ch 11.8- digestive system Flashcards
● Both enzymatic
digestion and
absorption
occur
● Absorbs many
nutrients
(carbs,
proteins, fats,
minerals,
vitamins, water,
& salts
small intestine
● Absorption
occurs,
enzymatic
digestion does
not
● Absorption of
vitamins, water,
& salts
● Bacteria
produce
vitamins
Large intestine
salivary amylase
saliva breaks down starch into maltose (glucose +
glucose). Saliva also lubricates the food, creating a
bolus.
common to digsetive and respiratory systems
pharynx
separates to form trachea and esophogus - epiglottis blocks trachea
food enters stomach via
cardiac sphincter
what happens in the stomach
mechanical and chemical breakdown of protein and fat occur
stomach gastric glands
mucous cells - produce mucous
parietal cells
chief cells
G cells
G cells
Food entry causes the stomach to distend, signaling G
cells to release gastrin, a hormone with two
functions:
functions of gastin
- Stimulates parietal cells to release very acidic
gastric juice (high [HCl]). - Stimulates chief cells to secrete gastric lipase
and pepsinogen. Gastric lipase breaks down
fats into fatty acids and glycerol. Pepsinogen is a
zymogen (inactive enzyme precursor) which
activates into pepsin in acid. Pepsin cleaves
peptide bonds (proteins → amino acids).
chyme enters the small intestine via
the pyloric sphincter
small intestine
Responsible for 90% of total digestive absorption.
Consists of three parts: duodenum (digestion),
jejunum, and ileum (absorption).
DJ Eye (i)
goblet cells
secrete mucus to protect the epithelial
lining from acidic chyme. Chyme triggers the release of secretin (a hormone), which stimulates the pancreas to release basic bicarbonate ions (HCO3-) into the duodenum via the pancreatic duct.
cholecystokinin
CKK
in response to detecting proteins and fats entering
the small intestine, which slows gastric emptying,
stimulates the pancreas to release digestive
enzymes, and tells the gallbladder to release bile
into the duodenum.
pancreas
secretes HCO3 - (neutralization),
pancreatic amylase (starch → maltose) and proteases (proteins → amino acids). Trypsin and chymotrypsin are pancreatic proteases, which are initially released as zymogens (trypsinogen and chymotrypsinogen).
enteropeptidase
Enteropeptidase in the
duodenum converts trypsinogen to trypsin, which
then converts chymotrypsinogen to chymotrypsin.
bile
(emulsifies fats) is produced by the liver and
stored and concentrated by the gallbladder. Bile is
important for the absorption of lipids (fats) from our
diets.
ileocecal sphincter
connects the small intestine (ileum) to the large
intestine (colon).
vili
(finger-like projections which increase surface
area) are made of enterocytes that are lined with
microvilli. Villi and microvilli increase surface area
and absorption efficiency. Crypts (invaginations in
the intestinal wall) contain cells that secrete enzymes
and produce new epithelial cells for the lining.
Inside the villus, nutrients (glucose and amino acids)
are absorbed into blood capillaries and fats (fatty
acids and glycerol) into lacteals.
liver functions
bile production
PUSH DoG
Protein synthesis, Urea synthesis, Storage, Hormone
synthesis, Detoxification, Glucose and fat metabolism
1. Blood maintenance
● Filters and detoxifies blood coming from the
digestive system.
● Detoxifies the body by metabolizing chemicals
and drugs, removing the by-products as waste
via bile → intestines, and kidneys → urine.
● Destroys erythrocytes and bacteria. Kupffer
cells (phagocytes) eat bacteria and get rid of
old RBCs, breaking down their hemoglobin to
bilirubin (yellow) for secretion in the bile.
2. Glucose metabolism
● Glycogenesis: Converts excess glucose into
glycogen for storage in the liver (after meals).
● Glycogenolysis: Breaks down glycogen to
glucose for bodily use (between meals).
● Gluconeogenesis: Converts glycerol and
amino acids into glucose when glycogen stores
are depleted.
3. Protein metabolism
● Synthesizes plasma proteins from amino
acids (albumin and blood clotting factors).
● Converts ammonia (dangerous byproduct of
protein metabolism) into urea (safer) for
excretion.
cecum
Water and mineral absorption occur at the cecum
(small pouch). in the large intestine
appendix
The appendix (projection in the
cecum) is a vestigial structure with negligible
immune function.
colon
water absorption is
completed, hardening feces. The feces is stored in
the rectum and expelled through the anus.
bact in large intestine
Many
species of bacteria coexist in the large intestine;
these bacteria serve a critical function in aiding
digestion. Over 99% of bacteria in the large intestine
are obligate anaerobes. These bacteria, as well as all
the other bacteria that are present in or on the body,
are collectively known as a microbiome.
large intestine functions
- Water absorption.
- Mineral absorption (salts).
- Vitamin production and absorption: In a
mutualistic relationship, bacteria produce and
absorb vitamins, metabolize bile acid, and ferment
fiber.
bile acid metabolism
Bile acid metabolism is a key indicator of the health of
the microbiome. A healthy microbiome will have
sufficient levels of all the bacteria needed for bile acid
metabolism, while an unhealthy microbiome will not,
impairing function.
small intestine enzymes
Peptidase- Breakdown of peptides
into amino acids
Maltase, sucrase,
lactase- Breakdown of
disaccharides into
monosaccharides
Enteropeptidase- Activates trypsinogen to
trypsin
pancreatic enzymes
Trypsin, chymotrypsin,, carboxypeptidase- Protein breakdown
Pancreatic amylase- Starch breakdown
Nucleases- DNA and RNA
breakdown