Omentum: A double-layered fold of peritoneum that attaches the STOMACH to other organs in the ABDOMINAL CAVITY.Peritoneal Diseases: Pathological processes involving the PERITONEUM.Peritoneal Neoplasms: Tumors or cancer of the PERITONEUM.Surgical Flaps: Tongues of skin and subcutaneous tissue, sometimes including muscle, cut away from the underlying parts but often still attached at one end. They retain their own microvasculature which is also transferred to the new site. They are often used in plastic surgery for filling a defect in a neighboring region.Autografts: Transplant comprised of an individual's own tissue, transferred from one part of the body to another.Poland Syndrome: A syndrome which is characterized by symbrachydactyly and aplasia of the sternal head of pectoralis major.Torsion Abnormality: An abnormal twisting or rotation of a bodily part or member on its axis.Hemangiopericytoma: A tumor composed of spindle cells with a rich vascular network, which apparently arises from pericytes, cells of smooth muscle origin that lie around small vessels. Benign and malignant hemangiopericytomas exist, and the rarity of these lesions has led to considerable confusion in distinguishing between benign and malignant variants. (From Dorland, 27th ed; DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p1364)Peritoneum: A membrane of squamous EPITHELIAL CELLS, the mesothelial cells, covered by apical MICROVILLI that allow rapid absorption of fluid and particles in the PERITONEAL CAVITY. The peritoneum is divided into parietal and visceral components. The parietal peritoneum covers the inside of the ABDOMINAL WALL. The visceral peritoneum covers the intraperitoneal organs. The double-layered peritoneum forms the MESENTERY that suspends these organs from the abdominal wall.Abdominal Cavity: The region in the abdomen extending from the thoracic DIAPHRAGM to the plane of the superior pelvic aperture (pelvic inlet). The abdominal cavity contains the PERITONEUM and abdominal VISCERA, as well as the extraperitoneal space which includes the RETROPERITONEAL SPACE.Abdomen, Acute: A clinical syndrome with acute abdominal pain that is severe, localized, and rapid in onset. Acute abdomen may be caused by a variety of disorders, injuries, or diseases.InkFacial Hemiatrophy: A syndrome characterized by slowly progressive unilateral atrophy of facial subcutaneous fat, muscle tissue, skin, cartilage, and bone. The condition typically progresses over a period of 2-10 years and then stabilizes.