Difference Between Sperm and Ovum

Introduction

The sperm is a male gamete, produced in the testes. It remains inactivated before ejaculation in the female tract that has a specific pH range helps in the capacitation of the sperm and controls its motility towards the ovum. The mitochondria supplies energy and the flagellum helps in propelling. In the ovary, the ovum is produced and matures but remains dormant. Though a million sperms are ejaculated, only the capacitated one can penetrate the outer membrane via dissolving to enter inside the ovum. Only the nucleus and the centrioles of the sperm can enter the ovum leaving the flagellum. The mitochondria degenerated. After fertilization, the zygote has maternal mitochondria, paternal centrioles and two haploid sets of chromosomes from both of them. In this article, we will discuss sperm and ovum in detail.

Sperm

Sperm is a motile, reproductive, male gamete takes part in sexual reproduction. It has a flagellum to control the motility of the animal sperm cell. The plants, algae and fungi develop non-motile sperms lacking the flagellum except gymnosperms and ferns. The animal sperm cell is called spermatozoa. The plants that have pollen, produce spermatia. The animals develop sperms in the process of spermatogenesis. The sperm cell is produced in the seminiferous tubules of the testes and then stored in epididymis. In the time of ejaculation, the sperm cells remain as fluid called semen. In spermatogenesis, the sperm cell precursor forms spermatogonia. The spermatogonia divide to develop spermatocytes. The spermatocyte undergoes meiosis division to half the chromosome number and forms spermatids. The mature spermatid is differentiated in head, neck, middle body and tail or flagellum. The sperm cells take 3 months to mature and have a restricted life span. They are activated after entering the female reproductive tract and then only one capacitated sperm cell can fertilize the egg cell and develop a zygote.

The sperm cell of amniotes (mammals) has two basic parts − the head consists of the condensed chromatin fiber enclosed in the nucleus. It has a sac-like cap named acrosome containing an enzyme called hyaluronidase that dissolves the outer membrane of the egg made up of hyaluronic acid. It also contains vacuole. The tail or the flagellum is the longest part of a sperm cell, helps swimming and moving towards the ovum through the female tract by propelling and creating wave-like motion. The flagellum propels helically. The tail and the head are connected with the middle body that consists of many mitochondria and two centrioles. The mitochondria forms ATP, which helps in propelling. The mid-piece is spirally surrounded by the mitochondria.

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The sperm centriole helps in developing the microtubules. The nucleus contains a haploid number of genomes (n = 23), forms diploid (2n = 46) conjugating with the egg haploid nucleus. It also activates the dormant oocyte after fertilization.

Ovum

The ovum is the rounded and larger female gamete, that also takes part in sexual reproduction along with the small, motile sperm cell. After fertilization they develop a zygote. The ovum is produced in the ovary or female gonad. The size and the yolk amount of the ovum differs in different animals. The germ cell divides repeatedly to form an ovum by oogenesis. It develops oogonium then oocyte.

The outer layer of the ovum, called cortex, contains microvilli, which helps to export and import substances from ooplasm or the cytoplasm. Ooplasm is the nutritive yolk, found a little in the human ovum. The ooplasm is made up of fat and albuminoid stuff. The cytoplasm contains the germinal vesicle or nucleus and the germinal spot or nucleolus. The mammalian ovum shows polarity. The animal pole occupies the nucleus and opposite to the animal pole is called vegetal pole. The ooplasm is surrounded by the membrane called vitelline membrane and then the zona pellucida. The perivitelline space is found in between these two membranes. The outermost layer of the ovum is called corona radiata, made up of epithelial cells.

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In bryophytes, the ovum is produced from the archegonium by mitosis. The archegonium consists of a long neck and base containing the egg cell. The gametes are produced from the gametophyte (n) and allow entering the sperms after maturation through the neck. After fertilization the zygote gives rise to a sporophyte (2n). In flowering plants, the ovule produced in the ovary. After pollination, the pollen tube penetrates the embryo sac through micropyle, fertilizes the egg cell, and forms a zygote that develops seed by further division. The seed enclosed in the placenta, develops fruits. The seed can give rise to a new offspring.

Difference between sperm and ovum

Sperm	Ovum
Male gamete.	Female gamete.
Has flagellum, controls motility.	Non-motile, no flagellum exists.
Smallest human cell.	Largest human cell.
Four sperms formed from a single spermatogonium.	One ovum developed from one oogonium.
Sperm is divided into head, neck, body and tail.	A round shaped gamete without any external segmentation.
Has plasma membrane.	Zona pellucida, the outer membrane.
Formed in the testes.	Formed in ovaries.
Central mitochondria (75-100) and dissolves in the time of fertilization.	Mitochondria scattered in cytoplasm (100-200000) and placed on the blastocyst after fertilization.
Centriole present.	No centriole.
A little cytoplasm present due to their smaller size.	Large amount of cytoplasm exists.
Bears X and Y chromosomes.	Bears XX, one activated and another deactivated. The deactivated, small X chromosome is called the barr body.
Releases enzymes to dissolve the outer membrane of ovum to penetrate.	Swallow up the sperm, leaving the flagellum.
A huge number of sperms are formed per day.	Every 28 day one ovum matures, per menstrual cycle.
Enzymes packed in the acrosome of the head.	Enzymes packed in cortical granules.

Conclusion

The female and the male gametes are known as sperm and ovum respectively. The sperm produced in the testes of a male while the female reproductive organ or the ovary produces an ovum. Both the gametes take part in sexual reproduction of an organism and form an embryo. The sperm and the ovum contain the haploid number of chromosomes. After fertilization they become diploid by conjugation. The shape, size, constituents and the developmental process of the gametes varies depending on the animals and plants.

FAQs

Q1. Define corpus luteum.

Ans. In the ovulation period, the ovarian follicle releases a mature ovum. The remaining follicle is called corpus luteum that produces high progesterone and estrogen in moderate levels.

Q2. Define graafian follicle.

Ans. The mature ovarian follicle that does not release the ovum yet is called graafian follicle.

Q3. What does placenta mean?

Ans. Placenta is an organ attached in the mother’s womb, holds the baby by the umbilical cord, and supplies nutrients and oxygen to a growing baby.

Q4. What happens if the mature ovum is not fertilized?

Ans. If not fertilized, the corpus luteum stops releasing progesterone and decays. The degenerated luteum becomes a mass of tissue, remains in endometrium and expelled through menstruation.