Endocrine System Overview

Thyroid

• Located on either side of the trachea, in front of the 2nd-4th tracheal rings.
• H-shaped and weighs approximately 25 grams (20-25 grams).
• Crucial for stimulating basal metabolic rate, protein synthesis, and increasing metabolic rate.
• Plays a role in glucose synthesis, lipolysis, and the development of the brain and gonads.

Triiodothyronine (T3) and Thyroxine (T4)

• T3 is approximately four times more active than T4.

Parathyroid

• Located on the dorsal part of the thyroid.
• Resembles a grain of rice and weighs approximately 30 milligrams.
• Plays a crucial role in increasing blood calcium levels by facilitating reabsorption in the intestines and kidneys.
• Lowers blood phosphate levels and activates vitamin D.

Calcitonin/Thyrocalcitonin/Parathormone

• Decreases blood calcium levels.

Thymus

• Located on each side of the trachea, just above the heart.
• Secretion is temporary and it is important for the formation of lymphocytes and antibodies.
• Plays a significant role in developing the immune response.

Islets of Langerhans

• Found within the pancreas (1-2%).
• a-cell: Produces Glucagon, which increases blood glucose by breaking down glycogen.
• B-cell: Produces Insulin, which reduces blood glucose by increasing glycogen synthesis.
• y-cell: Produces Pancreatic polypeptide.
• 8-cell: Produces Somatostatin, which reduces appetite.

Adrenal or Suprarenal

• Located above the kidney, covered by renal fascia or serosa fascia.
• Hat-like shaped and weighs around 7-10 grams.

Cortex (80%)

• Produces Glucocorticoid (Cortisol, Cortisone, Corticosterone), Mineralocorticoid (Aldosterone), and Gonadocorticoid (Estrogen, Androgen, Progesterone).
• Glucocorticoids: Regulate carbohydrate metabolism, stimulate glycogen synthesis in the liver and muscles, facilitate the absorption of sugar and lipids, prevent phagocytosis, chemotaxis, and allergy, and reduce antibody production.
• Mineralocorticoids: Regulate mineral salt metabolism, increase NaCl and water absorption, increase kidney capacity, increase plasma in blood, and increase K excretion rate.
• Gonadocorticoids: Regulate sexual differentiation of the embryo.

Pineal

• Located in the 3rd ventricle of the brain.

Testes

• Located in a sac outside the body cavity in the male body called the scrotum.

Ovary

• Located on the wall of the pelvic cavity in the female, on both sides of the uterus.

Placenta

• Plays a crucial role in pregnancy and childbirth.

Hormones

Adrenaline (Epinephrine) / Crisis/Emergency Hormone

• Releases glucose from glycogen stored in the liver and increases metabolic rate.
• Regulates body temperature.
• Controls involuntary muscle contraction of the heart and arteries.
• Increases heart rate.
• Plays a role in expressing fear, joy, and grief.

Nor-adrenaline (Norepinephrine)

• Stimulates heart muscle, increasing blood pressure.
• Converts excess glucose in the body into glycogen.

Dopamine

• Acts as a neurotransmitter.
• Accelerates phosphorus metabolism.
• Regulates sleep.
• Stimulates (activates) sexual organs.
• Regulates the biological clock.

Testosterone

• Enlarges male genital organs.
• Facilitates the expression of secondary sexual characteristics.
• Contributes to the continuation of sperm production.
• Stimulates the production of red blood corpuscles (RBC) in the red bone marrow.

Estrogen

• Helps in the expression of various sexual characteristics of the female during puberty.
• Regulates the menstrual cycle.
• Causes rapid RNA synthesis in the uterus tissue, controlling the growth of the uterus, fetus, and placenta during pregnancy in the female.

Progesterone

• Helps maintain pregnancy and normal growth of the mother's body and fetus during pregnancy.

Human Chorionic Gonadotropin (hCG)

• Plays a significant role in pregnancy.

Human Chorionic Somatomammotropin (hCS)

• Plays a significant role in pregnancy.

Relaxin

• Facilitates parturition (childbirth) at the end of pregnancy.

Prolactin

• Acts as a supplement to ovarian estrogen.

Progesterone

• Acts as a supplement to ovarian progesterone.

Placenta

• Plays a significant role in pregnancy by producing hormones.

Proteinaceous (Protein containing)

• A type of hormone.

Steroidal (Steroid containing)

• A type of hormone.

Pineal

• Located in the 3rd ventricle of the brain (Diencephalon).

Testes

• Located in a sac outside the body cavity in the male body called the scrotum.

Ovary

• Located on the wall of the pelvic cavity in the female, on both sides of the uterus.

Test your knowledge on the anatomy and functions of the thyroid, parathyroid, and thymus glands. This quiz covers their roles in metabolism, calcium regulation, and immune function. Dive into the essential hormones like T3, T4, and calcitonin.