Disorders of the Digestive and Circulatory Systems

Two systems, many ways to go wrong

Heart disease is the second leading cause of death in Canada, after cancer. Digestive disorders are rarely deadly but affect millions of Canadians' daily lives, and Canada has one of the highest rates of inflammatory bowel disease in the world, according to Crohn's and Colitis Canada. In this lesson you'll use your knowledge of anatomy to explain what goes wrong, and you'll look at how scientists figured out the cause of one very common disorder.

Peptic ulcers

A peptic ulcer is an open sore in the lining of the stomach or duodenum, where acid and pepsin have eaten through the protective mucus and lining. It can cause burning pain, and serious ulcers can bleed or even make a hole through the wall.

For much of the 20th century, doctors blamed ulcers mainly on stress and spicy food. Then in the early 1980s, two Australian scientists, Barry Marshall and Robin Warren, found a spiral bacterium, Helicobacter pylori, in the stomachs of most ulcer patients. Many experts doubted that bacteria could survive stomach acid. To test it, Marshall **drank a culture of H. pylori** himself in 1984; within days he developed stomach inflammation (gastritis), and the bacteria were found in his stomach. Further studies showed that killing H. pylori with antibiotics cured most ulcers for good. Marshall and Warren won the 2005 Nobel Prize in Physiology or Medicine.

Today we know the two main causes are ***H. pylori* infection and long-term use of NSAIDs (anti-inflammatory pain relievers such as ASA and ibuprofen), which reduce the stomach's protective mucus. Stress and spicy food can worsen symptoms but are not the main causes. Treatment: antibiotics** (for H. pylori) plus medicines that reduce acid so the lining can heal.

Other digestive disorders

• Heartburn and GERD: when the lower esophageal sphincter doesn't close well, stomach acid flows back up into the esophagus, which has no thick mucus protection. Frequent, long-term reflux is called gastroesophageal reflux disease (GERD).
• Inflammatory bowel disease (IBD): long-term inflammation of the digestive tract, caused by an abnormal immune response (genes, gut microbes and environment all seem to play a part). Ulcerative colitis affects the lining of the colon and rectum, in one continuous stretch. Crohn's disease can affect any part of the tract, in patches, and can involve the whole thickness of the wall. Symptoms include diarrhea (sometimes with blood), abdominal pain, tiredness and weight loss. Treatment includes medicines that calm the immune response and sometimes surgery.
• Celiac disease: an autoimmune reaction to gluten (a protein in wheat, barley and rye) damages and flattens the villi, so fewer nutrients are absorbed. Treatment is a strict gluten-free diet, after which the villi can recover.
• Constipation: when material moves too slowly through the large intestine, too much water is absorbed, and stool becomes hard and difficult to pass. Common causes are low-fibre diets, too little fluid, inactivity, ignoring the urge to go, and some medicines. Prevention: fibre (vegetables, fruit, whole grains, legumes), plenty of water, and physical activity. Diarrhea is the opposite: material moves too fast (or the intestine secretes extra fluid), so too little water is absorbed.
• Gallstones: cholesterol or bile pigments crystallize in the gallbladder. A stone blocking the bile duct causes pain, often after a fatty meal (when CCK makes the gallbladder contract).
• Appendicitis: a blocked, inflamed appendix. Pain often starts around the belly button and moves to the lower right abdomen. It is a medical emergency, usually treated by surgery.

Arteriosclerosis and atherosclerosis

Arteriosclerosis is the general hardening and thickening of artery walls; they lose their elasticity, so they can't stretch and recoil with each heartbeat, and blood pressure rises. The most common and dangerous form is atherosclerosis:

1. The smooth inner lining (endothelium) is damaged, for example by high blood pressure, smoking or high blood sugar.
2. LDL cholesterol ("bad" cholesterol) enters the wall at the damaged spot. White blood cells move in to engulf it, and inflammation follows.
3. Fat, cholesterol, cells and later calcium build up into a plaque under the lining, narrowing the lumen.
4. A narrowed artery carries less blood. If a plaque ruptures, platelets rush to the site and a clot forms, which can block the artery completely.

Risk factors: smoking or vaping nicotine, high blood pressure, high LDL cholesterol, diabetes, physical inactivity, obesity, excessive alcohol, stress, increasing age, and family history. Most of the first group can be changed.

What atherosclerosis leads to

• Coronary artery disease: narrowed coronary arteries can't supply enough oxygen when the heart works harder, causing angina: chest pain or pressure during exertion that eases with rest.
• Heart attack (myocardial infarction): a clot blocks a coronary artery, and the heart muscle beyond the block starts to die. Warning signs include chest pain, pressure or discomfort; pain spreading to the arms, neck, jaw or back; shortness of breath; sweating; nausea; and light-headedness. Signs can be less obvious, especially in women. Call 9-1-1 right away: treatment that reopens the artery (clot-dissolving drugs, or a balloon and stent) saves heart muscle. Time is muscle.
• Stroke: blood flow to part of the brain is blocked by a clot (ischemic stroke) or a blood vessel bursts (hemorrhagic stroke). Heart & Stroke's FAST signs: Face drooping, Arm weakness, Speech difficulty, Time to call 9-1-1.
• Hypertension both causes and is worsened by arteriosclerosis.

Heart attack vs cardiac arrest

These are often confused:

• A heart attack is a circulation ("plumbing") problem: a blocked coronary artery. The person is usually awake and breathing, often in pain.
• Cardiac arrest is an electrical problem: the heart's rhythm becomes chaotic (often ventricular fibrillation) or stops, so the heart stops pumping. Within seconds the person collapses, is unresponsive and is not breathing normally. Without help, death follows within minutes.

A heart attack can trigger cardiac arrest, but cardiac arrest also has other causes. Response to cardiac arrest: call 9-1-1, start CPR (hard, fast chest compressions in the centre of the chest), and use an AED (automated external defibrillator) as soon as one is available. An AED analyzes the rhythm and, if needed, delivers a shock that can reset it; it gives spoken instructions, so anyone can use one. Many arenas, schools, community centres and malls in Ontario have AEDs.