The adrenal glands are a pair of organs above the kidneys which produce hormones. The outer covering is called the adrenal cortex and is comprised of three layers: the zona glomerulosa, the zona fasciculata and the zona reticularis. The inner core is called the medulla. The cells of each layer of the cortex and the medulla are designed to make different hormones.
Cells of the Zona Glomerulosa
According to "Wheater's Functional Histology" by Barbara Young, cells of the zona glomerulosa are arranged in irregularly sized and shaped oval clusters separated by fibrous connective tissue. The cells have round nuclei, the control center of the cell where the DNA is found. They also have less fat like molecules called lipids and less cytoplasm than cells of the zona fasciculata. The cytoplasma is the liquid suspension within the cell. These cells mostly secrete aldosterone, a hormone that causes the kidneys to retain sodium that is released in response to low blood pressure or low sodium levels.
Cells of the Zona Fasciculata
Cells of the zona fasciculata are arranged into narrow cords and separated by thin strands of connective tissue. They have a lot of cytoplasm and lipids. Cells of this layer secrete mostly the hormone cortisol and others similar to it, but also secretes a small amount of androgenic hormones, which are male hormones such as testosterone. Cortisol is a stress hormone. Some of its effects are to raise blood glucose, increase protein and fat breakdown for energy use by the body in times of stress.
Cells of the Zona Reticularis
The cells of the zona reticularis are adjacent to the innermost layer of the adrenal gland: the medulla. These cells are arranged as clusters and branching cords. The cells are smaller than those of the zona fasciculata and contain few lipids. These cells secrete mostly sex steroids such as testosterone and estrogen.
Cells of the Medulla
The cells of the medulla include chromaffin cells and sustenacular cells. Chromaffin cells have polygonal walls and are arranged in small nests and cords. They primarily synthesize epinephrine, also known as adrenalin. This hormone is released in response to physical and psychological stress. It functions to get the body ready for fight or flight by dilating the airways, diverting blood to the muscles, increasing the heart rate among other things. The sustenacular cells support the chromaffin cells.
References
- "Wheater's Functional Histology"; Barbara Young; 5th Ed 2006
- Pathology Outlines: Adrenal Gland
