dilation

first stage of childbirth, involving an increase in cervical diameter

dominant

describes a trait that is expressed both in homozygous and heterozygous form

dominant lethal

inheritance pattern in which individuals with one or two copies of a lethal allele do not survive in utero or have a shortened life span

ductus arteriosus

shunt in the pulmonary trunk that diverts oxygenated blood back to the aorta

ductus venosus

shunt that causes oxygenated blood to bypass the fetal liver on its way to the inferior vena cava

ductus deferens

(also, vas deferens) duct that transports sperm from the epididymis through the spermatic cord and into the ejaculatory duct; also referred as the vas deferens

dehydration

state of containing insufficient water in blood and other tissues

dihydroxyvitamin D

active form of vitamin D required by the intestinal epithelial cells for the absorption of calcium

detrusor muscle

smooth muscle in the bladder wall; fibers run in all directions to reduce the size of the organ when emptying it of urine