L2 Anatomy of the thyroid gland Flashcards
Describe the dimensions and structure of thyroid gland ?
- Located anterior to the neck
- Extend from C5 to T1
- Made of :
* two lobes anterolateraly to the larynx and trachea
* isthmus Connecting the 2 lobes in front of 2 and 3 tracheal rings
What are the muscles that covers the thyroid ?
It lies deep to
- Sternothyroid
- Sternohyoid
What is the clinical significance of sternothyroid muscle ?
It attaches to thyroid cartilage superiorly so preventing the gland from going up when it will enlarge
What is Pyramidal lobe ? Where it is located ?
About 50% of thyroid gland have a extra lobe ( pyramidal lobe )
It extends from the left lateral aspect of the isthmus
What is the fascia that enclose the thyroid ?
Pretracheal fascia
What is the clinical significance of Pretracheal fascia ?
It attaches to the larynx and trachea, which they move during swallowing
So the thyroid will move also
If there is a swelling that is moving with swallowing, it is the thyroid
What is the Arterial supply? And what is their origin ?
1) Superior thyroid artery (external carotid a)
- superior and anterior
2) Inferior thyroid a. (thyrocervical trunk of Subclavian a.)
- inferior and posterior
- Thyroidima , arises from :
- arch of aorta
- brachiocephalic trunk
- right common carotid
What is the clinical significance of thyroidima ?
Potential source of bleeding during tracheostomy
What is the venous drainage of thyroid ?
Superior, middle , inferior
superior and middle Thyroid vs > Internal Jugular v,
Inferior thyroid v > Brachiocephalic v
What is the Lymphatic drainage ?
1) Prelaryngeal,
2) Pretracheal,
3) Paratrracheal,
4) Inferior deep cervical,
5) brachiocephalic Lymph nodes
What is the Nerve supply to the thyroid gland ?
Superior, middle, and Inferior cervical sympathatic Ganglion (vasomotor)
What is the best site for ligation in case of superior and inferior thyroid artery ?
- Superior thyroid artery with the external laryngeal nerve are away from gland , so its ligation will be to the gland
- inferior thyroid artery with recurrent nerve are near the gland, so artery ligation will be away
What is the colloid ?
large gelatinous protein called thyroglobulin
What is the lining of the follicles ?
Lined by simple squamous to columner (follicular cells or Thyrocytes(T) Has colloid inside (secretory product storeded outside the cell in the colloid).
What is the function of T cells / thyrocytes ?
Release T3 and T4 in response to TSH
What is the function of T3 and T4 ?
important for:
- growth
- cell differentiation
- Control the basal metabolic rate
What are the parafollicular or C cells (C) ?
They are large pale-staining cells that secrete calcitonin, a polypeptide involved with calcium metabolism.
Where you can find parafollicular or C cells (C)?
C cells may be part of the follicular epithelium or present singly or in groups outside of follicles
How calcitonin secretion is regulated ?
Depending on blood Ca concentration ( independent on TSH )
Who you can differentiate between the two types by TEM ?
T cells :
- have microvilli
- have psudopodia
- have junctional complexes
- have RER , GOLGI , lysosomes
C cells :
- cytoplasmic granules containing calcitonin
- RER and GOLGI
What is the clinical significance of the capsule between thyroid and parathyroid ?
It is used as a cleavage plane between the two glands
What is the origin of Follicular cells ?
As epithelial (endodermal) proliferation In the floor of pharynx At foramen cecum
When it will reach the final position?
7th week
When the thyroid will start to function ?
3rd month
What is the origin of Parafolicular cells ?
5 th pharyngeal pouch > Ultimobranchial body
When the cyst develops ?
If the thyroglossal duct is not removed … if open thyroglossal fistula is formed
Where is the most common sites of cyst ?
Superior and inferior to hyoid bone
What are the Ectopic thyroid gland ?
- Lingual thyroid gland.
- Hyoid bone.
- Accessory thyroid glandular tissue: remnants of the thyroglossal duct
What types of cells you have in parathyroid glands ? What are there functions ?
- Supporting/ chief cells
- larger and secrete the hormone (parathyroid hormone ) - Oxyphil cells
- they are lighter in color
What are the capsules that you have it in the thyroid ?
- Outer fibrous capsule > false capsule
2. Inner capsule ( in contact with thyroid gland ) > true capsule