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ANATOMY SEM 4 > thyroid and parathyroid gland > Flashcards

thyroid and parathyroid gland Flashcards

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1
Q

where is the thyroid gland?

A
  • anterior neck — spans the C5-T1 vertebrae
  • located within the visceral compartment of the neck (along with the trachea, oesophagus and pharynx)
  • wrapped around the cricoid cartilage and superior rings of the trachea
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2
Q

what does the thyroid gland consist of in its structure?

A

two lobes (left and right), which are connected by a central isthmus anteriorly – this produces a butterfly-shape appearance

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3
Q

what is the visceral compartment of the neck bounded by?

A

pretracheal fascia

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4
Q
A
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5
Q

In the embryo, the thyroid gland begins development near the base of the tongue – in an area known as the___________. It descends during development and reaches its destination in the anterior neck by week ___.

A
  • foramen cecum
  • 7
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6
Q

what does the descend of the developing thyroid gland form? describe

A

the thyroglossal duct – an epithelialised tract that connects the gland to its origin at the foramen cecum

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7
Q

what happens/can happen to the thyroglossal duct?

A

It usually regresses by the 10th week of gestation, but can persist in some individuals. If it fails to regress, the duct can give rise to cysts or fistulae.

A thyroglossal cyst results from a build-up of secretions within the duct. It typically presents as a midline lump in the anterior neck which rises on tongue protrusion. If left untreated, this cyst can become infected, and form a cutaneous fistula – discharging out onto the skin of the anterior neck.

Thyroglossal cysts and fistulae are usually treated with complete excision. Recurrence is quoted at approximately 2.5%

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8
Q

anterior relations of thryoid gland

A

infrahyoid muscles, namely the sternothyroid, superior belly of the omohyoid and sternohyoid

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9
Q

lateral relations of thyroid gland

A

carotid sheath, containing the common carotid artey, internal jugular vein and vagus nerve

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10
Q

medial relations of the thyroid gland

A

Organs – larynx, pharynx, trachea and oesophagus
Nerves – external laryngeal and recurrent laryngeal

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11
Q
A
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12
Q

the thyroid gland gets its arterial supply from what 2 main arteries?

A

superior and inferior thyroid arteries

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13
Q

describe the superior thyroid artery

A

arises as the first branch of the external carotid artery.

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14
Q

what does the superior thyroid artery lie in close proximity to?

A

the external branch of the superior laryngeal nerve (innervates the larynx)

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15
Q

what does the inferior thyroid artery arise from?

A

the thyrocervical trunk (a branch of the subclavian artery)

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16
Q

what does the inferior thyroid artery lie in close proximity to?

A

the recurrent laryngeal nerve (innervates the larynx)

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17
Q

In a small proportion of people (around 10%) there is an additional artery present for the thyroid gland – describe

A

the thyroid ima artery

  • it arises from the brachiocephalic trunk and supplies the anterior surface and isthmus of the thyroid gland
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18
Q

venous drainage of the thyroid gland

A

superior, middle, and inferior thyroid veins, which form a venous plexus around the thyroid gland

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19
Q

The superior and middle thyroid veins drain into the ______ and the inferior empties into the __________.

A
  • IJV
  • brachiocephalic vein
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20
Q

thyroid gland innervation

A

innervated by branches derived from the sympathetic trunk.

These nerves do not control the secretory function of the gland – the release of thyroid hormones is regulated by the pituitary gland.

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21
Q

lymphatic drainage of thyroid gland

A

to the paratracheal and deep cervical nodes

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22
Q

The left and right ________ laryngeal nerves lie in close proximity to the thyroid gland and care must be taken not to damage them during thyroid surgery.

They branch from their respective _____ nerve within the chest and hook around the right _______ artery (right RL nerve), or the _________ (left RL nerve).

The recurrent laryngeal nerve then travels back up the neck, running between the ____ and ____ in the ___________________. It then passes underneath the thyroid gland to innervate the ______.

A
  • recurrent
  • vagus
  • subclavian
  • arch of the aorta
  • trachea
  • oesophagus
  • tracheoeosophageal groove
  • larynx
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23
Q

the parathyroid glands are responsible for the production of _______ which acts to do what?

A
  • parathyroid hormone (PTH)
  • increase the level of serum calcium
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24
Q

where are the parathyroid glands?

A
  • posterior aspect of thyroid gland
  • external to the thyroid gland itself but within the pretracheal fascia
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25
how many PT glands do most people have?
4 — 2 superior and 2 inferior
26
what are the parathyroid glands derived from?
2 x superior — from fourth pharyngeal pouch 2 x inferior — from third pharyngeal pouch
27
where are the superior vs inferior parathyroid glands
superior — located at the middle of the posterior border of each thyroid lobe, approximately 1cm superior to the entry of the inferior thyroid artery into the thyroid gland inferior — although inconsistent in location between individuals, the inferior parathyroid glands are usually found near the inferior poles of the thyroid gland
28
in a small number of people, the inferior parathyroid glands can be found as far inferiorly as what?
superior mediastinum
29
30
arterial supply of the parathyroid glands
similar to that of the thyroid gland. Arterial supply is chiefly via the inferior thyroid artery (as this artery supplies the posterior aspect of the thyroid gland – where the parathyroids are located). Collateral arterial supply is from the superior thyroid artery and thyroid ima artery.
31
venous drainage of the parathyroid glands
superior, middle, and inferior thyroid veins
32
lymphatic drainage of parathyroid glands
to the paratracheal and deep cervical nodes
33
The parathyroid glands have an extensive supply of _________ nerves derived from thyroid branches of the ________ ganglia. Note: these nerves are _________, not ___________ – endocrine secretion of parathyroid hormone is under hormonal control.
The parathyroid glands have an extensive supply of sympathetic nerves derived from thyroid branches of the cervical ganglia. Note: these nerves are vasomotor, not secretomotor – endocrine secretion of parathyroid hormone is under hormonal control.
34
1 = body of hyoid 2 = greater horn of hyoid 3 = thyroid cartilage 4 = cricoid cartilage 5 = cricothyroid membrane 6 = first tracheal cartilage 7 = left lobe of thyroid gland 8 = isthmus of thyroid gland - hyoid bone at C3 - upper border of thyroid cartilage at C4 - cricoid cartilage at C6
35
A = investing fascia B = pretracheal fascia C = carotid sheath D = prevertebral fascia the pretracheal fascia forms a loose sheath around the thyroid gland the investing fascia splits to surround sternocleidomastoid and trapezius muscles
36
- 2nd-4th tracheal rings - lie at the level of the 4th/5th tracheal rings - apex extends to the oblique line of the thyroid cartilage - sternothyroid and sternohyoid msucles lie anterior to the isthmus - carotid sheath lies posterolateral to the lateral lobe
37
A = superior thyroid artery - arises from the ECA. supplies the anterosuperior aspect of the gland B = inferior thyroid artery - arises from the thyrocervical trunk. supplies the inferior steroid aspect of the gland C = external carotid artery thyroid ima arteries usually arise from the brachiocephalic trunk but less commonly from the aorta, right common carotid, subclavian or internal thoracic
38
A = superior thyroid vein B = middle thyroid vein C = inferior thyroid vein the superior and middle thyroid veins drain into the IJV the thyroid vein drains into the brachiocephalic vein
39
A = middle thyroid vein B = superior thyroid artery C = superior thyroid vein D = inferior thyroid veins lymph from the thyroid gland drains to the prelaryngeal, pretracheal and paratracheal nodes and then to the deep cervical nodes sympathetic innervation to the thyroid gland is vasomotor
40
the glandular component of the thyroid gland is formed of simple cuboidal epithelium the follicular cells secrete thyroxine colloid contains thyroglobulin which is the storage form of thyroxine parafollicular/C cells secrete calcitonin
41
the superior parathyroid glands are commonly at the level of the inferior border of the cricoid cartilage A = superior thyroid artery B = ECA C = inferior thyroid artery D = thyrocervical trunk the inferior thyroid artery most commonly supplies the parathyroid glands the parathyroid veins drain into the thyroid plexus of veins lymph from the parathyroid glands drains into the paratracheal and deep cervical nodes the parathyroid glands are richly innervated by branches from the cervical sympathetic ganglia, these are vasomotor fibres
42
A = vertebral body B = liver C = IVC D = aorta E = spleen F = stomach G = xiphisternum H = ribs
43
A = psoas major B = right kidney C = right renal vein D = IVC E = aorta F = left renal artery G = liver H = gall bladder I = transverse colon J = descending colon K = small intestine L = pancreas
44
A = psoas major B = vertebral body C = left kidney D = aorta E = right renal artery F = IVC G = liver H = gall bladder I = duodenum J = stomach
45
A = rectus abdominis B = external oblique C = psoas major D = ascending colon E = descending colon F = the mesentery G = aorta
46
what are the vertebral levels of: 1. suprasternal notch 2. thyroid notch 3. lower border of cricoid cartilage 4. hyoid bone
1. T2/3 2. C4 3. C6 4. C3
47
B C A
48
what directions does the thyroid gland spread when it is enlarged?
anterior, posterior, inferior, lateral
49
what structures may be compressed by a thyroid goitre?
oesophagus, recurrent laryngeal nerves, trachea
50
What is the name of the pit, on the dorsum of the tongue, which marks the site of origin of the thyroglossal duct?
foramen caecum
51
when do ectopic thyroid glands occur?
- when the gland fails to descend - in incomplete descent, the gland will be located high in the neck - rarely, the gland may fail to leave the tongue and a lingual thyroid develops
52
what are pyramidal lobes?
- present in approx 50% of the population - these lobes extend upwards from the isthmus usually to the left of the median plane - they develop from the remnants of the epithelium and connective tissue of the thyroglossal duct
53
describe accessory thyroid tissue
- may be present anywhere along the route of descent of the thyroglossal duct - occurs when isolated pockets of glandular tissue of the thyroglossal duct fails to degenerate
54
describe thyroglossal duct cysts
- occur when the duct fails to degenerate between the back of the tongue and the thyroid gland - can be asymptomatic but fluid may accumulate in small pockets and infection may occur - the cysts are often located close to the hyoid bone - their position in the neck will rise if the patient sticks their tongue out
55
The thyroid gland consists of numerous rounded follicles containing colloid. The walls of each follicle consist of a single layer of _______ epithelial cells which secrete the colloid into the ___________. The colloid is ______ whilst it is within the _________forming triiodothyronine (___) and thyroxine (___). It is later reabsorbed by the _________ cells and then secreted into the blood. A second cell type are also present in the thyroid gland. They are called _________ or _____ cells and they contribute to 2% of the cells within the gland. Parafollicular cells secrete ___________.
The thyroid gland consists of numerous rounded follicles containing colloid. The walls of each follicle consist of a single layer of cuboidal epithelial cells which secrete the colloid into the central colloid lake. The colloid is iodinated whilst it is within the colloid lake forming triiodothyronine (T3) and thyroxine (T4). It is later reabsorbed by the follicular cells and then secreted into the blood. A second cell type are also present in the thyroid gland. They are called parafollicular or C cells and they contribute to 2% of the cells within the gland. Parafollicular cells secrete calcitonin.
56
what do thyroxine, calcitonin and parathyroid hormone do?
1. thyroxine — increases basal metabolic rate 2. calcitonin — reduces plasma calcium levels 3. parathyroid hormone — stimulates osteoclasts and increases plasma calcium levels
57
what triangle of the neck is the thyroid gland in?
muscular
58
anterolateral relations of the thyroid gland
sternohyoid, sternohyoid, superior belly of omohyoid
59
posterolateral relations of the thyroid
carotid sheath (IC 10 CCs in the IV)
60
medial relations of the thyroid
cricothyroid, nerves (external and recurrent laryngeal), trachea, oesophagus, larynx, pharynx
61
what structure does the thyroid gland develop from?
1st and 2nd pharyngeal arch
62
what week does the thyroid gland develop?
3rd = 1st endocrine gland to develop
63
which nerve is at risk of damage in a thyroidectomy?
recurrent laryngeal
64
why cant the thyroid gland enlarge superiorly?
sternohyoid and sternothyroid muscles
65
what vocal changes may be noticed in someone with thyroid enlargement?
hoarse — suppresses recurrent laryngeal nerve - supplies vocal cord
66
through which 3 mechanisms does parathyroid hormone increase calcium?
- activates vit D — allows absorption in the gut - promotes resorption by osteoclasts — release Ca - promotes reabsorption of Ca in kidney
67
innervation of parathyroid glands
branches of cervical sympathetic ganglia

ANATOMY SEM 4 (12 decks)

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