Learning Reproduction in Farm Animals

LEARNING OBJECTIVES:

• To learn the nomenclature and structures of the male reproductive system.
• To understand the functions of these structures and how they are interrelated to prove the complete reproductive process in the male.

Reproductive Organs in the Male:

 
 Overall functions of the male:

• Produce and maintain supply of sperm

 
• Detect females in estrus

 
• Inseminate females and fertilize the female gamete

 

Structure of the Testis:

• Structures of the Testis

• Cross-section of Testis

1. Produce Sperm

 

 
 

2. Transport sperm out of testis

 
 
 
 
 
 
3. Produce testosterone

 
 
 
 Testosterone functions
 

Thermoregulation of the Testis:

One major factor is the Scrotum

Scrotal Properties that facilitate thermoregulation
 
1. Location of Testis

 
 
2. Low insulation

 
 
3. Sweat gland

 
 
4. Tunica Dartos

 
• Change in testis location

 
 
 
• Change in scrotal surface area

 

 

5. External Cremaster Muscle

 

 

6. Thermoreceptors

 
 

 2nd Major Factor - Blood supply to testis.

1. Pampiniform Plexus

 

 
 
 

2. Convoluted testicular artery on the surface of the testis.

 

Cryptorchidism - Lack of testis descent into scrotum and thus thermoregulation.

• Bilateral - Is sterile.

 

 

• Unilateral - Is fertile - Reduce sperm producing capacity.

 

 

• Common in boars and stallions.

 

 
 
 
 
 
 
 

Functions of the Epididymus:

1. Transport of sperm - 9-11 days in bull

 

 

1. Pressure of new sperm

 
 

 

2. Regular contraction of smooth muscle

 

 
 

3. Stimulated contractions of cauda

 

 

Concentration of sperm

 

 
Mechanism
 
 
Fluid absorbed in Caput

 
 

 
 
1. Sperm gain ability to be motile and fertilize the oocyte

 

 

2. Involves biochemical and physical changes to sperm

 
 
 
3. Controlled by rate of transport through epididymis and epididymal secretions

 
 
 
4. Epididymal fluid changes

 

 

Examples of changes sperm undergo:
 
 
1. Increase in specific gravity

 

2. Nucleus more condensed and stable

 
 
3. Increase (-) charge on plasma membrane

 
 
4. Sperm become less resistant to cold shock

 
 
5. Migration of cytoplasmic droplet

 
 

 

 

1. ~70% of sperm in cauda

 

 

2. 4 days of testicular sperm prod. stored

 

 

3. Can be stored for several weeks

 

 

Factors conducive to storage
 
 
1. Reduced pH

 

 

2. Low O2 High CO2

 

 

3. High K:Na ratio

 

 

4. Low concentrations of energy substrates

 
 
Other factors related to epididymal function
 
 
1. Temperature

 
 
 
2. Testicular androgens

 
 
 
3. Ejaculation frequency

 
 
 
 

Sperm Numbers in regions of the male tract (X 10⁹)

 

	Sexually  Rested Bull	Depleted  Bull (20 ejac 5 hr)	Bull on  (6 ejac/wk)
Caput	19.4	16.2	22.6
Corpus	4.7	3.0	5.2
Cauda	37.6	13.7	26.4
Vas Deferens & Ampulla	7.9	2.1	3.3

 

Fate of unejaculated sperm

• ½ of produced sperm not available for ejaculation

 
• Resorbed by excurrent duct system

 

 

• Some selective removal of abnormal sperm in epididymis (macrophages)

 
 
• Sperm lost in urine

 

 Masturbation loss of sperm

 
 

Functions of Vas Deferens and Ampulla for transport of sperm

1. Low level steady contractions of Vas Deferens

 

 

2. Increased contractions caused by sexual excitement

 

 

3. Sperm stored in ampulla age rapidly

 
 
• Increased temperature

 
 
• Poorer environment for sperm

 

 

Functions of seminal plasma:

1. Transport media

 

 

2. Culture media

 
 
3. Stimulates sperm motility

 
 
 
4. Retards sperm capacitation

 
 

 

5. Stimulates sperm transport in female

 
 

Sources of seminal plasma:

1.
 
2.
 
3.
 
4.

5.

6.

7.
 
 

Chemical composition of seminal plasma:

Nutrients
 
 
1. Fructose

 
 
2. Sorbital

 
 
3. Glycerol Phosphorylcholine

 
 
4. Lactic Acid

 
5. Fatty Acids

 
6. Amino Acids

 

 

Buffers
 
 
1. Bicarbonate

 
 
2. Citrate

 
Structure of Citric Acid

 
Other Components
 
1. Ergothioneine

 
2. Cysteine

 
3. Glutathione

 
Function to protect sperm
 
 
• Sperm produce H202

 
 
AA-SH HS-AA + H202 -> -S-S- + 2H20
 
 
4. Prostaglandins

 
 
 
5. Glycoproteins

 
 
• Sperm

 
 
• Sperm decapacitation

 
 
6. Enzymes

 
 
7. Ions:
Na K Zn Ca Mg
 
 

Stimulation of sperm metabolism
 
 

i.e. increased Na decreased K
 

Bull (Ram)

Not fractionated
 
 
Pre-ejaculation dribble - Cowpers
 
 

Ejaculate - Seminal Vesicles & Prostate
 
 

Fractionated
 
 
Presperm - Urethral glands (Disseminate Prostate) & Cowpers?
 
 

Sperm rich - Epididymal, Ampulla & Prostate
 
 

Postsperm - Gel from Seminal Vesicles
 
 

Penile Drip - Prostate, Cowpers & Uretheral Gland
 
 

Fractionated
 
 
Presperm - Urethral glands (Disseminate Prostate)
 
 

Sperm Rich - Seminal Vesicles & Prostate
 
 

Postsperm - Gel - Cowpers gland
 

Illustrated Notes

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