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Science of reproduction > Spermatogenisis > Flashcards

Spermatogenisis Flashcards

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1
Q

Where is the sperm produced and stored?

A

Sperm produced in the testes and stored in the epidermis

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2
Q

What happens during ejaculation?

A

there’s contractions in the epidermis and the vas deferens that propel the sperm and epidermal fluid into the seminal vesicle.

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3
Q

What is the pathway for sperm during ejaculation?

A
  • Sperm produced in the testes and stored in the epidermis
  • During ejaculation there’s contractions in the epidermis and the vas deferens that propel the sperm and epidermal fluid into the seminal vesicle.
  • Secretions from the seminal vesicles added to the mixture – continues to the ejaculatory duct.
  • Secretions from the prostate and Cowper gland also added during that – this makes up the ejaculate
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4
Q

What does the ejaculate contain other than sperm?

A
  • Epidermal fluid
  • Secretion from the seminal vesicle
  • Secretions from the prostate
  • Secretions from the Cowper gland
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5
Q

What keeps the urethra open for semen?

A

Corpus spongiosum under it is very flexible and it keeps the urethra open to allow a passage for semen.

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6
Q

What is the function of testes?

A
  • Produce sperm and store it.

* Produce hormones which regulate spermatogenesis ie tostesterone

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7
Q

Where are the testes found?

A

• Lie in scrotum outside body cavity – optimum temperature for sperm production 1.5-2.5oC below body. Overheating of testes reduces sperm count.

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8
Q

What is the structure of testes?

A
  • Tubules lead to an area on one side called rete testis.
  • Rete leads to epididymis (highly convoluted tubular structure) and that leads into vas deferens.
  • Epididymis is made of 3 segments: head, body, and tail
  • A Lot of lobes containing seminiferous tubules
  • Testis is 90% seminiferous tubules - the site of spermatogenesis.
  • 600m of seminiferous tubule in each testis. Tubules are tightly coiled.
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9
Q

What is the basal lining/basal laminar?

A

The outer lining of the seminiferous tubules

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10
Q

What is released in the lumen?

A

Spermatogenic cells/germ cells undergoing spermatogenesis and spermatozoa are released in the lumen.

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11
Q

Where are Sertoli cells found?

A

Between germ cell clusters

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12
Q

What is the function of Sertoli cells?

A

they respond to testosterone to regulate spermatogenesis and they provide sustenance for spermatogenic cells

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13
Q

Why is the mitotic division of primordial germ cells important?

A

Mitotic division of primordial germ cells is important because it means the male has a lifetime supply of sperm cells. Unlike females that a born with a fixed number of primordial oocytes.

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14
Q

What are the tight junctions?

A
  • Exist between Sertoli cells forming blood-testis barrier.

* Are almost like a seal

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15
Q

What do the tight junctions do?

A
  • Open to allow passage of spermatogonia prior to completion of meiosis
  • Protects the spermatogonia/germ cells from immune attack – if they get exposed immune system will create antibodies against sperm/germ cells
  • Allows specific enclosed environment for spermatogenesis which is filled with secretions from Sertoli cells.
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16
Q

What are the two compartments in testes?

A

Basal and adluminal compartments - they’re separated by the tight junction/blood-testis barrier

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17
Q

Where are Leydig cells found and what do they do?

A

Leydig cells outside the basal line – produce testosterone that crosses the basal membrane to go to Sertoli cells

18
Q

What are the different stages of sperms/spermatogenesis?

A
  1. Spermatogonia
  2. Primary spermatocyte
  3. Secondary spermatocytes
  4. Spermatids
  5. Spermatozoa
19
Q

How are the sperm like during the spermatogonia phase?

A

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

20
Q

How many types of spermatogonia are there and how are they different from each other?

A
  • There are 2 types of spermatogonia: A and B
  • There are also 2 categories type A spermatogonia: Dark and pale
  • Type A dark is capable of undergoing mitotic divisions to replenish itself or it could undergo differentiation to become type A pale
  • Type A can further differentiate to become type B
21
Q

How are the sperm like during the primary spermatocyte phase?

A
  • Cell committed to differentiative pathway, primary spermatocytes are 46XY diploid.
  • They move into the adluminal compartment and duplicate their DNA to produce sister chromatids which exchange genetic material and enter meiosis I – only type B can undergo this
22
Q

How are the sperm like during the secondary spermatocyte phase?

A

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

23
Q

How are the sperm like during the spermatid phase?

A

Meiosis II occurs to give 4 haploid spermatids. Round spermatid to elongated spermatid differentiation – end of meiotic divisions

24
Q

How are the sperm like during the spermatozoa phase?

A

Maturation of the spermatids, extra cytoplasm is removed, acrosome and tail formed. Mature sperm extruded into the lumen. This is called spermiogenesis.

25
Q

How long is the entire process of spermatogenesis?

A

74 days

26
Q

When does a new cycle of spermatogenesis start?

A

Every 16 days

27
Q

Summarise how sperm are made?

A
  1. Mitotic proliferation of spermatogonia.
  2. Meiosis and development of spermatocytes.
  3. Spermiogenesis, elongation, loss of cytoplasm, movement of cellular contents
28
Q

What controls the movement into the lumen?

A

Sertoli cell secretions

29
Q

What is the feedback of the HPG axis like in men?

A

In males there’s always a tonic level of production of the hormones – always constant and feedback is always negative

30
Q

What receptors do Leydig cells have?

A

LH receptors

31
Q

What is the Leydig cells function?

A

to convert cholesterol into androgens (testosterone)

32
Q

What do androgens do in the testes?

A

Androgens cross over to and stimulate Sertoli cell function and thereby control spermatogenesis.

33
Q

What receptors do Sertoli cells have and what do they do?

A
  • FSH receptors
  • FSH binding to Sertoli cells leads to production of androgen binding protein – it binds to testosterone and concentrates it within the epithelium to aid with spermatogenesis regulation
  • InhibinB is produced primarily by Sertoli cells in response to FSH
34
Q

What other purpose do the FSH and androgens have?

A
  • FSH establishes a quantitatively normal Sertoli cell population, whereas androgen initiates and maintains sperm production.
  • FSH also plays a role in helping the Sertoli cells plays their sustenance role
35
Q

What does Inhibin B do in males?

A

Inhibin B reduces FSH production by the anterior pituitary

36
Q

What is required for Inhibin B production?

A

Germ cells appear to be required for Inhibin B production

37
Q

Why is the middle piece important in the sperm?

A

Middle piece has ion channels that are intracellular calcium signalling when the sperm is in the female tract

38
Q

What is the normal ejaculate volume and how much of it is actual sperm?

A

Normal ejaculate volume is 1.5ml - 6ml.

Spermatozoa account for 1-5% of an ejaculate

39
Q

Name 6 roles of the seminal fluid

A
  • Transport of sperm through the male reproductive tract – sperm is non-motile is male reproductive tract
  • Coagulation of the ejaculate and creating a sperm deposit in the vagina – allows the sperm to actually get into the female reproductive tract
  • Creation of a neutral to slightly alkaline buffered milieu in the vagina to protect spermatozoa from the acidic vaginal milieu.
  • Activation and augmenting the motility of the sperm cells.
  • Coating the sperm cells with capacitation inhibitors.
  • Supplying nutrients for the sperm cells.
40
Q

What is analysed during semen analysis and what standards are used?

A 
Seme analysis is carried out according to the standards set by WHO. Things that are analysed include:
• Volume
• Appearance/colour
• Liquification
• Sperm concentrate
• Motility
• Progressive motility
• Morphology (normal forms)
• Vitality (live)
• pH
• leucocytes

Science of reproduction (32 decks)

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