Gametogenesis, Fertilization, and Implantation

Flashcards on Gametogenesis, Fertilization, and Implantation based on lecture notes.

Where does spermatogenesis occur, and when does it begin?

Spermatogenesis occurs in the testes after puberty (12-14 years).

What two hormones initiate and sustain spermatogenesis?

Follicle-stimulating hormone (FSH) initiates spermatogenesis, and testosterone sustains it.

Why are the testes located in the scrotum?

The testes are in the scrotum because spermatogenesis is optimum at 2-3 degrees Celsius below body temperature.

Where within the testes does spermatogenesis take place?

Spermatogenesis occurs within the seminiferous tubules of the testes.

What is the role of the blood-testis barrier?

The blood-testis barrier prevents the immune system from attacking cells undergoing meiosis.

What are the three stages of spermatogenesis?

Spermatocytogenesis, spermatidogenesis (meiosis), and spermiogenesis.

What happens during spermiogenesis?

Spermatids are converted into tadpole-shaped spermatozoa via cytodifferentiation, including nuclear condensation, tail formation, acrosome formation, organelle rearrangement, and shedding of excess cytoplasm.

What is the total time spermatogenesis takes?

The entire process of spermatogenesis takes approximately 64 days.

What is oogenesis?

Gametogenesis in females, resulting in the production of secondary oocytes (ova).

When does oogenesis commence?

Oogenesis commences prenatally, around the 5th month in utero.

What are the two main processes of oogenesis?

Mitosis of ovarian follicular cells and meiosis of the oocyte.

What happens to primary oocytes before puberty?

Before puberty, all oocytes are primary and housed in primordial follicles, suspended in the dictyotene stage of meiosis I.

When does the secondary oocyte complete its second meiotic division?

The secondary oocyte completes the second meiotic division only after fertilization by a spermatozoon.

What are the requirements for in vivo fertilization?

Successful coitus, adequate numbers of competent spermatozoa, the ability of spermatozoa to overcome obstacles in the female genital tract, a viable secondary oocyte, and a female genital tract free from infections.

What is the zona pellucida?

A gelatinous internal layer separating the plasma membrane of the ovum from an outer layer of corona radiata cells.

What is capacitation?

Physiological changes that spermatozoa must undergo to acquire the capacity to penetrate and fertilize the secondary oocyte.

What is the acrosomal reaction?

Changes in the acrosomal cap that release enzymes, such as hyaluronidase, to digest the cumulus cells surrounding the oocyte.

What are the three sequential events of fertilization?

Penetration of the corona radiata, penetration of the zona pellucida, and binding and fusion of the oocyte and sperm cell membranes.

What is the zonal reaction?

The alteration of the zona pellucida, making it impermeable to other sperm, triggered by the release of cortical granules from the oocyte.

What is polyspermy, and what is its result?

Fertilization by more than one spermatozoon, which does not proceed beyond a few cleavages of the zygote, leading to the death of the pre-embryo.

What event takes place after fertilization?

The sperm head releases paternal chromosomes into the oocyte to form the male pronucleus and the secondary oocyte completes the second meiotic division and ejects the second polar body.

How is genetic sex determined?

The genetic sex of the zygote depends on the sex chromosomes contributed by the sperm. XX for female, XY for male.

What is contained in semen?

Semen contains spermatozoa and secretions of the prostate gland and seminal vesicles.

Why is a healthy secondary oocyte necessary for fertilization?

The oocyte must lack structural abnormalities and possess the correct number of chromosomes, including essential cellular signaling.

Where does spermatogenesis occur?

a) Liver

b) Kidneys

c) Testes

d) Brain

When does spermatogenesis begin?

a