Essay On Spermatogenesis

Spermatogenesis

Spermatogenesis is the formation of the male sex cell, sperm. This process begins with the differentiation of germ cells to form stem cells. A first mitotic division creates spermatogonia (diploid) and a second creates spermatocytes (diploid). Each spermatocyte then goes through meiosis to firm four haploid spermatids. In the seminiferous tubules the cells move towards the centre of the tubules as they undergo shape changes. The cells go through a spermatocyte and a spermatid stage and move into the lumen then the epididymis where they finally become mobile (textbook).

Oogenesis

Oogenesis is the formation of female sex cells, oogonia (eggs). Oogonia begin in the ovary as a diploid cell and then move to the stroma where they are transformed into primary follicles. A growth phase turns the primary follicles into primary oocytes, which are still diploid. Further in the stoma stroma the primary oocytes are covered in layers of cells which will form the follicle wall. Oocytes, surrounded by fluid-filled follicles, enter the outer ovary where a meiotic

division creates secondary oocytes and the first polar bodies. At this point, nothing occurs until an oocyte is ovulated where it undergoes another division and forms a haploid ovum and three haploid polar bodies. The polar bodies disintegrate and the ovum then leaves the follicles (which are then called corpus luteum) (lab manual).

a.
The sperm of the three difference species observed in lab all had the same basic structure, heads and tail. Additionally, the sperm were very small in size, especially in comparison to the ovary cross-section that was examined. Overall, the bull sperm appeared to have the largest head and the human sperm appeared to be the shortest in length of the three. The rat sperm had the longest length with a small hook shaped head. Although the sperm of the rat, human, and bull differed slightly, the over structure of the sperm cells were same.
b.
Three notable similarities between the rat, human, and bull sperm were observed. Firstly, all of the sperm cells had a head. Secondly, the sperm calls all had tails that were much larger in comparison to the head. Lastly, all of the sperm cells were very small and numerous, especially in comparison to an ovary.
There notable differences between the rat, human, and bull sperm were observed. Firstly, although all types of sperm had heads, they varied in size. For example, the bull sperm had the largest head in comparison, and the rat sperm had a characteristic hook shape to the head of the sperm, which was almost as thin as the tail. Secondly, the tail length of the sperm cells differed. For example, the human sperm was short in comparison to the other two species and the rat had the longest tail. The final difference was the amount of sperm present. The human sperm was very small in size but there were many more human sperm cells than the other two species. This occurrence may be as a result of the small size of the human sperm, making it more advantageous to have larger amounts of sperm produced.
3.

Sperm and Eggs

a.

Sperm are small and mobile so that the likelihood of fertilization is increased. Having a reduced size and the ability to move allows the sperm to move towards the immobile egg. The size of the sperm is ideal for the passage through the vaginal cavity. The male body would use more energy producing larger sperm cells, instead, many more small sperm are produced to optimize the amount of energy used to produce the sex cells (Geoff).

The egg must be larger than the sperm as it is the first cell that will grow to form a baby. The egg is also most likely larger than the sperm as a result of not having to make the same journey to the uterus that the sperm undergoes. Additionally, the egg is large and immobile because it must stay in the uterus as that is where a baby will grow for nine months, unlike the sperm, the egg is already in position for fertilization to happen (Text 1057).

b.
Males produce so many sperm in order to increase the likelihood of fertilization. The more sperm present in the vicinity of the egg, the more likely that the egg will be penetrated and fertilized. (Braden). In contrast, females produce very few eggs because every cycle (approximately 28 days) of a female’s reproductive years, only one egg cell is released from the ovary. Females do not need to produce more eggs because a limited number of eggs are used, as opposed to males who release many times as much sperm every time they ejaculate. Additionally, the sperm the survive all end up in the same area of the female reproductive tract, the uterus, therefore there is no need for more eggs to be released each month as it would not increase the probability fertilization (Textbook 1057).
c.
The head, tail, acrosome, and mitochondria of a sperm cell are all specialized to increase mobility, allowing the sperm to more efficiently reach and penetrate the egg (Don). The function of the mitochondria is to provide the cell with energy. Mitochondria provide sugar by converting chemical energy (John). The acrosome is a structure the covers the nucleus of the sperm cell and is responsible for starting the chemical reactions that are necessary for the fertilization of the female egg (Don). The tail of the sperm makes movement possible and is made up of microtubules and fibers that contribute to the function of the tail (Don). The head of the sperm is specially modified so that it increases the maneuverability of the sperm. The parts of the head include the acrosome, the subarosomal space, the nucleus, and the neck. All of the components of the head allow for more efficient movement of the sperm (Don).
d.
Non-growing follicle cells produce new follicles which surround the oocytes (immature eggs) and aid in development. This process continues until a female reaches the age where she can no longer reproduce (John J). In the egg, cytoplasm provides nutrients, is the substance that all other organelles within the cell float in, and are also essential for cell division (cytoplasm is split between new cells) (text 1073).