Spermatogenesis

Question 1

Where is sperm produced?

Answer 1

testis
outside the body cavity to maintain temp and prevent death of sperms due to overheating
15- 25ml volume of sperm

Question 2

Where is sperm stored?

Answer 2

epididymis

Question 3

testicular structure and function

Answer 3

testis is 90% seminiferous tubles - and is the site of spermatogenesis
600m seminiferous tubule all coiled togther tightly , lead to rete testis and rete testis leads to the epididymis and the efferent ductules Which lead to the head of the epididymis, tail of epididymis leads to vas deferen that travels around the prostate and semi vesicular fluid and comes down to the urethra

testis function is to form testis and store it

Question 4

What is the structure of seminiferous epithelium?

Answer 4

The seminiferous tubules is where spermatogenesis takes place
The seminiferous epithelium has sperm cells at different stages of development (spermatogenesis) and contains tight junctions and in between these tight junctions are Sertoli cells which control the movement of substancesfor spermatogenesis

Question 5

What is the function of sertoli cells?

Answer 5

• sertoli found between germ cells (tight junctions)
  -respond to testosterone and regulate spermatogenesis via the formation of tight junction
• controls movement of substances into the lumen
  -factors produced by sertoli cells is required for development.

Question 6

What is the function of tight junctions?

Answer 6

-space between sertoli cells
-forms blood testis barrier
-open to allow passage of spermatogonia prior to completion of meiosis
-Divides into basal and adluminal compartments
-protects the spermatogina from immune attack, immune
-allows specific enclosed environment for spermatogenesis which is filled with secretions from sertoli cells

Question 7

What are the two compartments formed as a result of tight junctions?

Answer 7

Lumenal compartment and adluminal compartment.

Question 8

What are the 5 stages of spermatogenesis?

Answer 8

1. spermatogonia
2. primary spermatocyte
3. Secondary spermatogenesis
4. Spermatids
5. spermatozoa

Question 9

What happens in Spermatogonia stage?

Answer 9

germ cell on basement membrane, capable of mitotic or meiotic division to produce primary spermatocytes or more spermatogonia by mitosis. They are diploid.

Question 10

What happens in primary spermatocyte stage?

Answer 10

cell committed to differentiative pathway, primary spermatocytes are 46 XY diploid. They move into the adluminal compartment and duplicate their DNA to produce sister chromatid which exchange genetic material and enter meiosis I

Question 11

What happens in the secondary spermatocytes stage?

Answer 11

have undergone meiosis I to give 23X + 23Y haploid number of chromosomes, arranged as sister chromatids

Question 12

What happens in the spermatids stage?

Answer 12

meiosis II occurs to give 4 haploid spermatids. Round spermatids to elongated spermatid differentiation.

Question 13

What happens in the spermatozoa stage?

Answer 13

mature sperm extruded into the lumen.

Question 14

What are the 3 main stages of spermatogenesis?

Answer 14

1. mitotic proliferation of spermatogonia
2. meiosis and development of spermatocytes
3. Spermatogenesis, elongation, loss of cytoplasm, movement of cellular content

Question 15

What is the length of a spermatogenesis cycle?

Answer 15

new cycle every 16 days, entire process takes approx 74 days.

Question 16

Which two hormones control of spermatogenesis?

Answer 16

1. FSH
   2.LH

Question 17

How does FSH control spermatogenesis?

Answer 17

1. acts directly on sertoli cells and regulates sertoli cell number
2. acts to produce nutrients to growing sertoli cells
3. FSH binds to sertoli cell and they produce androgen binding protein (ABP) and this ABP binds to testosterone and concentrates testosterone to regulate with spermatogenesis.
   => sertoli cells contain FSH receptors and convert androgens to oestrogen

Question 18

How does LH control spermatogenesis?

Answer 18

LH binds to LH receptors on Leydig cells outside the basal lamina in seminiferous epithelial cell and leydig cells produce testosterone
testosterone acts on sertoli cells to regulate spermatogenesis.

Question 19

What is the function of inhibin B

Answer 19

• produced primarily by sertoli cells in response to FSH
• production of inhibin B has a negative feedback on pituitary and FSH production is reduced.
• germ cells appear to be required for inhibin B production
  => sertoli cells convert androgens(T) to oestrogen, they have FSH receptors but production of inhibin B by germ cells and sertoli cells themselves inhibits FSH which means less conversion of testosterone, so more T can act on sertoli cell for spermatogenesis.
  -FSH and inhibin B in combination has been correlated with testicular volume and spermatogenic activity but this hasn’t proved clincally useful as yet.

Question 20

ejaculation and seminal components

Answer 20

300 million sperm produced per day an average - 3500 per second and approx 120 million in average ejaculate
normal ejaculate volume is 1.5ml - 6ml, spermatozoa accounts for 1-5% of an ejaculate
initial portion of ejaculate is most sperm rich 99.9% lost before reaching ampulla of the uterine tube (around 120, 000 sperm get near to egg, only one enters)
seminal fluid consists of secretions from: seminal vesicles, prostate, bulbo-urethral gland combined with epididymal fluid.

Question 21

What is the role of seminal fluid?

Answer 21

• transport of sperm through the male reproductive tract
• coagulation of the ejaculate and creating a sperm deposit in the vagina
  -creation of a neutral to slightly alkaline buffered milieu in the vagina to protect spermatozoa from the acidic vaginal mileu
• activation and augmenting the motility of the sperm cells.
• coating the sperm cells with capacitation inhibitors
• supplying nutrients for the sperm cells

Question 22

What is the semen analysis to measure male fertility?

Answer 22

volume = 1.4-6.0ml (1.5 previously)
appearence/colour = grey-opalescent
liquefaction : <30 minutes
sperm conc: >16 million/ml (15 mil previously)
motility : >42% (40% previously)
progressive motility : >30% (32% previously)
morphology (normal forms) : > 4 % (no change)
vitality (live) : >54% (58% previously)
pH = 7.2- 8
leucocytes = <1 million/ ml (higher is indicative of illness)

Question 23

What are some limitations of semen analysis?

Answer 23

• standardised analysis revised in 2021
• new diagnostics look at more factors like fragmentation - however more costly
• changes made from 2010 to 2021, larger data set used in 2021 so more robust

Question 24

structure of spermatoza

Answer 24

acrosome - 2/3 region of head
nucleus - stores genetic info
tail - for swimming

Question 25

summary

Answer 25

- sperm production is continuous from puberty - process os long and complex with many errors - objective is to produce high numbers - process driven by FSH and testosterone - sperm highly specialised for function.

Question 26

meiosis

Answer 26