The endocrine system is made up of organs that secrete hormones into the blood which in turn control the functions of the body.
Functions:-
They change the permeability of the plasma membrane.
They synthesise enzymes/proteins in the cell.
They play an important role in activating and inactivating enzymes.
They stimulate mitosis.
They also help in promoting secretory activity.
Structure:- They are ductless and release hormones directly into the blood stream
1) Pituitary gland:- It is also known as the master gland because it controls the secretion of all the other glands. This pea sized gland is divided into two parts:-
Anterior Pituitary Gland:- It releases the growth hormone(GH) which controls the growth of the bones and limbs and in turn the height of the individual. Secondly, It releases the hormone prolactin which stimulates the milk production in the breasts of females. Thirdly, it releases the thyroid stimulating hormone(TSH) which controls the production of thyroxine in the thyroid glands. Fourthly, it releases the adrenocorticotropic hormone which stimulates the production of adrenaline in adrenal glands. More so, it produces the follicle stimulating hormone which stimulates the production of ova in ovaries and sperms in testes. Lastly , it produces the luteinizing hormone which stimulates ovulation and the development of secondary sexual characters.
Posterior Pituitary Gland:- It is not exactly an endocrine gland because it does not release any hormone but simply stores the hormones produced by the hypothalamus. It stores oxytocin, which stimulates the contraction of uterus during labour and the Anti-diuretic hormone( ADH) which promotes the retention of water by kidneys.
2) Hypothalamus:- It controls the release of hormones by the anterior pituitary and also releases hormones which are stored in the posterior pituitary gland.
3) Pineal gland:- It secretes melatonin which controls the biological rhythms of the body.
4) Thyroid gland:- It secretes thyroxine(T4) and triidothyronine(T3) which stimulates metabolism. It also secretes calcitonin which reduces the calcium level in the blood by depositing it in the bones.
5) Parathyroid gland:- It performs the opposite function of the thyroid gland by raising the blood calcium levels.
6)Thymus:- It secretes thymosin which helps in building immunity.
7) Adrenal glands:- They are divided into two parts
Adrenal medulla:- It secretes epinephrine( adrenaline) which helps to fight off short term stress by raising the blood glucose level, increasing rate of metabolism and constricting certain blood vessels.
Adrenal Cortex:- It secretes glucocorticoids which increase blood glucose level and help to fight off long term stress. They also secrete mineralocorticoids which promote absorption of Na + ions and excretion of K+ ions.
Also they secrete androgen and oestrogen.
8) Pancreas:- They secrete two hormones. One being insulin which decreases the blood sugar level and the other being glucagon, which raises the blood glucose levels.
9) Gonads:-
Testes:- They secrete testosterone which helps in sperm formation and development of secondary sexual characters.
Ovaries:- They secrete progesterone which promotes the growth of uterine lining and helps in the implantation of the zygote. They also secrete oestrogen which help in the development of secondary sexual characters.
Functions:-
They change the permeability of the plasma membrane.
They synthesise enzymes/proteins in the cell.
They play an important role in activating and inactivating enzymes.
They stimulate mitosis.
They also help in promoting secretory activity.
Structure:- They are ductless and release hormones directly into the blood stream
1) Pituitary gland:- It is also known as the master gland because it controls the secretion of all the other glands. This pea sized gland is divided into two parts:-
Anterior Pituitary Gland:- It releases the growth hormone(GH) which controls the growth of the bones and limbs and in turn the height of the individual. Secondly, It releases the hormone prolactin which stimulates the milk production in the breasts of females. Thirdly, it releases the thyroid stimulating hormone(TSH) which controls the production of thyroxine in the thyroid glands. Fourthly, it releases the adrenocorticotropic hormone which stimulates the production of adrenaline in adrenal glands. More so, it produces the follicle stimulating hormone which stimulates the production of ova in ovaries and sperms in testes. Lastly , it produces the luteinizing hormone which stimulates ovulation and the development of secondary sexual characters.
Posterior Pituitary Gland:- It is not exactly an endocrine gland because it does not release any hormone but simply stores the hormones produced by the hypothalamus. It stores oxytocin, which stimulates the contraction of uterus during labour and the Anti-diuretic hormone( ADH) which promotes the retention of water by kidneys.
2) Hypothalamus:- It controls the release of hormones by the anterior pituitary and also releases hormones which are stored in the posterior pituitary gland.
3) Pineal gland:- It secretes melatonin which controls the biological rhythms of the body.
4) Thyroid gland:- It secretes thyroxine(T4) and triidothyronine(T3) which stimulates metabolism. It also secretes calcitonin which reduces the calcium level in the blood by depositing it in the bones.
5) Parathyroid gland:- It performs the opposite function of the thyroid gland by raising the blood calcium levels.
6)Thymus:- It secretes thymosin which helps in building immunity.
7) Adrenal glands:- They are divided into two parts
Adrenal medulla:- It secretes epinephrine( adrenaline) which helps to fight off short term stress by raising the blood glucose level, increasing rate of metabolism and constricting certain blood vessels.
Adrenal Cortex:- It secretes glucocorticoids which increase blood glucose level and help to fight off long term stress. They also secrete mineralocorticoids which promote absorption of Na + ions and excretion of K+ ions.
Also they secrete androgen and oestrogen.
8) Pancreas:- They secrete two hormones. One being insulin which decreases the blood sugar level and the other being glucagon, which raises the blood glucose levels.
9) Gonads:-
Testes:- They secrete testosterone which helps in sperm formation and development of secondary sexual characters.
Ovaries:- They secrete progesterone which promotes the growth of uterine lining and helps in the implantation of the zygote. They also secrete oestrogen which help in the development of secondary sexual characters.