thyroid, parathyroid and adrenal glands Flashcards
The adrenal gland is composed of two distinct tissues: the outer cortex and the inner medulla. The adrenal cortex tends to be fattier and thus has a more yellow hue. The adrenal medulla is more of a reddish-brown color. A thick capsule consisting of connective tissue surrounds the entire adrenal gland.
what are the layers of the adrenal cortex and what do they release
Zona glomerulosa – produces and secretes mineralocorticoids such as aldosterone.
Zona fasciculata – produces and secretes corticosteroids such as cortisol. It also secretes a small amount of androgens.
Zona reticularis – produces and secretes androgens such as dehydroepiandrosterone (DHES). It also secretes a small amount of corticosteroids.
where do the superior, middle and inferior adrenal arteries arise from respectively
Superior adrenal artery – arises from the inferior phrenic artery
Middle adrenal artery – arises from the abdominal aorta.
Inferior adrenal artery – arises from the renal arteries.
innervation of the Adrenal glands
The adrenal glands are innervated by the coeliac plexus and greater splanchnic nerves.
Sympathetic innervation to the adrenal medulla is via myelinated pre-synaptic fibres, mainly from the T10 to L1 spinal cord segments.
what does aldosterone do
Aldosterone acts in the body by binding to and activating a receptor in the cytoplasm of renal tubular cells. The activated receptor then stimulates the production of ion channels in the renal tubular cells. It thus increases sodium reabsorption into the blood and increases potassium excretion into the urine.
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 ……..
The descent of the developing thyroid gland forms the ……………. – an epithelialised tract that connects the gland to its origin at the foramen cecum. 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.
foramen cecum
week 7
thyroglossal duct
A thyroglossal cyst results from a build-up of secretions within the duct.
how does it present
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.
what arteries supply the thyroid
Superior thyroid artery – arises as the first branch of the external carotid artery. It lies in close proximity to the external branch of the superior laryngeal nerve (innervates the larynx).
Inferior thyroid artery – arises from the thyrocervical trunk (a branch of the subclavian artery). It lies in close proximity to the recurrent laryngeal nerve (innervates the larynx).
In a small proportion of people (around 10%) there is an additional artery present – the thyroid ima artery. It arises from the brachiocephalic trunk and supplies the anterior surface and isthmus of the thyroid gland.
Venous drainage is carried by the superior, middle, and inferior thyroid veins, which form a venous plexus around the thyroid gland.
The superior and middle veins drain into the internal jugular vein and the inferior empties into the brachiocephalic vein.
parathyroid gland supplied by what
inferior thyroid artery
venous via all three
thyroid gland vertebral level
C5-T1
hyoid bone
C4
only complete ring in body of cartilage
cricoid cartilage
post and ant triangles split by what
sternocleidomastoid
the thyroid gland start as a bud called the thyroglossal duct that pushes outwards from the pharyngeal floor and descend to become the thyroid gland at the foramen caecum ( post tongue) lower end becomes the gland top disappears
the thoracic duct should go if not cyst forms
what operation to remove the thyroglossal cyst
sistrunks operation
benign disease of the thyroid is more common if it expands what will get quashed
trachea and oesophagus
