Chapter 60 - Testis part I Flashcards
What does the scrotum of a horse contain?
The testes, associated ducts, and distal spermatic cords.
What is the function of the tunica dartos?
It regulates testicular temperature by relaxing with heat and contracting with cold.
Which vessel provides vascular supply to the scrotum?
The external pudendal vessels.
What type of muscle is the tunica dartos?
Involuntary muscle. This muscle
relaxes with heat and contracts with cold to regulate testicular temperature, thus varying the size of the scrotum
Where is the epididymis located on the testis?
On the dorsolateral border of the testis.
Name the three parts of the epididymis.
Head (caput), body (corpus), and tail (cauda).
How does sperm travel during ejaculation?
Through peristaltic contractions of the epididymis into the ductus deferens.
What covers the testis externally?
The tunica albuginea.
What is the role of the Sertoli cells in the testis?
They provide mechanical and nutritive support for developing spermatozoa.
What hormone stimulates spermatogenesis?
Follicle-stimulating hormone (FSH).
What do Leydig cells produce?
Androgens and estrogen.
What structure do the seminiferous tubules form when they converge?
The rete testis.
Where do the efferent ductules unite to form a single coiled tube?
In the head of the epididymis.
What is the inguinal canal?
An oblique passage in the abdominal wall through which the spermatic cord and other structures pass.
What forms the internal opening of the inguinal canal?
The deep inguinal ring.
What structure lines the wall of the inguinal canal?
The peritoneum, forming the tunica vaginalis.
What two layers make up the tunica vaginalis?
The visceral tunic and the parietal tunic.
What is the purpose of serous fluid in the vaginal cavity?
It lubricates to facilitate movement of the testis.
What is the gubernaculum testis?
A fetal mesenchymal cord that guides testis descent.
What does the cranial part of the gubernaculum testis become?
The proper ligament of the testis.
Where is the vaginal ring located?
About 10-12 cm abaxial to the linea alba and 6-8 cm cranial to the iliopectineal eminence.
What ligament connects the tail of the epididymis to the parietal tunic?
The ligament of the tail of the epididymis.
What could result from abnormal gubernaculum function?
Abdominal or inguinal retention of a testis.
What separates the right and left pouches of the scrotum?
A sagittal septum formed by the tunica dartos.
Which nerve supplies the scrotum?
The genitofemoral nerve.
Which tunic forms the scrotal sac lining?
The parietal tunic of the tunica vaginalis.
What hormone produced by the hypophysis stimulates Leydig cells?
Luteinizing hormone (LH) or interstitial cell-stimulating hormone.
Which side of the horse’s body usually has a larger, more caudal testis?
The left side.
The tail projects beyond the
caudal border of the testis, wraps around to the medial side, and
continues proximally as the
ductus deferens
Figure 60-1. Left testis and epididymis of a stallion, lateral aspect. a,
Testis; b, head of epididymis; c, body of epididymis; d, tail of epididymis;
e, proper ligamentum testis; f, ligament of the tail of the epididymis; g,
spermatic cord; h, cremaster muscle; i, external inguinal ring; j, vaginal
ring; k, visceral tunic; l, vaginal cavity; m, parietal tunic.
Figure 60-2. Graphic representation of the reproductive tract of the stallion, left-sided view. a, Testicular artery and vein; b, spermatic cords with their inguinal canal; c, external lamina of the prepuce; d, testis within scrotum; e, external inguinal ring; f, internal inguinal (vaginal) ring.
Figure 60-3. Descent of the testis. G, Gubernaculum; K, kidney; T, testis; U, ureter; V, vaginal ring.
Figure 60-4. Transverse section of the spermatic cord. 1, Testicular artery; 2, ductus deferens; 3, pampiniform plexus; 4, testicular nerves and lymphatic vessels; 5, mesorchium; 6, mesoductus; 7, cremaster muscle; 8, vaginal cavity; 9, spermatic fascia; 10, visceral layer of vaginal tunic; 11, parietal layer of vaginal tunic.
At what day of gestation do the gonads begin differentiating into testes or ovaries?
Day 40.
What ligament suspends the testis cranially at gestational day 55?
The cephalic (suspensory) ligament.
How large is the testis at 5 months of gestation compared to a mature stallion?
Nearly as large as that of a mature stallion.
What is the concentration of which hormone elevated in the mare during testicular hypertrophy?
Estrogen.
What is the gubernaculum’s role in testicular descent?
It guides the fetal testis from the kidney region to the scrotum.
At what gestational day does the gubernaculum begin to shorten?
Between 8 to 12 months of gestation.
What does the gubernaculum become after testicular descent?
It forms various ligaments, including the proper ligament of the testis.
What change occurs to the testis in the last month of gestation?
It regresses to one-tenth of its size.
What comprises the spermatic cord?
The tunica vaginalis, testicular blood vessels, nerves, lymphatics, and ductus deferens.
Is the cremaster muscle part of the spermatic cord?
No, it lies external to the parietal tunic.
What membrane encloses the neurovascular components of the spermatic cord?
The mesorchium.
Where does the ampulla of the ductus deferens form in the stallion?
Dorsal to the bladder.
What supplies blood to the cremaster muscle?
The cremasteric artery.
What structures are in the mesoductus deferens?
The ductus deferens and deferential vessels.
What structure is the mesoductus deferens continuous with?
The mesorchium.
What allows the testis to pass into the inguinal canal close to birth?
Increased intra-abdominal pressure and gubernaculum expansion.
What is monorchidism?
The complete absence of one testis.
How can monorchidism be confirmed?
Through an hCG-stimulation test or measuring anti-Müllerian hormone levels.
Define cryptorchidism.
It is a developmental defect where one or both testes fail to descend into the scrotum.
Why are bilateral cryptorchids typically sterile?
Because the seminiferous tubules are rudimentary due to high abdominal temperatures.
Why might cryptorchidism be considered genetically unsound?
The condition can be inherited and is often linked to genetic abnormalities.
What is the approximate prevalence of cryptorchidism among young colts?
About 17%.
Which breeds have the highest prevalence of cryptorchidism?
Percherons, American Saddlebreds, American Quarter Horses, ponies, and crossbred horses.
What dysfunction is thought to contribute to cryptorchidism?
Improper function or failure of the gubernaculum to enlarge or regress.
What role do androgens play in testicular descent?
They influence the development of the vaginal process and gubernaculum differentiation indirectly through the genitofemoral nerve.
How does the cranial suspensory ligament affect testicular descent?
Failure to regress may result in the testis remaining near the kidney.
What genetic factor was initially proposed in cryptorchidism studies?
Cryptorchidism could be an autosomal dominant or recessive trait, though the inheritance mechanism is complex.
What percentage of cryptorchid horses exhibit bilateral retention?
Studies show between 9% and 14%, with most retained testes being abdominal.
A study with 350 crypto found that ____% of left undescended testes were located within the abdomen, whereas only ___% of right undescended testes were retained abdominally
75% of left undescended testes were located within the abdomen, whereas only 42% of right undescended testes were retained abdominally
What type of intestine usually protrudes in inguinal herniation in horses?
Ileum or distal jejunum.
What is another term used interchangeably with inguinal herniation?
Scrotal herniation.
What occurs in a ruptured inguinal hernia?
Intestine protrudes through the vaginal ring and a rent in the parietal tunic and scrotal fascia, lying subcutaneously.
What distinguishes inguinal rupture from a direct hernia in horses?
Inguinal rupture lacks a peritoneum-lined sac.
Which horses are almost exclusively affected by inguinal herniation and rupture?
Stallions.
Why do geldings rarely develop inguinal hernias?
The vaginal rings decrease in size post-castration.
What type of inguinal hernia is typically congenital in foals?
Reducible hernia.
What potential congenital cause leads to inguinal hernia in foals?
Excessive outgrowth of the extraabdominal part of the gubernaculum
By what age do congenital inguinal hernias in foals typically resolve?
3 to 6 months.
what complication may arise from longstanding congenital inguinal hernias?
Testicular atrophy.
What activities may contribute to inguinal herniation in adult horses?
Exercise or copulation.
Which breeds show a higher incidence of acquired inguinal herniation?
Standardbreds, draft breeds, and Andalusian horses.
What clinical signs indicate obstruction of the small intestine in acquired inguinal hernia?
Nasogastric reflux recovery and palpable distended small intestine.
What typically causes strangulation in inguinal hernias?
Constricted intestine by the vaginal ring.
What condition may cause inguinal rupture in foals during birth?
Compression of the abdomen during parturition.
How might an inguinal rupture affect the overlying skin?
It can reduce skin viability due to compromised blood supply
What occurs in torsion of the spermatic cord?
The attached testis rotates on its vertical axis.
What term is incorrectly used to describe torsion of the spermatic cord?
Testicular torsion.
What are the consequences of testicular vessel twisting in spermatic cord torsion?
Venous and arterial obstruction leading to testicular congestion and edema.
In which breed is torsion of the spermatic cord most commonly reported?
Standardbreds.
What degree of spermatic cord torsion in horses generally requires emergency surgery?
360 degrees or more.
What might mild torsion of the spermatic cord in an abdominally located testis cause?
Mild colic signs.
What anatomic change indicates torsion of 180 degrees in the spermatic cord?
Tail of the epididymis in the cranial scrotum.
Why might 360 or 720-degree torsion of the spermatic cord be hard to palpate?
Severe swelling masks the epididymis.
What might predispose horses to testicular torsion anatomically?
Horizontally positioned testis in the scrotum.
How might abnormal ligaments increase risk for torsion?
Long ligaments make the spermatic cord prone to twisting.
What procedure can prevent torsion in the contralateral testis?
Orchiopexy (orchidopexy).
What is the suspected torsion risk difference between abdominal and descended testes?
Higher risk in abdominal testes.
What surgical action is often necessary in cases of severe torsion?
Removal of the affected testis
How is the proper ligament related to spermatic cord torsion?
Abnormally long proper ligament in abdominal testis may predispose to torsion.
In horses, where does torsion of the spermatic cord of the descended testis occur?
Intravaginally (within the vaginal process).
What is a hydrocele?
An abnormal collection of serous fluid between the visceral and parietal layers of the tunica vaginalis.
What causes a hydrocele?
It occurs when fluid production by the vaginal tunic exceeds the rate of resorption by lymphatic vessels and veins.
What term is sometimes used interchangeably with hydrocele?
Vaginocele.
What are some possible causes of hydrocele?
Testicular neoplasia, orchitis, abdominal fluid entering the vaginal cavity, parasite migration, torsion of the spermatic cord, trauma, and high temperature with inactivity.
How does a hydrocele affect spermatogenesis?
It may insulate the testis, causing temperature-induced dysfunction of spermatogenesis.
What are typical ultrasonographic findings in a hydrocele?
Anechoic to semiechoic fluid around the testis and epididymis.
What is the usual treatment for a persistent unilateral hydrocele?
Removal of the affected testis and parietal tunic.
Why is sclerotherapy rarely used for hydrocele in horses?
It is untested in stallions and could potentially reduce fertility.
What characterizes a hematocele?
A collection of blood within the vaginal cavity.
What often causes a hematocele?
Testicular or scrotal trauma or an extension of hemoperitoneum.
How is a hematocele differentiated from a hydrocele?
Through ultrasonographic examination and aseptic aspiration.
What potential complication can arise from a hematocele?
Formation of adhesions between the visceral and parietal tunica vaginalis.
What might indicate a rupture of the tunica albuginea in a hematocele?
Ultrasonographic examination showing possible damage to the testis.
What is a varicocele?
An abnormally distended and tortuous pampiniform plexus.
What causes a varicocele?
Valvular incompetence of the testicular vein, leading to increased hydrostatic pressure.
How might a varicocele affect spermatogenesis?
By causing elevated scrotal temperature and testicular hypoxia.
What sensation might a varicocele produce upon palpation?
A “bag of worms” texture in the affected spermatic cord.
What is the common treatment for a varicocele in stallions?
Removal of the affected spermatic cord and testis, if fertility is affected.
What can cause a testis to retract into the inguinal canal?
Persistent contraction of the cremaster muscle, often due to pain.
What surgical procedure can reposition a retracted testis?
Transection of the cremaster muscle.
What is a primary presenting sign of testicular neoplasia in horses?
Insidious testicular enlargement.
What are the two main categories of testicular tumors?
Germinal and nongerminal tumors.
Which type of testicular tumor is the most common in horses?
Seminoma.
From what cells do seminomas originate?
Germinal cells of the seminiferous tubules.
How does cryptorchidism relate to seminomas in horses?
Seminomas occur more frequently in cryptorchid testes and older horses
What is a potential sign of metastasis in testicular neoplasia?
Enlargement of the sublumbar lymph nodes.
What is a typical appearance of a seminoma on cross-section?
Lobulated, homogeneous, and grayish-white or white.
From what cells do Sertoli cell tumors arise?
Nonspermatogenic cells of the seminiferous tubules.
Are Sertoli cell tumors in horses typically benign or malignant?
They can be malignant, with cases of metastasis reported.
What type of testicular tumor is yellow to brown in color?
Leydig cell tumor.
What is the potential association between cryptorchidism and Leydig cell tumors?
Leydig cell tumors often occur in undescended testes.
what effect might a varicocele have on a stallion’s fertility?
It may reduce fertility, although unilateral varicoceles sometimes occur in fertile stallions.
What is the treatment for a hydrocele if it persists despite other interventions?
Removal of the affected testis and parietal tunic.
How can one diagnose a hematocele versus a hydrocele?
Through ultrasonographic examination and fluid aspiration to identify blood versus serous fluid.
How might an inguinal hernia relate to the conditions described in the text?
It can cause testicular trauma or vascular issues, potentially leading to conditions like hydrocele or hematocele.
What type of cells are responsible for the development of teratomas, and where are they commonly found?
Pluripotential cells; commonly found in the gonads.
Which germ layers contribute to the tissue composition of equine teratomas?
All three germ layers: ectoderm, mesoderm, and endoderm.
How do teratocarcinomas differ histologically from teratomas?
Teratocarcinomas contain undifferentiated embryonic tissue along with differentiated tissues, making them malignant.
What common assumption about cryptorchidism and teratoma formation is debated among researchers?
Some believe cryptorchid testes are more prone to teratomas, while others think cryptorchidism might be caused by teratomas rather than being a predisposing factor.
What are the defining characteristics of an equine male pseudohermaphrodite?
They have testes (gonadal male) but external genitalia resembling those of a female, often with hypoplastic testes and a penis-like structure resembling a clitoris.
What potential origin of some cases of equine hermaphroditism is suggested by researchers?
.
Chimerism resulting from double fertilization or blastocyst fusion
What external genital characteristics might a true hermaphrodite display?
They may display both male and female genital characteristics externally.
How do teratocarcinomas and embryonal carcinomas affect the prognosis of horses compared to teratomas?
Teratocarcinomas and embryonal carcinomas are malignant and rapidly fatal, unlike benign teratomas.
What chromosomal anomaly is commonly associated with equine male pseudohermaphrodites?
Many equine male pseudohermaphrodites are genetically female, with a 64, XX karyotype.
What type of information is collected in the history for testicular problems?
Infertility, testicular pain, size changes, surgery, illnesses, and drug therapy.
Why might knowledge of the onset of testicular pain be useful?
It helps in diagnosing testicular issues, especially if pain occurs after exercise or copulation
What are the key features assessed during physical examination of the testes?
Size, shape, texture, and temperature.
What does a scrotal scar potentially indicate?
It may suggest an attempted orchidectomy, even if it wasn’t completed.
Why is asymmetry in the scrotum of a normal stallion common?
Because the left testis has a longer spermatic cord, making it more pendulous.
What does scrotal edema usually imply?
It’s likely a result of fluid retention from diseases in other systems, not genital disease.
What condition might insensitivity to digital compression of a testis indicate?
Neoplasia, as neoplastic testes are often less sensitive.
What is the significance of palpating internal lymph nodes during testicular examination?
To check for possible lymphadenopathy associated with neoplasia.
How should the examiner position their hand when palpating the superficial inguinal ring?
The palm should face the abdomen for easier palpation.
Why might a tranquilizer be administered before testicular palpation in a cryptorchid stallion?
To relax the cremaster muscles, facilitating palpation.
What anatomical feature can be mistaken for a testis in a partial abdominal cryptorchid?
The epididymis within an everted vaginal process.
What is a per rectum examination used for in diagnostic procedures?
To assess the vaginal rings, inguinal canal, and abdominal structures for abnormalities.
What approach is recommended if a testis isn’t found in the inguinal canal during surgery?
Removal through the vaginal ring or a parainguinal incision.
What is the likelihood of correctly palpating an abdominal testis per rectum?
Low, as abdominal testes are small and mobile.
How accurate is palpation of the vaginal ring per rectum for detecting the ductus deferens?
88% accurate.
What precautions are taken to avoid complications during needle biopsy?
The scrotum is prepared aseptically, local anesthetic is used, and a strategic site is chosen.
What is aspiration biopsy typically used for?
Determining the cause of testicular enlargement.
Why is aspiration biopsy less damaging than needle biopsy?
It poses minimal risk to spermatogenesis.
Why is testicular material smeared gently after aspiration biopsy?
Testicular cells are fragile and can be easily damaged.
What are some of the complications specific to testicular needle biopsy?
Hematoma formation, necrosis
What fixative is used for biopsy samples before laboratory examination?
Bouin solution, followed by storage in ethanol.
Why is testicular biopsy used less frequently in horses?
Due to concerns about complications observed in other species.
What key information does a testicular biopsy provide?
It assesses spermatogenesis stages, sperm production rates, and identifies space-occupying lesions.
What are some causes of testicular enlargement that a biopsy can help differentiate?
Septic orchitis, neoplasia, and trauma.
How is an aspiration biopsy performed on a horse?
A 23- or 25-gauge needle is inserted into the testicular parenchyma, attached to a syringe, and material is aspirated.
Which needle sizes are commonly used for a needle biopsy of the testis?
12- or 14-gauge.
Why is the craniolateral quarter of the testis preferred for needle biopsy?
It has less prominent vasculature and is away from the epididymis.
Is testicular needle biopsy associated with a reduction in semen quality in horses?
No, a reduction in semen quality has not been observed in horses.
When is a hormonal assay necessary in horses?
When physical examination cannot confirm the presence of a retained testis.
What can be used to differentiate geldings from horses with retained testicular tissue?
Concentrations of testosterone or estrogen in plasma or serum.
How quickly does serum testosterone stabilize after castration?
Within about 6 hours.
What is the general testosterone concentration in castrated horses?
Less than 40 pg/mL.
Entire stallions was greater than 100 pg/mL.
What causes occasional confusion in measuring basal serum testosterone?
Overlapping testosterone values between geldings and stallions with testicular tissue.
How does the testosterone level of cryptorchid stallions compare to entire stallions?
Slightly lower in some studies, but possibly similar or higher in others.
What seasonal effect influences testosterone levels in entire stallions?
Levels are often lower in winter.
What does a response to hCG administration indicate in a hormonal assay?
It increases accuracy in detecting cryptorchidism.
How accurate was the hCG-stimulation test in predicting the presence of testicular tissue?
94.6% accurate.
Why is the hCG-stimulation test less reliable in young horses and in winter?
Due to poor response in horses under 18 months and seasonal variations.
How long does the testosterone increase last after hCG administration in entire stallions?
About 10 days.
What hormone assay was found superior to androgens in detecting testicular tissue?
Total free estrogen.
What estrone sulfate level generally indicates cryptorchidism?
Greater than 400 pg/mL.
How does anti-Müllerian hormone help diagnose equine cryptorchidism?
It is indicative of testicular tissue presence as it is produced by the testis.
What is the biological half-life of anti-Müllerian hormone?
212 days.
When does anti-Müllerian hormone become undetectable after castration?
Approximately 2 weeks post-castration.
entire stallions was greater than 100 pg/mL.
entire stallions was greater than 100 pg/mL.
How much do you administer of hCG and how much time do you verify the testosterone?
30 and 120 minutes after intravenous administration of 6000 or 12,000 units of hCG
which animals do not consistently produce estrogen?
donkeys
crypto less than 3 years
what are the estrogen values indicatve of cryptorchidism or gelding?
Horses with a concentration of estrone sulfate less than 50 pg/mL in plasma or serum were determined to be geldings.
A concentration in excess of 400 pg/mL indicated cryptorchidism
which US transducer is used for transabdominal scan?
longitudinally placed 3.5-MHz convex probe or a 5-MHz transrectal transducer
describe the US of a normal testicle
round, homogeneous structure, surrounded by a more echogenic tunica albuginea, with an anechoic line inside, representing the central vein of the testis.
The sensitivity of transabdominal ultrasonography in detecting an undescended testis is
98%
what can you perform to increase the changes of finding an abdominal testis?
Withold feed from 24 to 36 hours
Transrectal US can also be performed if the testis is not found transabdominal. What is the sucess rate %?
100% accordingly with one report
