Muscular Triangle: Thyroid Gland Flashcards

1
Q

Site

A
  1. Dark red endocrine gland lying in lower part of neck front
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2
Q

Content

A

Consists of 2 pyramidal shaped lobes connected by an intermediate band (isthmus) which lies over 2nd, 3rd, and 4th tracheal rings

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3
Q

Extent

A

Each lobe extends from thyroid cartilage oblique line (lobe apex) till 5th or 6th tracheal rings (lobe base)

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4
Q

Relations Isthmus

A
  1. Skin
  2. Deeply
  3. At upper border
  4. At lower border
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5
Q

Relations Isthmus: superficial

A
  1. Skin
  2. Fascia
  3. Anterior jugular veins
  4. Sternohyoid
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6
Q

Relations Isthmus: deep

A

2nd, 3rd, 4th rings

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7
Q

Relations Isthmus: at upper border

A

Anastomosis between 2 superior thyroid arteries

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8
Q

Relations Isthmus: at lower border

A

Beginning of inferior thyroid veins and termination of thyroidea ima artery

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9
Q

Relations thyroid lobe (3 surface)

A
  1. Anterolateral surface
  2. Posterior surface
  3. Medial surface
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10
Q

Anterolateral surface

A
  1. Skin
  2. Superficial fascia (contains Platysma
  3. Deep investing fascia
  4. Sternomastoid
  5. Sternohyoid
  6. Sternothyroid
  7. Pretracheal fascia
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11
Q

Posterior surface

A
  1. Parathyroid glands (superior and inferior)
  2. Medial part carotid sheath
  3. Inferior thyroid artery
  4. Prevertebral muscles and fascia
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12
Q

Medial surface

A

Above:
1. Larynx
2. Pharynx
3. External laryngeal nerve
Below:
1. Trachea
2. Esophagus
With recurrent laryngeal nerve in between

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13
Q

Arterial blood supply

A
  1. Superior thyroid artery
  2. Inferior thyroid artery
  3. Thyroidea ima artery:
    - may be absent
    - from aortic arch to isthmus
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14
Q

Superior thyroid artery site and course

A
  1. From ECA anterior aspect below to of hyoid greater horn
  2. Descends downwards and forwards (closely related to external laryngeal nerve which supplies circothyroid) deep to infrahyoid muscles towards gland apex
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15
Q

Superior thyroid artery end

A

Divides into terminal anterior and posterior branches

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16
Q

Superior thyroid artery branches

A
  1. Infrahyoid artery
  2. Superior laryngeal artery
  3. Muscular branches
  4. Glandular branches (anterior and posterior)
17
Q

Infrahyoid artery

A

Runs alone hyoid lower border anastomosing with opposite artery

18
Q

Superior laryngeal artery

A

Pierces thyrohyoid membrane with internal laryngeal to supply larynx

19
Q

Muscular branches

A
  1. Sternomastoid
  2. Circothyroid
20
Q

Glandular branches

A

Upper 1/3 lobe (including apex) and upper 1/2 isthmus

21
Q

Inferior thyroid artery course

A
  1. Ascends alone scalenus anterior medial border until C6 transverse process
  2. It curves medial in front of vertebral artery and behind carotid sheath to reach thyroid gland posterior surface
  3. Finally descends reaching gland inferior pole (closely related to recurrent laryngeal nerve which supplies all larynx muscles except circothyroid and larynx mucosa below vocal cords)
22
Q

Venous blood supply

A
  1. Superior thyroid vein
  2. Middle thyroid vein
  3. Inferior thyroid vein
23
Q

Superior thyroid vein

A

From apex to IJV

24
Q

Middle thyroid vein

A

Very short
From lobe to IJV

25
Q

Inferior thyroid vein

A

From isthmus to brachiocephalic vein

26
Q

Inferior thyroid artery branches

A
  1. Ascending cervical artery: in front of scalenus anterior
  2. Inferior laryngeal artery
  3. Tracheal and esophageal arteries
  4. Glandular branches: supply lower 2/3 of lobe (including base) and lower 1/2 isthmus and parathyroids
27
Q

Lymphatic drainage

A
  1. Prelaryngeal
  2. Pretracheal
  3. Paratracheal
  4. Deep cervical
    Lymph nodes
28
Q

Nerve supply

A

Sympathetic from superior, middle, and inferior cervical sympathetic ganglia reaching gland around superior and inferior thyroid arteries

29
Q

Applied anatomy: goiter

A

Thyroid enlargement
May extend inside thoracic cavity behind sternum (retrosternal goiter) causing:
1. Dyspnea
2. Venous congestion

30
Q

Applied anatomy: manipulation of superior thyroid artery during thyroidectomy

A

May cause injury of external laryngeal nerve

31
Q

Applied anatomy: manipulation of inferior thyroid artery during thyroidectomy

A

May cause injury of recurrent laryngeal nerve

32
Q

Applied anatomy: how to avoid injury of external laryngeal nerve

A

Superior thyroid artery should be lighted as near as possible to gland (even within gland apex)

33
Q

Applied anatomy: how to avoid injury of reccurent laryngeal nerve

A

Ligation of inferior thyroid artery should be as far as possible from the gland base

34
Q

Applied anatomy: injury of laryngeal nerves

A

May lead to:
1. Hoarseness of voice
2. Aphonia
3. Suffocation
According to injury degree

35
Q

Applied anatomy: parathyroid glands

A
  1. During thyroidectomy, gland posterior part in which parathyroid glands embedded should be left
  2. Removal of parathyroids during surgery may lead to:
    - hypocalcemia
    - tetany