a paper about male reproductive system of dog

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Jan 16, 2012 01:23
Hello everyone, I am studying in a vet tech program, and had a paper about male reproductive system of dog.
Could you please correct it?
It is an unfinished long essay, even one collection is really appreciated.
Thank you in advance=)

Male Reproductive System of Dogs

Every body part in animals is essential and meaningful, and each owns a different chore from others.

Male reproductive system is also important because without it, animals cannot produce a descendant.

The task of male reproductive system is to produce male sex hormones, develop male reproductive cells, and deliver at the appropriate time (391 clinical anatomy and physiology).

However, it is not that simple, and there are more than those occur at the same time. Depending on what kind of animals, there are slightly differences on organs as well as their functions.

I chose dogs, one of the closest animals to humans, and their male reproductive systems are pretty interesting.

To start with, the male reproductive system of dog needs to produce male reproductive cells, spermatozoa.

A spermatozoon, a cell, has three parts; a head, midpiece, and tail, whose shape resembles a tadpole.

Its head has the nucleus of the cell, and is covered by the acrosome. A spermatozoon would not be able to reach the ovum without the acrosome because it has digestive enzyme, which penetrate the layer around the ovum.

A spermatozoon also owns a large mitochondria, the source of energy, in its midpiece because it has to travel a long distance to reach the ovum in the female body.

The rest of its body is a long thin tail, and it produces a whip-like movement to move forward. Depending on the size of the dogs, the number of sperms produced is different.

The middle size from 35 to 39 lb of dogs produces around 472 millions of sperms daily (---------------).

Testes, the male gonads, are where spermatozoa are produced in a sac of skin called the scrotum.

They are located outside the abdomen in the inguinal region (textbook 391). They have two important functions; spermatogenesis and hormone production.

The former is the process of producing of spermatozoa. There are seminterous tubes in the testes, and they are the place where spermatozoa are produced.

On the periphery of the tube, there are parent cells, and push daughter cells as they divide. Spermatocytes are male eukaryotic germ cells divided from the parent cell by mitosis, and the primary spermatocytes divide to produce secondary spermatocytes.

They divide again to produce immature male sex cells called spermatids, and they finally grow into mature spermatozoon.

In seminterous tubes, there are also stertoli cells which function as nurses for spermatozoa to help their development.

Nursing spermatids is not the only duty for them, but they also help shield the developing spermatozoa from the body’s immune system.

The latter, the hormone production, is literally the process of producing hormones. In the seminiderous tubes, interstitial cells exist, and they produce male sex hormones, called androgen.

The hormone is essential for the male reproduction because they produce testosterone, which develop male secondary sex characteristics, such as the male body shape and the sex drive.

A testis is divided by septa inside, and each is filled with 1 to 4 highly coiled seminiferous tubes, which is more than70 centimeters long when uncoiled. The other sides of the seminiferous tubes are united together, and are linked rete testis, which located between testes and epididymis.

Epididimis is a ribbon-like structure, which is actually very long tube, lied along the surface of the testes. It continues as the vasdeferens, a passageway of tube. Spermatozoa are stored in epidiymis, and they wait for when ejaculated.

The scrotum is the sac of skin, which holds testes inside. It has an important function to keep the temperature in testes little lower than body’s to produce spermatozoa.

It is attached to the cremaster muscle that adjusts the position of testes. In a warm temperature, the muscle becomes relaxed, and expands the area of scrotum, so that the scrotum can lower its temperature.

On the other hand, when it is cold, the cremaste muscle pulls testes up, and reduces the area of the scrotum surface. The temperature of scrotum is regulated by the cremaste muscle.

The spermatic cord, which is the only connection of testes and the rest of body, also has an temperature regulation function for spermatozoa.

There are blood vessels, nerves, lymphatic vessels, and vas deferens running the spermatic cord. Lymphatic vessels are veins to circulate interstitial fluid, and vas deferens is the muscular tube that carries sperms and the fluid from the testes.

The reason, testes in the scrotum is kind of a structure hanging from the body is adjust the temperature in the testes.

The body temperature is little too high for spermatozoa, so the spermatic cord makes the temperature of scrotum lower than its body.

There is a single testicular artery carrying blood down to the testes, and this is surrounded by the pampinform plexus.

It is a network of tiny veins spreading out the entire spermatic cord. As body-temperature blood passes down to the testes through the testicular artery, it is cooled by the blood returning from the testes in the pampiniform plexus.

Contrarily, the blood in the pampiniform plexus is warmed by the blood in the testicular artery. The temperature in the testes, where spermatozoa are produced, is ingeniously controlled by the pampiniform plexus.