Nutrition- Ch. 5

Functions of The Liver- (Major Functions)

- Bile production -synthesis of proteins and blood clotting factors -Metabolism of hormones and medications -Regulations of blood glucose levels - Urea production to remove the waste products of normal metabolism

.Lactose Intolerance-

A deficiency of any one of the disaccharides (i.e., lactase, sucrose, or maltase) in the small intestine may produce wide variety of GI problems and abdominal pain because the specific sugar involved cannot be digested. Lactose intolerance is the most common and cannot presents varying degrees of intolerance With this condition, there is insufficient lactase to break down the milk sugar lactose; thus, lactose accumulates in the intestine causing abdominal cramping and diarrhea.

Cholecystokinin (CCK)

A hormone secreted from the mucosal epithelium of the small intestine in response to the presence of fat and certain amino acids in chyme. CCK inhibits gastric motility, increases the release of pancreatic enzymes, and stimulates the secretion of pepsinogen from cells of the stomach.

Secretin-

A hormone that stimulates gastric and pancreatic secretions . Secretin secretion is secretion is increased in response to a low pH in the duodenum. Secretin stimulates the pancreatic release of bicarbonate to increase the pH to an alkaline environment It also stimulates the secretion of pepsinogen from chief cells of the stomach.

Pancreatic Lipase-

A major fat-splitting enzyme produced by the pancreas and secreted into the small intestine to digest fat

Metabolism-

All chemical changes in the cell that produce materials for energy, tissue building, and metabolic controls

Chemical Digestion: Gastrointestinal Secretions: Hydrochloric acid and buffer ions.

Are needed to produce the correct pH (i.e., the degree of acidity or alkalinity) that is necessary for enzymatic activity

Digestion in the Small Intestine: Mechanical Digestion -Longitudinal rotation

By long muscles that run the length of the intestine rolls the slowly moving food mass in a spiral motion to mix it and expose new surfaces for absorption

Digestion in the Stomach: Mechanical digestion- chyme

By the time the food mass reaches the antrum (i.e., the lower portion of the stomach), it is now a semiliquid, acid-food mix

Digestion in the Small Intestine: Chemical Digestion- Intestinal enzymes

Carbohydrate: Disaccharidases (i.e., maltase, lactase, and sucrase) convert their respective disaccharides (i.e., maltose, lactose, and sucrose) into monosaccharides (i.e., glucose, galactose, and fructose) Protein: The intestinal enzyme enterokinase activates trypsinogen, which is released from the pancreas to become the protein-splitting enzyme trypsin Fat: Intestinal lipase splits fat into glycerides and fatty acids

Digestion in the Small Intestine: Chemical Digestion- Pancreatic enzymes.

Carbohydrate: Pancreatic amylase converts starch into the disaccharides maltose and sucrose. Protein: Trypsin and chymotrypsin split large protein molecules into smaller and smaller peptide fragments and finally into single amino acids Fat: Pancreatic lipase converts fat into glycerides and fatty acids.Digestion in the Small Intestine: Chemical Digestion- Intestinal enzymes

A 23 year old who is admitted to the hospital from hypothermia and starvation would most likely be in a state of ______________ upon admission

Catabolism

Absorption in The Small Intestine- Absorption Processes

Complete the task of moving vital nutrients across the inner intestinal wall and into the body circulation -diffusion -energy-driven active transport -pinocytosis

Digestion in the Stomach: Chemical Digestion- Hydrocholric Acid

Creates the necessary degree of acidity for gastric enzymes to work, and it also activates the first protease, pepsinogen, in the stomach

Absorption in The Large Intestine- Dietary Fiber

Dietary fiber is not digested because humans lack the specific enzymes that are required to break down the beta bonds between molecules Fiber contributes important bulk to food mass and helps to form feces

A patient who has a large surgical resection of the small intestine would most likely have difficulty with

Digesting food

Preparing food for the body's use involves many steps, including

Digestion, absorption, transport, and metabolism.

Chemical Digestion: Gastrointestinal Secretions: Enzymes

Digestive enzymes are proteins produced in the body and are specifically designed to break down other nutrients

Digestion in the Small Intestine: Chemical Digestion- Bile.

Emulsifying agent and an important part of fat digestion and absorption

a 45-year-old female is considering eating 2 1/2 times the recommended protein for her body in order to build more lean muscle. What would you suggest?

Explain to her that excess protein intake is broken down and used for energy if needed or stored as fat

Lymphatic System-

Fatty materials are not water soluble. These fat molecules pass into the lymph and vessels in the villi (e.g., lacteals), flow into the larger lymph vessels in the body, and eventually enter the bloodstream through the thoracic duct.

Villi-

Finger-like extensions of the intestinal mucosa that increase the surface area for absorption

Digestion in the Small Intestine: Mechanical Digestion - Pendular movements

From small, local muscles sweep back and forth, thereby stirring the chyme at the mucosal surface

Digestion in the Small Intestine: Mechanical Digestion - Segmentation rings

From the alternating contraction and relaxation of circular muscles progressively chop the food mass into successive soft lumps and then mix them with GI secretions

Mechanical Digestion in the mouth and esophagus

In the mouth, the process of mastication begins to breakdown food into smaller particles After the food is chewed, the mixed mass of food particles is swallowed, and it passes down the esophagus, largely as a result of autonomic peristaltic waves that are controlled by nerve reflexes The gastroesophageal sphincter then constricts again to retain the food within the stomach cavity. If the sphincter is not working properly, it may allow acid-mixed food to seep back into the esophagus from the stomach

Digestion in the Stomach: Chemical Digestion- Enzymes

It is activated by hydrochloric acid to become the protein-splitting enzyme pepsin

Chemical Digestion: Gastrointestinal Secretions: Bile.

Made in the liver and stored in the gallbladder, bile emulsifies fat into smaller pieces to expose more surface area for the actions of fat-splitting enzymes.

An example of mechanical digestion is:

Mastication

Phenylketonuria-

Phenylanine hydroxylase is the enzyme that is responsible for metabolizing the essential amino acid phenylalanine. PKU is an autosomal recessive genetic disorder that results when phenylalanine hydroxylaseis not produced by the body. Not curable but treatable through diet Untreated can cause permanent mental retardation, and central nervous system damage. other possible side effects include irritability, hyperactivity, convulsive seizures, and psychiatric disorders

Digestion in the Stomach: Chemical Digestion- Mucus

Protect the stomach lining from the erosive effect of hydrochloric acidSecretions also bind and mix the food mass and help to move it along the GI tract

Chemical Digestion in the mouth and esophagus

Salivary glands secrete saliva that contains salivary amylase Small glands at the back of the tongue, secrete lingual lipase. Lipase is the general name for fat-splitting enzyme Food does not remain in the mouth long enough for much chemical action to occur. During infancy, lingual lipase is a more relevant enzyme for the digestion of milk fat.

Chemical Digestion: Gastrointestinal Secretions: Mucus

Secretions of mucus lubricate and protect the mucosal tissues that line the GI tract, and help to mix the food mass

Digestion in the Small Intestine: Mechanical Digestion - Peristaltic waves

Slowly push the food mass forward, sometimes with long, sweeping waves over the entire length of the intestine

Digestion in the Small Intestine: Chemical Digestion

Small intestines, together with the GI accessory organs (i.e., the pancreas, liver, and gallbladder), supply many secretory materials to accomplish the major chore of chemical digestion. The pancreas and intestines secrete enzymes that are specific for the digestion of each macronutrient. Also include mucus

Mechanical Digestion- Gastrointestinal Motility- (Nerves)

Specific nerves regulate muscular action along the GI tract. A complex network of nerves in the GI wall called intramural nerve plexus extends from the esophagus to the anus. These nerves do three things- (1) they control muscle tone in the wall (2) they regulate the rate and intensity of the alternating muscle contractions (3) they coordinate all of the various movements

Digestion in the Small Intestine: Mechanical Digestion -Surface villi motions

Stir and mix the chyme at the intestinal wall, thereby exposing additional nutrients for absorption.

Digestion in the Small Intestine: Chemical Digestion- Hormones

The hormone cholecystokinin, which is secreted by intestinal mucosal glands when fat is present, triggers the release of bile from the gallbladder to emulsify fat The hormone secretin, which is produced by the mucosal glands in the first part of the intestine, controls the acidity and secretion of enzymes from the pancreas

Mucosal Folds-

The large, visible folds of the mucous lining of the small intestine that increase the absorbing surface area

Absorption in The Large Intestine- Water

The main absorptive task for the large intestine is to absorb water Most water in the chyme that enters the large intestine is absorbed in the first half of the colon only small amounts (approx. 100 mL) remin to form the feces and be eliminated.

Chemical Digestion: Gastrointestinal Secretions: Water and electrolytes.

The products of digestion are carried and circulated through the GI tract and into the tissues by water and electrolytes.

Absorption in The Small Intestine- Absorbing Structures

Three important structures of the small intestinal wall surface are particularly adapted to ensure the maximal absorption of essential nutrients in the digestive system. -Mucosal Folds -Villi -Microvilli They combine to make the inner surface nearly 600 times greater than the area of the outer surface of the intestine.

Mechanical Digestion- Gastrointestinal Motility- (Muscles)

To provide two general types of movement (1) muscle tone or tonic contraction, which ensures the continuous passage of the food mass and valve control along the way; and (2) periodic muscle contraction and relaxation, which are rhythmic waves that mix the food mass and move it forward

The primary nutritional function of the large intestine is

absorption of water.

If you chew a piece of bread in the mouth for a long time, it begins to taste sweet because of the action of the enzyme:

amylase

The starch-splitting enzyme in the mouth is

amylase

An emulsifying agent that aids fat digestion and absorption is

bile

Glycolysis-

breaking down glucose into pyruvate to enter the Krebs Cycle

Glycogenolysis

breaking down glycogen into individual glucose units

Lypolysis-

breaking down lipids into fatty acids and glycerol

Protein Degradation-

breaking down proteins into single amino acids

Protein Synthesis-

building complete proteins from individual amino acids

Lipogenesis-

building up lipids from fatty acids and glycerol

Glycogenesis-

combining units of glucose to store as glycogen

Gluconeogenesis

converting noncarbohydrate substances into glucose

Microvilli-

extremely small, hair-like projections that cover all of the villi on the surface of the small intestine and that greatly increase the total absorbing surface area

Intestinal Gas-

forms in the colon, where bacteria attack fermentable residues and cause them to decompose and produce gas carbohydrates release hydrogen, carbon dioxide, and in some peoplewith certain types of bacteria in the gut, methane All three products are odorless Protein produces hydrogen sulfide and volatile compounds such as indole and skatole, which add a distinctive aroma to the expelled air.

Stomach Gas-

gas is a normal by-product of digestion it results from trapped air bubbles. it occurs when a person eats too fast, drinks through a straw, or otherwise takes in extra air while eating. burping release some gas, but the following can help to avoid uncomfortable situations -avoid carbonated beverages -do not gulp -chew with the mouth closed -do not drink from a can or through a straw -do not eat while overly nervous

Converting noncarbohydrate substances into glucose is called

gluconeogenesis.

Compared with the pH in the small intestine, the pH in the stomach is

lower

Fat molecules enter into the bloodstream through the

lymph vessels.

Phenylketonuria is caused by the inability to produce the enzyme needed to

metabolize the amino acid phenylalanine.

The mucosal lining of the intestine is protected from irritation and erosion by secretions of

mucus

A hiatal hernia occurs when

part of the stomach protrudes upward into the chest cavity

The part of the circulatory system that transports blood from the intestines to the liver is called the

portal circulation system.

Mastication is an important part of digestion because it

prepares the food for digestion by enzymes.

Peptidases are enzymes that act on

proteins

The hormone that stimulates the pancreas to release its secretions is

secretin.

Chyme is the word used for the intestinal contents when they are in the

stomach.

Pancreatic Amylase-

the major starch-splitting enzyme that is secreted by the pancreas and that acts in the small intestine

Transport-

the movement of nutrients through the circulatory system from one area of the body to another

Digestion-

the process by which food is broken down in the GI tract to release nutrients in forms that the body can absorb

Absorption-

the taking in of nutrients in forms that the body can absorb

The fingerlike projections in the small intestine that ensure maximal absorption of nutrients are called

villi.