Reproductive System Development - Revision history

Kathreid9: /* Primary Sexual Differentiation Phase */

2013-06-11T19:05:07Z

Primary Sexual Differentiation Phase

Kathreid9: /* Primary Sexual Differentiation Phase */

2013-06-11T19:03:47Z

Primary Sexual Differentiation Phase

Bara at 19:09, 28 June 2012

2012-06-28T19:09:52Z

Eca02csb: /* Puberty */

2011-08-22T15:32:29Z

Puberty

Eca02csb: /* Abnormal Reproductive Development */

2011-08-22T15:29:54Z

Abnormal Reproductive Development

Eca02csb: /* Normal Sexual Development */

2011-08-22T15:27:35Z

Normal Sexual Development

Eca02csb: /* Sex Determination in Birds */

2011-08-22T15:25:16Z

Sex Determination in Birds

Eca02csb: /* Introduction */

2011-08-22T15:20:05Z

Introduction

Eca02csb: /* EMBRYOLOGICAL DEVELOPMENT OF THE GENITAL TRACT */

2011-08-22T14:30:01Z

EMBRYOLOGICAL DEVELOPMENT OF THE GENITAL TRACT

Eca02csb: /* Freemartinism */

2011-08-22T14:29:01Z

Freemartinism

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 ===Primary Sexual Differentiation Phase===
-This phase represents the initial phase of differentiation of reproductive tissues. The male Y chromosome in mammals contains genetic code that results in the production of '''testes-determining factor (TDF)''' which is responsible for causing the gonads to develop into testes. In the female fetus, TDF is not produced as there is no Y chromosome and therefore the gonads develop into ovaries. As the testes begin to develop under the influence of TDF, the '''Sertoli cells''' within the testes begin to produce '''Anti-Mullerian hormone (AMH)''' and this has two main effects. It causes the '''Leydig cells''' within the testes to develop which are able to produce testosterone and this testosterone begins the development of the male duct system. Under the influence of AMH these Laydig cells also begin to produce '''dihydrotestosterone''' which, per the above explanation, is also a key signalling molecule in reproductive system development resulting in the development of the penis, scrotum and accessory sex glands. The second key effect of AMH is the regression of the paramesonephric duct system. In females, the lack of TDF and AMH allows the paramesonephric ducts to become the oviducts, uterus, cervix and internal parts of the vagina.
+This phase represents the initial phase of differentiation of reproductive tissues. The male Y chromosome in mammals contains genetic code that results in the production of '''testes-determining factor (TDF)''' which is responsible for causing the gonads to develop into testes. In the female fetus, TDF is not produced as there is no Y chromosome and therefore the gonads develop into ovaries. As the testes begin to develop under the influence of TDF, the '''Sertoli cells''' within the testes begin to produce '''Anti-Mullerian hormone (AMH)''' and this has two main effects. It causes the '''Leydig cells''' within the testes to develop which are able to produce testosterone and this testosterone begins the development of the male duct system. Under the influence of AMH these Leydig cells also begin to produce '''dihydrotestosterone''' which, per the above explanation, is also a key signalling molecule in reproductive system development resulting in the development of the penis, scrotum and accessory sex glands. The second key effect of AMH is the regression of the paramesonephric duct system. In females, the lack of TDF and AMH allows the paramesonephric ducts to become the oviducts, uterus, cervix and internal parts of the vagina.
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 There are a number of genes involved in this stage of bipotential gonadal determination; '''WT-1''', '''SF-1''', '''Lim-1''' and '''EMx-2'''. The development of either the Wolfian ducts is caused by the genes '''SRY''', '''SOX-9''', '''DMRT''' and '''1/2'''. The Mullerian ducts develop as a result of the genes '''DAX-1''' and '''Wnt-4'''.
-===Pimary Sexual Differentiation Phase===
+===Primary Sexual Differentiation Phase===
 This phase represents the initial phase of differentiation of reproductive tissues. The male Y chromosome in mammals contains genetic code that results in the production of '''testes-determining factor (TDF)''' which is responsible for causing the gonads to develop into testes. In the female fetus, TDF is not produced as there is no Y chromosome and therefore the gonads develop into ovaries. As the testes begin to develop under the influence of TDF, the '''Sertoli cells''' within the testes begin to produce '''Anti-Mullerian hormone (AMH)''' and this has two main effects. It causes the '''Leydig cells''' within the testes to develop which are able to produce testosterone and this testosterone begins the development of the male duct system. Under the influence of AMH these Laydig cells also begin to produce '''dihydrotestosterone''' which, per the above explanation, is also a key signalling molecule in reproductive system development resulting in the development of the penis, scrotum and accessory sex glands. The second key effect of AMH is the regression of the paramesonephric duct system. In females, the lack of TDF and AMH allows the paramesonephric ducts to become the oviducts, uterus, cervix and internal parts of the vagina.
 <br />

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 ==Introduction==
 Development of the reproductive system is a complex process relying on numerous systems and conditions to ensure appropriate structures are formed and the rate of development is maintained within the embryo. There are several important criteria that determine appropriate reproductive system development; '''genetic sex''' which determines the sex of the embryo, '''gonadal sex''' and '''phenotypic sex''' which both determine sexual differentiation. Genetic sex determines gonadal sex which in turn determines phenotypic sex. Sex determination relates to the genetic or environmental process which determines the sex of an individual whilst sexual differentiation represents the development of internal and external genitalia.
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+{{OpenPages}}
 [[Category:To Do - Review]]
 [[Category:Developmental Biology]] [[Category:Reproductive System - Anatomy & Physiology]]

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 ==Puberty==
-Puberty is the final stage in the development of the reproductive system and is defined as the period in life where sexual activity commences and the animal becomes physically able to reproduce. There is cyclic activity in the ovaries in the female and the production of spermatozoa in the male. For further information on puberty please see [[Puberty_Defining_-_Anatomy_%26_Physiology|here]].
+Puberty is the final stage in the development of the reproductive system and is defined as the period in life where sexual activity commences and the animal becomes physically able to reproduce. There is cyclic activity in the ovaries in the female and the production of spermatozoa in the male. For further information on the physiology of puberty please see [[Puberty_Defining_-_Anatomy_%26_Physiology|here]]. For information regarding the endocrinology of puberty please see [[Puberty_Endocrine_Events_-_Anatomy_%26_Physiology|here]]. For information regarding the time of onset of puberty, please see [[Puberty_Overview_-_Anatomy_%26_Physiology|here]] and for onset influencing factors please see [[Puberty_Onset_Influencing_Factors_-_Anatomy_%26_Physiology|here]].
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-[[Category:To Do - A&P]]
+[[Category:To Do - Review]]
 [[Category:Developmental Biology]] [[Category:Reproductive System - Anatomy & Physiology]]

← Older revision		Revision as of 15:29, 22 August 2011
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	This abnormal development occurs where is a urethral opening at the base of the penis. This abnormality has been linked to environmental factors.		This abnormal development occurs where is a urethral opening at the base of the penis. This abnormality has been linked to environmental factors.

−		+	==Puberty==
		+	Puberty is the final stage in the development of the reproductive system and is defined as the period in life where sexual activity commences and the animal becomes physically able to reproduce. There is cyclic activity in the ovaries in the female and the production of spermatozoa in the male. For further information on puberty please see [[Puberty_Defining_-_Anatomy_%26_Physiology\|here]].

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 In the female '''alpha-fetoprotein''' binds to estradiol which has been secreted by the fetal ovary. This binding results in the complex being unable to cross the [[Blood_Brain_Barrier_-_Anatomy_%26_Physiology|blood brain barrier]]. This mechanism protects the female brain from the masculinising effects of estradiol and allows the development of a 'feminising' '''surge centre''' at the point of the rostral part of the [[Midbrain_-_Anatomy_%26_Physiology|mesencephalon]].
 ==Normal Sexual Development==
-The development of the reproductive system develops in close proximity and concurrently to the renal system. Throughout normal sexual development there are series of defined phases;
+The development of the reproductive system occurs in close proximity and concurrently to the renal system. Throughout normal sexual development there are series of defined phases;
 ===Pregonadal Phase===
 The pregonadal phase represents the stage where '''germ cells''' begin to migrate from the yolk sac of the developing embryo. Primitive primordial germ cells are formed in the yolk sac (the yolk sac is part of the digestive system in the embryo). These primitive germ cells migrate from the yolk sac through the mesentry to the '''genital ridges''' which are small elongated pieces of tissue beneath the peritoneum situated at the dorsal aspect of the abdominal cavity. These germ cells then begin to divide by mitosis and the gonads are developed from these genital ridges.
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 ====Testicular Descent====
 Testicular descent usually occurs between the middle and the end of detal development. In horses this can be in very late pregnancy or even after birth. In canines it can be up to 8 days post partum. In other species including whales and elephants, the testes will remain in their original positions and do not descend. For further information regarding testicular descent, please see [[Testes_and_Epididymis_-_Anatomy_%26_Physiology#Testicular_Descent|here]].
 ==Abnormal Reproductive Development==
 ===Freemartinism===

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 ==Sex Determination in Birds==
-Birds have sex chromosomes labelled Z and W. The chromosomal requirements for a male in birds is the opposite of that in mammals as the female is the heterogametic species rather than the male. Therefore ZZ results in a male and ZW results in a female.
+Birds have sex chromosomes labelled Z and W. The chromosomal requirements for a male bird are the opposite of that in mammals as the female is the heterogametic species rather than the male. Therefore ZZ results in a male and ZW results in a female.
 ==Sex Determination in Reptiles==
 Crocodilians, marine turtles, some terrestrial turtles and lizards undergo environmental sex determination. The important factor for sex determination in these species is the incubation temperature of the eggs as this determines the development of the gonads towards testes or ovaries. In crocodiles a higher temperature is male determining whilst in turtles a higher temperature is female determining.