Lecture 2

What is the primary function of the male reproductive system?

Production and maturation of gametes (spermatozoa), transport of gametes to the female tract for fertilization, and production of hormones.

What are the gonads in the male anatomy and their function?

The testes, which are responsible for the production of spermatozoa and hormones.

What are the gonadal ducts and what is their funvtion

epididymis & ductus deferens→ transport, maturation & storage of spermatozoa

What is the role of the urethra in the male anatomy?

It is a single duct that is continued from the urinary system

What do accessory glands do in the male reproductive system?

They produce the bulk of ejaculate (semen) and provide a medium to assist with transport, deposition, and fertilization and also produce seminal plasma

What is the function of the penis

facilitates deposition of semen into female tract

What is the function of the scrotum?

It acts as a thermosensor, swamp cooler, and provides protection and support for the testes.

What does the scrotum contain

Testes, epididymides and spermatic cords

Describe the structure of the scrotum

Contains two cavities which are separated by the scrotal septum which is indicated on the surface by the scrotal raphe. Each side comprises a narrow neck proximally (containing the spermatic cord) and a broad base distally (containing the testis and epididymis), with the cavities containing fluid

What are the 5 layers of the scrotal wall from outer to inner

Scrotal skin → tunica dartos → scrotal fascia → parietal vaginal tunic → visceral vaginal tunic 

What is the function of the scrotal skin and describe its structure

It is heavily populated with sweat glands and Forces the scrotum to sweat through evaporative heat transfer → acts as swamp cooler

What is the function of the tunica dartos and describe its structure

A mesh-like smooth muscle layer that lies just beneath the scrotal skin AND initiates contractions/relaxations in response to changes in scrotal skin temperature

What is the location and orientation of the testes in different species?

• dorsal in small animals

• between the thighs and vertical in ruminants

• between the thighs and horizontal in horses

• close to the anus and oblique in pigs

Describe the outer layer structures of the testes

Covered by the serosal visceral vaginal tunic → capsule/tunica albuginea layer

What is the tunica albuginea ? 

dense irregular fibrous connective tissue which sends finger-like projections into the parenchyma of the testicle and contains a vascular layer called the tunica vasculosa

What divides the parenchyma into lobules in the testes?

Connective tissue septa (or trabeculae) which arise from the inner surface of the capsule

What does the testicular parenchyma comprise of?

The testicular parenchyma consists of seminiferous tubules and interstitial endocrine cells

What are the two compartments of the testes? 

Tubular compartment and interstitial compartment.

What are the seminiferous tubules?

Highly convoluted loops which attach to the canals of the rete testis. Each loop of a seminiferous tubule is composed of a convoluted portion (tubulus contortus) and a straight portion (rectus) that join the rete tubule

What is the tubulus contortus function

The tubulus contortus serves as the site of spermatogenesis.

What is the role of the interstitial endocrine cells

They produce androgens

What is the mediastinum of the testis

A concentration of connective tissue which contains the network of canals called the rete testis

What is the role of the rete testis

These connect the germinal or seminiferous tubules of the testicular parenchyma with the initial ducts of the epididymis at the cranial pole of the testis and allows the spermatozoa to be transported out of the testes

What makes up the excurrent duct system

The excurrent duct system consists of the efferent ductules, epididymis, and ductus deferens

What is the function of the efferent ducutules

Convey newly formed spermatozoa and tubular fluid (rete fluid) into the epididymal duct

What are the functions of the epididymis?

It stores spermatozoa, matures spermatozoa, and produces seminal plasma.

What is the function of the smooth muscle surrounding the epididymus

The muscular layer is responsible for rhythmic contractions, forcing spermatozoa to travel along its course to the tail

What is the epididymal transit time

The pathway of spermatozoa from the head to the tail

Describe the structure and role of the epididymus head

The head has a proximal and distal part

• The proximal head reabsorbs a significant amount of rete fluid

• The distal head secretes fluid into the lumen of the epididymal duct.

What is the name of the ligament attached to the tail of the epididymus to the caudal pole of the testis

The proper testicular ligament.

What is the name of the ligament attached to the tail of the epididymus to the scrotal wall

Ligament of the tail of the epididymus

What is the movement of the cytoplasmic drop on spermatozoa as it passes through the epididymus

it has a proximal cytoplasmic droplet → as it travels down the duct, the droplets move further down the tail

What is the ductus deferens and its structural pathway

The continuation of the tail of the epididymus and is a thin fibromuscular tube which passes cranially along the dorsomedial border of the testes then continues dorsally in the spermatic cord before entering the abdominal cavity through the inguinal canal

What is the name of the distal expansion of the ductus deferens (where present)

Ampulla

What is the mesoductus deferens

A mesentery which anchors the ductus to the abdominal wall 

What is the mesorchium 

The mesentery support of the testis which carries the testicular vessels through the inguinal canal (from the abdomen) and into the scrotal cavity

What is the spermatic cord and its structural pathway

A composite structure comprising the ductus deferens, testicular vessels and nerves and the cremaster muscle. The cord extends from the deep inguinal ring to the dorsal pole of the testis

What is the cremaster muscle and its role

The primary striated muscle which supports the testes and is continuous with the internal abdominal olbique muscle and attaches to the parietal visceral tunic. It helps support the testis and aids in the control of testicular temperature.

Describe the vascular structures of the testes and the function it has

The testicular vessels adopt a special form within the spermatic cord in that the testicular artery which winds through an extensive venous plexus (the pampiniform plexus) formed by the testicular vein

• The artery is derived from the aorta

• The vein runs into the caudal vena cava

The pampiniform plexus faciltiates counter-current heat exchange where arterial blood is cooled by venous blood 

Where would you find the ampulla accessory gland?

in the terminal portion of each deferent duct

Which species have an ampulla

Horses, bulls and dogs

Where would you find the vesicular accessory glands

Located within the genital fold lateral to the ductus deferens of either side and dorsocranial to the pelvic urethra

Which species do NOT have vesicular glands

Carnivores

Where would you find the prostate gland 

it lies between the pelvic urethra and bladder

What are the two structural forms of the prostate glands

1. Corpus prostate in which the prostate is outside of the urethralis muscle and is visible as a heart-shaped (boar), or an H-shaped (stallion) structure

2. Disseminate prostate in which glandular tissue is distributed along the dorsal and lateral walls of the pelvic urethra.

What are the species differences in prostate glands?

• In the dog it is the main accessory sex gland and only has the corpus prostate

• Stallions have no disseminate prostate, only corpus prostate which is lobulated

• In the tom, the prostate consists of four lobes that are dorsal to the pelvic urethra.

• Boar has both

• Rams only have disseminate prostates

Where are the bulbourethal glands/cowper’s glands 

On either side of the pelvic urethra near the ischial arch

What are the species differences betwen the cowper’s glands

• In the ram, bull and stallion, these glands are small and buried under the bulbospongiosus muscle.

• The boar they are very large and dense and lie on the surface of the caudal two-thirds of the pelvic urethra.

• They are small in cats

• Absent in dogs

Why are cowper’s glands important

They produce a viscous secretion that provides the gel fraction of the ejaculate and causes the seminal plasma to coagulate following ejaculation

What structure holds the penis during quiescence

The prepuce 

What is the name of the structure which forms smega in horses

Urethral fossa

What is special about the pig, ox and cat glans penis

• Pig and ox have a spiralling twist at the free extremity of the penis

• Cat has keratinised barbs covering the glans surface and penile spines

What is the corpus cavernosum

Erectile tissue which are firmly attached to the ischiatic arch and form part of the root of the penis

What is the urethral groove

The ventral surface of the corpus cavernosum within the body of the penis which is longitudinally grooved

What are the 2 main penis types

1. Fibroelastic = little erectile tissue and contains mostly fibrous and elastic connective tissue

2. Musculocavernosus = abundant erectile tissue with more smooth muscle

What is special about the fibroelastic penis

It has an S shaped bend or sigmod flexure when quiescent

Which species have which type of penis

Fibroelastic penis is found in ruminants and pigs, while musculocavernosus penis is typical in horses and carnivores

What is the os penis

The ossified extremity of the corpus cavernosum

What are the two regions of the corpus cavernosum tissue in dogs

The bulbus glandis and pars longa glandis 

What is the corpus spongiosum

A sleeve of erectile tissue with a connective tissue capsule (tunica albuginea) surrounding erectile tissue, which in turn envelopes the penile urethra

What are the 4 main muscles of the penis and their relative function

1. Urethralis muscle → moves seminal plasma and spermatozoa into the urethra

2. Ischiocavernosus muscle → contraction elevates the erect penis

3. Bulbospongiosus muscle → envelops the corpus spongiosum at the bulb of the penis

4. Retractor penis muscle → retracts the penis back into the prepuce

What is the main blood supply of the penis ? 

They are branches of the internal pudendal muscles and consists of:

1. Artery of bulb

2. Deep artery of penis

3. dorsal artery of penis