Download Lecture 11: Thyroid and Suprarenal (Adrenal) Glands: Learning

Lecture 11: Thyroid and Suprarenal (Adrenal) Glands:
 Learning Objectives
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Identify the anatomy of the thyroid glands including arterial and venous supply, nerve supply and lymphatic drainage
Identify the anatomy of the parathyroid glands including arterial and venous supply, nerve supply and lymphatic drainage
Identify the anatomy of the suprarenal (adrenal glands) including arterial and venous supply, nerve supply and lymphatic
drainage
Identify manifestations and diagnosis of common disorders of the suprarenal (adrenal) glands including Adrenocorticoid
hyperfunction (Cushing’s syndrome) and Adrenal insufficiency (Addison’s disease)
Thyroid Gland:
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Body’s largest endocrine gland
Produces thyroid hormone (controls rate of
metabolism)
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Produces calcitonin (controls calcium
metabolism)
Affects all areas of the body except the
spleen, testes, and uterus
 Muscles Covering The Thyroid
 Infra-Hyoid (Strap) muscles cover the 2 lobes of the Thyroid, specifically:
 Sterno-thyroid and sterno-hyoid muscles
 Sternocleidomastoid overlaps the strap muscles.
 Thyroid Gland Enlargement
 Goiter: a non-neoplastic and noninflammatory enlargement of the thyroid gland
 Results from lack of iodine
 Common in parts of the world where soil & water are iodine-deficient
 Enlarged gland causes a swelling in the neck that can compress the trachea, esophagus, and recurrent
laryngeal nerves
 Gland can enlarge anteriorly, posteriorly, inferiorly, or laterally
 not superiorly because of the superior attachments of the sternothyroid and sternohyoid muscles
 Thyroid Gland Location
 C5-T1
 Right & left lobes
 Thin isthmus unites the lobes over the trachea
 Anterolateral to larynx and trachea
 Surrounded by a thin fibrous capsule that sends septa deep into the gland
 Dense connective tissue attaches capsule to cricoid cartilage and superior tracheal rings
 Thyroid Gland Arteries
 Supplied by superior and inferior thyroid arteries, with extensive anastomosis
 Superior:
 Usually the first branches of the external carotid arteries
 Descend to the superior poles of the thyroid, pierce the pretracheal layer of deep cervical fascia
 Divide into anterior and posterior branches supplying mainly anterosuperior thyroid
 Inferior:
 Largest branches of thyrocervical trunks arising from subclavian arteries
 Run superomedially, branch, and pierce the pretracheal layer of deep cervical fascia
 Supply posterioinferior thyroid
 Thyroid Ima Artery
 Small, unpaired thyroid ima artery arises from brachiocephalic trunk in ~10% of people
 Or, can arise from arch of aorta, right common carotid, subclavian, or internal thoracic arteries
 Ascends on anterior surface of trachea, continues to isthmus of thyroid gland – divides & supplies
 Presence must be considered when performing midline neck procedures inferior to the isthmus because it
is a potential source for bleeding
 Tracheotomy
 Retract infrahyoid muscles
 Incision of isthmus of thyroid
 Incision of trachea
 Thyroid Veins
 Three pairs of veins form a thyroid plexus of veins on the anterior surface of thyroid gland
 Superior thyroid veins accompany superior thyroid arteries and drain the superior poles
 Middle thyroid veins run parallel to inferior thyroid arteries; drain middle of lobes
 Superior & middle drain into the IJV
 Inferior thyroid veins traverse alone and drain the inferior poles
 Drains into brachiocephalic veins posterior to the manubrium
 Lymphatic Drainage of Thyroid
 Thyroid lymphatic vessels run in the interlobular connective tissue, usually near the arteries
 Vessels pass to prelaryngeal, pretracheal, and paratracheal lymph nodes
 Prelaryngeal nodes drain to superior cervical lymph nodes
 Pretracheal and paratracheal nodes drain to inferior deep cervical nodes
 Laterally, lymphatic vessels along the superior thyroid veins pass directly to inferior deep cervical lymph
nodes
 Some lymphatic vessels may drain into the brachiocephalic lymph nodes or the thoracic duct
 Thyroid Nerves
 Derived from the superior, middle, and inferior cervical (sympathetic) ganglia
 Reach the gland through the cardiac, superior, and inferior thyroid periarterial plexuses that accompany
the thyroid arteries
 Fibers are VASOMOTOR (control the size of blood vessels - by their effect on vascular diameter, regulate the
amount of blood passing to a particular body part or organ), NOT secretomotor (nerve stimulation of
secretion), and cause blood vessel constriction
 Endocrine secretion from the thyroid gland is hormonally regulated by the pituitary
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Recurrent Laryngeal Nerves
 Near inferior pole of thyroid gland, r. recurrent laryngeal nerve is close to the inferior thyroid
artery/branches
 Danger of injury during surgery
 Because of this, inferior thyroid a. is ligated more distant/lateral to the thyroid gland to be further
from the nerves
 L. recurrent laryngeal nerves: not as great of a chance of damage since more vertical ascent from
superior mediastinum
 But artery and nerve are closely associated near inferior pole
 Hoarseness: sign of unilateral recurrent nerve injury
 Temporary aphonia or disturbance of phonation and laryngeal spasm might occur
 Usually result from bruising these nerves during surgery or from pressure of accumulated blood and
serous exudate post-op
 Thyroglossal Duct Cysts
 Embryonic thyroid gland travels from pharynx (foramen cecum)/dorsum of postnatal tongue into the neck
 During relocation, thyroid gland is attached to foramen cecum by the thyroglossal duct
 Duct normally disappears, but remnants of epithelium can remain and form a cyst at any point along the
path of descent
 Cyst is usually in the neck near hyoid bone and forms an anterior swelling
 Surgical excision may be necessary
 Aberrant Thyroid Gland
 Can be found anywhere along the path of the embryonic thyroglossal duct
 Thyroglossal duct carries thyroid-forming tissue can fail to relocate to neck
 Can be at the root of the tongue, posterior to foramen cecum: lingual thyroid gland
 Or can be at the neck near the hyoid (A)
 Cystic remnants of the duct can be differentiated from an undescended thyroid by radioscopic imaging (B)
 As a rule, an ectopic thyroid gland in the median plane of the neck is the only thyroid tissue present
 Sometimes thyroid tissue is associated with a cyst, so it is important to differentiate between the ectopic
thyroid gland and the cyst in removal of the cyst
 Failure to do this  total thyroidectomy, permanent dependence on thyroid medication
 Accessory Thyroid Glandular Tissue
 Portion of thyroglossal duct persists to form thyroid tissue
 Accessory thyroid can appear anywhere along the embryonic course of movement
 Can develop in the neck lateral to thyroid cartilage
 Usually lies on thyrohyoid muscle
 Can be functional, but usually too small to maintain normal function if thyroid is removed
 Thyroid Funkiness Cont.: Pyramidal Lobe
 ~50% of thyroid glands have a pyramidal lobe
 Varies in size
 Extends superiorly from the isthmus of the thyroid gland, usually to the left of the median plane
 Isthmus may be incomplete
 Band of connective tissue (often containing accessory thyroid tissue) may continue from the apex of the
pyramidal lobe to the hyoid
 Pyramidal lobe and band develop from remnants of the epithelium and connective tissue of the
thyroglossal duct
Parathyroid Gland:
 Produce parathormone (PTH) – controls metabolism of phosphorous and calcium in the blood
 Targets skeleton, kidneys, intestine
 Parathyroid Glands:
 Usually lie external to the thyroid capsule on the medial half of the posterior surface of each lobe of the
thyroid gland, inside its sheath
 Superior parathyroid glands
 Lie just above the point of entry of the inferior thyroid arteries into the thyroid gland
 Usually at the level of the inferior border of the cricoid cartilage
 Inferior parathyroid glands
 Lie just below the arterial entry point
 Usually near inferior poles of thyroid, but position is more variable than superiors
 Variability
 Most people have these 4; some have 2; ~5% have >4
 Inadvertent Removal of Parathyroid Glands
 Variable position of (esp. inferior) parathyroid glands puts them at risk for damage/removal during surgical
procedures in the neck
 Aberrant sites of these glands can be an issue when searching for abnormal parathyroid glands
 Cases of parathyroid adenoma (ordinarily benign tumor of epithelial tissue associated with
hyperparathyroidism)
 Parathyroid Arteries
 Inferior thyroid arteries primarily supply the posterior thyroid, where the parathyroid glands are located
 May also be supplied by branches from the superior thyroid arteries, the thyroid ima artery, or the
laryngeal, tracheal, and esophageal arteries
 Parathyroid Veins
 Parathyroid veins drain into the thyroid plexus of veins of the thyroid gland and trachea
 Lymphatic Drainage of Parathyroid
 Parathyroid lymphatic vessels drain with those from the thyroid gland into the deep cervical lymph nodes
and paratracheal lymph nodes
 Parathyroid Nerves
 Nerve supply of parathyroid glands is derived from thyroid branches of the cervical (sympathetic) ganglia
 As with thyroid, these nerves are vasomotor rather than secretomotor because the glands are hormonally
regulated
 Inadvertent Removal of Parathyroid Glands
 Tetany: atrophy or inadvertent surgical removal of parathyroid glands results in severe neurological
syndrome
 Characterized by muscle twitches and cramps
 Generalized spasms caused by decreased serum calcium levels
 Laryngeal and respiratory muscles are involved, so failure to respond immediately can result in death
 To protect these glands during thyroidectomy, surgeons usually preserve posterior thyroid lobes
 If it’s necessary to remove all of the thyroid gland, the parathyroids are carefully isolated with their blood
vessels intact before thyroid removal
 Parathyroid tissue can also be transplanted – usually to the arm – so it won’t be damaged by subsequent
surgery or radiation therapy
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Suprarenal (Adrenal) Glands
Located between the superomedial aspects of kidneys and diaphragm
Surrounded by connective tissue containing considerable perinephric fat
Enclosed by renal fascia attaching them to the crura of the diaphragm
Major attachment of the suprarenal glands is to the diaphragmatic crura rather than the kidneys
Separated from the kidneys by a thin septum (part of the renal fascia)
In chronic renal failure, kidney can be removed from donor without damaging suprarenal gland because of the
weak septum of renal fascia that separates the kidney from the gland
Each gland has a hilium where veins and lymphatic vessels exit the gland
Arteries and nerves enter the glands at multiple sites
In the ~5cm between the suprarenal glands, from R to L:
 IVC
 R crus of diaphragm
 Celiac ganglion
 Celiac trunk
 SMA
 Left crus of diaphragm
 Adrenal Gland CT
 Shape:
 Shape and relationships differ between R and L
 Crescent-shaped left gland
 Medial to the superior half of the left kidney
 Related to the spleen, stomach, pancreas, and left crus of the diaphragm
 Pyramidal right gland
 More apical relative to L
 Lies anterolateral to the R crus of the diaphragm
 Makes contact with the IVC anteromedially and the liver anterolaterally
 Suprarenal (Adrenal) Gland Components:
 Capsule: A tough fibroelastic covering of the adrenal gland.
 Cortex: essential to life - controls the electrolyte and water distribution in the body, maintains proper
carbohydrate balance.
 Derives from mesoderm
 Three concentric zones, each with a different cell arrangement.
 Zona glomerulosa: Produces aldosterone.
 Zona fasciculata: Produces cortisol.
 Zona reticularis: Produces androgens.
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Medulla: Produces epinephrine and norepinephrine.
 Derives from neural crest cells associated with sympathetic nervous system
 Chromaffin cells of the medulla are related to sympathetic ganglion neurons
 Adrenogenital Syndrome:
 Excessive quantities of androgens cause intense masculinizing effects throughout the body.
 Female
 Growth of a beard, deeper voice
 Baldness if she also has the genetic trait
 Masculine distribution of hair
 Growth of the clitoris to resemble a penis
 Prepubertal male
 Growth of a beard, deeper voice
 Masculine distribution of hair
 Rapid development of sex organs
 Adult male - difficult to make a diagnosis
 Suprarenal Medulla
 Chromaffin cells secrete catecholamines (mainly epinephrine) into the bloodstream
 Medullary hormones adrenaline (epinephrine) and noradrenaline (norepinephrine) activate the body to
fight-or-flight in response to acute stress
 Increase heart rate & blood pressure
 Dilate bronchioles
 Suprarenal Arteries
 Lots of blood supply necessary to support endocrine function
 50-60 suprarenal a. branches penetrate the capsule
 Suprarenal arteries arise from 3 sources:
 Superior suprarenal arteries (6-8) from inferior phrenic arteries
 Middle suprarenal arteries from the abdominal aorta
 Inferior suprarenal arteries from the renal arteries
 Suprarenal Veins
 Venous drainage through large suprarenal veins
 Short right suprarenal vein drains into IVC
 Longer left suprarenal vein is often joined by the inferior phrenic vein and empties into left renal vein
 Lymphatics of Suprarenal Glands
 Suprarenal lymphatic vessels arise from a plexus deep to the capsule of the gland and from a plexus in its
medulla
 Lymph passes to the lumbar lymph nodes
 There are many lymphatic vessels leaving the suprarenal glands
 Nerve Supply of the Suprarenal Glands
 Rich nerve supply of the suprarenal glands is from the celiac plexus and abdominopelvic (greater, lesser,
least) splanchnic nerves
 Myelinated presynaptic sympathetic fibers derived mainly from the intermediolateral (IML) cell column, or
lateral horn, T10-L1
 Travel through the paravertebral and prevertebral ganglia (without synapsing) and distribute to
chromaffin cells in the suprarenal medulla
 Adrenocorticoid Hyperfunction (Cushing’s Syndrome)
 Prolonged exposure to high levels of cortisol
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Pituitary tumor produces large amounts of ACTH
 Causes adrenal glands to  more cortisol
Suprarenal cortical hyperplasia
 Moon-shaped face
 Trunkal obesity
 Hypertension
Other causes: Adenoma or Carcinoma of the cortex
 Adrenal Insufficiency (Addison’s disease)
 Adrenal glands produce too little cortisol (and often too little aldosterone)
 Increased pigmentation (melanin production influenced)
 Muscular weakness
 Hypotension
 Can be caused by TB or bilateral atrophy of cortices
 Autoimmune in 80% of cases
 Diagnosed through blood tests, imaging
 Treated through hormone replacement (oral hydrocortisone and fludrocortisone)
 Disturbances of the Adrenal Medulla
 EXCESS
 Pheochromocytoma
 Too much epinephrine/norepinephrine
 Irritability/Nervousness
 Pallor
 Palpitations
 Tachycardia
 Hypertension & Blood pressure spikes
 Severe headache
 Sweating
 Weight loss
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President Eisenhower experienced an acute heart attack in September 1955 and died of ischemic
cardiomyopathy 14 years later. The autopsy revealed, unexpectedly, a 1.5-cm pheochromocytoma in the
left adrenal gland.
In view of these previously unreported findings, the investigators analyzed the blood pressure pattern of
the president throughout his life. Although hypertension was documented on and off from 1930 until his
death, it is unknown whether the pheochromocytoma was present during his presidency.
During the later part of President Eisenhower's life, excessive systolic and diastolic blood pressure spikes
were documented, although he concomitantly had severe ischemic cardiomyopathy.
In conclusion, most likely, the pheochromocytoma was the underlying cause of this erratic blood pressure
pattern and may have worsened the course of the president's ischemic cardiomyopathy.
 Key Concepts:
 Know: arteries, vein, nerves, and lymphatic drainage
 For: thyroid, parathyroid, and suprarenal (adrenal) glands
 Concepts in bold in this ppt.
 Cushing’s syndrome
 Addison’s disease
 Clinically-relevant details mentioned