Chapter 29 The Digestive System

What are some examples of Proteases and where are they located?

- Pepsin in stomach - Trypsin in pancreas

What are the 3 typical carbohydrates in human diet?

-Cellulose -Glycogen -Starch

What enyzmes hydrolyze which disaccharides to monosacharides?

-Maltase hydrolyzes maltose -Lactase hydrolyzes lactose -Sucrase hydrolyzes sucrose

Pharynx

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What are the steps in digesting carbohydrates?

1) Hydrolyze (using glucosidase) glycogen and starch into disaccharides 2) Hydrolyze (using sucrase, maltase, lactase) disaccharides (sucrose, maltose, lactose) into monosaccharides.

Salivary Glands

3 pairs of glands that secrete saliva into the mouth. Saliva moistens, lubricates, dissolves Saliva starts the digestion of starch (salivary amylase).

Bolus

A ball of food.

Pancreas

Accessory digestive organ which produces digestive enzymes that are secreted into the small intestine (duodenum). Also an endocrine organ that produces and secretes insulin and glucagon into the blood stream. These two hormones regulate blood sugar levels.

Bile

Breaks fat into tiny droplets

Sphincter

Circular muscles that contract and relax to control the passage of food through the GI tract.

Pancreatic Juice

Digests carbohydrates proteins, and fats

Intestinal Juice

Digests just carbohydrates and proteins

Saliva

Digests only carbohydrates

Lipase

Enzymes that digest lipids (fats). Found primarily in the small intestine, produced by the pancreas. Chemical Reaction: Triglyceride (Fat) --> Fatty Acids & Glycerol

Villi

Finger like projections in the lining epithelium of the small intestine. Increases surface area for chemical digestion and absorption.

Micro-villi

Finger like projections located on the surface of the villi of the small intestine. Also Increases the surface area for chemical digestion and absorption.

Duodenum

First section of the small intestine where chyme mixes with bile, bicarbonate, and digestive enzymes.

Duodenum

Fluids from the pancreas and liver flow through a tube into this

Chyme

Food mixed with gastric juice (stomach secretions).

What are the major carbohydrates that are digested?

Glycogen and Starch

Where does sucrose get first digested?

It's first digested in the small intestines and not in the mouth.

Liver

Located on the upper right hand side of the abdomen. Detoxifies naturally occurring poisons in foods. Stores glucose as glycogen. Produces bile.

Epiglottis

Muscular flap that prevents food from entering the larynx, trachea, lungs.

Carbohydrates, proteins, and fats

Nutrients that need to be digested

What enzymes hydrolyze proteins into amino acids, dipeptides, tripeptides?

Peptidases are found in the surface of the small intestines.

Bile

Produced by the liver, stored and secreted from the gall bladder, emulsifies large fat (lipid) globs into small droplets, increasing surface area for more efficient digestion of fats.

What enzyme partially breaks down proteins?

Proteases

Proteins in stomach

Proteins are denatured by acid in stomach. Pepsin hydrolyzes the huge polypeptide chains in the stomach. Short amino acid chains move with the chyme into the duodenum.

Location of chemical digestion of all Macromolecules : Carbohydrates, Proteins, Lipids, and Nucleic Acids.

Small Intestine.

Large Intestine (Colon)

Small intestine empties into this part of the digestive tract. Removes water and allows for bacterial production of vitamins that we absorb.

Enzymes

Special chemicals that help break down food.

Location of chemical digestion of proteins only

Stomach.

Villi

The finger-like projections of the small intestine that help absorb food.

Duodenum

The first 25 cm of the small intestine.

Absorb water

The function of the large intestine is to_____.

Absorb

The increase of surface area allows the small intestine to ___ more food.

Mastication

The mechanical digestion or chewing of food with our teeth.

Churn

The mechanical digestion or mixing of stomach contents (chyme) by contraction and relaxation of the 3 layers of stomach muscles.

Chyme

The thick, soupy liquid that leaves the stomach a spoonful at a time.

Anus

This sphincter releases the feces from the body.

Small Intestine

_____ is the main organ of the digestive system...digests and absorbs food.

What type of enzyme/s are used to hydrolyze carbohydrates to disaccharides?

amylase, found in the saliva and pancreas

Pyloric Sphincter

Sphincter located at the bottom of the stomach. Controls passage of chyme into small intestine, allowing small amounts over a long period of time so as maximize small intestine digestion and absorption and neutralization of stomach acid.

What first gets digested in the mouth?

The carbohydrates glycogen and starch get digested in the mouth first.

Peristalsis

The contraction and relaxation of digestive tract muscle to propel or move food.

Gall Bladder

Located underneath the liver. Stores and releases bile.

Small Intestine

Location of most of the enzyme digestion and absorption of nutrients. Divided into 3 sections: the duodenum (most digestion), jejunum (most absorption), and ileum.

Esophagus

Tube like structure that passes food from the mouth-pharynx to the stomach.

Gastric Juice

Digests only proteins

Single sugars (or glucose)

End product of carbohydrate digestion

Fatty Acids and Glycerol

End product of fat digestion

Amino acids

End product of protein digestion

Mouth

Entrance into the digestive tract.

Pepsin

Enzyme that digests proteins. Secreted into the stomach by gastric pit cells. Activated by HCl.

Amylase

Enzyme that digests starch. Secreted in the mouth by the salivary glands and secreted into the small intestine by the pancreas.

Nuclease

Enzymes that digest nucleic acids (DNA and RNA). Found in the small intestine and produced by the pancreas. Chemical Reaction: DNA or RNA polymer --> Nucleotides

Protease

Enzymes that digest proteins. Found in the stomach and small intestine. Chemical Reaction: Protein + H2O --> Amino Acids

Location of chemical digestion of carbohydrates only

Mouth

Stomach

Receives food from the esophagus Mixes (churns) food with Pepsin and HCl to produce a mixture called Chyme. Slowly releases chyme into the small intestine (duodenum).

Bicarbonate

Secreted into the first part of the small intestine (duodenum) by the pancreas. Neutralizes the HCl in the chyme from the stomach.

HCl

Secreted into the stomach by the gastric pits. Dissolves minerals and kills bacteria, viruses, and parasites. Activates Pepsin.

Mucus

Secretion that lubricates food and protects lining of digestive tract. Example mucus protects stomach lining from HCl.

Colon

The other word for large intestine is ______.

Defecation

The passage of undigested food out of the digestive tract.

Elimination

The passage of undigested food out of the digestive tract. Synonym: Defecation

Increase Surface Area

The purpose of the length, bumps & folds, and villi in the small intestine

Absorption

The uptake or transport of nutrients from the lumen of the GI tract into the body. The majority of absorption occurs in the jejunum. After passing across the small intestine cells amino acids and glucose enter blood stream capillaries of the villi. The lipids, fatty acids enter the villi lacteals (lymphatic system).

Chemical Digestion

The use of enzymes to hydrolyze polymers like starch, protein, and nucleic acids into their corresponding monomers: glucose, amino acids, and nucleotides. Fats are also hydrolyzed into small units.

Mechanical Digestion

The use of physical force to break down food into smaller pieces. This increases surface area of the food exposed to enzymes and increases their efficiency of converting polymers to monomers (Hydrolysis).

Rectum

This stores the feces before it is eliminated from the body

Ingestion

To eat.