Thyroid and Parathyroid

Question 1

Surface projection of thyroid gland

Answer 1

Description:
• Bilobed endocrine gland
• Composed of pyramidal and lateral lobes
• Connected across midline by isthmus of gland

Function:
• Synthesize and secrete thyroid hormones T3 (triiodothyronine) or T4 (thyroxine)
• Synthesize and secrete calcitonin

Question 2

Surface projection of clavicle

Answer 2

Description:
• S-shaped bone
• Subcutaneous
• Medial end articulates with sternum at sternoclavicular joint
• Lateral end articulates with acromion of scapula at acromioclavicular joint

Also known as:
• Clavicle also known as “collar bone”

Question 3

Hyoid bone

Answer 3

• U-shaped bone
• Paired projections (greater and lesser horns) on each side
Comment:
• Attached structures include stylohyoid ligament, suprahyoid and infrahyoid muscles, and extrinsic tongue muscles
• Does not articulate with any other bone

Question 4

Omohyoid m.

Answer 4

• Depression of hyoid bone
Innervation:
• Ventral rami of C1-3 spinal nerves (ansa cervicalis)

Comment:

Question 5

Pyramidal lobe of thyroid gland

Answer 5

• Extends superiorly from isthmus

Description:
• Pyramidal extension of gland

Function:
• Synthesizes and secretes thyroid hormones T3 (triiodothyronine) and T4 (thyroxine)
• Synthesizes and secretes calcitonin

Question 6

Sternohyoid m.

Answer 6

• Depression of hyoid bone
Innervation:
• Ventral rami of C1-3 spinal nerves (ansa cervicalis)

Question 7

Sternocleidomastoid m.

Answer 7

• Unilateral: rotation of head so face turns to opposite side
• Bilateral: flexion of head
• Accessory nerve (CN XI)

Question 8

Thyroid gland

Answer 8

• Bilobed endocrine gland
• Normally composed of left and right lateral lobes connected across midline by isthmus of gland
• An additional, superiorly-directed, conical pyramidal lobe present 50% of the time
• Follicular cells: synthesize and secrete thyroid hormones T3 (triiodothyronine) and T4 (thyroxine)
• Parafollicular cells: synthesize and secrete calcitonin
• Enlarged thyroid gland known as a goiter, typically due to insufficient dietary iodine

Question 9

Internal jugular v.

Answer 9

Drainage:
• Cranial cavity, including brain
• Face
• Neck
• Enclosed in carotid sheath

Question 10

Common carotid a.

Answer 10

Origin:
• Right: brachiocephalic trunk from arch of aorta
• Left: arch of aorta
• Has no branches before terminal branches
• Enclosed in carotid sheath
• Carotid sheath is a fascial sleeve which contains common and internal carotid arteries, internal jugular vein, vagus nerve (CN X), and lymphatic channels