L2 Anatomy of the thyroid gland Flashcards

1
Q

Describe the dimensions and structure of thyroid gland ?

A
  1. Located anterior to the neck
  2. Extend from C5 to T1
  3. Made of :
    * two lobes anterolateraly to the larynx and trachea
    * isthmus Connecting the 2 lobes in front of 2 and 3 tracheal rings
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2
Q

What are the muscles that covers the thyroid ?

A

It lies deep to

  • Sternothyroid
  • Sternohyoid
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3
Q

What is the clinical significance of sternothyroid muscle ?

A

It attaches to thyroid cartilage superiorly so preventing the gland from going up when it will enlarge

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4
Q

What is Pyramidal lobe ? Where it is located ?

A

About 50% of thyroid gland have a extra lobe ( pyramidal lobe )
It extends from the left lateral aspect of the isthmus

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5
Q

What is the fascia that enclose the thyroid ?

A

Pretracheal fascia

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6
Q

What is the clinical significance of Pretracheal fascia ?

A

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

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7
Q

What is the Arterial supply? And what is their origin ?

A

1) Superior thyroid artery (external carotid a)
- superior and anterior

2) Inferior thyroid a. (thyrocervical trunk of Subclavian a.)
- inferior and posterior

  1. Thyroidima , arises from :
    - arch of aorta
    - brachiocephalic trunk
    - right common carotid
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8
Q

What is the clinical significance of thyroidima ?

A

Potential source of bleeding during tracheostomy

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9
Q

What is the venous drainage of thyroid ?

A

Superior, middle , inferior

superior and middle Thyroid vs > Internal Jugular v,

Inferior thyroid v > Brachiocephalic v

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10
Q

What is the Lymphatic drainage ?

A

1) Prelaryngeal,
2) Pretracheal,
3) Paratrracheal,
4) Inferior deep cervical,
5) brachiocephalic Lymph nodes

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11
Q

What is the Nerve supply to the thyroid gland ?

A

Superior, middle, and Inferior cervical sympathatic Ganglion (vasomotor)

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12
Q

What is the best site for ligation in case of superior and inferior thyroid artery ?

A
  1. Superior thyroid artery with the external laryngeal nerve are away from gland , so its ligation will be to the gland
  2. inferior thyroid artery with recurrent nerve are near the gland, so artery ligation will be away
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13
Q

What is the colloid ?

A

large gelatinous protein called thyroglobulin

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14
Q

What is the lining of the follicles ?

A

Lined by simple squamous to columner (follicular cells or Thyrocytes(T) Has colloid inside (secretory product storeded outside the cell in the colloid).

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15
Q

What is the function of T cells / thyrocytes ?

A

Release T3 and T4 in response to TSH

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16
Q

What is the function of T3 and T4 ?

A

important for:

  • growth
  • cell differentiation
  • Control the basal metabolic rate
17
Q

What are the parafollicular or C cells (C) ?

A

They are large pale-staining cells that secrete calcitonin, a polypeptide involved with calcium metabolism.

18
Q

Where you can find parafollicular or C cells (C)?

A

C cells may be part of the follicular epithelium or present singly or in groups outside of follicles

19
Q

How calcitonin secretion is regulated ?

A

Depending on blood Ca concentration ( independent on TSH )

20
Q

Who you can differentiate between the two types by TEM ?

A

T cells :

  • have microvilli
  • have psudopodia
  • have junctional complexes
  • have RER , GOLGI , lysosomes

C cells :

  • cytoplasmic granules containing calcitonin
  • RER and GOLGI
21
Q

What is the clinical significance of the capsule between thyroid and parathyroid ?

A

It is used as a cleavage plane between the two glands

22
Q

What is the origin of Follicular cells ?

A

As epithelial (endodermal) proliferation In the floor of pharynx At foramen cecum

23
Q

When it will reach the final position?

A

7th week

24
Q

When the thyroid will start to function ?

A

3rd month

25
Q

What is the origin of Parafolicular cells ?

A

5 th pharyngeal pouch > Ultimobranchial body

26
Q

When the cyst develops ?

A

If the thyroglossal duct is not removed … if open thyroglossal fistula is formed

27
Q

Where is the most common sites of cyst ?

A

Superior and inferior to hyoid bone

28
Q

What are the Ectopic thyroid gland ?

A
  1. Lingual thyroid gland.
  2. Hyoid bone.
  3. Accessory thyroid glandular tissue: remnants of the thyroglossal duct
29
Q

What types of cells you have in parathyroid glands ? What are there functions ?

A
  1. Supporting/ chief cells
    - larger and secrete the hormone (parathyroid hormone )
  2. Oxyphil cells
    - they are lighter in color
30
Q

What are the capsules that you have it in the thyroid ?

A
  1. Outer fibrous capsule > false capsule

2. Inner capsule ( in contact with thyroid gland ) > true capsule