Adrenal Cortex Anatomy and Hormonal Functions

Adrenal Gland Location

The adrenal glands, also known as suprarenal glands, are located above the kidneys. They are shaped like pyramids in three dimensions but appear triangular in two-dimensional views. These glands lie beneath the protective capsule of the kidneys and play a vital role in producing several hormones.

Adrenal Gland Anatomy

The gland consists of an outer cortex. The cortex is fatty. The inner medulla appears to be full of neurosecretory axons. The cortex has a striped appearance, while the medulla contains blood vessels and neuronsThe functional cells of the nervous system that transmit signals.. The hypothalamusA small but vital brain region controlling hormones, temperature, and autonomic functions. connects directly to the adrenal medullaInner part of adrenal glands producing catecholamines (epinephrine, norepinephrine). through neurons.

Adrenal Cortex Zones

The cortex has three zones.  From superficialNear the surface of the body. to deepAway from the surface of the body., these are: the zona glomerulosaOuter adrenal cortex layer, secreting aldosterone., zona fasciculataMiddle adrenal cortex layer, secreting glucocorticoids., and zona reticularisInner adrenal cortex layer, producing androgens..  The word glomerulosa means “little spheres.”  The histology of this outermost layer of the cortex shows small sphere-like structures. They are just deep to the capsule. 

The zona fasciculata is named for its “ribbon-like“ appearance.  This zone is the largest of the zones and accounts for the bulk of the cortex.  The histology shows these nice cords or lines of cellsThe basic structural and functional units of life. that look like ribbons. 

The zone reticularis is the innermost zone of the cortex. It is located just superficial to the adrenal medulla. The medulla is like a completely separate organ.  The word reticular is common. It has many applications to histology, organs, and structures. These often have a network or web-like appearance.  In truth, this weblike network in the adrenal cortexOuter portion of the adrenal glands producing corticosteroids. can be obscured by the way the cortex is cut.

Adrenal Cortex Hormones

The outermost layer, the zona glomerulosa, produces mineralocorticoidsRegulate electrolyte and water balance (e.g., aldosterone). such as aldosteroneA hormone that increases sodium and water reabsorption in the kidneys, helping regulate blood pressu. Aldosterone targets the kidney to regulate blood pressureThe force exerted by gases in the respiratory system, affecting airflow and gas exchange.. 

The middle layer, the zona fasciculata, produces glucocorticoidsSteroid hormones regulating metabolism and immune response., primarily cortisolA glucocorticoid involved in stress response, metabolism, and immune regulation.. Cortisol plays a part in your long-term stress response.  

The innermost layer, the zona reticularis, produces androgensMale sex hormones, including testosterone and DHEA., which serve as precursors to sex hormones like testosterone and estrogen. These hormones influence secondary sex characteristics and are converted into active sex hormones in other tissues. Androgens affect various tissues depending on the specific sex hormone derived from them.

Aldosterone ensures proper hydration and electrolyte balanceThe maintenance of appropriate levels of ions like sodium, potassium, calcium, and magnesium in body, stabilizing blood pressure by acting on the kidneys. Cortisol helps the body cope with stress by providing quick energyThe capacity to do work or cause change., controlling inflammation, and regulating blood pressure. Androgens support puberty and maintain certain functions in adults by serving as an alternate source of sex hormones.

Aldosterone

Aldosterone, a mineralocorticoid, regulates ionsCharged atoms or molecules. like sodium(Na⁺): Major ECF cation; important for fluid balance, nerve function. and potassium(K⁺): Major ICF cation; essential for muscle and nerve function. in the blood. It is released by the zona glomerulosa and targets the kidney, conserving sodium and excreting potassium. This action increases blood volume and pressure. Low sodium levels, high potassium levels, and ACTH from the anteriorThe front of the body or toward the front when standing in the anatomical position. pituitary can trigger aldosterone release. Renin from the kidney can also trigger its release.

Aldosterone encourages the reabsorptionThe process of fluid moving back into capillaries from surrounding tissues due to colloid osmotic p of sodium, which means that it makes you keep sodium.  This also causes you to keep waterThe universal solvent essential for life., increasing blood volume and blood pressure.  This is why people are given salt tablets in hot environments – so they retain more water.  This is why you become bloated from salty foods like ham and pickled things.  You should eat some crackers before bed if you suspect a hangover. A hangover is really just a severe case of dehydrationA condition in which fluid loss exceeds intake, leading to a decrease in total body water..  Aldosterone is also really important in the management of potassium.  Your kidney prefers to get rid of potassium, keeping it quite low.  If potassium goes high, the adrenal cortex senses this humoral trigger and releases aldosterone.  Aldosterone then makes the kidney secrete or get rid of potassium.

Cortisol

Cortisol, a glucocorticoid released by the zona fasciculata, is regulated by the hypothalamus and anterior pituitary through ACTH. You suffer physical effects when stressed at the end of the semester. These are effects of cortisol.  

Let’s start at the bottom here.  These are white blood cells.  When you are under long term stress, cortisol lowers your ability to make these cells.  This causes a decreased ability to fight viruses and bacteria. It makes you sick at the end of the semester.  Bone and cartilageA flexible connective tissue found in joints, the ear, nose, and rib cage. Cartilage can be of three formation are depressed with cortisol, making stress management for young kids important.  Growing up in a trauma-state of violence, abuse, and/or neglect can pump cortisol from the adrenal cortex full-time.  This is why I am, like, barely 5 feet tall.  Barely.

Cortisol not only manages potassium via the kidney. It also increases blood sugar by stimulating glucoseA simple sugar that is the main source of energy for cells. production in the liverA large organ that produces bile, detoxifies blood, and stores nutrients.. Additionally, it triggers the release of stored energy in adipose reserves.  At the end of the semester, students experience various digestive issues. These range from newly diagnosed conditions like Crohn’s disease to simple heartburn.  This is cortisol at work.  It’s also working on your brain and your ability to concentrate.  This is why the last test/paper/quiz in all your classes just seems impossible.  It’s cortisol at work.  Stress-management is crucial at the end of the semester. You can manage stress through deep-breathing, exercise, or therapy.  My preferred methods are therapy and coloring.  As if that comes as a surprise to you!