Reproductive Physio 3 Flashcards
Describe the uterus
• A hollow, pear-shaped organ that is responsible for gestation (pregnancy), menstruation, and labour and delivery.
• It functions by nurturing the fertilized ovum, which passes through the fallopian tube and implants into the endometrium, where it receives nourishment from blood vessels, which are exclusively developed for this purpose.
• As the embryo grows and matures, the uterus expands to accommodate the developing foetus.
• During normal labour, the uterus contracts as the cervix dilates resulting in the delivery of the infant.
Differentiate the physiologic variants of the uterus
• The uterus varies in size and shape depending on the reproductive phase of the female and its response to the female sex hormones.
• Pre-pubertal age: Uterus is small, and the cervix is longer than the body. The cervix-to-body ratio is 2:1.
• Reproductive age: Mature size, the body is bigger than the cervix, and the cervix-to-body ratio is 1:2.
• Post-menopausal: The uterus is atrophic, and the body size is smaller than the cervix. The cervix-to-body ratio is 2:1.
Distinguish the layers of the uterus
There are 3 tissue layers.
1. Endometrium:
* The inner lining.
* Consists of the functional (superficial) and basal endometrium.
* The functional layer responds to reproductive hormones.
* When this layer sheds, this results in menstrual bleeding.
* If there is damage to the basal endometrium, this can result in the formation of adhesions and fibrosis (Asherman syndrome).
The endometrium is supplied by two types of arteries.
The superficial two thirds of the endometrium that is shed during menstruation, the stratum functionale, is supplied by long, coiled spiral arteries, whereas the deep layer that is not shed, the stratum basale, is supplied by short, straight basilar arteries
2. Myometrium:
The muscle layer and is composed of smooth muscle cells.
3. Serosa/Perimetrium:
The thin outer layer composed of epithelial cells.
Outline the uterine cycle
Refers to changes within the uterus during the menstrual cycle.
Just as the hormones produced by the granulosa and theca cells of the ovary “drive” the follicular and luteal phases of the ovarian cycle, they also control the 3 distinct phases of the menstrual cycle.
The menstrual (menses) phase
The proliferative phase
The secretory phase
The phases of the menstrual cycle are also named in terms of uterine events.
Day 1 the first day of menstrual bleeding and the entire period of menstruation is known as the menstrual phase, which is generally about 3 to 5 days in a typical 28 day cycle.
During this period, the epithelial lining of the uterus—the endometrium—degenerates, resulting in the menstrual flow.
The menstrual flow then ceases, and the endometrium begins to thicken as it regenerates.
This period of growth, the proliferative phase, lasts for the 10 days or so between cessation of menstruation and the occurrence of ovulation.
Soon after ovulation, the endometrium begins to secrete various substances, so that the part of the menstrual cycle between ovulation and the onset of the next menstruation is called the secretory phase.
Describe the menstrual phase of the uterine cycle
The phase during which the lining is shed.
The days that the person menstruates.
Can last from 2 to 7 days, or longer.
Occurs during the early days of the follicular phase of the ovarian cycle, when progesterone, FSH, and LH levels are low.
Progesterone levels decline as a result of the degradation of the corpus luteum, marking the end of the luteal phase.
This decline in progesterone triggers the shedding of the stratum functionalis of the endometrium
Describe the prolifeative phase of the menstrual cycle
Once menstrual flow ceases, the endometrium begins to proliferate again, marking the beginning of theproliferative phaseof the menstrual cycle.
It occurs when the granulosa and theca cells of the tertiary follicles begin to produce increased amounts of oestrogen.
The rising oestrogen concentrations stimulate the endometrial lining to rebuild
Recall that the high oestrogen concentrations will eventually lead to a decrease in FSH as a result of negative feedback, resulting in atresia of all but one of the developing tertiary follicles.
The switch to positive feedback—which occurs with the elevated oestrogen production from the dominant follicle—then stimulates the LH surge that will trigger ovulation.
In a typical 28-day menstrual cycle, ovulation occurs on day 14.
Ovulation marks the end of the proliferative phase as well as the end of the follicular phase
Describe the secretory phase of the menstrual cycle
In addition to prompting the LH surge, high oestrogen levels increase the uterine tube contractions that facilitate the pick-up and transfer of the ovulated oocyte.
High oestrogen levels also slightly decrease the acidity of the vagina, making it more hospitable to sperm.
In the ovary, the luteinization of the granulosa cells of the collapsed follicle forms the progesterone-producing corpus luteum, marking the beginning of the luteal phase of the ovarian cycle
In the uterus, progesterone from the corpus luteum begins thesecretory phase, in which the endometrial lining prepares for implantation.
Over the next 10 to 12 days, the endometrial glands secrete a fluid rich in glycogen.
If fertilization has occurred, this fluid will nourish the new cells now developing from the zygote.
At the same time, the spiral arteries develop to provide blood to the thickened stratum functionalis.
If no pregnancy occurs, within approximately 10 to 12 days, the corpus luteum will degrade into the corpus albicans.
Levels of both oestrogen and progesterone will fall, and the endometrium will grow thinner.
Prostaglandins will be secreted that cause constriction of the spiral arteries, reducing oxygen supply.
The endometrial tissue will die, resulting in menses—or the first day of the next cycle
What is the relationship between the changes in the evarian and uterine cycles?
What cyclical changes does the cervix undergo?
Although it is continuous with the body of the uterus, the cervix of the uterus is different in a number of ways.
The mucosa of the uterine cervix does not undergo cyclical desquamation, but there are regular changes in the cervical mucus.
Oestrogen makes the mucus thinner and more alkaline, changes that promote the survival and transport of sperms. It is thinnest and most elastic at the time of ovulation.
After ovulation and during pregnancy, it becomes thick (progesterone makes it thick, tenacious, and cellular).
What happens to the mammary glands during the uterine cycle?
During the normal hormonal fluctuations in the menstrual cycle, breast tissue responds to changing levels of oestrogen and progesterone, which can lead to swelling and breast tenderness in some individuals, especially during the secretory phase.
Oestrogens cause proliferation of mammary ducts, whereas progesterone causes growth of lobules and alveoli.
All these changes regress, along with the symptoms, during menstruation.
If pregnancy occurs, the increase in hormones leads to further development of the mammary tissue and enlargement of the breasts.
Although lactation normally does not occur until the end of pregnancy, cyclical changes take place in the breasts during the menstrual cycle.
The breast swelling, tenderness, and pain experienced by many women during the 10 d preceding menstruation are probably due to distention of the ducts, hyperemia, and oedema of the interstitial tissue of the breast.
