Reproductive system

Question 1

How are gametes produced?

Answer 1

Via the process of meiosis

Question 2

List some of the advantages of sexual reproduction compared to asexual reproduction

Answer 2

Creates variations among individuals, thus increasing the chance of survival, which leads to species preservation
Unfavourable genes will be eventually removed

Question 3

Disadvantages of sexual reproduction compared to asexual reproduction

Answer 3

Need male and female
Need effort to choose mates
May prevent favourable genes from being passed on to offspring
Produces fewer offspring than asexual reproduction

Question 4

Define the term ‘gonad’

Answer 4

The organ where gametes are produced. They also produce hormones that control secondary sexual characteristics

Question 5

Name the gonad in males

Answer 5

Testis

Question 6

Name the gonad in females

Answer 6

Ovary

Question 7

Define the term ‘germ cells’

Answer 7

Any cell in the series of the germ line that eventually become gametes
Often indicate the cells before meiosis during spermatogenesis and oogenesis

Question 8

What are the germ cells in females?

Answer 8

Oogonia

Question 9

What are the germ cells in males?

Answer 9

Spermatogonia

Question 10

What are primordial germ cells?

Answer 10

The origin of germ cells
Arises and stay in the posterior yolk sac
At 4-6 weeks in human, migrate into the gonad and then reside as germ cells

Question 11

When do the semibiferous tubules mature?

Answer 11

They mature at puberty because of testosterone

Question 12

What type of cell is the resident stem cell population of the seminiferous tubule of the testis?

Answer 12

Spermatogonium

Question 13

What are testes made of?

Answer 13

Seminiferous tubules, which is where meiosis occurs in males

Question 14

Define the term ‘spermiogenesis’

Answer 14

The differentiation step of spermatids to become a highly specialised spermatozoa

Question 15

Give the main stages of spermiogenesis (5)

Answer 15

• Nucleus condense
• Formation of the acrosome
• Formation of the flagellum
• Mitochondria gathered at the midpiece
• Removal of excess cytoplasm

Question 16

What is the acrosome?

Answer 16

A secretory vesicle containing enzymes required for penetrating the oocyte

Question 17

What is the flagellum?

Answer 17

a tail-like structure homologous to cilia

Question 18

Why do sperm need a lot of mitochondria?

Answer 18

For the moving flagellum

Question 19

When does spermiogenesis take place?

Answer 19

Spermiogenesis takes place when spermatids are still surrounded by Sertoli cells.

Question 20

Describe sertoli cells

Answer 20

Span from the basement membrane to the lumen, thus surrounding differentiating spermatogonia
Produce enzymes and growth factors required for spermatogenesis
Also function as a phagocyte to clean-up residual cytoplasm of sperm

Question 21

What are Leydig cells?

Answer 21

Leydig cells are interstitial cells that reside outside of seminiferous tubules. They secrete testosterone in response to LH

Question 22

What is spermiation?

Answer 22

The process of sperm being released in to the lumen from the sertoli cells

Question 23

What’s the epididymis?

Answer 23

A highly convoluted duct behind the testis, along which sperm passes to the vas deferens.

Question 24

Define the term ‘infertility’

Answer 24

An inability to conceive within 12 months

Question 25

List the causes of male infertility

Answer 25

* Primary hypogonadism (Kleinfelter, cryptorchidism (absence of testes), chemotherapy, radiation, torsion etc) (30-40%) * Secondary hypogonadism (hypothalamic-pituitary disease) (2%) * Disordered sperm transport (10-20%) * Unknown (40-50%)

Question 26

Define 'oogenesis'

Answer 26

The production or development of an ovum.

Question 27

What are the germ cells in females called when they enter the first phase of meiosis?

Answer 27

Primary oocytes

Question 28

One follicle=

Answer 28

One oocyte + surrounding follicular cells

Question 29

Why are polar bodies formed in female meiosis?

Answer 29

In the meiotic cell division, most of the cytoplasm is taken by one, so as not to waste cytoplasm

Question 30

What is the germ cell called when ovulation takes place?

Answer 30

A secondary oocyte

Question 31

Define the term 'primordial follicle'

Answer 31

A primary oocyte with an enlarged cytoplasm, with a flat one-cell layer of follicular (granulosa) cells. The dormant status

Question 32

What are primary follicles?

Answer 32

Follicles chosen to re-commence growth. Follicular cells become cuboid and proliferate into multiple layers

Question 33

Define the term 'zona pellucida'

Answer 33

A layer of glycoprotein, translucent.

Question 34

What are secondary follicles?

Answer 34

A follicle with antrum (a cavity) with fluid from granulosa cells

Question 35

What are preovulatory follicles?

Answer 35

Among several secondary follicles, one is chosen to mature for ovulation

Question 36

When is the first day of the menstrual cycle?

Answer 36

The first day of menstruation.

Question 37

What causes the endometrial lining to thicken?

Answer 37

After day 5, the follicle and thecal cells proliferate and secrete oestrogens. Oestrogens in turn cause the endometrial lining of the uterus to proliferate.

Question 38

What induces ovulation?

Answer 38

On about day 13 or 14, levels of FSH and LH suddenly rise very sharply, which induces ovulation and progresses meiosis

Question 39

What is ovulation?

Answer 39

The expulsion of the secondary oocyte from the follicle. It takes place about 38 hours after the LH surge

Question 40

What happens after ovulation?

Answer 40

After ovulation, the remaining follicle becomes a corpus luteum and secretes oestrogen and progesterone. This leads to the endometrium secretory phase, preparing for implantation

Question 41

What happens if implantation of a fertilised egg doesn't take place?

Answer 41

If implantation doesn't occurs, the corpus luteum degenerates after 14 days and becomes a scar-like structure called corpus albicans)

Question 42

When sperm reach the oocyte, what do they have to do in order to fertilise it?

Answer 42

When they encounter the oocyte, the sperm has to; a) migrate through the layer of follicular cells (corona radiata) b) penetrate the zona pellucia using enzyme in acrosome c) fuse the plasma membrane to that of oocyte

Question 43

When does the second meiotic division of oocytes happen?

Answer 43

The second division of meiosis of oocyte completes when the sperm enters

Question 44

Describe implantation of the fertilised eg

Answer 44

1. Blastocyst attaches to the endometrium at the embryonic pole 2. Some trophoblast cells invade the endometrium, beginning to form a part of the placenta 3. The inner cell mass becomes a flat sheet consisting of epiblasts and hypoblasts 4. The amniotic cavity appears on the epiblast side 5. human chorionic gonadotrophin (hCG), produced by the syncytiotrophoblast, enter the maternal blood

Question 45

What does human chorionic gonadotrophin do?

Answer 45

hCG maintains the hormonal activity of the corpus luteum in the ovary. The corpus luteum secretes estrogen and progesterone to maintain pregnancy.