20/03/2013 § Leave a comment
I’ve never reblogged something before so.
This past Saturday marked the end of an era for fans of DC Comics animation, as Cartoon Network aired the last episodes of Young Justice and Green Lantern: The Animated Series. Though Green Lantern used CGI effects while Young Justice relied on more traditional animation, both series gained a similar cult following. It was a bad omen when the series were shelved mid-season, and things just got worse when they were cancelled just shortly after their return.
In November 2010 Cartoon Network aired the first two episodes of Young Justice as a “world premiere event.” The series then returned on a regular basis in January 2011. Unlike the anime-heavy Teen Titans series from 2003, the series and its characters took themselves very seriously, by quickly establishing the need for a team of “sidekicks.” As a covert operations force for the Justice League, “The Team” (as they were…
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19/03/2013 § Leave a comment
Part 5 (blog 5) is when we start piecing things together and forming a baby! Not literally, of course because that would be really consequential and kind of really stupid. But that’s what fertilization does – it makes a baby! In humans, fertilization is when the egg cell (produced by oogenesis) and the sperm cell (produced by spermatogenesis) fuse to create an embryonic cell.
The process of fertilization can be explained in six steps, as well as a few important vocabulary. As always. HERE WE GO.
- the zone pellucida is the coat made up of glycoprotein that protects the egg cell
- the acrosome as we know by now (or should, at least) is the head of the sperm cell, and essentially a membrane-bound sac of enzymes
- inside the egg cell, near the membrane, are cortical granules, which are vesicles whose contents are important after fusion
- the cortical granules, after fertilization, will release its contents from the egg by exocytosis, which will interact with the glycoproteins from the previously mentioned zone pellucida and turn into an impenetrable membrane called the fertilization membrane
- the blastocyst is what we call the embryo after 48 hours, when it continues to divide and looks like a hollow ball
- finally, implantation is when the blastocyst starts to obtain food and nutrients from the mother by sinking into the endometrium (the uterus lining!)
An Embryo’s Six Steps to Success (A Quick Guide Written By Something That Is Not An Embryo) « Read the rest of this entry »
19/03/2013 § Leave a comment
Honestly, the better and more efficient explanation of oogenesis can be found on the study guide, as opposed to the explanation offered on the course companion. The course companion does provide vocabulary, such as
- the medulla, which is the central ovary tissue
- the cortex, which is the surrounding ovary tissue (around the medulla)
- the germinal epithelium is the outer layer of the ovary (doesn’t a male’s seminiferous tubules also have this?)
- the primary follicle is the cell that has started meiosis with the surrounding follicle cells
- the secondary oocyte normally resides inside a mature follicle over the process of oogenesis
Similarly to spermatogenesis, there is a lot of mitosis and meiosis involved in the production of an ovum, but one of the biggest differences is how much is produced and when. The germinal epithelium cells divide by mitosis to form multiple diploid cells that will grow into the primary oocytes. Once large enough, meiosis beings, and all of this occurs while the baby girl is still in her mother’s womb. The image below shows the rest of the cycle.
Clearly there are some similarities between spermatogenesis and oogenesis, as well as differences. Some similarities are:
- both start with proliferation of cells through mitosis
- both require cell growth before meiosis
- both involve two divisions of meiosis
- (and the obvious one) both produce gametes
A few differences (out of many!) are:
- spermatogenesis produces millions of sperm a day while oogenesis produces one ovum every 28 days
- sperm production starts during puberty for boys while the beginning stages of oogenesis starts while the females are still fetuses
- spermatogenesis lasts an entire lifetime but oogenesis stops at menopause
13/03/2013 § 2 Comments
Genesis is the creation of something. Soooo, if we smash “sperm” and a few more letters into the word “genesis,” then we get spermatogenesis, which is the production of sperm. This production occurs in the seminiferous tubules of the testes, which are a mass of narrow tubes. Between the tubules are interstitial cells, which make up gaps called interstices. The outer layer of cells that makes up the seminiferous tubules is called the germinal epithelium. Sperm in production are contained within the germinal epithelium and the ones closest to the mature stage are closer to the fluid-filled centers. Sperm cells that have developed tails are called spermatozoa, but we know them as sperm. Then, there are brilliantly altruistic nurse cells called Sertoli cells that feed the sperm as they develop.
The hormones involved in the production of sperm cells are: FSH, testosterone, and LH. Note that FSH and LH are also used in the production of egg cells. Semen is also produced with the sperm for various reasons. The semen contains nutrients for the sperm like fructose as well as mineral ions (making it alkaline) to protect them from the vagina’s acidic conditions.
12/03/2013 § Leave a comment
Reproduction starts when a male’s sperm fuses with a female’s egg. For humans, the gender of the embryo are determined by the tdf gene, which is usually found on the Y-chromosome, therefore the tdf gene would make the embryo a male. While estrogen and progesterone are the hormones that trigger the growth of female genitalia, testosterone is the hormone that triggers the development of male genitalia. It also fuels the sex drive in men.
Just for kicks, here are diagrams of the male and female reproductive system (because I hadn’t posted an image in the previous blog post).
11/03/2013 § Leave a comment
This next unit will start off as review of what we learned in middle school and in ninth grade. Let’s start from the very top with the female reproductive system. Okay, so an embryo in its mother’s wound can develop into a male or a female fetus. If the tdf gene is present, the baby develops into a male. If it isn’t there (usually it’s on the Y-chromosome), then the baby will probably become a female, but I’m assuming there are some rare cases. The embryonic gonads would then develop into ovaries (instead of testes), along with the production of the two female hormones – estrogen and progesterone, which are always present during pregnancy. These two hormones trigger the development of the female genitalia. Note: We’ve been talking about humans this whole time, excuse me.
What we learned in middle school and ninth grade was the menstrual cycle, but here, we take a look at the hormonal control of the menstrual cycle. Human females can reproduce at any give time of the year because of the production of the eggs in follicles, which are fluid-filled sacs. The endometrium – the lining of the uterus – thickens in preparation for the implantation of the embryo. If, when the follicle releases an egg, and fertilization doesn’t occur, then the released egg (called the corpus luteum) breaks down in the process of menstruation.
Over the period of a menstrual cycle, the hormone levels in a human female change. The ovary and endometrium are what endures the most change. The first half is called the follicular phase, because it’s when the follicle develops. The second half is called the luteal phase, because it’s the period where the corpus luteum develops.
There are so many essay questions for this unit, I could cry.
10/03/2013 § Leave a comment
egoísta (adj.) – selfish
— En un mundo donde ya no queda nadie, no puedo enfatizar bastante qué importante es valerse de uno al otro. Esta no es la hora para ser egoísta o tener miedo. Necesitamos acumularse tanta comida y reserva como posible y necesitamos organizar una sistema para podemos ser más eficientes.
El día es el 28 de marzo del año 2097. Hace más frío que los días de primavera antes la invasión.
— Tú y tú – ¡vayan al río y recoger agua!
Hemos estados parados por treinta minutos y la espera no está siendo más fácil. Mi primo más joven se agita a mi lado. Agarro su mano y exprímala. Bajo mi aliento, trato de decir a él que podemos hacerlos durante el día juntos, aunque tenemos que trabajar en sectores diferentes. Apenas dije este, mi primo fue llamado a sector dieciséis.
— Bueno… verte alrededor, hombre.
Trato de no verle alejarse.