Thyroid Gland- Gross Anatomy by Dr. Rabia Inam Gandapore.pptx

Thyroid Gland

1. Thyroid Gland Dr. Rabia Inam Gandapore Assistant Professor Head of Department Anatomy (Dentistry-BKCD) B.D.S (SBDC), M.Phil. Anatomy (KMU), Dip. Implant (Sharjah, Bangkok, ACHERS) , CHPE (KMU),CHR (KMU), Dip. Arts (Florence, Italy )

2. Teaching Methodology LGF (Long Group Format) SGF (Short Group Format) LGD (Long Group Discussion, Interactive discussion with the use of models or diagrams) SGD (Short Group) SDL (Self-Directed Learning) DSL (Directed-Self Learning) PBL (Problem- Based Learning) Online Teaching Method Role Play Demonstrations Laboratory Museum Library (Computed Assisted Learning or E-Learning) Assignments Video tutorial method

3. Goal/Aim (main objective) To help/facilitate/augment the students about the: Describe location & extent of thyroid gland. Briefly explain capsules of thyroid. Explain parts & relations of thyroid gland. Describe blood, nerve & lymphatic supply of thyroid gland .

4. Specific Learning Objectives (cognitive) At the end of the lecture the student will able to: Describe location & extent of thyroid gland. Briefly explain capsules of thyroid. Explain parts & relations of thyroid gland. Describe blood, nerve & lymphatic supply of thyroid gland.

5. Psychomotor Objective: (Guided response) A student to draw labelled diagram of the Thyroid Gland

6. Affective domain To be able to display a good code of conduct and moral values in the class. To cooperate with the teacher and in groups with the colleagues. To demonstrate a responsible behavior in the class and be punctual, regular, attentive and on time in the class. To be able to perform well in the class under the guidance and supervision of the teacher. Study the topic before entering the class. Discuss among colleagues the topic under discussion in SGDs. Participate in group activities and museum classes and follow the rules. Volunteer to participate in psychomotor activities. Listen to the teacher's instructions carefully and follow the guidelines. Ask questions in the class by raising hand and avoid creating a disturbance. To be able to submit all assignments on time and get your sketch logbooks checked.

7. Lesson contents Clinical chair side question: Students will be asked if they know what is the function of Thyroid Gland Outline: Activity 1 The facilitator will explain the student's Thyroid Gland Activity 2 The facilitator will ask the students to make a labeled diagram of the Thyroid Gland Activity 3 The facilitator will ask the students a few Multiple Choice Questions related to it with flashcards.

8. Recommendations Students assessment: MCQs, Flashcards, Diagrams labeling. Learning resources: Langman’s T.W. Sadler, Laiq Hussain Siddiqui, Snell Clinical Anatomy , Netter’s Atlas , BD Chaurasia’s Human anatomy, Internet sources links.

9. Thyroid Gland Named after the thyroid cartilage ( Greek: Shield shaped) L argest endocrine gland Serous acini Situated: -Below: external auditory meatus -Deep & behind: ramus of mandible - I nfront of: Sternocledomastoid muscle. Salivary Glands: Paired Parotid gland , Sub-mandibular, Sub-lingual glands & numerous small glands scattered in oral cavity.

10. Developmental Embryology 1st endocrine gland to develop Endodermal thickening primitive pharynx ---thyroid primordium - --descend in neck---ventral to hyoid, laryngeal cartilage- -- connection by thyroglossal duct 1st hollow than solid---divide into 2 — connected by isthmus At 7 week has definitive shape---reach final site Foramen cecum- -- persistance proximal opening of thyroglossal duct

11. Structure Of Thyroid Gland Extensions of capsule within the substance of gland form numerous setae , which divide it into lobes & lobules Each Lobule contains 40 to 60 thyroid follicles & stroma in which blood vessels & lymphatic ramify. Thyroid Follicle structural units of gland -- filled-- colloid thyroglobulin as storage. Follicle is surrounded by a single layer of epithelial cells.

12. Histology Epithelial cells are of 2 types : Principal cells ( i.e .,follicular ): formation of colloid Parafollicular cells (i.e . C-clear , light cells ): hormone calcitonin depending on the state of activity, the cells are flattened with colloid abundant (resting state) or cuboidal (secretory state) with colloid diminished

13. Site /Location/Topography Is anterior in neck below & lateral to thyroid cartilage D eep to: sternothyroid & sternohyoid muscles Present in visceral compartment of neck surrounded by pretracheal fascia E xtending from level of C5-T1 Isthmus: overlying the second to fourth tracheal rings

14. Shape, Weight & Size Shape: wedge shape (H or U) 25-30g Lobe : 50-60 mm long Isthmus: average height of 12-15 mm Normal gland has Consistency of muscle tissue

15. Parotid Duct Parotid Duct: passes forward over lateral surface of masseter muscle (One finger below zygomatic arch). At anterior border of muscle, it turns sharply medially & pierce buccal pad of fat & buccinator muscle . It then passes forward for a short distance between muscle & mucous membrane and finally opens into vestibule of mouth on small papilla , opposite upper second molar tooth . The oblique passage of duct forward between the mucous membrane & buccinators serve as a valve-like mechanism & prevents inflation of duct system during violent blowing (e.g. as in glass blowing or trumpet playing) A ccessory part of gland: drained by small duct that opens into upper border of parotid duct .

16. Coverings (Capsule) Lobulated mass surrounded by connective tissue capsule & dense fibrous capsule A. True Capsule: Surrounded by a inner true thin, fibrous capsule of connective tissue which adheres closely to gland Extensions of this capsule within the substance of gland form numerous septae , which divide it into lobes & lobules B. False Capsule: External to this is a “false capsule ” formed by pretracheal fascia of cervical fascia

17. Attachment Above: P retracheal fascia is attached to hyoid bone & thyroid cartilage on each side Below: it enters thoracic cavity & blends with fibrous pericardium of heart P retracheal fascia is thickened to form the ligament of Berry which connects each lobe of thyroid with cricoids cartilage (of larynx). These attachments of thyroid gland make it move up & down with swallowing .

18. Parts Facial nerve & its branches pass forward within parotid gland divides it into: Superficial Part Deep Part or Lobes A. Two lateral lobes RT & LT (Pyramidal) B. Two S uperior & Inferior poles C. Connected by narrow Isthmus -( ant surface of 2 & 3 tracheal cartilage ) -average height of 12-15 mm D. In some people a third “pyramidal lobe ” exists , ascending from isthmus towards hyoid bone

19. Lateral Lobes APEX (behind angle of Mandible) U pward , sandwiched between inferior constrictor (of pharynx) & sternothyroid muscles. Superior thyroid artery & external laryngeal nerve closely related A rtery lies superficial N erve passes deep to apex so ligated away from thyroid gland during surgery. BASE (above) Extends up to 5, 6 Tracheal ring R elated to inferior thyroid artery & recurrent laryngeal nerve . RLN either anteriorly or posteriorly to ITA,artery is ligated away laterally to gland to avoid injury to RLN SUPERFICIAL SURFACE is overlapped by neck muscles DEEP SURFACE related with larynx, trachea , pharynx, oesophagus & parathyroid glands .

20. Processes of Gland Superior Margin of Gland: extends upward behind TMJ into posterior part of mandibular fossa called Glenoid Process Anterior Margin of Gland: extends forward superficial to masseter muscle to for F acial P rocess . Small part of facial process maybe separate from the main gland called Accessory Par of gland . Deep part of Gland: extend forward between medial pterygoid muscle & ramus of mandible to form P terygoid Process

21. Structures within Parotid Gland From Lateral to Medial are: Facial nerve: Emerges from stylomastoid foramen & enters gland. It passes forward superficial to retromandibular vein & external carotid artery & divided into 5 terminal branches . The branches of nerve leave gland on its antero -medial surface. Retromandibular vein: formed within parotid gland by union of superficial temporal & maxillary vein . Divides into anterior & posterior divisions , which leave lower border of gland . Anterior division join facial vein & posterior division unites with posterior auricular vein to form external jugular vein External Carotid Artery: having left carotid triangle by passing deep to posterior belly of diagastric ascends & enters the substance of parotid gland. At the level of the neck of mandible, it divides into superficial temporal artery & maxillary artery Lymph nodes

22. Relations of Parotid Gland (Parotid Bed) 3. Postero -medial Relations: Mastoid Process Sternocleidomastoid muscle Posterior belly of digastric muscle Styloid process & its attached muscles Carotid sheath (Internal carotid artery, Vagus , Internal Jugular vein, glossopharyngeal, accessory, hypoglossal & facial nerves) 4. Antero-medial Relations: Posterior border of ramus of mandible Masseter Medial Pterygoid muscle TMJ 1. Superficial Relations: Skin Fascia Parotid lymph nodes Great auricular nerve 2 . Superior Relations: External auditory meatus Posterior surface TMJ At union of Antero & Postero - Medial gland lies in contact with pharyngeal wall

23. Arterial Supply Highly vascular ( External carotid artery & terminal branches) a. Superior T hyroid Arteries b. Inferior T hyroid Arteries c. Occasionally T hyroidea I ma , branch of arch of aorta or bracheocephalic trunk d. Accessory thyroid arteries , from oesophageal & tracheal branche These arteries lie between the true capsule & pretracheal layer of deep cervical fascia

24. a. Superior Thyroid Artery First anterior branch of external carotid artery D escend to superior pole divides into anterior & posterior branches after piercing pretracheal fascia. a. Anterior branch: supplies anterior surface both sides anastomose across midline b. Posterior branch: supplies posterior surface anastomose with inferior thyroid artery . High ligation of superior thyroid artery during thyroidectomy places this nerve at risk of inadvertent injury, which would produce dysphonia by altering pitch regulation

25. b. Inferior Thyroid Artery I nferior thyroid-- thyrocervical -- subclavian artery A scends vertically curves medially to enter the tracheoesophageal groove in a plane posterior to carotid sheath--- penetrate posterior aspect of lateral lobe C losely associated with recurrent laryngeal nerve

26. Venous Drainage Drains into retromandibular vein V eins do not accompany the arteries A rise from venous plexus which is present deep to true capsule & are drained by 3 pairs of veins: Superior thyroid veins: drain superior pole of gland Middle thyroid veins: drain middle of lobe Inferior thyroid veins: drain inferior pole of gland

27. Venous Drainage 3 pairs of veins Superior thyroid vein : (superior thyroid artery )--internal jugular vein Middle thyroid vein: directly--internal jugular vein Inferior thyroid vein- --- brachiocephalic vein occationally inferior veins form a common trunk called thyroid ima vein , which empties into left brachiocephalic vein

28. Lymphatic Drainage Drains into Parotid & Deep cervical lymph nodes Extensive & flows multidirectionally : Accompanying arteries & form a capsular network of lymphatic vessels. L ymphatic vessels: Periglandular nodes--- to prelaryngeal ( Delphian )--- pretracheal ---- paratracheal nodes along recurrent laryngeal nerve- -- to mediastinal ---deep cervical LN--- brachiocephalic lymph nodes or thoracic duct Regional metastases of thyroid carcinoma--- laterally, higher in neck along internal jugular vein , tumor invasion of pretracheal & paratracheal nodes causing an obstruction of normal lymph flow.

29. Innervation A. Vasomotor: from ANS. Vasomotor & cause constriction of blood vessels Parasympathetic fibers : come from vagus nerves . B. Secretomotor 1 . Parasympathetic fibers : Parasympathetic secretomotor fibers from inferior salivary nucleus of glossopharyngeal nerve supply parotid gland Pre-ganglionic parasympathetic Nerve fiber pass to otic ganglion via tympanic branch of glossopharyngeal nerve & lesser petrosal nerve . Post-ganglionic parasympathetic fibers reach parotid gland via auriculotemporal nerve which lies incontact with deep surface of gland 2. Sympathetic fibers : are distributed from superior , middle, & inferior ganglia of sympathetic trunk Post ganglionic sympathetic fibers reach gland as plexus of nerves around external carotid artery

30. Endocrine Function Regulated by pituitary gland ,TSH . T hyroid hormone , controls rate of metabolism & calcitonin , controlling calcium metabolism . Thyroid gland affects all areas of body except itself, spleen, testes, & uterus

31. Clinical Correlation

32. Clinical Corelation Thyroid Ima Artery Potential source of bleeding “Tracheostomy,” Thyroglossal Duct Cyst Normally disappears-- remnants of epithelium may remain -- form a thyroglossal duct cyst at any point along path of its descent U sually in neck, close or just inferior to hyoid, F orms a swelling in anterior part of neck

33. Aberrant Thyroid Gland F ound anywhere along path of embryonic thyroglossal duct. Uncommon At root of tongue: posterior to foramen cecum , resulting in lingual thyroid gland i n neck at or just inferior to hyoid

34. Accessory Thyroid Glandular Tissue Portions of thyroglossal duct may persist to form thyroid tissue. appear anywhere

35. Enlargement Of Thyroid Gland N on- neoplastic,non -inflammatory enlargement GOITER , which results from a lack of iodine S welling in neck- -may compress trachea, esophagus & recurrent laryngeal nerves Enlarge gland extend anteriorly, posteriorly, inferiorly, or laterally NOT superiorly because of superior attachments of overlying sternothyroid & sternohyoid muscles Substernal extension of goiter is also common

36. Parotid gland infection Acutely inflamed: retrograde bacterial infection from mouth via parotid duct Gland may be infected via bloodstream i.e Mumps Gland swollen, painful because fascial capsule derived from investing layer of deep cervical fascia is strong & limits swelling of gland Swollen glenoid process which extends medially behind TMJ is responsible for pain experienced in acute parotitis when eating

37. Frey’s Syndrome Develops after penetrating wounds of parotid gland When patient eats, beads of perspiration appears on skin covering parotid caused by damage to auriculotemporal & great auricular nerves During process of healing, parasympathetic secretomotor fibers in auriculotemporal nerve grow out & join distal end of great auricular nerve Eventually these fibers reach sweat glands in facial skin By thus means a stimulus intended for saliva production produces sweat secretion instead

38. Thyroidectomy Benign parotid neoplasm rare, cause facial palsy Malignant tumor of parotid invasive & involves facial nerve causing unilateral facial paralysis Excision of malignant tumor of thyroid gland, Necessitates removal of part or all of gland ( hemi-thyroidectomy or thyroidectomy). In surgical treatment of hyperthyroidism , posterior part of each lobe of enlarged thyroid is usually preserved, procedure called near-total thyroidectomy , to protect recurrent & superior laryngeal nerves & to spare parathyroid glands.

39. Injury to Recurrent Laryngeal Nerves E ver present during neck surgery Near inferior pole of thyroid gland, the right recurrent laryngeal nerve is intimately related to i nferior thyroid artery & its branches ligated some distance lateral to thyroid gland, where it is not close to nerve Hoarseness is usual sign of unilateral recurrent nerve injury; temporary aphonia or disturbance of phonation (voice production) & laryngeal spasm may occur . Signs result from bruising the recurrent laryngeal nerves during surgery or from pressure of accumulated blood & serous exudate after operation. To avoid injury to external branch of the superior laryngeal nerve superior thyroid artery is ligated & sectioned more superior to gland , its not as closely related to nerve Voice monotonous

40. Parotid Duct Injury Superficial structure: Can be damaged in injuries to face of during surgical operations on face Duct 2inches (5cm) long & passes forward across masseter about fingerbeneath below zygomatic arch. It pierces buccinators muscle to enter mouth opposite upper second molar tooth

41. Thank You