Chapter 7 - Sexual Reproduction in Humans.

Question 1

What does the male reproductive system consist of?

Answer 1

• A pair of testes contained in the scrotum.
• The penis.
• Ducts connecting the testes with the penis (vas deferens and the urethra).
• Accessory glands (seminal vesicles, prostate gland etc.).

Question 2

What happens in the seminiferous tubules?

Answer 2

The cells lining them undergo sperm formation and throughout the process, move towards the the lumen, running through the middle of the tube.

Question 3

What do the seminal vesicles do?

Answer 3

They secrete mucus which helps sperm mobility (contains fructose respired by the sperm).

Question 4

What does the prostate gland do?

Answer 4

It produces an alkaline secretion that neutralises any urine left in urethra and aids in sperm mobility.

Question 5

What do sertoli cells do?

Answer 5

They secrete a fluid which nourishes spermatids and protects them from the male’s immune system.

Question 6

What are the stages in spermatogenesis?

Answer 6

• Germinal Epithelial Cells (Mitosis).
• Spermatogonia (Mitosis).
• Primary spermatocytes (Meiosis I).
• Secondary spermatocytes (Meiosis II).
• Spermatids (Differentiation).
• Spermatozoan.

Question 7

What do interstitial cells (AKA. Leydig cells) do?

Answer 7

They secrete testosterone which has a role in sperm formation and maturation.

Question 8

What are the layers of the uterus wall?

Answer 8

• Myometrium muscle layer.
• Endometrium, it’s a mucous membrane which is well supplied with blood. It is the layer which builds and is shed in a monthly cycle, unless an oocyte is fertilised.

Question 9

What are the stages of oogenesis?

Answer 9

• Germinal epithelial cells (Mitosis).
• Oogonia (Mitosis).
• Primary Oocytes (Meiosis I).
• Secondary Oocyte +Polar body (Meiosis II).
• Ovum + 2nd polar body (Only happens after fertilisation).

Question 10

Where does Oogenesis have breaks?

Answer 10

-Primary Oocytes start to divide by mitosis but stop at Prophase I. Then, at puberty FSH stimulates one each month to complete Meiosis I and get to Metaphase II where it stops unless its fertilised.

Question 11

How does a Graafian Follicle develop?

Answer 11

Some germinal epithelial cells also divide by mitosis to form follicle cells which surround the primary oocytes to form primary follicles. FSH will then cause one each month to develop into a secondary follicle and then forms a Graafian follicle.

Question 12

What is the structure of a Graafian Follicle?

Answer 12

• Secondary Oocyte.
• Zona Pellucida.
• Corona Radiata.
• Antrum.
• Theca.

Question 13

What is the the temporary gland formed when the graafian follicle ruptures and what hormone does it produce if fertilised?

Answer 13

The corpus luteum which produces progesterone that maintains the endometrium.

Question 14

What happens to the corpus luteum is the oocyte isn’t fertilised?

Answer 14

It regresses.

Question 15

What in the oocytes prevents the entry of more than one sperm?

Answer 15

Cortical granules, they’re secretory organelles.

Question 16

What is a major difference between spermatogenesis and oogenesis?

Answer 16

A primary spermatocyte will produce four gametes but a primary oocytes produces only one (Due to the polar body created).

Question 17

What is the process of capacitation in a sperm cells?

Answer 17

It’s the removal of cholesterol and glycoproteins from the cell membrane over the acrosome in the sperm head. Over time, it becomes more fluid and permeable to Ca+ ions.

Question 18

What is the acrosome reaction?

Answer 18

Acrosome enzymes (proteases) digest the corona radiata and the zona pellucida, allowing the sperm and oocytes cell membranes to fuse.

Question 19

What is the reaction that prevents polyspermy and how does it occur?

Answer 19

The cortical reaction, when the sperm attaches to the secondary oocyte, the SER releases Calcium ions into the cytoplasm. They make the cortical granules fuse with the membrane and release their contents causing the zona pellucida to expand and harden.

Question 20

What is the sequence called as the embryo moves down the oviduct, dividing many times?

Answer 20

Cleavage.

Question 21

What is the process of implantation?

Answer 21

The sinking of the blastocyst into the endometrium.

Question 22

What is a trophoblast and what are the villi they form used for?

Answer 22

The trophoblast is the name given to the cells forming the outer layer of the blastocyst. The trophoblastic villi penetrate the endometrium and they increase the surface area for the absorption of nutrients from the endometrium.

Question 23

What does the trophoblast develop into?

Answer 23

The chorion, these create larger villi and acquire blood capillaries which are connected to the umbilical artery and vein.

Question 24

What is the umbilical cord?

Answer 24

It develops from the chorion and transfers the foetal blood to the placenta in 2 umbilical arteries and returns it in a vein.

Question 25

What are the functions of the placenta?

Answer 25

- Endocrine organ, producing hormones to support the pregnancy. - Exchange between the blood (Inter-villous spaces surround the chorionic villi). - A physical barrier, protecting the fragile foetal capillaries. - Provides passive immunity. - Protection against the mother's immune system.

Question 26

What are the significant hormones in the menstrual cycle?

Answer 26

- Follicle stimulating hormone (FSH). - Luteinising hormone (LH). - Oestrogen. - Progesterone.

Question 27

During pregnancy, what do each of the hormones do?

Answer 27

- HCG made by the embryo maintains the corpus luteum maintaining pregnancy. - Progesterone, prevents uterine contractions. - Oestrogen, stimulates the growth of the uterus and mammary glands.

Question 28

In the menstrual cycle, what is day 0?

Answer 28

The first day of a period.

Question 29

What is a period?

Answer 29

The shedding of the endometrium wall if a blastocyst has not implanted.

Question 30

What hormones are secreted in the period?

Answer 30

GnRH is secreted by the hypothalamus thich stimulates the anterior pituitary gland to secrete FSH which stimulates the development of a primary follicle. This has a positive feedback mechanism as it stimulates the theca cells to produce oestrogen.

Question 31

What does increasing oestrogen levels cause to happen?

Answer 31

- Triggers the rebuilding of the endometrium, that was shed during menstruation. - Inhibits FSH secretion by negative feedback, which in turn brings its own concentration down. - Stimulates LH production by positive feedback.

Question 32

What does the surge in LH cause to happen?

Answer 32

It causes ovulation (release of the secondary oocyte), and has a positive feedback on FSH and levels pick back up again.

Question 33

What does the ruptured graafian follicle develop into and what hormones does it secrete?

Answer 33

It develops into the corpus luteum which secretes oestrogen and progesterone.

Question 34

What do the increased levels of oestrogen and progesterone do?

Answer 34

They build and maintain the endometrium lining so that is a secondary oocyte is fertilised,, there with be suitable tissue in which the embryo can implant. These high levels also inhibit FSH and LH production.

Question 35

What does the falling levels of FSH and LH do to the corpus luteum?

Answer 35

It causes it to degenerate so progesterone and oestrogen production declines.

Question 36

What does the drop in progesterone cause to happen?

Answer 36

It causes mensuration so the endometrium is shed and the cycle starts over.

Question 37

Even if the secondary oocyte is fertilised, why may a pregnancy fail?

Answer 37

- It may fail to divide. - It may implant in the wrong place. - It may fail to implant.

Question 38

What are the main roles of the main hormones during the menstrual cycle?

Answer 38

- FSH, follicle development. - LH, ovulation. - Oestrogen, rebuild endometrium. - Progesterone, maintain endometrium.

Question 39

What is the function of the amniotic fluid?

Answer 39

- Maintains the foetus's temperature. - Provides lubrication. - Contributes to lung development. - Allows movement so muscles and bones function before birth. - Acts as a shock absorber.

Question 40

What does hCG do and when is it secreted?

Answer 40

It is secreted by the embryo and it maintains the corpus luteum.

Question 41

Before birth, what does the decrease of progesterone and oestrogen cause?

Answer 41

They are no longer inhibiting the production of oxytocin and prolactin. Oxytocin causes contractions of the myometrium in the uterus wall. The contractions are mild but they stimulate the secretion of more oxytosin so concentration increases