Digestive system Flashcards
what is digestion
process of mechanical and chemical breakdown of food into molecular subunits small enough to be absorbed into body fluids and cells (nutrients)
what is chemical and mechanical breakdown of food
-mechanical: chewing
-chemical: enzymes and acids being mixed with food
nutrients
substances essential for growth and maintaining life
what are the main functions of the digestive system
-breakdown food into smaller molecules that can cross plasma membranes
-food storage
-absorption of nutrients
-elimination of undigested food (feces)
macro-nutrients
requires in large amounts (carbohydrates, fat, protein, macro elements)
micro-nutrients
required in small amounts (vitamins, trace elements)
essential nutrients
animals cannot synthesize themselves and must be acquired from food (essential amino acids, essential fatty acids, vitamins, minerals)
essential amino acids in humans
-9 (number varies depending on species)
-lysine, histidine, tryptophan, phenylamine, threonine, valine, methionine, leucine, isoleucine
essential fatty acids in humans
-2
-linoleic acid (omega-6)
-linolenic acid (omega-3)
how many essential vitamins in humans
-13
-humans can synthesize vitiman D from sunlight
what are the fat soluble essential vitamans in humans
-A (retional)
-D (dalciferol)
-E (tocopherol)
-K (napthoquinone)
what are the water soluble essential vitamans in humans
-B1 (thiamine)
-B2 (riboflavin)
-niacin
-B6 (pyridoxine)
-pantothenic acid
-folic acid
-B12 (cobalamin)
-biotin
-C (ascorbic acid)
what are the macronutrients for humans
-calcium
-chlorine
-chromium
-cobalt
-fluorine
-iodine
-iron
-magnesium
-manganese
-mollybdenum
-nitrogen
what are the essential micronutrients for humans
copper
some monosaccharides
-glucose, fructose, galactose
-a few of which are normally found in most diets
-absorbable units
some disaccharides
-sucrose (glucose and one fructose)
-trehalose (two glucose molecs in opposite orentations)
-maltose (two glucose molecs in the some orientation)
-lactose (milk sugar; glucose and one galactose)
some polysaccharides
-chains of interconnected monosaccharides
-most common carbohydrate of animal diets
-starch from plants and glycogen form animals
-both have alpha bonds between the glucose units
cellulose
-beta bonds
-most abundant organic molec in the biosphere
-major component of plant material, comprising over half of the plant cell wall
-to be usable must be hydrolyzed into monosaccarides
-we cant break this down because our enzyme cant break down beta bonds
how is glycogen made up
-formed form glucose units joined in chains by alpha(1-4) linkages
-side branches are linked to the chains by alpha (1-6) linkages
how is cellulose made up
-formed form glucose units joined ends by beta (1-4) linkags
-hundreds to thousands of cellulose chains line up side by side in an arrangement reinforced by hydrogen bonds between the chains, to form cellulose microfibrils in plant cells
what are proteins
consists of various combinations of amino acids (absorbable units) held together by peptide bonds
what are most dietary lipids
bulk of dietary lipid is triglyceride, but also contains phospholipids, cholesterol, fat soluble vitimans
what are triglycerides
glycerol+fatty acids (which is the absorbable units)
how do fats pass through the the gut
after being broken down they pass through simple diffusion
how are nucleotides broken down
-nucleic acid
-nucleotides
-nucleosides
-ribose and nitrogenous base (which are the absorbable units)
what is a calorie
a unit of energy difined as the amount of energy needed to raise the temp of one gram of water by one degree Celsius at a pressure of 1 ATM
how many cals are in a gram of fat, protein, carbohydrates
carb/pro=4cal/gram
fats=9cal/gram
what is a unit of energy in international system of units
the joule
one cal=4.2 joules
how does are bonds broken during chemical break down in the digestive system
-bonds are broken by hydrolytic hydrolysis
-addition of H+ and OH- form water
what enzymes is the chemical break down in the digestive system driven by
amylase-starch
lipase-fats and other lipids
protase-proteins
-nucleases-nucleic acids
what kind of vitamins (fat or water soluble) can our body not store thus needs daily supply
-water
-fat soluble can be stored by the body water cannot it gets urinated out
what are the two ways digestion can occur
-intracellularly
-extracellularly
intracellular digestion
cells take in food particles by endocytosis
extracellular digestion
takes place in a tube enclosed in body but outside body cells (the digestive tract)
how does intracellular digestion happen in a sponge
-H2O carrying food particles
-food enters cell phagocytosis
-goes in food vacuoles
-lysosomes with digestive enzymes merge with food vacuoles
-waste products are expelled by exocytosis
where does extracellular digestion occur
in compartments that are continuous with the outside of the animals body
what is the gastrovascular cavity
a structure found in primitive animal phyla that functions in both digestion and distribution of nutrients
what is the evolutionary significance of the extracellular digestive system
-better food storage
-dont need to eat all the time
-you can ingest a lot more food so allows animals to increase body size, ingest more food=grow larger
-expands the food range (what they can eat)
what are the different classifications for ways animals can acquire nutrients
-fluid feeders
-suspension feeders
-deposit feeders
-bulk feeders
fluid feeders
ingest liquids containing organic molecules (e.g. tapeworms, mosquitos, insects, birds, bats)
suspension feeders
eat small particles of organic matter of small organisms in fluids (e.g. mussels, whales)
deposit feeders
ingest small organic particles form solid matter that feeders live on (e.g. earthworm, fiddler crab, polychaete worms)
bulk feeders
consume large pieces of organisms, or entire large organisms (e.g. most animals)(mostly carnavores)
tapeworm digesive tract
-they have none
-there fore they must eat food already digested by another animal
-they are fluid feeders
-they are parasites inside animals intestines, absorb nutrients directly by diffusion across their skin (cuticle)
what is the digestive system like of a earth work (deposit feeder)
-it is divided into many regions each with a certain function
-digestive system consists of mouth, esophagus, crop, intestine, gizzard
-gizzard uses stones the worm eats to grind the food
what is the digestive system of a grasshopper like
-foregut=mouth, salivary glands, esophagus, crop, gizzard
-midgut=chemical digestion takes place in the stomach and 6 pairs of gastric ceca extending from stomach, digestion aided by bacteria
-hindgut=coiled structure consisting of anterior ileum, middle colon, posterior rectum, anus
what are the parts that make up the digestive system of birds
-the canal includes the oral cavity, esophagus (which includes crop in some birds), stomach (proventeuculus, glandular portion of stomach), gizzard, small intestine, large intestine
-also has accessory structures including the beak, salivary glands, liver, pancreas
carnivore
digest animal products
herbivore
digest plant products
omnivore
digest both plant and animal products
what is the digestive tract of a carnivore like
-have a greatly enlarged stomach, which secretes powerful digestive enzymes, along with 10 times more HCL then herbivores
what is the digestive tract of the herbivore like
they have a long digestive tract because it take a long time to absorb nutrients form the plant material which they eat. they also have large caecu which helps along with enzyme, breakdown the plant material and cellulose
how can mammal be classified by the type of stomach
-monogastrics
-ruminants
monogastrics
they have a simple single chambered stomach such as humans, swine, rabbits, and horses
ruminants
have a four chambered complex stomach
what is the stomach of monogastrics like
-muscular digestive organ
-glands in the stomach wall secrete gastric juices
-gastric juices have about 0.2 to 0.5 precent HCL
-stomach muscle mix and sqeeze the food, and forces the chyme to go into the small intestine
-occupies 3/4 of abdominal cavity mostly on left side
what is a rumen stomach like
-4 chambers
-ferments food prior to digestion through microbial actions
-microbes digest cellulose
-uses lots of water
what are the five stages of digestion in animals with a GI tract
-mechanical processing
-secretion of enzymes and other digestive aids
-enzymatic hydrolysis
-absorption
-elimination
what are the main organs in the human GI tract (alimentary canal)
-tube form mouth to anus
-mouth
-pharynx
-esophagus
-stomach
-small intestine
-large intestine
what are the accessory digestive organs in the human GI tract to
-teeth
-tongue
-salivary glands
-liver
-gullbladder
-pancrease
what do the accessory organs help with in the human digestive tract
mechanical and digestive organs
what are the 4 layers of the GI tract
-mucosa
-submucosa
-muscularis
-serosa
mucosa
-the intermost layer of the GI wall that is surrounding the lumen
-responsible for protection, secretion, and absorbtion
-consists of epithelium, lamina propria (connective tissue), and muscularis mucosae (thin layer if smooth muscle)
submucosa
-areolar connective tissue
-binds mucosa to muscularis
-acts and glue
submucosa plexus
network of neurons and ganglia
muscularis
skeletal muscle (volentary swallowing and volentary control of defication) and smooth muscle (breaks down food and mixes it with digestive sectretions)
myenteric plexus
part of the enteric nervous system that regulates peristalsis
serosa
serous membrane of areolar connective tissue and simple squamous epithelium
enteric nervous system
-submucosal plexus + myenteric plexus
-which more or less works as an anomic nervous system
-with out inputs of the CNS
what are the 3 muscle layers of the musculais layer
-longitudinal muscle
-circular muscle
-oblique muscle
mouth
where food is taken in an where digestion begins
oral cavity
chamber contains teeth and tongue, and receives secretions from the salivary glands
digestion
mechanical and chemical begins in the mouth
what happen when food enters the mouth
-salivary glands secrete saliva
-salivary amylase digests starch
-saliva (mucus) acts as a softener/lube
-facilitates swallowing of food
-salivary lipases aids in triglyceride digestion
where is the parotid salivary gland found
infront of the ear
where is the salivary duct found
opens into the cheek form the parotid salivary gland
what does the tongue do
moves food during chewing and swallowing
where is the sublingual salivary found
under the tongue
where is the submandibular salivary gland found
lies deep in the mouth
what happen when bolus is swallowed
goes through the pharynx and esophogus to stomach
-epiglottis blocks trachea
why is swallowing important
it plays a major role in preventing the entrance of food into the respiratory tract
is swallowing voluntary or involuntary
it involves both voluntary (oral) snd involuntary (pharyngeal and esophageal) phases
explain how the esophagus changes through out swallowing (before swallowing)
-before swallowing the pheryngoesophageal sphincter muscle is contracted, closing esophogus, the epiglottis is up and the glottis is open to let air in lungs
explain how the esophagus changes through out swallowing (during swallowing)
-relflex begings when bolus reaches the pharynx
-elevation of soft palate prevents food bolus form entering nasal pasage
-pressure of tongue seals back of mouth and prevent bolus from backing up
-larynx moves up, pushign glottis to prevent bolus form entering airway
-pharyngoesphageal sphincter muscle relaxes, permitting bolus to enter esophagus
-once food is in the esophogus structures of mouth and pharynx reset to non swallow state
explain how the esophagus changes through out swallowing (during peristalsis)
-circulatory muscle of the espohogus contract behind the food blocking upward movement
-longitudinal muscle of the esophagus contract, opening up the esophagus
-in concert with the constricting circular muscles this pushes the bolus down the esophogus
-series of alter contracts and relaxations of circ and longitudal muscles produces peristaltic waves that move bolus to stomach
what is paristalsis
involentary contractions and relaxations of the GI tract
how are peristalsis waves produced
coordinated contractions of circular and longitudal muscles produce peristaltic waves that move digestive contents from mouth to anus
what are the functions of the stomach
-food is mixed with stomach acid and enzymes to break down the food into smaller prices
-reservoir of food before released to small intestine
what is chyme
the combination of food and stomach juices
what is the function of HCl
it doesnt digest food but it does break down the connective tissue of meat and activates pepsin
what is the mucus of the stomach for
its several mm thisch and it protects the cell wall from the effects if HCl
what are the different cells found in the gastric pits of the stomach
-surface epithelial cells
-mucous cells (secretes mucus)
-parental cell (secretes H+ and Cl-)
-chief cells (secretes pepsinogen)
what happens to the gastric walls when food enters the stomach
they stretch which releases HCl
what happens when pepsinogen and HCl are secreted into gastric lumen
-HCl cleaves pepsinogen to produce pepsin
-pepsin catalyzes conversion of more pepsinogen to pepsin leading to high amounts of pepsin
-digestion of proteins
what are the measurements of the small intestine
-small diameter (2.5cm)
-6 m long
what is the pH of the small intesine like
it is slightly basic
what is the duodenum, jejunum and iieum length
-dou (first 25m)
-jej (2.2-2.4m)
-iileum (3.3-3.6m)
what connects the large intestine to small intestine
Ileocecal sphincter
what is the SA of the small intestine
approximately the size of a tennis court
what does the inside of the small intestine have to inc SA
-projections called villi (sing villus)
-the outer layer of each villus has thousands of microvilli
what does the villi contain
blood and lymphatic capillaries
intentional juices
-1-2 L per day
-water and mucus
-slightly alkaline (HCO3-)
-brush-border (microvilli) enzymes
what kind of enzymes does the intestinal juice of the intestine have
-carbohydrate digesting
-protein digesting
what happens in the douodenum
digestive juices form the pancreas and liver add enzymes and digestive aids to food mass
what are pancreatic juices
-digestive enzymes (e.g. amylase, protases, lipases
-HCO3- ions (neutralizes)
how does the liver aid in digestion and what does it secrete
-secrets bile which emulsifies fats
-bile salts
-cholesterol
-bilirubin
-additional bicarbonate ions
what stores bile
gullbladder
what do the exocrine cells from the pancrease secrete
pancreatic enzymes
what do the endocrine cells form the pancreas secrete
insulin and glucogon into blood stream
what is the carbohydrate digestion system
-mouth=polysaccharides>smaller polysaccharides, disaccharides (salivary amylase)
-lumen of small intestine=polysaccharides> disaccharides (pancreatic amylase)
-eipthelial cells (brush border) of small intestine=disaccharides(malt, suc, lac) > monosaccharides (glucose) (disaccharidases)
what is the protein digestion process
-stomach=proteins> peptides (pepsin)
-lumen of sml intest=proteins> peptides (trypsin, chymotrypsin) and large peptides> AAs (carboxypeptidase)
-eipthelial cells (brush border) of small intestine=large peptides> AAs (amino peptidase)
-dipeptides>AAs (dipeptidase)
what is the digestive process of fats
lumen of small intestine=triglycerides and other lipids>fatty acids, monoglycerides (lipase)
what is the digestive process of nucleic acids
-lumen of sml int=DNA, RNA>nucleotides (pancreatic nucleuses)
-nucleotides> nitrogen bases, 5C sugars, phosphotates (nucleotidase, nucleosidase, phosphates)
how are water soluble nutrients absorbed in GI
water soluble molecules are broken into absorbable subunits at brush borders of mucosal cells and transported inside; the subunits are transported on the other side to the extracellular fluids and blood
what are the water soluble nutrients
-proteins, sugars, nucleotides
what are fat soluble nutrients
-products of lipid breakdown (FA, monoglycerides)
-fat soluble vitimans and cholesterol
how do fat soluble nutrients get absorbed
-when a micelle contacts the plasma membrane of a mucosal cell, the hydrophobic molecs within the droplet fuse and penetrate the membrane and enter the cytoplasm
what is a micelle
fats coated with bile salts
what are chylomicrons
-in mucosal cells fatty acids and momnoglycerides are re-combined into triglycerides and packages into chylomicrons
-small droplets covered by a protein coat
-hydrophilic surface that keeps the droplets suspended in the cytosol
what happens to cholesterol and chylomicrons
-cholesterol absorbed in the small intestine is also packed into chylomicrons
-after travelling across the mucosal cells the chylomicrons are secreted into the interstitial fluids of the submucosa
taken up by the lymph vassels and transferred into blood stream
what are many nutrients absorbed by the small intestine absorbed by
the liver
how are nutrients from the small intestine absorbed into the liver
-capillaries absorbing nutrient molecules in the small intestine collect into veins that join to form the hepatic portal vein
-a larger blood vessel that leads to capillary networks in the liver small droplets covered by a protein coat
-in the liver some nutrients leave the blood stream and enter the liver cells for chemical processing
what makes up the large intestine
-cecum, appendix, colon, rectum
what does the large intestine do
-secretes mucus and HCO3- ions
-absorbs water (1.3-1.5L/day) and other ions (mainly Na+ and Cl-)
what happens with matter at the end of the large intestine
undigested remnants are expelled form the anus
how many bacteria species live in the intestine
and many as 500. makes up to 30-50% of the dry matter of feces
what is most common bacteria found in the human (and most mammals) digestive tract
-escherichia coli
-metabolizes sugars and other nutrients remaining in the digestive residue
what do microbe in the intestine do
-produce useful fatty acids and vitamins such as: vit K, B group of vitimans (folic acid and biotin) some of which are absorbed in the large intestine
-produces a large quantity of gases: CO2, methane, and hydrogen sulfide
