chapter 34: animal nutrition and digestive system

obligate carnivores

only eat meat

facultative carnivores

can eat non-animal food but is best to eat mostly meat

incomplete digestive tract

one opening in body cavity (gastrovascular cavity)

food and waste both go thru mouth

complete digestive tract

two openings (alimentary canal)

food enters through mouth, waste exits through anus

monogastric digestive system

only one stomach

more than one stomach

crop

stores food in chicken

proventriculus

like human stomach, chemical digestion

gizzard

pebbles grind food

cloaca

excretes urine and feces in chickens

ruminants

have four stomachs

ruminants stomach cycle

grass taken to rumen → reticulum → omasum → food regurgitated to abomasum → intestine and out

rumen and reticulum

contain prokaryotes and protists to digest cellulose fiber

omasum

cud is regurgitated, chewed, and swallowed

removes water

abomasum

“true stomach”

equivalent of mono gastric stomach chamber where gastric juices are secreted

dentition in herbivores

incisors for clipping

premolars and molars for grinding

dentition in carnivores

pointed incisors and enlarged canines

dentition in omnivores

variety of specializations to accommodate both vegetation and meat

peristalsis

two layers of muscle allow for squeeze movement of esophagus

digestion is

extracellular

beta amylase

in salivary juice, digests starch

pharynx

where digestive and respiratory tract come together

soft palate

closes nasopharynx in presence of food

glottis

in larynx, produces voice

epiglottis

opens and closes air passage depending on presence of food

upper sphincter

separates esophagus and mouth

lower sphincter

separates esophagus and stomach

gastroduodenal sphincter

separates duodenum and stomach

oblique muscle

extra layer of muscle in stomach that helps with churning

gastric pits

deep folds in stomach

stomach cells

lined with columnar epithelial cells + muscle/goblet cells

parietal cells

produces HCl in stomach

goblet cells

produce mucus, prevents HCl form making holes in stomach lining (ulcer)

acid reflux

stratified squamous cells in esophagus die and are replaced with acidic columnar cells

precursor to cancer

pepsin

protease, digests proteins into peptides

chyme

mixture of digested food in stomach, small quantity passed into duodenum

neutralized by bicarbonates from pancreas

duodenum

has pancreatic juices and liver/gallbladder juice

villi

lined w absorption epithelial cells

microvilli

increases surface for better absorption

creates 4,000 square feet of small intestine

bile salts

emulsify fats (break into fat droplets)

expands into 4,000 square feet of small intestine

go into lymphatic vessel

carboxypeptidase

chews proteins one amino acid at a time from carboxyl end of amino acid

aminopeptidase

chews protein one amino acid at a time from amino terminal

dipeptidase

liver

has regenerative ability

produces bile

millions of hexagonal tubules

gallbladder

behind the bile

concentrates bile

pancreas

underneath stomach

produces trypsin: protein → peptides

lipase: fat droplets → glycerol and fatty acids

pancreatic amylase

converts starch → maltose

endocrine pancreas

produces insulin and glucagon

trypsin and chymotrypsin digest food further into smaller peptides and bicarbonate

large intestine

gets water back from chyme in small intestine

cecum

used for fermentation

appendix

vestigial organ

used in bacterial storage

constipation

large intestine takes too much water away

diarrhea

large intestine doesn’t take enough water away

lipid digestion

lipids emulsified by bile, form micelles

carbohydrate digestion

amylase in mouth

monosaccharides

glucose, fructose

disaccharides

lactose, sucrose

essential amino acids

not made in body, must be acquired through food

8 in adults, 9 in children

if needed amino acids aren’t there…

… proteins are truncated

fat-soluble vitamins

A, D, E, K

water soluble vitamins

B vitamins and vitamin C

vitamins

antioxidants

neutralize free radicals, which wear out body

sodium

muscle contraction

magnesium

cofactor for DNA

calcium

signaling molecule

phosphorous

present in DNA

chlorine

used for HCl, which is needed to convert pepsinogen to pepsin

potassium

maintains water balance, heartbeat

iodine

used for thyroid activity

iron

hemoglobin formation

can be toxic to the body

chief cells

produce pepsin, secreted as pepsinogen

protein digestion

in the stomach, pepsin breaks protein into peptides

in duodenum, trypsin, elastase, and chymotrypsin break peptides down smaller

carboxypeptidase, dipeptidase, and aminopeptidase reduce peptides to free amino acids, which are absorbed into the bloodstream through small intestines

lipid digestion

lipases break triglycerides → monoglycerides + fatty acids

packaged into micelles, absorbed by microvilli

converted back into triglycerides, which aggregate w cholesterol, proteins, and phospholipids to form chylomicrons

chylomicrons move into a lymph capillary, which transports to rest of body

carb digestion

salivary amylase

pancreatic amylase: starch → maltose

maltase: glycogen, starch → glucose

sucrase, lactase