Spermatogenesis Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

What is the testes?

A
  • produce sperm + store it
  • produce hormones which regulate spermatogenesis
  • lie in scrotum outside body cavity (optimum temp for sperm prod 1.5-2.5 deg below body)
  • overheating of testes reduces sperm count
  • well-vascularised, well-innervated
  • normal volume of testis approx 15-25ml
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the structure of the testis like?

A
  • testis is 90% seminiferous tubules - site of spermatogenesis
  • 600m long in each testis, tubules are tightly coiled
  • tubules lead to an area on one side called rete
  • rete leads to epididymis and vas deferens
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What kind of cells are the walls of the tubule made up of?

A
  • tall columnar endothelial cells = Sertoli cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What surrounds the sertoli cells?

A
  • between sertoli cells, lying on basement membrane are primary germ cells or spermatogonia
  • spaces between tubules are filled w/ blood + lymph vessels, Leydig cells + interstitial fluid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

The sertoli cells form tight junctions between each other. Why is this important?

A
  • tight junctions open to allow passage of spermatogonia to completion of meiosis
  • the junctions allow for divisions into luminal and adluminal compartments
  • protects spermatogonia from immune attack
  • allows specific enclosed enviroment for spermatogenesis which is filled w/ secretions from sertoli cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the comparisons and differences between oognia and spermatogonia?

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How long does spermatogenesis take?

A
  • entire process = approx 74 days
  • new cycle every 16 days
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the 3 main stages of spermatogenesis?

A
  • mitotic proliferation of spermatogonia
  • meiosis + development of spermatocytes
  • spermiogenesis, elongation, loss of cytoplasm, movement of cellular contents -> spermatids (haploid)

Movement into lumen controlled by sertoli cell secretions. Factors produced by sertoli cells are required for development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the role of Leydig cells?

A
  • contain LH receptors
  • primarily convert cholesterol into androgens
  • intra-testicular testosterone levels are 100x those in plasma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens to the androgens following production by Leydig cells?

A
  • androgens cross over to + stimulate Sertoli cell function
  • thereby control spermatogenesis
  • Sertoli cells contain FSH receptors
  • convert androgen -> oestrogen
  • FSH establishes a quantitavely normal Sertoli cell population
  • whereas androgen initiates + maintains sperm production

so sertoli cells need FSH to maintain its population and need testosterone to undergo spermatogenesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do anabolic steroids lead to testicular atrophy?

A
  • negative feedback on hypothalamus/pituitary
  • reduce FSH/LH secretion
  • it’s FSH which maintains sertoli cell population
  • so testicular atrophy results due to reduced FSH!
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How can anabolic steroids also lead to gynaecomastia in men?

A
  • araomatase present in men (as well as women)
  • lots of unbound anabolic steroids
  • they are aromatised into oestrogens from androgens
  • build up of oestrogen -> gynaecomastia
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What structural changes occur to cause and maintain erection?

A
  • vasodilation of corpus cavernosum (+ its arteries)
  • engorging corporal tissue with blood
  • egorging causes corporal tissue to swell, erecting penis
  • engorged corporal tissue compresses penile veins + venules, maintaining erection
  • partial constriction of venous return
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What part of the nervous system are erection and ejaculation under control of?

A
  • both under autonomic nervous system
  • “point + shoot”
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What exactly is under each of parasympathetic and sympathetic control in terms of erection and ejaculation?

A
  • parasympathetic: erection + evacuation of urethra
  • sympathetic: movement of sperm into epididymis, vas def, penile urethra expulsion of glandular secretions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How much sperm is produced per day on average?

A
  • 300 million sperm produced per day
  • 3,500 per second!
17
Q

What is normal ejaculate volume?

A
  • 1.5ml - 6ml
  • around one third to just over a teaspoon full
18
Q

The initial portion of the ejaculate is most sperm rich. How much sperm reaches the ampulla of the uterine tube?

A
  • 99.9% lost before reaching ampulla of uterine tube
  • around 120,000 sperm get near to egg
  • only 1 enters
19
Q

Seminal fluid consists of secretions from where?

A
  • seminal vesicles
  • prostate
  • bulbo-urethral gland combined w epididymal fluid
20
Q

What is the role of the bulbo-urethral gland in contributing to seminal fluid?

A
  • secreted before ejaculation
  • produces a clear viscous secretion high in salt
  • known as pre-ejaculate
  • this fluid helps to lubricate the urethra for spermatozoa to pass through
  • neutralising traces of acidic urine
21
Q

What is the role of the seminal vesicles in contributing to seminal fluid?

A
  • 50-70% of ejaculate
  • contains proteins, enzymes, fructose, mucus, vit C, prostaglandins
  • high fructose conc provide energy source
  • high pH protects against acidic env in vagina

if you don’t find fructose in semen -> could be a seminal vesicle problem

22
Q

How does the prostate contribute to the seminal fluid?

A
  • arrives here microsecond later following seminal secretions
  • secretes milky white fluid
  • 30% of seminal fluid
  • protein content is less than 1%
  • incldues proteolytic enzymes, prostatic acid phosphatase + prostate-specific antigen - all involved in liquefaction
  • high zinc conc: 500-1,000 times that in the blood is antibacterial
23
Q

Describe semen analysis

A
  • Volume: 1.5-6.0ml
  • Sperm conc: >15million/ml
  • Liquefaction: <30 mins
  • Motility: >40%
  • Prog motility: >32%
  • Vitality (live): >58%
  • Morphology: >4%
  • pH: >7.2
  • Leucocytes: >1million/ml
24
Q

What is the structure of a normal spermatozoon?

A