Thyroid Applied Anatomy, Pysiology, Development with MCQs.pptx
- 1. Tips on using my ppt. 1. You can freely download, edit, modify and put your name etc. 2. Don’t be concerned about number of slides. Half the slides are blanks except for the title. 3. First show the blank slides (eg. Aetiology ) > Ask students what they already know about etiology of today's topic. > Then show next slide which enumerates aetiologies. 4. At the end rerun the show – show blank> ask questions > show next slide. 5. This will be an ACTIVE LEARNING SESSION x three revisions. 6. Good for self study also. 7. See notes for bibliography.
- 2. Learning Objectives At the end of this session we shall be able to describe- • Embryology • Parts • Size and Weight • Relations • Arterial Supply • Venous Drainage • Lymphatic Drainage Of Thyroid. • Nerve Supply • Attachments/Supports • Surface Marking • Microscopic Anatomy • Applied Anatomy • Physiology • Congenital Anomalies
- 3. Anatomy • H- or butterfly-shaped structure • Brownish-red, highly vascular gland • Location: ant neck midline drapes trachea. • Isthmus at C5-T1, overlays 2nd – 4th tracheal rings • Avg width: 12-15 mm (each lobe) • Avg height: 50-60 mm long • Avg weight: 25-30 g in adults (slightly more in women) **enlarges during menstruation and pregnancy**
- 4. Parts •
- 5. Parts • Two Lateral Lobes. • Joined by Isthmus • Occasional Pyramidal Lobe Contains a pyramidal extension on the posterior-most aspect of each lobe, referred to as the tubercle of Zuckerkandl . It is a useful landmark for identifying RLN during thyroidectomy.
- 6. Pyramidal lobe: • Often ascends from the isthmus or the adjacent part of either lobe (usually Left) up to the hyoid bone. • May be attached by a fibrous/fibromuscular band “levator” of the thyroid gland
- 9. Arterial Supply • Superior and Inferior thyroid arteries (occ. thyroidea ima)- 1. Superior thyroid arteries –Ext. Carotid. 2. Inferior thyroid arteries- Thyrocervical trunk from subclavian art. 3. Thyroide ima (when pres) originates from aortic arch or innominate artery.
- 10. Venous Drainage
- 11. Venous Drainage 3 pairs of veins: 1. STV a tributary of the IJV 2. MTV – directly lateral IJV 3. ITV brachiocephalic vein.
- 13. Lymphatics • Extensive, multidirectional flow • Periglandular prelaryngeal (Delphian) pretracheal paratracheal (along RLN) brachiocephalic (sup mediastinum) deep cervical thoracic duct • Regional mets of thyroid carcinoma are superior and lateral, along IJV
- 14. Nerve Supply
- 15. Nerve Supply Principally from ANS • Parasympathetic fibers – from vagus • Sympathetic fibers – from superior, middle, and inferior ganglia of the sympathetic trunk Enter the gland along with the blood vessels.
- 17. Attachments/Supports • Thyroid is enclosed in middle layer of deep cervical fascia. • Ligament attachments: – Anterior suspensory ligament -: attaches the medial superior aspect of the thyroid to the cricoid cartilage and thyroid cartilage – Posterior suspensory ligament (Berry ligament): attaches the posteromedial thyroid to the cricoid cartilage , 1st and 2nd tracheal rings •
- 18. Relations •
- 19. Relations • Lateral: carotid sheath • Anterior - omohyoid muscle - sternohyoid • Sternocleidomastoid • Medial- Larynx, Trachea, Oesophagus • Posterior-Parathyroids, Recurrent laryngeal n. • Posteroinferior to the left lobe: thoracic duct
- 20. Recurrent laryngeal nerve • Branch of the vagus nerve • Innervates all larynx except cricothyroid • Lies in Tracheo-oesophageal groove. • Closely assoc with ITA • Liable to injury when controlling ITA • NB: ‘non recurrent LN’ –directly enters the larynx
- 21. Superior laryngeal nerve • Branch of the vagus nerve • Innervates cricothyroid m. • Two branches: the internal and external laryngeal nerve • Travels with the superior thyroid artery until approximately 1 cm from the gland • Liable to injury when controlling STA
- 22. Parathyroids • 4in number. • Posterior to lobes • Sometimes embedded within thyroid
- 23. Microscopic Anatomy • Thyroid follicles are the structural and functional units of the thyroid glands. Thyroid follicles are composed of a simple epithelial layer that encloses a colloid-filled cavity. • C cells- Also known as clear, light, or parafollicular cells.
- 24. Applied Anatomy
- 25. Applied Anatomy • Various nerves are at potential risk for injury during thyroidectomy- 1. Recurrent laryngeal nerve - vocal cord paralysis 2. Superior laryngeal nerve -dysphonia 3. Cervical sympathetic trunk. -Horner syndrome 1. Drooping of the eyelid 2. Constricted pupil (miosis) and 3. Decreased sweating on the affected side of the face (anhidrosis). • Removal of parathyroid glands or damage to its blood supply - transient or permanent hypoparathyroidism and consequential hypocalcemia.
- 26. Embryology •
- 27. Embryology • Starts @24th day of gestation • From two main structures:- 1. Thyroid diverticulum- median anlage, 2. Ultimobronchial bodies – Left and Right -- lateral anlage
- 28. Development of Thyroid • The thyroid gland originates from the endoderm between the 1st and 2nd pharyngeal pouches. • From Foramen cecum, which is a pit positioned at the posterior one-third of the tongue. • Then descends in front of the pharyngeal gut as a bilobed diverticulum . • During migration, the thyroid remains connected to the tongue by a narrow canal, the thyroglossal duct.
- 29. Development of Thyroid • The ultimobranchial body, derived from the ventral region of the fourth pharyngeal pouch, then becomes incorporated into the dorsal aspect of the thyroid gland • Parafollicular cells are derived from ultimobranchial body. • Ramnant is tubercle of Zuckerkandl .
- 31. Congenital anomalies • Ectopic thyroid • Thyroglossal duct Cyst • The persistence of the thyroglossal duct. • Thyroglossal fistula • The partial degeneration of the thyroglossal duct. • Pyramidal Lobe • Agenesis of Isthmus • Agenesis of thyroid.
- 32. Ectopic thyroid • Most cases of ectopic thyroid are detected in early childhood • May be associated with hypothyroidism. • The tissue may enlarge due to an elevation of thyroid-stimulating hormone (TSH), resulting in localized symptoms. • May be mistaken for a TDC. It is important to differentiate between these lesions, as THS-related enlarged tissue is frequently the only thyroid tissue present.
- 33. Ectopic thyroid Failed or incomplete descent • Lingual • Sublingual • Suprahyoid • Subhyoid Occasionally the thyroid descends beyond its normal station into the superior mediastinum • Retrosternal thyroid. • Sub diaphragmatic organs.
- 34. Thyroglossal duct cyst • Thyroglossal duct does not atrophy • These cysts are the most common congenital cervical anomalies • Presents as a painless, asymptomatic midline swelling. • Located anywhere from the thyroid cartilage up to the base of the tongue, along the embryonic course of descent
- 35. Thyroglossal duct cyst • Cysts are smooth, round, well-defined, and slightly mobile on physical exam. • Although most are observed during childhood, they can present at any age. • Classically move with protrusion of the tongue and swallowing due to their physical attachment to the hyoid bone and muscles of the tongue
- 36. Thyroglossal duct cyst: Treatment • The Sistrunk procedure • Because the hyoid bone develops in an anterior direction and may surround the thyroglossal duct, the surgeon should resect the central portion on the hyoid bone along with the cyst.
- 37. Physiology
- 38. Physiology • The five steps of thyroid hormone synthesis- 1. Synthesis of Thyroglobulin 2. Iodide uptake 3. Iodination of thyroglobulin 1. Oxidation 2. Organification 3. Coupling reaction: 4. Storage 5. Release
- 39. Hormones Epithelial cells = 2 types: • Principal (ie: follicular) – formation of colloid (iodothyroglobulin) • Parafollicular (ie: C cells -clear, light), lie adjacent to follicles w/in basal lamina produce calcitonin
- 41. Normal Physiology • TSH stimulates secretion of T4 and T3 from thyroid • Most serum T3 produced by deiodination of T4 • Think of T3 as active hormone and T4 as prohormone • Only small fraction total T4 and total T3 is unbound – therefore free and active
- 42. ACTIONS OF T3 T4 • Thyroid hormone affects virtually every organ system in the body- – The heart, – CNS, – Autonomic nervous system – Bone – GI – Metabolism.
- 43. ACTIONS OF T3 T4 • Increases the basal metabolic rate • Depending on the metabolic status, it can induce lipolysis or lipid synthesis. • Stimulate the metabolism of carbohydrates • Anabolism of proteins. Thyroid hormones can also induce catabolism of proteins in high doses. • Permissive effect on catecholamines
- 44. ACTIONS OF T3 T4 • In children, thyroid hormones act synergistically with growth hormone to stimulate bone growth. • CNS During the prenatal period, it is needed for the maturation of the brain. In adults, it can affect mood. • Thyroid hormone affects fertility, ovulation, and menstruation.
- 45. ACTIONS of Calcitonin • Calcitonin acts to decrease serum calcium concentrations by- • Decreasing osteoclast activity. • Inhibiting the reabsorption of calcium by the kidney.
- 47. PATHOPHYSIOLOGY • thyroid hormone secretion leads to hyperthyroidism • What you see in this is called: thyrotoxicosis. • Thyroid hormone secretion leads to hypothyroidism
- 48. Hyperthyoidism vs Thyrotoxicosis. • Hyperthyroidism is a set of disorders that involve excess synthesis and secretion of thyroid hormones by the thyroid gland. • In thyrotoxicosis, thyroid hormone levels are elevated with or without increased thyroid hormone synthesis- 1. Hyperthyroidism 2. Excess intake of levothyroxine or 3. Temporary excess release of thyroid hormone due to sub acute thyroiditis.
- 49. Thyroid Function Tests T3,T4,TSH • Serum Thyroid-Stimulating Hormone (Normal 0.5–5 U/mL): Serum TSH levels reflect the ability of the anterior pituitary to detect free T4 levels. Small changes in free T4 lead to a large shift in TSH levels (Inverse relation). • Total T4 (Reference Range 55–150 nmol/L) and T3 (Reference Range 1.5–3.5 nmol/L). • Free T4 (Reference Range 12–28 pmol/L) and Free T3 (3–9 pmol/L). • Thyroid Antibodies : Thyroid antibodies include anti-Tg, antimicrosomal, or anti-TPO and thyroid-stimulating immunoglobulin (TSI).
- 50. Thyroid Function Tests • TSH is used as screening test .
- 51. MCQ Thyroid is enclosed in which layer of cervical fascia- • A. Superficial cervical fascia • B. The superficial layer of deep cervical fascia • C. The middle layer of deep cervical fascia (visceral layer) • D. The deep layer of deep cervical fascia
- 52. MCQ Thyroid is enclosed in - • A. Superficial cervical fascia • B. The superficial layer of deep cervical fascia • C. The middle layer of deep cervical fascia (visceral layer) • D. The deep layer of deep cervical fascia
- 53. MCQ • During total thyroidectomy a set of nerves supplying the sympathetic fibers to the gland is damaged. Which of the following manifestation would most likely be seen in the patient- A. Vocal cord paralysis B. Dysphonia C. Horner syndrome D. Transient hypoparathyroidism
- 54. MCQ A. Vocal cord paralysis B. Dysphonia C. Horner syndrome D. Transient hypoparathyroidism
- 55. MCQ • Which of the following conditions marked by the low TSH? a) Hypothyroidism b) Goitre c) Hyperthyroidism d) Thyroid Cancer
- 56. MCQ • Marked by the low TSH? a) Hypothyroidism b) Goitre c) Hyperthyroidism d) Thyroid Cancer
- 57. MCQ • Which Organ that basically regulates and controls the actual activity of thyroid? a) Pituitary gland b) Hypothalamus c) Both A and B
- 58. MCQ • Organ that basically regulates and controls the actual activity of thyroid a) Pituitary gland b) Hypothalamus c) Both A and B
- 59. • Lectures one drive
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