ch. 41 Flashcards
animal nutrition process
food is taken in , taken apart, and taken up
herbivores
eat mainly plants or algae
carnivores
eat other animals
omnivores
regularly consume animals as well as plants or algae
essential nutrients
required materials that an animal cannot assemble from simpler organic molecules
4 classes of essential nutrients
- essential amino acids
- essential fatty acids
- vitamins
- minerals
where are essential nutrients obtained
animal’s diet
how many amino acids do animals require
20
how many amino acids can animals synthesize from their diet
about half - essential
how do vegetarians obtain all essential amino acids
eating a varied diet of plant proteins
fatty acids purpose
membranes, signaling, storage fats
- mammals - linoleic acid
- eats seeds, grains, vegetables
vitamins
organic molecules required in the diet in very small amounts
how many vitamins are essential for humans
13
2 categories of vitamins
fat-soluble and water-soluble
minerals
simple inorganic nutrients, usually required in small amounts
malnutrition
failure to obtain adequate nutrition
effects of malnutrition
deformities, disease, and death
undernourishment
diet does not provide enough chemical energy
what happens to undernourished individuals
- use up stored fat/carbohydrates
- break down own proteins
- lose muscle mass
- suffer protein deficiency of brain
- die or suffer irreversible damage
epidemiology
study of human health and disease in populations
what are neural tube defects in babies a result of
deficiency in folic acid in pregnant mothers
ingestion
act of eating or feeding
different types of feeders
filter, substrate, fluid, bulk
filter feeders
which sift small food particles from water
substrate feeders
live in or on food source
fluid feeders
suck nutrient-rich fluid from a living host
bulk feeders
eat relatively large pieces of food
digestion
breaking food down into molecules small enough to absorb
mechanical digestion
chewing or grinding, increases surface area of food
chemical digestion
splits food into small molecules that can pass through membranes
- enzymatic hydrolysis
enzymatic hydrolysis
splits bonds in molecules with addition of water
absorption
uptake of small molecules by body cells
elimination
passage of undigested material out of the digestive system
what reduces the risk of animals digesting their own cells/tissues?
digestive compartments
intracellular digestion
- food particles engulfed by phagocytosis and pinocytosis
- food vacuoles fuse with lysosomes containing hydrolytic enzymes
what animal uses intracellular digestion
sponges
extracellular digestion
- breaks down food particles outside of cells
- occurs in compartments continuous with outside of body
- some animals have gastrovascular cavity
complete digestive tract
have both mouth and an anus
alimentary canal
digestive tube, complete digestive tract
accessory glands of digestion
salivary glands, pancreas, liver, gallbladder
what does saliva contain
mucus (water, salts, cells, glycoproteins), amylase (breaks down amylose)
what does saliva do
lubricate food
what does the tongue do
shape food into a bolus to help with swallowing
pharynx (throat)
junction that opens to both esophagus and trachea
what blocks food entry to the trachea
epiglottis
peristalsis
rhythmic contractions of muscles in wall of esophageal canal to push food down
stomach function
stores food and processes food into liquid suspension
chyme
mixture food and gastric juice
gastric juice composition
- hydrochloric acid and pepsin
- pH of 2
gastric juice function
kills bacteria and denatures proteins
pepsin
protease that breaks peptide bonds to cleave proteins into smaller peptides
parietal cells
secrete hydrogen and chloride ions separately into lumen (cavity) of the stomach
chief cells
secrete inactive pepsinogen, which is activated to pepsin when mixed with hydrochloric acid in stomach
what protects the stomach lining from gastric juice?
mucus
how often are stomach epithelial layers replaced by cell division
3 days
gastric ulcers
lesions in the lining caused by bacterium Helicobacter pylori
what churns the stomach’s contents
coordinated contraction
what prevent chyme from entering esophagus
sphincters
heartburn
if sphincter at top of stomach allows movement of chyme back to lower end of esophagus
longest compartment of the alimentary canal
small intestine
where does most enzymatic hydrolysis of macromolecules from food occur
small intestine
first portion of small intestine
duodenum
what occurs in the duodenum
chyme from stomach mixes with digestive juices from pancreas, liver, gallbladder, and small intestine
what does the pancreas produce
- trypsinogen
- chymotrypsinogen
what are trypsinogen and chymotrypsinogen activated into
trypsin and chymotrypsin
- in duodenum lumen
- solution alkaline, neutralizes acidic chyme
where is bile made and stored?
- made in liver, stored in gallbladder
bile salts purpose
- facilitate digestion of fats
- major component of bile
bile functions
- destroys nonfunctional red blood cells
why does the small intestine have microvilli and villi
to increase the surface area for absorption
brush border
created by microvillar surface of small intestine that greatly increases rate of nutrient absorption
transport across epithelial cells of small intestine
passive or active
- depends on nutrient
hepatic portal vein
carries nutrient-rich blood from the capillaries of the villi to the liver, then to the heart
function of the liver
- regulates nutrient distribution
- detoxifies many organic molecules
what do the epithelial cells of the intestines absorb
- fatty acids
- monoglycerides
- recombine them into triglycerides
chylomicrons
fats coated with phospholipids, cholesterol, and proteins to form water-soluble chylomicrons
where are chylomicrons transported
into a lacteal - lymphatic vessel in each villus
- deliver chlyomicron-containing lymph to large veins that return blood to heart
where does the alimentary canal end
large intestine
parts of the large intestine
- cecum
- colon - leads to rectum and anus
cecum
- fermentation of plant material
- connects where small/large intestines meet
colon
completes recovery of water that began in small intestine
appendix
extension of human cecum
- plays minor role in immunity
feces
wastes of the digestive system
- become more solid as they move through the colon
where do feces exit the body
- stored in rectum until eliminated through anus
- 2 sphincters between rectum and anus control bowel movements
stomachs of carnivores
large, expandable stomachs
digestive system of herbivores and omnivores
longer alimentary canals that carnivores
- reflects longer time needed to digest vegetation
intestinal bacteria function
- produce vitamins
- regulate development of intestinal epithelium
- regulate function of innate immune system
fermentation chambers
where mutualistic microorganisms digest cellulose
- in many herbivores
how many times do rabbits and rodents pass food through their alimentary canal
twice
- poo eaters
where are the most elaborate adaptations for an herbivorous diet
in animals called ruminants
- cattle, sheep
- “chew the cud”
digestive system of giant tube worms
no digestive system, obtain nutrients from mutualistic bacteria within their bodies
enteric division of nervous system
helps regulate digestive process
endocrine system
regulates digestion through release and transport of hormones
what hormone is released when food arrives in the stomach and stretches the stomach walls
gastrin
- enters blood and comes back to stomach
what does gastrin stimulate the production of
gastric juices
what hormones are released by small intestine
- CCK and Secretin
- stimulate pancreases to release bicarbonate/digestive enzymes
- inhibit peristalsis and release of gastric juice
CCK
stimulates contraction of gallbladder and release of bile
where is energy first stored in humans
in liver and muscle cells in the polymer glycogen
where is excess energy stored
fat in adipose cells
what type of energy does human body use first
- expends liver glycogen first
- then muscle glycogen and fat
what is central to maintaining metabolic balance
synthesis and breakdown of glycogen
what is the site of glucose homeostasis?
liver
what triggers the synthesis of glycogen
carbohydrate-rich meal raises insulin levels
what triggers the breakdown/release of glucose
low blood sugar causes glucagon increase
what does insulin do
act on nearly all body cells to stimulate glucose uptake from blood
- except brain cells: take up glucose whether or not insulin is present
where are glucagon and insulin produced
islets of the pancreas
- alpha cells - glucagon
- beta cells - insulin
diabetes mellitus
caused by deficiency of insulin or decreased response to insulin in target tissues
- cells unable to take up enough glucose to meet metabolic needs
- level of glucose in blood may exceed capacity of kidneys to reabsorb it
- sugar in urine is one test for diabetes
type I diabetes
- autoimmune disorder - immune system destroys beta cells of pancreas
- appears during childhood
- treatment; insulin injections several times per day
type II diabetes
- non-insulin dependent
- failure of target cells to respond normally to insulin
- excess body weight and diet
- generally appears after 40 years
how do hormones regulate long/short-term appetite
affect “satiety” center in brain
ghrelin
hormone secreted by stomach wall that triggers feeling of hunger
insulin and PYY
PYY - hormone secreted by small intestine after meals
- both suppress appetite
leptin
suppresses appetite and plays role in regulating body fat levels
- produced by adipose
