Digestive System Flashcards
What is animal nutrition?
animal nutrition includes the processes by which food is ingested, digested, and absorbed into body cells and fluids
What is ingestion?
ingestion is the feeding method used to take food into the digestive cavity
What is digestion?
digestion is the splitting of carbohydrates, proteins, lipids, and nucleic acids in foods into chemical subunits small enough to be absorbed into an animal’s body fluids and cells
all organisms require sources of ____ and ____ for metabolism, homeostasis, growth, and reproduction
Matter and energy
all organisms require sources of matter and energy for ____, ____, ____, and ____
metabolism, homeostasis, growth, and reproduction
What is feeding?
for animals, meeting these nutritional requirements involves feeding, the uptake of food from the surroundings
What happens to food once it is ingested?
once food is ingested, digestive processes convert its molecules into absorbable subunits
What are herbivores?
Examples?
herbivores such as antelopes, horses, bison, giraffes, kangaroos, manatees, and grasshoppers obtain organic molecules primarily by eating plants
What are carnivores?
Examples?
carnivores such as cats, Tasmanian devils, penguins, sharks, and spiders, primarily eat other animals
What are omnivores?
Example?
such as crows, cockroaches, and humans, eat both plants and animals and, with appropriate digestive enzymes, may consume any source of organic matter
How is energy described?
energy requirements are described in terms of calories
How much is a calorie and a Calorie?
a calorie is the amount of energy required to raise the temperature of 1 g of pure water by 1°C
a kilocalorie [1 kcal = 4.2 kilojoules] equals 1,000 calories or one Calorie (capital C)
How many calories is fat, protein, and carbs?
carbohydrates contain about 4.2 kcal per gram, fats about 9.5 kcal per gram, and proteins about 4.1 kcal per gram
What is undernutrition?
animals whose intake of organic fuels is inadequate, or whose assimilation of such fuels is abnormal, suffer from undernutrition
What is malnutrition?
undernutrition is a form of malnutrition, a condition resulting from an improper diet
What is overnutrition?
overnutrition, the condition caused by excessive intake of specific nutrients, is another type of malnutrition
an animal suffering from undernutrition is starving for ____ ____ ____ ____ – taking in fewer calories than needed for daily activities
one or more nutrients
What happens in animals with chronic undernutrition?
animals with chronic undernutrition lose weight because they have to use energy-providing molecules of their own bodies as fuels
What do mammals used for food when undernourished?
What does this lead to?
mammals use stored fats and glycogen first, then proteins
use of proteins as fuel leads to muscle wastage and, in the long term, organ and brain damage, which leads to death
What do organic molecules serve as building blocks for?
organic molecules serve as building blocks for carbohydrates, lipids, proteins, and nucleic acids
What is it called when an animal cannot synthesize an organic molecule?
What is an example if an animal does not get these molecules?
animals synthesize many organic molecules – however, they cannot make certain essential amino acids and essential fatty acids, which must be obtained in the diet
EXAMPLE: In the absence of essential amino acids in the diet, an animal would have to break down its own proteins to provide amino acids for new protein synthesis
What are vitamins?
What is there general function?
vitamins are organic molecules required in small quantities that the animal cannot synthesize for itself
many are coenzymes, nonprotein
organic subunits that assist in enzymatic catalysis
What are essential minerals?
essential minerals are required inorganic elements such as calcium, iron, and magnesium
What are essential nutrients?
What do the vary between?
essential amino acids, fatty acids, vitamins, and minerals are known collectively as an animal’s essential nutrients
the list of essential nutrients differs from animal to animal
What are fluid feeders?
Example?
fluid feeders ingest liquids that contain organic molecules in solution (e.g., mosquitoes, hummingbirds)
What are suspension feeders?
Example?
suspension feeders ingest small organisms that are suspended in water (e.g., clams, baleen whales)
What are deposit feeders?
Example?
deposit feeders ingest particles of organic matter from solid material they live in or on (e.g., earthworms, crabs)
What are bulk feeders?
Example?
bulk feeders consume sizeable food items whole or in large chunks (most adult mammals, reptiles, birds, amphibians)
What are the four types of feeder?
fluid
suspension
deposit
bulk
What does the digestive process do?
digestive processes break food molecules into molecular subunits that can be absorbed into body fluids and cells
What does the breakdown of food molecules occur by?
breakdown occurs by enzymatic hydrolysis, in which chemical bonds are broken by the addition of H+ and OH–
What is enzymatic hydrolysis?
Enzymatic hydrolysis is the breakdown of a compound in presence of enzymes following its reaction with water
Hydrolysis reactions are the reverse of condensation reactions. In a hydrolysis reaction, a larger molecule forms two (or more) smaller molecules and water is consumed as a reactant. Hydrolysis (“hydro” = water and “lysis” = break) involves adding water to one large molecule to break it into multiple smaller molecules
Function:
amylase?
lipases?
proteases?
nucleases?
amylases hydrolyze starches
lipases hydrolyze fats and other lipids
proteases hydrolyze proteins
nucleases hydrolyze nucleic acids
sponges and some cnidarians break down food exclusively by ____ ____
intracellular digestion
What is the four step process of intracellular digestion?
cells take in food particles by endocytosis
an endocytic vesicle containing food particles fuses with a lysosome
containing hydrolytic enzymes
molecular subunits produced by hydrolysis pass from the vesicle to the cytosol
undigested material remaining in the vesicle is released to the outside of the cell by exocytosis
most invertebrates and all vertebrates digest food primarily by ____ ____
extracellular digestion
What are features of extracellular digestion?
specialized compartments prevent the animal from digesting its own body tissues
epithelial cells secrete enzymes that digest the food
What is extracellular digestion?
extracellular digestion – outside body cells, in a pouch or tube that is enclosed within the body
What is benefit of extracellular digestion?
extracellular digestion greatly expands the range of available food sources, and allows animals to eat large batches of food
____ and ____ (____) have a saclike digestive system with a single opening (a mouth) which serves both as the entrance for food and the exit for undigested material
flatworms and cnidarians (jellyfish)
What type of digestive system do flatworms and cnidarians (jellyfish) feature?
flatworms and cnidarians (jellyfish) have a saclike digestive system with a single opening (a mouth) which serves both as the entrance for food and the exit for undigested material
What system do flatworms and cnidarians lack?
How do they circulate nutrients to make up for this?
these animals lack a separate vascular system – water taken into the gastrovascular cavity circulates nutrients and other materials through the various tissue layers
flatworms and cnidarians (jellyfish) lack a separate vascular system – water taken into the ____ ____ circulates nutrients and other materials through the various tissue layers
gastrovascular cavity
In flatworms and cnidarians (jellyfish) where does digestion begin and where is it completed?
digestion begins in the gastrovascular cavity, and is completed intracellularly
most invertebrates and all vertebrates have a ____ ____ ____ ____ with two openings – the digestive contents move in one direction, from the ____ to the _____
tubular digestive tract system
mouth to the anus
the inside of the digestive tube (____) is functionally ____ to all body tissues (outside of the body)
lumen . . . external
Mechanical processing?
Mechanical processing:
chewing, grinding, and tearing food chunks into smaller pieces increases their mobility and the surface area exposed to digestive enzymes
Secretion of enzymes and other digestive aids?
release of enzymes and other substances that aid the process of digestion, such as acids, emulsifiers, and lubricating mucus, into the tube
Enzymatic hydrolysis?
food molecules are broken down through enzyme-catalyzed reactions into absorbable molecular subunits
Absorption?
the molecular subunits are absorbed from the digestive contents into body fluids and cells
Elimination?
undigested materials are expelled through the anus
What are five steps of digestion?
mechanical processing
secretion of enzymes and other digestive aids
enzymatic hydrolysis
absorption
elimination
What type of feeder is an earthworm? What does it feed on?
earthworm is a deposit feeder that feeds on soil particles
5 main steps of earthworm digestion?
- muscular activity moves particles through the esophagus into the crop, where they are stored and mixed with mucus
- this mixture enters the gizzard, which contains grains of sand, and is ground into fine particles
- the mixture enters a long intestine, where organic matter is hydrolyzed by enzymes
- muscular contractions move the mixture along
cells lining the intestine absorb molecular subunits - undigested residue is expelled through the anus
How do grasshoppers initially ingest food?
the grasshopper tear plant parts into small particles with hard external mouth parts
What is the digestive process of a grasshopper?
What structures does the plant material (food) pass through?
- salivary secretions in the pharynx begin digestion
- food moves through the esophagus, crop, and gizzard to the stomach, where it is hydrolyzed by enzymes in gastric ceca
- products are absorbed through walls of the ceca
- undigested contents move to the intestine for further digestion and absorption
- at the end of the intestine, water is absorbed and remnants are expelled through the anus
What do pigeons pick up and swallow whole?
a pigeon picks up seeds and swallows them whole
Digestive system of pigeon?
- seeds are moistened by mucus-filled saliva in the mouth
- seeds pass through the pharynx and tubelike anterior end of the esophagus to the pouchlike crop, which stores food
- the glandular anterior portion of the stomach (proventriculus) secretes digestive enzymes and acids
- seeds are ground up in the posterior end (gizzard)
- in the intestine, the liver secretes bile and the pancreas adds digestive enzymes
- products are absorbed, and undigested residues are expelled through the anus
What does the human digestive system provide?
the human digestive system provides fuel molecules and a wide range of nutrients, including the molecular building blocks of carbohydrates, lipids, proteins, and nucleic acids
What does types of nutrients does the digestive system absorb?
Can these nutrients be synthesized in the human body?
the digestive system also absorbs essential nutrients (amino acids, fatty acids, vitamins, and minerals) that cannot be synthesized within our bodies
What is the mammalian digestive system under the control of?
What are the structures with this system in order?
the mammalian digestive system is a series of specialized digestive regions under control of the nervous and endocrine systems: the mouth, pharynx, esophagus, stomach, small and large intestines, rectum, and anus
What are accessory organs of digestive system?
accessory organs include the salivary glands, exocrine pancreas, liver, and gallbladder
Is the digestive system identical between animals?
the digestive system is not identical in all mammals
How many essential amino acids? Name three?
there are 8 essential amino acids for adult humans: lysine, tryptophan, phenylalanine, threonine, valine, methionine, leucine, and isoleucine –
infants and young children also require histidine
What foods supply all essential amino acids?
proteins in fish, meat, egg whites, milk, and cheese supply all essential amino acids when eaten in adequate quantities
What is wrong with plan protein?
How to remedy this?
proteins of many plants are deficient in one or more essential amino acids, but certain combinations of plants, when taken together, contain all essential amino acids
What are two essential fatty acids?
2 fatty acids, linoleic acid and linolenic acid, are essential in the human diet
What are essential fatty acids required for?
both are required for synthesis of phospholipids that form parts of biological membranes and certain hormones
What is risk of low fat diet?
almost all foods contain these fatty acids – however, people on a low-fat diet that is deficient in linoleic acid and linolenic acid are at serious risk for developing coronary heart disease
How many known vitamins?
humans require 13 known vitamins in their diet
What general function of vitamins?
many metabolic reactions depend on vitamins, and the absence of one vitamin can affect the functions of others
What two general categories of vitamins?
vitamins fall into two classes: water-soluble (hydrophilic) vitamins and fat-soluble (hydrophobic) vitamins
Are vitamins stored in the body?
the body stores fat-soluble vitamins in adipose tissues – any amount of water-soluble vitamins above daily nutritional requirements is excreted in the urine
Where do most people get vitamins from?
most people get enough vitamins through a normal and varied diet that includes meats, fish, eggs, cheese, and vegetables
Who may need vitamin supplements?
supplements are usually necessary only for strict vegetarians, newborns, the elderly, and when taking certain medications
What is unique about vitamin D?
vitamin D differs from other vitamins because humans can synthesize it in the skin when exposed to ultraviolet light
What is unique about vitamin K?
humans cannot make vitamin K, but much of the requirement is supplied by bacterial activity in the large intestine
Vitamin A:
Common Source?
Main Function?
Effects of Deficiency?
Liver; fish oils; milk; eggs. (Beta-carotene, which is converted to vitamin A in the body, is in many plant foods such as sweet potato, spinach, and carrots.)
Component of visual pigments; bone metabolism; epithelial tissue maintenance
Night blindness; total blindness; skin disorders; decreased immunity
Vitamin D:
Common Source?
Main Function?
Effects of Deficiency?
Fish liver oil; egg yolk; fortified milk; produced in skin exposed to sunshine
Calcium and phosphorus absorption from gut
Bone deformities (rickets) in children; bone softening in adults
Vitamin E:
Common Source?
Main Function?
Effects of Deficiency?
Nuts; seeds; vegetable oils
Antioxidant; maintenance of cell membranes
Neuromuscular problems
Vitamin K:
Common Source?
Main Function?
Effects of Deficiency?
Intestinal bacteria; green vegetables
Promotes synthesis of blood-clotting protein by liver
Abnormal blood clotting, bleeding
Vitamin B1:
Common Source?
Main Function?
Effects of Deficiency?
Thiamine
Yeast; cereal grains; beans; nuts; meat
Connective tissue formation; needed for folate utilization; coenzyme forming part of enzyme in oxidative reactions
Beriberi (nervous system disorder that includes impaired sensory perception, limb weakness and pain, weight loss, cardiovascular malfunction)
Vitamin B2:
Common Source?
Main Function?
Effects of Deficiency?
Riboflavin
Whole grains, poultry, fish, egg white, milk, lean meat
Coenzyme
Skin lesions
Vitamin B3:
Common Source?
Main Function?
Effects of Deficiency?
Niacin
Fruits and vegetables; nuts; grains; meats
Coenzyme of oxidative phosphorylation
Pellagra (diarrhea, dermatitis, dementia)
Vitamin B5:
Common Source?
Main Function?
Effects of Deficiency?
Pantothenic acid
In many foods (meat, yeast, egg yolk especially)
Coenzyme in carbohydrate and fat oxidation; fatty acid and steroid synthesis
Fatigue; tingling in hands; headaches; nausea
Vitamin B6:
Common Source?
Main Function?
Effects of Deficiency?
Pyridoxine
Spinach, whole grains, tomatoes, potatoes, meat
Coenzyme in amino acid and fatty acid metabolism
Skin, muscle, and nerve damage
Vitamin B7:
Common Source?
Main Function?
Effects of Deficiency?
Biotin
Legumes; egg yolk; some synthesized by colon bacteria
Coenzyme in fat and glycogen formation and amino acid metabolism
Scaly skin (dermatitis); sore tongue; brittle hair; depression; weakness
Vitamin B9:
Common Source?
Main Function?
Effects of Deficiency?
Folic acid
Leafy vegetables; legumes; whole grains; yeast; liver; egg yolks
Coenzyme in nucleic acid and amino acid metabolism
Megablastic anemia
Vitamin B12:
Common Source?
Main Function?
Effects of Deficiency?
Cobalamin
Eggs; meats; dairy products
Coenzyme in nucleic acid metabolism; red blood cell formation
Anemia; brain and nervous system damage
What are the doses of macro and trace minerals?
many minerals are essential in the human diet:
macrominerals are required in large amounts (50 mg to more than 1 gram per day)
trace minerals are required in small amounts (some less than 1 mg per day)
What forms are minerals typically ingested in?
Overdose cause?
all minerals are ingested as compounds or as ions in solution
overdoses of some minerals (e.g., iron, sodium) can cause various problems
Ca:
Common Source?
Main Function?
Effects of Deficiency?
Calcium (Ca)
legumes; whole grains; nuts; dairy products; eggs
Bone and tooth formation; blood clotting; neural and muscle action
Stunted growth; loss of bone mass
Cl:
Common Source?
Main Function?
Effects of Deficiency?
Chlorine (Cl)
Table salt; vegetables; meat; dairy products; eggs
HCl formation in stomach; contributes to body’s acid–base balance; necessary for neural function and water balance
Muscle cramps; impaired growth; poor appetite
Mg:
Common Source?
Main Function?
Effects of Deficiency?
Magnesium (Mg)
Green leafy vegetables; legumes; nuts; dairy products; meat
Required for many enzymes; in bones and teeth; ATP processing
Weak, sore muscles; nervous system problems
P:
Common Source?
Main Function?
Effects of Deficiency?
Phosphorus (P)
Whole grains; legumes; nuts; dairy products; eggs; meats
In bones and teeth; component of nucleic acids, ATP, and phospholipids; energy processing
Muscular weakness; loss of minerals from bone
K:
Common Source?
Main Function?
Effects of Deficiency?
Potassium (K)
Many vegetables and fruits; whole grains; dairy products
Muscle and neural function; water balance; acid– base balance; main positive ion in cell
Muscular weakness; cardiac abnormalities or failure
Na:
Common Source?
Main Function?
Effects of Deficiency?
Sodium (Na)
Table salt; dairy products; eggs; meat
Acid–base balance; water balance; muscle and neural function; main positive ion in extracellular fluid
Muscle cramps
S:
Common Source?
Main Function?
Effects of Deficiency?
Sulfur (S)
Proteins from food sources, including legumes, nuts, dairy products, eggs, and meat
Component of body proteins
Same as protein deficiencies
I:
Common Source?
Main Function?
Effects of Deficiency?
Iodine (I)
Seafood; iodized salt
Thyroid hormone formation
Goiter (enlarged thyroid), with metabolic disorders
Fe:
Common Source?
Main Function?
Effects of Deficiency?
Iron (Fe)
Green leafy vegetables; legumes; whole grains; nuts; eggs; meats (particularly liver)
Component of hemoglobin, myoglobin, and electron carriers
Iron-deficiency anemia; weakness
Zn:
Common Source?
Main Function?
Effects of Deficiency?
Zinc (Zn)
Some vegetables; whole grains; legumes; nuts; fish; meats; many other foods
Component of many enzymes and some transcription factors; protein synthesis; DNA synthesis; cell division; immunity; wound healing
Impaired growth; loss of appetite; impaired immune function
What are 7 macrominerals?
Ca
Cl
Na
K
Mg
P
S
What are 3 trace minerals?
Iodine
Iron
Zinc
4 layer of digestive tract
Mucosa
Submucosa
Muscularis
Serosa
What is the mucosa?
What does it contain/what type of cells?
What is the function?
the mucosa, which contains epithelial and glandular cells, lines the inside of the gut
epithelial cells, which absorb digested nutrients, seal off the digestive contents from body fluids
What do glandular cells in the mucosa do?
glandular cells secrete enzymes, lubricating mucus that aids digestion, and substances that adjust the pH of the digestive contents
What is the submucosa?
What does it contain?
What type of tissue?
Function?
the submucosa is a thick layer of elastic connective tissue that contains neuron networks and blood and lymph vessels
neuron networks provide local control of digestive activity and carry signals between the gut and the central nervous system
What do lymph vessels do in relation to the digestive system?
lymph vessels carry absorbed lipids to other parts of the body
What is the muscularis?
What forms it?
What two layers?
Function?
in most regions of the gut, the muscularis is formed by two smooth muscle layers, a circular layer and a longitudinal layer
contraction of circular muscles and relaxation of the longitudinal muscles lengthens the gut, and vice versa
these muscles produce peristalsis – a wave of contractions that passes along the gut, constricting the gut and pushing the digestive contents onward
What action do smooth muscle of gut produce?
these muscles produce peristalsis – a wave of contractions that passes along the gut, constricting the gut and pushing the digestive contents onward
What is serosa?
Type of tissue?
the outermost gut layer, the serosa, consists of connective tissue that secretes a slippery fluid that lubricates the areas between the digestive organs and other organs
What is the serosa continuous with?
What does this tissue do?
along much of the length of the digestive system, the serosa is continuous with the mesentery, a tissue that suspends the digestive system from the inner wall of the abdominal cavity
What forms separations between major regions of the digestive tract?
powerful rings of smooth muscle called sphincters form valves between major regions of the digestive tract
What do sphincters do?
by contracting and relaxing, sphincters control the passage of digestive contents from one region to the next, and ultimately through the anus
What is sphincter between stomach and small intestine?
Pyloric sphincter
What is another name for chewing?
Mastication
What process do teeth assist in?
teeth cut, tear, and crush food items into small pieces during mastication (chewing)
What is food prepared into before swallowing?
the food mass forms a bolus, a ball of chewed or liquid food, in preparation for swallowing
What secretes saliva?
What is in saliva? (4)
salivary glands secrete saliva containing salivary amylase (which hydrolyzes starches), mucus, bicarbonate ions (HCO3–), and lysozyme (which kills bacteria)
When does the swallowing reflex start?
Swallowing reflex begins
when bolus reaches the pharynx.
the ____ ____ moves the bolus into the pharynx
the ____ prevents food from entering the trachea
____ in the esophagus moves the bolus downward and through the ____ ____
imperfect closure of the sphincter can result in acidic stomach contents reentering the esophagus, producing ____ ____(heartburn)
the swallowing reflex moves the bolus into the pharynx
the epiglottis prevents food from entering the trachea
peristalsis in the esophagus moves the bolus downward and through the gastroesophageal sphincter
imperfect closure of the sphincter can result in acidic stomach contents reentering the esophagus, producing acid reflux (heartburn)
9 phases of swallowing?
- The pharyngoesophageal
sphincter muscle is contracted, closing the esophagus, the epiglottis is up, and the glottis is open to let air enter the lungs. - Swallowing reflex begins
when bolus reaches the pharynx. - Elevation of soft palate
prevents food bolus from
entering nasal passages. - Pressure of tongue seals
back of mouth and prevents
bolus from backing up. - Larynx moves upward, pushing glottis against epiglottis to prevent bolus from entering airway.
- Pharyngoesophageal sphincter muscle relaxes, permitting bolus to enter the esophagus.
- Once food is in the
esophagus, the structures of the
mouth and pharynx reset to the
non-swallowing state. - Circular muscles of the
esophagus contract behind the
food, constricting the esophagus
and blocking upward movement. - Longitudinal muscles of the
esophagus contract, opening up
the esophagus. In concert with the
constricting circular muscles, this
pushes the bolus down the
esophagus. A series of alternating
contractions and relaxations of the
circular and longitudinal muscles
produces peristaltic waves that
move the bolus to the stomach.
What does the stomach do?
Stomach - stores food and adds digestive secretions
What is the mucosal layer of the stomach covered with?
the mucosal layer (epithelium) is covered with gastric pits containing gastric glands
What three things do stretch receptors in the stomach stimulate?
What cells produce these three things?
stretch receptors stimulate secretion of gastric juice containing pepsinogen (precursor of pepsin), hydrochloric acid (HCl), and lubricating mucus
chief cells in gastric pits secrete pepsinogen
parietal cells secrete H+ and Cl–
mucous cells secrete alkaline mucus that protects the stomach lining (epithelium)
What is stomach ulcer caused by, what does it cause, and what is treatment?
the bacterium Helicobacter pylori lives in the highly acid environment of the stomach
in some people, H. pylori breaks down the mucous barrier, exposing the stomach wall to attack by HCl and pepsin
the resulting peptic or stomach ulcer, causes stomach bleeding and pain
ulcers are treated with an antibiotic that kills H. pylori
What combine in the lumen of the stomach and what does this do functionally?
H+ and Cl– form HCl in the lumen of the stomach – lowering the pH to 2 or lower, which converts pepsinogen to pepsin
What does pepsin do?
pepsin begins protein digestion by breaking polypeptide chains
What is partially digested food in stomach called?
the partially digested mixture of food and gastric juices in the stomach is called chyme
What is between stomach and small intestine?
What moves chyme through this structure?
peristaltic contractions of the stomach wall move chyme through the pyloric sphincter into the small intestine
What is the main function of small intestine?
most absorption begins, and digestion is completed, in the small intestine
What lines the small intestine?
What is the purpose of these structures?
the lining folds into ridges covered by microscopic extensions (intestinal villi)
epithelial cells covering the villi have a brush border of fingerlike projections of plasma membrane (microvilli)
intestinal villi and microvilli increase the absorptive surface area of the small intestine to as much as 300 m2 – about the size of a doubles tennis court
secretions from the ____ (which are stored in the ____) and the ____ enter a common duct that empties into the lumen of the first segment of the small intestine (the ____)
secretions from the liver (stored in the gallbladder) and the pancreas enter a common duct that empties into the lumen of the first segment of the small intestine (the duodenum)
What does exocrine pancreas secrete?
exocrine cells in the pancreas secrete bicarbonate ions (H2CO3–) to neutralize acid in the chyme, and pancreatic enzymes (proteases, an amylase, nucleases, and lipases)
What are the active forms of the proteases secreted by pancreas?
proteases are secreted in inactive precursor forms – active forms are trypsin, chymotrypsin, and carboxypeptidase
What does the liver secrete?
the liver secretes bicarbonate ions and bile – a mixture of substances including bile salts, cholesterol, and bilirubin
What is the function of bile salts?
bile salts form a hydrophilic coating around fats which allows them to be to emulsified into tiny droplets
What does lipase do? Where is it secreted from?
lipase, a pancreatic enzyme, hydrolyzes the fats in micelles into monoglycerides and free fatty acids
What give bile its color? What does this come from?
bilirubin, the yellow pigment that gives bile its color, is a waste product derived from worn-out red blood cells
What happens in brush-border epithelial cells?
products of digestion in the lumen are transported across the plasma membranes of brush-border epithelial cells, which produce enzymes that complete digestion
Disaccharidases?
disaccharidases break maltose, lactose, and sucrose into individual monosaccharides
Aminopeptidases?
aminopeptidases hydrolyze small peptides to individual amino acids
Nucledotidases?
nucleotidases break nucleic acids into nucleosides
Nucleosidases?
nucleosidases convert nucleosides to nitrogenous bases, five-carbon sugars, and phosphates
What is between the small and large intestine?
The ileocecal valve-a sphincter between the small and large intestines controls the passage of materials into the large intestine
at the junction with the small intestine, part of the large intestine forms a blind pouch called the ____
cecum
What comes of the cecum?
appendix
What does the cecum merge with?
the cecum merges with the colon, which forms an inverted U
What are the final segments of the large intestine?
the final segment of the large intestine is the rectum, which terminates at the anal sphincter
What does the large intestine do?
the large intestine secretes mucus and bicarbonate ions and absorbs water and other ions, primarily sodium and chloride
What does the absorption of water in the large intestine do?
the absorption of water condenses and compacts the digestive contents into solid masses (feces)
What is else is contained in feces besides for waste?
What percent is this?
What do these do?
in vertebrates, 30-50% of the dry matter of feces consists of intestinal bacteria, which metabolize sugars and other nutrients and produce useful fatty acids and vitamins (such as vitamin K and the B vitamins folic acid and biotin)
What do intestinal bacteria do?
intestinal bacteria metabolize sugars and other nutrients remaining in the digestive residue, and produce useful fatty acids and vitamins
their activity also produces large quantities of gas (flatus) primarily CO2, methane, and hydrogen sulfide
What happens to gas produced by intestinal bacteria?
most of the gas is absorbed through the intestinal mucosa, and the rest is expelled through the anus in the process of flatulence
What happens when feces enter the rectum?
when feces enter the rectum, they stretch the rectal wall; the stretching triggers a defecation reflex that opens the anal sphincter and expels the feces through the anus
What does human digestion provide humans?
the human digestive system provides fuel molecules and a wide range of nutrients, including the molecular building blocks of carbohydrates, lipids, proteins, and nucleic acids
the digestive system also absorbs essential nutrients (amino acids, fatty acids, vitamins, and minerals) that cannot be synthesized within our bodies
What does an animals dentition reflect?
In what species is tooth specialization evident in?
an animal’s dentition reflects its diet, feeding method, habitat and life style
tooth specialization is especially evident among mammals, which have four types of teeth:
What are four types of teeth?
Function
incisors, at the front of the mouth, are chisel-shaped – used to nip or cut food
pointed canines at the sides of the incisors are specialized for biting and piercing
premolars and molars, at the sides of the mouth, crush and grind food
What the difference between carnivore and herbivore digestive tract?
vertebrates that feed primarily on nutrient-rich foods such as meat, blood, nectar, or insects (including carnivores) have a relatively short intestine
herbivores (e.g., rabbits) have a long intestinal tract and specializations of the esophagus, stomach, cecum, or other structures that store large volumes of plant material
What is microbiome?
microbiomes are the complete collections of microorganisms associated with a particular organism
What do microbiomes consist of?
microbiomes consist mostly of bacteria, but archaea, protists, yeasts and other fungi, and viruses may also be present
What does microbiome play an important role in?
microbiomes in digestive tracts — gut microbiomes — play important roles in digestion in many organisms
unlike vertebrates, many microorganisms can synthesize ____, the enzyme that hydrolyzes the cellulose of plant cell walls into glucose subunits
many ____ use microorganisms to aid digestion of plant material, housing them in specialized structures of the esophagus, stomach, or cecum
this is an example of ____; the herbivores benefit from the digestive abilities of the microorganisms, and the microorganisms benefit from an abundant supply of nutrients
cellulase
herbivores
mutualism
What are ruminants?
Examples?
ruminants such as cattle, deer, goats, sheep and antelopes have a complex, four-chambered stomach
Where do boluses of plant matter go in ruminants?
What is in here and what happens?
boluses of plant matter may go to the rumen or to the reticulum – both of which have symbiotic microorganisms that hydrolyze cellulose for fermentation reactions
fermentations generate nutrients (alcohols, amino acids, fatty acids) and methane gas, a byproduct
a ruminant “____ ____ ____” – it regurgitates material from the rumen and reticulum, rechews it, and swallows it again
chews its cud
Where does reswallowed cud by?
reswallowed cud bypasses the rumen and reticulum and goes to the omasum, where water is absorbed
What is the fourth part of a ruminant stomach and what happens here?
matter then moves to the abomasum (the gastric stomach), where acids and pepsin kill microorganisms and start the process of typical vertebrate digestion
the dead microorganisms are a rich source of proteins, vitamins, and other nutrients
