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Pancreas 
Gland that produces enzymes essential to the digestion of food. The islets of Langerhans within the pancreas secrete insulin into the blood.
Pancreatitis
Inflammation of the pancreas caused by alcohol, disease in the gallbladder, or virus.
Parenteral
Administered intravenously or by injection. 
Parietal Cells
Cells in the stomach wall that make hydrochloric acid.
Pathogenesis
the origin and development of a disease. 
Pepsin
An enzyme in the stomach that breaks down proteins.
Peptic
Related to the stomach and the duodenum, where pepsin is present.
Peptic Ulcer
A sore in the lining of the esophagus, stomach, or duodenum. An ulcer in the stomach is a gastric ulcer; an ulcer in the duodenum is a duodenal ulcer.
Percutaneous
Passing through the skin.
Perforated Ulcer
A hole in the wall of an organ.
Perianal
The area around the anus.
Peripheral neuropathy
Nerve damage, usually affecting the feet and legs; causing pain, numbness, or a tingling feeling. 
Peripheral vascular disease (PVD)
Disease in the large blood vessels of the arms, legs, and feet.  The signs of PVD are aching pains in the arms, legs, and feet and foot sores that heal slowly. 
Peristalsis
A wavelike movement of muscles in the GI tract that moves food and liquid through the GI tract.
Peritoneum
The lining of the abdominal cavity.
Peritonitis
Infection of the peritoneum.
Pernicious Anemia
Anemia caused by a lack of vitamin B12. The body needs B12 to make red blood cells.
Peutz-Jeghers Syndrome
An inherited condition. Many polyps grow in the intestine.
Pharynx
The space behind the mouth. Serves as a passage for food from the mouth to the esophagus and for air from the nose and mouth to the larynx.
Pituitary gland
a pea-sized structure, which secretes many important hormones, located behind the hypothalamus. The pituitary serves the body in many ways-in growth, in food use, and in reproduction.
Plaque
Is a swelling on the inner surface of an artery produced by lipid deposit.
Pneumonitis
inflammation of the lungs
Polyarthritis
inflammation of several joints at the same time
Polydipsia
Raging thirst that lasts for long periods of time.
Polymyositis
A rheumatic disease that causes weakness and inflammation of muscles.
Polyp
Bulging tissue from the surface of an organ. People who have polyps in the colon may have an increased risk of colorectal cancer.
Polyphagia
Great hunger.
Polyunsaturated fats
A type of fat that comes from vegetables.
Polyuria
Having to urinate often.
Portal Hypertension
High blood pressure in the portal vein. This vein carries blood into the liver. Portal hypertension is caused by a blood clot.
Portal Vein
The large vein that carries blood from the intestines and spleen to the liver.
Portosystemic Shunt
An operation to create an opening between the portal vein and other veins around the liver.
Preeclampsia
development of hypertension in pregnansy, accompanied by swelling of feet and proteinuria
Primary Biliary Cirrhosis
A chronic liver disease. Destruction of the bile ducts in the liver prevents release of bile.
Proctalgia Fugax  
Intense pain in the rectum that occasionally happens at night. Caused by muscle spasms around the anus.
Proctectomy
An operation to remove the rectum.
Proctitis
Irritation of the rectum.
Proctocolectomy
An operation to remove the colon and rectum. Also called coloproctectomy.
Proctocolitis
Irritation of the colon and rectum.
Proctoscopy
Looking into the rectum and anus with a proctoscope.
Proctosigmoidoscopy
An endoscopic examination of the rectum and sigmoid colon.
Prolapse
A condition that occurs when a body part slips from its normal position.
Proliferative Retinopathy
A disease of the small blood vessels of the retina of the eye. 
Prophylaxis
prevention of disease.
Protein
Proteins are made of amino acids, which are called the building blocks of the cells.  
Proteinuria
Too much protein in the urine.
Proton Pump Inhibitors
Medicines that stop the stomach's acid pump. 
Prune Belly Syndrome
A condition of newborn babies. The baby has no abdominal muscles, so the stomach looks like a shriveled prune. Also called Eagle-Barrett syndrome.
Pruritus
Itching skin.
Pruritus Ani
Itching around the anus.
Psoriatic arthritis
Joint inflammation that occurs in about 5 to 10 percent of people with psoriasis (a common skin disorder).
Pulmonary Embolism (PE)
The occlusion of the pulmonary artery or one of its branches by an embolus
Pyloric Stenosis
A narrowing of the opening between the stomach and the small intestine.