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Introduction Reproductive System. Dr. Amel Eassawi. Objectives. Know the functional anatomy of male & female reproductive system. Describe how the chromosomal content determines the sex of an embryo and how this relates to the development of testes or ovaries.

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objectives
Objectives
  • Know the functional anatomy of male & female reproductive system.
  • Describe how the chromosomal content determines the sex of an embryo and how this relates to the development of testes or ovaries.
  • Explain how the sexual differentiation along male & female lines depends on the presence or absence of masculinizing determinants.
  • Discuss the abnormalities on sexual differentiation.
reproductive system
Reproductive System
  • Depends on union of male and female gametes to form new individual.
  • Male and female reproductive systems designed to enable union of genetic material.
reproductive system1
Reproductive System

Components of Reproductive System:

1. Primary reproductive organ (Gonads)

2. Reproductive tract

3. Accessory sex glands

4. External genitelia

reproductive system2
Reproductive System

Secondary Sexual Characteristics:

  • External characteristics not directly involved in reproduction that distinguish males and females
    • Body configuration and hair distribution
    • Governs by testosterone and estrogen
    • Males have broader shoulders and beards
    • Females have curve hips and no beards
    • Progesterone has no influence on secondary sexual characteristic.
slide7

Male

Reproductive

System

reproductive system3
Reproductive System

1. Primary Reproductive Organs (gonads)

    • Pair of testes in male.
    • Pair of ovaries in female.
  • Functions of Mature Gonads
    • Producing gametes (gametogenesis)
      • Spermatozoa (sperm) in male.
      • Ova (eggs) in female.
    • Secreting sex hormones
      • Testosterone in males.
      • Estrogen and progesterone in females.
reproductive system4
Reproductive System

2. Reproductive Tract:

  • System of specialized ducts that transport or house gametes after they are produced.

3. Accessory Sex Glands:

  • Empty supportive secretions into reproductive tract.

4. External Genitalia:

  • Externally visible portions of reproductive system.
male reproductive system
Male Reproductive System

Functions and Organs:

Testes

Function: Production of sperm (spermatogenesis).

Secretion of testosterone.

Accessory Sex Glands

  • Seminal vesicles, prostate gland, bulbourethral gland

Function:Secretions provide bulk of semen (liquid substance that is conducive to sperm viability)

Penis

Function: Organ used to deposit semen in female

Male Reproductive Tract

  • Epididymis, ductus (vas) deferens

Function:Sperm maturation

  • Ejaculatory duct

Function: Empty into urethra (canal running length of penis that empties into exterior)

slide11

Female

Reproductive

System

female reproductive system
Female Reproductive System

Functions and Organs

Ovaries

Function:Production of ova (oogenesis).

Secretion of estrogen & progesterone.

Female Reproductive Tract

  • Oviducts (uterine or Fallopian tubes)

Function: Pick up ova on ovulation, serve as site for fertilization

  • Uterus

Function:

    • Responsible for maintenance of fetus during development
    • Responsible for expelling fetus at end of pregnancy
    • The lower portion of the uterus is the cervix(projects in the vagina and contain single, small opening the

cervical canal

Function:

Serves as pathway for sperm through the uterus to the site of fertilization

Serves as passageway for delivery of baby from uterus

female reproductive system1
Female Reproductive System

Vagina

Function:Connects uterus to external environment

  • Vaginal opening

Located in perineal region between urethral opening and anal opening

Partially covered by thin mucous membrane, hymen

  • Labia minora and labia majora

Skin folds that surround vaginal and urethral openings

  • Clitoris

Small erotic structure located at anterior end of folds of labia minora

Vulva

  • Collective term for female external genitalia
reproductive cells
ReproductiveCells

Body (somatic) cells

  • Contain 46 chromosomes (diploid number)
  • Can be sorted into 23 homologous pairs

Gametes (sperm and egg)

  • Have 23 chromosomes (haploid number)
  • Contains only one member of each homologous pair of chromosomes
  • Gametogenesis is accomplished by meiosis
reproductive cells1
Reproductive Cells

Autosomes

  • 22 pairs which code for general human characteristics and specific traits. (example eye color)

Sex chromosomes

  • Remaining pair of chromosomes
  • Two genetically different types
    • Larger X chromosome
    • Smaller Y chromosome
sex determination
Sex Determination
  • Depends on combination of sex chromosomes
  • Genetic female

Has two X chromosomes

  • Genetic male

Has an X and a Y chromosome

Y chromosome

  • Responsible for all the anatomical and functional distinctions between males and females

Genetic sex

  • Determined at time of conception
  • Depends on which type of sex chromosome is contained within the fertilizing sperm
sex determination1
Three levels of differences between males and females

Genetic

Depends on combination of sex chromosomes at time of conception

Gonadal

Whether testes or ovaries develop

Presence or absence of Y chromosome determines gonadal differentiation

Phenotypic

Apparent anatomic sex of individual

Determined by gonadal sex

Sex Determination
time sequence of human sexual differentiation in males females
Time Sequence of Human Sexual Differentiation in Males & Females
  • The gonads (both XY and XX genotypes) are bipotential at seven weeks of gestation.
  • In males, testicular differentiation begins after the seventh week of gestation.
  • Primitive sertoli-like cells in the developing testis secrete AMH and regression of the Mullerian ducts begins at around 60 days of gestation.
  • Differentiation of the Wolfian ducts in response to testosterone begins at 63-70 days of gestation in males and meoisis signals the beginning (60-70 days) of ovarian differentiation in females.
  • Differentiation of the male external genitalia occurs during the 9-13 weeks of gestation in response to DHT.
  • Androgen induced brain differentiation may occur via its conversion to estrogen in the target tissue.
male sexual differentiation
Male Sexual Differentiation
  • The first step toward sexual differentiation is action of the SRY gene product on primordial germ cells (PGC) to start testicular differentiation. The SRY gene is found distal to the ZFY gene on the Y chromosome of males. Subsequently, the PGC and associated cells start organizing into testicular-like structures
  • Sertoli cells (or Sertoli precursor cells) secrete AMH which causes regression of the adjacent Müllerian duct.
  • Leydig (or Leydig precursor cells) secrete testosterone which induces differentiation of the Wolffian ducts into the internal secondary sex organs.
  • The external secondary sex structure differentiation occurs in response to DHT (dependent on the presence of 5DHT reductase in the target tissues).
urogenital 5 reductase activity during differentiation1
UROGENITAL 5α REDUCTASE ACTIVITY DURING DIFFERENTIATION

1. 5 α DHT reductase must be present at adequate levels in cells of precursor structures during the critical 9 – 13 week period of gestation in order for differentiation into male external genitalia.

2. An absence of this enzyme in male fetuses during that period (5 αreductasedeficiency) leads to female appearing external genitalia.

fetal plasma gonadotropins androgen testis development
Fetal Plasma Gonadotropins, Androgen & Testis Development
  • The decline in fetal gonadotropin levels after the first trimester leads to a decrease in numbers of Leydig cells and a reduction of seminiferous tubule growth
  • Proliferation of Leydig cells and tubule development is associated with elevated fetal gonadotropin levels.
ovarian development during fetal growth
OVARIAN DEVELOPMENT DURING FETAL GROWTH
  • The first primordial follicles appear near the fourth month of gestation.
  • The last oogonia enter meiosis at seven months of gestation.
  • Around 2M follicles are present at birth and folliculogenesis is completed at six months post-partum
male sexual differentiation summary
Male Sexual Differentiation Summary
  • Testicular differentiation is mediated by TDF (TIF).
  • The first endocrine function of the fetal testis is secretion of AMH (MIF).
  • Dihydrotestosterone stimulates (mediates) differentiation of the urethra, prostate, and external genitalia.
  • Testosterone mediates differentiation of the Wolffian ducts and associated internal secondary sex structures.
  • Fetal testosterone reaches peak plasma levels at 16 weeks of gestation.
  • hCG and fetal LH are important for continued growth of the penis and testis during the second and third trimesters.
female sexual differentiation summary
Female Sexual Differentiation Summary
  • In the absence of TDF, gonadal cells have an inherent tendency to form ovarian-like structures.
  • In the absence of androgens an inherent tendency for formation of female secondary structure exists.
  • Interstitial steroidogenic cells appear at 12 weeks of gestation.
  • Oogonia formation is complete at 7 months of gestation.
  • Approximately two million follicles are present in the new-born ovary.
  • Primordial follicle development is completed at six months post-partrum.
errors in sexual differentiation1
Errors in Sexual Differentiation

Discrepancies occur between genetic and anatomic sexes

Pseudo hermaphrodite:

  • Gonad of one sex and genitalia of other

1. Male Pseudo Hermaphrodite:

    • Genetic males whose target cells lack receptors for testosterone are feminized ( testicular feminizing syndrome)
    • Defective testicular development
    • 5α reductsae deficiency ( enzyme, coverts testosteron to DHT)
  • Female phenotype & XY male genotype
errors in sexual differentiation2
Errors in Sexual Differentiation

2. Female Pseudo Hermaphrodite:

  • Congenital adrenal hyperplasia
  • Administration of androgen to mother
  • Male phenotype and XX female genotype
slide34

(Turner’s syndrome)

Four possible defects produced by maternal non-disjunction of the sex chromosomes at the time of meiosis

(Klinefelter’s syndrome)

references
References
  • Human physiology, Lauralee Sherwood, seventh edition.
  • Text book physiology by Guyton &Hall,11th edition.
  • Text book of physiology by Linda .s Contanzo, third edition.
  • Physiology by Berne and Levy, sixth edition.