Menstrual cycle, Biology

MENSTRUAL CYCLE -

It occurs only in Primates. Start at the age of 13 yrs. upto menopouse.

During this period, generally one egg is released every 28 dyas or so alternately from the two ovaries. Since the female is fertile for about 32 years and about 13 eggs mature each year, only about 466 eggs have a chance of reaching maturity.

Menstrual cycle consists of 3 phases.

1.       FOLLICULAR (PROLIFERATING) PHASE -

It lasts for about 14 days.

It comprises the following events -

1.       Level of FSH is increased in the blood early in the cycle.

2.       FSH stimulates the grwoth of the selected primary ovarian follicle.

3.       FSH stimulates follicle to secrete estradiol.

4.       Estradiol inhibit secretion of FSH & stimulate secretion of LH.

5.       LH induces graffian follicle to burst & eject its egg in to fallopian tube. It occurs after about 14 days.

6.       Estradiol stimultes the uterus to prepare for implantation & nourishment of foetus.

7.       Lining of fallopian tube becomes thick to move ova into uterus.

2.       LUTEAL OR SECRETORY PHASE -

This phase lasts for 10 days. It involves following events -

1.       LH stimulates graffian follicle to convert into corpus luteum.

2.       Corpus luteum secretes progesteron and little amount of estradiol.

3.       Progesteron inhibits the release of FSH so that it may not develop additional follicle & eggs.

3.       MENSTRUAL OR BLEEDING CYCLE -

It lasts about for 4 days.

It involves following events -

(i) If fertilization does not occur, secondary oocyte undergoes autolysis.

(ii) In some wall of uterus secretes a luteolysine. It reaches to ovary where it causes autolysis of corpus luteum.

(iii) Stratum functionalis of endomatrium is given out with bleeding.

(iv) Menstrual flow continues for 3-5 days.

(v) Endomatrium tissue, unfertilised egg & 500-600 ml of blood are lost during this period.

Menstural is often described as funeral of unfertilized egg or weeping of uterus for the last ovum.

Posted Date: 10/3/2012 6:01:54 AM | Location : United States







Related Discussions:- Menstrual cycle, Assignment Help, Ask Question on Menstrual cycle, Get Answer, Expert's Help, Menstrual cycle Discussions

Write discussion on Menstrual cycle
Your posts are moderated
Related Questions
Is there anything I can do to keep my brain healthy in older age? It is increasingly clear that how we live our lives on a daily basis strongly influences how well our brain ag

Maintain nutrition Your responsibility as a nurse is to take care of nutrition and prevent the child from starvation. Breast feeding'should be continued during the diarrhoea e

Q.Explain Chemical changes due to spoilage A food item may have apparently looked safe and wholesome for you to eat, but the rumbling and grumbling in your stomach at night may

What is the production of RNA called and what is the enzyme that catalyzes the process? The making of RNA from information included in DNA is called transcription. The enzyme t

how the gall bladder develops in a trnsplanted liver tissue ?

How is the respiratory system in aquatic molluscs divided? What adaptive respiratory structure do terrestrial molluscs present? Aquatic molluscs oxygenate their blood through g

what is the composition of urine in fishes and reptiles ?

Global Air Circulation The major wind systems of the earth result because large masses of air around the earth's equator are forced to rise from the bottom due to surface heati

Question 1. State the basic properties of light. Discuss the special features of ultra-microscopy and phase contrast microscopy 2. What are ultrasonic waves? Explain the dif

Functions of cerebrum The forebrain is otherwise called as ‘cerebrum'. It is highest centre for controlling several functions in the body, The most interesting aspect