Which is the following is true regarding endocrine organ histology?
a. The thyroid gland consists of rings of stratified cuboidal follicle cells surrounding colloid.
b. The pancreas has an exocrine portion consisting of pancreatic islets and an endocrine portion consisting of acinar cells.
c. The adrenal cortex has three zones of cells that secrete steroid hormones.
d. The adrenal medulla is modified nervous tissue of the parasympathetic nervous system.
The Correct Answer and Explanation is :
The correct answer is c. The adrenal cortex has three zones of cells that secrete steroid hormones.
Explanation:
The adrenal cortex is the outer part of the adrenal glands, and it is composed of three distinct zones, each responsible for producing different types of steroid hormones:
- Zona Glomerulosa: This is the outermost layer, which primarily secretes mineralocorticoids, such as aldosterone. These hormones are crucial for regulating sodium and potassium balance and maintaining blood pressure.
- Zona Fasciculata: The middle layer of the adrenal cortex secretes glucocorticoids, with cortisol being the most significant. Glucocorticoids are essential for glucose metabolism, immune response regulation, and stress responses.
- Zona Reticularis: This innermost layer produces androgens, which are male sex hormones like dehydroepiandrosterone (DHEA). While these hormones are less prominent than those produced in the gonads, they play a role in sexual development and function.
Incorrect Options:
a. The thyroid gland does not consist of rings of stratified cuboidal follicle cells. Instead, it is made up of follicles lined with simple cuboidal or columnar epithelial cells surrounding a central lumen filled with colloid, which contains thyroglobulin.
b. The pancreas has an exocrine portion that consists of acinar cells that produce digestive enzymes, and the endocrine portion consists of pancreatic islets (Islets of Langerhans) that secrete hormones like insulin and glucagon. Therefore, this statement is incorrect in describing the functions of these cells.
d. The adrenal medulla is not part of the parasympathetic nervous system; it is actually a modified sympathetic nervous tissue. It produces catecholamines like adrenaline (epinephrine) and norepinephrine, which are vital for the body’s “fight or flight” response.
In summary, the adrenal cortex is well-defined by its three zones, each of which plays a distinct role in hormone production, making option c the only accurate statement among the choices provided.