11. memory t cells (select all that apply.) a. must all be activated in secondary lymphoid organs b. do not require co-stimulation through cd28 c. are composed only of cd4 t cells d. do not undergo somatic hypermutation e. are usually short-lived f. do not undergo isotype switching.

Activated by the binding of an antigen to a specific matching receptor on its surface, a B cell proliferates into a clone.

"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."