Testis Flashcards
Four layers of the scrotum
1) Skin
2) Dartos
3) Spermatic fascia
4) Parietal vaginal tunic
Parts of the gubernaculum, attachments and what they become
1) Cranial part. Attaches the tail of the epididymus to the testis. Becomes the proper ligament of the testis
2) Middle part. Attaches the tail of the epididymus to the parietal vaginal tunic. Becomes the ligament of the tail of the epididymus
3) Caudal part. Extends from abdominal wall to the scrotum. Becomes the scrotal ligament attaching the parietal tunic to the scrotum. This is usually elongated in crypts and may be referred to as the inguinal extension of the gubernaculum
Testicular orientation in the stallion and bull
Stallion - horizontally aligned, head of the epididymus cranially and tail caudally
Bull - vertically aligned with the head of epididymus dorsally and tail caudally
Path of the ductus (vas) deferens
Travels from the tail of the eipdidymus (continuation of the epididymal duct) to empty into the pelvic urethra, at the colliculus seminalis, via the ejaculatory ducts, which are the combined opening of the ductus deferens and ipsilateral seminal vesicle
What structures open at the colliculus seminalis
Ejaculatory ducts (combined duct of ductus deferens ampullae and seminal vesicles)
Accessory sex glands and their urethral openings
Seminal vesicles (paired) - open at the colliculus seminals via ejaculatory ducts (common opening with ductus deferens ampullae)
Prostate - open via multiple papillae either side of the colliculus seminalis
Bulbourethral (Cowpers) glands (paired) - open further caudally.
Nerve and blood supply to the scrotum
Blood supply: external pudendal vessels
Innervation: genitofemoral nerve
Structures passing through the inguinal canal in the adult male
Spermatic cord (incl. cremaster from int abdominal oblique)
Genitofemoral nerve
External pudendal vasculature (-> scrotum)
Efferent lymphatics from superficial inguinal LNs
*In the female, it contains mammary vessels and nerves (ext pudendal) (+ round ligament of the uterus)
Label the image
a - testis
b - head of epididymis
c - body of epididymis
d - tail of epididymus
e - proper ligament of the testis
f - ligament of the tail of the epididymus
g - spermatic cord
h - cremaster mm
i - external inguinal ring
j - vaginal ring
k - visceral vaginal tunic
l - vaginal cavity
m - parietal vaginal tunic
What forms the borders of the internal inguinal ring?
Caudal free border of the internal abdominal oblique cranially
Inguinal ligament (tuber coxa to pre-pubic tendon) caudally
(Rectus abdominis and prepubic tendon ventromedially)
*Medial and lateral borders not well defined
What forms the external/superficial inguinal ring?
A well defined split in the aponeurosis of the external abdominal oblique muscle
By what gestational age should the testes passed into the inguinal canal?
Where are most testicles located at birth?
d270-300
At birth, most testes are located in the inguinal canal; the extra-abdominal portion of the gubernaculum usually resides in the scrotum (may be mistaken for testicles)
By what age does contraction of the vaginal process prevent movement of the testicles to and from the abdomen?
Contracts to approx 1cm within the first few weeks of life
What structures run within the spermatic cord?
1) Vaginal tunic(s)
2) Testicular vessels and lymphatics
3) Ductus/vas deferens
(Cremaster closely associated although not technically a component of the cord as it lies outside the parietal tunic)
Label the parts of the spermatic cord (transverse section)
1 - Testicular aa
2 -Ductus deferens
3 - Pampiniform plexus
4 - Testicular nerves/lymphatics
5 - Mesorchium
6 - Mesoductus
7 - Cremaster
8 - Vaginal cavity
9 - Spermatic fascia
10 - Visceral vaginal tunic
11 - Parietal vaginal tunic
Where does the cremaster mm origonate?
Detachment of the internal abdominal oblique but has acquired an origin of its own from the inguinal ligament
Approximate proportion of left and right cryptorchid testices that are abdominally retained
Approximately 75% of left cryptorchid testicles are abdominal
vs approx 42% of right crypts being abdominal
There is some debate in the literature with some publications finding no significant difference in incidence of abdominal cryptorchidism between left and right sides
What is the difference between inguinal hernia, ruptured inguinal hernia and inguinal rupture?
Inguinal hernia - most common equine inguinal hernia (prev - indirect hernia). Intestine protrudes through the vaginal ring into the inguinal canal.
Ruptured inguinal hernia - inguinal hernia as above but intestine passes through a rent in the parietal tunic/spermatic fascia to lie SQ
Inguinal rupture (prev direct hernia)- intestine protrudes through a rent in the peritoneum & transeverse fascia adjacent to the vaginal ring, such that intestine sits SQ beside the vaginal process
Indications for surgical treatment of congenital inguinl hernias
Failure to resolve spontaneously by 6 months of age
Acute onset incarceration/inability to reduces +/- colic signs
Breeds most likely to be affected by acquired inguinal/scrotal hernias
Which testicle is most commonly affected?
Standardbreds
Draft breed
Andalusians
The left testicle is most frequently affected
What degree of torsion of the spermatic cord is within normal limits?
Up to 180°
Where does fluid/blood accumulation occur with hydrocoele/haematocoele formation?
In the vaginal cavity between the visceral and parietal vaginal tunics
Differential diagnoses for scrotal enlargement (9)
Testicular trauma (breeding injury)
Orchitis
Testicular abscessation/pyocoele
Hydrocoele
Haematocoele
Testicular neoplasia
Congenital or acquired inguinal hernia
Varicocoele (enlargement of the scrotal neck)
Torsion of the spermatic cord >180°
List the types of primary testicular tumours in horses
Germinal
Seminoma, teratoma, teratocarcinoma, embryonic carcinoma
Non-germinal
Sertoli cell tumour, Leydig cell tumour
Whic is the most common equine testicular neoplasm
Which cell type do these origonate from and which group(s) of horses are most commonly affected?
Seminomas
Origonate from geminal cells of the seminiferous tubules
Affect mainly older horses of those with cryptorchid testicles
What is this condition?
Male pseudhermaphrodite (male gonadal tissue and more female like external genitalia)
Typically have hypoplastic testes within the abdomen, and a penis like structure resembling a clitoris, emerging from a rudimentary ‘prepuce’ which may be positioned on midline anywhere between the perimeun or scrotal location. Phenotypic appearance resembles female but sexual behaviour is that of a male
Diagnostic accuracy of palpating the internal inguinal rings per rectum in dx of abdominal crypts
Overall 88%
Inability to palpate the ring(s) indcates abdominal crypt
If the ring is palpable, either the epididymus or testis (or both) has traversed the ring, so either not an abdominal crypt, or a partial abdominal crypt (testis retained, epididymus descended)
Possible complications of testicular biospy
Transient scrotal oedema, intratesticular hemorrhage ( may cause pressure necrosis), immune reaction to spermatozoa caused by disruption of the blood-testis barrier; dissemination of neoplastic cells if a neoplasm is biopsied, formation of a haematoma (negative effect on spermatogenesis)
List 2 methods of testicular biopsy and main advantages and disadvantages of each
1) Aspiration biopsy: + low risk. + Less damaging than needle biopsy
- Usually no useful info re spermatogenesis. Main use is to determine the cause of testicular enlargement
2) Needle biopsy (or Trucut): + Most useful info on spermatogenesis. + Unlikely to have deleterious long term effects on the testes
- More damaging than aspiration biopsy
- More complications
Best location for testicular biopsy
Craniolateral quarter. Less vascular and remote from head of epididymus
What hormonal assays can be done to aid in the dx of crypts?
Which is most accurate?
Testosterone
hCG stim test
Oestrone sulphate
Anti-mullarian hormone; this is the most reliable in animals >2yrs
Testosterone assay for dx of crypts.
Testosterone is<40pg/ml in geldings, >100pg/ml in stallions (often 1000-2000)
Crypts have testosterone between the 2 but significant overlap so not suitable as a definitve dx test
Upto 14% error using basal testosterone alone although false positives are rare
hCG stim test for dx of crypts
Take baseline plasma T then inject w/ 6000-12000IU hCG IV
Take 2nd sample at 1hr/3hrs/24hrs/even ideally 3days
Stallions, T ↑ 4-30 fold, 0-120mins after IV hCG
Geldings, T ↑ 0-2 fold
Cryptorchids ↑ 3 fold
94.6% accurate in predicting the presence of testicular tissue, but response poor in horses less than 18months & in the Winter. Also abdo testes much less rx to hCG stim than scrotal testes
Oestrone sulphate for dx of crypts
86% diagnostic accuracy
NOT useful in donkeys (absence of conjugated E) or horses <3 years
Geldings had estrone sulphate <0.12ng/ml (<50pg/ml)
Animals w/ testic tissue had estrone suphate >1.0ng/ml (>400pg/ml)
AMH for dx of crypts
Cryptorchids have a significantly higher AMH concentration (32.4 +/- 5.0 ng/ml) than intact stallions (14.7 +/- 2.4ng/ml) and geldings (0.07 +/- 0.01ng/ml)
High diagnostic accuracy and single sample required
Dx accuracy of scanning the inguinal region alone for dx location of retained testicles reported by Coomber 2016 EVE
Absence of testis indicates abdo testicle -
Predicted with 98% accuracy for visualising inguinal testis, and 97% accuracy for ID abdo testes with absence of testicle inguinally
What is a varicocoele and how should it be treated?
Abnormally distended/tortuous pampiniform plexus
Treatment is removal of the cord and testis, but often tx NOT REQUIRED esp if semen quality is fine
Treatment for hydrocoeles
ID and remove underlying cause where present (remember to check for peritoneal effusion)
If occurring as a complication of open castration, remove the remaining tunic
Castration of the affected testicle will lessen the negative effect on spermatogenesis of the contralateral unaffected testicle
Px for fertility with bilateral hydrocoeles is guarded although some do retain normal spermatogenesis