5-Thyroid and Parathyroid Glands
Terms
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- What type of gland is the thyroid?
- endocrine
- What do thyroid hormones maintain?
- metabolism of other tissues
- Describe the essentialness of the thyroid.
- it is not essential in adults, but its absence in children leads to mental retardation and dwarfism
- Describe the vasculature of the thyroid.
- highly vascular and has one of the highest blood flow rates per gram of tissue of any organ of the body
- What are the two major lobes of the thyroid? What others are present?
-
right and left lobes
a small pyramidal lobe is present at the isthmus in 40% of individuals - What separates the right and left lobes of the thyroid?
- isthmus
- What is the pyramidal lobe a remnant of?
- the embryonic thyroglossal duct
- What does the thyroid gland develop from? Between what branchial arches?
-
a down growth off the pharynx
between the 1st and 2nd branchial arches - What markes the down growth of the thyroid in the adults?
- the foramen cecum at the apex of the sulcus terminalis marking the anterior 2/3 and posterior 1/3 of the tongue
- Describe the extension of the thyroglossal duct.
- extends down from the foramen cecum over the hyoid bone and down to the seconds tracheal ring
- Where is the site of the adult isthmus?
- at the second tracheal ring
- What is abnormal enlargement of the thyroid called?
- goiter
- What does the thyroid gland wrap around? What holds it in place?
-
trachea and inferior portion of the larynx
pretracheal fascia - Name the two pairs of arteries which supply the thyroid gland.
- superior thyroid areteries and inferior thyroid arteries
- What do the superior thyroid arteries branch from?
- first branch off the external carotid arteries
- What do the inferior thyroid arteries branch from?
- thyrocervical trunk
- What is the occasional third vessel that supplies the thyroid? What does it branch from?
-
thyroid ima artery
directly off the aortic arch - What is the clinical significance of the thyroid ima artery?
- its possible presence is one of the reasons emergency tracheotomies are not done more frequently below the isthmus of the thyroid gland
- Name the three pairs of veins which drain blood from the thyroid.
- superior, middle and inferior thyroid veins
- What do the superior thyroid veins drain into? middle? and inferior?
-
superior-internal jugular
middle-internal jugular
inferior-R&L brachiocephalic veins - Lymph from the thyroid gland generally runs into what?
- superior or inferior deep cervical lymph nodes, or paratracheal lymph nodes
- What restricts blood flow to the thyroid gland?
- sympathetic innervation by the postganglionic sympathetic fibers from the superior, middle and inferior cervical sympathetic ganglia
- What does PTH maintain?
- calcium levels
- How many parathyroid glands are there?
- 4
- Where do the parathyroid glands lie with respect to the thyroid?
- on the inner surface of the thyroid gland
- Which arteries supply the parathyroid?
- inferior thyroid arteries
- What drains the parathyroid?
- thyroid venous plexus
- Lymph from the parathyroid gland flows into what?
- paratracheal or deep cervical lymph nodes
- Is the parathyroid gland neccessary for life? What can occur if it is removed
-
yes
calcium and parathyroid extracts must be given to raise calcium levels, otherwise tetany and ultimately death will occur - What does the thyroid gland develop from?
- a midline pharyngeal outpocketing at the site of the future foramen cecum
- What does the thyroid gland develop between?
- terberculum impar and copula
- Name the important structures formed from pharyngeal outpocketings.
- thyroid, tonsils, tube (eustachian), thymus, and parathyroid
- The pyramidal lobe of the thyroid gland is a remainder of what embryonic development?
- thyroglossal duct
- Where can ectopic thyroid tissue be found?
- in the midline anywhere between the foramen cecum around the hyoid bone and down to the isthmus of the thyroid gland
- What are the boundaries of the root of the neck?
- 1st rib, manubrium sterna and 1st thoracic vertebra
- What does the anterior scalenus muscle insert onto?
- 1st rib
- What artery runs posterior to the anterior scalenus muscle?
- subclavian artery
- Name the branch(es) of the medial subclavian artery.
- vertebral artery, thyrocervical trunk and internal thoracic artery
- Name the branches of the thyrocervial trunk.
- inferior thyroid artery, transverse cervical artery, suprascapular artery
- Name the branch(es) of the posterior subclavian artery.
- costocervical trunk
- Name the branch(es) of the lateral subclavian artery.
- dorsal scapular artery
- What does the vertebral artey supply?
- brain
- What branches from the inferior thyroid artery?
- ascending cervical artery
- What does the transverse cervical artery supply?
- posterior triangle m.
- What does the suprascapular artery travel to?
- scapula m.
- What do the internal thoracic artery go to?
- anterior intercostal art
- What does the costocervial trunch go to?
- intercostal and deep cervical artery
- What does the dorsal scapular artery go to?
- scapula muscles
- What runs anterior to the anterior scalenus muscle?
- phrenic nerve, vagus, and subclavian vein
- What runs posterior to the anterior scalenus muscle?
- subclavian artery and brachial plexus
- What are the three cervical sympathetic ganglia of the sympathetic trunk?
- inferior middle, and superior cervical ganglia
- Where do the inferior cervical ganglion lie? What do they wrap around?
-
at the 1st rib
vertebral artery - What are the inferior cervical ganglion a part of? What else is a part of it?
-
stellate ganglia
superior thorax sympathetic chain ganglia - Where do the middle cervical ganglion lie?
- C6 on the inferior thyroid artery
- Where do the superior cervical ganglion lie?
- C2&3