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In this handout, the major anatomic subdivisions of the male genital system will be considered individually. Although there is some overlap, diseases tend to initially or predominantly affect only a single structure (scrotum, penis, etc.).
The scrotum forms a protective covering for the testicles and it is well adapted for its function of maintaining the testis at a temperature less than that in the abdominal cavity. Because of its location and the delicacy of its covering skin, the scrotum is quite vulnerable to trauma and/or inflammation. Inflammation of the scrotal skin is not uncommon. The skin is subjected to bacterial and viral infections similar to those that occur on any other part of the skin.
The tunica vaginalis is the serosal lined sac that contains the testis and epididymis. This structure may be involved in any of the following:
Which refers to the accumulation of clear serous fluid in the tunica vaginalis. the fluid may be a part of generalized edema or ascites or it may be associated with local factors (neoplasia, etc.).
Refers to the accumulation of chyle in the tunica vaginalis. This is usually associated with lymphatic obstruction.
Refers to the accumulation of blood within the tunica vaginalis and is oftentimes associated with trauma.
Of the tunica vaginalis occurs frequently in peritonitis and as a complication of orchitis and epididymitis.
Cryptorchidism refers to incomplete descent of the testicle and the condition has been reported in all species. Evidence suggests that the condition is inherited. The position of the retained testis will vary from case to case, but it is most commonly found at the internal inguinal ring. The retained testicle has several characteristic features which make it different from a normal testicle:
The retained testicle is sterile because of the higher temperature to which it is subjected. Thus, spermatogenesis is absent (however, the interstitial cells are present and active). The exception to sterility because of high temperature is found in fowl. In fowl, the testicles are always located in the abdominal cavity (just ventral to the vertebral column at the anterior pole of the kidneys). Remember, if only one testicle is retained, only that one will be sterile and the descended testicle will be fertile. (If the descended testicle is removed and the retained one is not removed, the animal will continue to resemble and act like an intact male. In dogs, there is a tendency for neoplasms, i.e., sertoli cell and seminoma, to develop in the retained testicle.)
The term hypoplasia implies that the testes failed to develop fully. The condition is known to be inherited only in the Swedish Highland cattle. Hypoplasia is usually suspected only at the time of puberty or later when the animal exhibits lowered or absence of fertility (decreased fertility corresponds with the degree of hypoplasia). Sexual activity of the affected animal is normal. Microscopically, the lesions will vary depending on the degree of hypoplasia. In more severe cases, there is no evidence of spermatogenesis and the basement membranes are hyalinized. The diameter of the seminiferous tubules is reduced. In less severe cases, there may be varying degrees of spermatogenesis. Grossly, the changes are similar to those described for cryptorchidism.
The testicular germinal epithelium is very sensitive to a variety of adverse influence (heat, trauma, infections, etc.) and degeneration readily occurs. In fact, testicular degeneration is considered to be the most common cause of reduced fertility in male animals. Permanent and progressive degeneration occurs quite frequently in all species without any indication of its pathogenesis. However, the pattern and signs of testicular degeneration are the same regardless of the causes or the species affected. The involvement may be bilateral or unilateral. Grossly, the affected organ may or may not be reduced in size. However, it is usually soft and flabby. The cut surface does not bulge (as does the normal testicle). In chronic stages, fibrosis occurs and the organ will be quite firm. Microscopically, the changes will vary depending on the severity and stage of degeneration. In early stages, there is failure of maturation of spermatozoa and spermatids undergo degeneration and become necrotic. In later stages, there is progressive fibrosis. Frequently, it is not possible to distinguish testicular degeneration from testicular hypoplasia on the basis of microscopic findings.
Inflammation of the testes is referred to as orchitis. Orchitis is usually caused by bacterial agents and there may be a concurrent epididymitis. The causes of orchitis include: Brucella spp. in bulls and boar, Corynebacterium pyogenes in bulls and rams, E. coli and Proteus vulgaris in dogs. Grossly, there is swelling of the affected testicle. Microscopically, there is interstitial edema and a mononuclear cell infiltration (neutrophils will dominate if the condition is due to pyogenic agents). During healing there will be varying degrees of fibrosis.
In bulls, Brucella abortis (and strain 19 of this organism) is the most common infectious cause of orchitis. The condition may be unilateral or bilateral (the animal is usually sterile even when the condition is unilateral because of the mixing of inflammatory products with the semen from the normal testis. Also, the non-inflammatory testis undergoes some thermal degeneration.) The inflammatory reaction may be both necrotizing and suppurative.
Primary testicular neoplasms are common only in aged dogs. The tree primary tumors of the testes are
is the most common testicular tumor in the dog. Evidence suggest that this tumor does not produce excessive androgenic hormones (however, androgens are produced by normal interstitial cells). Grossly, interstitial cell tumors are usually small (up to about 2 cm in diameter) and they are yellowish, well-demarcated and slightly encapsulated. Microscopically, the neoplastic cells are larger and have more eosinophilic cytoplasm than sertoli cell tumors or seminomas. The cytoplasm is foamy and contains large amounts of lipids (much of the lipid is anisotropic under polarizing light). The cells tend to form masses which are divided into compartments by fibrous connective tissue. Mitotic figures are seldom found and these tumors are nearly always benign.
may secrete excessive estrogen resulting in the development of a feminization syndrome in affected males. The feminization syndrome is manifested by
Do not produce hormones. They are not often malignant but are probably more so than sertoli cell or interstitial cell tumors. Grossly, the cut surface is coarsely lobulated. The color is usually white or grayish white and the texture is soft to moderately firm. The color and texture closely resemble that of neoplastic lymphoid tissue. Microscopically, the earliest development of the tumor is intratubular and this pattern can usually be observed. However, rupture of tubules occurs and the growth becomes confluent, forming broad sheets of closely packed cells with little supporting stroma. Individual cells are large, polyhedral and fairly discrete.
Inflammation of the epididymis often coexists with orchitis. However, there is a tendency for infections to be more common in the epididymis than in the testis. Of course, infections may ultimately reach the testis from the epididymis by direct or lymphatic spread. Epididymitis causes by Brucella ovis in the ram may occur in the absence of a concurrent orchitis. Brucella ovis epididymitis is purulent in the acute stages. In chronic stages, fibrosis and atrophy of both the epididymis and testis occur. There is a tendency for sperm granulomas to develop in the involved epididymis.
Sperm granulomas develop when sperm escape from the ductal system. This may be due to infections (Brucella ovis, etc.) or it may be a sequela to a cystic dilatation (spermatocele) of the epididymal duct that subsequently ruptures. Spermatoceles may be congenital or they may be associated with acquired occlusions. In any event, the cystic duct becomes impacted and inspissated with sperm. If rupture occurs, sperm are released and they come in contact with stroma resulting in a granulomatous response. Microscopically, sperm granulomas closely resemble tubercules (sperm release acid fast lipids similar to mycotic acid which apparently determines the nature of the granulomatous response). The sperm body is markedly resistant to disintegration. Therefore, inspissated sperm can usually be found in granulomas.
Inflammation of the spermatic cord is referred to as funiculitis. The condition is common in pigs subjected to open castrations because of their proximity to the ground, their unsanitary surroundings and the crude type of surgery which is oftentimes performed by stockmen and others. In the pig, funiculitis is usually a necrotizing and purulent response. If large amounts of granulation tissue form on the stump of the severed spermatic cord, the term scirrhous cord is used. Funiculitis and scirrhous cord are observed in horses (funiculitis is a pyogenic infection usually caused by staphylococcal organisms).
The most common conditions affecting the prostate gland are:
In general, prostatic diseases are common only in the dog. Prostatic diseases are uncommon in other species with the exception of inflammation in boars and bulls caused by Brucella spp.
Inflammation of the prostate is referred to as prostatitis and the condition is rather common in dogs. Acute prostatitis is characterized by suppuration, either in the form of minute, discrete abscesses or as large coalescent areas of involvement. Chronic prostatitis is most often a sequel to acute prostatitis and thus represents the continued presence of a smoldering infection. The causative agents in prostatitis are nonspecific. They may include: Escherichia coli, Proteus vulgaris, Streptococci, and Staphylococci which invade via the urinary system.
Prostatic hyperplasia is common only in dogs and it usually becomes evident at 4 to 5 years of age and increases in severity with advancing years. The enlarged prostate is frequently associated with constipation that results from pressure on the rectum. Interference with micturition is less frequent. The reason(s) for urinary retention has not been completely elucidated. Apparently, hormonal imbalances play an important role in the development of prostatic hyperplasia (Hyperplasia does not occur in castrated male animals. Once hyperplasia is established, castration brings relief.). Grossly, the hyperplastic gland is larger than normal, the surface is irregularly nodular and many small (or a few large) cysts may be found over the surfaces. Microscopically, the condition is characterized by hyperplasia of glandular and stromal elements with cyst formation.
Estrogens apparently have profound effect on the prostate. One of the earliest responses to low levels of estrogen over a short period is atrophy of acinar tissue. However, large amounts of estrogens result in enlargement and cyst formation along with squamous metaplasia. This response is observed in dogs with large estrogen secreting sertoli cell tumors. Squamous metaplasia of the prostate occurs in male castrated sheep grazing on clovers (red clover, subterranean clover, etc.) possessing high estrogenic content. However, intact sheep are not affected.
Occasionally, calculi consisting primarily of phosphates and carbonates of calcium will be found in the prostate of the dog. They apparently arise in association with chronic prostatitis and/or prostatic hyperplasia. If stones are numerous, they may result in severe irritation or they may be obstructive.
Inflammation of the penis and prepuce is referred to as balanoposthitis which is common and important. There are a number of infectious agents that may be associated with the penis and prepuce. These include:
Phimosis refers to narrowness of the orifice of the prepuce. The condition may be congenital, but it oftentimes results from or accompanies balanitis. In congenital phimosis, the preputial orifice may be so small that urine is expressed only with difficulty and the sheath in such cases is often distended with urine. The phimosis that occurs in adolescent puppies often corrects itself as the dog becomes sexually mature.
Paraphimosis refers to a constriction of the prepuce posterior to the glans penis. The usual case of paraphimosis is actually partial phimosis that prevents retraction of the swollen glans into the sheath following erection.
Neoplasms of the penis occur with some frequency in horses and cattle. In bulls, the only neoplasm of significance is the fibropapilloma. This is a viral induce, cauliflower-like tumor that tends to ulcerate and bleed. In horses, squamous papillomas and squamous cell carcinomas occur. The transmissible venereal tumor occurs on the penis of dogs.
The gonads are greatly enlarged in the equine fetus from the 4th or 5th month to the 9th month of gestation. There is an increase of interstitial tissue and the gonads may be 5 to 7 cm long and 4 cm in diameter and weigh up to 150 grams (this is as large or larger than in adult horses). The gonads reduce markedly in size the last few months of gestation.
SLIDE 1: CANINE: ILLUSTRATION OF NORMAL ANATOMICAL FEATURES.
SLIDE 2: CAPRINE SCROTUM: DERMATITIS OF SCROTAL SKIN - Observe the areas of inflammation over the scrotal skin. Actually, the inflammation extended into the scrotal sac and involved the testis. (What term is used to refer to inflammation of the testis?).
SLIDE 3: OVINE SCROTUM: ABSCESSATION OF THE SCROTUM - The scrotum of this sheep was greatly distended with purulent exudate. It was actually touching the ground and the animal had difficulty carrying the extra weight. The pus was located in the tunica vaginalis and Corynebacterium pseudotuberculosis was recovered on microbiologic examination. (What term is used to refer to an adult intact sheep? What other lesions, etc., would you expect to find in this sheep? Name a specific disease in sheep that may be associated with the etiologic agent recovered on microbiologic examination.).
SLIDE 4: OVINE SCROTUM: HERNIA - Observe the enlarged scrotum. A loop of small intestine passed down through the inguinal canal into the scrotal sac. (What complications would you expect to occur in this animal?).
SLIDE 5: MONKEY TESTICLE: HERNIA (FAT) - Observe the abdominal fat completely surrounding a testicle. The scrotum was enlarged and a mass could be palpated clinically.
SLIDE 6: CANINE TESTICLES: CRYPTORCHIDISM - Observe the large mass in the abdominal cavity of this small dog. The right testis was retained and a neoplasm (sertoli cell tumor) developed. Actually, the neoplastic, retained testis weighed nearly as much as the dog. (How would you expect this male dog to interact with females? What changes would you expect to find in the prostate gland? Name one other neoplasm that may develop in a retained Testis. On gross inspection, how would you differentiate a retained testis from a normal testis?).
SLIDE 7: CANINE TESTICLE: CRYPTORCHIDISM - The microscopic section denotes the hypoplastic changes associated with a retained testis. Note the degenerative changes as well as the absence of sperm.
SLIDE 8: CANINE TESTICLE: CRYPTORCHIDISM - Microscopic section from a retained testicle. Observe the small number of tubules (atrophic also) with interstitial tissue predominating. This dog was apparently sterile.
SLIDE 9: CANINE TESTICLE: CRYPTORCHIDISM - This is a close-up view of slide #8 (microscopic).
SLIDE 10: BOVINE TESTICLE: TESTICULAR DEGENERATION WITH FIBROSIS - This testis is characterized by degenerative changes and replacement fibrosis. On palpation, it was rather soft and flabby. The animal was slaughtered because of reduced fertility and the lack of value as a breeder.
SLIDE 11: BOVINE TESTICLE: TESTICULAR DEGENERATION - This microscopic section denotes the changes associated with testicular degeneration. Observe the disoriented and distorted tubules. There is an absence of spermatogenesis.
SLIDE 12: BOVINE TESTICLE: TESTICULAR DEGENERATION- Observe the severe degenerative changes with giant cell formation. The animal was sterile.
SLIDE 13: CAPRINE TESTICLE: ORCHITIS - This is a chronic orchitis due to Corynebacterium pseudotuberculosis. Observe the large amounts of fibrous connective tissue.
SLIDE 14: CAPRINE TESTICLE: ORCHITIS - This is a close-up view of slide #13. Observe the suppurative foci in incised portion of the testis. This animal had a condition that's commonly referred to as caseous lymphadenitis.
SLIDE 15: BOVINE TESTICLE: ORCHITIS - This is chronic orchitis in a bull. Observe the areas in which connective tissue has replaced normal parenchyma.
SLIDE 16: BOVINE TESTICLE: ORCHITIS - This is a microscopic section or orchitis due to Brucella abortis. In this low power field, the dark areas represent suppurative foci with many neutrophils. Considerable connective tissue is also present. There is complete absence of normal tubules in this section.
SLIDE 17: BOVINE TESTICLE: ORCHITIS - This is another section through the same testis denoted in slide #16. Many inflammatory cells can be observed. No normal testicular tissue is present.
SLIDE 18: CANINE TESTICLE: SERTOLI CELL TUMOR - Observe the multiple tumor nodules in the testes of this dog. (Discuss the feminization syndrome. What hormone(s) would you expect this tumor to produce? What changes would you expect to find in the prostate gland? Would there be a tendency for this dog to seek females?).
SLIDE 19: CANINE TESTICLE: SERTOLI CELL TUMOR - The large tumor-like testis was retained and a sertoli cell tumor developed. The small or more or less normal size testis had descended into the scrotum. Note the enlarged mammae.
SLIDE 20: CANINE TESTICLES: SERTOLI CELL TUMOR - This is an incised testis which had been replaced for the most part by a sertoli cell tumor. Can you appreciate the connective tissue associated with this mass?
SLIDE 21: CANINE TESTICLE: SERTOLI CELL TUMOR - This is a microscopic section from a sertoli cell tumor. Observe the proliferation of rather elongated sertoli cells as well as the increased amounts of connective tissue.
SLIDE 22: CANINE TESTICLE: INTERSTITIAL CELL TUMOR - Observe the proliferation of interstitial cells around acini. Note the absence of sperm. (Discuss the occurrence, gross and microscopic lesions that you would expect to find.).
SLIDE 23: CANINE TESTICLE: INTERSTITIAL CELL TUMOR - This is a close-up view of slide #22. Observe the proliferating interstitial cells as well as the location and appearance of the tubules.
SLIDE 24: CANINE TESTICLE: SEMINOMA - This microscopic section of a seminoma denotes the heavy proliferation of neoplastic cells with little supporting stroma.
SLIDE 25: CAPRINE EPIDIDYMIS: SPERM GRANULOMA - Observe the enlarged and discolored end of the epididymis as indicated by the arrow. On incision, yellowish material that resembled pus was present. This condition was caused by Brucella ovis. There was no involvement of the testes. (Give the pathogenesis of a sperm granuloma caused by Brucella ovis. What does the term inspissated mean to you? Give a reason(s) why sperm granulomas oftentime resemble tubercules.).
SLIDE 26: CAPRINE EPIDIDYMIS: SPERM GRANULOMA - This is a low power view of a sperm granuloma. Observe the fibrosis and sparsity of tubules.
SLIDE 27: CAPRINE EPIDIDYMIS: SPERM GRANULOMA - This microscopic section denotes the dilated and sperm filled tubules associated with sperm granulomas. Also note the interstitial fibrosis.
SLIDE 28: CAPRINE EPIDIDYMIS: SPERM GRANULOMA - Observe the dilated tubules which are filled with inspissated sperm. (Give a likely etiologic agent or mechanism).
SLIDE 29: CANINE PROSTATE: PROSTATITIS - Acute suppurative prostatitis. This prostate is markedly enlarged (swollen) with bulging surfaces (please refer to slide #30).
SLIDE 30: CANINE PROSTATE: PROSTATITIS - Acute suppurative prostatitis. Observe the purulent exudate in the swollen prostate. (Give a likely pathogenesis of this condition.).
SLIDE 31: CANINE PROSTATE: PROSTATITIS - Acute suppurative prostatitis. This microscopic section is characterized by the presence of many neutrophils.
SLIDE 32: CANINE PROSTATE: PROSTATITIS - This is a close-up view of slide #31. Observe the inflammatory cells.
SLIDE 33: CANINE PROSTATE: PROSTATITIS - This microscopic section is characterized by the presence of considerable fibrous connective tissue as well as many inflammatory cells (chronic prostatitis).
SLIDE 34: CANINE PROSTATE: PROSTATITIS - Chronic prostatitis. This is a close-up view of slide #33. Observe the fibrosis and inflammatory cells.
SLIDE 35: CANINE PROSTATE: HYPERPLASIA OF THE PROSTATE - Observe the markedly enlarged prostate with few cysts. Note the location of the urinary bladder and urethra. (Where would you expect to find the seminal vesicles? In addition to hyperplasia, would you expect to find evidence of hypertrophy in this gland? What are the expected clinical affects of prostatic hyperplasia?).
SLIDE 36: CANINE PROSTATE: HYPERPLASIA OF THE PROSTATE - Observe the many cystic structures found over the surface of this prostate. (Would you expect this to be a castrated or a non-castrated male?).
SLIDE 37: CANINE PROSTATE: HYPERPLASIA OF THE PROSTATE - This microscopic section denotes some of the changes associated with prostatic hyperplasia. Note the increased number of acinar epithelial cells. (How would you differentiate prostatic hyperplasia (the condition observed in this slide) from a carcinoma of the acinar epithelial cells?).
SLIDE 38: CANINE PROSTATE: HYPERPLASIA OF THE PROSTATE - This is a close-up view of slide #37. Observe the growth of acinar epithelial cells into the lumens of the acini.
SLIDE 39: CANINE PROSTATE: SQUAMOUS METAPLASIA OF THE PROSTATE - Observe evidence of squamous metaplasia of the prostatic epithelial cells. Also note the dilated tubules and increased fibrous connective tissue. (What type epithelial cells would you expect to find in a normal prostate? Give a likely pathogenesis for the condition observed in this slide. Under what conditions would you expect to find prostatic squamous metaplasia in sheep? in dogs?).
SLIDE 40: CANINE PROSTATE: SQUAMOUS METAPLASIA OF THE PROSTATE - This is a close-up view of slide #38. Observe the metaplastic changes and fibrosis.
SLIDE 41: CANINE PROSTATE: SQUAMOUS METAPLASIA OF THE PROSTATE - Observe squamous cells in markedly dilated tubules.
SLIDE 42: CANINE PROSTATE: CALCULI OF THE PROSTATE - Observe the small calculi in a cystic cavity. The central nucleus was most likely desquamated cells or other dead cells.
SLIDE 43: CANINE PROSTATE: CALCULI OF THE PROSTATE - Observe the many stones present in the prostate of this dog.
SLIDE 44: MINK PENIS: BALANOPOSTHITIS - Observe the reddened and swollen penis. The mink was unable to retract the penis (paraphimosis).
SLIDE 45: EQUINE PENIS: PARAPHIMOSIS - This is paraphimosis associated with an inflamed and swollen prepuce. The horse was unable to retract the penis following an erection. In addition, the glans penis is inflamed (Balanoposthitis).
SLIDE 46: EQUINE PENIS: PARAPHIMOSIS - Observe the protruded penis that could not be retracted.
SLIDE 47: BOVINE PENIS: FIBROPAPILLOMA - Observe the large necrotic neoplastic growth located on the penis of this bull.
SLIDE 48: BOVINE PENIS: FIBROPAPILLOMA - Note neoplastic growth.
SLIDE 49: BOVINE PENIS: FIBROPAPILLOMA - Note the characteristic microscopic features as denoted by this slide. (Describe the significant microscopic features of a fibropapilloma and a squamous cell carcinoma.).
SLIDE 50: EQUINE FETAL GONADS: NORMAL GONADS - Observe the large size of the fetal gonads. Note the abdominal location and the relationship to the kidneys.
SLIDE 51: EQUINE FETAL GONADS: NORMAL GONADS - Incised equine fetal gonads.
