Chapter 32 Flashcards
What is an Animal’s Digestive System?
A body cavity or a tube that mechanically and chemically breaks down food to small particles to get absorbed into the internal environment. It also expels unabsorbed residues, and helps maintain homeostasis.
What is an Incomplete Digestive System?
Some invertebrates have it, food enters and waste leaves a saclike gut through a single opening at the body surface.
What is a Complete Digestive System?
All vertebrates have one, a tubular gut with two openings. A mouth at one end and an anus at the other, along the tube there are specialized regions that process food, absorb nutrients, and concentrate water.
Five Tasks of a Complete Digestive System
- Mechanical processing and motility2. Secretion3. Digestion4. Absorption5. Elimination
Complete Digestive System Task: Mechanical Processing and Moltility
Movements that break up, mix, and directionally propel food material.
Complete Digestive System Task: Secretion
Release of substances, especially digestive enzymes, into the lumen (the space inside the tube).
Complete Digestive System Task: DIgestion
Breakdown of food into particles, then to nutrient molecules small enough to be absorbed.
Complete Digestive System Task: Absorption
Uptake of digested nutrients and water across the gut wall, into extracellular fluid.
Complete Digestive System Task: Elimination
Expulsion of undigested or unabsorbed solid residues.
True or False: Digestive Systems differ due to diet-related adaptations
True, examples include: type of feeding structures and length of the gut
Gastrointestinal Tract in Humans
Gut, starts at the stomach and extends through the intestines to the tube’s terminal opening.
Oral Cavity in Humans
The mouth, food is partially processed here.
Tongue in Humans
Membrane-covered skeletal muscle that positions food for swallowing.
Pharynx in Humans
The throat, the entrance to the digestive and respiratory tracts.
Esophagus in Humans
A muscular tube in between the pharynx and stomach.
Stomach in Humans
A stretchable sac that stores food, secretes acid and enzymes, and mixes them together.
Complete Digestion System in Humans
Swallowing forces food and water from the mouth into the pharynx. Food continues through an esophagus to the stomach. Food processing starts in the mouth, most digestion and absorption occurs in the small intestine. The colon absorbs most of the remaining water and ions, which causes the wastes to compact. The rectum briefly stores the wastes before they are expelled through the anus.
Function of Teeth
Mechanically breakdown food into particles, salivary amylase begins the chemical digestion of carbohydrates.
Carbohydrate Digestion System
Includes the mouth, stomach, and small intestine.
Protein Digestion System
Found in the stomach and small intestine.
Lipid Digestion System
Found in the small intestine.
Nucleic Acid Digestion
Found in the small intestine.
Hormonal Controls of Digestion: Gastrin
Source: StomachEffect: Increases acid secretion by stomach
Hormonal Controls of Digestion: Cholecystokinin (CCK)
Source: Small IntestineEffect: Increases enzyme secretion by pancreas and causes contractions of gallbladder.
Hormonal Controls of Digestion: Secretin
Source: Small IntestineEffect: Increases bicarbonate secretion by pancreas and slows contractions in the small intestine.
Features of the Small Intestine Lining
- Lining is folded2. Millions of multicelled, fingerlike absorptive structures called villi extend from these folds, this villi house a lymph vessel and blood vessels 3. Most cells on the villus surface are brush border cells, which have membrane extensions called microvilli that project into the lumen.
Brush Border cell Functions
Both digestion and absorption.
Absorption Mechanisms
- Water and Solute Absorptions2. Fat Absorption
Colon Function
By absorbing water and mineral ions, the colon compacts undigested residues and other wastes as feces, which are stored briefly in the rectum before expulsion.
Purpose of Absorbed Sugars
Absorbed sugars are the human body’s most accessible energy source. Between meats, the brain draws on glucose in blood; other cells tap fat and glycogen stores, Adipose cells convert and store excess carbohydrates as fats.
Liver Functions
Forms bile (assists fat digestion), rids body of excess cholesterol and blood’s respiratory pigments. Controls amino acid levels in the blood; converts potentially toxic ammonia to urea. Controls glucose level in blood, major reservoir for glycogen. Removes hormones that served their function in blood. Removes ingested toxins, such as alcohol, from blood. Breaks down worn-out and dead red blood cells, and stores iron. Stores some vitamins.
Vitamins
Organic substances that are essential in very small amounts
Minerals
Inorganic substances that are essential for growth and survival.
