The masses often have a recognisable capsule and may contain calcification. The appearance of myelolipomas on CT depends on their histological composition, with some tumours showing only small regions of fatty tissue in a predominantly soft-tissue mass, whilst others are almost completely composed of fat ( Figs 37.21 and 37.22). The tumour may have areas of fibromyxoid degeneration, haemorrhage, necrosis and calcification. Usually the tumour is smaller than 5 cm, solitary and is composed of hematopoietic precursor cells and mature adipose tissue in varying proportions.
Medullary arteries and arterioles penetrate the cortex without branching, then form capillary beds in the medulla.īlood from both cortical and medullary veins empties through a single large central vein, which leaves the adrenal and anastomoses with either the vena cava or renal vein.Andreas Adam CBE, MB, BS(Hons), PhD, PhD (hon caus), DSc (hon caus), FRCP, FRCR, FRCS, FFRRCSI(Hon), FRANZCR(Hon), FACR(Hon), FMedSci, in Grainger & Allison's Diagnostic Radiology, 2021 MyelolipomaĪlthough described as rare (0.1% to 0.2% of cases), these benign, non-functioning lesions are increasingly detected incidentally on imaging and their true incidence is likely to be higher. Cortical arteries and arterioles branch into capillary beds within the cortex to supply that area, then coalesce into veins at the corticomedullary junction. Numerous small arteries from several sources ramify over the surface of the gland and penetrate into the gland into two ways: Histologic examination of the adrenal reveals a rich vasculature. cells in the fasiculata produce a small amount of androgens and cells in the reticularis secrete some cortisol).Ĭatecholamines (epinephrine and norepinephrine) There is some overlap in hormones synthesized by the zonae fasiculata and reticularis (i.e. The medulla produces catecholamines and the cortex produces several steroid hormones, as depicted in the table below. The three cortical zones and part of the medulla are evident in the section of rabbit adrenal gland seen below.Ī higher magnification montage of a feline adrenal gland is available.īased on embryologic origin and type of hormones produced, the cortex and medulla are best though of as separate endocrine organs. 
zona glomerulosa - thin, outermost zone.The medulla is fairly homogeneous, but even when viewed a low power, three concentric zones can be distinguished in the cortex: The most distinctive feature of the adrenal is its partitioning into cortex and medulla.
The organ is richly vascularized and capsular blood vessels, nerves and lymphatics penetrate along with the connective tissue septae. The adrenal gland is encased in a connective tissue capsule that extends septae into the substance of the gland.
Endocrine System > Adrenal Glands Overview of Adrenal Histology
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