Ch 21 Digestion and Nutrition Ingestion methods All

Ch 21 Digestion and Nutrition

Ingestion methods…. . • All animals consume energy – Herbivores – Carnivores – Omnivores

– Suspension feeders – particles suspended in water or air (clams, oysters, humpback whale) – Substrate feeders – live in or eat their way through (earthworm, maggot)

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

4 stages of Food Processing: • Ingestion Digestion Absorbtion Elimination

• Some organisms only have one opening, a gastrovascular cavity, they eat and eliminate out of the same opening. • Most have 2 openings, Alimentary canal, made up of a mouth and an anus.

• Breaking down of Organic Molecules: – Lipids (Fat) glycerol + fatty acid – Polysaccharide Monosaccarides – Proteins Amino acids – Nucleic acids nucleotides

• The Human Digestive system consists of an alimentary canal and accessory glands – Glands secrete digestive juices through ducts – Peristalsis: smooth muscle contractions that propel food through the digestive tract – Sphincters: muscle rings that regulate passage of food into and out of the stomach – Nutrient absorption occurs in the small intestine – Water is absorbed in the large intestine

• Digestion begins in the oral cavity • Salivary glands secrete: – 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 • Both mechanical and chemical digestion start in the oral cavity • Tongue: used to taste food and to form a bolus for swallowing

• After swallowing, peristalsis moves food through the esophagus to the stomach • Swallowing process: – Tongue pushes the food into the pharynx – Esophageal sphincter relaxes – Epiglottis covers larynx – Peristalsis pushes the food toward the stomach

• Stomach stores and breaks down food with acids and enzymes • Chemical digestion - gastric juice which contains mucus, enzymes (pepsin), and HCl (p. H~2) • Stomach interior is highly folded • Human stomach lining is fully replaced every three days • Gastrin: hormone stimulating the secretion of gastric juice • Chyme: nutrient rich “broth” formed after digestion of foods in the stomach – Leaves the stomach only a little at a time

• The small intestine is the major organ of chemical digestion and nutrient absorption • 3 Parts – Pyloric sphincter 1. Duodenum 2. Jejunum 3. illium • Nutrients that result from digestion are absorbed into the blood from the small intestine • Pancreas: secretes digestive enzymes and buffer solution • Liver produces bile to break down fats – Bile is stored in the gallbladder • Most digestion occurs in the duodenum • Nutrient absorption occurs in the jejunum and ileum Villi and microvilli: fingerlike projections that increase the surface area of the small intestine lining

The large intestine reclaims water and compacts the feces The small intestine empties into the cecum of the large intestine -The appendix - minor immune fnt. and attaches to the end of the cecum Large intestine functions: 1. Absorb water resulting in solidification of feces Inflammation of the lining cells may impair this function and result in diarrhea 2. Absorb vitamins produced by bacteria

• Rectum, holds feces till elimination through anus.

Adaptations of vertebrate digestive systems reflect diet • Carnivores often have large, expandable stomachs to accommodate large and infrequent meals • Herbivores & omnivores have longer canals to allow for digestion and absorption

• Most herbivores have extra chambers to house digestive microbes – May involved an enlarged cecum

• 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

Urinary System: Eliminates waste products from the body and maintains fluid/salt balance.

- The blood, which carries waste enters the kidneys through the Renal Artery

- blood moves through the kidneys, and is fitered by nephrons.

• Excess salts, water, urea, glucose, and amino acids make urine. • Stored in the medulla in tubes • Blood moves through kidneys 20 times an hour.

• Urine in kidneys Ureters (tubes) bladder Urethra toilet

Overview: A healthy diet satisfies 3 needs • All animals must obtain: 1. Fuel to power all body activities 2. Organic molecules to build the animal’s molecules 3. Obtain essential nutrients the animal cannot make for itself

Chemical energy powers the body • Cellular metabolism produces the body’s energy currency, ATP, by oxidizing organic molecules digested from food – The richest energy source is fat

The energy content of foods is measured in kilocalories • Rate of energy consumed by the body is called metabolic rate – Basal metabolic rate: the number of kilocalories a resting animal requires for basic living – Breathing, beating heart, maintain body temperature • Any excess energy is stored as glycogen or fat

• Diet must supply essential nutrients • Essential nutrients: must be obtained in preassembled form b/c cannot make – minerals – Malnourishment: results of long-term absence of one or more essential nutrients – 8 of the 20 amino acids are essential and must be obtained in the diet

• A healthy diet includes 13 vitamins and many essential minerals • Vitamin: organic nutrient – Helps activate enzymes during Chem Rxns – Ex: Vit. K – helps with blood clotting • Minerals: inorganic nutrients usually required in small amounts – Ex: calcium, phosphorus – You can have to much!!

Food Labels

• Read 21 - 24