In which body system did scientists find the polio virus before it entered the nervous system?

The Digestive System

Explanation: Polio first enters the body through the mouth, usually through contact between people. The infected person can spread it through their nasal and oral secretions (mucous and saliva) as well as through their infected contaminated fecal matter (stool from bowel movement), in cases of lack of hygiene. Once the polio virus is in the digestive tract, it multiplies quickly, then enters the blood, and ends up in the nervous system. From there, it attacks the spine leading to paralysis.

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.