chapter 30.3: the digestive system. functions of the digestive system -ingestion -take food into...
TRANSCRIPT
Chapter 30.3:The Digestive System
Functions of the Digestive System
- Ingestion- Take food into body
- Digestion- Mechanical
- Physical breakdown of food into small pieces
- Chemical- Enzymes break down food into
individual nutrients
- Absorption- Nutrients absorbed into body
- Elimination- Waste is compacted and eliminated
The Mouth- Teeth
- Incisors, cuspids, and bicuspids cut and tear food
- Molars grind food
- Saliva- Amylase breaks down starch
- Tongue- Forms a bolus, or ball of food - Pushes food into back of throat, or
pharynx
- Pharynx- Contains epiglottis, which blocks the
trachea and prevents choking
The Esophagus
- Connects the pharynx to the stomach
- Moves food by peristalsis- Smooth, wave-like muscle
contractions
The Stomach- Is a muscular sac that continues
mechanical and chemical digestion
- Chemical digestion- Protein is broken down by the enzyme pepsin
- Hydrochloric acid (HCl) also breaks down food
- Mechanical digestion- Stomach squeezes and churns food to
produce chime- Chyme is the mixture of food and digestive
enzymes
The Small Intestine- Begins at stomach and ends at large
intestine
- First section called the duodenum
- Chemical digestion by enzymes continues after food is pushed from stomach
- Enzymes are made in the small intestine walls, or from the pancreas
The Small Intestine
- Absorption of nutrients into the blood occurs through villi
- Villi are fingerlike projections that line the small intestine, and are covered with microvilli
- Microvilli are tiny projections of cells on villi that aid nutrient absorption
The Pancreas
- Connects to the small intestine by a duct
- Makes and secretes sodium bicarbonate, which neutralizes stomach acid
- Makes and secretes enzymes, which break down food
- Also produces hormones that regulate blood sugar
The Liver and Gallbladder
- Liver produces bile
- Gallbladder stores bile, and secretes it by a duct into the small intestine
- Bile helps break down fats
The Large Intestine- Also called the colon
- Connects to the small intestine and ends at the rectum
- Absorbs water from chyme
- Supports colonies of bacteria
- Compacts unused nutrients into solid waste
The Rectum and Anus
- Elimination occurs after the large intestine has compacted solid waste into feces
- Feces is stored in the rectum
- Anus is the muscle that controls release of feces
