Changes

===Oxytocin (OT)===

===Oxytocin (OT)===

OT is a neuropeptide (a octapeptide) which is synthesised in the '''hypothalamus''' and stored in the posterior pituitary. OT can also be synthesised by the corpus luteum. In males the target tissue for OT is smooth muscle within the epididymal tail, ductus deferens and the ampulla. In females OT targets the uterine myometrium and endometrium together with cells of the mammary glands. In the male OT stimulates PGF2α synthesis and facilitates the pre-ejaculatory movement of spermatozoa. In females, OT stimulates uterine motility and the synthesis of PGF2α from the uterus. It also begins milk 'let-down' or ejection.

OT is a neuropeptide (a octapeptide) which is synthesised in the '''hypothalamus''' and stored in the posterior pituitary. OT can also be synthesised by the corpus luteum. In males the target tissue for OT is smooth muscle within the epididymal tail, ductus deferens and the ampulla. In females OT targets the uterine myometrium and endometrium together with cells of the mammary glands. In the male OT stimulates PGF2α synthesis and facilitates the pre-ejaculatory movement of spermatozoa. In females, OT stimulates uterine motility and the synthesis of PGF2α from the uterus. It also begins milk 'let-down' or ejection.

===Oestradiol (E₂)===

===Estradiol (E₂)===

E₂ is a steroid that is produced by the '''granulosa cells''' of a follicle, the placenta and the testes. In males the target tissue is the brain for maturation of the male brain during foetal development. E₂ in the male also inhibits long bone growth. In females the target tissues are the hypothalamus, the entire female reproductive tract and the mammary glands. The primary action of E₂ in males is the appropriate development of male sexual behaviours whilst in females it influences sexual behaviour, GnRH levels, the secretory activity of the reproductive tract and enhances uterine motility.

Estradiol (E₂) is a steroid hormone and is part of the oestrogens group of hormones and is the principle oestrogen in females. '''Estrone''' and '''estriol''' are chemically similar to estradiol but are found in lower concentrations and have a lower estrogenic activity. Production of oestrogens occurs in the ovary via '''granulosa cells''', the placenta and the adrenal cortex. In males in it is produced in sertoli cells found in the testes. Estradiol is synthesised from cholestrol.

Oestrogens have a number of functions related to reproduction and other areas of physiology. In relation to the reproductive role of oestrogens, they stimulate follicular growth and maturation, induce the female to begin displaying oestrous behaviour to facilitate mating, prepare the external genitalia for copulation and create favourable conditions for the development of fertilised egg cells. Oestrogens also contribute to the growth and development of mammary tissue and prepare the uterus for parturition.

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Where oestrogens stimulate growth of follicles in the ovaries, oestrogens secreted from the ovary in the [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Follicular_Phase|follicular phase]] ([[Oestrous_Cycle_-_Anatomy_%26_Physiology#Pro-Oestrus|proestrous]] and [[Oestrous_Cycle_-_Anatomy_%26_Physiology#Oestrus|oestrous]]) lead to hypertrophy of the epithelium and the endometrium. Secretory glands within the uterus enlarge and secretion is initiated leading to thickening of tissues. The blood vessels supplying the uterus and external genitalia dilate and blood flow to these areas increases significantly. Oedema occurs within the uterus and surrounding connective tissues. Oestrogen also causes increased uterine muscle tone. In the cervix oestrogens stimulate increased mucus secretion and the vaginal epithelium becomes keratinised.

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In males the target tissue is the brain where it causes maturation of the brain during development. This maturation process ensures the appropriate development of male sexual behaviours. E₂ in the male also inhibits long bone growth.

 

===Progesterone (P₄)===

===Progesterone (P₄)===

Progesterone is a steroid hormone that is produced by the corpus luteum and the placenta. In males the target tissues are the accessory sex glands, the tunica dartos (scrotum), the seminiferous tubules and skeletal muscles. In females the target tissues are the uterine endometrium, the mammary gland, the myometrium and the hypothalamus. Progesterone results in increased endometrial secretions and inhibits the release of GnRH in females. It also inhibits female reproductive behaviour as well as acting to maintain a pregnancy. Progesterone has no primary action in the male.

Progesterone is a steroid hormone that is produced by the corpus luteum and the placenta. In males the target tissues are the accessory sex glands, the tunica dartos (scrotum), the seminiferous tubules and skeletal muscles. In females the target tissues are the uterine endometrium, the mammary gland, the myometrium and the hypothalamus. Progesterone results in increased endometrial secretions and inhibits the release of GnRH in females. It also inhibits female reproductive behaviour as well as acting to maintain a pregnancy. Progesterone has no primary action in the male.