Muscular Triangle: Thyroid Gland

Question 1

Site

Answer 1

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

Question 2

Content

Answer 2

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

Question 3

Extent

Answer 3

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

Question 4

Relations Isthmus

Answer 4

1. Skin
2. Deeply
3. At upper border
4. At lower border

Question 5

Relations Isthmus: superficial

Answer 5

1. Skin
2. Fascia
3. Anterior jugular veins
4. Sternohyoid

Question 6

Relations Isthmus: deep

Answer 6

2nd, 3rd, 4th rings

Question 7

Relations Isthmus: at upper border

Answer 7

Anastomosis between 2 superior thyroid arteries

Question 8

Relations Isthmus: at lower border

Answer 8

Beginning of inferior thyroid veins and termination of thyroidea ima artery

Question 9

Relations thyroid lobe (3 surface)

Answer 9

1. Anterolateral surface
2. Posterior surface
3. Medial surface

Question 10

Anterolateral surface

Answer 10

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

Question 11

Posterior surface

Answer 11

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

Question 12

Medial surface

Answer 12

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

Question 13

Arterial blood supply

Answer 13

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

Question 14

Superior thyroid artery site and course

Answer 14

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

Question 15

Superior thyroid artery end

Answer 15

Divides into terminal anterior and posterior branches

Question 16

Superior thyroid artery branches

Answer 16

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

Question 17

Infrahyoid artery

Answer 17

Runs alone hyoid lower border anastomosing with opposite artery

Question 18

Superior laryngeal artery

Answer 18

Pierces thyrohyoid membrane with internal laryngeal to supply larynx

Question 19

Muscular branches

Answer 19

1. Sternomastoid
2. Circothyroid

Question 20

Glandular branches

Answer 20

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

Question 21

Inferior thyroid artery course

Answer 21

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)

Question 22

Venous blood supply

Answer 22

1. Superior thyroid vein
2. Middle thyroid vein
3. Inferior thyroid vein

Question 23

Superior thyroid vein

Answer 23

From apex to IJV

Question 24

Middle thyroid vein

Answer 24

Very short
From lobe to IJV

Question 25

Inferior thyroid vein

Answer 25

From isthmus to brachiocephalic vein

Question 26

Inferior thyroid artery branches

Answer 26

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

Question 27

Lymphatic drainage

Answer 27

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

Question 28

Nerve supply

Answer 28

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

Question 29

Applied anatomy: goiter

Answer 29

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

Question 30

Applied anatomy: manipulation of superior thyroid artery during thyroidectomy

Answer 30

May cause injury of external laryngeal nerve

Question 31

Applied anatomy: manipulation of inferior thyroid artery during thyroidectomy

Answer 31

May cause injury of recurrent laryngeal nerve

Question 32

Applied anatomy: how to avoid injury of external laryngeal nerve

Answer 32

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

Question 33

Applied anatomy: how to avoid injury of reccurent laryngeal nerve

Answer 33

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

Question 34

Applied anatomy: injury of laryngeal nerves

Answer 34

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

Question 35

Applied anatomy: parathyroid glands

Answer 35

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