The adrenal gland is very important to the human bodyendocrineThe organ is located above the kidneys on both sides, so it is called adrenal gland.The adrenal glands are located on the upper part of the kidney and are wrapped by the renal fascia and adipose tissue.The left adrenal gland is half moon shaped, and the right adrenal gland is triangular.The total weight of both adrenal glands is about 30g.Viewed from the side, the gland is divided into two parts: adrenal cortex and adrenal medulla. The surrounding part is cortex and the inner part is medulla.They are different in genesis, structure and function, and are actually two endocrine glands.
The adrenal gland is a pair of endocrine glands. It is soft and light yellow. Its size is about 5 × 3 × 1cm2, and its weight is about 7g. The one on the left is slightly larger;It is located in the retroperitoneal space on both sides of the spine and belongs to an extraperitoneal organ.The left adrenal gland is longer and half moon shaped.Its front is adjacent to stomach, pancreas and spleen;Left foot with diaphragm attached behind;The lower depression is called the renal surface, which lies on the upper part of the medial edge of the left kidney;The medial margin contacts the abdominal aorta and the celiac ganglion.The left adrenal hilum is located in the lower part in front of it, and there is a central adrenal vein passing through the door and flowing into the left renal vein.The right adrenal gland is slightly shorter and triangular.There is no peritoneum in the front of it, and it is in direct contact with the inferior vena cava;The lateral branch is adjacent to the liver;The back of the gland is slightly convex and close to the diaphragm;The bottom depression is called the renal surface, which lies on the upper end of the right kidney, and the medial edge is adjacent to the celiac ganglion.The right adrenal hilum is located at the front inner superior branch of the gland. The central adrenal vein passes through the portal and flows into the inferior vena cava or the right renal vein.The adrenal gland and the kidney are wrapped together in the renal fascia, but each has its own fibrous capsule and fat capsule;Therefore, it does not move downward with the kidney.The adipose connective tissue between the adrenal gland and the kidney is not obvious in the fetus and newborn, but gradually thickens with age.Sometimes small tissue similar to the adrenal cortex structure can be seen near the adrenal gland or in the abdominal plexus, which is called accessory adrenal or cortical body;It is rare in humans.
The blood supply of the blood vessels, lymph nodes and nerves adrenal glands is extremely rich. The arteries are supplied by the superior, middle and inferior adrenal arteries, which originate from the inferior phrenic artery, abdominal aorta and renal artery respectively.The three groups of arteries were divided into small branches to the fibrous capsule of the adrenal gland, anastomosing each other into a plexus, from which the cortical branches and medullary branches were sent out to supply the cortical bands and medulla.The blood in the blood sinus flows out through the small vein and the central vein, and flows into the left renal vein and the inferior vena cava through the left and right adrenal veins.The lymphatic capillaries in the gland form clusters and gradually converge into larger lymphatic output, and finally enter the lumbar lymph node.The nerves are mainly originated from the abdominal plexus, and the phrenic plexus and adrenal plexus are distributed in hair branches.The preganglionic fibers of the sympathetic nerve form the adrenal plexus on the inner side of the adrenal gland. Its branches pass through the fibrous capsule to form the subcapsular plexus of the adrenal gland. The subcapsular plexus then branches to the chromaffin cells and sympathetic ganglion cells of the blood vessels and medulla to secrete.
The adrenal gland is divided into cortex and medulla. The embryonic origin of the two parts is completely different. The former comes fromMesoderm, the latter comes fromEctoderm。The medulla is wrapped by cortex, and its organizational structure and hormone secretion function are independent.Adults' adrenal cortex is solid and golden, accounting for 90% of the total weight of the gland;The medulla is loose and brown, accounting for 10%.The adrenal cortex is divided into three layers: the outermost layer is the zona glomerulosa, which accounts for 15% of the cortex. The cells are arranged in a spherical shape and secreteMineralocorticoid；The second layer is the zona fasciculata, which accounts for 75% of the cortex. The cells are arranged in cords and secreteGlucocorticoid；The third layer is the zona reticularis, which accounts for about 10% of the cortexsex hormone。stayAdrenocorticotropic hormoneUnder the stimulation of ACTH, the zona reticularis could be widened and the zona fasciculata narrowed accordingly.The main cells of adrenal medulla areChromaffin cell。When these cells are stained with potassium dichromate, there are brown chromate containing particles in the cytoplasm, hence the name. The function of chromaffin cells is to synthesize and secrete epinephrine (E) or norepinephrine (NE). About 85% of the human adrenal medulla reserves are epinephrine.[1]
