An adult human brain contains over 10^14 (a hundred thousand billion) electrical connections (d), more than all the soldered electrical connections in the world. The human heart, a ten-ounce pump that will operate without maintenance or lubrication for about 75 years, is another engineering marvel (e).
d. “The human brain consists of about ten thousand million nerve cells. Each nerve cell puts out somewhere in the region of between ten thousand and one hundred thousand connecting fibres by which it makes contact with other nerve cells in the brain. Altogether the total number of connections in the human brain approaches 10^15 or a thousand million million. ... a much greater number of specific connections than in the entire communications network on Earth.” Denton, pp. 330–331.
“... the human brain probably contains more than 10^14 synapses ...” Deborah M. Barnes, “Brain Architecture: Beyond Genes,” Science, Vol. 233, 11 July 1986, p. 155.
e. Marlyn E. Clark, Our Amazing Circulatory System, Technical Monograph No. 5 (San Diego: Creation-Life Publishers, 1976).