PBL 2- Male reproductive system and ART

Question 1

How long does it take for spermatogenesis to occur

Answer 1

Takes 65-75 days

Question 2

What are the types of spermatogonia

Answer 2

Type Dark A- reserve spermatogonia
Type Pale A- undergoes mitosis to give Type B spermatogonia
Type B- Divides by mitosis to give primary spermatocytes

Question 3

Do spermatogonia contain haploid or diploid number of chromosomes

Answer 3

Diploid number of chromosomes

Question 4

Describe how type dark A spermatogonia are ‘reserve spermatogonia’

Answer 4

they remain near the basement membrane of seminiferous tubules as precursor stem cells for future cell division and subsequent sperm production

Question 5

describe how Type pale A becomes type B and then primary spermatocytes

Answer 5

Type pale A spermatogonia lose their contact with the basement membrane and squeeze through the tight junction of the blood-testis barrier and differentiate into Type B and then they differentiate into Primary spermatocytes

Question 6

what happens to primary spermatocytes

Answer 6

They undergo DNA replication and Meiosis I begins which produces Secondary Spermatocytes

Question 7

What happens to secondary spermatocytes

Answer 7

Enters meiosis II and produces FOUR spermatids

Question 8

Are spermatids haploid or diploid

Answer 8

they are haploid

Question 9

What process occurs after 4 spermatids are made

Answer 9

Spermiogenesis

Question 10

Describe spermiogenesis

Answer 10

No cell division occurs here

Each spermatid becomes a sperm

Question 11

describe the structural changes a spermatid goes through to become a sperm

Answer 11

• Spherical spermatids transform into elongated, slender sperm
• An acrosome forms atop the nucleus
• tail forms for motility + mitochondira multiply
• sertoli cells phagocytose excess cytoplasm
• midpiece forms- area between head and tail

Question 12

What is the definition of spermatogenesis

Answer 12

Process by which immature stem cells (spermatogonia) proliferate and differentiate into mature sperm

Question 13

where does spermatogenesis takes place

Answer 13

Takes place in the seminiferous tubules

Question 14

how long do men make sperm for

Answer 14

Production from puberty until death

Question 15

Describe the hormonal regulation of spermatogenesis

Answer 15

All controlled by the brain

At puberty, hypothalamus causes the release of GnRH which acts on the anterior pituitary gland to release LH and FSH

Question 16

What is the purpose of FSH and LH in spermatogenesis

Answer 16

FSH enters the testes and stimulates sertoli cells to begin spermatogenesis using negative feedback
LH enters the testes and stimulates leydig cells to release testosterone into the testes and blood
–> Testosterone stimulates spermatogenesis

Question 17

What effect does testosterone and FSH have on sertoli cells

Answer 17

FSH and testosterone stimulate sertoli cells to support the developing germ cells.

Question 18

What happens once spermatogenesis reaches sufficient levels

Answer 18

sertoli cells produce inhibin, inhibin acts on the anterior pituitary:

• Limits FSH production
• Decreases spermatogenesis

Question 19

describe how testosterone has an inhibitory effect on GnRH once spermatogenesis reaches sufficient levels

Answer 19

Testosterone inhibits the secretion of GnRH by the hypothalamus
decreased FSH and LH secretion
decreased spermatogenesis

Question 20

Where does fertilisation take place

Answer 20

occurs in the ampulla of the uterine tubes

Question 21

what is the 1st step in fertilisation and describe it

Answer 21

Penetration of Corona Radiata:
Acrosome membrane begins to perforate, releasing the enzyme hyaluronidase- this disrupts the cell matrix and enables sperm to push through the remaining granulosa cells.

Question 22

What is the 2nd step in fertilisation and describe it

Answer 22

Penetration of Zona Pellucida
Receptors on acrosome bind to ZP3 molecules causing the release of acrosin- enzyme that digests glycoprotein chains of the zona pellucida. This allows the sperm to push through the weakened structure

Question 23

What is the 3rd step in fertilisation and describe it

Answer 23

Fusion of the plasma membranes:
Membranes of the sperm + oocyte bind via integrin receptors and fuse. sperm nucleus enters oocyte cytoplasm (leaving tail, membrane and mitochondria behind)

Question 24

what occurs after fusion of the plasma membranes (step 4 and 5)

Answer 24

Capacitation- Fast block and Slow block

Question 25

Describe Fast and Slow block (step 4 and 5)

Answer 25

Fast Block- Membrane fusion causes oocyte to depolarise, preventing other sperm from binding for about a minute

Slow block- the membrane fusion causes Ca to enter the oocyte -> releases cortical granules containing hydrolyic enzymes. these enzymes then break down the ZP3 molecules of the zona pellucida, permanently preventing other sperm from binding

Question 26

What occurs after fast and slow block (step 6)

Answer 26

Second meiotic division- Ca influx causes oocyte to complete 2nd meiotic division and produces 2 haploid cells

Question 27

What happens after 2nd meiotic division (step 7)

Answer 27

Nucleus of sperm enlarges to form a pronucleus. DNA within each sperm and ovum pronucleus enlarges.
Nuclear membranes surrounding the pronuclei breaks down. Maternal and Paternal chromosomes mix producing a diploid (46 chromosomes) zygote

Question 28

What happens after the 2nd meiotic division (step 8)

Answer 28

First MITOTIC division- zygote immediately begins to divide

Question 29

According to NICE, women aged under 40 should be offered 3 cycles of IVF treatment on the NHS if:

Answer 29

• They’ve been trying to get pregnant through regular unprotected sex for 2 years
• They’ve not been able to get pregnant after 12 cycles of artificial insemination

Question 30

According to NICE guidelines, women aged 40-42, should be offered 1 cycle of IVF treatment on the NHS if:

Answer 30

• They’ve been trying to get pregnant through regular unprotected sex for 2 years, or haven’t been able to get pregnant after 12 cycles of artificial insemination
• They’ve never had IVF treatment before
• They show no evidence of low ovarian reserve (where eggs in your ovaries are low in number or quality)
• They’ve been informed of the additional implications of IVF and pregnancy at this age

Question 31

What are the difference between assisted reproductive technologies criteria between scotland and england

Answer 31

Scotland- same rules apply throughout Scotland

England- rules differ throughout england due to different CCG (clinical commission groups) criteria

Question 32

what are some CCG criteria that need to be met before offered ART?

Answer 32

• Not having any children already, from both your current and any previous relationships
• Being a healthy weight (BMI must be above 18.5 and below 30)
• Not smoking
• Falling into a certain age range – NHS limit is 42 (for example, some CCGs only fund treatment for women under 35)
• Couple must be living together for at least 2 years

Question 33

what are some ethical considerations surrounding ART?

Answer 33

• unnatural means of conception (some religious bodies are against it)
• high cost (burden on NHS and burden on couple if carried out privately)
• safety of the procedure
• fate of the lost embryos