Unit IV: Part 1 Digestive System Notes

I. All animals consume energy….. A. Herbivores B. Carnivores C. Omnivores

II. Ingestion Methods Differ A. Suspension feeders – particles suspended in water (clams, oysters, humpback whale)

B. Substrate feeders – live in or eat their way through (earthworm, maggot)

C. Fluid Feeders: obtain food by sucking nutrient-rich fluids from a living host Ex: mosquitoes, ticks, butterflies D. Bulk Feeders: ingest large pieces of food Ex: snake, human

Ingestion  Digestion  Absorption  Elimination E. 4 Stages of Processing Food No matter what organism you are, what you eat or how you eat it… there are 4 stages of Food Processing: Ingestion  Digestion  Absorption  Elimination

III. Types of Digestive Systems A. Some organisms only have one opening, a gastrovascular cavity, they eat and eliminate out of the same opening.

B. Most have 2 openings, Alimentary canal, made up of a mouth and an anus

IV. The Human Digestive system consists of an alimentary canal and accessory structures. A. Alimentary canal structures: mouth, oral cavity, tongue, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus (in order in which they occur).

IV. The Human Digestive system consists of an alimentary canal and IV. The Human Digestive system consists of an alimentary canal and accessory structures. B. Digestive glands: salivary, pancreas, liver (Liver secretions stored in Gall bladder) C. Sphincters: muscle rings that regulate passage of materials into and out of a structure (gastroesophageal, pyloric, anus) D. Peristalsis: smooth muscle contractions that propel food through digestive tract.

1. Digestion begins in the oral cavity a. Mechanical: Teeth: ripping, tearing & grinding food into smaller pieces. Tongue: mixes food with saliva, pushes into pharynx. b. Chemical: Saliva amylase

1. Digestion begins in the oral cavity c. Salivary glands secrete saliva glycoprotein: slippery; protection of oral cavity and lubrication of food Buffers: neutralize food acids Antibacterial agents to kill bacteria Amylase: digestive enzyme most active against carbohydrates d. Tongue: used to taste food and to form a bolus for swallowing; pushes food into pharynx.

1. Digestion begins in the oral cavity e. Teeth (Structure implies function) Sharp teeth: ripping, tearing Flat teeth: grinding, crushing Angled teeth: tearing, slicing

2. Swallowing process: After swallowing, peristalsis moves Tongue pushes the bolus into the pharynx Esophageal sphincter relaxes Epiglottis covers larynx After swallowing, peristalsis moves food through the esophagus to the stomach

3. Food enters & is broken down in the stomach Mechanical: Very muscular, squeezing, churning of food Chemical: gastric juices (mucus, enzyme pepsin, HCl w/ pH of ~2)

3. Food enters & is broken down in the stomach Stomach is highly folded internally. (fully replaced every 3 days) Why? Turns food into chyme -nutrient broth (breaks down protein & carbs, starts breakdown of fats) Plyloric sphincter only allows chyme to leave the stomach a little at a time. (You stay fuller longer!)

Label your illustration Upper GI: Oral Cavity (teeth, tongue, saliva) Pharynx Esophagus Esophageal sphincter Stomach Pyloric sphincter

4. Small intestine receives chyme.

4. Small intestine receives chyme. Sm intestine has 3 parts: 1. Duodenum 2. Jejunum3. Illium Duodenum’s job: -Finishes up the digestion of fats with the help of bile. Bile was made in the liver, stored in the gall bladder and added to chyme as it passes through the duodenum. -Pancreas helps out by adding buffer solution to reduce the acidity of chyme.

4. Small intestine receives chyme. Jejunum & Illium’s job: absorbing all those nutrients that were broken down in the stomach and the duodenum. Villi & microvilli are fingerlike projections that increase surface area with which to absorb.

Villi & Microvilli that aid in absorption

The small intestine has taken all the good vitamins and nutrients out of the chyme. What do you have left? POOP (or fecal matter)

5. Fecal matter enters the large intestine (colon) where water is reclaimed and fecal matter compacted. Large intestine has 3 parts: cecum (attached appendix), rectum, anus The small intestine empties into the cecum of the large intestine.

5. Feces moves into lg. intestine (colon) Cecum- holding area for bacteria who help us break down cellulose (plant cell walls) that we have trouble digesting. Appendix- some believe the appendix played a role in immunity long ago.

What happens in the colon? Water is absorbed, resulting in solidification of the feces. Inflammation of the lining cells may impair this function. 2. Absorb vitamins produced by bacteria that were in the cecum.

V. Adaptations of vertebrate digestive systems reflect diet Meats are easy to digest: small cecum Plant materials are much harder to digest: long cecum to hold more bacteria who will help out with digesting the plant materials.

Ruminants: four-chambered stomach found in herbivorous mammals Produces “cud” which is further breakdown of the cellulose in plants. Chambers contain symbiotic microbes Digest the microbes along with the nutrients produced