Male and Female sex organs consists of three sets of structuresL
1. The Gonads: The organs that produced gametes (cells that unite to form new individuals)
a. Male gonads = the testes which produce the sperm
b. Female gonads = the ovaries which produce the eggs
c. Undifferentiated cells that become gamete = germ cells
2. The Internal Genitalia: Accessory glands and ducts that connect the gonads with the outside
environment
3. The External Genitalia: External reproductive structures
All cells other than the gametes, contain 46 chromosomes. Cells with 46 chromosomes are labeled as
diploid cells.
- 22 matching pairs of autosomes
- 1 pair of sex chromosomes
- Gametes contain 23 chromosomes. They are labeled as haploid cells.
Sex Determination
Sex is determined based on the sex chromosome provided by the father’s gamete.
- The mother has only XX chromosomes, and can only provide X chromosomes to offspring.
- Father has both X and Y chromosomes, only one is passed onto offspring.
- Males receive Y from father, Females receive X from father.
Abnormalities in sex chromosome inheritance can occur as follows:
- XXY → will become male, because of possession of Y chromosome
- Y → will die, because X is essential to the development of any sex.
- X → Turner’s Syndrome → will survive with abnormal female reproductive function
Once the ovaries develop in a female fetus, one X chromosome is inactivated in each cell of her body,
condensed into a Barr Body.
,Sexual Differentiation (see next page)
Before differentiation the embryonic tissues are bipotential, they cannot be identified as morphologically
male or female.
- The bipotential gonad has: Outer gonadal cortex and inner gonadal medulla:
- In females, cortex becomes ovaries, medulla regresses
- In males, cortex regresses, medulla becomes testes
- The bipotential internal genitalia has: Wolffian ducts and Mullerian Ducts
- Absence of presence of one depends on male/female signals
- The bipotential internal genitalia has:
- Genital tuburcles: becomes clitoris, becomes glans penis
- Urethral folds & groove: becomes labia minora, vaginal opening, becomes penis shaft
- Labioscrotal swellings: form labia majora, form shaft and scrotum
, Sex determination depends on the presence or absence of Sex
Determining Regions of the Y chromosome (SRY gene).
- In the presence of a functional SRY gene, bipotential gonad
medulla become testes
- In the absence of a functional SRY gene, and under direction of X
chromosome genes, gonad cortex develops into ovaries
Male Embryonic Development:
1. The SRY Gene produces testis determining factor (TDF)
2. TDF binds DNA, activating genes directing development of
gonadal medulla into the testes
3. Once the testes develop they begin to secrete hormones to guide
male internal and external genitalia development:
a. Sertoli Cells secrete anti-Mullerian hormone
b. Interstitial (Leydig cells) secrete androgens (testosterone and DHT)
4. Antimullerian hormone causes embryonic Mullerian Ducts to regress
5. Testosterone converts Wolffian Ducts into male accessory structure: epididymis, vas deferens,
and seminal vesicle
6. DHT directs external genitalia development
a. Genital tuburcles become glans penis
b. Urethral folds & groove become penis shaft
c. Labioscrotal swellings form shaft and scrotum
1. The Gonads: The organs that produced gametes (cells that unite to form new individuals)
a. Male gonads = the testes which produce the sperm
b. Female gonads = the ovaries which produce the eggs
c. Undifferentiated cells that become gamete = germ cells
2. The Internal Genitalia: Accessory glands and ducts that connect the gonads with the outside
environment
3. The External Genitalia: External reproductive structures
All cells other than the gametes, contain 46 chromosomes. Cells with 46 chromosomes are labeled as
diploid cells.
- 22 matching pairs of autosomes
- 1 pair of sex chromosomes
- Gametes contain 23 chromosomes. They are labeled as haploid cells.
Sex Determination
Sex is determined based on the sex chromosome provided by the father’s gamete.
- The mother has only XX chromosomes, and can only provide X chromosomes to offspring.
- Father has both X and Y chromosomes, only one is passed onto offspring.
- Males receive Y from father, Females receive X from father.
Abnormalities in sex chromosome inheritance can occur as follows:
- XXY → will become male, because of possession of Y chromosome
- Y → will die, because X is essential to the development of any sex.
- X → Turner’s Syndrome → will survive with abnormal female reproductive function
Once the ovaries develop in a female fetus, one X chromosome is inactivated in each cell of her body,
condensed into a Barr Body.
,Sexual Differentiation (see next page)
Before differentiation the embryonic tissues are bipotential, they cannot be identified as morphologically
male or female.
- The bipotential gonad has: Outer gonadal cortex and inner gonadal medulla:
- In females, cortex becomes ovaries, medulla regresses
- In males, cortex regresses, medulla becomes testes
- The bipotential internal genitalia has: Wolffian ducts and Mullerian Ducts
- Absence of presence of one depends on male/female signals
- The bipotential internal genitalia has:
- Genital tuburcles: becomes clitoris, becomes glans penis
- Urethral folds & groove: becomes labia minora, vaginal opening, becomes penis shaft
- Labioscrotal swellings: form labia majora, form shaft and scrotum
, Sex determination depends on the presence or absence of Sex
Determining Regions of the Y chromosome (SRY gene).
- In the presence of a functional SRY gene, bipotential gonad
medulla become testes
- In the absence of a functional SRY gene, and under direction of X
chromosome genes, gonad cortex develops into ovaries
Male Embryonic Development:
1. The SRY Gene produces testis determining factor (TDF)
2. TDF binds DNA, activating genes directing development of
gonadal medulla into the testes
3. Once the testes develop they begin to secrete hormones to guide
male internal and external genitalia development:
a. Sertoli Cells secrete anti-Mullerian hormone
b. Interstitial (Leydig cells) secrete androgens (testosterone and DHT)
4. Antimullerian hormone causes embryonic Mullerian Ducts to regress
5. Testosterone converts Wolffian Ducts into male accessory structure: epididymis, vas deferens,
and seminal vesicle
6. DHT directs external genitalia development
a. Genital tuburcles become glans penis
b. Urethral folds & groove become penis shaft
c. Labioscrotal swellings form shaft and scrotum
