THE MENSTRUAL CYCLE

Candidate should be able to describe the menstrual cycle

When a female reaches puberty she usually has a menstrual period every month.

The start of periods is known as menarche.

Menarche doesn't happen until all the parts of a girl's reproductive system have matured and are working together.

This event occurs until the woman reaches menopause

This ‘period’ is apart of a cyclical process which prepares the woman's body for the development of a fertilized egg.

The process is controlled by several hormones.

What is a hormone? A chemical substance produced by an

endocrine gland to coordinate one or more specific processes in the body.

The process is controlled by several hormones.

GONADOTROPIN-RELEASING HORMONE GnRH FOLLICLE STIMULATING HORMONE FSH LEUTENIZING HORMONE LH LUTEOTROPPIC HORMONE OESTROGEN PROGESTERONE

Each month, the ovary releases an egg cell. It travels down the fallopian tube towards the uterus.

The egg matures when FSH from the pituitary gland reaches the ovary.

The mature egg is surrounded by a fluid and a jacket of cells known as the Graafian follicle.

Graafian Folllicle

OVULATION The mature Graafian follicle moves toward the

surface of the ovary and ruptures releasing the egg(ovum) from the follicle and the ovary.

This process, ovulation occurs about the 14th day after the beginning of the menstrual period.

When the ovum is released it enters the oviduct and passes along the oviduct to the uterus

After ovulation, the pituitary gland secretes lutenizing hormone (LH).

LH changes the remains of the follicle into the corpus luteum/yellow body.

Corpus luteum produces the hormone progesterone.

Progesterone further thickens the uterus lining and increases blood supply

If fertilization does occur the corpus luteum enlarges and continues to produce progesterone. The lining of the uterus thickens and blood supply increases.

Progesterone also causes the breast to enlarge.

These are pregnancy changes, progesterone is also known as the ‘pregnancy hormone’.

Both oestrogen and progesterone slow down FSH production when their concentrations become high. Thus no more eggs develop. *negative feedback *

If fertilization does not occur the corpus luteum degenerates to ordinary ovary tissue and the progesterone level falls.

The lining of the uterus breaks down and the egg dies.

Lining along with blood passes out the vagina as the menstrual period.

Cycle continues with increased FSH production and egg development.

Cycle lasts approximately 28days

Normal Menstrual CycleWhat is the mean duration of the MC? Mean 28 days (only 15% of ♀) Range 21-35

What is the average duration of menses? 3-8 days

What is the normal estimated blood loss? Approximately 30 ml

When does ovulation occur? Usually day 14 36 hrs after the onset of mid-cycle LH surge

Menstrual Cramps Menstrual cramps are pains in the abdominal

(belly) and pelvic areas that are experienced by a woman as a result of her menstrual period.

Menstrual cramps can range from mild to quite severe. Mild menstrual cramps may be barely noticeable and of short duration - sometimes felt just as a sense of light heaviness in the belly. Severe menstrual cramps can be so painful that they interfere with a woman's regular activities for several days.

What causes menstrual cramps When the old uterine lining begins to break

down, molecular compounds called prostaglandins are released. These compounds cause the muscles of the uterus to contract. When the uterine muscles contract, they constrict the blood supply to the endometrium.

This contraction blocks the delivery of oxygen to the tissue of the endometrium which, in turn, breaks down and dies. After the death of this tissue, the uterine contractions literally squeeze the old endometrial tissue through the cervix and out of the body by way of the vagina.