Digestive System Anatomy/Physiology
Anatomy of the Digestive System:
_____ tract (alimentary canal) = continuous tube running through the ventral body cavity, mouth to anus
Accessory structures, Teeth, Tongue, Salivary glands, Liver, Gallbladder, Pancreas
Digestive Process:
Ingestion
Movement = ______
Secretion (water, HCl, buffers, enzymes)
Digestion = process of breaking down large food particles into molecules which are small enough to enter body cells
Mechanical digestion = chewing, churning, mixing with secretions
Chemical digestion = series of catabolic (hydrolysis) reactions that break down large carbohydrates, lipid, & protein food particles into smaller molecules that can be used by body cells
Absorption = moving these nutrient molecules from GI tract into blood / lymph
Defecation = emptying of the rectum, to remove indigestible substances
Mouth = buccal cavity
Uvula = muscular process which hangs from the back of the soft palate
Tongue = forms the floor of the oral cavity
Salivary glands
Saliva = continuous secreted into the mouth; increased amount of saliva secreted with presence of food in mouth / nervous stimulation, Lubricates; keeps oral and pharyngeal membranes moist, Helps to dissolve food, Starts chemical digestion of ______(contains the enzyme amylase)
3 pairs of major salivary glands: parotid, submandibular, sublingual
Esophagus = muscular tube behind the trachea; connects pharynx to stomach
Moves the bolus by peristalsis; ___ chemical digestion
Esophagus contains upper and lower esophageal sphincters
Stomach
Shaped like a “J” = stomach is just a wide place in the GI tract
4 main regions:
Cardia = Right uppermost; just past the lower esophageal sphincter
Fundus = Left uppermost
Body = middle, curved portion of stomach
Pylorus = lower portion; attaches to the duodenum
Lining of stomach contains folds (rugae), similar to bladder lining
Gastric glands; located in gastric pits: ____, mucus (protective),other enzymes
Only a few substances are absorbed thru the stomach wall:
some water
electrolytes
certain drugs (aspirin)
alcohol
Pancreas
posterior to lower stomach
Pancreas is connected to ______by 2 ducts (pancreatic & accessory)
Tiny patches of cells (1%) = Secrete hormones, 99% of pancreas cells = Secrete pancreatic juice: Pancreatic amylase → breaks down carbs
Trypsin, chymotrypsin, carboxypeptidase → digest proteins
Pancreatic lipase → digests fats
Ribonuclease & deoxyribonuclease → digest nucleic acids
Liver = 2nd largest organ of the body
Large right lobe + small left lobe (positioned behind lower sternum), Produce bile → through a duct system to gallbladder for storage, Gallbladder then secretes bile when stimulated by nervous / hormones
Functions of the Liver
Carb metabolism
Lipid metabolism
Protein metabolism
Also convert one amino acid to another, as needed by the body
Liver removes & ______certain drugs & hormones from the blood
Liver stores vitamins (A, B12, D, E, K) and minerals (ferritin, Cu, etc.)
Gallbladder stores & concentrates the bile
Small Intestines, Duodenum = top end; connected to pyloric sphincter, Jejunum, Ileum = lower end; connected to large intestine at ileocecal sphincter
Small intestine is highly adapted for digestion & absorption, Large surface area for absorption
Absorption = passage of end products of digestion from GI tract into blood or lymph (90% of absorption occurs in the small intestine)
Large Intestine = Colon, Cecum = a blind pouch about 2.5” long; hangs below the ileocecal sphincter, Vermiform appendix = coiled tube attached to the cecum; 3” long, Colon (4 parts), Rectum = anterior to the sacrum & coccyx; about 8” long, Anus = outer opening of the large intestine
Internal anal sphincter = smooth muscle (involuntary)
External anal sphincter = skeletal muscle (voluntary)
More ______gets absorbed in the Colon (liquid chyme → solid/semisolid feces)
Disorders and procedures of the digestive system
Parotitis – mumps, swollen parotid salivary glands, bacterial
Heartburn – chyme pushed up esophagus due to incomplete closure of the esophageal sphincter
Vomiting – noxious chemicals, disease, motion
Gall stones – cholesterol crystals formed in gall bladder
Colon cancer – rectal bleeding, anemia
Appendicitis – inflammation, peritonitis, shock, caused by bacterial infection or fecolith
Diarrhea – ______bowel up
Constipation – slow bowel down
Stomach ulcers – lack of mucous bacteria or Nsaids creates a hole
Celiac disease – autoimmune, chronic diarrhea, fatigue, failure to thrive in children
Cystic fibrosis – recessive ______disease, chloride channel not transported across membrane, malabsorption in gut cannot exchange water, pancreas does not make enzymes well
Appendectomy – cut off appendix
Cholecystectomy – cut off gall bladder
Endoscopy – sending fiber optic camera into esophagus to evaluate and band bleeding vessels
Colonoscopy – sending fiber optic camera into colon to evaluate and take biopsy
Short gut syndrome – genetic abnormality short small intestinal tract
Comb procedure – zipper cut the intestines to increase length, fix short gut
Whipple – surgical removal of pancreatic cancer, attach remaining pancreas to duodenum, attach stomach to jejunum, duodenum become duct for pancreatic and liver secretions
Crazy surgical options: 100lbs overweight, bmi of 40
Lap band – plastic band around stomach that can be tightened, removable surgically
Gastric bypass – any rearranging or skipping of the stomach or small intestines
Roux-en-y – cut off most of stomach, attaches small egg sized portion to the jejunum, caused malabsorption
Diet types gluten free, vegetarian, vegan, diabetes, Atkins, south beach, lactose intolerant
Healthy diet =
A healthy diet is one that helps maintain or improve general health. It is important for lowering many chronic health risks, such as obesity, heart disease, diabetes, hypertension and cancer. A healthy diet involves consuming appropriate amounts of all essential nutrients and an adequate amount of water. Nutrients can be obtained from many different foods, so there are numerous diets that may be considered healthy. A healthy diet needs to have a balance of macronutrients (fats, proteins, and carbohydrates), calories to support energy needs, and micronutrients to meet the needs for human nutrition without inducing toxicity or excessive weight gain from consuming excessive amounts.
Gluten free =
A gluten- -free diet is a diet that ______foods containing gluten. Gluten is a protein found in wheat (including kamut and spelt), barley, rye, malts and triticale. It is used as a food additive in the form of a flavoring, stabilizing or thickening agent, often as "dextrin". A gluten-free diet is the only medically accepted treatment for ______disease, the related condition dermatitis herpetiformis, and wheat allergy.
Additionally, a gluten-free diet may exclude oats. Medical practitioners are divided on whether oats are an allergen to celiac disease(chronic diarrhea and failure to thrive) sufferers or if they are cross-contaminated in milling facilities by other allergens.
The term gluten-free is generally used to indicate a supposed harmless level of gluten rather than a complete absence. The exact level at which gluten is harmless is uncertain and controversial. A recent systematic review tentatively concluded that consumption of less than 10mg of gluten per day is unlikely to cause histological abnormalities, although it noted that few reliable studies had been done. Regulation of the label gluten-free varies widely by country. In the United States, the FDA issued regulations in 2007 limiting the use of "gluten-free" in food products to those with less than 20 ppm of gluten.
Vegetarian and Vegan=
Vegetarianism encompasses the practice of following ______-based diets (fruits, vegetables, etc.), with or without the inclusion of dairy products or eggs, and with the exclusion of meat (red meat, poultry, and seafood). Abstention from by-products of animal slaughter, such as animal-derived rennet and gelatin, may also be practiced.
Vegetarianism can be adopted for different reasons: In addition to ethical reasons, motivations for vegetarianism include health, religious, political, environmental, cultural, aesthetic or economic. There are varieties of the diet as well: an ovo-vegetarian diet includes eggs but not dairy products, a lacto-vegetarian diet includes dairy products but not eggs, and an ovo-lacto vegetarian diet includes both eggs and dairy products. A vegan diet excludes all animal products, including eggs, dairy, and honey.
Diabetic diet =
The basics to diabetic diet meal planning are simple once we understand the way our body breaks down food. Everything we eat is broken down into ______eventually. Sugary foods such as sweets or fruit hit the bloodstream almost immediately, followed by the slower starches (carbohydrates, or carbs), which take an hour or two to break down depending on their complexity. Proteins are next, taking about four hours, then between six and eight hours the fats finally break down. If strict attention is paid to diet and exercise, many diabetics can control their blood sugar with minimal dependence on medication.
Atkin’s diet =
The Atkins diet involves limited consumption of carbohydrates to switch the body's metabolism from metabolizing glucose as energy over to converting stored body fat to energy. This process, called ketosis, begins when insulin levels are low; in normal humans, insulin is lowest when blood glucose levels are low (mostly before eating). Ketosis lipolysis occurs when some of the lipid stored in fat cells are transferred to the blood and are thereby used for energy. On the other hand, caloric carbohydrates (for example, glucose or starch, the latter made of chains of glucose) impact the body by increasing blood sugar after consumption. (In the treatment of diabetes, blood sugar levels are used to determine a patient's daily insulin requirements.) Fiber, because of its low digestibility, provides little or no food energy and does not significantly impact glucose and insulin levels.
The Atkins Diet restricts "______carbs" (digestible carbohydrates that impact blood sugar). One effect is a tendency to decrease the onset of hunger, perhaps because of longer duration of digestion (fats and proteins take longer to digest than carbohydrates). Atkins states in his 2002 book New Diet Revolution that hunger is the number one reason why low-fat diets fail and that the Atkins diet is easier because you are allowed to eat as much as you want
South beach diet =
According to Agatston, hunger cycles are triggered not by carbohydrates in general, but by carbohydrate-rich foods that the body digests ______, creating a spike in blood sugar. Such foods include the heavily refined sugars and grains that make up a large part of the typical Western diet. The South Beach Diet eliminates these carbohydrate sources in favor of relatively unprocessed foods such as vegetables, beans, and whole grains. Carbohydrate sources are considered "good" only if they have a low glycemic index.
Given that South Beach Diet was designed by a cardiologist, it should be no surprise that it eliminates trans-fats and discourages saturated fats. Although foods rich in these "bad fats" do not contribute to the hunger cycle, they do contribute to LDL cholesterol and heart disease. The South Beach Diet replaces them with foods rich in unsaturated fats and omega-3 fatty acid which contribute to HDL cholesterol and provide other health benefits. Specifically, the diet excludes the fatty portions of red meat and poultry, replacing them with lean meats, nuts, and oily fish.
Agatston divides the South Beach Diet into three phases, each progressively becoming more liberal. "Phase 1" lasts for the first two weeks of the diet. It eliminates all sugars, processed carbohydrates, fruits, and some higher-glycemic vegetables as well. Its purpose is to eliminate the hunger cycle and is expected to result in significant weight loss. "Phase 2" continues as long as the dieter wishes to lose weight. It re-introduces most fruits and vegetables and some whole grains as well. "Phase 3" is the maintenance phase and lasts for life. There is no specific list of permitted and prohibited foods. Instead, the dieter is expected to understand the basic principles of the diet and live by the principles
Lactose intolerant =
Lactose intolerance, also called lactase deficiency or hypolactasia, is the inability to digest and metabolize lactose, a sugar found in ______. It is caused by a lack of lactase, the enzyme required to break down lactose in the digestive system, and results in symptoms including abdominal pain, bloating, flatulence, diarrhea, nausea and acid reflux.
Most mammals normally become lactose intolerant when they are young but some human populations have developed lactase persistence, in which lactase production continues into adulthood. It is estimated that 75% of adults worldwide show some decrease in lactase activity during adulthood. The frequency of decreased lactase activity ranges from 5% in northern Europe through 71% for Sicily to more than 90% in some African and Asian countries.
Lactose is a water-soluble molecule. Therefore fat percentage and the curdling process affect tolerance of foods. After the curdling process lactose is found in the water portion (along with whey and casein) but not in the fat portion. Dairy products that are "fat reduced" or "fat free" generally have a slightly higher lactose percentage. Low fat dairy foods, additionally, often have various dairy derivatives such as milk solids added to them to enhance sweetness, increasing the lactose content
Obesity eating disorders
National Institute of Mental Health
Eating disorders - An eating disorder is an illness that causes serious disturbances to your everyday diet, such as eating extremely small amounts of food or severely overeating. A person with an eating disorder may have started out just eating smaller or larger amounts of food, but at some point, the urge to eat less or more spiraled out of control. Severe distress or concern about body weight or shape may also characterize an eating disorder.
Eating disorders frequently appear during the teen years or young adulthood but may also develop during childhood or later in life. Common eating disorders include anorexia nervosa, bulimia nervosa, and binge-eating disorder.
Eating disorders are real, ______medical illnesses. They frequently coexist with other illnesses such as depression, substance abuse, or anxiety disorders.
Anorexia – Extreme ______(emaciation)
A relentless pursuit of thinness and unwillingness to maintain a normal or healthy weight
Intense fear of gaining weight
Distorted body image, a self-esteem that is heavily influenced by perceptions of body weight and shape, or a denial of the seriousness of low body weight
Lack of menstruation among girls and women
Extremely restricted eating.
Many people with anorexia nervosa see themselves as overweight, even when they are clearly underweight. Eating, food, and weight control become obsessions. People with anorexia nervosa typically weigh themselves repeatedly, portion food carefully, and eat very small quantities of only certain foods. Some people with anorexia nervosa may also engage in binge-eating followed by extreme dieting, excessive exercise, self-induced vomiting, and/or misuse of laxatives, diuretics, or enemas.