Papillary muscles are the muscles that project out from the walls of the ventricles of the heart. These muscles are attached to the AV valves with the help of chordae tendineae. During the contraction of ventricles, the higher blood pressure closes the AV valves by driving the edges of these valves towards each other. At this time, the contraction of Papillary muscle pulls on and makes the chordae tendineae rigid and right. This does not allow the cusps of the AV valves to ever into the atria in the response to higher blood pressure in ventricles.
On day one the levels of oestrogen and progesterone are low, having dropped quickly at the end of the last cycle. Low oestrogen level causes FSH release from the pituitary gland.
