ABSTRACT
Two adrenal glands are present in the adult, each located just rostral and medial to the upper poles of the kidneys. Each adrenal gland possesses a fibrous capsule subjacent to which is a cortex of coelomic epithelial (mesodermal) origin, and a medulla principally of neural crest-derived sympathetic nerve (ectodermal) origin. Two early cell types are recognized in the medulla: the sympathoblasts, which give rise to the mature sympathetic ganglion cells, and the phaeochromoblasts, which develop into the chromaffin cells. The gland also has a rich blood supply. In the adult human, the suprarenal arteries, which are usually of a large size compared to these glands, are derived from the abdominal aorta and pass directly to the suprarenal glands. These arteries enter the gland after dividing into several small branches. Other branches to the adrenals, usually termed the middle suprarenal arteries, are of various diameters and arise laterally from each side of the aorta. They anastomose with the suprarenal branches of the phrenic and renal arteries. The inferior suprarenal arteries ascend to the suprarenal glands from the renal arteries. The suprarenal vein emerges from the hilus of the gland. The one on the right side drains into the inferior vena cava, while that on the left side drains into the left renal vein.1,2 The arrangement observed in rodents has been described by Lever,3 and had previously been discussed by Gersh and Grollman4 and somewhat later by Harrison.5 The arrangement observed in rodents and in a number of other mammalian species differs from that in the human, and is discussed in detail later in this chapter.
