NOTES: CH 41 Animal Nutrition & Digestion
NUTRITION *Nutrition is the study of nutrients and how the body utilizes them!
*ESSENTIAL NUTRIENTS: nutrients that human cells cannot synthesize (i.e. certain amino acids)
CARBOHYDRATES Carbohydrate sources: -starch -glycogen -disaccharides -monosaccharides -cellulose (not digested, but provides FIBER)
CARBOHYDRATES How are carbohydrates used? -they are broken down (oxidized) which releases energy from glucose -excess glucose is stored as glycogen or converted to fat -most carbohydrates supply ENERGY
CARBOHYDRATES Carbohydrate requirements: -recommended that carbs make up 60% of a person s diet -physically active individuals require more fuel than sedentary ones -cellulose is a complex carbohydrate that humans cannot digest; provides FIBER
LIPIDS Lipid sources: -plant oils (unsaturated): corn oil, olive oil -animal products (saturated): butter, lard
LIPIDS How are lipids used? -the liver and adipose (fat) tissue work together to regulate triglyceride metabolism -lipids supply energy (long-term) -lipids are used to build cell structures -cholesterol is present in membranes and is also used to synthesize certain hormones
LIPIDS Lipid requirements: -recommended that not more than 30% of diet is fat intake -saturated fats should comprise no more than 10% of diet -must be sufficient to carry fat-soluble vitamins
PROTEINS Protein sources -meats, fish, poultry, dairy products, cereals, legumes -complete proteins have adequate amounts of all essential amino acids -incomplete proteins lack adequate amounts of one or more essential amino acids
PROTEINS How are proteins used? -structural (collagen, elastin, keratin) -enzymes (lactase, lipase, amylase) that control metabolic reactions -antibodies (fight infection) -messengers (hormones) -transport (hemoglobin; cell membrane proteins) -may provide energy
PROTEINS Protein requirements: -should make up about 10% of diet -must supply essential amino acids -pregnant and nursing women should increase their protein intake
VITAMINS (organic compounds required in small amounts)
VITAMINS Fat-soluble vitamins: -dissolve in (and stored in) fat -include vitamins A, D, E, and K -resist the effects of heat (therefore cooking does not destroy them)
VITAMINS Water-soluble vitamins: -dissolve in water -include the B vitamins and vitamin C -cooking or processing food destroys some water-soluble vitamins
MINERALS (elements, other than carbon, needed in small amounts for normal metabolism)
MINERALS Characteristics: -most are stored in the bones and teeth -can be incorporated into organic molecules (parts of enzymes, vitamins, etc.) -can be in the form of free ions (example: Ca 2+ ions in muscle cells)
MINERALS Mineral functions include: -structural materials -can function as part of enzymes -play vital roles in metabolic processes -maintaining ph of body fluids
MINERALS Examples of Major Minerals: -calcium (Ca) -chlorine (Cl) -phosphorus (P) -magnesium (Mg) -potassium (K) -sulfur (S) -sodium (Na)
MINERALS Examples of Trace Elements: -iron (Fe) -cobalt (Co) -manganese (Mn) -zinc (Zn) -copper (Cu) -fluorine (F) -iodine (I) -selenium (Se)
ADEQUATE DIETS an adequate diet provides sufficient: Energy Essential nutrients
*essential nutrients are necessary to support optimal growth, maintenance, and tissue repair malnutrition is poor nutrition due to: -Lack of food -Failure to make the best use of available food
MALNUTRITION *Malnutrition may be due to: UNDERNUTRITION (deficiency diseases) OVERNUTRITION (excess diseases)
Food processing occurs in 4 stages: 1) Ingestion (act of eating) 2) Digestion (into smaller molecules) 3) Absorption (of nutrients) 4) Elimination (of wastes)
DIGESTION Digestion is the process of mechanically and chemically breaking down foods and absorbing the breakdown products. The digestive system consists of an alimentary canal and several accessory organs.
Alimentary canal includes: mouth pharynx esophagus stomach small intestine large intestine rectum anus
Accessory organs are: salivary glands liver gallbladder pancreas
THE ALIMENTARY CANAL *The alimentary canal is a muscular tube that passes through the body s ventral cavity. Different regions carry out different functions.
Movements of the tube: MIXING MOVEMENTS and PROPELLING MOVEMENTS (include a wavelike motion called PERISTALSIS)
MOUTH (Oral Cavity) *receives food and begins digestion Tongue: -rough projections (PAPILLAE) on surface of tongue provide friction to handle food -papillae also contain TASTE BUDS
MOUTH (Oral Cavity) TEETH: teeth are used to mechanically break food into smaller pieces (this increases the surface area of food allowing digestive enzymes to react more effectively with the food molecules)
SALIVARY GLANDS *3 pairs of salivary glands secrete SALIVA, which moistens food, helps bind food particles, begins chemical digestion of carbohydrates, makes taste possible, and helps cleanse the mouth.
SALIVARY GLANDS secrete a watery fluid that contains the digestive enzyme AMYLASE (starts to break down starch and glycogen into smaller disaccharides) secrete a thick fluid called MUCUS, which binds food particles and lubricates during swallowing
Pharynx / Throat leads to esophagus and trachea when food is swallowed, trachea is blocked by EPIGLOTTIS (cartilage flap)
ESOPHAGUS ESOPHAGUS: a food passageway from the pharynx to the stomach -at distal end, circular smooth muscle fibers thicken and close the entrance to the stomach (prevents regurgitation); -if some of the acidic stomach contents are regurgitated (reflux) into the esophagus, may cause HEARTBURN
STOMACH *the stomach receives food, mixes it with gastric juice, initiates protein digestion, carries on a limited amount of absorption, and moves food into the small intestine.
Structure / Parts: STOMACH -has a capacity of about 1 L -separated from the small intestine by a powerful circular muscle: PYLORIC SPHINCTER
PYLORIC SPHINCTER
STOMACH Gastric secretions include: mucus digestive enzymes hydrochloric acid (HCl) *together, these secretions form GASTRIC JUICE
STOMACH PEPSIN: most important digestive enzyme in gastric juice -secreted in an inactive form: PEPSINOGEN -when it comes into contact with hydrochloric acid, it becomes the active PEPSIN (a protease)
STOMACH *a layer of thick mucus is produced by cells in the stomach s inner lining this protective coating prevents the stomach from digesting itself.
STOMACH Mixing and emptying actions: - CHYME = a mixture of food particles and gastric juice produced by mixing -chyme is emptied into the small intestine where chemical digestion continues
PANCREAS Structure of the pancreas: the pancreas produces PANCREATIC JUICE that is then secreted into the PANCREATIC DUCT, which leads to the DUODENUM (first portion of the small intestine)
PANCREAS Pancreatic juice contains enzymes that split or break down: carbohydrates proteins fats / lipids nucleic acids *pancreatic juice also has a high bicarbonate ion concentration that helps neutralize chyme and causes intestinal contents to be alkaline (basic).
Hormones regulate / control pancreatic secretion: as chyme enters the duodenum, the duodenal mucous membrane secretes the hormone SECRETIN stimulates secretion of pancreatic juice that has a high conc. of bicarbonate ions proteins and fats in the chyme within the duodenum cause the duodenal membrane to release the hormone CHOLECYSTOKININ! stimulates secretion of pancreatic juice that has a high conc. of digestive enzymes
CHOLECYSTOKININ (CCK) word #3 on my list!!!...let s see, so far we have: 1) Okazaki fragments 2) plasmodesmata 3) cholecystokinin 4) acetylcholinesterase 5)??? 6) rubisco 7) chaperonins 8) Islets of Langerhans 9) Batesian mimicry 10) nodes of Ranvier
LIVER Structure of the liver: The liver is divided into a large RIGHT LOBE and a smaller LEFT LOBE.
Liver functions include: metabolizing carbohydrates, lipids, and proteins; storage of some substances; filtering the blood; destroying toxins; secreting bile. **Bile is the only liver secretion that directly affects DIGESTION!!
Composition of BILE: BILE contains: *bile salts bile pigments cholesterol electrolytes *only the BILE SALTS have digestive functions!
GALLBLADDER the gallbladder stores bile between meals and releases bile into the small intestine via the CYSTIC DUCT and COMMON BILE DUCT cholesterol in the bile may form solid GALLSTONES which could block the ducts
Functions of Bile Salts: emulsify fats (surround and break them down into small droplets) aid in the absorption of fatty acids, cholesterol, and certain vitamins
SMALL INTESTINE *the small intestine receives secretions from the pancreas and liver, completes nutrient digestion, absorbs the products of digestion, and transports the residues to the large intestine.
SMALL INTESTINE the small intestine consists of the: DUODENUM (first 25 cm) JEJUNUM ILEUM
Structure of the small intestine wall: the wall is lined with VILLI that increase the surface area and aid in mixing and absorption (these, in turn, are covered with smaller extensions called MICROVILLI) intestinal glands are located between the villi
Secretions of the small intestine: secretions include: MUCUS and DIGESTIVE ENZYMES digestive enzymes split molecules of SUGARS, PROTEINS, and FATS into simpler forms *these secretions are released when stimulated by gastric juice, chyme, and stretching of the small intestine s wall
Absorption in the small intestine: the intestinal villi absorb the products of carbohydrate, protein, and fat digestion the villi also absorb electrolytes and water
**if food is rushed through the small intestine, not enough absorption of these things takes place and the result is DIARRHEA.
LARGE INTESTINE *the large intestine reabsorbs water and electrolytes, and forms and stores FECES
LARGE INTESTINE the large intestine consists of the: -CECUM -COLON (ASCENDING, TRANSVERSE, DESCENDING, and SIGMOID COLON) -RECTUM -ANAL CANAL
Functions of the Large Intestine: has little or no digestive function secretes mucus absorbs water and electrolytes forms and stores FECES
FECES consist of: -Water -Electrolytes -Bacteria -Undigested material -Mucus