digestive system

Lips

Surround the oral cavity opening

Palate

roof of the mouth

Hard palate

anterior portion of
the palate; covered with
specialized mucous membrane

Soft palate

flexible posterior
portion; during swallowing,
closes off the nasal passage

Uvula

hangs from the free edge
of the soft palate; plays a role in
some speech sounds

Tongue

very strong, flexible, and muscular

Dorsum

upper surface of the tongue

Papillae

tough protective covering; contains small bumps with taste buds

Sublingual surface

highly vascular tissues under the tongue

Lingual frenum

band of tissue under the tongue

Periodontium

structures that surround, support, and are attached to the teeth

Gingiva (masticatory mucosa, or gums)

mucous membrane; covers the bone of the dental arches and surrounds the neck of the teeth

Sulcus

area of space between a tooth and the surrounding gingiva

Maxillary arch

upper jaw; bones of the lower surface of the skull

Mandibular arch

lower jaw; separate bone; only movable component of the joint

Temporomandibular joint (TMJ)

joining of the maxillary and mandibular arches

Incisors and canines

teeth used for biting and tearing

Premolars (bicuspids) and molars

teeth used for chewing and grinding

Primary dentition (baby teeth)

20 teeth; replaced by permanent teeth

Permanent teeth

32 teeth designed to last a lifetime

Crown

visible portion of tooth covered in enamel

Roots

hold tooth in place

Cervix

neck of the tooth

Dentin

portion above the gum line

Pulp

blood vessels and nerves; contained in the pulp cavity

Saliva

• Colorless liquid

• Maintains moisture in the mouth

• Contains digestive enzyme amylase

Parotid glands

ducts are inside the cheek

Sublingual glands

ducts are located on the floor of the mouth under the tongue

Submandibular glands

ducts are located on the floor of the mouth near the mandible

The Pharynx

• Passageway for both respiration and digestion

• Plays an important role in deglutition (swallowing)

Epiglottis

Lid-like structure that closes off trachea entrance (windpipe)

Lower esophageal sphincter (cardiac sphincter)

• Muscular ring between the esophagus and stomach

• Relaxes during swallowing to allow food to enter the stomach

• Normally opens to allow the flow of food into the stomach

• Closes to prevent the stomach contents from regurgitating

The Stomach

• Sac-like organ

  • Fundus (upper, rounded part) 

  • Body (main portion)

  • Antrum (lower part)

Rugae

folds in the mucosa lining the stomach

Gastric juices

aid food digestion

Pyloric sphincter

• Ring-like muscle at the stomach base

• Controls the flow of partially digested food

Pylorus

connects the stomach to the small intestine

The Small Intestine

• Extends from the pyloric sphincter to the first part of the large intestine

• Coiled organ up to 20 feet in length 

• Consists of three sections: duodenum, jejunum, and ileum

Duodenum

First portion extending from the stomach to the jejunum

Jejunum

Middle portion extending from the duodenum to the ileum

Ileum

• Last, longest portion of the small intestine

• Extends from the jejunum to the cecum of the large intestine

The Large Intestine

• Extends from the end of the small intestine to the anus

• About twice as wide as the small intestine, but one-fourth as long

• Processes waste products of digestion

Cecum

• Pouch on the right side of the abdomen

• Ileocecal sphincter: ring-like muscle; controls flow from the ileum into the cecum

Vermiform appendix (appendix)

hangs from the lower portion of the cecum

Ascending colon

travels upward from the cecum to the undersurface of the liver

Transverse colon

passes horizontally across the abdominal cavity from right to left toward the spleen

Descending colon

travels down the left side of the abdominal cavity to the sigmoid colon

Sigmoid colon

S-shaped structure that continues from the descending colon above and joins the rectum below

Rectum

widest division of the large intestine; ends at the anus

Anus

lower opening of the digestive tract

Anorectal

refers to the anus and rectum as a single unit

The liver

• Removes toxins from the blood

• Turns food into fuel

• Uses bile to aid digestion of fats

• Breakdown of hemoglobin forms the pigment bilirubin

The biliary tree

• Provides channels through which bile is transported

• Small ducts join together like branches

• The trunk is the common hepatic duct

The gallbladder

• Pear-shaped organ about the size of an egg

• Located under the liver

• Stores and concentrates bile

• Contracts when bile is needed, forcing bile out through the biliary tree

The pancreas

• Soft, 6-inch-long, oblong gland

• Located behind the stomach

• Produces and secretes pancreatic juices that aid in digestion

• Aids in digestion and plays a role in the endocrine system

Digestion

Process by which complex foods are broken down into nutrients

Digestive enzymes

Responsible for breakdown of foods

Primary or macronutrients

• Provide the body with calories

• Carbohydrates, fats, and proteins

Micronutrients

• Required only in small amounts

• Vitamins and minerals

Metabolism

• Includes all of the processes involved in the body’s use of nutrients

• Consists of two parts: anabolism and catabolism

Anabolism

• Building up of body cells or substances from nutrients

• Opposite of catabolism

Catabolism

• Breaking down of body cells or substances, releasing energy and carbon dioxide

• Opposite of anabolism

Absorption

Process of transporting completely digested nutrients to the cells throughout the body

Villi

• Finger-like projections that cover the mucosa lining the small intestine

• Contain blood vessels and lacteals

• Absorb nutrients directly from the digestive system into the bloodstream

Lacteals

• Specialized structures of the lymphatic system

• Absorb fats and fat-soluble vitamins that cannot be transported directly by the bloodstream

• Transport these nutrients via lymphatic vessels

Mastication (chewing)

Breaks food down into smaller pieces, mixes it with saliva, and prepares it to be swallowed

Bolus

Mass of food that has been chewed and is ready to be swallowed

Peristalsis

• Series of wave-like contractions of the smooth muscles 

• Moves food downward with the help of gravity

• Moves in a single direction into the digestive system

Gastric juices

Hydrochloric acid and digestive enzymes that continue to breakdown food

Churning action

Works with the gastric juices by converting the food into chyme

Chyme

• Semifluid mass of partly digested food

• Passes out of the stomach, through the pyloric sphincter, and into the small intestine

Role of the Small Intestine

• Converts food into usable nutrients

• Completed as chyme is moved through the small intestine by peristaltic action

Role of the Large Intestine

Receives, stores, and eliminates waste products of digestion

Defecation (bowel movement [BM])

Evacuation or emptying of large intestines

Feces (solid body waste or stool)

expelled through the rectum or anus

Gut microbiota

• Billions of bacteria present in the large intestine

• Protect against infection and help maintain the immune system

Borborygmus

Rumbling noise; movement of gas in the intestine

Flatulence (flatus)

Passage of gas

Canker sores (aphthous ulcers)

gray-white pits with a red border in the soft tissues lining the mouth; associated with stress, certain foods, or fever

Cheilitis (cheilosis)

inflammation of lips; crack-like sores at the corners of the mouth

Leukoplakia

usually benign lesion (sore); develops on the tongue or inside of the cheek

Stomatitis

inflammation of the mucosa of the mouth

Oral thrush

fungal infection in the mouth caused by Candida albicans

Trismus (lockjaw)

any restriction to the opening of the mouth

Xerostomia (dry mouth)

lack of adequate saliva; diminished salivary gland secretions

Cleft lip

• Birth defect; deep groove of the lip running upward to the nose

• Failure of this portion of the lip to close during prenatal development

Cleft palate

• Failure of the palate to close during the early development of the fetus

• Can involve the upper lip, hard palate, and/or soft palate

• If not corrected, makes it difficult for the child to eat and speak

Bruxism

Involuntary grinding of the teeth that usually occurs during sleep

Dental caries (tooth decay or a cavity)

Caused by bacteria that destroy the enamel and dentin of the tooth

Dental plaque

• Forms near the gums and between the teeth

• Consists of bacteria and bacterial by-products

• Cause of dental caries and periodontal disease

Edentulous

without teeth

Halitosis (bad breath)

• Unpleasant odor coming from the mouth

• Can be caused by dental diseases or respiratory or gastric disorders

Malocclusion

Any deviation from the normal positioning of the upper teeth against the lower teeth

Dental calculus (tartar)

Dental calculus (tartar

Gum recession

shrinking of gingival tissue often associated with aging

Gingivitis

earliest stage of periodontal disease; inflammation affects only the gums

Acute necrotizing ulcerative gingivitis (trench mouth)

inflammation, bleeding, deep ulceration, and the death of gum tissue caused by abnormal growth of bacteria

Dysphagia

Difficulty in swallowing

Eosinophilic esophagitis (EoE)

Chronic immune system disease in which eosinophils builds up in the esophagus

Gastroesophageal reflux disease (GERD)

Upward flow of acid from the stomach into the esophagus