The menstrual cycle Flashcards
What is the menstrual cycle?
The monthly process of the maturation of the oocyte
What is Menarche? (1)
The onset of periods
What factor can influence the Menarche? (1)
High body fat percentage - higher levels of Leptin
What phases does the menstrual cycle consist of? (2)
The follicular/ proliferative phase (postmenstrual)
The luteal/ secretory phase (premenstrual)
What hormone triggers the onset of periods?
Leptin - a regulatory hormone of appetite and energy metabolism)
What is the function of the menstrual cycle?
To allow reproduction.
How does Leptin trigger Menarche? (3)
Leptin hormone promotes the stimulation of the hypothalamus = release of GnRH (Gonadatrophin) = promotes release of FSH, LH & Estradiol = ovulation triggered
What is menstruation?
The cyclical activity involving partial shedding of the endometrium.
What is amenorrhea?
The absence of periods.
What is dysmenorrhea?
Painful periods.
What is menopause? (1)
End/ stopping of the menstrual cycle
What is menorrhagia?
Heavy periods.
Roughly what age does menopause occur? (1)
Between the ages 52-55
When does the typical menstrual cycle occur?
Usually, every 21-35 days with an average of 28 days.
When does ovulation take place?
On day 14 of the menstrual cycle.
What happens to the endometrium during menstruation? (1)
The stratum functionalis is discharged through the vagina
On average, how many days will a woman bleed during their menstrual cycle?
5 days
What is the typical volume of blood loss during menstruation?
30-40ml
What is the volume of blood loss that describes menorrhagia?
80ml
What is menstrual loss comprised of?
80% blood
less than 25% endometrial tissue fluid and mucus
What does a primordial follicle consist of? (1)
An oocyte and a single cell layer of granulosa cells
Why does menstrual loss contain minimum fibrinogen?
This is a clotting agent that prevents the blood from clotting.
Where is gonadotrophin released?
The pituitary gland.
What hormone increases as the granulosa cells multiply?
Oestrogen.
What is ovulation?
The process in which the mature oocyte is released from the ovary and taken into the uterine tube.
What are the four main hormones involved in the menstrual cycle? (4)
Follicle stimulating hormone (FSH)
Luteinising hormone (LH)
Oestrogen
Progesterone
Which phase of the menstrual cycle is always 14 days long?
Luteal phase.
What is the role of oestrogen during the menstrual cycle? (3)
To stimulate the uterine blood vessels.
To aid the development of the endometrium
Thinnen cervical mucus to allow sperm to reach egg.
What happens to LH and FSH when oestrogen rises?
They are suppressed.
What hormone does the corpus luteum secrete high levels of?
Progesterone.
If fertilisation takes place, what hormone does the embryo release?
Human chorionic gonadotrophin (HCG)
What hormone maintains the corpus luteum?
Human chorionic gonadotrophin (HCG)
At the start of follicular development, what layer does the cells divide into?
The stromal layer which surrounds the granulosa cells.
What cells forms with the continuum of follicular development?
The theca cells.
Where do the theca cells lie?
Between the granulosa and the stromal cells.
What is the oocyte surrounded by?
The zona pellucida.
What develops from the primordial follicle?
The follicular antrum.
Outline the follicular development
- Primordial follicle - an oocyte and a single layer of cells
- Layer of cells begin to devide and create further layers - over time becoming the granulosa cells, the theca interna and externa and the stromal cells.
The space between the oocyte and the granulosa cells is called the sons pellucida. - The follicular antrum develops and is filled with follicular fluid
- The oocyte is mature - suspended in follicular fluid and attached to the granulosa cell layer by a stalk
- Ovulation occurs - Follicle ruptures to release the ovum - triggers start of luteal phase
What is the follicular antrum filled with?
Follicular fluid.
What is suspended in the follicular fluid of the follicular antrum?
A mature oocyte.
What is the mature oocyte attached to in the follicular antrum?
The granulosa cell layer via a stalk.
What happens at the point of ovulation?
The follicle ruptures to release the oocyte, the corpus luteum is formed.
