A.24.1 Thyroid Anatomy and Physiology 1 of 2 - Thyroid & Neck PDF

ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck...

ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 1 2 Thyroid & Neck textbook reference A.24 Thyroid & Neck Thyroid Anatomy & Physiology 1 Rumack 5th Edition Thyroid Anatomy & Physiology 2 Chapter 19 Focal Thyroid Disease Chapter 20 Diffuse Thyroid Disease Parathyroids Curry 5th Edition Miscellaneous Neck Pathology Chapter 26 Salivary Glands 3 4 Thyroid Anatomy & Physiology 1 Thyroid 1 Thyroid gland Anatomy & Physiology Thyroid embryology Variants & ectopics Thyroid vasculature Thyroid physiology Cross-sectional anatomy A.24 Thyroid & Neck 5 6 Objectives Key Points By the end of this module you should be able to: Thyroid isthmus is normally inferior to cricoid cartilage State the normal structures seen in the neck with and superior to the sternal notch ultrasound Embryology: develops at base of tongue and descends Identify the normal neck structures from an ultrasound down the midline thyroglossal duct image Variants: pyramidal lobe, ectopia, thyrogossal duct cysts Discuss the physiology of the thyroid gland and its relevance to ultrasound imaging Good vascular supply: veins anterior, arteries posterior Discriminate between normal and abnormal structures in the neck on an ultrasound image 1  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 7 8 Key Points Key Points Physiology: functional unit is the follicle Know the cross sectional anatomy well! * Uses iodine to make T3 and T4, stored in colloid * Trachea * Parafollicular cells make calcitonin (lowers the blood calcium) * CCA/IJV * Hypothalamus-pituitary-thyroid axis: feedback mechanism * Esophagus * Thyroid regulates metabolism * Muscles: Euthyroid, hypothyroid, hyperthyroid SCM, strap, anterior scalenus, longus colli, platysma * NM radioactive iodine can be used to scan and assess Patient positioning: neck extended function of thyroid 9 10 Thyroid Location: Thyroid Anterior to: Inferior to: Superior to: from Greek thyreoeid: shield-shaped 11 12 Thyroid cartilage (Adam’s apple) Cricoid cartilage 2  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 13 14 Thyroid cartilage (Adam’s apple) Cricoid cartilage Thyroid 15 16 Cricothyrotomy Adam’s apple Thyroid location an incision made through the skin and cricothyroid membrane to establish a patent airway during certain life-threatening situations Thyroid cartilage Cricoid cartilage Trachea It’s in the inferior third of the neck 17 18 Thyroid Morphology: 2 main lobes Thyroid Embryology Isthmus ± pyramidal lobe & thyroglossal duct 3  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 19 20 Thyroid Gland Thyroglossal Duct Embryology: embryologic structure Originates at base of tongue an open midline connection between: Migrates inferiorly along midline thyroglossal duct * the initial area of thyroid development in the oropharynx Reaches level of 2nd-4th * The thyroid gland’s final position tracheal rings at 9w GA inferior to the cricoid cartilage Thyroglossal duct should degenerate normally atrophies and closes off before birth may remain open in some people 21 22 Thyroid Variants Pyramidal lobe Thyroid Variants Zuckerkandl tubercle Ectopic thyroid & ectopic thyroid Accessory thyroid Thyroglossal duct cysts * (covered a little later) 23 24 Pyramidal Lobe Thyroid tissue extending Pyramidal Lobe into a persistent portion of inferior thyroglossal duct Most common thyroid variant * ~50% of normals Less prominent with age 4  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 25 26 Levator Muscle of Thyroid Fibrous or muscular band attaching thyroid isthmus Zuckerkandl Tubercle (or pyramidal lobe) to hyoid bone When muscular, it is termed the “levator muscle of thyroid gland” Pulls thyroid superioly during swallowing Swallowing (and also extending the tongue) Note: thyroid always moves with swallowing is a key technique when investigating because it is within pretracheal fascia thyroglossal duct anomalies 27 28 Zuckerkandl Tubercle Zuckerkandl Tubercle AKA posterior thyroid tubercle a projection of normal thyroid tissue from the posterior aspect of the lateral lobes of the thyroid gland Common normal variant Maybe nodular * Mistaken for pathology 29 30 Normal Thyroid Right ZT Nodular Right ZT 5  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 31 32 SCM ZT Rt. lobe IJV CCA ZT Nodular right Zuckerkandl tubercle Much more easily seen with CT…but be aware Transverse right 33 34 Ectopic Thyroid Gland Gland not located in normal Ectopic Thyroid position Uncommon Typically midline & superior 1. Lingual thyroid to normal location (1-4) 2. Intralingual 3. Thyroglossal duct May be more inferior (7) 4. Low neck ectopia 5. Normal position 6. Intratracheal position Rarely intratracheal (6) 7. Mediastinal position Very rarely lateral 35 36 20 y.o. female, ? Enlarged thyroid ?lateral ectopic thyroid tissue 6  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 37 38 Sublingual mass Thyroid Vasculature Hypothyroid No 2-week-old thyroid tissue seen male hypervascular 39 40 Thyroid Blood Supply RIGHT CCA superior thyroid artery * first branch off ECA inferior thyroid artery * from thyrocervical trunk DESCENDING AORTA 2nd Branch off SCA * terminal ends may be seen within Left vertebral artery Aortic arch and inferior aspect of normal thyroid Right vertebral artery the branches you LV need to know thyroid is very vascular On Learn 41 42 Posterior view Superior thyroid artery 1st branch off ECA Superior thyroid artery 1st branch off ECA Inferior thyroid artery from thyrocervical trunk: 2nd branch off subclavian artery 7  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 43 44 Inferior thyroid artery Three pairs of veins: superior, middle and inferior thyroid veins You do NOT need to know the names 45 ANTERIOR VIEW POSTERIOR VIEW 46 Sagittal thyroid lobe ANTERIOR VIEW Veins tend to be Arteries tend to be Inferior thyroid artery & vein more anterior more posterior (just like renals) 47 48 Transverse right thyroid Thyroid Physiology how it works and what it does  Normal colour 8  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 49 50 Thyroid Physiology Thyroid Follicle Endocrine gland Functional unit of the thyroid * Secretes thyroid hormones into bloodstream Follicular cells T3 (Triiodothyronine) * Surround a glob of colloid Regulate metabolism T4 (Thyroxine) * Make thyroid hormones (T3 & T4) Calcitonin Lowers blood calcium Thyroglobulin (colloid) * Stores thyroid hormones Parafollicular cells (C cells) * Make calcintonin 51 52 Thyroid Physiology Thyroid Hormones T3 & T4 Triiodothyronine: regulate metabolism Thyroxine: * metabolism rate Action: * energy levels * internal temperatures T4 (four iodine atoms) * skin/hair/nail growth Calcitonin * etc. Produced by which cells: Molecules contain 3 or 4 iodine atoms Action: * Count the I’s! T3 (three iodine atoms) 53 54 Thyroid Physiology Thyroid Physiology hypothalamus-pituitary-thyroid axis Feedback mechanism questions: Feedback mechanism 1. What would the blood levels of TSH be Hypothalamus: TRH (thyrotropin releasing hormone) like if the thyroid was autonomously Anterior Pituitary: TSH (thyroid stimulating hormone) releasing too much T3 and T4 Thyroid: Thyroid hormones (T3, T4) (hyperthyroid)? 2. What would the TSH be like if the thyroid was autonomously not working properly and releasing too little T3 and T4 (hypothyroid)? 9  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 55 56 What would happen if the patient was iodine deficient? Low T3 & T4 High TRH & TSH Iodine deficiency goiter 57 58 Thyroid Physiology Thyroid Function Tests Term Function Symptoms Euthyroid Normal None Blood work * serum levels of T3, T4, and TSH Slow metabolism, Hypothyroid Decreased weight gain, lethargy, N.M. uptake test (and scan) dry skin, cold * oral radioactive iodine I-123 Fast metabolism, slim, Hyperthyroid Increased hyperactive, sweaty, hot, Normal uptake ~ 15 – 25% (thyrotoxicosis) high heart rate Eu- Prefix meaning well or good 59 60 Cross-Sectional Anatomy lateral → CCA, IJV Cross-Sectional Anatomy medial → trachea, esophagus anatomy adjacent to the thyroid gland anterior → strap muscles posterior → parathyroid glands longus colli muscle minor neurovascular bundle 10  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 61 62 Normal scm sternocleidomastoid m. thyroid gland s strap m. m. v left IJV c left CCA T trachea t right lobe thyroid e esophagus m longus colli m. Esophagus 63 64 Know your anatomy! Practice drawing it 65 66 You can also call any other infrahyoid muscles the “strap” muscles  Quiz yourself! strap muscles nerves VB Left vertebral artery Know all of this 11  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 67 68 1. ________________ node 1. ________________ 2. ________________ Rt. IJV 2. ________________ 3. ________________ nerve 3. ________________ 4. ________________ Rt. CCA 4. ________________ 5. ________________ nerve 5. ________________ 6. ________________ esophagus 6. ________________ 7. ________________ Lt. longus colli 7. ________________ 8. ________________ Lt. ant. scalenus 8. ________________ 9. ________________ Lt. strap m. 9. ________________ 10. ________________ Lt. SCM 10. ________________ 11. ________________ Lt. strap m. 11. ________________ 12. ________________ Lt. strap m. 12. ________________ 13. ________________ trachea 13. ________________ 15.________________ Rt. lobe thyroid 15.________________ 69 70 Minor Neurovascular Bundle The inferior thyroid artery and the recurrent laryngeal nerve Clinical Sonography: A Practical guide by Sanders It lies posterior to thyroid and anterior to longus colli muscle 71 72 Lt. SCM Trachea Thy IJV CCA IJV Rt. Thy Es Ant. Ant. scal. scal. ZT LC LC 12  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 73 74 Transverse SCM Transverse SM Abnormal heterogeneous Abnormal heterogeneous T SM left lobe of thyroid left lobe of thyroid CCA Use landmarks to identify E LC Use landmarks to identify the gland the gland 75 76 strap muscle long long esophagus Abnormal thyroid Abnormal thyroid 77 78 Internal Jugular Vein Internal Jugular Vein Variable size Anterolateral to CCA Proximal valve Long IJV: valve 13  ULTR-3016 Superficial Structures and Vascular Sonography Module A.24: Thyroid & Neck 1 Thyroid Anatomy & Physiology – Part 1 79 Continued in Part 2 Thyroid A&P part 2 14