Understanding the Menstrual Cycle: Hormones, Phases, and Disorders, Lecture notes of Nursing

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THE MENSTRUAL CYCLE

Presented By

John Brito Mary

Associate Professor

INTRODUCTION

 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 Menopause is the permanent cessation of menses.

INTRODUCTION

 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.

 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.

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 14 th 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 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 Cycle

What 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

Hypothalamus Pitutary gland Follicle stimuating hormone & LH Maturation of follicles Estrogen hormone Lining of the uterus to thicken Leutenizing hormone Results in ovulation stimulates secrets causes Follicle releases causes Pitutary releases Mature follicle burst PATHOPHYSIOLOGY

Menstrual Cycle

 The Menstrual Cycle can be divided into 3 Phases.

• Follicular (Preovulatory) Phase
• Ovulatory Phase
• Luteal (Postovulatory) Phase

Ovulatory Phase

Lasts for 16 to 32 hours

Phase begins when the level of LH surges. LH stimulates dominant follicle to bulge from the surface of ovary and finally rupture, releasing the Egg. Egg travel to Fallopian Tube. This is the time when the women is most likely to become Pregnant. The Egg can be fertilized for only up to about 12 hours after its release.

Luteal Phase, Day 15- 28

After releasing Egg this empty Follicle develops the structure called Corpus Luteum (CL) CL secrets increasing amount of Progesterone. CL prepares Uterus in case fertilization occurs. Progesterone causes the Endometrium to thicken If Egg is Fertilized If Egg is not Fertilized The embryo produces Human Chorionic Gonadotropin (hCG) which will be detected by CL and this Human Chorionic Gonadotropin maintains CL and its Progesterone secretion. The egg moves to the uterus and attaches itself to the endometrium about six or seven days after ovulation, where it begins to develop into a fetus. CL destroys after 14 days an new Menstrual Cycle begins