You have approximately 1013 cells in your body (human cells, that is – we'll come back to the rest in a few if all of those human cells arose by successive divisions of your original zygote, how many divisions did it take to produce you? determine the integral number of divisions that gives the closest result.

From the zygote cells differentiate by 2^n. Here n is the number of divisions needed to attain the total number of cells.

Here 2^n = 10^13 = 10000000000000

After 10 divisions = 2^n = 1024 (n = 10)

After 20 divisions = 2^20 = 1048576

After 30 divisions = 2^30 = 1073741824

After 40 divisions = 2^40 = 1099511627776

Almost after 43 divisions or 43.3 divisions = 10829260783553

Hence, about 43 divisions are needed to attain 10^13 cells.

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]