Flashcards in Head and Neck Session 11 Deck (86):
how does the post. lobe of pituitary arise?
from developing brain: downgrowth from diencephalon forms in midline= infundibulum, and extends down towards roof of oral cavity,
name given to downgrowth of diencephalon from which P lobe of pituitary arises?
how is floor of hypothalamus formed?
from part of diencephalon giving rise to infundibulum
what name is given to connection between floor of hypothalamus and infundibulum forming P lobe of pituitary?
name given to outpushing from roof of oral cavity which grows up to meet forming infundibulum?
what may form from persitent remnants of Rathke's pouch in the roof of the pharynx from where it split off from the ectoderm from which it was derived?
how do the tongue and thyroid gland arise from pharyngeal arches?
from where they meet as they curve around lateral walls of mouth and pharynx, meeting in the midline ventrally
which 3 components form the anterior 2/3 of the tongue?
median tongue bud from floor of pharynx at level of 2nd pharyngeal arch- facial nerve
paired distal tongue buds form in front of median bud and eventually overgrow and absorb it. originate from 1st pharyngeal arch- trigeminal nerve
which 2 components form posterior 1/3 of tongue?
copola- forms in midline from 2nd pharyngeal arch
hypobranchial eminence- forms from 3rd and 4th arches behind copola. Expands and absorbs copola, forming post 1/3 tongue (3rd arch- glossopharyngeal nerve) and epiglottis (4th arch)
what is seen in adult at site of fusion of A and P parts of tongue?
muscles of tongue are NOT derived from pharyngeal arches. where do they arise from?
small somites (paraxial mesoderm) which arise in occipital region and migrate into developing tongue
name given to site of origin of thyroid?
name of epithelial outgrowth in 4th wk that gives rise to thyroid?
where is the foramen cecum?
between 1st and 2nd pharyngeal arches, behind median tongue bud
on descent, how does the thyroid remain attached to the foramen cecum?
via the thyroglossal duct
what may form as a remanant of the distal end of the thyroglossal duct?
pyramidal lobe of thyroid
the foramen cecum closes off, but how is it seen in adult?
indentation on dorsum of tongue
calcitonin producing cells of thyroid originate from where?
4th pharyngeal pouch-ventral part
most common site for thyroglossal cysts?
base of tongue and just inferior to hyoid
most common site of ectopic thyroid tissue due to failure of thyroid to descend normally?
when might the isthmus of the thyroid need to be incised?
during a tracheostomy to expose the trachea to keep the airway patent
what is the nasopharynx attached to superiorly?
base of skull
the wall of the pharynx has an outer incomplete circular muscle layer, and an inner longitudinal layer, what 3 muscles comprise the inner layer?
stylopharyngeus-from 3rd arch
the 3 named tonsils comprising the incomplete ring of lymphoid tissue in the pharynx?
palatine- between palatoglossal and palatopharyngeal ridges
adenoids (pharyngeal)- near roof of nasopharynx close to ET entry
lingual- beneath mucosa of P 1/3 of tongue
how is food forced into oesophagus?
by automatic contraction of the 3 pharyngeal constrictor muscles
which muscles contract to elevate the larynx during swallowing?
longitudinal pharyngeal muscles= stylopharyngeus, palatopharyngeus, salpingopharyngeus
2 important structures vulnerable to injury in tonsillectomy?
arterial b.supply to tonsil?
tonsillar branch of facial artery
common site where FBs entering pharynx may become lodged?
what does the posterior wall of the pharynx lie against?
prevertebral layer of deep cervical fascia
what does the nasopharynx lie superior to?
what may a pharyngeal pouch (diverticulum of zenker) in the pharynx cause?
regurgitation of food
what nerve plexus supplies the pharynx and what does it comprise?
pharyngeal branches of vagus, glossopharyngeal, and sympathetoc branches from S.cervical ganglion
sensory innervation to nasopharynx?
maxillary division of trigeminal
how does the uvula look if tonsillitis?
central and inflamed
how does the uvula look if peritonsillar abscess?
pushed to 1 side
what is the anatomical location of the pituitary gland?
sits in the pituitary (hypophyseal) fossa in the sella turcica= a saddle shaped depression in the sphenoid bone
where does Rathke's pouch arise?
out-pocketing of ectoderm of the stomatodeum, evagination of roof of oropharynx, grows dorsally towards developing forebrain
how is the tongue capable of being highly mobile?
due to the lingual frenulum= short cord attaching tongue to oral cavity
importance of tongue being highly mobile?
necessary for mastication and speech
what do the intrinsic and extrinsic muscles of tongue allow?
tongue can change its shape and position
what does the tongue develop from?
components of each of the pharyngeal arches
what swellings does the 1st pharyngeal arch give rise to which contribute to the tongue
2 lateral lingual swellings
1 median lingual swelling= tuberculum impar
the copula/hypo-branchial eminence, a second median swelling, is formed from the mesoderm of what?
the 2nd, 3rd and 4th pharyngeal arches
how does the 4th pharyngeal arch contribute to tongue development?
contributes to the formation of 2 of the 3 median lingual swellings: the copula, and the epiglottal swelling which will form the epiglottis
how does the tongue become freed from the floor of the oral cavity?
extensive degeneration occurs by apoptosis: programmed cell death, but the tongue still retains a connection to the oral cavity via the lingual frenulum
what happens as the lateral lingual swellings increase in size?
they overgrow the tuberculum impar and merge, forming the anterior 2/3 of the tongue
why is sensory innervation to the posterior 1/3 of the tongue mainly from the glossopharyngeal nerve based in development?
the 3rd pharyngeal arch component of the copula overgrows the 2nd arch component
what is the innervation to the extreme posterior part of the tongue and the epiglottis?
superior laryngeal branch of vagus nerve due to development from the 4th pharyngeal arch which forms the epiglottal swelling and small contribution to the copula
most tongue musculature develops from occipital somites, hence what is its innervation?
general sensory innervation to anterior 2/3 of tongue and why?
mandibular division of trigeminal (lingual nerve)
as mucosa originates from 1st pharyngeal arch (gave rise to 2 lateral lingual swellings which overgrow the tuberculum impar- a median lingual swelling)
how does taste sensation of anterior 2/3 of tongue come to derive from the chorda tympani nerve?
the nerve passes into the 1st pharyngeal arch from the second, passing through the 1st pharyngeal pouch and hence travels through the middle ear
between which 2 swellings of the developing tongue does the primordium of the thyroid gland appear between?
the tuberculum impar and the copula
from where does the thyroid gland descend into the neck?
floor of the pharynx
where are the follicular cells of the thyroid gland derived from?
the thyroid diverticulum: an epithelial proliferation in the floor of the pharynx between the tuberculum impar and the copula which descends in front of the pharyngeal gut., the hyoid bone and laryngeal caritlages, and stays connected to tongue on migration by thyroglossal duct
what part of the 4th pharyngeal pouch gives rise to the parafollicular cells of the thyroid?
ventral part, the ultimobranchial body
in what region of the neck do thyroglossal cysts occur, in contrast to branchial cysts?
midline of neck
branchial occur more laterally along SCM
why does CATCH22 occur with Di-George syndrome?
deletion on chromosome 22 responsible for disruption of neural crest cells
C- cardiac abnormalities- neural crest cells contribute to devlopment of CVS e.g. endocardial cushions and separation of PA and aorta?
A- abnormal facies- neural crest cells populate mesenchyme forming prominences giving rise to face
T- thymic hypoplasia/aplasia- thymus derived from 3rd pharyngeal pouch and neural crest cells contribute the mesenchyme into which the endoderm from pharyngeal pouches migrates, the mesenchyme makes the CT necessary for gland differentiation
C- cleft palate- failure of 1 or both palatal shelves to grow towards the midline and/or fuse with its partner
H- hypocalcaemia- absence of PT glands which secrete PTH which stimualtes Ca2+ release from bone, reabsorption by kidneys and absorption from gut via calcitriol
boundaries of nasopharynx?
inferior= level of soft palate
anterior= posterior choanae
posterior= adenoids= C1
vertebral level of oropharynx?
vertebral level of laryngopharynx?
boundaries of oropharynx?
superior= level of soft palate
inferior= superior edge of epiglottis
anterior= oral cavity
boundaries of laryngopharynx?
superior= superior edge of epiglottis
inferior= lower border of cricoid cartilage
posterior= C3-C6 vertebrae
contents of nasopharynx?
opening of eustachian tube
contents of oropharynx?
anterior and posterior tonsillar pillars (palatoglossal and palatopharyngeal arches)
lymphatic drainage of palatine tonsils?
lymphatics pierce superior constrictor muscle of outer incomplete circular layer of pharyngeal muscles
pass to nodes along IJV (terminal LNs)
jugulodigastric node (angle of mandible)
how are constrictor muscles of pharynx attached posteriorly (open anteriorly) ?
importance of soft palate elevation in swallowing?
closes off nasopharynx so food not regurgitated through nose
indications for a tonsillectomy?
recurrent tonsillitis (5 per yr for at least 2 yrs)
previous peritonsillar abscess (quinsy)
suspected cancer (unilateral enlargement/ulcertation)
risks during tonsillectomy?
vertebral level of hard palate?
vertebral level of angle of mandible?
vertebral level of hyoid bone?
vertebral level of upper and lower borders of thyroid cartilage?
C4 and C5
vertebral level of cricoid cartilage?
muscle which must relax for food to enter oesophagus?
describe the mechanism of swallowing
Pushing food from oral cavity to oropharynx: tongue and suprahyoid muscles (mylohyoid, geniohyoid, digastric and stylohyoid) pull hyoid and larynx up, soft palate elevates closing off nasopharynx and superior constrictor pharyngeal muscles contract.
Food bolus passes into hypopharynx by aid of middle an d inferior constrictors
cricopharyngeus relaxes, allowing food to enter oesophagus after being funneled into upper part by piriform fossa
what is the larynx protected by in swallowing?
lining of oropharynx and laryngopharynx?
stratified squamous non-keratinized epithelium
how is peristalsis aided by arrangement of pharyngeal musculature?
constrictor muscles overlap each other and so contract in a downward fashion
pharyngeal arterial b.supply?
ECA: branches of lingual, facial and maxillary arteries, ascending and descending palatine artery, ascending pharyngeal artery, superior thyroid artery
venous blood drainage pharynx?
pharyngeal venous plexus to IJV
motor nerve supply to pharynx?
sensory supply to laryngopharynx?
presentation of patient with enlarged adenoids?
hyponasal speech- high pitched
recurrent acute otitis media- earache
chronic otitis media with effusion- glue ear- reduced hearing