2.2 physiology and health (2) Flashcards
State the location of the endometrium
The endometrium is the lining of the uterus
What happens to the endometrium during the menstrual cycle
During the course of a menstrual cycle the endometrium changes as a result of hormonal signals from the ovary
How many days does it take the endometrium to shed (menstrual cycle 1)
During days 1 to 5 the endometrium is shed – this is the menstrual bleed
How does the endometrium get repaired after its shed (menstrual cycle 2)
Then the endometrium repairs as oestrogen stimulates proliferation from days 5 to 14 preparing it for a possible implantation event
What happens days 14-22 (menstrual cycle 3)
From days 14 to 22, further development and vascularisation of the endometrium is stimulated by progesterone to ensure that it is a thick blood rich layer ready to sustain an implanted embryo
What happens if theyre is no fertilisation (menstrual cycle)
If there is no fertilisation, then from days 22 to 28 the progesterone levels fall and the endometrium starts to break down in preparation for menstruation from days 1 to 5 as the cycle continues.
Identify the two phases of a menstrual cycle
Follicular phase – Days 1 to 14
Luteal phase – Days 15 to 28
Outline the events that occur in the ovaries and endometrium during the follicular phase of the menstrual cycle.
During the follicular phase, a follicle develops in the ovary and oestrogen is secreted. At the start of the follicular phase, the endometrium is being shed (menstruation) and then during the rest of the follicular phase, the endometrium is being repaired (proliferation).
Identify the event that signals the end of the follicular phase and the start of the luteal phase.
The end of the follicular phase is signalled by the process of ovulation when a mature follicle ruptures to release an egg and luteal phase begins.
Outline the events that occur in the ovaries and endometrium during the luteal phase of the menstrual cycle.
(Luteal phase 1)
During the luteal phase, the remains of the Graafian follicle develops into corpus luteum which then starts to secrete progesterone
What happens at the start of the luteal phase of the menstrual cycle
(Luteal phase 2)
At the start of the luteal phase, the endometrium is becoming vascularised to form a thick blood rich layer ready for implantation of an embryo
What happens if there is no pregnancy (Luteal phase 3)
If there is no pregnancy, then in the second half of the luteal phase the corpus luteum starts to degenerate and as the progesterone levels start to fall, the endometrium starts to break down in preparation for the next menstrual bleed at the start of the next follicular phase.
Describe the events involved in the formation of a blastocyst.
If an egg (ova) is successfully fertilised by a sperm, this forms a zygote. The zygote then starts to divide by mitosis creating a ball of cells called a blastocyst.
Describe the process of blastocyst implantation.
As the fertilised egg is undergoing cell division, it continues to travel though the oviduct towards the uterus. By the time the zygote gets to the uterus it has become a blastocyst (ball of cells).
What happens after the uterus becomes a blastocyst (Blasctocyst implantation 2)
The blastocyst will then implant into the blood rich endometrium lining the uterus
What happens during this process (blastocyst implantation 3)
During this process of implantation, the blastocyst grows blood vessels into the endometrium forming chorionic villi. These structures are the initial
stages in the formation of a placenta to allow exchange of materials between the maternal blood supply and the foetal blood supply.
What causes negative feedback effect on ovarian hormones
High levels of progesterone (ovarian hormone) act on the pituitary gland inhibiting the secretions of FSH and LH (the pituitary hormones).
Whats the purpose of negative feedback control (nfc in ovarian hormones)
The purpose of this negative feedback effect is to prevent the development of further follicles while there is the possibility of a successful fertilisation and implantation.
What happens when a pregnancy occurs (nfc on ovarian hormones)
If a pregnancy occurs, then this inhibition of FSH and LH continues as the corpus luteum does not degenerate and then the developing placenta takes over the secretion of progesterone.
What happens if there is no fertilisation (nfc ovarian hormones)
If there is no fertilisation, then the corpus luteum will start to degenerate and progesterone levels will fall. This removes the inhibition of the pituitary gland and so secretions of FSH and LH trigger the development of a new follicle in the ovaries starting a new menstrual cycle.
How long does a typical menstrual cycle take
approximately 28 days
What days does menstruation take
typically day 1 to 5
what days does the follicular phase take
typically occurs from day 1 to day 14 where levels of oestrogen are increasing.
What days does the menstrual cycle take place
around the mid-point, day 14, of the menstrual cycle where LH is at its peak levels
What days does the Luteal phase typically occur
day 14 to day 28.
When does the develpoment of the corpus luteum occur
Development of the corpus luteum occurs after ovulation, typically from days 14 to 22 accompanied by an increase in progesterone levels.
What days does the corpus luteum start to degenerate
The corpus luteum starts to degenerate at around day 22 in a typical cycle leading to a decline in progesterone levels.
