Chapter 15 - BIO 110

Gastrointestinal tract

The tract that includes several accessory glands releasing their secretions.

Structure of gastrointestinal tract

Begins at the mouth and includes the pharynx, esophagus, stomach, small intestine, and large intestine.

Mechanical digestion

The physical breaking of food into smaller pieces.

Chemical digestion

The breaking of chemical bonds so that complex molecules are broken into smaller subunits.

Hard palate

Reinforced with bone and located toward the front of the mouth.

Soft palate

Muscle only, located toward the back; prevents food from entering nasal cavities during swallowing.

Function of the mouth

Begins mechanical and chemical digestion, monitors food quality, prepares food for swallowing.

Function of the teeth

Mechanical digestion breaks food into smaller pieces.

Incisors

Teeth that clip and slice food.

Canines

Teeth that puncture and tear food.

Molars

Teeth that crush food.

Structure of the teeth

Consists of crown above the gum and root below the gum.

Layers of the teeth

Includes pulp (innermost), dentin (hard bonelike), and enamel (nonliving covering crown).

Salivary glands

Include sublingual (below tongue), submandibular (below jaw), and parotid (in front of ears).

Saliva

Moistens food, binds food with mucus, and contains salivary amylase for starch digestion.

Tongue

A large skeletal muscle important for speech and food manipulation.

Pharynx

A passageway shared by the respiratory and digestive systems.

Esophagus

Muscular tube that transports food from the pharynx to the stomach.

Structure of the stomach

J-shaped expandable sac with circular muscles at each end.

Functions of the stomach

Stores food, regulates release to small intestine, liquefies food, and begins protein digestion.

Gastric glands

Secrete hydrochloric acid and intrinsic factor.

Stomach protection

Protected by mucus, pepsin in inactive form, and rapid lining replacement.

Structure of the small intestines

Duodenum, jejunum, and ileum.

Functions of the small intestines

Chemical digestion and absorption.

Chemical digestion in small intestines

Digests carbohydrates, proteins, fats, and nucleic acids into simplest forms.

Surface area of small intestines

Increased by pleated lining, villi, and microvilli.

Pancreatic juice

Contains digestive enzymes and bicarbonate; drains into the small intestine.

Liver

Largest internal organ; produces bile, regulates blood glucose, and aids lipid transport.

Gallbladder

Muscular pear-shaped sac that stores, modifies, and concentrates bile produced by the liver.

Structure of large intestines

Includes cecum, colon, rectum, and anal canal.

Functions of the large intestines

Absorbs water from indigestible food residue and stores/eliminates feces.

Colon structure

Pouch at junction of small and large intestines.

Colon function

Absorbs water and ions; contains beneficial bacteria that produce vitamins.

Nervous system control of digestion

Controls quick or anticipatory digestive processes.

Hormonal control of digestion

Regulates longer-lasting digestive processes.

Nutrients

Substances in food that provide energy or serve structural or functional roles.

Lipids

Provide nine calories per gram and include fats, oils, and cholesterol.

Carbohydrates

Provide four calories per gram.

Proteins

Comprise chains of amino acids; provide four calories per gram.

Vitamins

Needed in small amounts, serve as enzymes or coenzymes.

Minerals

Inorganic substances essential for various life processes.

Food label

Helps choose foods for nutrient intake and limit harmful substances.

Energy balance

Basal metabolic rate: minimal energy needed to keep an awake, resting person alive.

Obesity

Excess body fat beyond height-weight recommendations.