Reproductive System of Rabbit (Male)

The male reproductive system of a rabbit is a complex and fascinating anatomical structure that plays a crucial role in the perpetuation of the species. Understanding the intricacies of this system is not only of great importance to breeders but also to those interested in the broader field of biology.

Anatomy of the Male Reproductive System

The male rabbit, also known as a buck, possesses a reproductive system that consists of several key components. These include the testes, epididymis, vas deferens, and accessory glands.

In rabbits, the sexes are separate i.e. unisexual and sexual dimorphism is well marked. The male reproductive organs include a pair of testes, a pair of epididymis, a pair of vasa deferentia, a urethra, a penis and some accessory glands.

Testes

The testes are the primary reproductive organs in a male rabbit. They are responsible for producing sperm, the male gametes, and testosterone, the hormone that influences male characteristics and behavior. These almond-shaped organs are located within the scrotum, which is a sac-like structure hanging outside the body. The scrotum helps regulate the temperature of the testes, as sperm production is most efficient at slightly lower temperatures than the rabbit's core body temperature.

• The paired testes are small, ovoid bodies of light pink color.
• Each testes lies in a special thin-walled sac of hairy skin outside the abdominal cavity, called the scrotum.
• It is located ventrally in the pubic region.
• In the fetus and newborn rabbit, the testes lie within the abdominal cavity near the kidneys where they were developed.
• But at puberty, they descend through inguinal canals into scrotal sacs.
• In most species of mammals, the testes remain within scrotal sacs throughout life.
• But in rabbits, rats, and other rodents, they are migratory. They descend into the scrotum during the breeding season but withdraw into the abdominal cavity during non-breeding periods through inguinal canals which remain open throughout life.
• The reason for this is spermatozoa can develop within the scrotal sacs at low temperatures but cannot develop inside the abdomen at normal temperatures.

• Histologically, the mammalian testis is composed of a number of wedge-shaped or cone-shaped compartments or locules.
• The outer protective covering of the testis, the tunica albuginea, is a tough capsule made of white fibrous connective tissue, which projects inwards forming interlobular septa.
• Each lobule contains long, slender, much convoluted microscopic seminiferous tubules bound together by connective tissue.
• The germinal epithelium lining of the tubule is made of two kinds of cells.
• The most numerous are the smaller spermatogenic cells which undergo spermatogenesis to produce spermatozoa.

• A few larger, tall, columnar supporting cells, called Sertoli cells, nourish the sperm cells before they leave the tubule.
• Each sperm consists of a head composed mainly of the nucleus, and a long cytoplasmic tail.
• In the connective tissue between the seminiferous tubules lie scattered interstitial cells or the cells of Leydig which are endocrine in function.
• All the seminiferous tubules in each testis open into a network called rete testis.
• It opens by several fine ductules lined by cilia, called vasa efferentia, into the epididymis.
• The spermatozoa produced by the testis are transferred through vasa efferentia into the epididymis.

Epididymis

Connected to each testicle is the epididymis, a tightly coiled tube responsible for the storage and maturation of sperm. Sperm produced in the testes are transported to the epididymis, where they gain the ability to fertilize an egg. The epididymis is a crucial intermediary between the testes and the vas deferens.

• The epididymis is an irregular, narrow, and highly convoluted tubule of great length.
• It forms a compact ridge-like mass all along the inner surface of the testis.
• The epididymis has three distinct parts.

Caput Epididymis

• It is the head or anterior part that is connected with the anterior end of the testis through vasa efferentia. It lies buried in the fat body.
• It is also connected with the dorsal abdominal wall by a spermatic duct consisting of connective tissue spermatic artery, a spermatic vein, and a nerve.
• The vein forms an extensive capillary network around the artery called the pampiniform plexus.

Cauda Apididmi

• It is the tail or posterior part that connects the posterior end of the testis to the scrotal sac by a thick elastic cord of connective tissue, called the gubernaculum.
• When it shortens, it draws the testis into the scrotal sac.

Corpus Eohilidymis

• It is the narrow-body or middle part connecting the caput and the cauda epididymis.

Vasa Deferentia

The vas deferens, also known as the ductus deferens, is a long muscular tube that extends from the epididymis to the urethra. Its primary function is to transport mature sperm from the epididymis to the urethra, where it mixes with seminal fluids produced by the accessory glands.

• The basal end of each epididymis (cauda epididymis) leads into a yellowish-white, straight, and muscular tube, the sperm duct or vas deferens.
• It runs forward along the inner side of the scrotal sac and traverses the inguinal canal to enter the abdominal cavity.
• It loops ventrally under the ureter and opens dorsally into the urethra immediately in front of the opening of the ureter.
• A small slightly bifurcated blindsac, uterus masculinus or seminal vesicle, opens dorsally into the urethra just dorsal to the openings of vasa deferentia.

Urethra

• The neck of the urinary bladder and the vasa deferentia open into a thick-walled muscular duct, the urethra. It is the common passage for both urine and semen and is called the urinogenital duct.
• It traverses and opens at the tip of the penis as the male urinogenital aperture.

Penis

• The copulatory organ or penis is a small, cylindrical, and erectile organ in front of the anus.
• It is composed of three longitudinal columns of spongy erectile tissue, which become filled with blood during sexual excitement to produce an erection of the penis.
• Surrounding the urethra is the corpus spongiosum above which lies the two corpora cavernosa.
• The penis is enclosed in a sheath of skin which hangs loosely as a fold over its cap-like tip known as prepuce.
• The penis serves to transmit sperm into the vagina of the female during sexual intercourse.
• The operation of circumcision is the removal of the prepuce.

Accessory Sex Glands

The male rabbit's reproductive system includes several accessory glands, including the seminal vesicles, prostate gland, and bulbourethral glands. These glands produce seminal fluids that nourish and transport sperm during ejaculation. These fluids also play a role in neutralizing the acidity of the female reproductive tract, ensuring the survival of sperm on their journey to fertilize an egg.

• Several accessory sex glands open into the urethra of males.
• Their secretions, together with those of epididymis and uterus masculinus, constitute the seminal fluid or semen.

Prostate Gland

• A large prostate gland lies dorsally around the base of the uterus masculinus.
• It opens into the urethra by several small ducts. Its whitish alkaline secretion activates the passive spermatozoa.

Cower Gland

• A pair of Cowper's glands lie posteriorly to the prostate glands dorsally at the base of the penis.
• Their secretion neutralizes acidity for the protection of spermatozoa.

Perineal Glands

• These are a pair of dark elongated scent glands lying behind the Cowper's glands.
• As mentioned earlier, they open into the hairless perineal depressions one on either side of the anus.
• Their odorous secretion gives the rabbit its characteristic smell.

Rectal Glands

• A pair of rectal glands of unknown function is situated dorsally on the rectum.

Reproduction and Behavior

Understanding the male rabbit's reproductive behavior is crucial for successful breeding. Bucks are known for their territorial and sometimes aggressive nature, especially during the breeding season. It's essential to introduce the female, or doe, to the buck's territory to facilitate mating.

In conclusion, the male reproductive system of a rabbit is an intricate and finely tuned system responsible for ensuring the survival of the species. Its various components work in harmony to produce and deliver sperm, ultimately leading to the continuation of rabbit populations. A deep understanding of this system is vital for breeders and researchers alike, contributing to the broader field of biology.