Presentation on theme: "Functional Anatomy of the Thyroid & Parathyroid Glands Innervation of the Pharynx & Larynx Dr James Peerless June 2011."— Presentation transcript:
1Functional Anatomy of the Thyroid & Parathyroid Glands Innervation of the Pharynx & Larynx Dr James PeerlessJune 2011
2Objectives The Thyroid Gland The Parathyroid Gland Pharynx & Larynx AnatomyEndocrine functionThe Parathyroid GlandCa2+ metabolismPharynx & LarynxInnervation
3The Thyroid Gland Largest endocrine gland in the body Origin Originates from the floor of pharynxThyroglossal duct sometimes persists in adultsLargest endocrine gland in the bodyAffects basal metabolic rate via the thyroid hormones: control CHO, protein metabolism, and influence growth, maturation and body temperatureOriginates from floor of the pharynxThyroglossal duct marks path of gland from the base of the tongue to its final site
4The Thyroid Gland Relations Deep to sternothyroid and sternohyoid musclesLevel of C5 –T1Bilobular; joined by the isthmusAnterolateral to the larynx and trachea (2nd & 3rd rings)Bound by a loose connective tissue capsule which is anchored to the cricoid cartilage and tracheal ringsUpper and lower pole
5Supplied by superior and inferior thyroid arteries Highly vascularSupplied by superior and inferior thyroid arteriesDrainage via superior, middle and inferior thyroid veins2+3Superior thyroid artery is commonly the first branch of the external carotidInferior thyroid artery originates from the thyrocervical trunk (from the subclavian artery).10% of people have the unpaired thyroid ima artery – supplied directly from the aorta or the common carotid a. – important when planning tracheostomies as it runs arteriorly along the trachea.Sup. and middle drain into IJV, inf. into the brachiocephalic veins
6The Thyroid Gland Nerve Supply Derived from superior, middle and inferior cervical sympathetic ganglia (from the sympathetic trunk)Fibres are vasomotorNo secretomotor parasympathetic innervation: the gland is hormonally regulated
7Ectopic glandsAccessory tissuePyramidal lobePerseveration of the thyroglossal duct
8Functional Anatomy of Thyroid Follicular structure lined by epithelial cellsAlter shape depending on amount of activityContain colloidParafollicular ‘C’ cellsSecrete calcitonin
10Thyroid Hormone Synthesis Function of the follicular cells:Thyroglobulin production (protein containing 123 tyrosine residues) forms the colloidthyroid peroxidase synthesisstorage of T3 and T41 iodide ions actively transported into the follicular cells from the plasma – 20-40x concentration2 iodide ions reduced to iodine in the colloid by TP and combined with tyrosine to form MIT or DIT.3 DIT/MIT combine to form T3/T4/thyroglobulin complex.4 passes back into the follicular cell until released into the blood.
11The Parathyroid Glands Four disc-like glands, embedded in the thyroid gland (dorsal surface)Contain two cell types:Chief cells producing PTHOxyphil cells: function unknownEssential for maintenance of normocalcaemia – important as Ca2+ act as secondary messengers, blood coag., nerve impulse transmission, muscle contractionFour disc-like glands, embedded in the thyroid gland – two in each of the upper and lower polesMost people have 4 glands – 5% have more.Blood supply is most commonly provided by the inferior thyroid arteries (but can be any).
13Parathyroid Hormone Polypeptide produced in the chief cells Preprohormone Prehormone PTHIncreases Ca2+ via three main actions:ResorptionReabsorptionAbsorptionResorption: mobilization of Ca2+ from bone (clasts and blasts)Increased reabsorption from the distal tubule (and reduced reabsorption of PO42- in the proximal tubules)Increased production of 1,25 dihydroxycholecalciferol increased absorption of Ca2+ from the small intestineControlled by negative feedback loop.
15The PharynxExternal circular – constrictors (superior, middle and inferior constrictors)Internal longitudinal – elevate the larynx and shorten the pharynx during speaking and swallowing – stylopharyngeus, salpingopharyngeus, palatopharyngeusAnterior connections such as the mandible, hyoid and larynx – and join at the posterior midline raphe.
16The Pharynx Nerve Supply Pharyngeal plexus provides motor and most of sensoryMotor:All muscles – fibres from nucleus ambiguus of the accessory nerve carried via the vagus nerveStylopharyngeus – CN IXTensor veli palatini - CN V3Lower pharynx also receives some motor fibres from recurrent laryngeal nerveSensory:Glossopharyngeal (CN IX) – most of mucosaMaxillary (CN V2) – anterior nasopharynxVagus (CN X)Branches from the cervical sympathetic chain
21ReferenceSmith T, Pinnock C, Lin T (2009). Fundamentals of Anaesthesia, 3rd Edition. Cambridge: Cambridge University PressMoore K, Dalley A (1999). Clinically Oriented Anatomy, 4th Edition. Philadelphia: Lippincott Williams & Wilkins