INTRODUCTION :
To continue its own race, an organism by the process of reproduction, produces off springs like its own.
In sexual reproduction the organisms produce male and female gametes which on combining, develop into a new individual. The formation of gametes takes place in the reproductive organs.
PRIMARY SEX ORGAN :
Essential organs which form the gametes. In males, the gamete forming organs are the testes. In females, the corresponding organs are ovaries.
The male gametes is the spermatozoan.
The female gamete is the ovum.
SECONDARY SEX ORGAN :
These form the passage for the gametes to help the union of male & female gametes.
In male this include epididymis, vas deferens, seminal vesicles, prostate, bulbourethral glands & penis.
While in female - Fallopian tube, uterus & vagina. (Breast is an accessory sex organ)
DEVELOPMENT OF SEX ORGAN :
During intra uterine life (IUL) testis & ovary develop from mesoderm. They develop in abdominal cavity in IUL, at the time of birth, testes descend down into scrotal sac but ovaries remain in abdominal cavity.
MALE REPRODUCTIVE SYSTEM
¶ In man, one pair of testes are the main or primary reproductive organ. Size 4-5 cm × 2-3 cm
¶ Both testes are located in a small bag like structure situated below & out side the abdominal cavity called as scrotum or scrotal sac. The temperature of scrotum is 2 to 3°C lesser than body temperature.
¶ Internally scrotum is lined by dartos muscle & spermatic fascia.
¶ Dartos muscle helps in regulation of the temperature with in the scrotum during cold season, It becomes contracted in cold & during warm season, it becomes relaxed.
Cremaster muscles line inside the wall of scrotal & inguinal canal region and help in elevation of testes.
¶ Each testis is attached to the walls of the scrotal-sac through flexible, elastic fibres. This group of fibres is called Gubernaculum or Mesorchium.
¶ Each testis is attached to the dorsal body wall of the abdominal-cavity through a cord termed as the Spermatic cord. This cord is made up of elastin fibres & spermatic fascia. The contents of cord are vas deferens, gonadal veins, gonadal arteries, nerves and lymphatics.
During embryonic stage, testes develop in abdominal cavity & they descend to reach the scrotum at the time of birth. When the testes does not descend to reach the scrotum but remain in abdominal cavity at the time of birth this conditions is called undescended testes or cryptorchidism. Such testis can not develop and function properly and may develop malignancy.
Orchiopexy : When the undescended testes are brought into scrotal sac by surgical process during childhood this process called as orchiopexy.
Castration : Crushing of testes in bulls to convert them to bullocks. (This makes them more obidient due to fall in the level of testosterone)
¶ In some animals the testes descend into the scrotum only in the breeding-season. e.g. Order Chiroptera Order Rodentia
¶ Testes of some animals are permanently placed in the abdominal-cavity. Their scrotum is vestigial-organ.e.g.
Prototherians, animals of the order Edentata (Pangolin, Sloth)
Order Proboscida (Elephant)
Order Sirenia and Order Cetacea
¶ Each scrotum is connected to the abdominal cavity through a passage termed as inguinal-canal. Through this canal the testes descend down into the scrotal-sacs at the time of birth.
¶ Spermatic cord in males passes through the inguinal canal.
Sometimes the inguinal canal may tear leading to abnormal protrusion of abdominal contents like loops of intestine into the inguinal canal. This condition is called as inguinal hernia.
Internal Structure of Testis :
Testis is covered by three coats. Outer most is tunica vaginalis. Middle coat is tunica albuginea & inner most is tunica vasculosa.
Tunica vaginalis has a parietal & visceral layer. It covers the whole testis except it's posterior border from where the testicular vessels & nerves enter the testis.
The Tunica albuginea is a dense, white fibrous coat covering the testis all around . The posterior border tunica albuginea is thickened to form vertical septum called the Mediastinum testis.
Tunica vasculosa is the inner most vascular coat of the testis lining testicular lobules.
¶ Each lobules has 2 to 3 seminiferous tubules, which join together at the apices of the lobules to form straight tubules or tubulirecti which enter the mediastinum. Here they form a network of tubules called as rete testis.
Rete testis fuse to form 10 to 20 efferent ductule called as vasa efferentia or ductuli efferentes. These ductules come out from upper dorsal surface of testis & open into common tubules, which get highly coiled to form epididymis or ductus epididymis. This epididymis is responsible for functional maturation of sperm.
¶ Total number of seminiferous tubules in each testis is about 750 to 1000.
¶ In rabbit, epididymis is 3 m long and in man it is 6 m in length.
Epididymis has 3 parts :
(i) Upper, highly coiled part - Caput epididymis or Globus-major
(ii) Middle part - Corpus epididymis
(iii) Basal, least coiled part - Cauda epididymis or Globus minor
Cauda-epididymis, enters inside the abdominal-cavity from the scrotal-sac in the form of Vas deferens or ductus deferens. Terminal dilated part of vas deferens are called ampulla. Vas deferens and Epididymis both develop from the wolfian-duct of mesonephros. Epididymis can temporarily stores the sperms for as long as one month and here the functional maturation of sperms takes place. 18 to 24 hr. after functional maturation of sperm, sperms proceed further to store in vas deferens, specially in its ampulla part. The wall of epididymis is made up of 2 layers-outer circular muscle layer and inner epithelium. Wall of vasdeferens is also made up of 2 layers-outer circular muscle layer and inner epithelium. The sperms reach the abdominal cavity due to the pulsation of the vas-deferens.
→Cutting of the vasa-deferens & tieing it by a thread is termed as vasectomy.
Vas deferens runs upward & enter into abdominal cavity. Both vas deferens coil around the ureter of their respective sides and then dilate to form ampulla. Ampulla of each side receives the seminal vesicle of that side.
→The vas deferens now forms ejaculatory duct and opens into prostatic urethra.
In rabbit 1 seminal vesicle is found on dorsal side of urinary bladder & it opens at the junction of both vas deferens, while in human 1 pair of seminal vesicles are situated on dorsolateral side of urinary bladder which open separately beforethe terminal ends of vas deferens. So terminal ends of vas deferens meet to form a single ejaculatory duct.
Accessory Reproductive Glands
→ The substances secreted by the accessory reproductive glands help in reproduction, these are-
1. Seminal vesicle
It is also called Uterus-masculinus. If forms from the Mullerian-duct of the embryo. In females, these ducts form the oviducts. Internally, it is lined by glandular epithelium which secretes seminal fluid, which is lubricating, transparent & jelly like substance, which makes 60-70% part of semen. It is slightly alkaline (pH 7.3.). Fructose is found in seminal fluid, it act as fuel to sperm. Fibrinogen, prostaglandin, citrate, inositol and several proteins are also present in semen.
2. Prostate gland
This gland is located below the urinary bladder. It is unpaired & made up of 5 lobes in man. In Rabbit 3 or 4 lobe are found. Each lobe opens into prostatic urethra through many fine apertures. It secretes slightly alkaline prostatic fluid which is milky, thick, sticky or jelly like. It makes about 30% part of semen and helps in sperm activation. In the secretion of prostate-gland citric acid, Calcium and phosphate, clotting enzyme and profibrinolysin are present. The secretion of the prostate gland combines with the secretion of seminal vesicle and so the semen gets coagulated. In the coagulated semen, the mobility of sperms is reduced and so their energy is conserved. After some time of ejaculation due to fibrinolysins, semen again liquefies and in this semen now the sperms can move.
3. Cowper's glands
It is a pair of glands found on lateral side of urethra. It is also called as bulbourethral gland. It is situated in membranous part of urethra & opens into penile urethra. It secretes transparent, slimy, jelly like fluid. It is slightly alkaline (pH is 7.2). This destroys the acidity of the urethra and cleans it for the movement of sperms.
4. Perineal or Rectal glands
These are found both in male and female rabbits. Perineal gland is found around external genital organ & perineal region, while rectal glands are found around external genital organs & anus. During the breeding season, these glands secrete odoriferous liquid which has pheromones or Ectohormones in it.The pheromone develops sexual attraction between opposite sexes & also develops desire for copulation.
Note : - In man, Perineal or Rectal glands are absent.
Semen - Semen = Sperm + Accessary reproductive gland fluid
Volume = 3 to 4ml.
Normal sperm count 20 to 120 million/ml.
Oligospermia < 20 million/ml.
Azospermia – either absence or near absence of sperms.
