Small intestine
It is approximately 1.5 cm in diameter in newborns after 35 weeks of gestational age, and 2.5–3 cm (1 inch) in diameter in adults. On abdominal X-rays, the small intestine is considered to be abnormally dilated when the diameter exceeds 3 cm. On CT scans, a diameter of over 2.5 cm is considered abnormally dilated. The surface area of the human small intestinal mucosa, due to enlargement caused by folds, villi and microvilli, averages 30 square meters.
Spongy urethra
The spongy urethra runs along the length of the penis on its ventral (underneath) surface. It is about 15–16 cm in length, and travels through the corpus spongiosum. The ducts from the urethral gland (gland of Littre) enter here. The openings of the bulbourethral glands are also found here. Some textbooks will subdivide the spongy urethra into two parts, the bulbous and pendulous urethra. The urethral lumen runs effectively parallel to the penis, except at the narrowest point, the external urethral meatus, where it is vertical. This produces a spiral stream of urine and has the effect of cleaning the external urethral meatus. The lack of an equivalent mechanism in the female urethra partly explains why urinary tract infections occur so much more frequently in females.