Development, Gross Anatomy and Functional Histology of the Suprarenal Gland Flashcards
Where are the suprarenal glands located?
In the superior pole of the kidneys, there are two glands: one left and one right.
They lie between the superomedial aspect of the kidney and the diaphragm
What are the fascial relations of the kidney?
Fibrous capsule
Perirenal fat
Renal fascia
Pararenal fat
What separates the suprarenal gland from the kidney?
The perirenal fat
What is the shape of the right suprarenal galnd?
Pyramidal in shape
What is the shape of the left suprarenal gland?
Crescentic in shape
What are the relations of the right suprarenal gland?
Anterior: Liver and IVC
Posteriorly: Right crus of the diaphragm
What are the relations of the left suprarenal gland?
Anterior: Stomach, pancreas and spleen
Posterior: Left crus of the diaphragm
What are the the cruses of the diaphragm?
Part of the origin of the diaphgram
What is the cavity between the stomach and the adrenal gland?
The lesser sac
What are the parts of the suprarenal gland?
Medulla and the cortex
What are the layers of the cortex of the suprarenal gland?
Zona glomerulosa
Zona fasciculata
Zona reticularis
What are the embryological origins of the medulla and the cortex?
Medulla: ectoderm (neural crest cells)
Cortex: mesoderm
What is the developmental process of the formation of the fetal cortex?
- Mesenchymal cells on each side of the embryo
- Located between the root of the dorsal mesentery and the urogenital ridge
- Formation of the fetal cortex from the aggregate of these mesenchymal cells
What is the fetal cortex?
The first stage of the process of the cortex development
What occurs with the formation of the fetal cortex?
Neural crest cells arrive
Where are neural crest cells derived from?
Neural tube
What kind of cells do neural crest cells give rise to?
Neurons
Glia
Melanocytes
What happens following the arrival of the neural crest cells?
The neural crest cells form a mass on the medial side of the fetal cortex; cells differentiate into secretory cells of the medulla
What are chromaffin cells?
They are cells that stain positive with the chromaffin stain
Where are medullary chromaffin cells derived from?
Neural crest cells
What happens after the differentiation of medullary chromaffin cells into the medulla?
- A 2nd wave of mesothelial cells penetrates the underlying mesenchyme
- Aggregate of cells surround the fetal cortex and form the definitive cortex
Where do the different zone develop from?
Zona glomerulosa: Definitive cortex
Zona fasciculata: Definitive cortex
Zone reticularis: fetal cortex regression
What is the different theory regarding the development of the layers of the cortex?
A second theory claims that all zones are derived from the definitive cortex and the fetal cortex is simply degraded
What are the cells of the adrenal cortex like?
Typical ultrastructure of steroid-secreting cells
They do not store their secretory products in granules
Why are there lipids in the cells of the adrenal cortex?
They are part of the synthesis of the steroid hormones
Why is SER so abundant in adrenal cortex cells?
It is involved in the synthesis of steroid hormones
What is the difference between RER and SER?
RER has ribosomes and is usually associated with peptide-hormone secretion
What kind of cells does zona glomerulosa consist of?
Rounded clusters of columnar/pyramidal cells
What do the cells of the zona glomerulosa secrete?
Mineralocorticoids
What is an example of mineralocorticoids?
Aldosterone –> balances potassium and sodium
What % of the cortex does zona glomerulosa make up?
15% of cortex
What cells does zona fasciculata consist of?
Long cords of large polyhedral cells which form bundles
What are the cells of the zona fasciculata also called?
Spongycytes because they contain a great number of lipid droplets in their cytoplasm
What do the cells of the zona fasciculata secrete?
Glucocorticoids and small amounts of sex hormones
What is an examples of glucocorticoids?
Cortisol
What % of the cortex does the zona fasciculata account for?
65 to 80%
What kind of cells does the zona reticularis consist of?
Smaller cells, heavily stained
Why are the cells of the zona reticularis heavily stained?
They contain less lipid droplets
What do the cells of the zona reticularis form?
Network of irregular cords, interspersed with wide capillaries
WHat do the cell of the zona reticularis secrete?
Mainly sex hormones and cortisol
What is an example of sex hormone secreted by the zona reticularis?
DHEA –> helps produce other hormones such as testosterone and estrogen
What % of the cortex does the zona reticularis make up?
10% of the cortex
What are the cells of the adrenal medulla like?
Large polyhedral cells arranged in cords or clumps
What is the most abundant cell in the adrenal medulla?
Chromaffin cells from the neural crest cells
What other structures does the adrenal medulla contain? (2)
- Single or groups of sympathetic ganglions and preganglionic sympathetic nerve bundles –> thus the adrenal medulla has a close relation to the sympathetic nervous system
- Presence of sinusoidal capillaries
What hormones does the adrenal medulla secrete?
Adrenaline/epinephrine (80%)
Noradrenaline/norepinephrine (20%)
What are the cells of the suprarenal gland medulla like?
Medullary cells have abundant membrane-limited electron-dense secretory cells
These granules contain one or the other of the catecholamine (epinephrine or norepinephrine)
What is the difference in appearance between NE and E secretory cells?
NE cells are larger and more electron-dense compared to E cells
What is the arterial supply of the suprarenal gland like?
Superior suprarenal artery
Middle suprarenal artery
Inferior suprarenal artery
What is the root of the superior suprarenal artery?
Inferior phrenic artery
What is the root of the middle suprarenal artery?
Abdominal aorta
What is the root of the inferior suprarenal artery?
Renal artery
Why does the suprarenal gland have three different sources of blood supply?
Cortisol is such a crucial hormone, and since it is secreted by the suprarenal gland, it is important for the gland to have an efficient enough blood supply to provide it even in the case that anything happens
Why is there no hilum in the suprarenal gland?
So that there is continuous supply of blood to the gland at different points
What is the medullary artery?
It is one of the two supplies of blood for the medulla of the suprarenal gland, it penetrates the cortex and goes straight into the medulla
How many blood supplies does the medulla have?
2:
Medullary artery
Capillaries of the plexus
Why are the capillaries of the plexus not enough to supply the medulla of the suprarenal gland?
They have to pass and supply the cortex with oxygenated blood as well so by the time they would have reached the medulla there would be insufficient blood to provide
What is the venous drainage of the suprarenal gland?
Right suprarenal vein –> Inferior vena cava
Left suprarenal vein –> Left renal vein –> Inferior vena cava
Which suprarenal vein is closer to the IVC?
The right suprarenal vein is closer to the IVC and thus drains directly into it
Why does the left suprarenal vein not drain directly into the IVC?
It is further away from the IVC, and because of the anterior structures and the fragile nature of the vein, it drains into the renal vein first, and then that one drains into the IVC
Which artery is closer to the IVC?
Left suprarenal side of the arteries
What is the lymphatic drainage of the suprarenal gland like?
Lumbar aortic nodes and paraaortic nodes
What is the parasympathetic system known as?
Craniosacral
What is the sympathetic system known as?
Thoracolumbar
Where do the sympathetic nerves originate from?
Lateral horn, and then they move to the gray ramus, where they either synapse or bypass the sympathetic trunk
Which are the pre-ganglionic sympathetic neurons?
T5 to T8 –> greater thoracic splanchnic nerves
What happens to the pre-ganglionic sympathetic neurons if they bypass the sympathetic trunk without synapse?
They initiate an alternative route, where they stay as preganglionic and they target the modified cells of the medulla to secrete NE or E
What happens to the pre-ganglionic sympathetic neurons that synapse at the sympathetic trunk?
They are not involved in the secretion of NE or E in the medulla but instead they regulate dilation of the blood vessels