18.1 - Epiphysis, thymus gland and non-glandular organs with. endocrine functions. Tissue hormones – types, physiological effects and control of secretion.

section

epiphysis

thymus gland

non glandular organs with endocrine function

epiphysis

pineal gland

• Secretes melationin- secretion increases at night

• Role in sleep circardian rhythm

• Inhibits MSH- melanocyte stimulating hormone

• Involutes before puberty, largest in infants

thymus gland

• The gland, is only active until puberty. It is the largest in size at 2 years old

• After puberty, the thymus starts to slowly shrink and become replaced by fat.

• Before birth the thymus is involved in the production and maturation of T-lymphocytes or T cells, it is facilitated by thymosin.

non glandular organs with endocrine function

Placenta:

• Connects mother and fetus.

• Secretes hCG (used in pregnancy tests) to keep the corpus luteum making progesterone.

• Produces estrogen & progesterone to support pregnancy and prepare for breastfeeding.

Skin, Liver, Kidneys:

• Work together to make active vitamin D (calcitriol) when skin is exposed to UV light.

• Calcitriol helps regulate calcium and phosphate levels by acting on bones, kidneys, and the intestines.

Adipose Tissue (Fat):

• Releases adipokines, including:

  • Leptin: Controls appetite.

  • Ghrelin: Stimulates growth hormone release.

Liver & Kidneys:

• Produce erythropoietin (EPO):

  • Stimulates red blood cell production.

  • Aids in wound healing.

Stomach:

• Secretes gastrin:

  • Stimulates stomach acid.

  • Supports growth of stomach lining.

Heart:

• Releases ANP (atrial natriuretic peptide):

  • Causes vasodilation and lowers blood pressure.