Repro physiology 2 - Spermatogenesis, sperm maturation and semen assessment

Spermatogenesis

• Large numbers of sperm produced

Which animal produces the most sperm

Rams and boars produce even more

Seminiferous tubules also produce

fluid containing nutrients for sperm

Sperm moved through

tubules to epididymus where stored

The blood-testes barrier (BTB) Formed by

complex junctions between adjacent sertoli cells

The blood-testes barrier (BTB) Separate the

seminiferous tubule into two main compartments – central and basal

What is the function of The blood-testes barrier (BTB)

• Prevent passage of water-soluble substances from blood vessels in the outside of the tubules to the central compartment

What is able to pass through the The blood-testes barrier (BTB)

• Only lipid-soluble substances like androgens and estrogens can pass through the central compartment and into the lumen of the tubules

The blood-testes barrier (BTB) protects what

• Also protects spermatozoa from immune responses

What are the four stages of spermiogenesis

• Golgi phase

• Cap phase

• Tail phase (Acrosome/Elongation phase)

• Maturation phase

The first phase of the spermiogensis is ?

Golgi phase

What is the Gogli phase

The Golgi apparatus produces enzymes that aggregate to form the acrosomal vesicle at one end of the nucleus, which will later help the sperm penetrate the egg.

What is the second stage of spermiogenesis

Cap phase

What is Cap phase:

The acrosomal vesicle spreads over the anterior half of the nucleus, forming the "cap," while the nucleus begins to condense.

What is the third phase of spermiogenesis

Tail phase (Acrosome/Elongation phase)

What is Tail phase (Acrosome/Elongation phase):

The centrioles migrate to the opposite end of the nucleus to initiate the assembly of the flagellum (tail). The nucleus elongates and becomes more streamlined, often shaped by a microtubule structure called the manchette.

What is the fourth stage of spermigenesis

Maturation phase

What is the Maturation phase:

The spermatid sheds excess, unnecessary cytoplasm (residual body), which is phagocytosed by Sertoli cells, resulting in a mature, compact spermatozoon ready for release

What happens after the final maturation phase of spermigenesis

After the final maturation phase, spermatozoa are released from Sertoli cells into the lumen – this process is termed spermiation.

Number of Sertoli cells positively correlated with

daily sperm production

Sertoli cells are also called

‘nurse cells’

Are spermatozoa released into the seminal tubule mature?

• No, they are incapable of fertilizing an egg

Are spermatozoa released into the seminal tubule mature, motile?

Non-motile

Are spermatozoa released into the seminal tubule mature structurally immature?

yes they are Structurally immature

What are the spermatozoal characteristics

• not moltile

• no fertile

• proximal cytoplasmic droplet

• low disulfide crosslinkign

Iniital maturation of spermatozoa takes place where?

in the epididymal

What is occurring in further maturation of spermatoza in the epidiymal tail

• expression of normal motility after dilution

• fertile potential

• distal droplet

• high degree of disuldide crosslinking

• can bind to oocytes

Highly concentrated sperm that are

motile, morphologically developed, highly compressed nucleus

Outer surface of the sperm head is covered by

glycoproteins

Glycoproteins enables recogtion of what

Enable recognition and binding of egg, protection from female immune system and capacitation and acrosome reaction

Motility is limited/restricted in the

cauda epididymis to conserve energy

What are two key things that keep sperm quiescent

• pH and HCO3

Spermatozoa transit time in epididymis is?

Normal passage time 8–14 days depending on species

DHT is concentrated in the

epididymis by ABP, and this slows sperm transport

What is the transit time for Spermatozoa transit time in epididymis in bull

10-14 days

What is the transit time for Spermatozoa transit time in epididymis in boar

9-14 days

What is the transit time for Spermatozoa transit time in epididymis in dog

10-14 days

What is the transit time for Spermatozoa transit time in epididymis in human

2-6 days

What is the transit time for Spermatozoa transit time in epididymis in camel

42 days

Spermatozoa movement by the

the coordinated contraction of adjacent doublets (attached to outer dense fibers) within the axoneme

Semen composition

• Clears the urethra of urine (pre-ejaculate fraction)

• Medium for sperm motility

• Nourishment (fructose, glucose, various minerals)

• Protector (e.g., pH buffer, anti-oxidant enzymes, prevent immune attack)

• Proteins involved in capacitation, acrosome reaction, and sperm-oocyte reaction

• Modulator of sperm function

• Ovulation inducing factor (β nerve growth factor) in induced ovulators

• Forming vaginal plug (rodents and primates)

• Stimulate peristaltic contractions of female reproductive tract

Seminal plasma produced by

accessory glands

The three fractions of the semen ejaculate are?

1) Pre-ejaculatory fraction

2) Sperm-rich fraction

3) Prostatic fraction

What is occurring in the Pre-ejaculatory fraction

• Little-to-no sperm

• Clear fluid from accessory glands

What is occurring in the Sperm rich fraction

• Rich in sperm with a cloudy

What is occurring in the prostatic fraction

• Low sperm count

• A large volume of prostatic fluid (bulk of the semen composition)

In horses, pigs and dogs, the third fraction is usually collected separately?

1 and 2 collected together. In other domestic animals, all three fractions are collected together.

Why should ejaculate/semen quality be assessed?

• Detect sperm morphological defects

• Predict fertility of males

• Monitoring reproductive health of males

• Quantify sperm numbers

What are the factors for Semen quality

• Volume

• Morphology

• Opacity/color

• Motility

• Live:dead ratio (viability)

• Concentration

• pH

Why measure pH?

• Low pH: urine contamination

• high pH: infection

What is the ranger for semen pH

• Ranges from 6 – 9

What is Nigrosin:

Counterstain that binds to and stains the cell membrane of sperm head for contrast.

What is Eosin:

Membrane impermeable stain. Stains cytoplasmic structures when membrane integrity damaged to allow entry.

What is the description of good sperm concentration

• Milk or creamy

What color is semen when there is white blood cells

• green

What color would urine contamination (or due to riboflavin/B12 in bulls) look like in semen color

Yellow

What color haemospermia (trauma to penis or prostate looks like in the semen color

• Red/brown

When low sperm count (oligospermia or azoospermia) describe the semen color

Clear