The Digestive System

Major Functions Digestion- Break down food into the nutrients the body can absorb. Absorption- Take out nutrients out of the food we eat and deliver it to the cells in our body. Eliminate solid wastes that is not needed by the body.

Digestion Processing of food Types Mechanical (physical) Chew Tear Grind Mash Mix Chemical- uses catabolic reactions and enzymes to break down food Saliva Stomach Acids Bile used to break down fats Examples of Mechanical Digestion

Digestion Phases Ingestion Movement Digestion Absorption Further digestion

Digestive System Organization Gastrointestinal (Gl) tract Tube within a tube Direct link/path between organs Major Organs: MouthPharynx Esophagus Stomach  Small Intestines Large Intestines Rectum

Digestive System Organization Accessory Organs Not in tube path Organs Teeth Tongue Salivary glands Liver Gall bladder Pancreas

Mouth- where digestion begins Teeth- Mechanical Digestion Salivary Glands- Chemical digestion of compounds such as starch

Teeth- Mechanical Digestion

Surface of the Tongue

The Major Salivary Glands

Deglutition (swallowing) __________________ Deglutition (swallowing) Peristalsis Sequence A. Voluntary stage Push food to back of mouth B. Pharyngeal stage Raise pallate - C. Esophageal stage- Contract pharyngeal muscles, open esophagus, start peristalsis

Esophagus Usually collapsed (closed) Functions Secrete mucous Transport food to the stomach

Peristalsis Contractions of smooth muscles that push food down the digestive tract

Esophagus Sphincters Abnormalities Upper Lower Achalasia Atresia Hernia Barret’s esophagus Esophageal varices

Stomach Usually “J” shaped Mucous membrane G cells – make gastrin Goblet cells – make mucous Gastric pit – Oxyntic gland – Parietal cells – Make HCl Chief cells – Zymogenic cells Pepsin Gastric lipase Very Acidic, but the cells are produced faster than they die

Anatomy of the Stomach

Stomach Functions 5. Absorbs 1. Mix food- Mechanically 2. Reservoir- Store food 3. Start chemical digestion of Protein Nucleic acids Fats 4. Destroy some bacteria 5. Absorbs Alcohol Water Lipophilic acid B 12

Stomach Function- To mix, break down (chemically and mechanically), and store food. Inner surface thrown into folds – Rugae Contains enzymes that work best at pH 1-2 (VERY ACIDIC)

Stomach Food leaves the stomach as a soupy mixture called chyme

Small Intestine Function- Major site of chemical digestion and absorption. Movements Peristalsis Absorbs 80% ingested water Vitamins Minerals Carbonates Proteins

Structure of the Villi in the Small Intestine Villi- Increase surface area for absorption.

Small Intestine- Accessory Organs Liver- Creates bile that is used to break down fats. Gal bladder- Stores bile and releases it into the small intestines Pancreas- Creates pancreatic juices that neutralize the chyme.

Anatomy of the Large Intestine

Large Intestine Function- To reabsorb water from digested wastes to make solid wastes. - No villi No permanent circular folds Smooth muscle Chyme dehydrated to form feces

Feces Formation and Defecation “whats in it?” Chyme dehydrated to form feces Feces composition Water Inorganic salts Epithelial cells Bacteria Byproducts of digestion Defecation Peristalsis pushes feces into rectum Rectal walls stretch until full

Anatomy of the Large Intestine

The Organs and Positions in the Abdominal Cavity

Video of the digestion of food- The whole picture http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html

Digestive Disorders Chrone’s Disease (inflammatory bowel syndrome)- Inflammation of the intestines

Digestive disorders Blind loop syndrome- Blind loop syndrome occurs when part of the intestine becomes bypassed, so that digested food slows or stops moving through the intestines. This causes bacteria to grow too much in the intestines and leads to problems in absorbing nutrients. Diarrhea- increased frequency of watery feces. Causing dehydration and abdominal pain.

Digestive Disorders Phenylketonuria (PKU)- is a rare condition in which a baby is born without the ability to properly break down an essential amino acid called phenylalanine.

Symptoms Lighter skin and hair color Delayed mental and social skills Bad breath and odor from skin and urine.

PKU is a recessive trait and therefore both parents must carry the allele to pass the trait.

Salivary gland Mouth Esophagus Liver Stomach Gal Bladder Pancreas Small Intestines Large Intestines Rectum Anus