Chapter 8 - Digestive System and Nutrition: Exam 2

What are the main steps in the digestive process?

Ingestion, secretion, digestion, movement, absorption, and elimination

Ingestion

Intake of food via the mouth

Digestion

Mechanically or chemically breaking down foods into their subunits

Movement

Food must be moved along the GI tract in order to fulfill all functions

Absorption

Movement of nutrients across the GI tract wall to be delivered to cells via the blood

Elimination

Removal of indigestible molecules

What are the 4 major layers that make up the wall of the GI tract?

Mucosa, submucosa, muscularis, and serosa

Lumen

Central space right below the mucosa containing food being digested

Mucosa

Innermost layer that produces mucus to protect the lining and also produces digestive enzymes

Submucosa

2nd layer of loose connective tissue that contains blood vessels, lymphatic vessels, and nerves

Muscularis

3rd layer made of 2 layers of smooth muscle that move food along the GI tract

Serosa

Outer lining that is part of the peritoneum

What are the accessory organs of the digestive system?

Salivary glands, liver, gallbladder, and pancreas

What are the digestive tract organs?

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus

Salivary Glands (Diagram definition)

Secrete saliva which contains digestive enzyme for carbohydrates

Liver (Diagram definition)

Major metabolic organ; processes and stores nutrients; produces bile for emulsification of fats

Gallbladder (Diagram definition)

Stores bile from liver, sends it to the small intestine

Pancreas (Diagram definition)

Produces pancreatic juice; contains digestive enzymes, and sends it to the small intestine; produces insulin and secretes it into the blood after eating

Mouth (Diagram definition)

Teeth chew food; tongue tastes and pushes food for chewing and swallowing

Pharynx (Diagram definition)

Passageway where food is swallowed

Esophagus (Diagram definition)

Passageway where peristalsis pushes food to stomach

Stomach (Diagram definition)

Secretes acid and digestive enzyme for protein; churns, mixing food with secretions, and sends chyme to small intestine

Small Intestine (Diagram definition)

Mixes chyme with digestive enzymes for final breakdown; absorbs nutrient molecules into body; secretes digestive hormones into blood

Large Intestine (Diagram definition)

Absorbs water and salt to form feces

Rectum (Diagram definition)

Stores and regulates elimination of feces

What is the pathway that food follows

Mouth → pharynx → esophagus → stomach → small intestine → large intestine → rectum → anus

How many pairs of salivary glands do humans have?

3

What do the salivary glands secrete?

Salivary amylase

What does salivary amylase begin in the digestive process?

Carbohydrate digestion

What do tonsils do?

Fight diseases

What type of tissue are tonsils made of?

Lymphatic tissue

What is the teeth’s function?

Mechanical breakdown of food

What is the tongue covered in?

Taste buds

What does the tongue assist in doing?

The mechanical breakdown and movement of food

The tongue forms ____ and moves it toward the pharynx

Bolus

Bolus

Mass of chewed food created by the tongue

How many teeth are in adults?

32

How many deciduous teeth are in babies?

20

What is each tooth made of?

A crown and a root

What covers the crown of teeth?

Enamel and dentin

Pharynx

A cavity between the mouth and esophagus that serves as a passageway for food (and air)

Esophagus

A long muscular tube that carries food to the stomach

What are the two ways we swallow food?

Voluntarily and involuntarily

What is the voluntary phase of swallowing food?

In the beginning, when food is being swallowed from the mouth into the pharynx is a voluntary act

What is the involuntary phase of swallowing food?

Once the food in the pharynx, swallowing becomes a reflex

Epiglottis

Covers the voice box to make sure food is routed into the esophagus

How does food move down the esophagus?

Peristalsis

Peristalsis

The rhythmic contraction of the GI tract

Stomach Functions

Store food, start digestion of proteins, and control movement of chyme into the small intestine

Stomach Physical Description

J-shaped organ with a thick wall

How many layers of muscle in the muscularis layer of the stomach wall are there?

3

What do the 3 layers of muscle in the stomach wall help with?

Mechanical digestion and allow it to stretch

The mucosa layer of the stomach has deep folds called ____, and _____ pits that lead into _____ glands that secrete _____ juice

Rugae; gastric

What does gastric juice contain?

Pepsin, HCl, and mucus

Pepsin

An enzyme that breaks down proteins

What does HCl in the stomach do?

Gives the stomach a pH of 2 which activates pepsin and helps kill bacteria found in food

What bacterium lives in the mucus of gastric juice?

Helicobacter pylori

What can helicobacter pylori in stomach mucus cause?

Gastric ulcers

What substance does the stomach empty into the small intestine?

Chyme

How long does it take for the stomach to empty chyme into the small intestine?

2-6 hours

How long is the average small intestine?

6 m/18 ft

What do the enzymes secreted by the pancreas into the small intestine do?

Digest carbs, proteins, and fats

What is secreted by the gallbladder into the small intestine?

Bile

What does the bile from the gallbladder in the small intestine do?

Emulsify fats

What does the absorption of digested food depend on in the small intestine?

A large surface area

How is a large surface area created in the small intestine?

Numerous villi and microvilli

Where do amino acids and sugar enter after being absorbed in the microvilli?

Capillaries

Where do fatty acids and glycerol enter after being absorbed in the microvilli?

Lacteals (small lymphatic vessels)

What is the process of carbohydrate digestion?

Carbohydrate → Pancreatic amylase → maltase → glucose → villi → blood capillary

What is the process of protein digestion?

Protein → trypsin → peptides → peptidase → amino acids → villi → blood capillary

What is the process of fat digestion?

Bile + fat globules → emulsification droplets → lipase → monoglycerides and free fatty acids → chylomicron → lymphatic capillary

Carbohydrate digestion major digestive enzymes

Salivary amylase, pancreatic amylase, maltase, and lactase

Protein digestion major digestive enzymes

Pepsin, trypsin, and peptidases

Fat digestion major digestive enzymes

Lipase

Nucleic acids digestion major digestive enzymes

Nuclease and nucleosidases

What is salivary amylase produced by and its site of action?

Salivary glands and mouth

What is pancreatic amylase produced by and its site of action?

Pancreas and small intestine

What is maltase produced by and its site of action?

Small intestine and small intestine

What is lactase produced by and its site of action?

Small intestine and small intestine

What is pepsin produced by and its site of action?

Gastric glands and stomach

What is trypsin produced by and its site of action?

Pancreas and small intestine

What is peptidases produced by and its site of action?

Small intestine and small intestine

What is nuclease produced by and its site of action?

Pancreas and small intestine

What is nucleosidases produced by and its site of action?

Small intestine and small intestine

What is lipase produced by and its site of action?

Pancreas and small intestine

What does salivary amylase digest?

Starch + water → maltose

What does pancreatic amylase digest?

Starch + water → maltose

What does maltase digest?

Maltose + water → glucose + glucose

What does lactase digest?

Lactose + water → glucose + glucose

What does pepsin digest?

Protein + water → peptides

What does trypsin digest?

Protein + water → peptides

What does peptidases digest?

Peptide + water → amino acids

What does nuclease digest?

RNA and DNA + water → nucleotides

What does nucleosidases digest?

Nucleotide + water → base + sugar + phosphate

What does lipase amylase digest?

Fat droplet + Water → monoglycerides + fatty acids

What is the pH of salivary amylase?

Neutral

What is the pH of pancreatic amylase?

Basic

What is the pH of maltase?

Basic

What is the pH of lactase?

Basic

What is the pH of pepsin?

Acidic