Thyroid gland and parathyroid THYROID GLAND Introduction Situation

Thyroid gland. and parathyroid

THYROID GLAND Introduction. Situation. Coverings. Parts and relations. Blood supply. Nerve supply. Lymphatic drainage. Applied anatomy.

Butterfly shaped highly vascular endocrine gland Size- 25 gms in wt Shape- H shaped mass Situation Infront and sides of the trachea opposite 5 th, 6 th, 7 th cervical and 1 st thoracic vertebra

COVERINGS - Gland is invested by Inner true capsule. Outer false capsule- Inner true capsulecondensation of fibrous tissue stroma

Outer false capsulepretracheal fascia Tracings. Above-Hyoid bone Oblique line of thyroid cartilage Cricoid cartilage –thickened to form ligament of berry Below –Blends with apex of fibrous pericardium

PARTS AND RELATIONS Two lateral lobes. Isthmus.

LATERAL LOBES L-5 cms, B-3 cms, Thickness 2 cms Shape-Pyramidal shape Parts Apex Base 3 Surfaces 1) Anterolateral 2) Posterolateral 3) Medial Two borders. Anterior Posterior

Apex: Extends to the thyroid cartilage. Related: Superior thyroid artery front. External laryngeal nerve behind Base: Upto the 4 th or 5 th tracheal rings. Related: Inferior Thyroid artery Recurrent Laryngeal nerve.

Antero-lateral surface: Sternohyoid, Sternothyroid, Superior belly of the Omohyoid. Posterolateral surface: Carotid sheath and its contents.

Medial Surface: Trachea and Oesophagus. Cricothyroid and inferior constrictor muscle of pharynx. External and recurrent laryngeal nerves.

Anterior Border. Related to the anterior descending branch of the superior thyroid artery. Posterior Border. Anastomosis between the posterior descending branch of superior thyroid artery and ascending branch of the inferior thyroid artery. Parathyroid gland.

Isthmus: connects both lobes across the midline Vertical and transverse diameter-1. 25 cms Relations. Infront- skin, superficial fascia, investing layer of deep cervical fasia, sternohyoid, sternothyroid Behind-2 nd, 3 rd, and 4 th tracheal rings

Upper border- is related Arterial anastomosis between two superior thyroid artery Pyramidal lobe ocassionally extends from isthmus Fibromuscular band Levator glandulae thyroidae extends from the hyoid bone to the isthmus. Lower border. Inferior thyroid vein Arteria thyroidea ima-Branch from arch of aorta or brachiocephalic trunk

Arterial supply 1)Superior thyroid arterybranch from External carotid artery 2) Inferior thyroid arterybranch from Thyrocervical trunk 3) Arteria thyroidea ima 4) Accessory thyroid arteries- from oesophageal and tracheal branches

VENOUS DRAINAGE veins do not accompany the artery Superior thyrooid vein- drains into Internal jugular vein Middle thyroid vein- drains into internal jugular vein Inferior thyroid vein- drains into left brachiocephalic vein Kocher’s vein-drains into internal jugular vein

Lymphatic drainage -Upper group-Prelaryngeal and jugulodigastric Lower group. Pretracheal and lymphnodes along recurrent laryngeal nerve

NERVE SUPPLYParasympathetic is by vagus and recurrent laryngeal nerve Sympathetic. Superior, middle and inferior cervical ganglia

Applied anatomy- Enlargement of thyroid gland is called as Goitre Hyperthyroidism(thyrotoxicosis) Is due to hyper functioning of the gland 1)Tachycardia 2) Tremors 3) Exophthalamus Hypothyroidism-Hypofunctioning of the gland Myxoedema-in adults Cretinism –in children

PARATHYROID GLAND

PARATHYROID GLAND small yellowish brown lentiform bodies about the size of a split pea Size- L-6 mm, B-3 -4 mm, T 1 -2 mm Number-2 to 6 , (80% of cases -4) arranged as Superior and Inferior para thyroid gland

FUNCTION Secretes Parathormone regulate the level of calcium in the body. Secretory function of the gland are controlled by the level of calcium in the blood. Low level of calcium stimulates and high level will inhibit the gland

SUPERIOR PARATHYROID GLAND 1)fairly constant in position and situated at the posterior border of thyroid gland at the level of cricoid cartilage 2) It lies between the true and false capsule 3) They are developed from the endoderm of fourth phayngeal pouch hence they are called Parathyroid IV.

INFERIOR PARATHYROID GLANDvariable in position 2) It is developed from the endoderm of third pharyngeal pouch and so it is called as parathyroid III.

Blood supplymostly supplied by Inferior thyroid artery or from the anastomosis between superior and inferior thyroid arteries Nerve supply. Sympathetics- are from superior and middle cervical ganglion

Applied anatomy. Hyperparathyroidism-is observed in tumours of the gland. It is characterised by decalcification of the bone, hypercalcaemia, formation of stones in the kidney Hypoparathyroidism-results in tetany which is characterised by hypocalcaemia and increased neuromuscular excitability causing convulsions and carpopedal spasms.

Thank you.