Lecture 4 Flashcards
The male reproductive system role
Gametogen (testicle) )
produce 1-25 bil. Spermcells/day
35.000-290.000 sp./sec.
1 cm3 produce 20.mil sp/day
Endocrine (testicle).
Delivery system (intra-and extrapelvic urethra)
The male reproductive system sturcture
Gonads (testes);
Sperm ducts;
Accessory glands:
Seminal vesicles; (vesicular glands)
Prostate;
Bulbouretral glands;
The male reproductive system anatomy
Spermatic cord
The pampiniform plexus is a vascular structure
consisting of an intimately intertwined artery and
vein.
This highly specialized structure is important for
proper temperature control of the testis.
In most mammals the testis must be 4 to 6°C
cooler than the body in order for spermatogenesis
to occur.
The spermatic artery leaves the body and enters
the spermatic cord as an uncoiled vessel
The pampiniform plexus is a vascular structure
consisting of an intimately intertwined artery and
vein.
This highly specialized structure is important for
proper temperature control of the testis.
In most mammals the testis must be 4 to 6°C
cooler than the body in order for spermatogenesis
to occur.
The spermatic artery leaves the body and enters
the spermatic cord as an uncoiled vessel
The cremaster muscle
- The primary muscle supporting the testis
- The cremaster is a striated muscle which is continuous with the internal abdominal oblique muscle.
- It helps support the testis and aids in control of testicular temperature.
- Its temperature control function is probably related to the fact that when the cremaster muscle contracts and relaxes, it creates a “pumping action” on the pampiniform plexus, thus facilitating blood flow and enhancing cooling efficiency.
- In some species (the ram and, to some degree, the bull) sexual excitation promotes a high degree of intermittent contractile activity of the cremaster muscle.
- During sexual excitation the testes move up and down in a rapid manner.
- Unlike the smooth muscle in the scrotum (tunica dartos), the cremaster muscle is not capable of sustained contractions.
- The cremaster muscle may be important in short term elevation of the testicles during fear or high planes of excitement.
- Such a function would tend to protect the pendular testes during periods of physical confrontation or flight from danger.
The Scrotal Skin
- The scrotal skin is heavily populated with sweat glands required for maintenance of proper testicular temperature.
- The scrotal sweat glands are innervated by large numbers of thermosensitive nerves
- Elevated body temperature or elevated scrotal temperature, is detected by the hypothalamus and sends nerve impulses to the sweat glands.
- Sweating allows the scrotum (and thus the testes) to be cooled by evaporative heat transfer.
- These sensory nerves govern both the degree of scrotal sweating and respiratory rate of the animal.
- In fact, in the ram changes in scrotal temperature can bring about dramatic changes in respiratory rate.
The tunica dartos?
- Is an open meshlike smooth muscle layer which lies just beneath the scrotal skin.
- The degree of contraction of this smooth muscle is constantly being adjusted in response to changes in scrotal skin temperature.
- The sensory nerves initiating the changes in the tone (degree of contraction) of the tunica dartos are located in the scrotal skin.
- The smooth muscle of the tunica dartos can maintain sustained contractions.
- This characteristic allows the testes to be held close to the body for sustained periods during cold temperatures.
- On the contrary, during the hot summer months, the tunica dartos relaxes and thus the surface area of the scrotum increases substantially to facilitate cooling.
- This increase in surface area of the scrotum is
- closely linked to scrotal perspiration.
- As the scrotum perspires, the increased surface area allows for a greater rate of evaporative heat loss and more rapid and efficient cooling,
The testicular parenchyma consists of:
- seminiferous tubules
- iuterstitial cells of Leydig
- Capillaries
- lymphatic vessels
- connective tissue
The parenchyma can be divided into:
The parenchyma can be divided into 2:
The seminiferous tubule
- Form highly convoluted loops, the ends of which join with the rete tubules.
- Each loop of a seminiferous tubule is composed of a convoluted portion (tubulus contortus) and a straight portion (rectus) which join the rete tubule
The tubular compartment consists of:
- Seminiferous epithelium
- Sertoli cells
- Developing germ cells
- Peritubular cells
The Excurrent Duct System
The epididymis
The time required to transport spermatozoa from the proximal head of the epididymis to the distal tail is referred to as epididymal transit time.
- Boar :9-14 days
- Bull :14 days
- Ram :12 days
- Stallion 9 days
Epididymal transit time is constant among species Smooth muscle in the tail of the epididymis tends to be quiescent except during periods of sexual excitation, when contract vigorously, Epididymal transit time through the head and body is not altered by sexual excitation.
The Epididymis (2)
- In sexually rested males, the sperm content of the tail is maximal, while males experiencing a high ejaculation frequency have 25% to 45% fewer sperm in the epididymal tail.
- Spermatozoa spending an unusually long time in the tail (such as after long periods of sexual rest) may be of poor quality when compared to sperm from animals ejaculated routinely (once or twice weekly).
- Some males tend to accumulate sperm in the epididymis rather than void them periodically, which probably constitutes a loss of viability.
- Spermatozoal removal from the epididymis is caused by
periodic contractions of the epididymis and ductus
deferens, resulting in a gradual trickle of spermatozoa out
of the tail, through the ductus deferens, into the pelvic
urethra where they are flushed out of the tract during
urination. - This trickle allows removal of sperm from the epididymison a continual basis.
- There is no reabsorption of sperm in the epididymal duct.
Factors that control epididymal transit
- nervous system
- endocrine systems (oxytocin, acetylcholine,prostaglandins and angiotensin)
