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How long can an egg survive after it is released in ovulation?

24 hours


What is the source of a positive home pregnancy test?

human chorionic gonadotropin (HCG)
This is secreted by the blastocyst to stimulate the corpus luteum to secrete progesterone, which increases the blood supply to the endometrium. The endometrium secretes glycogen to sustain the blastocyst before implantation.


What are the three layers developed by the blastocyst upon implantation in the endometrium?

The ectoderm is the outer layer
The mesoderm is the middle layer
The endoderm is the inner layer


What body parts develop from each layer?

Ectoderm- skin and nervous tissue
Endoderm- Glands (thyroid, parathyroid, thymus glands), several solid organs (liver and pancreas) and the lining of the hollow organs of digestive and respiratory systems
Mesoderm- all other tissues, including the cardiovascular system, red blood cells and muscle


What is the function of the placenta?

To provide the embryo and fetus in the uterus with nutrition. It is a temporary organ that carries out nutritive,excretory, endocrine and respiratory functions for the embyro. The placenta is attached to the embryo by the umbilical cord.


How many trimesters are there a pregnancy?

1st, 2nd and 3rd Trimesters


What is the length of each trimester?

1st Trimester (0-12 weeks,)
2nd Trimester (13-28 weeks)
3rd Trimester (29-40 weeks)


Highlights from the 1st Trimester

The head is formed but is disproportionately large for the majority of the first trimester. The brain, spinal cord and limbs begin to form. The eyes, ears, and nose begin to form but are not necessarily in their correct location yet. The heart forms and begins pumping blood. By the end of week eight the embryo is now considered a fetus and begins to move, but movement is not yet felt by the mother. Finally, the genitals begin to form.


Highlights from the 2nd Trimester

The eyes, ears, and nose move to the correct position on the face and head and the body is growing to its proper proportion. The fetus begins to suck and blink and fetus’ fingerprints develop. The mother begins to feel the fetus move in the womb. Lanugo or hair develops on the fetus’ body to keep it warm. The fetus develops sleep/wake cycles and the heart beats at a regular pattern.


Highlights from the 3rd Trimester

The third trimester is characterized by continued development of the systems in place. For boys, the testes descend into the scrotum. The baby increases in weight and begins to develop fat under the skin. The lungs continue to develop and the baby begins to regulate its own temperature.


How does the mother's body adapt to pregnancy?

As the baby is growing during pregnancy and changing, so is the mother’s body. The uterus enlarges significantly and fills up the abdominal cavity by the end of pregnancy. The female’s breasts grow and prepare to produce milk for the new baby. The cardiovascular system increases blood volume and the respiratory system increases the respiratory rate. The kidneys increase urine output because of the fetal waste. As the female’s abdomen expands to accommodate the uterus, her center of gravity shifts and causes an increase in lumbar curvature. The pubic symphysis expands and the pelvis ligaments relax and become more flexible to allow room for the baby at delivery. Other common changes during pregnancy are heartburn, morning sickness, and constipation.


1st stage of Delivery

The first stage, dilation of the cervix, is the time it takes for the woman’s cervix to dilate to ten centimeters. During this stage the uterus contracts, which pushes the baby’s head against the cervix causing it to dilate. This stage of labor is the longest, lasting, on average 6-10 hours.


2nd stage of Delivery

The second stage, delivery of the baby, is the time it takes for the baby to be pushed out of the birth canal after full dilation has been accomplished. During this stage a woman uses her abdominal muscles to push the baby, with the help of the uterus contracting, through the cervix and out the vagina. This stage is much shorter, lasting, on average, 50 minutes in a first delivery and 20 minutes in later ones. After the child is born the umbilical cord is tied and cut. Babies are typically born head first but if the baby is in a different position such as a buttock-first (breech), it can cause complications for the mother and child. In breech and other especially long and difficult deliveries, a cesarean section is performed, in which the baby is delivered through a surgical incision made through the abdominal and uterine walls.


3rd Delivery

Delivery of the Placenta- when the placenta is pushed out of the birth canal. This occurs within 15 minutes of the birth of the child and is the shortest part of labor. The entire placenta needs to be removed after birth or uterine bleeding will continue. The placenta is referred to as the afterbirth.


What is oogenesis?

Oogenesis is the production of eggs in the ovaries which occurs during development of the fetus in the womb and is complete by the time of birth. Therefore, at birth a female has all of the immature eggs that she can later ovulate during her reproductive lifetime which extends from puberty to about her 50th year of life. The end of the female reproductive lifetime is known as menopause.


What are the stem cells that become eggs known as? What are the daughter cells called after undergoing mitotic division?

Stem cells, known as oogonia, undergo mitotic division into two daughter cells known as primary oocytes. These primary oocytes are covered by follicles, known as primary follicles. This process is completed by birth.


Primary oocytes are covered by what structures? What are these known by?

Primary oocytes are covered by follicles, known as primary follicles.


What effect does Follicle stimulating hormone have?

In puberty, FSH begins to be secreted by the anterior pituitary gland which causes a few follicles to mature each month.


What happens once FSH is secreted in puberty?

This hormone causes a few follicles to mature each month. The primary oocyte in the follicle undergoes its first meiotic division into two daughter cells: the secondary oocyte and the first polar body.


What happens if the secondary oocyte is united with a sperm after ovulation ?

If the secondary oocyte is united with a sperm after ovulation the second meiotic division occurs which produces a second polar body and an ovum with 23 chromosomes. The ovum and the sperm combine their chromosomes to form a fertilized egg with 46 chromosomes.


What happens to the first polar body produced in the 1st meiotic division?

It may or may not undergo a second meiotic division. Therefore females produce two to three polar bodies and one viable gamete or ovum with 23 chromosomes.


What happens if the secondary oocyte does not combine with a sperm ?

It dies and menstruation occurs.


What action does the Luteinizing hormone perform? What gland is it secreted by ?

Around the time of ovulation the anterior pituitary secretes a second hormone called luteinizing hormone (LH). This causes the follicle to become the corpus luteum which is necessary for maintaining pregnancy.


What is menstruation ?

The shedding of the inner endometrium layer of the uterus if a zygote is not implanted.


How are the ovarian cycle and the menstrual cycle integrated ?

Every month the ovaries release hormones (estrogen and progesterone) that cause changes to the endometrium, the innermost layer of the uterus, which provides the site for implantation if fertilization occurs and if not it is shed (every 28 days).


What are the 3 phases of the menstrual cycle?

the menstrual phase, the proliferative phase, and the secretory phase.


What happens in the menstrual phase of the menstrual cycle?

The menstrual phase begins on day 1 when all but the innermost basal layer of the endometrium is shed and continues through day five. The detached tissue and blood flow from the uterus into the vagina and exit the body via the vaginal orifice as the menstrual flow.


What happens in the proliferative phase of the menstrual cycle?

The proliferative phase occurs during days 6-14 as the endometrium rebuilds in response to increasing estrogen levels. Ovulation of an egg typically occurs in the ovaries on day 14. This is a result of the anterior pituitary release of luteinizing hormone as a response to high levels of estrogen.


What happens in the secretory phase of the menstrual cycle?

The final phase of the cycle is the secretory phase which occurs during days 15-28. During this phase the corpus luteum begins to secrete progesterone. Progesterone causes an increased blood supply in the uterus and secretion of nutrients glycoproteins. This prepares the uterus for implantation if an egg has been fertilized


What happens to the corpus luteum if fertilization does not occur?

the corpus luteum dies and the endometrium’s blood supply decreases as a result of decreased progesterone which begins the menstrual phase again.