L1: Anatomy of The Thyroid Gland Flashcards

1
Q

The thyroid gland starts functioning from the …… month of intrauterine life.

A

4th

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2
Q

The thyroid gland is derived from …….

A
  • Thyroglossal duct.
  • Ultimobranchial body.
  • Neural Crest Cells
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3
Q

Origin of Thyroglossal Duct

A

From the endoderm of the floor of the embryonic pharynx at the foramen cecum.

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4
Q

What is Foramen Cecum?

A

A midline foramen at the junction of the anterior 2/3 & posterior 1/3 of the developing tongue.

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5
Q

Course of Thyroglossal Duct

A
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6
Q

Fate of Thyroglossal Duct

A
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7
Q

Derivateves of Thyroglossal Duct

A
  • The bilobed lower end of the thyroglossal duct gives origin to the follicular cells of the thyroid gland.
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8
Q

Derivatives of Ultimobronchial Body

β€œCaudal pharyngeal complex”

A

Joins each side of the lower end of thyroglossal duct to give origin to parafollicular cells.

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9
Q

Congenital Anomalies of Thyroid Gland

A
  • Ectopic thyroid
  • Thyroglossal cyst
  • Thyroglossal fistula
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10
Q

what causes ectopic thyroid?

A
  • The thyroglossal duct fails to descend
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11
Q

Site of ectopic thyroid

A
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12
Q

What causes thyroglossal cyst?

A
  • Persistence of thyroglossal duct
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13
Q

Site of thyroglossal cyst

A

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.
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14
Q

What causes Thyroglossal fistula?

A

When the cyst breaks through the skin

  • Never congenial
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15
Q

The thyroid gland is a …… vascular endocrine gland

A

highly

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16
Q

Site of Thyroid Gland

A

Lower part of the front of the neck β€œin close relation to larynx & trachea”

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17
Q

Average Weight of Thyroid Gland

A

= 25 gm in adult β€œSlightly heavier in female”

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18
Q

Parts of Thyroid Gland

A
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19
Q

Extent of Thyroid Gland

A
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20
Q

Capsule of Thyroid Gland

A

Has a true capsule (fibrous) and a false capsule (fascial).

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21
Q

Enlarged thyroid gland shifted downward not upward

why?

A
  • 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).
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22
Q

what are types of thyroid capsules?

A
  • True capsule (fibrous)
  • False capsule (fascial)
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23
Q

Describe True Capsule of Thyroid Gland

A
  • 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.
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24
Q

Clinical Correlation related to True Capsule of Thyroid Gland

A
  • During surgical removal of the gland, care is taken to remove the gland along with its true capsule to avoid injury to venous plexus.
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25
Q

what is the False capsule (fascial) of thyroid gland derived from?

A
  • Derived from the pretracheal layer of deep cervical fascia.
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26
Q

Attachment of pretracheal fascia

A
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27
Q

Importance of pretracheal fascia

A

Responsible for movement of the thyroid gland up with deglutition.

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28
Q

Clinical Correlations of Pretracheal fascia

A
  • Movements of the thyroid during swallowing (deglutition) & speech: due to the attachments of the pretrachel fascia to (Thyroid & cricoid cartilages + Hyoid bone).
  • Retrosternal extension.
  • Compression manifestation of huge goitre.
  • Suspensory ligament of Berry
29
Q

Definition of Suspensory ligament of Berry

A

A thickening of pretracheal fascia.

30
Q

Site of Suspensory ligament of Berry

A

Between Posteromedial aspect of thyroid gland lobe & cricoid cartilage.

31
Q

Importance of Suspensory ligament of Berry

A
32
Q

Each lobe of thyroid gland presents the following

A
33
Q

Relations of Superficial surface of thyroid gland

A
34
Q

Relations of Medial surface of thyroid gland

A
35
Q

Relations of Posterior surface of thyroid gland

A
36
Q

Relations of Anterior Border of thyroid gland

A
  • Related to: The anterior branch of the superior thyroid artery.
37
Q

Relations of Posterior Border of thyroid gland

A

Related to:

  • The parathyroid glands.
  • The anastomosis between the superior & inferior thyroid arteries.
38
Q

Anterior Relations of the Isthmus

A
39
Q

Posterior Relations of the Isthmus

A

It rests on 2nd to (3d or 4th) tracheal rings.

40
Q

Relations to the upper margin of the isthmus

A

The terminal parts of anterior branches of both superior thyroid arteries

  • Take part in a rich anastomosis, which supply twigs to the anterior surface of the isthmus also.
41
Q

Relations to the Lower margin of the isthmus

A
  • The inferior thyroid veins emerge.
  • The thyroidea ima (when present) enters.

These vascular relations of the isthmus are to be kept in mind during tracheostomy.

42
Q

Relations to the Apex of thyroid Gland

A
  • limited by the insertion of the thyrohyoid muscle to the oblique line of the thyroid cartilage.
  • It is related to:
  • The superior thyroid artery.
  • External laryngeal nerve.
43
Q

Relations to the Base of thyroid Gland

A

Related to:

  • Inferior thyroid artery.
  • Recurrent laryngeal nerve.
  • On the left side, it may be related to the arch of the thoracic duct.
44
Q

How to find the thyroid gland lobes?

A
45
Q

How to find the thyroid gland isthmus?

A
46
Q

Arterial Supply of Thyroid Gland

A
  • Pair of Superior thyroid arteries
  • Pair of inferior thyroid arteries
  • The thyroidea ima
  • The accessory thyroid arteries.
47
Q

Where Does the Superior Thyroid Artery Arise from?

A

External carotid artery

48
Q

Course of Superior Thyroid Artery

A
49
Q

Where do Inferior Thyroid Arteries arise from?

A

The thyrocervical trunk of the first part of subclavian artery

50
Q

Course of Inferior Thyroid Arteries

A
51
Q

The …… branch of the inferior thyroid artery anastomoses with the ……. branch of the superior thyroid artery along the posterior margin of the gland.

A

ascending - descending

52
Q

While tying the branches of inferior thyroid artery, its ascending branch supplying the parathyroid glands is always preserved, since it is the main supply of the parathyroid glands.

A

..

53
Q

Where does The thyroidea ima arise from?

A

Arch of aorta or Brachiocephalic trunk

54
Q

Course of The thyroidea ima

A

Ascends in front of the trachea & enters the isthmus.

55
Q

Where do The accessory thyroid arteries arise from?

A

Twigs from esophageal & tracheal branches of inferior thyroid arteries.

56
Q

The thyroid arteries are large-sized and show arterial loops to accommodate the upward & downward movements of the thyroid gland.

A

..

57
Q

Venous Drainage of Thyroid Gland

A
58
Q

Kocher’s Vein

  • Site
  • Opens
A
  • Between the inferior & middle thyroid veins.
  • Opens into the internal jugular vein.
59
Q

Lymphtic Drainage of Thyroid Gland

A
60
Q

Lymphatic spread of papillary carcinoma of the thyroid gland manifests in an interesting way.

Why?

A
  • As the thyroid gland looks normal.
  • But the deep cervical LNs of the jugular chain is enlarged & contains thyroid tissue.
61
Q

NUCLEAR SCAN OF THYROID GLAND

A
62
Q

Study Goiter from Notes

A

..

63
Q

Def of Thyroid Stimulating Abs

A
  • A family of IgG immunoglobulins.
  • Collectively known as Thyroid Stimulating Antibodies (TsAB).
64
Q

MOA of Thyroid Stimulating Abs

A
65
Q

Def of Thyroid Follicles

A

The structural & functional unit of the thyroid gland.

66
Q

General Characters of Thyroid Follicles

A
67
Q

Cells Lining the Thyroid Follicles

A
68
Q

Thyroid Hormone Synthesis

A