5.2 Mammalian Reproduction

Question 1

Outline the structure of the testis.

Answer 1

This structure is made from thousands of seminiferous tubules each of which is about 20μm diameter. Between these tubes are interstitial cells which produce testosterone at puberty.

Question 2

What is the role of testosterone? (In relation to reproduction)

Answer 2

This hormone begins sperm cell production

Question 3

What is the process by which sperm cells are made?

Answer 3

Spermatogenesis.

Question 4

Where does spermatogenesis occur?

Answer 4

In the testis

Question 5

What is the name for the vessel to which all the seminiferous tubules are connected?

Answer 5

The epididymis.

Question 6

label This diagram of a male mammalian reproductive system.

Answer 6

Question 7

Label this Diagram of a sperm cell.

Answer 7

sperm cells are highly specialised haploid cells which live for only a few hours, which is why they have very little cytoplasm and no food reserve.

Question 8

Label this diagram of a sectioned Testis.

Answer 8

Question 9

What is the function of the cowper’s and sempinal glands?

Answer 9

They secrete the fluids, protien and glucose which keep sperm cells alive for long enough to enter the female reproductive tract.

Question 10

How thick is the wall of the germinal epithelium of the seminiferous tubules and what nkind of cells make up this structure?

Answer 10

One cell thick.. These cells are diploid, somatic(body) cells.

Question 11

Complete this diagram giving an outline of spermatogenesis.

Answer 11

Question 12

By what process do germinal epithelial cells become spermatagonia?

Answer 12

Mitosis

Question 13

What Changes occur that differentiate Spermatagonia from primary spermocytes?

Answer 13

Spermatagonia undergo a short growth phase and move inwards to become primary spermocytes.

Question 14

By what process are secondary spermatocytes produced from primary spermatocytes?

Answer 14

Meiosis 1

Question 15

In terms of n/2n how many chromosomes are contained in a secondary spermatocyte?

Answer 15

2n (Primary spermatocyte genetic content doubles before meiosis 1 resulting in the foremation of two diploid secondary spermatocytes at the end of meiosis 1)

Question 16

By what process are spermatids produced from secondary spermatocytes?

Answer 16

Meiosis 2

Question 17

In terms of n/2n how many chromosomes are present in a spermatid?

Answer 17

n

Question 18

What happens to the spermatids?

Answer 18

They migrate to the centre of the lumen where they undergo specialisation to become spermatozoa (sperm cells)

Question 19

What happens to a spermatozoon once it has been produced?

Answer 19

It becomes attached to large secretory sertoli cells which provide nutrition.

Question 20

Complete this diagram outlining Oogenesis.

Answer 20

Question 21

Label this diagram of the female reproductive system.

Answer 21

Question 22

Label this diagram outlining the process of ovulation.

Answer 22

Question 23

What Triggers Oogenesis?

Answer 23

The stroma secretes oestrogen which is the chemical signal for the development of the primary follicle.

Question 24

How does a primary follicle develop?

Answer 24

A cell from The germinal epithelium undergoes mitosis to produce cells called oogonia (2n). These cells then go through a growth phase to become primary oocytes. Each primary oocyte now becomes surrounded by thousands of cells from the stroma to create a primary follicle.

Question 25

Why is cytokinesis during Oogenesis unequal?

Answer 25

So that the ovum produced has the maximum possible amount of cytoplasm - and therefore nutrients - which is required for a developing zygote.

Question 26

What happens whilst the primary oocyte withing the follicle is undergoing meiosis?

Answer 26

The foillicle is growing ever larger and is migrating through the stroma, eventually becoming a 12mm structure called the graffian follicle.

Question 27

Outline the structure of the graffian follicle.

Answer 27

The graffian follicle has a complex structure but is mainly filled with fluid. In its centre is the secondary oocyte which is surrounded by a fluid - the zona pellucida - and a tissue called the corona radiata (vitelline membrane).

Question 28

What causes ovulation?

Answer 28

Ovulation occurs when the graafian follicle ruptures and the secondary oocyte is released, surrounded by the corona radiata.

Question 29

What does the empty graffian follicle become after ovulation?

Answer 29

It becomes a structure called the corpus luteum which secretes progesterone which maintains the endometrium.

Question 30

After ovulation, what happens if fertilization occurs?

Answer 30

The secondary oocyte undergoes meiosis 2, producing an ovum and a secon polar body. In this case the corpus luteum and endometium do not break down and progesterone levels remain high.

Question 31

Label this diagram which outlines the procfess of fertilization

Answer 31

Question 32

Whaere does the sperm cell usually make contact with the ovum?

Answer 32

A sperm cell usually makes contact with the vitelline membrane within the first third of the fallopian tube resulting in the acrosome reaction.

Question 33

What is the function of the acrosome reaction?

Answer 33

Here, the acrosome breaks open, releasing hydrolytic enzymes which soften vitelline membrane, allowing the sperm cell head to bind with the membrane of the secondary oocyte.

Question 34

What happens during fertilization after the sperm has fused with the ovum?

Answer 34

The male nucleus now enters the cytoplasm of the egg cell. THe two nuclei fuse together producing the first diploid nucleus and a cell called the zygote.

Question 35

How is a second fertilisation prevented?

Answer 35

The cortical granules migrate through the plasma membrane of the zygote cell - hardening the zona pellucida - and forming a tough outer layer around the entire membrane.

Question 36

WHat happens after fertilisation is complete?

Answer 36

Mitosis now occurs, rapidly forming a solid ball of cells called a Morula, which continues to develop until it eventually becomes a much larger hollow structure called the blastocyst.

Question 37

What happens during implantation?

Answer 37

After about five days the blastocyst enters the uterus, secretes hydrolytic enzymes and sinks into a nutrient rich fluid.

Question 38

Label this diagram to show the structure of a blastocyst.

Answer 38

Question 39

Name the hormone which is secreted by the placenta which is used by pregnancy tests.

Answer 39

Choriogonadotrophin, the human form of which is HGC.

Question 40

How do pregnancy tests detect HGC?

Answer 40

They contain an antibody to HGC which is bonded to a blue bead. If HGC is present in the urine, the antibody binds to HGC causing the beads to align and a blue line to appear.