THE FEMALE REPRODUCTIVE SYSTEM AND CHILDBIRTH

Hi, my name is Nads the Dog. Today, we aregoing to talk about a subject close to my heart,the female reproductive system!

THE FEMALE REPRODUCTIVE SYSTEM AND CHILDBIRTH

We are going to rationally discuss ovaries, hormones, pregnancy and the menstrualcycle. This is gonna be great!

THE FEMALE REPRODUCTIVE SYSTEM AND CHILDBIRTH

Let’s begin our discussion with the formationof eggs in the ovary. Cool!

A female is born with more than 400,000 eggs in herovaries but they’re immature and cannot be fertilized.Typically, a female will release about 300-400 mature eggs during her reproductive lifetime; averaging 1 every 28 days from the time she reaches puberty to menopause, around 50 years of age. The oldest womanto ever give birth was Mabel Zyeroski of Chicago, who gave birth to a bouncy baby boy at the age of 81.

I heard Mabel was pretty tough for 81. Labor lasted 10 minutes and Mabel smoked the entire time.

FACT: The oldest reported Mom was Rajo Davi,

a woman from India who, at age 70, had a child after IVF (in vitro fertilization) treatment. This treatment is reportedly on the rise in India and other countries as its availability has allowed women to avoid the cultural stigma of being “barren”. Unfortunately, many of these women are now facing health complications and, in fact, some have died.

Immature eggs all begin meiosis, but that process isstalled in prophase I until the female reachespuberty when levels of sex hormones become highenough to complete the maturation of the eggs.regulated by these hormones, 10-20 eggs resume meiosis every 28 days. Typically, however, one mature egg is released each time.

Each female has 2 ovaries. After the egg matures nearthe surface, it is released into the abdominal cavity.What?!? The abdominal cavity!? Yup, the abdominal cavity. The egg is swept into the fallopian tube by theaction of cilia that lines the end of the tubes. This narrow passage leads to the uterus, where cool stuffhappens, like embryonic development. The lower end ofthe uterus is the cervix. A sphincter muscle controlsthe opening of the cervix.

INTERESTING HUMAN FACT

You have 40sphincters in yourbody.

Each month, the female reproductive system preparesitself for pregnancy. Hey, it could happen. This is called the menstrual cycle. For most, this cycle lastsabout 28 days. During this time, an egg matures and enters the fallopian tube, where it could be fertilizedby a sperm. If not, the egg degenerates. This cycle has 4 stages: the follicular phase, ovulation, the lutealphase and menstruation. All of the stages are controlled by hormones.

An immature egg completes its first meiotic divisionduring the follicular phase. This phase begins when the hypothalamus secretes a releasing hormone thatstimulates the anterior lobe of the pituitary gland tosecrete follicle-stimulating hormone (FSH). FSHstimulates cell division in a follicle, a layer of cellsthat surrounds an immature egg. Follicle cells supplynutrients to the egg. They also secrete estrogen, which stimulates growth of the uterine lining, causing it tothicken.

The follicular phase lasts about 14 days. During this time, the estrogen level in the blood continues to rise until it reaches a peak and the egg moves to the surface of the ovary. The elevated estrogen levelstimulates the anterior pituitary to secrete luteinizinghormone (LH), which initiates the next stage of the cycle. This is an example of a positive feedbackmechanism.

Ovulation!! Hurray!!

The rise in LH that occurs around day 14 causes thefollicle to rupture and release the egg. The egg thenis swept into the fallopian tube. The egg can hang for about 48 hours, given its stored nutrients.

The cells of the ruptured follicle grow larger and forma new structure called a corpus luteum. This is the luteal phase of the menstrual cycle. The corpusluteum secretes large amounts of estrogen and progesterone. Progesterone stimulates growth ofblood vessels and storage of fluids and nutrients in thelining of the uterus. This causes the lining to thickenfurther.

In addition, the increased levels of estrogen and progesterone cause the pituitary gland to stop secreting LH and FSH. This is a negative feedbackmechanism. This phase lasts about 14 days.

If the egg is not fertilized, the corpus luteum stopsproducing sex hormones. Without these hormonesto maintain the uterine lining, the lining begins to degenerate and slough off. This is the beginningof menstruation. The lining of the uterus and bloodfrom ruptured blood vessels is discharged throughthe vagina. Menstruation lasts about 5 days at thebeginning of the follicular phase.

Once the woman runs out of follicles, menstruationends. Without follicles, the ovaries cannot secreteenough estrogen and progesterone to continue thecycle. This is menopause.

Hey Kayla, don’t you dig this stuff!? Get it?Dig? Ha ha ha that’s funny!

You know why my name is Nads? Because whenI chase a cat, my master yells, “Go Nads! Go Nads!”

TIME TO GET PREGNANT!!!

So the egg is fertilized in the fallopian tubeand heads on down to the uterus forimplantation. I love that word.

Hey Kody, how many pregnant women doesit take to change a light bulb?

Just one, but you have to stick a pickle inthe socket and smear ice cream on the bulb!HA HA – that’s funny!

FACT Food cravings, like wanting ice cream

and pickles, hasn’t been adequately explained by science. Most physicians agree that these unusual cravings are the result of changing hormone levels, the woman’s nutritional needs and the physical and emotional stress of pregnancy.

If the egg is fertilized, the resulting zygote attachesto the uterine lining where it will develop for the next9 months. A hormone that is produced early in pregnancy stimulates the corpus luteum to continue producing estrogen and progesterone and the uterinelining is maintained. The hormone is produced by thedeveloping placenta and is called human chorionicgonadotropin (HCG).

INTERESTING FACT You know those sticks you pee on to see

if you’re pregnant? You don’t? Good. You shouldn’t know about that yet. But years from now, when you think you’re pregnant and you get one of those sticks and pee on it, the presence of HCG is what is being tested for.

The HCG is produced by the second week of pregnancyin order to maintain the uterine wall. As the placentadevelops, it begins to secrete large amounts ofestrogen and progesterone, which take over the maintenance of the uterine lining from the corpusluteum. Continued production of estrogen and progesterone throughout pregnancy prevents the release of LH and FSH and ovulation will not occur.

TIME FOR BABY!!!

When labor begins, it’s almost baby time. A complexinteraction of hormones and prostaglandins induceand regulate labor. High levels of estrogen trigger theformation of oxytocin receptors on the uterus. Oxytocin,produced by the mother’s posterior pituitary and by thefetus, stimulates strong contractions of the uterus.Oxytocin also stimulates the placenta to secreteprostaglandins, which enhance these contractions. Boyoh boy, can they make Jamie scream!

Physical and emotional stress during labor can also stimulate the release of more oxytocin and prostaglandins, further increasing the contractions.

So, here comes the baby and, man, is it hungry!

Really, if you think about it, breastfeedingis one of the greatest things in the world.

Only mammals can do it – we have the ability toform a vacuum in our mouths thereby producingthe necessary suction to extract the milk from the breast. So, what does this mean?

Mammals suck!

I remember my own breastfeeding days down on the farm. Just me and Mom and my 11brothers and sisters. Good times. Of course, Mom only had 8 nipples so you can imagine the ruckus during lunch time!

FACT While humans have 2 nipples (and

sometimes 3) the number of nipples on dogs can vary between 6 and 10. Some dogs can even have an odd number of nipples!

Lactation is unique to mammals. In response to sucklingby the newborn, the hypothalamus signals the anteriorend of the pituitary to secrete prolactin whichstimulates the mammary glands to produce milk. Sucklingalso stimulates the release of oxytocin which triggersthe release of milk of the mammary glands.