ANATOMY - Male Reproductive System Flashcards
What are the three main functions of the male reproductive system?
Gamete/spermatozoa production
Semen production
Androgenic hormone production (testosterone)
What makes up the external male genitalia?
Penis, Prepuce, Scrotum, Testes
What type of penis do canines have?
Musculocavernous
What are the distinguishing features of a musculocavernous penis
Copious cavernous and erectile tissue
What are the four main regions of the penis?
Root, Body, Glans, Os penis
What forms the root and body of the penis?
Two crura which arise from the ischial arches to form the root and then combine to form the body of the penis
What are the two types of cavernous tissue found in the crura?
Corpus cavernosum and Corpus spongiosum
What is the fibrous coat surrounding the cavernous tissue (corpus cavernosum and corpus spongiosum)?
Tunica albuginea
Describe the corpus cavernosum
Corpus cavernosum is distensible, erectile tissue which makes up the majority of the crura
What are the different structures formed from the corpus spongiosum?
The corpus spongiosum enlarges to form the bulb of the penis, a thin vascular sleeve around the penile urethra and then enlarges again to form the glans at the distal end of the corpus cavernosum
Why is the corpus spongiosum more delicate than the corpus cavernosum?
The corpus spongiosum has larger potential blood spaces making the tissue more distensible and thus more delicate
In which animal is the os penis the easiest to see on a radiograph?
Canine (dog)
What is the os penis?
The penile bone located at the distal end of the corpus cavernosum
What is the function of the ventral groove of the canine os penis?
The ventral groove allows the penile urethra to pass through the distal glans of the penis
What is the clinical significance of the ventral groove of the os penis?
Bladder stones tend to get stuck as they can’t pass through the urethra due to the occlusion of the ventral groove
What are the two areas of the canine glans?
Bulbus glandis and Pars longa glandis
Describe where the Bulbus glandis is located in the glans?
The Bulbus glandis is the proximal, expanded region of the glans secured firmly to the os penis
Describe where the Pars longa glandis is located in the glans?
The Pars longa glandis is the distal, cylindrical region of the glans forming the apex of the penis
In which of the glans is the urethral orifice found in the musculocavernous penis?
The urethral orifice is found at the distal end of the Pars longa glandis
What is the prepuce?
An invagination of the abdominal skin which covers the retracted penis
What are the two layers of the prepuce?
Lamina externa
Lamina interna
What is found in the lamina interna of the prepuce?
Smega-secreting preputial glands and lymphoid tissue
Where do the paired preputial muscles which twitch the skin of the prepuce arise from?
Cutaneous trunci muscle
Where is the preputial orifice found in the canine?
The preputial orifice is found caudal to the umbilicus
What is different in the prepuce of neonates?
In neonates, the prepuce and penis are fused together to prevent extrusion of the penis
What is phimosis?
Phimosis is the congenital narrowing of the preputial orifice preventing the extrusion of the penis
What is paraphimosis?
Paraphimosis is the inability to retract the penis
What are some of the causes of paraphimosis?
- Preputial orifice slightly too narrow
- Fur wrapping around the extruded penis creating a stricture
Why is it essential to correct paraphimosis quickly?
Paraphimosis can lead to impaired circulation to the penis
What are the four penile muscles?
Bulbospongiosus
Ischiocavernosus
Ischiourethralis
Retractor penis
Describe where the bulbospongiosus muscle runs within the penis
The bulbospongiosus is a continuation of the urethralis muscle and forms a muscular sleeve around the penile urethra
Describe where the ischiocavernosi muscles run within the penis
The ischiocavernosi are paired muscles which wrap around the crura and attach to the corpus cavernosum
Where does the ischiourethralis muscle arise from?
The ischiourethralis muscle arises from the ischium of the pelvis
Which of the penile muscles is particularly important in the erection process?
Ischiourethralis muscle
Where do the retractor penis muscles arise from?
The retractor penis muscles are paired muscles which arise from the caudal vertebrae, run lateral to the anal canal, along the perineum and attach to the penis at the prepuce
What is the function of the retractor penis muscles?
The function of the retractor penis muscles is to retain the penis within the prepuce
Out of the four penile muscles, which one is made up of mostly smooth muscle?
Retractor penis muscles
What are the nerves which innovate the penile muscles?
Motor, parasympathetic fibres arising from the pelvic nerves
What is the main artery which supplies the penis?
Internal pudendal artery
What is the main artery which supplies the prepuce?
External pudendal artery
What are the three branches of the internal pudendal artery?
Dorsal artery of the penis
Deep artery of the penis
Artery of the bulb
Which region of the penis is supplied by the dorsal artery of the penis?
Glans
Which region of the penis is supplied by the deep artery of the penis?
Corpus cavernosum
Which regions of the penis are supplied by the artery of the bulb?
Corpus spongiosum and the proximal region of the penis
What is the predominant venous drainage route for the penis?
Dorsal vein
Which vein does the dorsal vein drain into?
Internal pudendal vein
Which structures of the penis drain directly into the dorsal vein and into the internal pudendal vein?
Bulbus glandis, Corpus cavenosum, Bulb of the penis
Describe the possible routes of venous drainage for the Pars longa glandis
Pars longa glandis can either drain into the bulbus glandis and into the dorsal vein which drains into the internal pudendal vein, or the Pars longa glandis can drain directly into the external pudendal vein
What are the two structures which prevent venous reflux in the penis?
Valves and the Ischiourethralis ring
What vein is occluded by a fibrous Ischiourethralis ring during erection?
Dorsal vein
What is the first step of erection?
Increased arterial flow into the penis and occlusion of venous outflow due to the valves and the ischiourethralis ring, allowing arterial pressure to be reached in the cavernous spaces
What is the second step of erection?
Rhythmic contractions of the bulbospongiosus and ischiocavernosus muscles squeeze more blood into the cavernous spaces to reach above arterial pressure
Describe the ‘tie’ which occurs in dogs during copulation
Further occlusion of venous drainage causes the bulbus glandis to remain swollen, ‘tying’ the penis with the vulva to keep the semen secure within the female to increases the chances of fertilisation
What is the main function of the scrotum?
Thermoregulation of the testes to allow for optimal testicular production
What is the position of the scrotum in the dog and the cat?
Dog: intermediate position
Cat: perineal position
What are the external features of the scrotum
The external scrotum is a thin skin with copious sweat and sebaceous glands
What is the unique feature that can be seen on the cranial external face of the ruminant scrotum?
Rudimentary teats can be seen on the cranial external face of the ruminant scrotum
What are the internal features of the scrotum?
The internal features of the scrotum consist of the testes, fasia lining and dartos which are closely adhered to the scrotal skin
What is the dartos?
The dartos is a thermoregulatory fibromuscular layer of the scrotum
What is the vaginal tunic?
The vaginal tunic is an outpouching of parietal peritoneum through the inguinal canal
What are the two layers of the vaginal tunic?
Parietal outer layer
Visceral inner layer
What is the clinical significance of the fluid filled space between the parietal outer layer and visceral inner layer of the vaginal tunic?
This fluid filled space is directly connected to the peritoneal cavity and if strict preparation and asepsis is not used during castration surgery, this can be a direct route for infection and peritonitis
What is the inguinal canal?
The inguinal canal is the slit between the abdominal muscles made up of the superficial and deep inguinal ring
What is the function of the inguinal canal in males?
The vaginal tunic and external pudendal vessels pass through the inguinal canal
What is clinically significant about the size of the inguinal canal in the stallion
The inguinal canal of the stallion is to wide that there is a risk of abdominal herniation through the inguinal canal
What type of penis does the feline have?
Musculocavernous
Where is the feline penis located?
The feline penis is located caudoventrally with the preputial orifice facing caudoventrally
Where is the groove of the os penis located in the feline compared to the canine os penis?
On the dorsal surface of the feline os penis compared to on the ventral surface of the canine penis
What is the unique secondary sexual characteristic that develops on the glans of the feline penis?
The glans of the feline penis develop small keratinised spines on the surface
What is the function of the keratinised spines on the surface of the feline glans?
To induce ovulation in the queen (female cat)
What type of penis does the stallion have?
Musculocavernous
What are the three regions of the glans of the stallion penis?
Collum glandis
Corona glandis
Dorsal process extending over the corpus cavernosum
Where is the urethral orifice located in the stallion?
The urethral orifice is located at the end of the corona glandis within the urethral sinus of the fossa glandis
What is the clinical significance of the urethral sinus and fossa glandis of the stallion glans?
The urethral sinus and the fossa glandis is a blind ending pocket which can accumulate smega and harbour bacteria which can cause infection and infertility
Describe the two parts of the stallion prepuce
Preputial orifice: the opening to the outer layer of the prepuce
Preputial ring: the opening to the inner layer of the prepuce
In which orientation do the stallion testes lie within the scrotum?
Horizontal orientation
What type of penis do ruminants have (bull, ram and billy goat)?
Fibroelastic penis
What is the distinguishing anatomical feature of the fibroelastic penis?
Sigmoid flexure
(T/F) The penis of ruminant neonates does not have a sigmoid flexure
TRUE
Which features of the fibroelastic penis allow more rapid erection?
There are small blood spaces in the cavernous tissue as well as copious fibroelastic tissue which remains rigid even when the penis isn’t erect, allowing for a more rapid erection with less blood required. The sigmoid flexure also allows for more rapid extension
Where do the retractor penis muscles attach to on the fibroelastic penis?
The paired retractor penis muscles attach to the second bend of the sigmoid flexure
What is the function of the retractor penis muscles in regards to the fibroelastic penis?
The retractor penis muscles maintain the bend of the sigmoid flexure when the penis is flaccid
Other than the size, how would it be possible to differentiate a bull penis from a ram or billy goat penis?
In the ram and the billy goats, there is a distinctive urethral process which extends cranial to the glans
What type of penis does the boar have?
Fibroelastic
What is unique about the shape of the boar penis?
The shaft of the boar penis twists one full anticlockwise turn and there is another anticlockwise turn at the apex of the penis
How does the number of anticlockwise turns change when the boar penis is erect?
When the boar penis is erect, there are six anticlockwise turns
What is the unique structure present on the dorsal surface of the cranial end of the boar prepuce?
Preputial diverticulum
What is the function of the preputial diverticulum?
The preputial diverticulum is involved in pheromone production and distribution
What is the clinical significance of the preputial diverticulum?
The preputial diverticulum can become infected and resemble an umbilical hernia
What is the main function of the testes?
Gamete/spermatozoa production
At what temperature do the testes achieve optimal testicular production?
3°C below body temperature
What can commonly affect ram fertility?
Rams can often have a thick covering of wool over the scrotum which can affect the thermoregulation of the testes and thus result in fertility issues
What is the outer capsule of the testis called?
Tunica albuginea
What can be obviously seen on the surface of the tunica albuginea of the ruminant testes?
The tunica albuginea of the ruminant testes has very tortuous vessels seen on the surface
What can be obviously seen on the surface of the tunica albuginea of the boar testes?
The tunica albuginea of the boar testes has linear vessels seen on the surface
What makes up the parenchyma contained within the tunica albuginea of the testis?
Interstitium which supports the seminiferous tubules
What causes the lobules seen in the testicular parenchyma?
The lobules are caused by invaginations of the tunica albuginea
What is contained within the central mediastinum running through the centre of the testicular parenchyma?
Rete testis
(T/F) There is no visible mediastinum in the stallion testes
TRUE
What is the function of the rete testis?
Rete testis is the collecting point for sperm as they leave the seminiferous tubules
What is the function of the epididymus?
The epididymus allows the storage and maturation of sperm
Describe where the sperm travels from the rete testis to the vas deferens
Sperm exits the rete testis via small efferent ductiles which combine to form the epididymal tract which runs through the epididymus, exiting as the tail of the epididymus to form the vas deferens
Which regions of the epididymis are tightly connected to the testis and which region is free?
The head and the tail of the epididymis are tightly connected to the testis whereas the body of the epididymus is free
What is the name of the space between the body of the epididymus and the testes?
Testicular bursa
What are the three testicular ligaments?
Proper ligament
Ligament tail of the epididymus
Scrotal ligament
Which of the testicular ligaments attaches the tail of the epididymus to the testis?
Proper ligament
Which of the testicular ligaments attaches the tail of the epididymus to the parietal layer of the vaginal tunic?
Ligament tail of the epididymis
Which of the testicular ligaments attaches the vaginal tunic to the scrotum?
Scrotal ligament
Which testicular ligament is usually broken down during a castration?
Scrotal ligament
What are the structures that make up the spermatic cord?
Vas deferens
Deferential artery and vein
Testicular artery and vein
Lymphatics
Sympathetic testicular nerves
Why might it be difficult to palpate the spermatic cord in small ruminants?
Due to the deposition of ‘cod fat’ around the spermatic cord
What is the function of the vas deferens?
Vas deferens carries sperm to the prostate urethra
Which artery is the testicular artery a branch of?
Abdominal aorta
What is the function of the pampiniform plexus of the testicular vein?
The pampiniform plexus of the testicular vein wraps around the distal convoluted testicular artery to allow heat exchange between the vessels. The venous blood cools the arterial blood so the blood entering the testis is below body temperature to allow for optimal testicular production
Which vein does the testicular vein drain into?
Caudal vena cava
What is the function of the cremaster muscle?
The cremaster muscle acts as a thermoregulatory mechanism as when it contracts, the testes are drawn closer to the abdominal wall to increase testicular heat
From which muscle does the cremaster muscle originate?
Internal abdominal oblique muscle
What is the structure responsible for testicular descent?
Gubernaculum
What are the three layers of the gubernaculum?
Pars propria
Pars vaginalis
Pars infravaginalis
Describe how the gubernaculum allows testicular descent
The shortening and the swelling of the gubernaculum opens the inguinal canal wide enough to draw the testis into the scrotum
What is cryptorchidism?
The uni or bilateral failure of testicular descent
In animals with cryptorchidism, where in the body is the testis most likely to be found?
Near the inguinal canal
What are the main risks of cryptorchidism
Infertility and increased chances of malignant neoplasia
Why is it not always abnormal to see temporary cryptorchidism in the stallion?
In the stallion there is marked, temporary enlargement of the foetal testes during gestation which can delay testicular descent
What are the two regions of the urethra?
Pelvic urethra
Penile urethra
What is the best way to image the urethra using diagnostic imaging?
Contrast radiography
Where in the ruminant is there commonly bladder stone obstructions?
There are commonly bladder stone obstructions in the region of the sigmoid flexure of the penis due to the constriction of the urethra in this area
What is the function of the accessory reproductive glands?
Seminal fluid production
What are the accessory glands found in dogs?
Ampullary glands
Prostate gland
What are the accessory glands found in cats?
Bulbourethral glands
Prostate gland
Which of the accessory reproductive glands produces the most seminal fluid in carnivores?
Prostate gland
What are the accessory glands found in stallions, ruminants and boars?
Prostate gland
Vesicular glands
Bulbourethral glands
Ampullary glands
Which of the accessory reproductive glands produces the most seminal fluid in the stallion?
Vesicular glands
Describe how the bi-lobed structure of the prostate gland differs in dogs and cats
In dogs, the bi-lobed structure of the prostate completely encloses the proximal urethra, however in cats, the bi-lobed structure of the prostate only covers the dorsal surface
Which artery supplies the prostate gland?
Prostatic artery
Which artery does the prostatic artery branch from?
Internal pudendal artery
What is the most common cause of prostatic enlargement (prostamegaly)?
Benign prostatic hyperplasia
What are some of the consequences of prostamegaly?
Compression of the urethra and/or rectum causing tenesmus and constipation
Other than benign prostatic hyperplasia, what are some of the other causes of prostamegaly?
Prostatitis (inflammation)
Prostatic tumours
Cystic disease
What is the best way to image the prostate using diagnostic imaging?
Ultrasound (however prostamegaly can be seen on a radiograph)
What is the best way to image the testis using diagnostic imaging?
Ultrasound
