Chapter 3 Flashcards
Absorption
Process of taking substances into the interior of the body.
Gastrointestinal Tract (7)
Hollow tube aprox. 10m in length that runs from the mouth to the anus. Organs include: mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus.
Transit Time
Amount of time it takes for food to pass the length of the GI tract. In a healthy adult transit time is about 24-72 hours.
Feces
Body waste, including unabsorbed food residue, bacteria and dead cells.
Produce saliva, which contains a starch-digesting enzyme
Salivary glands
Swallows chewed food mixed with saliva
Pharynx
Moves food (bolus) to the stomach by peristalsis.
Esophagus
Churns and mixes food (chyme); secretes acid and a protein-digesting enzyme pepsin and enzyme rennin.
Stomach
Makes bile, which aids in digestion and absorption of fat.
Liver
Releases bicarbonate to neutralize intestinal contents; produces enzymes that digest carbohydrate, protein, and fat.
Pancreas
Stores bile and releases it into the small intestine when needed.
Gallbladder
Completes digestion; absorbs nutrients into blood or lymph. Most nutrient absorption occurs here.
Small intestine.
Absorbs water and some vitamins and minerals; home to intestinal bacteria; passes waste material.
Large intestine
Opens to allow waste to leave the body
Anus
Structures of the GI tract wall from the inside out.
Lumen Mucosa Connective tissue Layers of smooth muscle External layer of connective tissue
Lumen
The tube inside the gastrointestinal tract. Food within the lumen has not yet been absorbed and is therefore technically still outside the body. Consists of 4 layers of tissue (mucosa, connective tissue, layers of smooth muscle, external layer of connective tissue).
Mucus
Viscous material produced by goblet cells; mucus moistens, lubricates and protects the GI tract. Secreted inside the lumen.
Enzymes
A digestive secretion/protein molecules that speeds up chemical reactions without being changed or destroyed in the process.
Enzymes that break down starches (2)
Salivary amylase, pancreatic amylase
Enzymes that break down protiens (6)
pepsin, trypsin, chymotrypsin, carboxypeptidase, aminopeptidase, dipeptidase
Enzymes that break down sugars (4)
Sucrase, lactase, maltase, dextrinase (all found in the small intestine)
Enzymes that break down fats (3)
Pancreatic lipase, lipase
Only 2 enzymes secreted in the stomach
Pepsin, rennin
What can stimulate activity in the digestive tract?
Sight and smell of food, presence of food in the gut, hormones.
The hormone that stimulates secretion of hydrochloric acid (HCL) and pepsinogen by gastric glands in the stomach and increases gastric motility and emptying.
Gastrin; comes from stomach mucosa
A hormone that inhibits the following: stomach secretion, motility, and emptying; pancreatic secretion; absorption in the small intestine; gallbladder contraction; and bile release.
Somatostasin; comes from stomach and duodenal mucosa
Secretin
A hormone secreted by the mucosal lining of the duodenum. Signals the pancreas to secrete pancreatic juice rich in bicarbonate ion and stimulates the liver to secrete bile into the gallbladder.
Mucosa
A layer of mucosal cells lining the lumen that serve as a protective layer and is responsible for the absorption of the end products of digestion. They reproduce rapidly and are one of the first parts of the body to be affected by nutrient deficiencies.
Cholecystokinin (CCK)
A hormone secreted by the mucosal lining of the duodenum. Signals the pancreas to secrete digestive enzymes and caused the gallbladder to contract and release bile into the duodenum.
A hormone that inhibits gastric secretion and motility
Gastric inhibitory peptide; duodenal mucosa
Digestion
Process of breaking food into components small enough to be absorbed by the body.
What characteristics of the wall of the GI tract enables it to propel food?
The rhythmic contraction of smooth muscles.
3 types of cells of the immune system that are present in the GI tract
Phagocytes
Lymphocytes
Antibodies
A cell of the immune system that is found in the GI tract. It is the first responder to that detects an antigen. It target the antigen, engulfs it, and destroys it by breaking it up.
Phagocytes
A cell of the immune system found in the GI tract that detects the broken up pieces of the antigen and produce antibodies.
Lymphocytes
Antibodies
Bind to an invading antigen and help destroy them. Each antibody is designed for one specific antigen and will be produced again to fight it when the body detects the the same antigen in the body.
A mixture of partially digested food and stomach secretions. Normally leaves the stomach in 2-6 hours.
Chyme
Parietal Cells
Large cells in the stomach lining that produce and secrete intrinsic factor and hydrochloric acid.
The HCL kills most bacteria present in food.
The Intrinsic factor is needed for Vit. B12 absorption.
Substances found in Gastric Juice
HCL (parietal cells), pepsinogen (the inactive form of pepsin), rennin (in children only)
Peptic Ulcer
An open sore in the lining of the stomach, esophagus or small intestine. Pepsin and acid can damage the underlying tissues.
Gastrin
A hormone secreted by the stomach mucosa that stimulates the secretion of gastric juice
Main site of digestion and absorption of nutrients. Divided into 3 segments (duodenum, jejenum, ileum)
Small intestine
Villi and mocrovilli
Villi -Fingerlike protrusions of the lining of the small intestine that participate in the digestion and absorption of nutrients.
Microvilli - minute brush-like projections on the mucosal cell membrane that increase the absorptive surface area in the small intestine.
Duodenum
Part of the small intestine, secretes secretin which signals the pancreas to secrete pancreatic juice and liver to secrete bile into gallbladder. CCK (Cholecystokinin) then signals the pancreas to secrete digestive enzymes and the gallbladder to contract and release bile into the duodenum (small intestine).
Pancreas
Secretes pancreatic juice.
- bicarbonate ions: neutralize acid in chyme
- pancreatic amylase: breaks starch down into sugars
- Trypsin/chymotrypsin: break protein down
- Lipase: break fat down
Gallbladder
Secretes bile produced in liver and stored in gallbladder. Bile needed for fat digestion and absorption.
Large intestine
Does not participate in digestion. Only absorbs some water, vitamins and minerals. Contains the colon and rectum.
Microflora
Bacteria found in the large intestine that synthesis small amounts of fatty acids, some B vitamins, and K vitamins, some of which can be absorbed. By product of bacterial metabolism is gas.
Vitamin E and fatty acids
Are absorbed by simple diffusion. (high concentration to low concentration)
Water and nutrient absorption
Water moves across a membrane to balance the concentration on the other side. For example, high sugar concentration in the lumen, water will move from the mucosal cells into the lumen. As sugar is absorbed and sugar in lumen decreases, water moves back into the mucosal cells by osmosis.
Digestion
The process of breaking food into components small enough to be absorbed into the body
2 main functions of the digestive system
digestion, absorbtion
Barrier function
Gastrointestinal cells prevent the absorption of harmful substances in the GI tract. Immune cells that lie below the mucosal cells can detect antigens by producing and secreting phagocytes, and antibodies.
Lysozyme
Enzyme found in the mouth that inhibits the growth of bacteria.
Stops the function of salivary amylase when it reaches the stomach. Salivary amylase continues in the small intestine.
Pepsin
Parietal cells
Cells found in the gastric pits in the stomach that produce intrinsic factor and HCL.
Simple diffusion
A mechanism of absorption of nutrients in the small intestine. A substance moves across a membrane from an area of higher concentration to an area of lower concentration. This method does not require an input of energy. ex. vitamin E, fatty acids
Facilitated diffusion
A mechanism of absorption that requires carriet molecules to move molecules down a concentration gradient from an are of high concentration to an area of lower concentration. ex. fructose
Active transport
A process of absorption that requires a carrier molecule and the input of energy. This allows the substances to be transported against their concentration gradient. ex.glucose
Intestinal Microflora
Microorganisms that inhabit the small intestine.
GERD
gastrointestinal reflux disease
Atrophic gastritis
An inflammation of the stomach lining that causes a reduction in stomach acid and allows bacterial growth. Common in elderly.
Hepatic Portal
The system of blood vessels that collects nutrient-laden blood from the digestive organs and delivers it to the liver.
Includes amino acids, simple sugars, water soluble products of fat digestion are taken to capillaries.
Lymphatic system
The system of blood vessels, organs, and tissues that drains excess fluid from the spaces between cells, transports fat-soluble substances from the digestive tract and contributes to immune function. Includes products from fat digestion that are not water soluble and taken to lacteals - small vessels of the lymphatic system before entering the blood.
Veins
transport blood and dissolved substances toward the the heart
Arteries
Transport blood and dissolved substances away from the heart.
Liver and glucose function
Removes absorbed glucose from the blood and stores it by sending absorbed glucose on to the tissues of the body, or by releasing liver glucose into the blood.
Liver and amino acid function
Modifies the products of protein breakdown o form molecules that can be safely transported to the kidneys for excretion. Also contains enzymes that protects the body from toxins that are absorbed by the GI tract.
Mitochondron
Organelle in the cell where metabolic reactions that provide energy occur.
Metabolic Pathway
A series of chemical reactions inside of a living organism that result in the transformation of one molecule into another.
Coenzyme
A small unit (not a protein but sometimes a vitamin) that is necessary for enzymatic reactions. ex. B vitamins
ATP
Adenosine triphosphate - the high energy molecule used by the body to perform energy-requiring activities. Made by the breaking of chemical bonds that hold molecules together. Bonds of ATP are very high in energy. Consists of an adenosine molecule attached to three phosphate groups.
Anabolic pathways
metabolic pathways that use energy from ATP to build new compounds.
Catabolic pathways
The process which substances are broken down into simpler molecules, releasing energy. Some of the energy is lost as heat and some is converted into ATP
Cellular Respiration
The reactions that break down carbohydrates, fats, and proteins in the presence of oxygen to produce carbon dioxide, water and energy in the form of ATP
Acetyl-CoA
Metabolic intermediate formed during the breakdown of glucose, fatty acids, and amino acids. A 2-carbon compound attached to a molecule of a CoA (C-C-CoA)
Citric acid cycle
The stage of the cellular respiration in which two carbons from acetyl-CoA are oxidized, producing two molecules of carbon dioxide
Glycogen
A storage form of carbohydrate synthesized by glucose
If body has enough glycogen, glucose can be used to form fatty acids. Which can then be used to form triglycerides that are stored as body fat.
Urea
A nitrogen containing waste product formed from the breakdown of amino acids that is excreted in the urine.
Capillaries
Small thin walled blood vessels where the exchange of gases and nutrients between blood and cells occur
Nephron
the functional unit of the kidney which performs the job of filtering the blood and maintaining fluid balance.
Glomerulus
Ball of capillaries in the nephron that filters blood during urine formation.
Lacteals
A tubular component of the lymphatic system that carries fluid away from the body tissues. Lymph vessels in the intestine are known as lacteals and can transport large particles such as the products of fat digestion.
The sum of all the chemical reactions that take place in a living organism.
Metabolism
