The human body is an amazing thing. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.
The humble chin, that bony protrusion Types of chins and what they mean the bottom of your face, is a mysterious little body part that is a surprising source of controversy among researchers. Though popular culture derives great meaning out of how "strong" or "weak" chins are, very little science backs that up.
The most interesting thing about the chin, according to Faisal Tawwaba family practice doctor with Multicare Physicians in Orlando, Florida, is that there is no precise answer as to why we even have one.
There are critiques around all of the current prevailing theories.
The chin may have evolved to protect the jaw from the unique stresses of shaping our mouths to form language, according to a study in the journal Medical Hypotheses. Your chin may help bear some of the muscle load of chewing and speaking a valid reason to want a strong one. Research supports this theory, suggesting that the chin " helps buttress the jaw against certain mechanical stresses," including chewing, which produces a great deal of force.
A more recent theory is that our chins helped us choose mates. Types of chins and what they mean tend to have narrower and rounder chins," says Gargano. While humans may share some things in common with animals, chins are not one of them. It's not a bony protrusion, which is a real chin—and a feature that's ours alone. In short, it's evidence of our species's evolution—and one of our defining physical characteristics.
The reality is much more mundane. A chin may not have anything to do with withstanding pressure or attracting a mate, according to Nathan Holton, an anthropologist at the University of Iowa. The lower jaw is the last part of the face to stop growing, which causes it to be more prominent as compared to other parts of the face.
The prominent chin "is a secondary consequence of faces getting smaller," Holton writes. Their Types of chins and what they mean responsibilities include producing eggs and secreting sex hormones that promote fertility. In this way, the future of humanity depends on them.
Read on to learn more about these tiny but mighty organs. It actually refers to the reproductive glands of both sexes: When an embryo is in the early stages of development around the seventh weekits gonads have the potential to develop into either female or male sex organs through a process called sexual differentiation.
By this point, the sex has already been pre-determined by chromosomes XX or XYand in the absence of a Y chromosome, the gonads turn into ovaries. One study of adult mice found that ovaries could be turned into testes by deleting a single gene called FOXL2, which is constantly working to suppress the development of male anatomy in mammals.
However, it's unknown what effect the modification of this gene would have on humans.
Breathtaking types of chins and what they mean nude 18+
The hypothalamus and pituitary gland both play pivotal roles in ensuring the ovaries function as they should. Neither is located anywhere near the ovaries, though.
Essentially, the hypothalamus tells the pituitary gland to send hormones to the ovaries, and the ovaries respond by secreting their own batch of hormones. A signal is then sent back to the hypothalamus to let it know if the levels of estrogen and progesterone are too high or too low. The cycle then continues, but we don't fully understand what triggers the hypothalamus and kicks off the process in the first place, Epstein says.
In the latter Types of chins and what they mean, scientists have been looking at different genetic markers in an attempt to predict when the ovaries will shut down the processes of menstruation and ovulation—otherwise known as menopause —but "nothing is definitive" right now, according to Mary Jane Minkin, an obstetrician-gynecologist in New Haven, Connecticut, who also teaches at the Yale School of Medicine.
However, family history and age offer some clues. The average age for menopause in the U. Women who have had hysterectomies may also go through menopause one or two years earlier than they normally would, even if they have otherwise healthy ovaries.
That's because the surgery is believed to reduce the flow of blood to the ovaries, resulting in a lower supply of hormones and therefore earlier ovarian failure. Ovaries get bigger and morph into the shape of an almond when girls reach adolescence, eventually reaching roughly 1.
Later in life, once menopause has occurred and the ovaries have fulfilled their purpose, they dwindle to under an inch long. Here's a mind-boggling fact: Many of these eggs die off before a girl reaches reproductive age, though.
By the time she starts going through puberty, she has aboutleft. About or so eggs are lost each month after that. Research in recent years has suggested that ovarian stem cells could someday be used to grow new egg cells, or to delay or stop menopause in women. Both of these tasks have already been successfully carried out in mice.
For now, women faced with a diminishing supply can have their unfertilized eggs frozen through the process of cryopreservation.
Those ovaries were then filled with follicles containing immature egg cells, which allowed the mice to give birth to healthy babies. Scientists hope this technique will someday be used to restore fertility to women whose ovaries have been damaged by cancer treatments.
Oral contraceptives prevent ovulation by providing all the estrogen and progesterone that the body needs.
The ovaries are also less exposed to naturally occurring hormones that may promote the growth of cancer. One of the most common problems affecting the ovaries are cysts. Fortunately, these cysts often go away on their own.
They only become a problem if they grow, or multiple cysts form. Strange things can happen, though. In one recent casesurgeons found a cyst containing a miniature skull and brain tissue inside the ovary of a year-old girl. Yes, you read that right. It's called a teratoma —from the Greek word for monster —and it happens when the reproductive cells go rogue and start developing their own way.
Another disorder that can sometimes affect the ovaries is endometriosis. It can attach to the bladder, bowel, ovaries, or other areas.
Symptoms may be minimal, severe, or somewhere in between, and the tissue can be removed through a minor surgery if needed. Ovulation may not go as smoothly, periods can be irregular, and cysts can develop.
The main active ingredient was alcohol. Unlike their dinosaur ancestors, birds have only their left ovary. Scientists theorize that birds lost an ovary over the course of evolution because it helped reduce their weight, making it easier for them to fly.
This explains why dinosaurs laid loads of eggs, but birds lay just a few at a time. This is because they have both mature testes and immature ovaries, the latter of which can develop if the alpha female in a school of fish dies.
Types of chins and what they mean Business Insider points outa scientifically accurate Finding Nemo would have been significantly more disturbing. Parrotfish can change sex as well—mostly from female to male. During this transition, the ovaries dissolve and testes are grown. Gut feelings get all the press, but your gut may be more of a thinker than you know. Some scientists now consider it a second brain.