Chapter 4 - Human Digestion & Absorption Flashcards
Tissue
Collection of cells adapted to perform at specific function
What are the four major types of tissue?
Epithelial, connective, muscle, nervous
Epithelial Tissue
Composed of cells that cover surfaces outside and inside the body (ex: skin)
Epithelial cells absorb nutrients, secret important substances, excrete waste, and protect underlying tissues.
Connective Tissue
Supports and protects the body by holding structures (ex: cells, cell parts) together, stores fat, and produces blood cells (ex: tendons, cartilage, parts of bone, arteries, and veins)
Muscle Tissue
Can contract and relax and permits movement
Nervous Tissue
Transmits nerve impulses from one part of the body to another. Found in the brain and spinal cord.
Organ
A structure consisting of cells and tissues that perform a specific function in an organism
Organ System
Groups of organs classified as a unit because they work together to perform a function or set of functions
Digestion
The process of breaking down foods into a form the body can use.
Absorption
The uptake of nutrients from the GI tract into either the blood or the lymph
What are the nine major parts of the digestive system?
- the mouth/salivary glands
- the esophagus
- the stomach
- the liver
- the gallbladder
- the pancreas
- the small intestine
- the large intestine
- the rectum
What does the mouth/salivary glands do?
Chew food, perceive taste, moisten food with saliva, lubricate food with mucus, release starch-digesting (amylase) enzyme, initiate swallowing reflex.
What does the esophagus do?
Lubricate with mucus, move food to stomach by perialistic waves (swallowing)
What does the stomach do?
Store, mix, dissolved and continue digestion of food, dissolve food particles with secretions, kill micro organisms with acid, release protein-digesting (pepsin) enzyme, lubricate and protect stomach surface with mucus, regulate emptying of dissolved food into small intestine, produce intrinsic factor for vitamin B-12 absorption
What does the liver do?
Produce bile to aid fat digestion and absorption
What does the gallbladder do?
Store, concentrate, and later release bile into the small intestine
What does the pancreas do?
Secrete sodium bicarbonate and enzymes for digesting carbohydrate, fat, and protein
What does the small intestine do?
Mix and propel contents, lubricate with mucus, digest and absorb most substances using enzymes made by the pancreas and small intestine
What does the large intestine do?
Mix and propel contents, absorb sodium, potassium, and waters house bacteria, lubricate with mucus, synthesize some vitamins and short-chain fatty acids, form feces
What does the rectum do?
Hold feces and expel via the anus, the opening to the outside of the body
Alimentary Canal
Tubular portion of the digesting tract that extends from the mouth to the anus. Also known as the GI tract.
What does alimentary mean?
“Relating to nourishment or nutrition”
Nutrients must pass through the walls of what to be absorbed into the body?
the alimentary canal
What are the four layers of alimentary canal wall?
(in order) mucosa, submucosa, muscle, serosa
Mucosa
Innermost layer of the alimentary canal wall.
Lined with epithelial cells and glands.
Not smooth, has lumen (finger-like projections) which increase the surface area of the mucosa.
Submucosa
2nd layer of the alimentary canal wall.
Loose connective tissue, glands, blood vessels, and nerves.
Vessels carry substances to and from the GI tract.
Muscle
3rd layer of the alimentary canal wall.
Double layered with inner circular smooth muscle and outer longitudinal muscle fibers.
Move food forward through the GI tract.
(Stomach has 3rd layer of muscle fiber).
Serosa
Outermost layer of the alimentary canal wall.
Protects the GI tract, secretes fluid that cushions the GI tract and reduces friction during movement.
Sphincter
Muscular valve that controls the flow of foodstuffs in the alimentary canal.
What are the 5 types of sphincters?
Lower esophageal (cardiac) sphincter, pyloric sphincter, sphincter of Oddi (hepatopancreatic), ileocecal valve, anal sphincter
Lower Esophageal (Cardiac) Sphincter
Prevents the back flow (reflux) of stomach contents into the esophagus
Pyloric Sphincter
Controls the flow of stomach contents into the small intestine
Sphincter of Oddi (Hepatopancreatic)
Controls the flow of bile from the common bile duct into the small intestine
Ileocecal Valve
Prevents the contents of the large intestines from rendering the small intestine
Anal Sphincter
Prevents defecation until the person desires to do so
Peristalsis
Coordinated wave of contraction and relaxation that moves the bonus ahead of the wave through the GI tract.
Segmentation
Back and forth action in the small intestine that breaks apart the bolts and mixes them with digestive juices
Where do you find saliva and what is its digestive purpose?
Found in the mouth.
Contributes to starch digestion, lubrication, and swallowing.
Where do you find mucus and what is its digestive purpose?
Found in the mouth, stomach, and intestines.
Protects the GI tract cells, lubricates digesting food.
Where do you find digestive enzymes (amylases, lipases, proteases) and what are their digestive purposes?
Found in the mouth, stomach, small intestine, and pancreas.
They break down carbs, fats, and protein into forms small enough for absorption
Hydrolysis Reaction
Chemical reaction that breaks down a compound by adding water. One product receives a hydrogen ion (H+) and the other recipes a hydroxyl ion (OH-).
Hydrolytic enzymes break down compounds using water in this manner.
Where do you find hydrochloric acid (HCl) and what is its digestive purpose?
Found in the stomach, from the parietal cell.
Promotes digestion of protein, destroys microorganisms, increases solubility of minerals.
Where do you find bile and what is its digestive purpose?
Made in the liver, stored in the gallbladder.
Aids in fat digestion (emulsifies fat)
Where do you find bicarbonate and what is its digestive purpose?
Found in the pancreas and small intestine.
Neutralizes stomach acid when it reaches the small intestine.
Where do you find the digestive hormones and what are their purposes?
Found in the stomach, small intestine, and pancreas.
They regulate digestion and absorption.
What are the four major digestive hormones?
Gastrin, secretin, cholecystokinin (CCK), and gastric inhibitory peptide
Bolus
Mass of food that is swallowed
Lysozyme
Enzyme that is produced by a variety of cells and can destroy bacteria by rupturing cell membranes.
Found in saliva.
Amylase
Starch-digesting enzyme from the salivary gland or pancreas.
Lingual Lipase
Salivary gland’s fat-digesting enzyme produced mainly in infancy
What are the 5 basic tastes?
Salty, sour, sweet, bitter, and umami
Olfactory
Related to the sense of smell.
Epiglottis
Flow that folds down over the trachea during swallowing.
Trachea
Airway leading from the larynx to the lungs
Larynx
Structure between the pharynx and trachea containing the vocal cords
Parietal Cell
Gastric gland cell that secretes hydrochloric acid and intrinsic factor
Pepsinogen
Inactive precursor to the protein-digesting enzyme pepsin.
Produced in the stomach.
Chief Cells
Gastric gland cells that secrete pepsinogen.
Also produces gastric lipase.
Gastrin
Hormone that stimulates hydrochloric acid and pepsinogen secretion by the stomach
Prostaglandins
Potent compounds that are synthesized from polyunsaturated fatty acids and produce diverse effects in the body
Nonsteroidal Anti-Inflammatory Drugs (NSAIDS)
Class of medications that reduce inflammation, fever, and pain but aren’t steroids.
ex: aspirin, ibuprofen (Advil), naproxen (Aleve)
Heavy use of what damages the stomach wall by inhibiting prostaglandin production?
NSAIDS
Chyme
Liquid mixture of stomach secretions and partially digested foods
Duodenum
The first part of the small intestine.
10 inches long.
Gastric Inhibitory Peptide
Hormone that slows gastric motility and stimulates insulin release from the pancreas.
Ulcer
Small erosion of the top layer of cells.
Jejunum
2nd, middle, part of the small intestine.
4 feet long.
Ileum
Third, and last, part of the small intestine
5 feet long
What are the names of the finger-like projections that line the small intestine?
villi and microvilli
__________ ______ in the small intestine make chyme flow slowly
Circular folds
Enterocytes
Specialized absorptive cells in the villi of the small intestine
Glycocalyx
Projections of proteins on microvilli.
Contain enzymes to digest protein and carbohydrate.
Accessory Organs
Organs that work with a system but aren’t physically a part of it.
ex: liver & gallbladder in the digestive system
Enterohepatic Circulation
Continual recycling of compounds between the small intestine and liver
ex: bile
Cholecystokinin (CCK)
Released by the small intestine in response to dietary fat in chyme.
Stimulates the release of pancreatic bicarbonate.
Secretin
Hormone released by the small intestine in response to acidic chyme and as digestion progresses.
Stimulates release of pancreatic bicarbonate.
Motilin
Hormone released by the small intestine in response to gastric dissension and dietary fat.
Regulates motility of the GI tract.
Peptide YY
Hormone released by the ileum and large intestine in response to fat in the large intestine.
Inhibits gastric and pancreatic secretions.
Somatostatin
Hormone released by the stomach, small intestine, and pancreas.
Inhibits the release of GI hormones; allows gastric emptying, GI motility, and blood flow to the intestine
Passive Diffusion
How fats, water, and some minerals are absorbed.
When the concentration of a nutrient is higher in the lumen of the small intestine than in absorptive cells, the nutrients are forced into the absorptive cells.
Facilitated Diffusion
How sugar fructose is absorbed.
The nutrient needs a carrier protein to shuttle it from the lumen to the absorptive cells.
Active Absorption/Tranpsort
How amino acids and some sugars are absorbed.
The nutrient needs a carrier protein and ATP in order to concentrate itself of both sides of the cell membrane.
Endocytosis (Phagocytosis & Pinocytosis)
How immune substances are absorbed by infants.
Active transport where absorptive cells engulf compounds (phagocytosis) or liquids (pinocytosis).
What are the primary nutrients absorbed by the stomach?
- alcohol (20%)
- water (very little)
What are the primary nutrients absorbed by the small intestine?
- calcium
- magnesium
- iron
- glucose
- amino acids
- fats
- vitamins
- water (70-90%)
- alcohol (80%)
- bile acids
What are the primary nutrients absorbed by the large intestine?
- sodium
- potassium
- some fatty acids
- vitamin K
- biotin
- gases
- water (10-30%)
Electrolytes
Compounds that separate into ions in water and, in turn, are able to conduct an electrical current.
ex: sodium, chloride, potassium
Short-Chain Fatty Acids
Fatty acid that contains fewer than 6 carbon atoms
Medium-Chain Fatty Acids
Fatty acid that contains 6 to 10 carbon atoms
What are the three nutrients that can be transported by the cardiovascular system?
- short-chain fatty acids
- medium-chain fatty acids
- water soluble nutrients (proteins, carbs, vitamin Bs and C)
Capillary
Smallest blood vessel; the major sit for the exchange of substance between blood and tissues
Lacteals
Tiny vessels in the small intestine villus that absorb dietary fat
What are the nutrients that can be transported in the lymphatic system?
- fat soluble nutrients (most fats and vitamins A, D, E, K)
- some proteins
What are the three parts of the large intestine?
Colon, rectum, anus
What are the five parts of the colon?
Cecum, ascending colon, transverse colon, descending colon, sigmoid colon
Fermentation
Breakdown of large organic compounds into smaller compounds, especially organic acids. The breakdown is often by anaerobic bacteria.
Probiotics
Live microorganisms that when ingested in adequate amounts confers a health benefit on the host
Prebiotics
Substances that stimulate bacterial growth in the large intestine
ex: inulin and resistant starch
Composition of Feces (percentages)
75% water, 25% solid
Gastroesophageal Reflux Disease (GERD)
Digestive disease in which stomach acid or bile irritates the esophagus
Anemia
Decreased oxygen-carrying capacity of the blood.
Many causes.
Hiatal Hernia
Protrusion of part of the stomach upward through the diaphragm into the chest cavity
Peptic Ulcer
Hole in the lining of the stomach or duodenum
Perforated Ulcer
Ulcer that eats through the stomach or intestinal wall
Gallstones
Composed of cholesterol or bile pigments, crystal-like particles in the gallbladder
Irritable Bowel Syndrome (IBS)
Disorder causing irregular bowel function, abdominal pain, and abdominal distension
Colitis
Inflammation of the colon that can lead to ulcers (ulcerative colitis)
Crohn’s Disease
Inflammatory disease of the GI tract that often reduces the absorptive capacity of the small intestine
Hemorrhoids
Swollen veins of the rectum and anus
Adenosine Triphosphate (ATP)
Chemical that supplies energy for many cellular processes and reactions
