The Reproductive System Essay
The Reproductive System
The reproductive system occurs in both male and female.
Like in plants it is the male gamete that needs to be transferred to
the female gamete. The female gamete is fertilised and develops inside
the mother’s body so the reproductive systems of both males and
females are highly adapted for this.
Production of sperm is called spermatogenesis.
It occurs at puberty and for the rest of there life.
It takes place in the gonads of the male - the testes. Over 100
million can be made in one day!
Each testis is composed of numerous tiny tubes called seminiferous
tubules. It is in the walls of these tubules that sperm production
actually takes place.
Development begins in the outer side of the wall in a layer of cells
called the germinal epithelium. As the immature sperm cells become
more mature they move to the inner side and break way into the lumen
of the tubule to be carried away to the epididymis for storage. The
process of this production is shown in the next two diagrams.
In between the tubules, inside the testes, are interstitial cells
called Leydig cells. These secrete the hormone testosterone.
There are also blood vessels in close proximity, delivering nutrients
and carrying away some testosterone to other target cells for the
development and maintenance of secondary sexual characteristics, e.g.
facial and pubic hair, deepening of the voice. The testosterone also
stimulates the cells inside the testis involved in spermatogenesis.
Hormonal control of spermatogenesis
The control centres are the pituitary gland and the hypothalamus in
The hypothalamus secretes GnRH (gonadotrophin releasing hormone). This
is released into the blood and stimulates the anterior lobe of the
The anterior lobe of the pituitary gland secretes ICSH (interstitial
cell stimulating hormone).
ICSH: this stimulates the leydig cells that produce testosterone.
FSH: this stimulates the seminiferous tubules, including the Sertoli
cells. They produce sperm in response.
Note: Testosterone also acts on the seminiferous tubules and
stimulates sperm production.
The testosterone feeds back to the hypothalamus and pituitary gland to
switch off GnRH and ICSH release.
The Sertoli cells produce a hormone called inhibin that feeds back to
the pituitary gland to switch off FSH release.
Since the action of the interstitial cells and Sertoli cells are
inhibited, less testosterone and inhibin are released as a result. The
inhibition of the hypothalamus and pituitary is lifted and the process
can start again. Due to the levels of the hormones and their effects,
the process is not noticeably cyclical – there aren’t noticeable peaks
and troughs in the levels of the hormones.
The production of eggs is called...
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Ascaris reproduces sexually and is dioecious. It shows sexual dimorphism.
Image Source: 188.8.131.52
(1)Male reproductive organs:
These organs are confined to the posterior half of pseudocoel and include following organs.
Male ascaris is monarchic, possessing a single testis which is long, thin and highly twisted tube like structure.
It occupies most of the pseudocoel in posterior 2/3 of the body. Wall of testis is made up of a single layer of cuboidai cells.
Proximally it is closed and contains germinal zone that produces spermatogonia through budding from a single germinal cell.
The rest of the testis contains a solid axis called cytoplasmic rachis. It serves as a surface of maturation and growth of the sperms.
Distally testis leads into short and thick twisted tubes, the vas deferens. It is distinguished from testis in having a lumen in place of the rachis.
Vas deferentia are followed by a much thicker, wider, somewhat muscular straight tube, the seminal vesicle. It serves to store mature sperms.
4. Ejaculatory duct:
Terminal part of seminal vesicle narrows to form a highly muscular ejaculatory duct. It joins rectum to form the cloaca. Its wall contains a number of prostatic glands, whose secretion helps in copulation.
Two small contractile penial sacs open dorsally into the cloaca. Each sac contains a small needle like penial orcopulatory seta made up of cuticle.
The spicules protruded and retracted through the cloacal aperture by the action of protractor and retractor muscles of the sac wall spicules help in opening the female gonopore for copulation.
(2) Female reproductive system:
This system is situated in the posterior 2/3 part of the body and consists of ovaries, oviduct, uteri and vagina.
Female Ascaris is didelphic i.e., it has two ovaries two oviducts and two uterus. Each ovary is a long, thin thread-like much twisted tube.
These are also telogenic like the testis. Proximally it bears germinal cell to produce ova. Remaining distal part of the ovary contains cytoplasmic rachis and acts as growth zone for ovum maturation. There is no lumen.
Each ovary leads into a long coiled oviduct of same thickness and similar wall without any external distinction. It has a lumen.
Each oviduct followed by a thick and long but straight uterus extending from behind forwards, its wall is thick and formed of an inner layer of tufted secretory cells surrounded by a muscular layer. Uteri serve to store the eggs after fertilization.
Anteriorly both uteri bend median wards and join together to form a very short and relatively narrow vagina. Its wall is quite muscular and contractile. Anteriorly it opens out by the midventral transverse slit-like female gonopore or vulva.