Sexual reproduction in animals
Male Reproductive System
- In sexual reproduction, offspring are formed by the combination of gametes or amphimixes.
- For the formation of gametes, both male and female parents have meiosis in their gonads.
- There are two main stages in the life of a sexually reproductive animal:
- Juvenile Phase/ pro-reproductive stage in which growth of body occur
- Reproductive Phase / maturation stage in which the sex organs are mature.
Animals are either seasonal breeders like goats, sheep and donkeys that breed only in certain seasons or are continuous breeders like humans and monkeys that can breed all year round.
Human Reproduction
Primary sex organs - testicles (testicles: singular) in males and ovaries (ovaries: singular) in females.
Secondary or sexual organs - organs other than the testicles in males and organs other than the ovaries in females.
Secondary sexual characteristics in males -
Beard, mustache, chest hair, muscular body, enlarged larynx (Adam's apple) etc.
Secondary sexual character in women -
Developed breasts, wide pelvis, loud voice. Etc.
Sexual Dimorphism : Events by which gender can be identified externally
Male Reproductive System
Parts of the male reproductive system -
Testis, accessory ducts, glands and external genitalia.
Testicles (Testis) - A pair of testicles, originally formed in the mesodermal, lower abdominal cavity
Location: They are located in a sac called scrotum. In the early stages of the fetus, the testicles develop in the abdominal cavity and then they descend into the scrotum.
Structure : The testicles are male gonads measuring 4.5 mm. Cm long, 2.5 cm wide and 3 cm thick. Each testicle contains about 200 to 300 lobules containing semicircular tubules that form the reticulum.Functions: The testicles produce sperm and the male secretes sex hormones, androgens or testosterone.
Accessory ducts
Rete testis, vas deferens, epididymis, vas deferens, ejaculatory ducts and urethra together form the auxiliary ducts of the male reproductive system.
Rete testis
Position: Towards the posterior side of the testicle
Structure: Formed by the convergence of seminiferous tubules
Functions: Carrying the sperm into the vas deferens
vasa efferentia
Position: They originate from the reticular testis and end
in the epididymis.
Structure: Vasa efferentia consists of 12-20 fine tubes.
Functions: Testicular sperm are transported through these
tubes to the epididymis.
Epididymis:
Location: They are located on the posterior border of each
testicle.
Structure: The epididymis is a long, coiled tube with three
parts, e.g. Caput, corpus and kauda epididymis.
Functions: Spermatogenesis occurs in the epididymis.
Vasa Differentia:
Location: Each odor enters the abdominal cavity through the
differential inguinal canal and then ascends in the form of a spermatic cord.
Structure: Vasa differentia is a 40 cm long tube-shaped pair
arising from the cauda epididymis. The vas deferens on each side are connected
by a duct through the seminal vesicle which forms the ejaculatory duct.
Function: Carrying sperm from the epididymis to the
ejaculatory ducts.
Ejaculation ducts:
Location : Ducts of vas deferess and seminal vesicles
connect to form a pair of tubes about 2 cm long.
Structure: Structure-like tube, 2 cm long passes through the
prostate gland and opens into the urethra.
Functions: Spermatogenic fluids are carried in the urethra
through the ejaculatory duct.
Urethra
Location: The long tube spreads through the penis.
Structure: Tube about 18-20 cm long. Open through the
urethral opening or through the urethral mucus.
Functions: The male urethra provides a normal passage for urine and semen, hence it is also called urinogenital duct.
Accessory glands: are related to the male reproductive system:
(a) seminal vesicles (b) prostate gland and (c) cooper or bulborethral gland.
Each accessory gland contains secretions that help in the
functioning of the reproductive system.
Seminal vesicles:
Position: posterior side of bladder
Structure: A pair of small fibromuscular glands
The secretion of seminal vesicles contains fructose, fibrinogen and prostaglandins. Fructose provides energy for the movement of sperm. Fibrinogen accumulates semen in the bolus. Prostaglandin helps in the rapid movement of sperm towards the ovum in the female body. Contributes to about 60% of the total volume of semen.
Prostate gland
Position : below the bladder
Structure: Large and single gland composed of 20-30
lobes..in the urethra
Functions: The secretion is white and slightly acidic,
prostatic fluid. Semen content is about 30%. Contains citric acid, acid
phosphate and enzymes. Acid phosphate protects sperm from the acidic
environment of the vagina.
Cowper or bulborethral gland
Position : On both sides of the urethra.
Structure: Small, pea-shaped and attached glands.
Functions: Alkaline, viscous mucus secretion like fluid. Acts as a lubricant during intercourse.
External genitalia: The external genitalia contain the male genitalia and testicles.
Penis
Structure: It is a cylindrical, erect and hanging organ through which the urethra passes. It consists of three columns of erectile tissue containing abundant blood sinuses. The tip is called the glans penis and the retractable membrane of the skin on the penis is called the prepuce.
Functions: The penis is the connective organ used to implant or accumulate sperm in the female genitalia.
Scrotum:
Position: In the lower abdomen, behind the penis
Structure : The testicle is a pigmented skin sac formed from
the lower abdominal wall. It protects the testicles.
Functions: The scrotum acts as a thermoregulator. The
testicles are suspended in the testicles by the spermatic cord.
Conditions related to the external genitalia of the male.
Inguinal canal: The passage through which the testicles
enter the testicles.
Gubernaculum: The scrotum has a fibro-muscular band.
Cryptorchidism: Failure of the testicles to descend into the
testicles which can lead to infertility.
Three bundles of tissues formed in the penis: (i) The
attached corpora cavernosa. (ii) Intermediate corpus spongiosum.
Semen: Single ejaculation of semen is 2.5 to 4.00 ml sticky.
Alkaline and milky liquid (pH 7.2 to 7.7)
Histology of testis
- The outer covering of the testicles appeared in L.S. From the outside to the inside are tunica vaginalis, tunica albuginia and tunica vasculosa.
- Testicular mass was divided into 200-300 testicular lobules by tunica albuginia.
- Each lobule contains 1-4 seminiferous tubules.
- The seminiferous tubules contain interstitial cells of Ledig or Ledig cells.
- They secrete the male hormone androgen or testosterone.
- The inner lining of the cuboidal germinal epithelial cells or spermatogonia within the seminiferous tubules
.png)
0 Comments