`star` Thymus
`star` Adrenal Gland


● The `color{brown}"thymus gland"` is a lobular structure located on the `color{violet}"dorsal side"` of the `color{violet}"heart and the aorta"`.

● The thymus plays a major role in the `color{violet}"development"` of `color{violet}"the immune system"`.

● This gland secretes the `color{violet}"peptide hormones"` called `color{brown}"thymosins"`.

● Thymosins play a major role in the `color{violet}"differentiation of T lymphocytes"`, which provide `color{violet}"cell-mediated immunity"`.

● In addition, thymosins also promote `color{violet}"production of antibodies"` to provide `color{violet}"humoral immunity"`.

● Thymus is `color{violet}"degenerated in old"` individuals resulting in a `color{violet}"decreased production"` of thymosins.

● As a result, the `color{violet}"immune responses"` of old persons `color{violet}"become weak"`.


● Our body has `color{violet}"one pair"` of adrenal glands, one at the `color{violet}"anterior part"` `color{violet}"of each kidney"`.

● The gland is composed of `color{violet}"two types of tissues"`.

● The `color{violet}"centrally located"` tissue is called the `color{brown}"adrenal medulla"`, and outside this lies the `color{brown}"adrenal cortex"`.

● The adrenal medulla secretes two hormones called `color{brown}"adrenaline or epinephrine"` and `color{brown}"noradrenaline or norepinephrine"`.

● These are commonly called as `color{violet}"catecholamines"`.

● Adrenaline and noradrenaline are `color{violet}"rapidly secreted"` in response to `color{violet}"stress"` of any kind and during `color{violet}"emergency situations"` and are called `color{violet}"emergency hormones"` or `color{Brown"hormones of Fight or Flight"`.

● These hormones increase `color{violet}"alertness"`, `color{violet}"pupilary dilation"`, `color{violet}"piloerection"` (raising of hairs), `color{violet}"sweating"` etc. Both the hormones increase the `color{violet}"heart beat"`, the strength of `color{violet}"heart contraction"` and the `color{violet}"rate of respiration"`.

● Catecholamines also stimulate the `color{violet}"breakdown of glycogen"` resulting in an increased concentration of `color{violet}"glucose in blood"`.

● In addition, they also stimulate the `color{violet}"breakdown"` of `color{violet}"lipids and proteins"`.

● The `color{violet}"adrenal cortex"` can be divided into three layers, called `color{brown}"zona reticularis"` (inner layer), `color{brown}"zona fasciculata"` (middle layer) and `color{brown}"zona glomerulosa"` (outer layer).

● The adrenal cortex secretes many `color{violet}"hormones"`, commonly called as `color{brown}"corticoids"`.

● The corticoids, which are involved in `color{violet}"carbohydrate metabolism"` are called `color{brown}"glucocorticoids"`.

● In our body, `color{violet}"cortisol"` is the `color{violet}"main glucocorticoid"`.

● Corticoids, which regulate the `color{violet}"balance of water"` `color{violet}"and electrolytes"` in our body are called `color{brown}"mineralocorticoids"`.

● `color{violet}"Aldosterone"` is the `color{violet}"main mineralocorticoid"` in our body.

● Glucocorticoids stimulate, `color{violet}"gluconeogenesis, lipolysis"` and `color{violet}"proteolysis"`; and inhibit cellular uptake and utilisation of amino acids.

● Cortisol is also involved in maintaining the `color{violet}"cardio-vascular system"` as well as the `color{violet}"kidney functions"`.

● `color{violet}"Glucocorticoids"`, particularly cortisol, produces `color{violet}"anti inflamatory reactions"` and `color{violet}"suppresses the immune response"`.

● Cortisol stimulates the `color{violet}"RBC production"`.

● `color{brown}"Aldosterone"` acts mainly at the `color{violet}"renal tubules"` and stimulates the `color{violet}"reabsorption"` of `Na^+` and water and `color{violet}"excretion"` of `K^+` and phosphate ions.

● Thus, aldosterone helps in the `color{violet}"maintenance of electrolytes"`, `color{violet}"body fluid volume"`, `color{violet}"osmotic pressure"` and `color{violet}"blood pressure"`.

● Small amounts of `color{violet}"androgenic steroids"` are also secreted by the `color{violet}"adrenal cortex"` which play a role in the growth of `color{violet}"axial hair"`, `color{violet}"pubic hair"` and `color{violet}"facial hair"` during puberty.