Anatomy Flashcards
Location of the hypophysis
Encased in the sphenoid bone
- Sella turcica
Inferior to the hypothalamus
- Connected by the infundibulum
Posterior to the optic chiasm
Structure of hypophysis
Divided into
- Neurohypophysis, posterior–> Neural down-growth of the diencephalon
- Adenohypophysis, anterior–> Outpouch of ectoderm, Rathke’s pouch (oral cavity)
Function of the hypophysis
Master gland
- Secretes hormones to to all glands, control their secretion.
Arterial supply to the hypophysis
Superior and Inferior hypophyseal artery
- From ICA
Superior supplies
- Median eminence
- Upper infundibulum
Inferior supplies
- Neurohypophysis
- Lower infundibulum
Arteries supplying the infundibulum and median eminence end as capillary plexus as the anastomose.
Venous drainage of the hypophysis
Portal system
Capillary plexus at the stalk ending and median eminence drain into portal veins.
- Form secondary capillary plexus at the anterior pituitary.
- Allows substances from the hypothalamus to reach the anterior pituitary.
Compare hormonal from neurotransmission
Hormonal—> Release of hormones
- Much slower
- Transported every in the body via circulatory system
Neurones–>Neural impulse, using neurotransmitters
- Very fast (1-2ms)
- Act locally from pre to postsynaptic neurones, microns apart
Thyroid location
Anterior to the trachea
- Lateral to thyroid cartilage
Recurrent laryngeal nerves passes deep to the posteromedial surface of the lobes.
Type of endocrine glands [3]
Discrete- separate and distinct. Only secretes hormones
- Hypophysis
- Thyroid and parathyroid
- Adrenal
Larger glands- both exocrine and endocrine function
- Pancreas
- Kidney
- Ovaries/ testes
- Placenta
Diffuse neuroendocrine
- Nerve cells with endocrine function
Anatomy of thyroid
Two lobes joined by the isthmus
- Covers 5-6 cartilage rings
- Covers cricoid and lower cartilage
Arterial supply of the thyroid
Superior thyroid
- From external carotid
Inferior thyroid
- From thyrocervical trunk (subclavian)
Venous drainage of the thyroid gland
Plexus drains into the superior, middle and interior thyroid veins.
Thyroid veins drain into
- Internal jugular (superior and middle)
- Brachiocephalic (inferior)
Development of the thyroid
Endodermal origin
- From the floor of the pharynx, near the base of the tongue
Thyroid function
Release of thyroid hormones that regulate growth and development- T3, T4
- Under the control of TRH and TSH from the hypothalamus and anterior pituitary
Cricothyrotomy
Incision in the cricothyroid membrane to establish patent airway.
Parathyroid location
Deep to the lateral lobes of the thyroid
- Posterior aspect of the thyroid capsule.
Can also be located elsewhere between the carotid bifurcation and the mediastinum.
Parathyroid origin
Third pharyngeal pouch
- inferior parathyroid
Fourth pharyngeal pouch
- Superior parathyroid
The pouches grow caudally towards the thymus to their adult positions.
Anatomy of the parathyroid gland
2 pairs- 4 altogether
- Superior and inferior
- Very small- 40mg, size of the grain of rice.
Arterial supply of the parathyroid
Mainly inferior thyroid artery
- From Thyrocervical trunk (subclavian)
Superior thyroid
- From external carotid
Venous drainage of parathyroid
Superior, middle and thyroid veins
- Drains into Internal jugular and brachiocephalic
Nervous supply of the parathyroid
Middle and inferior cervical ganglion.
Function of the parathyroid
Composed predominantly of epithelial chief cells
- Secretes PTH
PTH regulates blood calcium and phosphate levels.
Parathyroid implication of thyroidectomy
Parathyroid MUST be conserved
- Unless calcium and phosphate regulation is disrupted.
Leads to hypocalcaemia–> Tetanic contraction—> death.
Adrenal gland location
Superior to kidneys
- At T12 level
- Retroperitoneal
Adrenal gland gross anatomy
- Shape
- Layers
- Size
Left gland—> Semilunar
Right gland—> Pyramidal
Layers
- Outer capsule
- Cortex
- Medulla
Size
- 3.5-5g
Adrenal gland orgin
Medulla—> Neural function
- Neural crest origin
Cortex—> Exocrine
- Mesodermal orgin
Adrenal medulla function
Release of catecholamines
- NA and ADR from chromaffin cells
Cells act are modified sympathetic post-ganglionic
Release of catecholamines= fight or flight
- Raised HR, BP
- Relaxation of SM viscera.
Adrenal cortex function
Release of adrenal corticosteroids and adrenal androgens
- Glucocorticoids, from zona fasciculata—> Maintains blood glucose concentration
- Mineralocorticoids, from zona glomerulosa—> Maintains Na+ levels
Secretion of hormones under the control of ACTH, RAS.
Adrenal medulla ANS
Receives direct preganglionic fibres from the sympathetic trunk
- Allows fast fight-or-flight response
Impulse—>release of Ach–> Chromaffin cells—> Release of NA, ADR
Also receives post-ganglionic fibres from coeliac ganglion
- Supplies blood vessels that penetrates the cortex
Arterial supply of the adrenal gland
Superior suprarenal artery
- From Inferior phrenic
Middle suprarenal
- From aorta
Inferior suprarenal
- From renal
Arteries branch before entering capsule
Cortex
- Arteries branch into subcapsular plexus—> sinusoids
Medulla
- Arteries pass through cortex, into medulla—> Cortical activity can influence medulla
Venous drainage of the adrenal glands
Adrenal veins
- Drain into IVC (R)
- Drain into left renal vein (L)
