WINDSOR UNIVERSITY SCHOOL OF MEDICINE

1. WINDSOR UNIVERSITYSCHOOL OF MEDICINE Dr. SREEKANTH THOTA DEPARTMENT OF ANATOMY Neck

2. Viscera • Thyroid and parathyroid glands • PHARYNX • LARYNX

3. Thyroid and parathyroid glands • The thyroid and parathyroid glands are endocrine glands positioned anteriorly in the neck. • Both glands begin as pharyngeal outgrowths that migrate caudally to their final position as development continues. • The thyroid gland is a large, unpaired gland, while the parathyroid glands, usually four in number, are small and are on the posterior surface of the thyroid gland

4. Thyroid gland • The thyroid gland is anterior in the neck below and lateral to the thyroid cartilage. • It consists of two lateral lobes(which cover the anterolateral surfaces of the trachea, the cricoid cartilage, and the lower part of the thyroid cartilage) with an isthmus that connects the lateral lobes and crosses the anterior surfaces of the second and third tracheal cartilages.

5. Thyroid gland in the anterior triangle of neck

6. Arterial supply • Two major arteries supply the thyroid gland. • 1. Superior thyroid artery • 2. Inferior thyroid artery • Thyroid ima artery :Occasionally, a small thyroid ima artery arises from the brachiocephalic trunk or the arch of the aorta and ascends on the anterior surface of the trachea to supply the thyroid gland.

7. Superior and inferior thyroid arteries

8. Thyroid Ima Artery • In approximately 10% of people, a small, unpaired thyroid ima artery arises from the brachiocephalic trunk, however, it may arise from the arch of the aorta

9. Venous and lymphatic drainage • Three veins drain the thyroid gland • 1.Superior thyroid veinprimarily drains the area supplied by the superior thyroid artery; • 2. Middle and inferior thyroid veinsdrain the rest of the thyroid gland. • The superior and middle thyroid veins drain into the IJVs • Inferior thyroid veins drain into the brachiocephalic veins

10. Vasculature of the thyroid

11. Recurrent laryngeal nerves • The thyroid gland is closely related to the recurrent laryngeal nerves. • After branching from the vagus nerve [X] and looping around the subclavian artery on the right and the arch of the aorta on the left, the recurrent laryngeal nerves ascend in a groove between the trachea and esophagus.

12. Injury to the Recurrent Laryngeal Nerves • Right recurrent laryngeal nerve is intimately related to the inferior thyroid artery and its branches. It is more prone to injury during thyroidectomy. • Hoarseness is the usual sign of unilateral recurrent nerve injury; however, temporary aphonia or disturbance of phonation (voice production) and laryngeal spasm may occur.

13. Parathyroid glands • The parathyroid glands are two pairs of small, ovoid, yellowish structures on the deep surface of the lateral lobes of the thyroid gland. • They are designated as the superior and inferior parathyroid glands • Derived from the third (the inferior parathyroid glands) and fourth (the superior parathyroid glands) pharyngeal pouches, these paired structures migrate to their final adult position and are named accordingly.

14. Pharynx • The pharynx is attached above to the base of the skull and is continuous below, approximately at the level of vertebra CVI, with the top of the esophagus. • The walls of the pharynx are attached anteriorly to the margins of the nasal cavities, oral cavity, and larynx. • Based on these anterior relationships the pharynx is subdivided into three regions, the nasopharynx, oropharynx, and laryngopharynx

15. Line of attachment of the pharynx to the base of the skull.

16. Nasopharynx • The nasopharynx is behind the posterior apertures (choanae) of the nasal cavities and above the level of the soft palate. • The most prominent features on each lateral wall of the nasopharynx are: the opening of the pharyngotympanic tube. • There is a large collection of lymphoid tissue (the pharyngeal tonsil) in the mucosa covering the roof of the nasopharynx.

17. Features of the pharynx

18. Oropharynx • The oropharynx is posterior to the oral cavity, inferior to the level of the soft palate, and superior to the upper margin of the epiglottis. • The palatine tonsils are on the lateral walls of the oropharynx.

19. Laryngopharynx • The laryngopharynx extends from the superior margin of the epiglottis to the top of the esophagus at the level of vertebra CVI. • The laryngeal inlet opens into the anterior wall of the laryngopharynx. • There is a pair of mucosal recesses (piriformfossae) between the central part of the larynx and the more lateral lamina of the thyroid cartilage

20. Piriformfossae The piriformfossae form channels that direct solids and liquids from the oral cavity around the raised laryngeal inlet and into the esophagus.

21. Tonsils • Collections of lymphoid tissue in the mucosa of the pharynx surrounding the openings of the nasal and oral cavities are part of the body's defense system.

22. Waldeyer'stonsillar ring The ring consists of (from superior to inferior): • Pharyngeal tonsil (also known as 'adenoids' when infected) • Tubal tonsil (where Eustachian tube opens in the nasopharynx) • Palatine tonsils (commonly called "the tonsils" ) • Lingual tonsils

23. Adenoids • Enlargement of pharyngeal tonsil , known then as adenoids, can occlude the nasopharynx so that breathing is only possible through the oral cavity.

24. Palatine tonsils • The palatine tonsils are visible through the oral cavity just posterior to the palatoglossal folds.

25. Lingual tonsils • The lingual tonsils are rounded masses of lymphatic tissue that cover the posterior region of the tongue.

26. Muscles • The muscles of the pharynx are organized into two groups based on the orientation of muscle fibers. • 1. Constrictor muscles • 2. Longitudinal muscles

27. Constrictor muscles • 1. Superior constrictor • 2. Middle constrictors • 3. Inferior constrictor • Innervation:Vagus nerve [X] • Function: Constriction of pharynx

29. Longitudinal muscles • The three longitudinal muscles of the pharyngeal wall are named according to their origins • 1. Stylopharyngeus • 2. Salpingopharyngeus • 3. Palatopharyngeus • Innervation: All the muscles of pharynx are innerVated by Vagus except stylopharyngeus which is by glassopharyngeal(9th CN) • Function:Elevation of the pharynx

30. LARYNX • The larynx is both a valve (or sphincter) to close the lower respiratory tract, and an instrument to produce sound. • It is composed of: nine cartilages connected by membranes and ligaments and containing the vocal folds.

32. Laryngeal cartilages • The laryngeal skeleton consists of nine cartilages: three are single (thyroid, cricoid, and epiglottic) and three are paired (arytenoid, corniculate, and cuneiform)

33. Thyroid cartilage • It is formed by a right and a left lamina, which are widely separated posteriorly, but converge and join anteriorly. • The most superior point of the site of fusion between the two broad flat laminae projects forward as the laryngeal prominence('Adam's apple'). • The angle between the two laminae is more acute in men (90°) than in women (120°) so the laryngeal prominence is more apparent in men than women.

34. Thyroid cartilage

35. Cricoid cartilage • It is shaped like a 'signet ring' with a broad lamina of cricoid cartilage posterior to the airway and a much narrower arch of cricoid cartilage circling anteriorly.

36. Epiglottis • The epiglottis is a 'leaf-shaped' cartilage attached by its stem to the posterior aspect of the thyroid cartilage at the angle.

37. Arytenoid cartilages • The two arytenoid cartilages are pyramid-shaped cartilages with three surfaces, a base of arytenoidcartilage,apex of arytenoid cartilage, medial surface and anterolateral surface.

38. Corniculate and Cuneiform

39. Intrinsic ligaments • 1. Cricothyroid ligament: • The free margin between the two points of attachment is thickened to form the vocal ligament, which is under the vocal fold (true 'vocal cord') of the larynx.

40. Cricothyrotomy • In emergency situations, when the airway is blocked above the level of the vocal folds, the median cricothyroid ligament can be perforated to establish an airway. • Except for small vessels and the occasional presence of a pyramidal lobe of the thyroid gland, normally there are few structures between the median cricothyroid ligament and skin.

41. Cricothyrotomy

42. Quadrangular membrane • Each quadrangular membrane has a free upper margin and a free lower margin. The free lower margin is thickened to form the vestibular ligamentunder the vestibular fold (false 'vocal cord') of the larynx.

43. Movements of the crico-arytenoid joints.

44. Laryngeal cavity

45. Intrinsic muscles • 1. Cricothyroid: Stretches and tenses vocal ligament • 2. Posterior cricoarytenoid: Abducts vocal folds • 3. Lateral cricoarytenoid: Adducts vocal folds • 4. Transverse arytenoid: adduct • 5. Oblique arytenoid: adduct • 6. Thyro-arytenoid: Relaxes vocal ligament • 7. Vocalis:Relaxes posterior vocal ligament

46. Crico-arytenoid, oblique and transverse arytenoids, and vocalis muscles.

47. Main Action

48. Posterior cricoarytenoid • Paralysis of the posterior cricoarytenoid muscles may lead to asphyxiation as they are the only laryngeal muscles to open the true vocal folds, allowing inspiration and expiration.

49. Important • The cricothyroid muscles are the only intrinsic muscles of the larynx innervated by the superior laryngeal branches of the vagus nerves [X]. • All other intrinsic muscles are innervated by the recurrent laryngeal branches of the vagus nerves [X].

50. Arteries • The major blood supply to the larynx is by the • 1.Superior • 2.Inferior laryngeal arteries