ENDOCRINE SYSTEM THYMUS AND ADRENAL GLANDS

Thymus

• located in the upper thorax, posterior to the sternum.

• large in infants, decreases in size throughout adulthood.

• by old age, it is mostly composed of fibrous connective tissue and fat.

produces hormone called thymosin and other hormones that are essential for normal development of T lymphocytes or T cells, and the immune response.

Thymosin

_________ plays a crucial role in the thymus by "training" immature white blood cells (lymphocytes) from the bone marrow to become fully functional T cells

Adrenal Glands

• bean-shaped organs that curve over the top of the kidneys

• considered two endocrine organs in one

has glandular (cortex) and neural tissue (medulla) parts

Corticosteroids

mainly aldosterone

- produced by the outermost adrenal cortex layer

- important in regulating the mineral conteent of the blood, particularly the concentrations of sodium and potassium ions

- help regulate both water and electrolyte balance in body fluids

Adrenal Cortex

is the largest and outer part of the adrenal gland. It is responsible for producing steroid hormones (corticosteroids), aldosterone and a lil sex hormones which are essential for life. The cortex itself is divided into three layers (zones), which can be remembered using the mnemonic GFR for their names

Adrenal Medulla

is the smaller, central part of the adrenal gland, and it is a functional extension of the sympathetic nervous system.

• Hormones Produced: The medulla produces catecholamines, which are often called the "fight-or-flight" hormones.

  • Epinephrine (Adrenaline)

  • Norepinephrine (Noradrenaline)

renin

produced by kidney when blood pressure drops by triggering the formation of angiotensin II

Glucocorticoids

 includes cortisone and cortisol 

- promote normal cell metabolism

- help body resist long-term stressors by increasing blood glucose levels

- said to be hyperglycemic hormones 

- released in response to ACTH

- control effects of inflammation

• decreasing edema

• reduce pain by inhibiting prostaglandins

Sex hormones

• The adrenal glands make small starter pieces of these hormones (like building blocks).

• They are the main reason why boys grow big muscles, get deeper voices, and grow body hair, and why girls develop breasts and other changes when they get older

Addisons’s Disease

• hyposecretion of all adrenal cortex hormones

• characterized by bronze tone of skin

• leads to problems with electrolyte and water balance that causes muscles to become weak

Cushing Syndrome

occurs when client has been receiving pharmacological doses of glucocorticoids to counteract inflammatory disease

• may result in swollen "moon" face and "buffalo hump" or fat on the upper back

• other common effects include high blood pressure, hyperglycemia, etc.

Hyperaldosteronism

• hypersecretion from an ACTH-releasing tumor of the pituitary or from adrenal cortical tumors

• hyperactivity of the outermost cortical area

• results in high blood pressure and edema

CORTICOSTEROIDS, GLUCOCORTICOIDS, SEX HORMONES

HORMONES OF THE ADRENAL CORTEX

Adrenaline/Epinephrine

Increases heart rate and the force of heart contractions. Causes vasodilation (widening) of blood vessels to skeletal muscles and liver. Increases blood glucose (sugar) levels for immediate energy.

Noradrenaline/Norepinephrine

Causes widespread vasoconstriction (narrowing) of blood vessels, especially in the skin and gut. This action significantly increases blood pressure.