· Gonads, ovaries in female and testes in the male apart from producing spermatozoa and ova, also function as endocrine glands. They produce the chemicals called as hormones which transmit the signal to the target cells.
· There are two types of gonads:
· Ovary is ductless reproductive gland in which the female reproductive cells are reproduced.
· Ovary is a primary sex organ in females that serve to produce ova (female gamete) and female sex hormones.
· In females, a pair of ovaries located in the pelvic cavity, one on each side of the lower part of the abdomen
Each ovary is small glandular organ about a size and shape of almond.Internally it is composed of ovarian follicles and stromal tissues. During ovulation, a follicle (a small cavity in the ovary) expels an egg under the stimulation of gonadotrophic hormone (released by the pituitary gland), the luteinizing hormone and the Follicle stimulating hormone (FSH). The rest of the follicle or corpus luteum secretes sex hormones oestrogen and progesterone, which regulates menstruation and control the development of sex organs; they are gonadotrophic hormones interact with each other to control menstrual cycle. Ovary is needed for reproduction since it is responsible for producing female reproductive cells or ova.
· Ovary produces two groups of steroid hormones i.e. estrogen and progesterone.
· Estrogen is secreted by granulosa cells of graffian follicles.
· After ovulation, the ruptured follicle is converted to another structure called corpus luteum which is responsible for secretion of Progesterone.
Function of Hormones:
At puberty, these hormones regulate the growth and development of secondary female sex organs like uterus and mammary glands and of female accessory sex characters like deposition of fat on thighs and the female pattern of pubic hair deposition. They also maintain the normal function of the secondary sex organs and control their changes during menstrual cycle and pregnancy. Both estrogen and progesterone play an important role in various processes in females. These are as follows:
· Estrogen helps in the growth of uterine endometrium layer during each menstrual cycle.
· It directly influences the development of mammary glands.
· It regulates female’s sexual behaviour and stimulates the growth and activities of secondary sex organ of female.
· It plays an important role in the development of growing ovarian follicles.
· It helps in the appearance of female secondary sexual characteristics.
· This hormone is secreted in very high amount continuously during pregnancy.
· It also acts on mammary glands and stimulates the formation of alveoli.
· It also helps in forming a mucus plug at cervix.
· Another hormone from the ovary is relaxin which is peptide hormone.
· This hormone is secreted by ovary in later stages of pregnancy.
· The main role of this hormone is in softening of ligament, widening of pelvic cavity.
· This also affects other ligaments such as foot, due to which women may experience increase in their foot size during pregnancy.
· This hormone softens the pelvic ligament so that childbirth can take place easily.
· Testes are the primary sex organ in males.
· Testes is also known as testicles or male gonads.
· In humans each testes weighs about 25gm and 4-5 cm long and 2-3 cm in diameter.
· They perform dual role i.e. function as a endocrine gland apart from acting as male sex organ
· Testes secrete male sex hormone called androgens of which testosterone is the principle one.
· The androgens are all steroid.
· At puberty, testosterone stimulates the growth and development of male secondary sex organs like prostrate and seminal vesicles and also male accessory sex characters like deepening of voice, broadening of shoulders and the male pattern distribution of pubic hair.
· It also maintains the male secondary sexual characteristics.
A pair of testes is located in the scrotal sac (outside the abdomen) of male individual.
Testes are lie behind the penis in a pouch of skin called as scrotum. The testes move freely in the scrotum but each testis is attached to the body wall by a thin cord called the spermatic cord, which passes through a cavity in the pelvis and into the abdomen. The cord contains the nerves and blood vessels for the testes as well as vasa deferens, which carries the sperm from the testes into the urethra; it is the passageway for sperm to the outside of the body at ejaculation. Testes contain germ cells that differentiate into mature spermatozoa supporting cells called as sertoli cells and testosterone producing cells called leydig’s cells. The seminiferous tubules in which the sperms are produced constitute about 90% of the testicular mass. In the young male the tubules are simple and compound of underdeveloped sperm producing cells (spermatogonia) and the sertoli cells.
A testis is composed of many seminiferous tubules which are lined by germinal epithelium and stromal or interstitial tissue. This epithelium consists of three types of cells:
a) Follicular cells; give rise to sperms
b) Interstitial cells or leydig’s cells; secretes group of hormones called androgens mainly testosterone
c) Sertoli cells provide nourishment to sperms and also secretes inhibin hormone.
Interstitial cells present in the inter-tubular spaces which produces a group of hormones i.e. androgens. This includes testosterone, dihydrotestosterone and androsteredione, but mainly secretes testosterone.
Function of Hormones:
Androgens mainly testosterone performs following functions:
a) Testosterone is the main hormone secreted by the cells of testes that lie between the seminiferous tubules; these cells are known as leydig’s cells.
b) Regulates the development, maturation and function of male accessory organ like epididymis, vas deferens, seminal vesicles, prostrate gland, urethra etc.
c) It also stimulates changes associated with puberty in male i.e. muscular growth, growth of facial and axillary hair, aggressiveness, low pitch of voice etc.
d) It also stimulates the process of spermatogenesis i.e. formation of spermatozoa.
e) Promotes the growth of body tissues such as bones and muscles.
f) It helps in the formation of masculine body.
g) It has anabolic effects or synthetic effect on the metabolism of protein and carbohydrate.
Besides testosterone another hormone is secreted from the sertoli cells of testes known as inhibin hormone. The main function of inhibin hormone is to regulate the over-activity of testosterone by inhibiting its secretion.
III. Anti- Mullerian hormone:
This hormone is produced by the sertoli cells of testes.
IV. Insulin like factor 3 and Oestradiol:
They are also produced by the leydig’s cells of testes. Oestradiol help in maintaining the health of reproductive organ and facilitates fertilization in women.
Endocrine glands are ductless glands and their secretions are known as Hormones. They are chemical messengers which are secreted in trace amounts and affects the target organ of the body.
Pituitary gland release several hormones which regulate the functioning of different parts of the body. Growth hormone, PRL, TSH, ACTH, LH, FSH, MSH, oxytocin and vasopressin are the hormones released by the pituitary gland.
Thyroid glands are located in our neck region and secretes thyroxine, TCT and calcitonin hormone. On the other hand Parathyroid gland is located on the posterior side of thyroid gland and release PTH.
Adrenal glands are supra-renal glands which consists of two parts; cortex and medulla which releases certain hormones to regulate the process of human body.
Pancreas is a composite gland which function as both exocrine and endocrine gland. The endocrine pancreas consists of islets of langerhans. Alpha cells of pancreas secretes glucagon and beta cells release insulin.
Thymus gland is a lymphoid organ that secretes the peptide hormone thymosin. Thymus gland promotes the development of specific cell of the immune system called as T- lymphocytes.
Pineal gland is an endocrine gland found in the cerrebral ventricle in the brain midline. Pineal gland release melatonin hormone which controls circadian rhythm of the body.
Hypothalamus is the basal part of the brain which contain neuro-secretory cells called nuclei These nuclei produce hormones which regulate the functioning of pituitary hormones.