module 14: reproductive system first half

Question 1

what is the function of both male and female reproductive systems?

Answer 1

to pass on genes of the individuals and maintain the species

Question 2

how many chromosomes are in each body cell? what are sex chromosomes made of ?

Answer 2

each cell in the body contains 23 chromosomes, including a pair of sex chromosomes
- sex chromosomes are made up of a large X chromosome and a small Y chromosome

Question 3

what chromosomes do eggs and sperm carry? how and when does this determine sex of the baby?

Answer 3

all eggs contain an X chromosome and the sperm can carry either an X or Y
- if a sperm carrying a X chromosome penetrates the egg, then female will develop (XX)
- if a sperm carrying a Y chromosome penetrates the egg, a male will develop (XY)

sex of the future baby is determined at point of fertilization

Question 4

what happens at 6 weeks of development? when/what do male and female gonads develop?

Answer 4

during the first 6 weeks of development, male and female embryos contain common gonads

in developing male embryos (6-7 weeks): presence of Y chromosome causes the indifferent gonads to develop testes

in developing female embryos (9 weeks): XX chromosomes are activated and ovaries develop

Question 5

what are the 2 sets of primitive reproductive tracts, what occurs?

Answer 5

1. Wolffian duct (also called mesonephric)
2. Mullerian duct (also called paramesonephric)

where mature reproductive tracts and external genitalia form after development of testes/ovaries

Question 6

male fetal development of reproductive system - what happens at 7 weeks and 9 weeks?

Answer 6

• at 7 weeks, testicular cells begin to produce Mullerian inhibiting hormone (MIH), causing the Müllerian duct to regress
• at 9 weeks, testicular cells begin to produce testosterone, this stimulates the Wolffian duct to develop into the:
• epididymis
• vas deferens
• seminal vesicles
• urethra

presence of testosterone also causes the development of the male external genitalia

Question 7

female fetal development of reproductive system - describe what happens in the beginning of development

Answer 7

development of the female reproductive tract requires NO hormonal control
- since there is no Mullerian Inhibiting Hormone (MIH) the Müllerian duct develops into the:
- fallopian tubes
- cervix
- uterus
- and part of the vagina

since no testosterone is produced, Wolffian duct regresses and female external genitalia develop

Question 8

what are the functions of the male reproductive system?

Answer 8

• produce the sex steroid testosterone (has many bodily effects, especially at puberty)
• to produce sperm (spermatogenesis) and deliver it to the female vagina

Question 9

what are the functions of the female reproductive system?

Answer 9

• produce the sex steroid estrogen, and the hormone progesterone
• produce eggs and receive the sperm
• provide optimal conditions for the development of the fetus

Question 10

what structures make up the male external genitalia, describe what the penis is made up of, and what the scrotum contains

Answer 10

the external genitalia consists of the penis and the scrotum

the penis is made up of the:
- urethra
- glans penis
- erectile tissue corpus spongiosum and corpus cavernosum

the scrotum contains the testes where the sperm and testosterone is produced

Question 11

describe the sperms path during ejaculation

Answer 11

1. sperm travels through the ductus deferens (vas deferens) and mixes with fluid from the seminal vesicles
2. then pasess through the prostate and receives more fluid from the bulbourethral (Cowper’s) gland
3. it then enters the urethra and passes out through the penis

Question 12

explain the pathway of sperm in the testes

Answer 12

testes consist of many coiled seminiferous tubules
- after formation in the seminiferous tubules, the sperm moves into the epididymis, another coiled tube
- epididymis drains into the ductus deferens (vas deferens)

Question 13

what is contained in the seminiferous tubules

Answer 13

• they contain Sertoli cells and developing sperm
• in the interstitial space between the seminiferous tubules are Leydig cells (interstitial cells)

Question 14

what are the functions of seminiferous tubules, Leydig cells, and Sertoli cells

Answer 14

Seminiferous tubules - site of spermatogenesis

Leydig cell - produce testosterone

Sertoli cells - regulate spermatogenesis and maintain developing sperm cells (spermatogonia), also…
- produce the hormone inhibin which secretes a fluid that pushes immature sperm to the epididymis and form the blood-testis barrier (BTB)
- BTB isolates the developing sperm cells from the blood so that immune cells do not attack them

Question 15

Explain the functions of the epididymis, vas deferens, seminal vesicles, the bulbourethral (Cowper’s) gland, and urethra

Answer 15

Epididymis is the final maturation area and storage site for sperm

Vas deferens carries the sperm from the epididymis to the ejaculatory duct
- ejaculatory duct drains into the urethra

Seminal vesicles contribute a large amount of fluid to the semen during ejaculation
- this fluid is rich in fructose and enzymes, helps to maintain/nourish sperm

The Bulbourethral Gland (Cowper’s Gland) secretes fluid to neutralize pH and lubricate the urethra and vagina to create an optimal environment for sperm

Urethra transports sperm during ejaculation and drains the bladder during urination

Question 16

when does spermatogenesis begin in a male?

Answer 16

spermatogenesis (sperm production) begins when male begins puberty and starts producing testosterone

Question 17

describe the process of spermatogenesis, how long does it take?

Answer 17

1. Spermatogonia contain 46 chromosomes (23 pairs) and are located at the outer edge of the seminiferous tubules, they divide by mitosis into 2 cells
2. One cell continues as spermatogonia and the other develops into a primary spermatocyte (each cell contains 46 chromosomes)
3. Primary spermatocyte divides by meiosis into 2 secondary spermatocytes (during 1st meiotic division) then into 4 spermatids (during 2nd meiotic division)
4. Dividing cells, which are surrounded and nourished by Sertoli cells, work their way to the centre of the tubule
5. Spermatids (23 chromosomes) develop into sperm cells, where they are released by Sertoli cells into the lumen of the seminiferous tubules

whole process takes 64 days to complete

Question 18

Describe the components of a sperm cell, how long does maturation of a sperm cell take and when

Answer 18

although not fully mature and able to swim, the sperm cell contains…
- a head with an acrosome and nucleus
- a midpiece with mitochondria
- a long tail or flagellum that will propel the sperm once it fully matures

complete maturation of the sperm takes another 12 days, occurs as sperm are moved to epididymis by the fluid that is secreted by the Sertoli cells

Question 19

How are testicular functions controlled?

Answer 19

functions are controlled by follicle stimulating hormone (FSH) and luteinizing hormone (LH)
- released by the anterior pituitary in response to gonadotropin releasing hormone (GnRH) from the hypothalamus

Question 20

What does FSH control in the testes, feedback?

Answer 20

FSH acts on the Sertoli cells to promote spermatogenesis and producing the hormone inhibin
- inhibin feeds back to the hypothalamus to decrease the release of LH and FSH

Question 21

What does LH control in the testes, feedback?

Answer 21

LH stimulates the Leydig cells to produce testosterone
- testosterone is essential for spermatogenesis and will feed back to the hypothalamus and anterior pituitary to decrease production and secretion of LH and FSH

Question 22

what is testosterone, brief overview of how it is produced

Answer 22

a steroid hormone produced by the Leydig cells in the testes
- production involves series of reactions, begins with cholesterol and the formation of several intermediates, ending in testosterone
- progesterone (female hormone) is present as one of the intermediates leading to testosterone production

Question 23

describe testosterone levels varying through age (to adulthood)

Answer 23

1. rise during fetal development
2. after birth there is another small increase
3. levels of testosterone remain low until puberty
4. puberty marks the transition from childhood (non reproductive state) to adulthood (reproductive state)
5. at puberty (9-14) levels of gonadotropin releasing hormone (GnRH) begin to increase
   - leads to increase in LH and FSH, causing testosterone levels to rise
6. testosterone causes the final maturation of the male reproductive system to the point where mature sperm is produced

sexual maturity and peak testosterone levels are reached around 16-18

Question 24

describe the functions of testosterone

Answer 24

development of the male reproductive tract and external genitalia in the embryo
- growth/development of all male reproductive organs at puberty
- development of male secondary sex characteristics at puberty (muscle growth, deep voice, etc.)
– sex drive at puberty
- spermatogenesis
- bone growth
- increased aggressiveness

Question 25

what happens in testosterone levels from age 40+

Answer 25

beginning at 40 there is a slow decrease in testosterone levels

at 50, sperm production begins to decrease
- this period of decreased testosterone is called andropause
- may occur because Leydig cells no longer respond to LH
- andropause accompanied by decreased sexual desire, erectile ability, fatigue, depression, etc.