Chapter 8: Digestive System

• Breaking down food through mechanical and chemical digestion.

• After being digested, nutrient molecules are absorbed into the body and enter the bloodstream

• Any food not digested or absorbed is eliminated as solid waste

Three (3) main functions of the Digestive System

• Anus

• Esophagus

• Gallbladder (GB)

• Large Intestine

• Liver

• Mouth

• Oral Cavity

• Pancreas

• Pharynx

• Salivary Glands

• Small Intestine

• Stomach

The primary organs of the Digestive System:

Gastrointestinal (GI) System

Digests food and absorbs nutrients; Organs include oral cavity, pharynx, esophagus, stomach, small and large intestines, liver, gallbladder, pancreas, and salivary glands; Also called the digestive system

30

The gastrointestinal system, includes approximately _____ feet of a continuous muscular tube called the gut that stretches between two external openings, the mouth and the anus.

Gut

Name for continuous muscular tube that stretches between the mouth and the anus; Also called alimentary canal, gastrointestinal system/tract

Mouth

External opening of alimentary canal; receives food; also called the oral cavaity

Anus

Terminal opening of digestive tube

1. Oral Cavity (Mouth)

2. Pharynx

3. Esophagus

4. Stomach

5. Small intestine

6. Large Intestine

In order, beginning at the mouth and continuing to the anus, these organs are the

Pharynx

Medical term for throat; Passageway that conducts air from nasal cavity to trachea and also carries food and drink from mouth to esophagus; Divided into three sections: nasopharynx, oropharynx, and laryngopharynx

Esophagus

Tube that carries food from pharynx to stomach

Stomach

J-shaped muscular organ that acts as sac to collect, churn, digest, and store food; Composed of three parts: fundus, body, and antrum; Hydrochloric acid is secreted by glands in mucous membrane lining; Food mixes with other gastric juices and hydrochloric acid to form semisoft mixture called chyme, which then passes into duodenum

Small Intestine

Portion of digestive tube between stomach and large intestine and major site of nutrient absorption; three sections: duodenum, jejunum, and ileum; Also called small bowel

Large Intestine

Part of alimentary canal of digestive system extending from ileocecal valve to anus; consists of cecum, colon, rectum, and anal canal; Responsible primarily for reabsorption of water; Material remaining in large intestine is feces ready for defecation

Accessory Organs

Organs that assist in digestion but are not part of continuous tube from mouth to anus (alimentary canal); Includes liver, pancreas, gallbladder, and salivary glands

Liver

Large organ located in right upper quadrant of abdomen; serves many functions in body; Digestive system role includes producing bile, processing absorbed nutrients, and detoxifying harmful substances

Pancreas

Digestive system organ that produces digestive enzymes; Within endocrine system produces two hormones, insulin an glucagon; Endocrine gland that plays a role in regulating the level of glucose in the blood

Gallbladder

Small organ located just under the liver; Functions to store bile produced by the liver; Releases bile into duodenum through common bile duct

Salivary Glands

Exocrine glands with ducts that open into mouth; Produces saliva, which makes bolus of food easier to swallow and begins digestive process; Three pairs include parotid, submandibular, and sublingual

Ducts

The accessory organs are connected to the gut by ______.

The Urinary System

Describes how the kidneys eliminate excess water and dissolved waste substances by producing urine

• Glucose

• Triglycerides

• Amino Acids

Digestion includes the physical and chemical breakdown of large food particles into simple nutrient molecules like:

Intestines

Simple nutrient molecules are absorbed from the _____ and are circulated throughout the body by the cardiovascular system.

Growth / Repair

Simple nutrient molecules are used for _____ and _____ of organs and tissue.

Solid

Any food that cannot be digested or absorbed by the body is eliminated from the gastrointestinal system as ______ waste.

Mastication

Chewing movements of teeth

Teeth

Structures in mouth that mechanically break up food into smaller pieces during mastication

Food enters the mouth and is mechanically broken up by mastication

Digestion begins when:

Tongue

Muscular organ in flood or mouth; Works to move food around inside mouth and is also necessary for speech

Saliva

Watery fluid secreted into mouth from salivary glands; contains digestive enzymes that break down carbohydrates and lubricants that make it easier to swallow food

Deglutition

Swallowing

Taste Buds

Found on the surface of the tongue, Designed to detect bitter, sweet, sour, salty, and umami flavors in foods

Palate

Roof of mouth (oral cavity); Subdivided into the anterior portion is hard or bony, and posterior portion is soft or flexible

Uvula

Structure that hangs down from posterior edge of soft palate, helps in production of speech and is location of gag reflex;

Food enters the throat without swallowing (e.g., laughing with food in the mouth)

The gag reflex is stimulated when:

Epiglottis

Swallowing also results in the ______ covering the larynx to prevent food from entering the lungs

Cheeks

Form lateral walls of the oral cavity

Lips

Anterior opening of the oral cavity

Mucous Membrane

The entire oral cavity is lined with _______, a portion of which forms the gums that combine with connective tissue to cover the jawbone and seal off the teeth in their bony sockets.

Gums

Tissue around teeth; Also called gingiva

First

Teeth are an important part of the ____ stage of digestion.

Front

The teeth in the _____ of the mouth bite, tear, or cut food into small pieces.

Cuspids

Permanent teeth located between incisors and bicuspids that assist in biting and cutting food; Humans have four cuspids; Also called canine teeth or eyeteeth

Incisors

Biting teeth in very front of mouth that function to cut food into smaller pieces; Humans have eight

Bicuspids

Premolar permanent teeth having two cusps or projections that assist in grinding food; Humans have eight

Molars

Large, somewhat flat-topped back teeth; Function to grind food; humans have up to 12

Crown

Portion of tooth covered by enamel; Also artificial covering for tooth created to replace original enamel

Root

Portion of tooth below gum line

Cementum

Anchors root of a tooth into socket of jaw

Periodontal Ligaments

Small ligaments that anchor root of tooth in socket of jaw

Enamel

Hardest substance in body; Covers outer surface of teeth

Dentin

Makes up the main bulk of tooth; Under the enamel layer; Covered by enamel

Pulp Cavity

Hollow interior of tooth; Contains soft tissue made up of blood vessels, nerves, and lymph vessels

Root Canal

(1) Canal connecting pulp cavity of tooth to body; Contains nerves and blood vessels; (2) Dental treatment involving pulp cavity of root of tooth; Procedure used to save tooth that is badly infected or abscessed

Two

Humans have _______ sets of teeth.

Deciduous Teeth

20 teeth that begin to erupt between six and 28 months; Eventually pushed out by permanent teeth; Also called baby teeth

Permanent Teeth

Begin to erupt at about age six; Generally complete by age 18-20; Replaces baby teeth with 32 teeth

Oropharynx

Middle section of pharynx that receives food and drink from mouth

Laryngopharynx

Inferior section of pharynx; lies at the same level in neck as larynx

Epiglottis

Flap of cartilage that covers larynx when swallowing; Prevents food and drink from entering larynx and trachea (respiratory tract) and continues to the esophagus

Air

______ is also traveling through the oropharynx and laryngopharynx portions of the pharynx.

Thoracic Cavity

Food entering the esophagus is carried through the _________ and diaphragm and into the abdominal cavity, where it enters the stomach.

Peristalsis

Wavelike muscular movements in wall of digestive system tube (esophagus, stomach, small intestine, and colon) that function to move food along tube; Works to push food through the entire gastrointestinal tract

Fundus

Domed upper portion of organ such as stomach or uterus

Body

Main portion of organs such as stomach or uterus

Antrum

Tapered distal (lower) end of the stomach

Rugae

Prominent folds in mucosa of stomach; Smooth out and almost disappear allowing stomach to expand when full of food; Also found in urinary bladder

Hydrochloric Acid (HCl)

Acid secreted by glands in the mucous membrane in the stomach lining; Aids in digestion

Chyme

Semisoft mixture of food and digestive fluids that pass from stomach into small intestines; Food mixes with hydrochloric acid and gastric juices to form this liquid mixture

Spincters

Ring of muscle around tubular organ; Can contract to control opening of tube; Controls entry and exit from the stomach; Muscular valves

Cardiac Sphincter

Ring of muscle that prevents food and gastric juices from backing up into esophagus; Also called lower esophageal sphincter (LES) or gastroesophageal sphincter

Backward

During the process of regurgitation and vomiting, the brain causes the sphincters to relax, thereby allowing stomach contents to flow _________.

Pyloric Sphincter

Located at distal end of stomach; Controls passage of food into duodenum (small intestine)

Narrower

The small intestine is much ______ than the stomach and cannot hold as much as can the stomach.

Acidic

Chyme is highly ______ and must be thoroughly neutralized as it leaves the stomach.

Pyloric

The small intestine is located between the _____ sphincter (distal end of stomach) and the colon (portion of large intestine)

Villi

Highly folded finger-like projections from wall of small intestine; Serve to increase surface area for nutrient absorption

Microvilli

Microscopic projections extending from surface cell of an intestinal villus; Increase surface area of small intestine

Tennis Court

The small intestine is roughly the size of a ______.

20

The small intestine has an average length of ___ feet, is the longest portion of the alimentary canal and has three sections: the duodenum, the jejunum, and the ileum.

Duodenum

First section of small intestine; Location where digestion is completed after chyme mixes with digestive juices from pancreas and gallbladder; Extends from the pyloric sphincter to the jejunum and is about 10–12 inches long.

Jejunum

Middle portion of the small intestine; Site of nutrient absorption; About eight feet long

Ileum

Third portion of small intestine; Joins colon (large intestine) at cecum; Ileum and cecum are separated by ileocecal valve; At 12 feet in length, it is the longest portion of the small intestine

Ileocecal Valve

Sphincter between ileum and cecum

Fluid that remains after the complete digestion and absorption of nutrients in the small intestine enters the _______ intestine. Most of this fluid is water that is reabsorbed into the body.

Large

Feces

Waste product from food that cannot be digested and is expelled or defecated; Also called stool; This is the product evacuated in a bowel movement (BM)

Cecum

First portion of a colon; A pouch or saclike area in the first two to three inches at the beginning of the large intestine and colon; Appendix originates at end

Colon

Section of large intestine; Functions to reabsorb most fluid in digested food; Material that remains after water absorption is feces; Sections include cecum, ascending colon, transverse colon, descending colon, and sigmoid colon

Rectum

Area at end of large intestine for storage of feces that leads to anal canal

Anal Canal

Passageway between rectum and anus for feces to exit the body

Vermiform Appendix

Small worm-shaped outgrowth at the end of cecum; Reservoir for beneficial intestinal bacteria

Ascending Colon

Section of colon following cecum; Ascends right side of abdomen; Extends from cecum to the lower border of the liver

Transverse Colon

Section of colon that horizontally crosses upper abdomen from right side of body to left toward the spleen

Descending Colon

Section of colon that descends left side of abdomen where the sigmoid colon begins

Sigmoid Colon

Final section of colon; Follows S-shaped path to the midline of the body and terminates in rectum

Anal Spinchter

Rings of muscle that control defecation; his sphincter consists of rings of voluntary and involuntary muscles to control the evacuation of feces or defecation

Defecation

Evacuation of feces from rectum

Chemical

Accessory Organs function by producing much of the digestive fluids and enzymes necessary for _____ breakdown of food.

Bolus

Chewed-up morsel of food ready to be swallowed

Amylase

Digestive enzyme found in saliva that begins digestion of carbohydrates

Parotid Glands

Pair of salivary glands located in front of the ears