Gastrointestinal tract
The small intestine begins at the duodenum and is a tubular structure, usually between 6 and 7 m long. Its mucosal area in an adult human is about 30 m. Its main function is to absorb the products of digestion (including carbohydrates, proteins, lipids, and vitamins) into the bloodstream. There are three major divisions:
Human sexuality
The male genitalia are the penis and the scrotum. The penis provides a passageway for sperm and urine. An average-sized flaccid penis is about in length and in diameter. When erect, the average penis is between to in length and in diameter. The penis's internal structures consist of the shaft, glans, and the root.