þvagrás

The þvagrás, also known as the urethra, is a tube that connects the urinary bladder to the outside of the body. It is a crucial part of the urinary system in both males and females, responsible for expelling urine from the body. The length and structure of the þvagrás differ significantly between sexes. In females, the þvagrás is shorter, typically around 3-4 centimeters long, and opens anterior to the vaginal opening. In males, the þvagrás is considerably longer, about 20 centimeters, and serves a dual purpose as it also carries semen during ejaculation. This dual function in males means the þvagrás passes through the prostate gland and the penis. The internal lining of the þvagrás is made of stratified squamous epithelium, which changes to pseudostratified columnar epithelium in the longer portions, and then back to stratified squamous epithelium near the external opening. This structure helps protect the urethra from infection and trauma. Muscles surrounding the þvagrás, specifically the internal and external urethral sphincters, control the flow of urine. The internal sphincter is involuntary, while the external sphincter is voluntary, allowing conscious control over urination.