the root of the tongue?
Glossopharyngeal
Why is the motor innervation of the tongue provided by the hypoglossal nerve?
Intrinsic and extrinsic myogenic precursors arise in occipital somites and migrate to the tongue, taking their innervation with them
What marks the border between the body and root of the tongue?
Sulca terminalis
Where does the primordium of the thyroid gland arise?
In the floor of the pharynx between tuberculum impar and copula
How is the origin of the thyroid gland seen in the adult?
Foramen cecum
Describe the descent of the thyroid primordium.
In front of pharyngeal gut tube, hyoid bone and laryngeal cartilages connected to the tongue by the thyroglossal duct
What does the thyroglossal duct connect?
Isthmus of thyroid with tongue
What forms the pyramidal lobe of the thyroid gland seen in 50% of the population?
Remnant of thyroglossal duct at isthmus
When does the thyroid gland reach its final position?
7th week
When does the thyroid gland become functional?
End of the 3rd month
What provides follicular cells to the thyroid gland?
Thyroid diverticulum
What provides parafollicular cells to the thyroid gland?
Ultimobranchial body of 4th PA
What is a thyroglossal cyst?
Fluid filled pouch found anywhere along the thyroglossal duct due to failure of closure
Where in the neck will a thyroglossal cyst present?
Near or in the midline
Where are 50% of thyroglossal cysts found?
Close of just inferior to the hyoid bone
What is a thyroglossal fistula?
Connection of a thyroglossal cyst to the outside by a fistulas canal
What is a thyroglossal cysts usually secondary to?
Cyst rupture
What is aberrant thyroid tissue?
Functioning thyroid tissue found anywhere along the line of descent that is subject to the same diseases as the thyroid itself
Where is aberrant thyroid tissue commonly found?
Just behind foramen cecum
Why does neural crest cell defects cause both craniofacial and cardiac abnormalities?
They are essential for craniofacial and normal conotruncal endocardial cushion development
What cardiac abnormalities are commonly seen in neural crest cell defects?
Persistent turn us arteriosus, tetralogy of Fallot, transposition of the great vessels
Neural crest cells are a particularly vulnerable population of cells. What are they easily killed by?
Alcohol, retinoic acid
What is Treacher-Collins syndrome?
Autosomal dominant condition causing hypoplasia of the mandible and facial bones, down slanting palpebral fissure, lower eyelid colobomas and malformed external ears
What is the genetic defect in Di-George syndrome?
Deletion of long arm of chromosome 22
Describe the spectrum of disorders seen in Di-George syndrome.
Congenital heart defects, mild facial dysmorphology, learning disabilities and frequent infections
Why do Di-George patients suffer from frequent infections?
Thymic hypo-/aplasia disrupting T-cell mediated responses
Why might hypocalcaemic seizures be seen in Di-George syndrome?
Parathyroid dysfunction due to disruption of endodermal-mesenchymal interaction
What is CATCH-22?
Deletion of long arm of chromosome 22 causing: Cardiac abnormality Abnormal fancies Thymic aplasia Cleft palate Hypocalcaemia/ hypoparathyroidism
What is the defect in CHARGE Syndrome?
CHD7 heterozygous mutation causing impaired production of multipotent neural crest cells
How does CHARGE Syndrome present?
Coloboma, heart defect, atresia of choanae, retardation of growth and development, genital hypoplasia, ear defects
What are the cellular implications for CHARGE syndrome?
Deficiency of mesoderm formation and neural crest cell dysfunction
What is the type of genital hypoplasia seen in CHARGE syndrome?
Hypogonadotrophic hypogonadism
What is the general implication for embryological development in CHARGE syndrome?
Arrest of embryological differentiation in the 2nd month
What is the pharynx?
Muscular tube hanging from the skull to the opening of the oesophagus
What anatomical landmark can be used to identify the opening of the oesophagus?
Cricoid cartilage
What gives motor innervation to the pharynx?
CNVII, IX, X and XII
What provides sensory innervation to the oropharynx?
CNV2
What is the sensory innervation of the oropharynx?
CNIX
What is the sensory innervation to the laryngopharynx?
CNXII
What are the borders of the nasopharynx?
Superior: skull base
Inferior: level of soft palate
Anterior: posterior choanae
Posterior: nasopharyngeal tonsil and C1 vertebral body
What is the function of the nasopharynx?
Condition inspired air
What lines the nasopharynx?
Ciliated stratified squamous epithelium
What are the contents of the nasopharynx?
Nasopharyngeal tonsil, Eustachian tube orifice, tubal tonsil
Where is the tubal tonsil located?
In the submucosa of the lateral wall of the pharynx at the Eustachian tube orifice
What landmark can be used to identify the level of the C1 vertebra?
Hard palate
What landmarks can be used to identify the C2 and C3 vertebral levels?
Angle of mandible and hyoid bone
What landmarks can be used to identify the levels of C4-6 vertebrae?
Upper thyroid cartilage, lower thyroid cartilage, cricoid cartilage
What are the borders of the oropharynx?
Superior: level of soft palate
Inferior: superior edge of epiglottis
Anterior: oral cavity
Posterior: C2 and C3 vertebral bodies
What is the function of the oropharynx?
Digestion
What lines the oropharynx?
Stratified squamous epithelium
What are the contents of the oropharynx?
Palatine tonsils, anterior and posterior pillars
What are the palatine tonsils?
Collections of lymphoid tissue encapsulated by squamous epithelium with crypts that form part of Waldeyer’s ring
What forms the submucosal tonsillar bed of the palatine tonsils?
Superior pharyngeal constrictor and pharyngobasilar fascia
Why do the palatine tonsils not fill the tonsillar sinus in adults?
Due to post-puberty atrophy
What gives innervation to the palatine tonsils?
CNV2 and CNIX
What gives arterial supply to the palatine tonsils?
Tonsillar branch of facial, lingual, ascending palatine and ascending pharyngeal
What gives venous drainage to the palatine tonsils?
Pharyngeal plexus and para tonsillar vein
Where does lymphatic drainage of the palatine tonsils flow?
Pierces superior constrictor to reach jugulo-digastric
What forms the anterior pillar in the oropharynx?
Palatoglossal muscle between the buccal cavity and oropharynx fusing with the lateral wall of the tongue
What forms the posterior pillar in the oropharynx?
Palatopharyngeus muscle blending with the constrictor muscles of the pharynx wall
What gives arterial supply to the pharynx?
Superior thyroid, ascending pharyngeal, ascending and descending palatine, branches of lingual, facial and maxillary
What provides venous drainage to the pharynx?
Pharyngeal venous plexus into the IJV
What are the borders of the laryngopharynx?
Superior: superior edge of epiglottis
Inferior: level of inferior edge of cricoid cartilage
Anterior: larynx
Posterior: C3-6 vertebral bodies
What is the function of the laryngopharynx?
Open inferior to the oesophagus and larynx
What lines the laryngopharynx?
Stratified squamous epithelium
What forms the paoterior and lateral walls of the laryngopharynx?
Externally middle and inferior constrictor muscles, internally Palatopharyngeus and stylopharyngeus
What forms the Piriform fossa?
Ary-epiglottic fold, thyroid cartilage, thyrohyoid membrane
Where is the Piriform fossa located?
Either side of the laryngeal inlet
What is the clinical relevance of the Piriform fossa?
Internal and recurrently laryngeal nerves run deep to it and are vulnerable to damage if a foreign body becomes lodged
What does the median raphe provide?
Point of attachment for constrictor muscles of pharynx
Give the arrangement of the external circular layer of the pharynx from superior to inferior.
Pharyngobasilar fascia, superior constrictor, greater hyoid bone, middle constrictor and inferior constrictor
What are the facial layers of the external circular layer of the pharynx?
Strong internal pharyngobasilar fascia and thin external buccopharyngeal fascia
What is the buccopharyngeal layer of fascia continuous with?
Pretracheal layer of deep cervical fascia
What is the function of the external circular layer muscles in the pharynx?
Sequentially contract involuntarily to propel food to oesophagus
Which muscles form the internal longitudinal layer of the pharynx?
Salpingopharyngeus, Palatopharyngeus and stylopharyngeus
Which structures pass in the gap superior to the superior constrictor muscles of the pharynx?
Levator veli palatini, ET, ascending palatine artery
Which structures pass in the gap superior to the middle constrictor muscles of the pharynx?
Stylopharyngeus, CNIX, stylohyoid ligament
Which structures pass in the gap superior to the inferior constrictor muscles of the pharynx?
Internal laryngeal nerve, superior laryngeal artery and vein
Which structures pass in the gap inferior to the inferior constrictor muscles of the pharynx?
RLN, inferior laryngeal artery
Where is the pharyngeal nerve plexus found?
Lying mainly on middle constrictor
What forms the pharyngeal plexus?
CNIX and X with sympathetic branches from the superior cervical ganglion
What are the 3 phases of swallowing?
Oral, pharyngeal and oesophageal
Describe the oral phase of swallowing.
Voluntary, bolus compressed against palate by tongue and pushed to oropharynx by tongue and soft palate musclature
Describe the pharyngeal phase of swallowing.
Involuntary and soft palate rises to seal of laryngopharynx from naso- and oropharynx whilst the pharynx widens and shortens
What muscles are involved in the pharyngeal phase of swallowing?
Suprahyoid and longitudinal pharyngeal muscles
What is the action of the muscles in the pharyngeal phase of swallowing?
Elevate larynx
Describe the oesophageal phase of swallowing.
Involuntary sequential contraction of all 3 pharyngeal constrictor muscles to create peristaltic ridge
What protects the larynx during swallowing?
Overhanging tongue, epiglottis and vocal cords
What is the problem with the arrangement of the pharynx with respect to the oesophagus and larynx?
Food and air have to cross over in oropharynx to enter correct structure
What do the nasopharyngeal tonsils produce?
IgA, IgG and IgM
When are the adenoids maximal in size?
Between 3 and 8 y.o.
What causes enlargement of the adenoids?
Viral or bacterial infection
What are the consequences of adenoid enlargement?
Nasal obstruction, ET obstruction
What can nasal obstruction lead to?
Mouth breathing causing feeding difficulty, hyponasal speech, snoring, obstructive sleep apnoea
What can ET obstruction lead to?
Recurrent otitis media, chronic otitis media with effusion
What is obstructive sleep apnoea?
Spectrum from mild snoring to OSA due to partial/complete airway obstruction causing turbulent airflow
What are the S/S of OSA?
Daytime tiredness, hypoxia, increased CVS strain
How can the adenoids be visualised?
Post-nasal space X-ray, post-nasal mirror, fibre optic endoscope, in theatre
What are post nasal space X-rays no longer used to visualise the tonsils?
Radiation exposure to children
What are the possible complications of adenoidectomy?
Bleeding, Atlanto-occipital joint dislocation due to infection, ET stenosis
What is the 5-year survival rate for nasopharyngeal carcinoma?
80%
Where are nasopharyngeal carcinomas most commonly found?
Lateral nasopharyngeal recess
What is associated with the undifferentiated form of nasopharyngeal carcinoma?
EBV infection
What are the risk factors for nasopharyngeal carcinoma?
Chinese ancestry, EBV exposure, heavy alcohol intake
What are the S/S of nasopharyngeal carcinoma?
Nasal obstruction, blood-tinged discharge, tinnitus, sore throat, unilateral conductive hearing loss
Does naopharyngeal carcinoma usually present early or late?
Late
How is nasopharyngeal carcinoma managed?
Staged by TNM and treated with radiotherapy (limited role for chemotherapy and surgery)
Why is tonsillectomy no longer carried out as frequently as it was historically?
Disorders of palatine tonsils tend to lessen in severity and frequency as they atrophy with age
What are the indications for tonsillectomy?
Recurrent tonsilitis (5/year in the last 2 years), previous peritonsillar abscess, suspected cancer, OSA
What techniques can be used in tonsillectomy?
Cold steel instruments, guillotine, electrosurgery, diathermy, radio wave
What are the complications associated with tonsillectomy?
General anaesthetic risks, primary and secondary bleeding, infection
Which vessel does primary bleeding in tonsillectomy usually arise from?
Tonsillar branch of facial artery
Which vessel does secondary bleeding in tonsillectomy usually arise from?
External palatine vein
What is pharyngeal pouch?
Relatively rare position herniation of pharyngeal mucosa through Kilian’s dehiscence
Where is Kilian’s dehiscence?
Between superior thyropharyngeus and inferior cricopharyngeus parts of infirm constrictor muscle of pharynx
What is the pathogenesis of pharyngeal pouch?
In swallowing the cricopharyngeus does not relax as the thyropharyngeus contracts causing an increase in intrapharyngeal pressure –> midline true diverticulum
What are the consequences of pharyngeal pouch?
Accumulation of food leading to dysphasia, regurgitation, halitosis,and even aspiration of pouch contents
What population is pharyngeal pouch typically seen in?
Elderly
What causes clinical challenges to the patency of the airway in children compared to the adult?
Head:body ratio, small face and mandible, large tongue and adenoids, soft and short trachea, high SA:weight ratio, lower respiratory reserve, high metabolic rate, complaint chest walls
How can the patency of the airway in children be examined?
Effort of respiration, pallor, cyanosis, haemangioma, auscultation, palpation, flexible nasal endoscopy, microlaryngoscopy, bronchoscopy
What causes the funnel shape of the airway in the child in comparison to the adult?
Narrow and underdeveloped cricoid cartilage
How does acute epiglottis present?
Septic, pyrexia, classic Tripod position: leaning forward and drooling
What are the usually causative agents of acute epiglottitis?
H influenzae, staphylococci, beta-haemolytic streptococci or pneumococci
Which age group does acute epiglottitis typically affect?
2-7 y.o.
How is acute epiglottitis treated?
Secure airway, take bloods and throat swabs, broad spectrum Abx (ceftriaxone) and steroids
What is the pathogenesis of laryngotracheobronchitis (croup)?
Initial viral infection of throat –> infective oedema narrowing subglottis –> harsh (barking) subglottis cough and stridor
How is mild croup treated?
Oral Abx and steam inhalation
How is moderate-severe croup treated?
IV Abx, humidified O2, adrenaline nebuliser
What is the leading cause of death in 1-3 y.o., especially in males?
Foreign body in airway
How does a foreign body in the airway typically present?
Hx of unwitnessed episode of choking, coughing or aging with foreign body –> vague S/S
What does radiology in foreign body in the airway investigation look for?
Opacity of object, segmental/lobar lung collapse, local emphysema and air trapping
How are foreign bodies and associated complications managed?
Remove item by bronchoscopy and use steroid and inhaled bronchodilators if there is oedema as a result
What is laryngomalacia?
Congenital dynamic lesion of laryngeal cartilage causing collapse of supra glottic structures on inspiration resulting in congenital stridor
What is the most common cause of congenital stridor?
Laryngomalacia
What are the Tx options for laryngomalacia?
Conservative or aryepiglottoplasty
