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Asignment1 Investigating fertility

Asignment1 Investigating fertility

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Task 1

a) Process of Oogenesis (ovum production)

Oogenesis is the process of formation of ova or eggs in the ovary of a female.

The start of the process begins with the formation of diploid germ cells called

oogonia or primary oocytes, which are created during the fetal period. Primary

oocytes are arrested in prophase I of division at the time of birth of the female

fetus. However, as the fetus develops into a female and when the female

reaches her menarche, the primary oocytes start to undergo meiosis. The

primary oocyte divides into two haploid cells, one of which is capable of

developing into an ovum and the other is capable of developing into a polar

body. Half of the chromosomes are taken by the polar body while the other

half are available to become ova. This process leads to the creation of the

secondary oocyte which is released into the fallopian tube upon the rupture of

the mature follicle. This process is termed as ovulation. Once the secondary

oocyte is in the fallopian tubes, the process of oogenesis remains halted till the

secondary oocyte is fertilized. It has a time frame of three days for being

fertilized, as if it is not fertilized, it will not undergo the second stage of

meiosis. Upon fertilization by a sperm, the oocyte immediately undergoes

meiosis 2 leading to the formation of two polar bodies and an ovum which is

capable of developing into an embryo (Pensky B. 1982).

b) Spermatogenesis (sperm production)

Spermatogenesis is the term applied to production of sperms. It takes place in

the testes. Testes are composed of convoluted and thin tubules termed as

seminiferous tubules. Walls of the seminiferous tubules produce the sperm

cells and they also possess specialized cells called Sertoli cells (Xiao, Mruk

and Cheng, 2013) which nourish and support the sperms during their

production. The cells which differentiate into sperms are called germ cells.

Immature germ cell needs as much as seventy four days to reach maturation,

and during this process there are resting phases as well.

The immature cells are termed spermatogonia which all originate from cells

termed as stem cells in the outer wall of the seminiferous tubules. These stem

cells start multiplying by the process of mitosis. Half of the new cells from

this initial stage go on to develop into sperm cells, and the other half remain

behind as stem cells so that a constant source of germ cells persists. This is

very important because spermatogenesis is a life time process for the males.

Spermatogonia which have to develop into mature sperm cells are called

primary sperm cells. They transition from the outer portion of the seminiferous

tubule to a central location and get attached around the Sertoli cells. After the

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resting phase the primary cells divide into secondary sperm cells. During this

cell division there is a splitting up of the nuclear material. The nucleus of the

primary sperm cells has forty six chromosomes while of the secondary sperm

cells gets only twenty three chromosomes, as much as there are in an egg. The

secondary sperm cell still needs to mature before they are able to fertilize an

egg.

Maturation of the sperms leads to alterations in their morphology (form and

shape). The changes include condensation of the nuclear material to assume an

oval shape. This oval and condensed are is referred to as the head of the sperm

cell. Acrosome caps the head of the sperm and is vital for the sperm to enter

into the egg. Secondary sperm cell’s cytoplasm is converted into the tail piece

of the sperm.

c) Annotated hand diagram of process of meiosis

Attached on sheet.

Task 2a

Female hormones

Oestrogen

Structure from which it originates: Ovaries.

The structure on which it acts: Female reproductive tract, breasts and other parts of

the body.

The hormones function (Whitehead and Nussey, 2001) are:

• Development of secondary sexual characteristics

• Maintain growth of endometrial.

• Bone functions including bone strengthening

• Metabolism increase

• Growth of uterus

• Vaginal wall thickening

• Skin vitality

• Proper lubrication of vagina

• Maintaining body fats.

The effect it has on other hormones: FSH and LH act synergistically to initiate

estrogen secretion. The estrogen has a negative feedback on FSH, which leads it to

stop being secreted.

Progesterone

Structure from which it originates: Ovaries (corpus luteum), placenta and adrenal

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Task 1 a) Process of Oogenesis (ovum production) Oogenesis is the process of formation of ova or eggs in the ovary of a female. The start of the process begins with the formation of diploid germ cells called oogonia or primary oocytes, which are created during the fetal period. Primary oocytes are arrested in prophase I of division at the time of birth of the female fetus. However, as the fetus develops into a female and when the female reaches her menarche, the primary oocytes start to undergo meiosis. The primary oocyte divides into two haploid cells, one of which is capable of developing into an ovum and the other is capable of developing into a polar body. Half of the chromosomes are taken by the polar body while the other half are available to become ova. This process leads to the creation of the secondary oocyte which is released into the fallopian tube upon the rupture of the mature follicle. This process is termed as ovulation. Once the secondary oocyte is in the fallopian tubes, the process of oogenesis remains halted till the secondary oocyte is fertilized. It has a time frame of three days for being fertilized, as if it is not fertilized, it will not undergo the second stage of meiosis. Upon fertilization by a sperm, the oocyte immediately undergoes meiosis 2 leading to the formation of two polar bodies and an ovum which is capable of developing into an embryo (Pensky B. 1982). b) Spermatogenesis (sperm production) Spermatogenesis is the term applied to production ...
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