A + P Digestive System Flashcards
digestive system purpose
chemically break down large food molecules into smaller molecules that can be used by cells
the main macronutrients in food/drink
carbohydrates (polysaccharides)
proteins (amino acids)
fats (fatty acids and triglycerides)
what happens to each macronutrient
broken down with specific enzymes in specific locations during digestion
carbohydrate breakdown
- enzymes used (area)
- -products
- salivary amylase (mouth)
- -maltose
- pancreatic amylase (small intestine)
- -maltose
- maltase (small intestine)
- -glucose
- sucrase (small intestine)
- -fructose + glucose
- lactase (small intestine)
- -galactose + glucose
proteins
- enzymes used (area)
- -products
- pepsin (stomach)
- -peptides
- trypsin (small intestine)
- -amino acids and peptides
- chymotrypsin (small intestine)
- -AAs and peptides
fats
- enzymes used (area)
- -products
pancreatic lipase (small intestine) -fatty acids and glycerol
products resulting from the process of digestion
glucose
AAs
glycerol
fatty acids
glucose function
energy used to produce ATP via glycolysis and mitochondrial respiration
AA function
-excess use
used to construct proteins
excess
-can be used to synthesize pyruvate and acetyl CoA, which can be used for mitochondrial respiration
glycerol and fatty acids function
can be converted to pyruvate and acetyl CoA for mitochondrial respiration
digestion areas
mouth pharynx esophagus stomach small intestine large intestine (colon) pancreas liver
mouth
- chewing function
- salivary glands function
- tongue function
chewing
-breaks food into smaller particles so that chemical digestion can occur faster
salivary glands
-secrete mucous and enzymes that assist with digestion
tongue
-muscular and can move
-pushed food to back of mouth where it is swallowed
salivary glands
- salivary amylase function
- HCO3- function
- mucous function
salivary amylase
-breaks starch (polysaccharide) down to maltose (disaccharide)
HCO3- ions in saliva
-act as buffer
-maintain a pH between 6.5-7.5
mucous
-lubricates and helps hold chewed food together in a clump called a bolus
pharynx
- what meet there
- where do they separate
- how is swallowing accomplished
respiratory and digestive passages meet in the pharynx
separate posterior to the pharynx to form the esophagus (leads to the stomach) and trachea (leads to the lungs)
swallowing is accomplished by reflexes that close the opening to the trachea (via the epiglottis)
esophagus
-peristalsis
rhythmic contractions that move food from the mouth down to the stomach (and within the GI tract)
peristalsis
- function
- when lying down, inverted, or in reduced gravity
important mechanism because it ensures that you can eat and drink regardless of your body position or environment
when lying down, inverted, or in reduced gravity, the contractions associated with peristalsis are stronger and more rhythmic to push the bolus down to the stomach
stomach parts
upper sphincter
lower sphincter
gastric glands
muscular walls
upper sphincter
- function
- also called
lets food in
called the lower esophageal or cardiac sphincter
lower sphincter
- function
- also called
lets food out
called the pyloric sphincter
gastric glands
-produce
produce secretions called gastric juice
gastric juice composition
pepsiongen and HCl
pepsinogen
- converted to
- production stimulated by
converted to pepsin, which digests specific proteins
production is stimulated by the presence of gastrin in the blood
HCL
- functions
- maintains
functions -converts pepsinogen to pepsin -dissolves food -kills microorganisms maintains a pH in the stomach of approximately 2.0
seeing, smelling, tasting, or thinking about food result
can result in the secretion of gastric juice (via the release of gastrin in the blood)
muscular walls function
contract vigorously to mix food with gastric juice, producing a mixture called chyme
small intestine
-approx. length
6 meters
chyme
- how does it enter the SI
- function
enters through the pyloric sphincter in tiny spurts
presence of chyme stimulates mucous production within the SI to further reduce the acidity of the chyme
SI three main sections
duodenum
jejunum
ileum
duodenum
- location
- length
- function
first section
approx. 10-12 in. long
largely responsible for final food breakdown within the SI
jejunum
- location
- length
- function
middle section
approx 2-4 meters
absorbs most glucose, fructose, AAS, small peptides, and vitamins
ileum
- length
- function
approx. 2-4 m long
absorbs Vitamin B12, bile salts, and leftovers from jejunum
SI contains numerous ridges and furrows and projections called…
villi
villi
- function
- individual villus cells have…
- function
increase the surface area for absorption of nutrients
individual villus cells have microvilli
-further increase absorptive surface area
total absorptive area
equivalent to 500-600 m2
each villus contains
blood vessels and lacteal (lymph vessel)
digestion enzymes location
embedded within the plasma membrane of the microvilli
digestion of nutrients in SI
- up to this point
- CHOs
- fats
- proteins
up to this point, proteins and CHO are only partially digested and lipid digestion has not begun - 90% of food digestion will occur here
CHOs
- enzymes
- function
pancreatic amylase, maltase, sucrase, and lactase
collectively break down starches into glucose and other monosaccharides
fats
- enzyme
- function
pancreatic lipase
digests small-chain triglycerides and fatty acids into glycerol and free fatty acids
proteins
- enzyme
- function
trypsin
digests peptides from stomach into smaller peptide chains and AAs
absorption of nutrients in the SI
-active transport function
moves glucose and AAs into the intestinal walls, where they are picked up by blood capillaries
medium-chain triglycerides absorption
absorbed and sent to liver
large chain triglycerides absorption
form chylomicrons and are sent to the lymphatic system
fat-soluble vitamins absorption
90% are absorbed with lipids in SI, then transported to liver or adipose tissue
water-soluble vitamins absorption
absorbed via simple diffusion and sent to kidneys
excess water-soluble vitamins are excreted
mineral absorption in SI
depends largely on bioavailability, pH, availability of substances for co-transport, etc.
water absorption from food/drink
- primary location
- location of the rest
primarily in SI
rest is in LI
hypotonic solutions facilitate…
water absorption by the SI
hypertonic solutions (salt tablets, high sugar drinks) function
pull water into the SI, which may create GI distress
large intestine length
approx. 1.5 m long
ileocecal valve function
regulates what comes into LI from SI
first portion of LI
- what is it?
- function
small pouch called the cecum
absorbs fluids and salts that remain after SI digestion/absorption and to mix undigested remains with mucus
appendix
- connected to
- function
connected to the cecum function still not well known -current theory is that is has an immune system role by harboring and protecting bacteria which are important for LI function
last portion of LI
- terminates in
- function
rectum
terminates in the anus
function
-regulates excretion of undigested/unabsorbed waste material from the LI
how much digestion occurs in LI
5%
LI primary functions
absorb water from remaining undigested materials
excrete the final waste materials
LI and water -receives how much every day? --water is from where? -how much is reabsorbed what is absorbed with water by the LI? -purpose of HCO3- -what vitamin does it absorb
10L/day
-1.5L from food
-8.5 from secretions into the gut
95% is resorbed
Na+ and Cl- are also absorbed
HCO3- is excreted into the LI to reduce the acidity of the waste materials
absorbs vitamin K produced by colon bacteria
diarrhea
- cause
- result
water is not absorbed well
can cause dehydration and electrolyte loss
feces
-composition
75% water, 25% solids
- 1/3 of solids is intestinal bacteria
- 2/3 is undigested materials
pancreas function
acts as an exocrine gland to produce pancreatic juice
acts as an endocrine gland to produce insulin
where does pancreatic juice empty into
the SI via a shared duct adjoined with the duodenum
pancreatic juice composition
sodium bicarbonate (NaHCO3)
pancreatic amylase
trypsin and chymotrypsin
pancreatic lipase
sodium bicarbonate (NaHCO3) function
neutralizes the acidic material from the stomach
pancreatic amylase function
digests starch to maltose
trypsin and chymotrypsin function
digest proteins to peptides
-like pepsin, these are specific for certain AAS, but not all of them
pancreatic lipase
digest fats to glycerol and fatty acids
liver
-produces
bile
bile
- stored
- sent to
- common bile duct
stored in the gallbladder sent to the duodenum through the common bile duct emulsifies fats (separates them into small droplets so that they can mix with water and be easily acted upon by enzymes
liver function
filters blood received from intestines (via hepatic portan vein) -drugs, alcohol, poisonous substances acts as a glucose regulator produces blood proteins destroys old red blood cells converts ammonia (produced by the digestion of proteins)to urea, a less toxic compound stores macrophages -used to combat infection
liver as a glucose regulator
creates glucose (from AAs) and/or coverts glucose to glycogen for storage breaks down glycogen to release glucose into the blood circulation as needed this storage-release process maintains a constant glucose concentration in the blood (0.1%) if glycogen and glucose run short, AAs can be converted to glucose in the liver
what happens to destroyed old RBCs
converts Hb from these cells into iron, biliverdin, and bilirubin
digestion hormones
gastrin enterocrinin secretin cholecystokinin (CCK) gastric inhibitory peptide (GIP) vasoactive intestinal peptide (VIP)
gastrin
- food in the stomach….
- medulla
- gastrin
presence of food in the stomach stimulates stretch receptors, which relay this information to the medulla oblongata
medulla stimulates endocrine cells in the stomach to secrete gastrin into the circulatory system
gastrin then stimulates the stomach to secrete gastric juice
enterocrinin
chyme from the stomach stimulates the cells in the duodenum to release enterocrinin
enterocrinin stimulates the mucous glands to produce mucous, which helps reduce the acidity of the chyme
secretin
chyme from stomach stimulates the cells in the duodenum to release secretin
secretin stimulates the pancreas to produce NaHCO3, which neutralizes the acidic chyme
secretin also stimulates the liver and gallbladder to secrete bile
cholecystokinin (CCK)
the presence of food in the duodenum stimulates duodenal cells to secrete CCK
CCK stimulates the liver and gallbladder to release bile
CCK also stimulates the pancreas to produce pancreatic enzymes for pancreatic juice
Gastric Inhibitory Peptide (GIP)
the presence of food in the duodenum stimulates certain endocrine cells to produce GIP
it has the opposite effects of gastrin
-inhibits gastric glands in the stomach and inhibits the mixing and churning movement of stomach muscles
this slows the rate of stomach emptying when the duodenum contains food
Vasoactive Intestinal Peptide (VIP)
the presence of food in the duodenum stimulates certain endocrine cells to produce VIP
it has many functions, but the most important for digestion is that is dilates capillaries in active areas of the intestinal tract to facilitate absorption of nutrients
peptic ulcer
an irritation due to gastric juice penetrating the mucous lining of the stomach or duodenum
ulcers are thought to be caused by certain bacteria, which can thrive in the acid environment of the stomach
the presence of the bacteria on portions of the stomach lining prevents it from secreting mucous, making it susceptible to the digestive action of pepsin
polyps
small growths often found in the epithelial lining of the LI
can be benign or cancerous and can be removed individually
a low-fat, high-fiber diet promotes regularity and is recommended as a protection against LI cancer
appendicitis
an infection of the appendix
the appendix may swell and burst, leading to peritonitis (infection of the abdominal lining)
cirrhosis
scarring of the liver, which results in poor liver function
it is the final phase of chronic liver disease and damage, commonly caused by Hepatitis C and long-term alcohol abuse
gall stones and pancreatitis
bile salts clump up into a ball
high-fat meal can cause them to come out of the gallbladder and travel to the pancreatic duct
predisposition for gall stones
high-fat diets
high-sodium diets
alcoholic
