Spermatogenesis and Oogenesis Flashcards
Meiosis Review
Complete the meiosis Atomy quiz to check your understanding.
Practice content regularly to prevent it from becoming "rusty", especially after moving on from unit three.
Reviewing topics covered a while ago can be very effective for exam preparation.
Production of Sperm Cells and Egg Cells
Spermatogenesis: production of sperm cells
Oogenesis: production of egg cells
Differences exist in the production of sperm cells versus egg cells.
Syllabus point: Compare and contrast spermatogenesis and oogenesis with reference to haploid and diploid cells within the context of meiosis I and II.
Egg cells need to carry the genetic material, energy stores, and organelles required for the early development of a zygote.
Sperm cells primarily need to carry genetic material and be able to reach the egg.
Oogenesis
Oogenesis is female gamete production.
Meiosis in oogenesis results in one large, viable egg instead of four equal haploid cells.
The other three haploid cells are called polar bodies, which degenerate and their components are reused.
Polar bodies carry genetic material but have an uneven distribution of cytoplasm and organelles, making them non-viable.
This process ensures the best quality and chance of survival for the single egg, which is crucial due to the finite number of eggs a female has.
Females produce all their eggs before birth or in the early stages, whereas sperm cells are continuously produced from puberty until death.
Menopause occurs when there are no more eggs to be released.
Oogonium
Oogonia (pre-egg cells) undergo mitosis before meiosis one.
Mitosis produces two oocytes.
Process of Oogenesis
Begins during fetal development, where diploid oogonia are formed by mitosis.
From one oogonium, two egg cells are produced, one from each oocyte.
Cells begin meiosis one but are arrested in prophase one until puberty.
At puberty, follicles develop each month in response to follicle-stimulating hormone (FSH).
The follicle completes the first meiotic division into two cells of unequal size.
A larger cell with more cytoplasm and organelles, and a first polar body, which degenerates.
The larger cell forms the secondary oocyte.
The secondary oocyte begins meiosis two but is paused in metaphase two until fertilization.
The egg is released from the ovary and travels through the fallopian tubes.
If fertilization occurs, meiosis two continues.
After every division results in polar bodies.
There are three polar bodies and one large viable egg cell for every oocyte.
Diagrammatic Representation
Diagrams may represent polar bodies differently, but remember there are always three polar bodies and one viable egg.
There are clear pauses/development at certain level and then wait for the next hormone to be released to push development on.
Spermatogenesis
Spermatogenesis is the production of sperm in the seminiferous tubules of the testes.
Spermatogenesis begins at puberty.
Each dividing cell produces four functional sperm cells of approximately the same size.
Spermatogenesis is continuous, unlike the monthly release of eggs.
Process
Spermatogenesis begins with the mitotic division of diploid spermatogonium.
Mitosis at the beginning of meiosis means the first stage spermatocyte produces 2 of them, so from one spermatogonia, eight sperm are produced.
Meiosis one and meiosis two result in four haploid spermatid cells.
Spermatids differentiate into sperm by losing most of their cytoplasm and gaining a flagellum.
Losing cytoplasm reduces water resistance for swimming.
The sperm structure's only goal is to carry genetic material and swim fast.
Summary
Comparing spermatogenesis and oogenesis involves understanding haploid and diploid cells.
Comparison
Sperm is small with no food source.
Egg is larger with its own energy/food source.
Sperm is mobile, and the egg is not.
Sperm is made in the male gonads (testes), and the egg is made in the female gonads (ovaries).
Sperm production occurs from puberty until death.
Females are born with a full complement of eggs and do not make new ones.
Both sperm and ova (eggs) are haploid.
Haploid means having half the normal genetic material (a single set of chromosomes).
Four sperm are produced from a meiotic division, while one ovum is produced from a meiotic division.
Action Items
Submit a Venn diagram comparing mitosis and meiosis to demonstrate understanding.
