REPRODUCTIVE SYSTEM OF FEMALE RABBIT

Published in Zoology
Sunday, 28 May 2017 23:04
The female reproductive organs include a pair of ovaries, a pair of oviducts, a pair of uteri, vagina, vestibule, clitoris and some accessory glands.
 
1. OVARIES
 
  • The two ovaries are small, whitish, oval bodies, about 2 cm long.
  • They are found behind the kidneys, each ovary attached to the dorsal abdominal wall by a double fold of peritoneum called mesovarium.
  • From the surface of ovaries project several blister-like, small, rounded, semitransparent projections, called ovarian or Graafian follicles, each containing a developing ovum.
  • Histologically, the section of a rabbit ovary shows a peripheral layer of germinal epithelial cells surrounding a dense mass of connective tissue fibres, called stroma, containing blood andlymph vessels and nerve.
  • Stroma contains groups of actively dividng germinal cells, called follicle in various stages of development.
  • In each follicle, a single cell enlarges firswhile others surround and nourish it. It ultimately beomes oocyte orovum.
  • The mass of cells around oocyte is known as discusproligerous.
  • When ripe, the follicles are known as Graafian follicles, which project from thesurface of ovary as minute bumps.
  • Each graafian follicle contains a large fluid - filled follicular cavity.
  • The cells lining the cavity are termed membrana granulosa.
  • The fully mature oocyte is surrounded by a thick transparent membrane called zona pellucida containing yolk and fat droplets.
  • It is covered by another striated layer ot columnar cells, called corona radiata.
  • In the stroma there are also found groups of interstitial cells which produce sex hormones (oestrogen).
  • Eventually each mature follicle bursts to liberate the oocyte into body cavity, a process known as ovulation.
  • The follicular cells remaining behind divide rapidly to form a yellowish solid mass of cells called corpus luteum.
  • During pregnancy it serves as a temporary endocrine gland secreting a hormone (progesterone).
  • It causes uterus to enlarge to receive the growing foetus and stimulates lactation.
  • If ovum is not fertilized, corpus luteum gradually disappears leaving a scar called corpus albicans.
 
2. OVIDUCTS
 
  • Each oviduct opens anteriorly, close to the outer border of the ovary of its side, by a wide funnel called fallopian or oviducal funnel.
  • The opening of funnel, or ostium, is provided with many cilia to receive the minute ova released from the ovary.
  • Funnel leads into the upper part of oviduct. It is a short, narrow, coiled and internally ciliated duct called fallopian tube. Ova pass. through this tube by ciliary action and fertilization also occurs here.
  • The fallopian tube is followed by a much wider, longer convoluted, thick walled muscular tube the uterus.
  • It is richly vascular and highly distensible and attached to the dorsal abdominal wall by a mesentery.
  • Fertilized ova or zygotes get implanted on the uterine wall to develop into embryos or foetuses, each attached to the placenta by an umbilical cord.
 
3. VAGINA AND VESTIBULA
 
  • The uteri of both the sides meet into a long wide, median duct, the vagina, lying dorsally upon the urinary bladder.
  • It opens posteriorly into the neck of bladder to join the urethra forming a short narrow common urinogenital canal or vestibule.
  • It runs backwards ventral to the rectum and opens to the exterior by a slit-like aperture, the vulva.
  • The vagina serves to receive the penis of the male during copulation.
 
4. CLITORIS
 
  • From the anterior wall of vulva projects a small erectile knob-like clitoris.
  • It is regarded homologous with the male penis since it contains a pair of erectile tissue, the corpora cavernosa.
  • But the urethra does not pass through the clitoris.
 
5. ACCESSSORY GLANDS
 
  • In the female rabbit, there is no prostate gland.
  • A pair of small Bartholin’s glands or Cowper’s glands lies embedded in the dorsal wall of vestibule.
  • Their viscid secretion lubricates the vaginal passage. The perineal and rectal glands are as in the male.

REPRODUCTIVE SYSTEM OF MALE RABBIT

Published in Zoology
Sunday, 28 May 2017 22:08
In rabbit 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 epididymes, a pair of vasa deferentia, urethra, penis and some accessory glands.
 
1. TESTES
 
  • The paired testes are small, ovoid bodies of light pink colour.
  • 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 foetus and new born rabbit, the testes lie within the abdominal cavity near 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 throught life.
  • But in rabbit, rat 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 throught life.
  • The reason for this is spermatozoa can develop within the scrotalsacs at low temperature but cannot develop inside abdomen at normal temperature.
 
testis ls rabbit thumb1
 
  • Histologically, the mammalian testis is composed of a number of wedge-shaped or cone-shaped compartments or locules.
  • The outer protective covering of testis, the tunica aibuginea, 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.

 

sperm structure thumb1

 

  • 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 the 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 testis are transferred through vasa efferentia into the epididymis.

2. EPIDIDYMIS
 
  • 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.
 
A. CAPUT EPIDIDYMIS
 
  • It is the head or anterior part which 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, spermatic vein and a nerve.
  • The vein forms an extensive capillary network round the artery called the pampiniform plexus.
 
B. CAUDA APIDIDYMI
 
  • It is the tail or posterior part which 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.
 
C. CORPUS EOHLIDYMIS
 
  • It is the narrow body or middle part connecting the caput and the cauda epididymis.
 
3. VASA DEFERENTIA
 
  • 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, traverses the inguinal canal to enterthe abdominal cavity.
  • It loops ventrally under the ureter and opens dorsally into urethra immediately in front of the opening of the ureter.
  • A small slightly bifurcated blindsac, uterus masculinus or seminal vesicle, opens dorsally into urethra just dorsal to the openings of vasa deferentia.
 
4. 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 called the urinogenital duct.
  • It traverses and opens at the tip of the penis as the male urinogenital aperture.
 
5. 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 exitement to produce erection of penis.
  • Surrounding the urethra is corpus spongiosum above which lie 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 sperms into the vagina of the female during sexual intercourse.
  • The operation of circumcision is the removal of the prepuce.

6. ACCESSORY SEX GLANDS
 
  • Several accessory sex glands open into urethra of male.
  • Their secretions, together with those of epididymes and uterus masculinus, constitute the seminal fluid or semen.
 
A. PROSTATE GLAND
 
  • A large prostate gland lies dorsally around the base of uterus masculinus.
  • It opens into urethra by several small ducts. Its whitish alkaline secretion activates the passive spermatozoa.

B. COWPER GLAND
 
  • A pair of Cowper's glands lie posteriorly to the prostate glands dorsally at the base of penis.
  • Their secretion neutralizes acidity for the protection of spermatozoa.
 
C. 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 anus.
  • Their odorous secretion gives the rabbit its characteristic smell.

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