Ch 8 Digestive System

Ch 8 Digestive SystemCh 8 Digestive System

StructuresStructures

Digestive System

•AKA alimentary canal

Aliment means to nourish

-ary means pertaining to

•Responsible for

•Intake & digestion of food

•Absorption of nutrients from digested food

•Elimination of solid waste products

Major Structures

•Oral Cavity

•Pharynx

•Esophagus

•Stomach

•Small intestine

•Large intestine

•Rectum

•Anus

•Accessory organs

–Liver

–Gallbladder

–pancreas

Gastrointestinal tract

•Divided into two sections

–Upper GI tract

•Mouth, esophagus, & stomach

–Lower GI tract

•Small intestine, large intestine, rectum, & anus

•Sometimes referred to as the bowels

Oral Cavity

•Lips aka labia

•Palate

–Hard palate-Soft palate

–Rugae -uvula

•Tongue

–Papillae aka taste buds

Oral Cavity

•Teeth

–Dentition refers to the natural teeth arranged in the

upper (maxillary) and lower (mandibular) arches.

•Primary or deciduous dentition

•Permanent dentition

–Edentulous means without teeth

•Periodontium – bone and soft tissues that surround teeth

–Gingiva aka gums, specialized mucous membranes

That surrounds the teeth

•Salivary glands secrete saliva that moistens food, begins the

digestive process, and cleanses the mouth

3 pairs; parotid, sublingual, & submandibular

Pharynx

•Aka throat

•Common passageway for both respiration &digestion

•What structure closes off and prevents food fromentering

the trachea during swallowing?

Esophagus

•Sometimes called the gullet

•A collapsible tube that leads from the pharynx tothe

Stomach

•Has a ringlike muscle at the end that controls theflow between the esophagus and the stomachcalled the lower esophageal sphincter or cardiacsphincter.

Stomach

•A saclike organ made of the fundus (upper,rounded part), the body(main part), and theantrum (lower part)

•Has folds in the mucosa lining called Rugae.These folds have glands that make the gastricjuices.

•The pylorus is the narrow passage that connectsthe stomach with the small intestine

•Pyloric sphincter is the muscle ring that controlsthe flow from the stomach to the duodenum ofthe small intestine.

Small Intestine

•Has 3 parts

–Duodenum, beginning

–Jejunum, middle

–Ileum, last portion

•Ileocecal sphincter controls the flow from the ileum of thesmall intestine into the cecum of the large intestine

•Has little hairlike or fingerlike projections called villi thatline the walls. These absorb fats and fat soluble vitamins

Large Intestine

•Major parts;

–Cecum is a pouchlike structure at the beginning of thelarge intestine. The vermiform appendix hangs fromthe lower portion.

–Colon

•Ascending colon

•Transverse colon

•Descending colon

•Sigmoid colon

–Rectum is the third major division

–Anus is the lower opening of the digestive tract. Flowof waste controlled by two anal sphincter muscles.

Accessory Digestive Organs

•Liver

–Found in the RUQ

–Removes excess glucose from bloodstream & stores itas glycogen

–Destroys old erythrocytes

•Bilirubin is a pigment produced from thedestruction of hemoglobin

–Makes & secretes bile

•Digestive juice that has enzymes that break downfat

Accessory Digestive Organs

•Gallbladder

–Pear shaped sac located inferior the liver

–Stores and concentrates bile for later use

•Pancreas

–Feather shaped organ located posterior to the stomach

–Has digestive and endocrine functions. We will discussthe endocrine function in a different chapter.

–Synthesizes and secretes pancreatic juices. Thesejuices help the body process protein, carbs, & fats, aswell as helping to neutralize stomach acids.

DIGESTION

Digestion

•The process by which foods are broken down into nutrientform the body can use.

•Enzymes are responsible for the chemical changes thatbreak foods down into simpler forms of nutrients thebody can use

•A nutrient is a substance, usually from food, that isnecessary for normal functioning of the body

Metabolism

•All the processes involved in the body’s use of nutrients.

–Anabolism, the building up of body cells or substances

–Catabolism, the breaking down of body cells orsubstances

Miscellaneous Terms

•Mastication aka chewing

•Peristalsis - wavelike contractions of the smooth muscles

•Chyme – semifluid mass of partly digested food

•Emulsification – digestion of fats by pancreatic juices

•Feces or stools

•Defecation or bowel movement

•Flatulence, flatus, or gas

•Borborygmus is the rumbling noise created by themovement of gas in the intestine