Ch 8 - Digestive System Flashcards
What is the gastrointestinal (GI) tract?
The tube where organs of the digestive system are located
What does hydrolyze mean?
To break down macromolecules into their subunits using water
What do carbohydrates break down to?
Glucose
What does protein break down to?
Amino Acids
What does fat break down to?
Monoglycerides and free fatty acids (which are broken down from triglycerides)
Which enzymes break down carbs?
Salivary & pancreatic amylase + intestinal enzymes
Which enzymes break down proteins?
Trypsin (protease) released by the pancreas (acts in small intestine) + intestinal enzymes
Which enzymes break down fats?
Lipase
What emulsifies fats?
Bile
What organ produces bile and what organ stores it?
The liver produces bile and the gallbladder stores bile
What is the name of the first 25 cm of the small intestine where most enzymes and bile are secreted?
The duodenum
What is peristalsis?
Wavelike contractions of smooth muscles, starting in the esophagus and continuing through the colon
What is the role of the pancreas?
Produces pancreatic juice
Releases digestive enzymes in the small intestine
Produces insulin & secretes it into the blood after eating
What is the passageway where food is swallowed?
The pharynx
Which organs of the digestive system do not play a role in chemical digestion?
The esophagus and the large intestine
What is the role of the large intestine?
Absorbs water and salt to form feces
What is the lumen?
The hollow area of the digestive tract where food travels.
What are the four layers of the GI tract?
- Starts from the inside w/ the lumen
1. Mucosa
2. Submucosa
3. Muscularis
4. Serosa
What role does the mucosa play?
This layer contains cells that produce and secrete mucus to protect all the layers of the tract from the digestive enzymes inside the lumen.
What is a common disease in the mucosa layer?
Diverticulosis = when the mucosa (primarily in the large intestine) have pushed through the other three layers and create a pouch where food can collect. When these pouches become infected or inflamed, it’s called diverticulitis.
What role does the submucosa layer play?
A band of loose connective tissue that contains blood vessels, lymphatic vessels and nerves. These vessels carry the nutrients that are absorbed by the mucosa. Lymph nodules also located here.
What is a common disease in the submucosa layer?
Because it contains blood vessels, it can be a site for inflammatory responses that lead to IBD, inflammatory bowel disease.
What role does the muscularis layer play?
Two layers of smooth muscle that contract to create peristalsis
What is a common disease in the muscularis?
IBS (Irritable bowel syndrome). Where contractions of the wall cause abdominal pain, constipation or diarrhea.
What role does the serosa layer play?
It’s the membrane, which secretes a lubricating fluid. Part of the peritoneum, the internal lining of the abdominal cavity.
Why are our lips so red?
Because they’re poorly keratinized, allowing blood to show through.
What does the soft palate in our mouth connect to?
The uvula, which hangs down in the back of our mouth.
What is the tube called where air travels from your nose to the pharynx?
The nasopharynx
What are the adenoids and where are they located?
Right above the soft palate where the nasal cavity opens. They, along with the tonsils, are part of the lymphatic system. The adenoids are a single pharyngeal tonsil.
How many pairs of salivary glands are there that secrete into the mouth?
Three.
What happens when a person has the mumps?
The salivary glands above the molars swell. The mumps are a viral disease.
What is saliva?
A solution of mucus and water. It also contains salivary amylase, which breaks down starch.
What is enamel?
An extremely hard outer covering of calcium compounds
What is the inner pulp of a tooth?
It contains the nerves and the blood vessels.
What are dental caries?
Cavities, which occur when bacteria within the mouth metabolize sugar.
What is gingivitis?
Inflammation of the gums
What is periodontitis?
A loss of bone and loosening of the teeth.
What is the pharynx?
Where the mouth and nasal passages lead. A hollow space at the back of the throat where food gets swallowed and air passes through
Which tubes branch off of the pharynx?
The esophagus and the trachea (windpipe)
What happens when we swallow food (a bolus)?
The soft palate moved backwards to cover the nasopharynx/nasal passages, and the epiglottis covers the glottis so food can’t get into the trachea
What is the glottis?
The opening to the larynx (voice box) and, therefore, the air passage
What is the lower gastroesophageal sphincter?
The entrance of the esophagus to the stomach. Sphincters act as valves
What prevents stomach acid from going up into the esophagus?
The gastroesophageal sphincter contracting
What takes place during vomiting?
When strong contractions of the abdominal muscles and the diaphragm force the contents of the stomach into the esophagus and the oral cavity.
What is the role of the stomach?
Stores food
Initiates the digestion of protein
Controls movement of food into small intestine
Nutrients aren’t absorbed by the stomach
Which layers of the stomach is modified?
It has all four layers of the GI tract, but the muscularis has three layers of muscle instead of 2
What is the oblique layer?
The extra third layer of the muscularis in the stomach that allows it to stretch and mechanically break down food into smaller fragments that are mixed with gastric juice.
What is emulsion?
Breaking down fat into smaller molecules and spreading them out. Dispersing them. When fat is emulsified, it breaks up into droplets, which provide a larger surface area for digestive enzymes to act upon them.
What does the mucosa layer of the stomach contain?
Rugae, which are deep folds with gastric pits and gastric glands where cells secrete gastric juice.
What enzymes do gastric glands secrete (part of gastric juice)?
Pepsin, which is an enzyme that breaks down protein. It also secretes hydrochloric acid (HCl)
What is the role of hydrochloric acid?
Causes the stomach to be very acidic so as to kill bad bacteria and help break down connective tissue of meat for digestion AND activates pepsin. Has an acidity of about 2.
How long does it take the stomach to empty?
2-6 hrs
What is chyme?
The thick, soupy liquid of the stomach’s partially digested food that enters into the small intestine.
What is the sphincter called that connects the stomach to the small intestine where chyme passes through?
The pyloric sphincter.
How long is the small intestine and large intestine?
Small = 6m (18 ft) Large = 1.5m (4.5 ft)
What happens after fat is emulsified by the bile produced by the liver (released in the small intestine)?
The lipase enzyme, produced by the pancreas, hydrolyzes fats (chemical reaction to break things down with water)
What is the pH of the intestines?
It’s slightly basic, because pancreatic juice neutralizes chyme
What are the major digestive enzymes involved in carbohydrate digestion?
Salivary amylase - made and released in mouth
Pancreatic amylase - made by pancreas but released in small intestine
Maltase - made and released in the small intestine
Lactase - made and released in the small intestine
What are the major digestive enzymes involved in protein digestion?
Pepsin - made and released in stomach (gastric glands)
Trypsin - made in pancreas and released in small intestine
Peptidases - made and released in small intestine
What are the major digestive enzymes involved in nucleic acid digestion?
Nuclease - made by pancreas but released in small intestine
Nucleosidases - made and released in small intestine
What are the major digestive enzymes involved in fat digestion?
Lipase - made by pancreas but released in small intestine
What is nucleic acid, and why should we break it down?
Types of nucleic acid are DNA and RNA. We break nucleic acid down into nucleotides so that we can use those to build our own DNA
Which of the 4 GI tract layers are modified in the small intestine for absorption? How is it modified?
The mucosa. It has villi, or small finger-like projections. A villus has an outer layer of columnar epithelial cells, and each of these cells has microscopic extensions called microvilli.
What can be found on microvilli?
Brush border enzymes that complete the digestive process
How are nutrients absorbed in the small intestine?
They’re absorbed into the vessels of a villus, which contains blood capillaries and a small lymphatic capillary
What are lacteals?
Small lymphatic capillaries in the villi
Which macromolecules are absorbed into the blood capillary of a villus, and which are absorbed into a lacteal?
Carbohydrates (glucose) and protein (amino acids) are absorbed into the blood capillary.
Fats (monoglycerides and free fatty acids) are absorbed into lymphatic capillaries, or lacteals. Eventually these are absorbed into the bloodstream as well.
Which enzyme is missing in people with lactose intolerance? Why would diarrhea occur?
Lactase. Diarrhea occurs because undigested lactose causes fluid retention in the small intestine. This is because the glucose molecules increase the osmolarity of the lumen, thus water doesn’t get absorbed well into the small/large intestine. Bacteria breaks down the lactose anaerobically, causing gas, bloating and cramps
What is a hormone?
A protein or steroid produced by a cell that affects the function of a different cell (the target cell)
Why is the pancreas considered a gland?
Because it secretes hormones (insulin)
What is pancreatic juice?
Contains sodium bicarbonate (NaHCO3) and digestive enzymes for all types of macromolecules.
What are the three different enzymes created by the pancreas that digest carbohydrates/starch, protein and fats?
- Carbs/starch = amylase
- Protein = protease/trypsin
- Fats = lipase
What is type I diabetes?
When the pancreas doesn’t manufacture enough insulin.
What is type II diabetes?
When the body’s cells have become insulin-resistant (cells aren’t receptive to insulin)
What is the largest gland in the body?
The liver. It’s a gland because it secretes
What are functions of the liver?
- Destroys old red blood cells and converts them into bilirubin, which is a breakdown product of hemoglobin.
- Releases bilirubin in bile
- Stores iron (Fe2+), vitamin B-12 (water-soluble), and vitamins A, D, E and K (fat-soluble)
- Makes plasma proteins, such as albumins and fibrinogen, from amino acids
- Stores glucose as glycogen after a meal and vice versa to maintain the blood sugar levels between meals
- Produces urea from breaking down amino acids (nitrogenous waste)
- Helps regulate blood cholesterol levels, converting some bile to salts
What are the accessory organs of the digestive system?
The liver
The gallbladder
The pancreas
What does the liver do with glucose, and what hormone do its actions depend on?
In the presence of insulin, it stores glucose as glycogen after a meal. Between meals, it converts glycogen to glucose in the blood to maintain blood sugar levels
What things does the liver store?
Stores iron (Fe2+), vitamin B-12 (water-soluble), and vitamins A, D, E and K (fat-soluble). Stores glycogen
What role does the liver play with protein digestion?
Converts amino acids into glucose, a process called gluconeogenesis. The liver combines their amino groups with carbon dioxide to form urea, the nitrogenous waste product in humans.
What is bile?
A solution of bile salts, water, cholesterol and bicarbonate. It has a yellowish-green color because it contains bilirubin, a pigment protein formed during the breakdown of hemoglobin.
Where is bile stored?
The gallbladder
What are gallstones?
These form in the gallbladder when the liquid stored there hardens into pieces of stone-like material.
What is jaundice?
A liver disorder where bile pigments leak into the blood, causing the skin to yellow. Can result from hepatitis, or inflammation of the liver
What are the forms of hepatitis?
Hep A = acquired from sewage-contaminated drinking water and food.
Hep B = spread by sexual contact or blood transfusions/contaminated needles
What is cirrhosis?
A chronic disease of the liver. 1) Organ becomes fatty, then 2) liver tissue is replaced by scar tissue. Seen in alcoholics due to excessive toxins and malnutrition (depletion of minerals and nutrients because liver is using them to break town the toxins (aka alcohol)). Also occurs due to obesity.
What controls the secretion of digestive juices of the digestive system?
The nervous system/digestive hormones. Parasympathetic/sympathetic nervous system get activated by seeing and smelling food.
Hormones = CCK, gastrin and secretin
What is CCK?
Cholecystokinin. A hormone that induces the release of bile to emulsify fats.
What is gastrin?
A hormone that induces activity of gastric glands for protein digestion
What is secretin?
A hormone that induces secretion of pancreatic enzymes that neutralize the acidic hydrochloric acid present in chyme as it reaches the duodenum
What’s the section where the large intestine joins with the small intestine called? What else is located here?
The cecum. The appendix is also found here, as a projection of the cecum.
What role does the appendix possibly play?
Thought to aid in fighting infections. Also might contribute to the population of needed bacteria in the large intestine
What is peritontitis?
Inflammation of the peritoneum — a silk-like membrane that lines your inner abdominal wall and covers the organs within your abdomen — that is usually due to a bacterial or fungal infection. Oftentimes caused by the appendix bursting. Leads to swelling and infection of the peritoneum.
What is the peritoneum?
A thin membrane that lines the abdominal and pelvic cavities
What are the 3 parts of the colon?
- Ascending
- Transverse
- Descending
- Sigmoid = enters the rectum; last 20 cm of the large intestine
What are the functions of the large intestine?
- Does NOT produce any digestive enzymes
- Does NOT absorb any nutrients (glucose, fatty acids, etc.)
- Can absorb vitamins
- Absorbs water
- Bacteria in the large intestine break down indigestible material and produce B-complex vitamins and most of the vitamin K needed by our bodies
- Forms feces
What is feces made up of?
3/4 water, 1/4 solid waste
Solid waste = bacteria, dietary fiber and other indigestible materials
Stercobilin (breakdown product of bilirubin) + oxidized iron create the brown color of feces
What initiates nerve impulses to the spinal chord to tell our brain that it’s time to defecate?
Stretch receptors in the rectal wall as feces collects in the rectum
What are the major causes of diarrhea?
- Infection of lower intestinal tract = intestinal wall becomes irritated, and peristalsis increases when an infection occurs. Water isn’t absorbed and we try ridding body of infectious organisms via diarrhea.
- Nervous stimulation = nervous system stimulates intestinal wall, resulting in diarrhea
What is constipation and how does it happen?
When feces aren’t expelled regularly, water is absorbed from them and the material becomes drier/harder. Adequate water and fiber intake can help regularity of defecation.
What are hemorrhoids?
Enlarged and inflamed blood vessels at the anus
What is IBD, and what are the two most common types?
Inflammatory bowel disease, a collective term for several inflammatory disorders that oftentimes lead to ulcers in the submucosal layer of the GI tract.
- Ulcerative colitis - large intestine and rectum > diarrhea, rectal bleeding, abdominal cramps, and urgency in defecation
- Crohn’s disease - isolated in small intestine normally. Breakdown of the lining of the affected area resulting in ulcers. Cause bleeding b/c erodes submucosal layer. Inability to absorb nutrients at the affected sites
What is IBS?
Irritable bowel syndrome, or spastic colon. When muscularis contracts powerfully but without its normal coordination.
What are polyps?
Small growths arising from the epithelial lining. Can be benign or cancerous
What is a colonoscopy?
Doctor examines the GI tract through the anus and takes tissue samples.
Why is obesity dangerous?
Excess body fat is associated with a higher risk for premature death, type 2 diabetes, hypertension, cardiovascular disease, stroke, gallbladder disease, etc.
How is obesity defined?
A BMI (body mass index) of 30+.
Weight (lbs) divided by height (inches squared) x 703
What is a nutrient?
A required component of food that performs a physiological function in the body.
What is refined food?
When the fiber is removed from the grain, leaving mainly starch
What is the difference between insoluble fiber and soluble fiber?
Insoluble = adds bulk to fecal material and stimulates movements of the large intestine Soluble = combines w/ bile salts and cholesterol in the small intestine and prevents them from being absorbed
Why do we need a daily supply of essential amino acids?
Because EAAs can’t be stored in the body, whereas other amino acids can be stored as proteins and metabolized for cells’ needs.
What is urea?
A substance that the liver makes to safely eliminate nitrogenous wastes from the breakdown of protein. Large amounts of water are needed to properly excrete urea.
What happens if protein intake is excessive?
Dehydration can occur if protein intake is excessive. It can also increase calcium loss in urine, which can lead to kidney stones and bone loss.
What are the essential fatty acids?
Polyunsaturated oils. It’s the only type of fat that contains linoleic acid (Omega-6) and linolenic acid (Omega-3), two fatty acids that the body cannot make.
What type of fat is omega 3?
Monounsaturated fatty acids
What are the two types of unsaturated fatty acids? Are these good or bad for us?
- Monounsaturated fatty acids
- Polyunsaturated fatty acids
They’re good for us and prevent us from getting heart disease.
What does the textbook say about saturated fats?
They contribute to the formation of lesions associated with atherosclerosis inside blood vessels, called atherosclerotic plaques
What does HDL do?
Transports cholesterol to the liver to be metabolized.
What does LDL do?
Transports cholesterol to tissues to be deposited (this is the “bad” cholesterol)
What are trans-fatty acids? (aka hydrogenated oils)
When unsaturated fatty acids are hydrogenated to produce a solid fat.
What are the two types of minerals?
Trace minerals < 100mg < major minerals
What are the major minerals? (see functions on pg. 188)
Calcium Phosphorus Potassium Sulfur Sodium Chloride Magnesium
What are the trace minerals? (see functions on pg. 188)
Zinc Iron Copper Iodine Selenium Manganese
What is calcium needed for?
- Strong bones/teeth
- Nerve conduction
- Muscle contraction
- Blood clotting
What is osteoporosis?
Degenerative bone disease where osteoclasts are more active than osteoblasts.
What is sodium needed for?
- Regulate the body’s water balance
- Nerve conduction
- pH
- Movement of materials across the plasma membrane (look up sodium/potassium pump, which helps particles move across membranes)
What are vitamins?
Organic compounds that the body uses for metabolic purposes but is unable to produce in adequate quantity. Many vitamins are portions of coenzymes, enzyme helpers. These coenzymes can be used over and over again. Vitamin A isn’t a coenzyme, but rather a precursor for the visual pigment that prevents night blindness
What are the fat-soluble vitamins? (see functions on pg. 190)
Vitamin A
Vitamin D
Vitamin K
Vitamin E
What are the water-soluble vitamins? (see functions on pg. 190)
Vitamin C Thiamine (vitamin B1) Riboflavin (vitamin B2) Niacin (nicotonic acid) Folacin (folic acid) Vitamin B6 Pantothenic acid Vitamin B12 Biotin
How do free radicals stabilize themselves?
They give up one of their electrons to DNA, proteins (including enzymes), or to lipids found in cell membranes. These donations damage these cellular molecules and can lead to disruptions of any cellular functions. Antioxidants are good to donate these electrons to because they…get eliminated before they cause too many issues? Or because they’re less important than DNA, proteins and lipids
What are examples of antioxidants?
Vitamin C, E and A.
What does vitamin D turn into?
Calcitriol, which promotes absorption of calcium in the intestines
What is anorexia nervosa?
When you don’t eat enough to maintain a healthy body weight.
What is bulimia nervosa?
When you purge so as to not gain weight
What is binge-eating disorder?
Episodes of overeating without purging.
What is muscle dysmorphia?
When someone thinks his or her body is underdeveloped. Bodybuilding activities and preoccupation with diet and body form.
