The Menstrual Cycle

The Menstrual Cycle

Hormones

Four hormones involved in controlling menstruation.  

  • FSH
  • Oestrogen
  • LH
  • Progesterone
FSH (follicle stimulating hormone) and LH ( Luteinising hormone) these hormones are released from pituitary gland in the brain. They help to control the mestural cycle. Function of FSH is stimulates one egg cell to develop and stimulates the ovaries to produce oestrogen. Function of LH is stimulate the release of an egg at day 14 (ovulation). 

Oestrogen
  • Causes the lining of the uterus to thicken and grow.
  • Stimulates the production of LH.
  • Inhibits the production of FSH so that only one egg is released in each cycle. 
Progesterone
  • Maintains the lining of the uterus. when the level of progesterone falls and there's a low oestrogen level, the lining breaks down.
  • Inhibits the production of FSH and LH.
  • A low progesterone level allows FSH to increase and then the whole cycle starts again.
The Cycle

The mestrual cycle has four stages

Stage 1 Day 1 is when menstruation starts. The uterus lining breaks down and is released.
Stage 2 The lining of the uterus builds up again, from day 4 to 14, into a thick spongy layer full of blood vessels ready to receive a fertilised egg.
Stage 3 An egg develops and is released from an ovary (ovulation) at about day 14.
Stage 4The lining is then maintained for about 14 days, until day 28. If no fertilised egg has implanted into the uterus wall by day 28, the spongy lining starts to break down again and the whole cycle starts over.




Comments

Post a Comment

Popular posts from this blog

Movement of water through plants (Xylem)

Image
Movement of water through plants  (Xylem) ARRANGEMENT OF XYLEM IN ROOTS ARRANGEMENT OF XYLEM IN STEMS ARRANGEMENT OF XYLEM IN LEAVES ROOT HAIR CELLS INCREASE SURFACE AREA The increased surface area means that water can be absorbed faster from the soil. TRANSPIRATION Transpiration is the loss of water vapour from leaves which causes water molecules to be pulled upwards through the roots, stem and leaves. The water is needed for photosynthesis and to keep plant cells turgid (full) which supports the plant and prevents it from wilting.  WHAT HAPPENS IF A PLANT DOES NOT HAVE ENOUGH WATER? • The plant wilts as the cells are no longer turgid. • As cells are not turgid stomata close to prevent further water loss. • The drooping leaves reduces their surface area which helps to reduce water loss. • Plants may overheat when they do not have enough water. • Plants will stay wilted until they receive enough water. http...
Read more