Functional Anatomy of the Normal male cat (tom)

General considerations

The reproductive system of the cat is unique amongst the domestic species in many respects. The system reflects the sexual and population dynamics of wild felids, and domestic breeds of cats have not had the types of selection pressures that face other species. The male reproductive system is to transfer spermatozoa to the female and the size and structure matches this.

Figure 1 : Normal reproductive tract,

The testis and epididymis is relatively small and is well protected beneath the tail. The scrotum is haired, unlike most other species. The domestic felids copulate in an almost vertical rather than horizontal fashion, and the penis has backward facing barbs or spines. There are 100-120 of these (McEntee 1990). Considerable discussion about the function of these spines has occurred, with the favoured theory being that spines ‘stimulate’ the female to ovulate – as the females are ‘induced ovulators. The penile barbs are keratinous projections that are testosterone sensitive. They appear about 9 - 13 weeks of age and are fully developed at 8 months. They disappear after castration.

The os penis of the cat is a rarity, only occurring in some old toms. When present, it is about 3-5 mm long

 

Figure 2 : Normal penis (with spines) and prepuce. Prepuce has been opened to show penile barbs.

The testis and epididymis is arranged in a horizontal axis with the epididymis being caudal, the head cranial and the body dorsal. The normal testis is oval in profile. The parenchyma of the testis is an off white to pale pink colour normally.

Franca and Godinho (2003) provide testicular morphologic and histologic characteristics. Testicular weight is about 1.2g and 0.08% testis weight to body weight. They recognised 8 stages of the spermatogenic cycle, which was 10 days per cycle with 4.5 cycles for at total of 46.8 days. Tubular diameter was 220um and there were 23m of tubules!

There are 14 to 17 efferent ductules in cats, arising from the mesonephric ductules (McEntee 1990). They fuse with the epididymal duct, that arises from the mesonephric duct. This duct is one tube that is coiled to for the head, body and tail of the epididymis.

Most male cats are castrated as juveniles to eliminate the unwanted behaviours and unpleasant odour of urine, aggressive behaviours and ‘male’ appearance of pronounced jowls. This effectively eliminates most diseases of the reproductive tract.

The internal genitalia is comprised of the bilobed prostate and bulbourethral glands, and these are small and seldom examined.

Figure 3 : Normal accessory genital glands. Bulbourethral glands are the swellings on the left; the bilobed prostate is on the right.

Normal histology

Histology of the scrotal skin.

The skin of the scrotum is much like skin in the rest of the body. As already indicated above, the normal scrotal skin is haired, so there are many hair follicles. Apocrine glands are absent, however.

Figure 4 : Histology of the scrotal skin of a cat.

There are bundles of smooth muscle present, as in other species.

Figure 5 : Histology of the scrotal skin - normal bundles of smooth muscle are present.

The normal penis of the cat has penile barbs - keratinous projections that are testosterone sensitive. They appear about 9 - 13 weeks of age and are fully developed at 8 months. They disappear after castration.

I am unaware of any special histological features, so the testis and epididymis have a similar appearance to that of the dog. Photographs of the normal canine testis can be found at this link.

According to Franca and Godinho (2003), the testis of the domestic cat weighs 1.2g each, the seminiferous tubules are 223 microns in diameter and the seminiferous epithelium is 81 microns high. The spermatogenic cycle was estimated at 47 days.

There is some seasonality in testicular function, depending on the time of year. Thus there is greater spermatogenic activity and a higher testosterone concentration in long days than short days - more in spring than in winter (Blottner and Jewgenow 2007, Stornelli et al 2009)

The normal rete testis of the cat is described in detail by Viotto et al (1993)

 

 

Blottner S, Jewgenow K.(2007) Moderate Seasonality in Testis Function of Domestic Cat. Reproduction in Domestic Animals 42 (5): 536–540.

Franca LR, Godinho CL. (2003)  Testis morphometry, seminiferous epithelium cycle length, and daily sperm production in domestic cats (Felis catus). Biol Reprod. 68(5):1554-61

Stornelli MA ,Reyna JC, Stornelli MC, Nun˜ ez Favre R, Savignone CA, Tittarelli CM and de la Sota RL (2009) Seasonal Changes in Testicular Cell Morphology in Domestic Male Cats (Felis catus). Reproduction in Domestic Animals 44 (Suppl 2): 278-290.

Viotto MJ, Orsi AM, Vicentini CA, Dias SM, Gregório EA.Ultrastructure of the rete testis in the cat (Felis domestica, L.). Anat Histol Embryol. 1993 Jun;22(2):114-22.

Spermatogenesis

Sanchez, Pizarro, Garcia and Flores (1993) record the postnatal development of seminiferous tubules in the cat. They examined the testes of 20 cats aged from 1 day to 1 year. Up to 4.5 months of age, the tubules are 'neonatal' in type, that is, the tubules were small, lined by sustentacular (Sertoli) cells only and spermatogonia were centrally located. There was gradual development of the normal type so that by 8 months, spermatogenesis was fully established.

Detailed analysis of the spermatogenic cycle was recorded by Franca and Godinho (2003).

There is some seasonality in testicular function, depending on the time of year. Thus there is greater spermatogenic activity and a higher testosterone concentration in spring than in winter (Blottner and Jewgenow 2007)

Gobello (2022) reviewed feline spermatogenesis. Spermatogenesis takes about 47 days. The testis weight is about 1.2 g and the seminiferous tubules are about 23 m long. They comprise 88% of the testis. They are 223+-5 um wide and the seminiferous epithelium is 81 um high. During spermatogenesis, 2.6 spermatozoa are produced per primary spermatocyte.

No compensatory hypertrophy occurs with hemicastration.

 

Blottner S, Jewgenow K.(2007) Moderate Seasonality in Testis Function of Domestic Cat. Reproduction in Domestic Animals 42 (5): 536–540.

Franca LR, Godinho CL. (2003)   Testis morphometry, seminiferous epithelium cycle length, and daily sperm production in domestic cats (Felis catus). Biol Reprod. 68(5):1554-61

Gobello C. Key aspects of domestic cat spermatogenesis. Reprod Domest Anim. 2022; 57: 459-464.

Age related changes

Elcock and Schoning (1984) reported on age related changes in the feline testis and epididymis. They examined 42 pairs of testes. Ten were from cats 0.5-1 year of age, 10 were 1 to 3 years, 10 were 3 to 5 years, 5 were 5-7 years, and 7 were 7 years or older.

Age associated changes increased with age including increased thickness of the tunica albuginea, the amount of lipofuscin in the interstitial endocrine cells, increased thickness of the basement membrane of the seminiferous tubules, and tubular degeneration.

Lymphocytic foci

It is apparently 'not uncommon' to see lymphocytic foci in the testes and epididymides of cats of all agees. Elcock and Schoning (1984) saw them in 8 cats of all ages. They were in the epididymis, testicular capsule (tunical abuginea) and spermatic cord.

Elcock LH, Schoning P. (1984) Age-related changes in the cat testis and epididymis. Am J Vet Res 45: 2380-2384

Hemeida Sanchez B, Pizarro M, Garcia P, Flores JM (1993). Postnatal development of seminiferous tubules in the cat. J Reprod Fertil Suppl 47: 343-348.