Biology: The Menstrual Cycle

What is happening in the Uterus during the Luteal Phase

The uterine lining is thickening.

How STDs are transmitted

Through sexual contact.

What is happening in the Brain in regard to hormones during the Luteal Phase

(Luteinizing Hormone [LH], Follicle-stimulating Hormone [FSH], Estrogen, and Progesterone) and cells effected by those hormones

What is happening in the Brain in regard to hormones during the Follicular Phase

(Luteinizing Hormone [LH], Follicle-stimulating Hormone [FSH], Estrogen, and Progesterone) and cells effected by those hormones.

Ovaries

1. Produce eggs through the process of meiosis. 2. Produce female sex hormones (estrogen & progesterone) (the follicular phase , ovulation, and the luteal phase all happen here)

Uterus

1. The main body of the uterus can easily expand to hold a developing baby and contract to push that baby out 2. The lining (called the endometrium) thickens to prepare for an embryo or leaves the body during menstruation.

Follicular Phase

Estrogen and progesterone at this point are low In response, the hypothalamus sends a chemical signal to the pituitary gland telling it to release FSH (follicle stimulating hormone) and LH (lutenizing hormone). FSH & LH go through the blood stream to the ovaries and cause a follicle to mature When the follicle begins to mature it releases increasing amounts of ESTROGEN into the bloodstream. Estrogen causes the uterine lining to thicken in preparation for a fertilized egg. The egg matures (in response to FSH & LH) and the uterine lining begins to thicken (in response to estrogen).

Oocyte

Oocytes are immature egg cells. Oocytes remain immature until the female hits puberty

What is happening in the ovaries during the Luteal Phase

The corpus luteum is a wound on the side of the ovary, secreting estrogen and progesterone.

What is happening in the ovaries during the Follicular Phase

The egg is maturing. The corpus luteum is releasing low amount of E and P.

What is happening in the ovaries during ovulation

The egg is released.

Oxytocin

Causes the joints and ligaments to loosen, starting at about 4 months. Initiates labor. (produced after Fertilization)

Prolactin

Causes the production of milk to start (occurs in the mammary glands). Takes about 3 days for the milk to be formed after birth. For first day or two, baby drinks colostrum (form of milk w/many benefits to baby). (produced after Fertilization)

Follicle

Inside the ovaries, a follicle is a collection of cells that includes an immature egg (an oocyte), as well as supporting cells that support the immature egg (metabolic support, secrete hormones, etc.)

What is happening in the uterus during the Follicular Phase

Menstruation and the uterine lining beginning to thicken.

Progesterone

Produced by the corpus luteum and follicle cells. Causes the uterine lining to thicken.

Estrogen

Produced by the corpus luteum in the ovary by follicle cells that surround the egg. Makes the endometrium (uterine lining) thicken (high levels=thicken, low levels=lining sheds). High estrogen levels cause LH to rise.

FSH (Follicle Stimulating Hormone)

Produced by the pituitary gland. It stimulates follicles to produce an egg.

LH

Produced by the pituitary gland. Makes eggs mature. Causes eggs to be released (ovulation).

Ovulation

This spike in LH level (on about day 13) causes the release of egg or OVULATION, on about day 14. This is when the egg is released from the ovary. The follicle near the edge of the ovary pops open and the egg comes oozing out-- causing a crater/wound on the side of the ovary to be formed.

Important Note

The follicular phase, ovulation, and the luteal phase refer to what is happening in the ovary during the 28 days in response to FSH/LH. Menstruation is a term that refers to what is happening in the uterus in response to estrogen/progesterone.

Menstruation

If No fertilization of the egg occurs in the fallopian tubes, the egg deteriorates when it arrives at uterus. Since fertilization did not occur, no hormones from the zygote are sent to the corpus luteum to continue hormone production, so progesterone & estrogen levels drop rapidly. The corpus luteum on the side of the ovary heals into the corpus albacans (white body) the cycle starts all over again with the secretion of FSH/LH by the pituitary gland. (Stage 4a) (Part of the Follicular Phase, approximately the first 5-7 days)

Menstrual Cycle

Regulated by hormones made by hypothalamus, pituitary gland, and ovaries. 4 hormones: FSH, LH, estrogen, progesterone. Typical length is 28 days. Four Stages: follicular phase, ovulation, luteal phase, menstruation. Begins at puberty; ends at menopause.

Corpus luteum

Releases estrogen and progesterone (more progesterone). Another name is yellow body. (is maturing days 15-23)

Pituatary Gland

Sends signals to the corpus luteum to release estrogen and progesterone. Located underneath the hypothalamus.

Fertilization

The egg meets up with a sperm in the fallopian tube and a zygote is formed. Some of the dividing cells form the embryo, others form the placenta and amniotic sac. The cells forming the placenta send hormones to the corpus luteum. The corpus luteum does not heal, so the progesterone and estrogen levels stay high for 40 weeks until the baby is born. (Levels stay high because the corpus luteum does not heal) (Stage 4b)

Luteal Phase

The egg which was released moves through the fallopian tube. The cells from the follicle left on the side of the ovary change and become the corpus luteum ("yellow body")—they continue to produce estrogen and now also produce the hormone progesterone. progesterone causes the uterine lining to thicken further and increases the blood supply in anticipation of a fertilized egg The chance for fertilization of the egg is greatest during the first 2 days of the luteal phase. One egg is released every month (approximately). Normally, the ovaries take turns in releasing eggs. The first month one ovary releases an egg, then the next month the other ovary releases an egg. Each egg travels from the ovary, down a fallopian tube, to the uterus. Fertilization takes place in the fallopian tube.

Hypothalamus

The hypothalamus sending a chemical signal to the pituitary gland telling it to release FSH and LH. This is caused by low FSH and LH levels.