Reproductive System Introduction MBBS.pptx

Introduction to reproductive system, sex differentiation and puberty

1. Reproductive System Introduction Dr Anupama Deepak

2. Introduction Reproduction is essential for the continuation of species If any species loses the ability to reproduce, it would become extinct very soon All mammals including man reproduce by sexual means This involves the fusion of two gametes The sperm is produced by male while ovum is produced by female

3. Male Reproductive System

4. Organ Location Function Scrotum External Supports testes and regulates their temperature Penis External Delivers urine, copulating organ Testes Primary Gonad Produce sperm and male hormones Epididymis Internal Maturation and storage space for sperm Va s Deferens Internal Transporatation of sperm Accessory Glands Location Function Seminal Vesicles Internal Contribute to semen production Prostate Gland Internal Contributes to semen production Bulbourethtral Glands Internal Neutralize urine in urethra Male Reproductive Organs

5. Female Reproductive Anatomy Organ Location Function Clitoris External Sensory organ Mons pubis External Fatty area overlying pubic bone Labia majora External Covers labia minora; contains sweat and sebaceous glands Labia minora External Covers vestibule Greater vestibular glands External Secrete mucus; lubricate vagina Breast External Produces and delivers milk Ovaries Primary Gonad Produce and develop eggs Oviducts Internal Transport egg to uterus; site of fertilization Uterus Internal Supports developing embryo Vagina Internal Common tube for intercourse, birth canal, passing menstrual flow

6. Development of Reproductive organs-Sex Determination And Differentiation Multiple differences between male and female depend primarily on a single chromosome “Y” Presence of Y chromosome- primitive gonads differentiate into testes Absence of Y - ovaries develop Formation of male genitalia depends on the presence of a functional, secreting testis In absence of testicular tissues, development is female

7. Sex Determination And Differentiation There are four terminologies to be understood: Chromosomal sex – “XX” or “XY” Gonadal sex – “ovaries” or “testis” Genital sex – primary genitals ( internal, external) and secondary sexual characters of female or male Psychological sex – thought and sexual behavior of the person

8. Sex Determination Genetic differentiation Genotype of fetus – male or female is determined by sex chromosomes Human chromosomes – each cell in normal adult male and female possesses 46 chromosomes (44 autosomes + 2 sex chromosomes) Females – 44 autosomes + XX Males – 44 autosomes + XY

9. Sex Determination Mature gametes – Haploid Males – sperms – 22 autosomes + 1 sex chromosomes (X or Y) Females – ova – 22 autosomes + 1 Sex chromosomes (X or X)

10. Genetic Sex Determination Occurs during fertilization 44XX 44XY

11. Gonadal Differentiation Bi-potential gonads begin to differentiate into testes at approx. 6 th week- in the presence of Y chromosome which codes for Testis determining factor(TDF) Absence of Y - ovaries develop

12. Genital Differentiation Also known as phenotypic sex differentiation It refers to differentiation of internal genitalia, urethra, external genitalia Internal genitalia develop from paired set of ducts known Wolffian and Mullerian ducts

13. Differentiation of internal genitalia In genetic male fetus – functioning testes , testosterone and Mullerian inhibiting substance (MIS) are secreted Testosterone from leydig cells stimulate the wolffian ducts to form epididymis , vas deferens, seminal vesicles MIS from sertoli cells causes regression of the mullerian ducts In females in the absence of testosterone- Mullerian ducts develop to form female internal genetalia

14. Differentiation Of External Genitalia Male fetus – functional testes secreting testosterone and dihydrotestosterone , external genitalia acquire male charecteristics by 5 th month of gestation Female fetus – in absence of any hormone , external genitalia differentiation occurs along the female line

15. Differentiation Of External Genitalia -- Male

16. Differentiation Of External Genitalia --Female

17. Psychological Differentiation Difference in male and female behavior is due to Some anatomical and functional differences in certain areas of brain Effect of androgens on the development of brain in the embryo- male behavior during puberty Absence of androgenic exposure of fetal hypothalamus in female embryo causes it to stimulate anterior pituitary in a cyclic way as in adult females

18. Chromosomal Abnormalities Klinefelter syndrome Turners syndrome

19. Puberty and Adolescence

20. Difference between Puberty and Adolescence??

21. Puberty is the process of physical transition, adolescence is about a psychological and social transition.

22. It is the period when the endocrine & gametogenic functions of the gonads have first developed to the point where reproduction is possible. Age of onset – in developing countries onset is 11-16 yrs in girls and 13-18 yrs in boys. Definition

23. 1) Gonadotrophin Releasing Hormone (GnRH)- before puberty , hypothalamus is more sensitive to the inhibitory effects of adrenal steroids & this keeps the release of hypothalamic GnRH under check. At puberty this negative feedback effect of steroids decreases. It is proposed that this pulsatile secretion of GnRH brings about the onset of puberty. Control of onset of puberty

24. 2) Role of Leptin- it is a hormone secreted from the adipose tissue cell & is believed to help in the maturation of hypothalamic-gonadal axis. It has been observed that the body weight increases to a critical level before the onset of puberty, especially in females.

25. Body configuration- broad shoulders, more muscular body Hair growth- male pattern of pubic hair. Hair appears all over body, axilla , face and chest Voice- becomes deep & breaks External & internal genitalia – adult pattern Skin changes – acne appears due to increased secretion from sebaceous glands Psychological changes – aggressive, active attitude, interest in opposite sex develops Pubertal Changes in males

26. Body configuration : narrow shoulders, broad hips, female fat distribution in breast & hips. Hair growth : less body hair & more scalp hair Voice : high pitched voice External & Internal genitalia : Adult pattern Skin changes : acne formation is less as estrogen antagonizes the action of androgen on sebaceous glands Psychological changes : changes in mental & emotional behaviour , shyness, interest in opposite sex develops Pubertal changes in females

27. 1) Precocious puberty – True precocious puberty Precocious pseudopuberty 2) Delayed puberty- Abnormalities of puberty

28. True precocious puberty : early development of secondary sexual characteristics that may be associated with premature development of gonads. Due to following causes- a) Hypothalamic precocity- tumor or infection of hypothalamus that causes premature increased secretion of GnRH . Precocious puberty

29. b) Gonadotropin independent precocity- occurs due to increased sensitivity of LH receptors to gonadotropins c) Constitutional precocity – actual cause cannot be ascertained

30. Precocious Pseudopuberty : the development of secondary sexual characteristics without gametogenesis . Occurs due to exposure of immature males to abnormal quantity of androgen, & females to estrogen. Causes- Adrenal causes- congenital virilizing adrenal hyperplasia, androgen or estrogen secreting tumor of adrenal gland Gonadal causes- Leydig cell tumor of testis or granulosa cell tumor of ovary.

31. Onset of puberty is delayed beyond the age of 17 yrs in girls and 20 yrs in boys. It occurs due to – Panhypopituitarism that causes failure of maturation of gonads Associated with chromosomal abnormality of XO pattern (Turner’s syndrome) or gonadal dysgenesis Delayed puberty

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