Normally menstruation occurs when ________.
A) blood levels of FSH fall off
B) blood levels of estrogen and progesterone decrease
C) blood levels of estrogen and progesterone increase
D) the corpus luteum secretes estrogen
B) blood levels of estrogen and progesterone decrease
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The ________ is the connective tissue covering around a single muscle fascicle.
Fill in the blank(s) with the appropriate word(s).
ohn, a 72-year-old grandfather, had been smoking heavily for 24 years and had a persistent cough. A biopsy of his lung tissue revealed considerable amounts of carbon particles. How could this happen considering the natural cleaning mechanism of the respiratory system?
What will be an ideal response?
The heart valves open and close due to
a. attachment to the heart muscle. b. a pressure difference on the two sides of the valve. c. Na+ and K+ fluxes during ventricular depolarization. d. turbulent flow in the atria and ventricles. e. none of these answers.
Equal amounts of two solutes, A and B, are placed into the same beaker of water at the same time. Solute A reaches diffusion equilibrium faster than solute B. What is the most likely explanation for this observation?
A. The temperature was greater for solute A than solute B. B. The concentration gradient for A was greater than B. C. Solute A is smaller than solute B. D. Solute A traveled a shorter distance than solute B. E. Solute B is more soluble in water than solute A.