Gonads

Endocrine System of Class 11

Gonads are primary sex organs. These are mixed tissues i.e these perform gametogenic function as well as endocrine function.

Testis (male gonads)

Testis perform spermatogenesis as well as endocrine  function.

Testicular hormones

(A) Steroids (secreted by Leydig cells/ interstitial cells)

These are collectively called Androgens and include various hormones like testosterone, dihydrotestosterone and androstenedione.

Testicular steroids are responsible for growth, development and mainitenance of male secondary sex organs, characters & even masculine

behaviour. These also regulate spermatogenesis.

(B) Proteinaceous hormones (secreted by Sertoli cells)

(i) Inhibin : It has negative feedback effect with FSH of anterior pituitary.

(ii) MIS or MIH or MIF (mullerian inhibiting substance/hormone/factor) : It is secreed by foetal testis only. It causes regression of mullerian ducts in case of male embryo.

Ovaries (female gonads)

Ovaries perform oogenesis as well as endocrine function.

Ovarian hormones

(A) Steroids

(i) Estrogens : Estrogens include estrone, estriol and estradiol. Out of these estradiol is maximum. Estrogens regulate growth, development and maintenance of secondary sex organs, characters and even feminine behaviour. These also regulate oogenesis.

(ii) Progestins : Progestins include progesterone and 17OH progesterone. Progesterone inhibits uterine contractions and maintains preganancy.

(B) Proteinaceous hormones

(i) Inhibin : It has negative feedback effect with FSH.

(ii) Relaxin : It relaxes pelvic ligaments of female during parturition & helps in easy birth of baby. Existence of this hormone is contraversial in humans.

Corpus luteum (yellow body)

It is a temporary endocrine gland (reoccuring endocrine gland) formed from remaining cells of Graafian follicle after ovulation.

It secretes various hormones like small amount of estrogens, large amount of progesterone. It also secretes inhibin & relaxin.

Placenta

It is foetomaternal connection formed during pregnancy. It is also a temporary endocrine gland. It secretes various hormones like, estrogens, progestins, relaxin, human chorionic gonadotropin (HCG), Humans Placental Lactogen (HPL), Human (chorionic Somatotropin (HCS), Chorionic Thyrotropin, Chorionic Corticotropin.

Note : HCG is a glycoproteinaceous hormone similar in action to LH. Presence of this hormone in blood or urine of a female is taken as positive test for pregnancy. (The test is Gravidex test)

 
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