L1: Anatomy of The Thyroid Gland Flashcards
The thyroid gland starts functioning from the β¦β¦ month of intrauterine life.
4th
The thyroid gland is derived from β¦β¦.
- Thyroglossal duct.
- Ultimobranchial body.
- Neural Crest Cells
Origin of Thyroglossal Duct
From the endoderm of the floor of the embryonic pharynx at the foramen cecum.
What is Foramen Cecum?
A midline foramen at the junction of the anterior 2/3 & posterior 1/3 of the developing tongue.
Course of Thyroglossal Duct
Fate of Thyroglossal Duct
Derivateves of Thyroglossal Duct
- The bilobed lower end of the thyroglossal duct gives origin to the follicular cells of the thyroid gland.
Derivatives of Ultimobronchial Body
βCaudal pharyngeal complexβ
Joins each side of the lower end of thyroglossal duct to give origin to parafollicular cells.
Congenital Anomalies of Thyroid Gland
- Ectopic thyroid
- Thyroglossal cyst
- Thyroglossal fistula
what causes ectopic thyroid?
- The thyroglossal duct fails to descend
Site of ectopic thyroid
What causes thyroglossal cyst?
- Persistence of thyroglossal duct
Site of thyroglossal cyst
Presents as midline swelling in the neck.
- Usually it is found in the vicinity of the hyoid bone, So during surgical removal of the cyst the body of hyoid bone is also removed to prevent recurrence.
What causes Thyroglossal fistula?
When the cyst breaks through the skin
- Never congenial
The thyroid gland is a β¦β¦ vascular endocrine gland
highly
Site of Thyroid Gland
Lower part of the front of the neck βin close relation to larynx & tracheaβ
Average Weight of Thyroid Gland
= 25 gm in adult βSlightly heavier in femaleβ
Parts of Thyroid Gland
Extent of Thyroid Gland
Capsule of Thyroid Gland
Has a true capsule (fibrous) and a false capsule (fascial).
Enlarged thyroid gland shifted downward not upward
why?
- The upward shift: is arrested by the attachment of sternothyroid muscle to the oblique line of thyroid cartilage.
- The downward shift: The short neck & strong strap muscles are responsible for pushing the lower pole of a normally located but enlarged gland downward into the superior mediastinum (retrosternal goiter).
what are types of thyroid capsules?
- True capsule (fibrous)
- False capsule (fascial)
Describe True Capsule of Thyroid Gland
- The condensation of the connective tissue at the periphery of the gland
- Completely surrounds the gland.
- The venous plexus lies deep to the true capsule.
Clinical Correlation related to True Capsule of Thyroid Gland
- During surgical removal of the gland, care is taken to remove the gland along with its true capsule to avoid injury to venous plexus.
what is the False capsule (fascial) of thyroid gland derived from?
- Derived from the pretracheal layer of deep cervical fascia.
Attachment of pretracheal fascia
Importance of pretracheal fascia
Responsible for movement of the thyroid gland up with deglutition.