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Human development block > Control of testicular function and sperm physiology > Flashcards

Control of testicular function and sperm physiology Flashcards

1
Q

What is the function of the testicles?

A
  • production of sperm

- secretion of androgens

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2
Q

What is the length of the seminiferous tubules ?

A

500m

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3
Q

Describe the structure and function of the seminiferous tubules

A

A.) spermatogonial stem cells for sperm production

B.) sertoli cells: support,nutrition, protection,secretory,excretory

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4
Q

Describe the characteristics of spermatogenesis

A
  • starts at puberty
  • Maintains species
  • Mitosis followed by meiosis
  • 120million sperm/day or 1500/sec
  • whole cycle takes 72days
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5
Q

What is spermiogenesis?

A
  • final stage of spermatogenesis, which sees the maturation of spermatids into mature, motile spermatozoa.
  • Repackaging
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6
Q

What is the function of the sertoli cells?

A
  • Provide structural support
  • create two compartments
  • Provide nutrients for mature sperm
  • Eliminate degenerate germ cells
  • Secrete inhibin, ABP, AMH and growth factors.
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7
Q

What is the function of the Leydig cells?

A

Secrete androgens (C19), mainly testosterone

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8
Q

What are the actions of testosterone?

A
  • Male hormone, anabolic (bone&muscle mass)
  • Primary and secondary sexual characteristics
  • Libido and sexual behaviour
  • Stimulates sertoli cells and spermatogenesis
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9
Q

What are the two compartments of the seminiferous tubule?

A

1.)adluminal compartment, near the lumen of the seminiferous tubule
2.)Interstitial compartment,the basal spermatogonal cell and the interstital cells of Leydig
They are separated by the blood-testicular barrier

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10
Q

What makes up the blood-testicular barrier?

A

The intracellular junctions of the sertolli cells.

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11
Q

Describe the Hypothalamic-Pituitary-Gonadal axis

A

Hypothalamus releases GnRH which stimulates the pituitary to release LH&FSH which stimulate the testes to release testosterone.

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12
Q

Describe the role of testosterone in the feedback loop.

A

Takes part in negative feedback. Testosterone feeds back to the hypothalamus to reduce the release of GnRH& also on the pituitary to reduce the release of FSH& LH (thus directly and indirectly)

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13
Q

Which cells do FSH & LH act on?

A

the FSH acts on the Sertoli cell while LH acts on the Leydig cell. Testosterone also acts on the Sertoli cell.

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14
Q

What is testosterone aromatised into?

A

Estradiol.

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15
Q

What is testosterone reduced to?

A

DHT

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16
Q

Where are FSH receptors located?

A

On the surface of the Leydig & Sertoli cells.

17
Q

Describe the role of the Sertoli cells and testosterone in negative feedback of the FSH &LH

A
  • The Sertoli cells produce INHIBIN which inhibits FSH.

- The testosterone inhibits the LH production.

18
Q

Describe the different elements of sperm transport.

A
  • Ejaculation: deposition of sperm in vagina(acidic)
  • Cervix: mucous barrier and crypts act as sperm reservoirs-motility is important
  • Uterus and tubes: mild contraction to propel the sperm towards the egg
  • Ampullary portion of the tube: fertilization
19
Q

What is sperm capacitation?

A

Refers to the physiological changes spermatozoa must undergo in order to have the ability to penetrate and fertilize an egg.

  • “switching on” of sperm- HYPERACTIVE
  • Takes about 4 hours after ejaculation
  • cholesterol loss and calcium influx
20
Q

Outline the acrosome reaction.

A
  • Triggered by contact with oocyte
  • Interaction with ZP3 protein on oocyte membrane
  • Leads to exposure of hyaluronidase and acrosin enzymes
  • Facilitates oocyte penetration
21
Q

Outline Oocyte activation.

A
  • Release of cortical granules. This acts as a block to polyspermic penetration
  • Resumption of meiosis
  • Formation of the male and female pronuclei (fertilisation)
22
Q

Which factors affect sperm production?

A
  • Recreational anabolics abuse
  • Environment
  • Non-hormonal factors: e.g vasectomy= the male vas deferens are cut and tied or sealed so as to prevent sperm from entering into the urethra
  • Heat exposure( optimum temp. for testes is 35 degrees Celsius which is why they are located outside the body)
  • Radiation
  • Air pollution
  • Food chain pollution
  • stress &reduced sexual activity may also play a role
23
Q

Outline the mechanism of factors causing infertility

A
  • A factor( such as smoking,drugs, varicocele or cancer) causes oxidative stress( oxygen,hydrogen peroxide or hydroxide)
  • This then causes protein damage, lipid peroxidation,bio-membrane damage or DNA damage, which ultimately leads to sperm damage and thus infertility.
24
Q

At which level can there be disturbance in regulation of testicular function?

A
  • Genetic level
  • Hypothalamic level
  • Pituitary level
  • Target tissue level
25
Q

What is the presentation of Klinefelter syndrome?

A

47 XXY

  • Taller than average height
  • reduced facial and body hair
  • gynaecomastia
  • Osteoporosis
  • Feminine fat distribution
  • Small testes( testicular atrophy)
  • May cause delayed puberty
26
Q

What is Kallman syndrome?

A
  • is a genetic disorder that prevents a person from starting or fully completing puberty
  • a form of a group of conditions termed hypogonadotropic hypogonadism
  • More common in men
  • infertility
  • affected at the olfactory bulb& tract
  • These patients have no sense of smell or a reduced sense of smell because those nuclei develop next to the olfactory bulb
  • Due to lack of development of the hypothalamic nuclei that are responsible for producing GnRH
  • can be treated with HRT
27
Q

What is androgen insensitivity syndrome?

A
  • Partial or complete inability of the cell to respond to androgens
  • genetically a man, phenotypically a woman
  • There could be target tissue level abnormality i.e normal testosterone production from testicle but tissue not respond effectively, it may lack receptors
  • 46 XY but phenotypically female because the target tissue can’t respond to the testosterone
28
Q

What does testicular function ultimately depend on?

A

The delicate interaction between the two testicular compartments.

29
Q

What is the function of the pampiform venous plexus

A

contains cooler venous blood to absorb heat from arterial blood in the testes.
-so regulates temp. of the testes

Human development block (35 decks)

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