The Digestive System

Chapter 19

Purpose of Digestive System

Humans are heterotrophic

Hetero = other

Trophic = to feed

Cellular materials are needed for metabolism, growth, and repair of cells

Body accomplishes this by taking in food particles and breaking them down for cell functions

Functions of the Digestive System

Digestion: breakdown of food particles into nutrient components

Absorption: transfer of nutrients into circulation

Elimination: waste products unused or unneeded by the body excreted

Anatomy of Digestive System

Digestive Tract: passageway nutrient intake will follow in which particles will be broken down and absorbed

Accessory Organs: organs necessary for digestion, but not components of the digestive tract (ex. liver, gallbladder, pancreas,

salivary glands)

Anatomy of Digestive System: Oral Cavity

Anatomy of Digestive System: Oral Cavity

Teeth: mastication

Full adult set = 32 teeth

Salivary glands: lubricates food, secretes salivary amylase (breakdown of starch)

Tongue: deglutition (swallowing)

Movement of food particles into pharynx & esophagus

Anatomy of Digestive System: Pharynx (throat)

Oropharynx:

post. region of oral cavity

Nasopharynx:

swallowing pushes soft palate superior preventing food from entering this cavity

Anatomy of Digestive System: Pharynx (throat)

Laryngeal pharynx:

Food moved into esophagus by epiglottis preventing food particles from entering trachea

Anatomy of Digestive System:Esophagus

Food is lubricated by mucus

Food moved into stomach via peristalsis

(smooth muscle)

Separated from stomach by gastroesophageal sphincter

GERD

Anatomy of Digestive System:Stomach

Upper-left quadrant

Greater curvature

Lesser curvature

Rugae

Pyloric sphincter

Anatomy of Digestive System: Stomach

Cells in stomach lining secrete substances that combine to form “gastric juice”

HCl

Pepsin

Mucus

Chyme (food + gastric juice) enters S.I.

Anatomy of Digestive Sytem:Small Intestine

Longest portion of digestive tract

Smaller in diameter than L.I.

Smooth muscle moves chyme via peristalsis

3 regions:

duodenum

jejunum

ilium

Anatomy of Digestive System:Small Intestine

Large amt. of mucus produced to protect lining of S.I.

Majority of digestion occurs here w/ help from liver & pancreatic enzymes

Majority of absorption occurs here as well

Anatomy of Digestive System:Small Intestine

Villi: small, finger-like projections in S.I.

Increase S.A.

Linked to circulatory system through blood vessels allowing absorbed nutrients to enter blood stream

Anatomy of Digestive System:Large Intestine

3 regions:

Ascending colon

Transverse colon

Descending colon

Hepatic flexure

Splenic flexure

sigmoid colon empties into rectum

Rectum anus

Anatomy of Digestive System:Large Intestine

No digestion occurs in L.I.

Some H20 absorbed

Undigested food stored & formed into solid waste material - feces

Anatomy of Digestive System: Accessory Organs

Salivary Glands: secretes saliva which contains salivary amylase (facilitates breakdown of starch)

parotid glands

submandibular glands

sublingual glands

Anatomy of Digestive System: Accessory Organs

Liver:

Located in upper right quadrant

Blood supply – hepatic artery/portal vein

MAJOR FUNCTIONS:

Produces bile (fat breakdown)

Stores glycogen (reg. blood sugar)

Breakdown of RBC’s (by-product is bilirubin)

Detoxification (filtration of poisons)

Anatomy of Digestive System: Accessory Organs

Gallbladder:

Bile storage

Chyme enters duodenum, gallbladder contracts, bile moves from cystic duct into S.I.

Anatomy of Digestive System: Accessory Organs

Pancreas:

Produces enzymes that digest organic molecules (proteins, fats, carbs, nucleic acids)

Produces alkaline (basic) substance used to neutralize chyme in digestive tract

Pancreatic duct joins common bile duct

Abdominal Quadrants

Common Digestive System Injuries/Illnesses

Appendicitis

Liver cirrhosis: replacement of liver tissue with fibrous/scar tissue

Intestinal rupture

Pancreatic cancer

Colon cancer

Gallstones

(cholesterol 80%/bilirubin 20%)

(Veriform) Appendix

Physiology of Digestive Process

Enzymes: proteins that initiate or speed up the rate of chemical reactions

Required in every phase of digestion

Very specific for the job they carry out

Hydrolysis: breakdown of particles by water

Digestive juices

Dilute food

Chemical process

Digestion: MOUTH (1) food enters oral cavity

Mastication breaks down food

Saliva moistens food

ENZYME: salivary amylase initiates breakdown of starches into simple sugars

Digestion: ESOPHAGUS

HA! TRICK QUESTION!

There is NO digestion that occurs in the esophagus

(2) Food is moved through the esophagus via peristalsis

Digestion: STOMACH

(3) Food reaches stomach and gastric juice secreted by stomach cells

RUGAE increases SURFACE AREA for digestion

ENZYME: pepsin is activated by HCl

breaks down all protein in the diet

end product is CHYME moved into small

intestine

Digestion: SMALL INTESTINE

Majority of digestion occurs in small intestine

(4) Duodenum: chyme mixed with bile

Break down fats so pancreatic enzymes work

ENZYME: PANCREATIC ENZYMES

lipase, amylase, trypsin, nucleases

Absorption

Villi located in small intestine

Contain significant blood supply

(5) Nutrients absorbed through villi into blood vessels and transmitted throughout bloodstream

Excretion

(6) Waste products accumulated in LARGE INTESTINE or transmitted to Urinary System