rugae

Rugae, plural of ruga, are ridges or folds formed by mucous membranes. The term derives from Latin for wrinkles. In human anatomy, rugae occur in various hollow or expandable organs, where they permit distension and increase surface area while maintaining tissue integrity.

Major examples include gastric rugae, the transverse folds of the stomach's mucosa that allow the organ to expand after eating; palatal rugae, irregular transverse ridges on the hard palate behind the incisors; vaginal rugae, transverse folds in the vaginal mucosa; and vesical rugae, mucosal folds inside the urinary bladder that flatten as the bladder fills.

Functionally, rugae provide elasticity and increase surface area. They enable the stomach to accommodate food and gastric contents, and they permit distension of the bladder and vagina as they stretch during filling and childbirth.

Clinical notes: Palatal rugae patterns are relatively stable and have been used in forensic dentistry for individual identification. In the stomach, rugae are a normal feature of anatomy that changes with distension; their appearance can be influenced by physiological state but is not diagnostic on its own.