Module 2 Section 1 (Intro to Reproductive Physiology)

Question 1

Describe the primary purposes of both the male and female reproductive systems (2 vs. 6).

Answer 1

Male:

1) Production of sperm
- Sperm = gamete cells of males produced in the testes
- Testes inside of abdomonal cavity in scrotum

2) Delivery of sperm to the female
- Sperm -> testes
- Sperm is suspended in secretions from the accessory sex glands
• the seminal vesicles
• the prostate gland
• the bulbourethral glands
- Secretions = important for sperm viability and for the delivery of the sperm to the female reproductive
system via the penis.

     Female: 

1) The production of ova
- Ova or eggs are produced in the ovaries and individual ova undergo cyclical maturation.

2) Reception of sperm
- The reception of sperm occurs in the vagina, which is a muscular tube that connects the uterus, via the cervical canal, to the external environment.

3) Transport of ovum and sperm to a common site for fertilization:
- The ova leave the ovaries and move into the Fallopian tubes, where they can be fertilized by sperm that have traveled from the vagina, through the cervical canal, into the uterus, and ultimately into the Fallopian tubes.

4) Maintenance of the developing fetus
- This occurs within the uterus for about 9 months during pregnancy.

5) Birth of the baby
- This is referred to as parturition.

6) Nourishing the baby by milk production
- Lactation.

Question 2

Explain sex differentiation (refers to the embryonic development of both the external genitalia and the
reproductive tract) in terms of genetic, gonadal, and phenotypic sex

Answer 2

Genetic
- Genetic sex is determined by a combo of sex chromosomes at conception.
- diploid parent cells divide -> haploid gamete cells (sperm and ova) via meiosis = gametes
- Half of sperm carry a single X chromosome, while other half = Y; Meanwhile females just carry X.
- 2 haploid cells combine -> fertilized ovum w/ 2 sets of 23 chromosomes.
- Sperm carrying X fertilizes ovum then genetic sex of embryo = XX (female); if Y, then male.
- Genetic sex determined gonadal sex b/c of presence or absence of Y.
- Phenotypic
sex thus depends on the genetically determined gonadal sex.

Gonadal
- Determined by presence of absence of Y.
- For first 6 weeks of gestation, male and female embryos = identical
- At 7 weeks, the sex-determining region of Y-chromosome (SRY) stimulates -> H-Y antigen production (acts on the gonads to differentiate into testes)
• In absense of antigen, the gonads differentiate into ovaries.

Phenotypic

• Anatomical differences that’s dependent upon the gonadal sex.
• As with the undifferentiated gonads, embryos of both sexes have the potential to develop either male or female external genitalia and reproductive tracts.
• In the presence of androgens secreted by the developing testes = male-type reproductive systems are developed. The absence of androgens = a female-type reproductive system.

Question 3

Explain how the reproductive tracts of males and females develop during sexual differentiation.

Answer 3

Wolffian Ducts:
- The placenta secretes human chorionic gonadotropin (hCG).
- If testes are present, hCG stimulates them to produce and secrete testosterone.
- This testosterone -> stimulates the Wolffian ducts -> develop into the male reproductive system.
- Testosterone is also converted -> dihydrotestosterone (which is responsible for the development of
male external genitalia).
- The testes secrete Müllerian-inhibiting factor = causes the degradation
of the Müllerian ducts.

Müllerian Ducts:

• In the absence of testosterone = Wolffian ducts degrade and the Müllerian ducts develop into the female reproductive tract and external genitalia.
• Sexual differentiation is dependent upon the presence or absence of testosterone.
• However, the developing embryo is exposed to high levels of female sex hormones throughout gestation.
• W/o the addition of testosterone, all fetuses would be feminized.

Question 4

What does successful sexual reproduction look like?

Answer 4

Depends on the union of male and female gametes in order to form a
new individual with a full set of chromosomes.

Question 5

Define gametes

Answer 5

Reproductive, or germ cells, each containing a half set of chromosomes.

Question 6

The male and female reproductive systems are dramatically different.
However, they have the common purpose. What is it?

Answer 6

They have the common purpose of producing gametes and are designed for allowing the union of both male and female gametes.

Question 7

Define gonads.

Answer 7

The primary reproductive organs are called gonads. The gonads are where the gametes, as well as the primary sex hormones, are produced.

• In males = testes
• In females = ovaries

Question 8

What does the reproductive tract do?

Answer 8

It allows the transport of gametes after they are produced, as well
as many accessory sex glands that release supportive secretions into the reproductive tract.

Question 9

What is external genitalia?

Answer 9

The externally visible part of the reproductive systems of both males and females

Question 10

Review the name and location of each structure of the male reproductive system

Answer 10

Check SC

Question 11

Review the name and location of each structure of the female reproductive system

Answer 11

Check SC

Question 12

Define diploid, haploid, embryo and gestation.

Answer 12

Diploid: Containing 2 complete sets of chromosomes, with one chromosome from each pair being derived from the sperm cell, and one from the ova.
- Diploid = 46 chromosomes, 23 pairs

Haploid: Having a single set of unpaired chromosomes.
- Haploid = 23 individual chromosomes

Embryo: A vertebrate at any stage of development prior to birth or hatching.

Gestation: The carrying of an embryo or fetus inside the female.

Question 13

True or false: specialized germ cells undergo meiosis to produce 4 daughter cells with only a single set of genetic
information, or 23 unpaired chromosomes.

Answer 13

True

These haploid daughter cells are the ova and sperm.

Question 14

What occurs during Meiosis I?

Answer 14

Replicated chromosomes (which contain an identical pair of chromatids) sort themselves into homologous pairs before separating so that each daughter cell receives a single set of chromosomes (1 homologue from each pair).

Therefore, meiosis I = 2 daughter cells with a single set of chromosomes, each containing a
pair of sister chromatids.

Question 15

What occurs during Meiosis II?

Answer 15

The sister chromatids within the chromosomes of each of the
daughter cells separate and are distributed to 2 cells.

The result of meiosis II = 4 daughter cells, each containing a single set of chromosomes, containing
one chromatid each.

Question 16

What is the placenta and what does it do?

Answer 16

An organ that connects the developing fetus to the uterine wall to allow nutrient uptake, thermo-regulation, waste elimination, and gas exchange via the mother’s blood supply.

Question 17

Using what you have learned about sexual differentiation, describe what would occur in an individual affected by the given error in sexual differentiation.

1) A genetic male whose testes fail to develop or target tissues lack testosterone receptors
2) A deficiency in the enzyme that converts testosterone to DHT
3) A genetic female with excessive adrenal secretion of DHEA during fetal development

Answer 17

1) A genetic male whose testes fail to develop or target tissues lack testosterone receptors
- An apparent phenotypic female that is sterile due to lack of ovaries.

2) A deficiency in the enzyme that converts testosterone to DHT
- An individual having a male reproductive tract with female external genitalia.

3) A genetic female with excessive adrenal secretion of DHEA during fetal development
- Reproductive tract and external genitalia are masculinized, the extent of which depends on how much dehydroepiandrosterone is secreted.