The Adrenal Gland, the Pancreas, the Parathyroid, the Thymus and the Gonads: Quick Revision

A brief note on The Adrenal Gland, the Pancreas, the Parathyroid, the Thymus and the Gonads. Read it before a test. Try each question at the end before you open its answer.

The adrenal gland

• Medulla: adrenaline and noradrenaline, the catecholamines, the hormones of fight or flight. They raise the heartbeat, the strength of contraction and the rate of breathing, and they raise the glucose.
• Cortex (from outside): zona glomerulosa, zona fasciculata, zona reticularis. Glucocorticoids (cortisol), mineralocorticoids (aldosterone) and small amounts of androgens.
• Cortisol: gluconeogenesis, lipolysis, proteolysis, anti-inflammatory, suppresses immunity. Aldosterone: reabsorbs Na$^+$ and water, excretes K$^+$.
• Addison's disease: lack of the cortical hormones.

The pancreas

• Islets of Langerhans: 1 to 2 million, 1 to 2 per cent of the tissue. Alpha cells make glucagon. Beta cells make insulin.
• Glucagon: hyperglycaemic, glycogenolysis and gluconeogenesis in the liver.
• Insulin: hypoglycaemic, glucose uptake by hepatocytes and adipocytes, glycogenesis.
• Diabetes mellitus: long hyperglycaemia, glucose in the urine, ketone bodies, insulin therapy. One mmol/L of glucose is 18 mg/dL.

Parathyroid, thymus and gonads

• Parathyroid: four glands on the back of the thyroid. PTH raises the calcium (bone, kidney, gut). A low calcium causes tetany.
• Thymus: thymosins, T lymphocytes. It shrinks in old age.
• Testis: interstitial (Leydig) cells make androgens. Ovary: follicles make estrogen, the corpus luteum makes progesterone.

A worked example

A fasting glucose is reported as 6.8 mmol/L. Is it above the cut-off of 126 mg/dL?

1. In mg/dL: $6.8 \times 18 = 122.4$ mg/dL.
2. This is below 126 mg/dL, so it does not reach the cut-off.

Practice with new numbers

A program to try

The program changes a glucose level to mg/dL and compares it with the cut-off.

Mistakes to avoid

• Mixing up insulin and glucagon. Insulin lowers the glucose.
• Saying that adrenaline comes from the cortex. It comes from the medulla.
• Saying that PTH lowers the calcium. It raises it.
• Saying that the corpus luteum makes mainly estrogen. It makes mainly progesterone.

Check yourself

1. Which hormone stimulates glycogenolysis in the liver cells?

2. Which hormone helps the kidney to keep sodium?

3. Which hormone is the main product of the cells that lie between the tubules of the testis?

4. What does a low level of calcium in the blood cause?

Sources

• Betts J. G. et al. (2022). Anatomy and Physiology 2e, OpenStax, chapter 17.
• World Health Organization (2006). Definition and diagnosis of diabetes mellitus and intermediate hyperglycaemia.
• NCERT (2023). Biology, Textbook for Class XI, chapter 19.