Body Systems - Digestive System

Non-AP Bio 20 content

Feeding Strategies

How organisms take in/eat food. General types include herbivore, carnivore, omnivore. 4 kinds

1. Suspension feeders

2. Substrate feeders

3. Fluid feeders

4. Bulk feeders

Suspension feeders

Organisms that filter food particles from water

Substrate feeders

Organisms that live on or in a food source and eat their way through it. Typically a decomposer or parasite

Fluid feeders

Organisms that suck nutrient rich fluids from host organism (eg. through puncturing). Includes predators

Bulk feeders

Organisms that ingest large chunks of food at once

Homeostasis

Where the body maintains internal conditions such as temperature and chemical composition. Controlled through feedback inhibition. Bodies lose function if conditions are not kept at certain levels. Different than being in equilibrium

Feedback Inhibition/Negative Feedback Loop

How bodies control homeostasis. The product of a cycle inhibits the process of production when there is enough of it

Undernourished

Where not enough calories are consumed, stores of glycogen and fats will be broken down for fuel

Essential Nutrients

Materials that our bodies cannot produce/assemble but are necessary. Typically amino acids. When these are not present, may become malnourished

Malnourished

When one or more essential nutrients are missing

Stages of Food Processing

1. Ingestion

2. Digestion

3. Absorption

4. Elimination

Ingestion

Bringing food inside the digestive system

Digestion

Breaking down food into particles small enough to be absorbed. Generally accomplished through enzymatic hydrolysis

1. Intracellular digestion

2. Extracellular digestion

Intracellular digestion

Digestion occurring within the cell when vacuoles with food particles fuse with lysosomes

Extracellular Digestion

Digestion occurring outside body cells in specialized compartments (eg stomach)

Absorption

Cells absorbing nutrient molecules from digestive system

Elimination

Undigested material is expelled from digestive system

Digestive System

Organ/Body system responsible for breaking down food into usable materials and removing waste material from body

Gastrovascular Cavity

Digestive system composing of single sack with single opening found in very simple animals. Both digests and distributes nutrients

Complete Digestive tract/Alimentary Canal

More complex digestive system composed of a tube with two openings (mouth and anus)

Mechanical Digestion

Physically breaking up food to increase its surface area (chewing/mastication)

Peristalsis

Muscles in the digestive system (esophagus) squeezing food through it. Mechanically digests food

Chemical Digestion

Breaking up food with chemicals (enzymes and acids)

Components of the Digestive System

1. Oral Cavity/Mouth

2. Tongue

3. Pharynx

4. Epiglottis

5. Esophagus

6. Stomach

7. Small Intestine

8. Pancreas

9. Liver

10. Gall bladder

11. Large Intestine

12. Rectum

13. Anus

Oral Cavity/Mouth

Where mechanical digestion primarily occurs. Houses saliva glands that produce salivary amylase enzyme that breaks down starch and glycogen, softens food and begins chemical digestion.

Tongue

Muscle that allows food to be moved around in the mouth, manipulates it into clumps to be easily swallowed/chewed. Tastes food to determine if it’s safe.

Pharynx

Junction between the mouth, esophagus, and trachea

Epiglottis

Flap at the back of the mouth (pharynx) that prevents food from falling into the trachea

Esophagus

Tube that connects the mouth and stomach. Peristalsis moves food down toward stomach

Stomach

Organ that has strong muscles used to mash food (mechanical digestion). Secretes strong chemicals (gastric juice) for chemical digestion. Regularly replaces its cells to prevent digesting itself. Has folded structure to increase surface area, positive feedback loop

Gastric Juice

Mixture of chemicals in the stomach composed of HCl and enzyme pepsin. Used to break down extra-cellular matrix of plant/animal tissue. Kills most bacteria, pH of ~2

Pepsin

An enzyme used for hydrolyzing proteins in the stomach

Pepsinogen

An inactive form of pepsin in the stomach that is activated by HCl in the stomach

Acid Chyme

Nutrient-rich fluid in the stomach produced by mechanical and chemical digestion

Mucus Cells

Secrete a mucus to lubricate and protect stomach

Parietal cells

Secrete HCl that lowers the pH of the stomach. HCl converts pepsinogen to pepsin

Pyloric Sphincter

Muscle/valve at the bottom of the stomach that regulates what can enter the small intestine

Small Intestine

Long tube where nutrients are absorbed across the epithelium in capillaries and lacteals. Sugars and amino acids into blood, fats into lacteal. Contains villi/microvilli to increase its surface area. Deactivates pepsin and neutralizes HCl (trypsin → trypsinogen)

Trypsin

Enzyme produced by pancreas used to break down proteins. Inactive form is trypsinogen, activated by endopeptidase

Duodenum

First ~25 cm of the small intestine. Uses chemicals from liver, gall bladder, and pancreas to complete most of digestion

Bile

Chemical produced by the liver and stored in the gall bladder. Contains bile salts (detergents or emulsifiers) to help break down fats

Villi and microvilli

Projections in the small intestine to increase surface area to help absorb nutrients. Where the circulatory and digestive systems connect.

Pancreas

Organ that produces chemicals to aid in the digestion of proteins, carbs, and lipids. Produces lipase, trypsin, erepsin, and amylase

Lipase

Enzyme to digest lipids. Produced by the pancreas

Trypsin

Enzyme produced by the pancreas to digest proteins into peptides. Inactive form is trypsinogen

Erepsin

Enzyme produced by the pancreas and small intestine to digest peptides into amino acids

Pancreatic Amylase

Enzyme used to digest starch produced by the pancreas

Liver

Organ that produces bile for the digestive system, regulates blood glucose levels. First place to get blood from digestive tract, has 2 capillaries in a row from hepatic portal vein. Filters blood

Gall Bladder

Stores and releases bile into digestive system. Bile used to emulsify fats

Large Intestine

Long tube that removes the last nutrients and water from digested food material. Compacts it and stores it for release

Rectum

Organ that expels waste material from body

Hormone Regulation

1. Ghrelin

2. Insulin

3. PYY

4. Leptin

Ghrelin

Produced by the stomach to indicate hunger, levels increase on diets. Stimulating hormone

Insulin

Produced by the pancreas. Increases blood sugar, suppresses appetite, converts sugars into glycogen. Suppressing hormone

PYY

Produced in the small intestine after a meal, suppresses appetite. Suppressing hormone

Leptin

Produced by adipose (fat) tissue, increased fat levels leads to hunger suppression. Suppressing hormone