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Anatomy > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What are the 5 stages of digestion?

A

– Ingestion: selective intake of food
– Digestion: mechanical and chemical breakdown of food
into a form usable by the body
– Absorption: uptake of nutrient molecules into the
epithelial cells of the digestive tract and then into the blood
and lymph
– Compaction: absorbing water and consolidating the
indigestible residue into feces
– Defecation: elimination of feces

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2
Q

What is mechanical digestion and what are some examples?

A

—the physical breakdown of
food into smaller particles
– Cutting and grinding action of the teeth
– Churning action of stomach and small intestines
– Exposes more food surface to digestive enzymes

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3
Q

What is chemical digestion and what are some examples?

A

—a series of hydrolysis reactions
that breaks dietary macromolecules into their
monomers (residues)
– Carried out by digestive enzymes produced by salivary
glands, stomach, pancreas, and small intestine
– Results
* Polysaccharides into monosaccharides
* Proteins into amino acids
* Fats into monoglycerides and fatty acids
* Nucleic acids into nucleotides

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4
Q

What nutrients are present in a usable form?

A

– Vitamins, amino acids, minerals, cholesterol, and water

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5
Q

What organs make up the digestive tract? GI tract?

A

– Mouth, pharynx,
esophagus, stomach, small
intestine, and large intestine
– Gastrointestinal (GI) tract
is the stomach and
intestines

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6
Q

What are the accessory organs?

A

– Teeth, tongue, salivary
glands, liver, gallbladder,
and pancreas

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7
Q

What is the enteric nervous system?

A

—nervous network in
esophagus, stomach, and intestines that regulates
digestive tract motility, secretion, and blood flow

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8
Q

What is the mesentary?

A

—connective tissue sheets that
suspend stomach and intestines from abdominal wall

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9
Q

What is the parietal peritoneum?

A

—a serous membrane that
lines the wall of the abdominal cavity

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10
Q

What is the dorsal mesentary?

A

a translucent two-layered
membrane extending to the digestive tract

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11
Q

What are the lesser and greater omentum?

A
  • Lesser omentum—a ventral mesentery that
    extends from the lesser curvature of the stomach
    to the liver
  • Greater omentum—hangs from the greater
    curvature of the stomach (its left inferior margin)
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12
Q

What is the mesocolon?

A

—extension of the mesentery that anchors
the colon to the abdominal wall

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13
Q

What is intraperitoneal? Retro?

A
  • Intraperitoneal—when an organ is enclosed by
    mesentery on both sides
    – Considered within the peritoneal cavity
    – Stomach, liver, and parts of small and large intestine
  • Retroperitoneal—when an organ lies against the
    posterior body wall and is covered by peritoneum on its
    anterior side only
    – Considered to be outside the peritoneal cavity
    – Duodenum, pancreas, and parts of the large intestine
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14
Q

What are the functions of the mouth?

A

– Ingestion (food intake)
– Taste and other sensory responses to food
– Chewing and chemical digestion
– Swallowing, speech, and respiration

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15
Q

What are the different types of teeth

A

8 incisors, 4 canines, 8 premolars, 12 molars

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16
Q

What is the function of saliva?

A

– Moistens mouth
– Begins starch and fat digestion
– Cleanses teeth
– Inhibits bacterial growth
– Dissolves molecules so they can stimulate the taste
buds
– Moistens food and binds it together into bolus to aid in
swallowing

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17
Q

What are the solutes in saliva?

A

– Salivary amylase: enzyme that begins starch digestion in
the mouth
– Lingual lipase: enzyme that is activated by stomach acid
and digests fat after food is swallowed
– Mucus: binds and lubricates a mass of food and aids in
swallowing
– Lysozyme: enzyme that kills bacteria
– Immunoglobulin A (IgA): an antibody that inhibits
bacterial growth
– Electrolytes: Na+, K+, Cl−, phosphate, and bicarbonate

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18
Q

What are the intrinsic salivary glands?

A

– Lingual glands: in the tongue; produce lingual lipase
– Labial glands: inside of the lips
– Palatine glands: roof of mouth
– Buccal glands: inside of the cheek

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19
Q

What are the extrinsic salivary glands?

A

– Parotid: located beneath the skin anterior to the earlobe
* Mumps is an inflammation and swelling of the parotid
gland caused by a virus
– Submandibular gland: located halfway along the body
of the mandible
* Its duct empties at the side of the lingual frenulum, near
the lower central incisors
– Sublingual gland: located in the floor of the mouth

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20
Q

What is a bolus?

A

—mass swallowed as a result of saliva
binding food particles into a soft, slippery, easily
swallowed mass

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21
Q

What are the pharyngeal constrictors?

A

– Has superficial layer of circular skeletal muscles that form
pharyngeal constrictors (superior, middle, and inferior)
that force food downward during swallowing
* When not swallowing, the inferior constrictor (upper
esophageal shincter) remains contracted to exclude air from the
esophagus
* Disappears at the time of death when the muscles relax, so it is a
physiological sphincter, not an anatomical structure

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22
Q

What are the features of the esophagus?

A

– Extends from pharynx to cardiac orifice of stomach
passing through esophageal hiatus in diaphragm
– Lower esophageal sphincter: food pauses here because
of constriction
* Prevents stomach contents from regurgitating into the
esophagus
* Protects esophageal mucosa from erosive stomach acid
* Heartburn—burning sensation produced by acid reflux into
the esophagus

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23
Q

What is the capacity of the stomach?

A

50 ml when empty, 1 to 1.5 l after meal, 4 l when very full

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24
Q

What is the main function of the stomach?

A

to mechanically digest and liquify, begin digestion of protein and fat

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25
Q

What are the regions of the stomach?

A
  • Cardiac region (cardia)—small area within about 3 cm of
    the cardiac orifice
  • Fundic region (fundus)—dome-shaped portion superior to
    esophageal attachment
  • Body (corpus)—makes up the greatest part of stomach
  • Pyloric region—narrower pouch at the inferior end
    – Subdivided into the funnel-like antrum
    – Narrower pyloric canal that terminates at pylorus
    – Pylorus: narrow passage to duodenum
    – Pyloric (gastroduodenal) sphincter—regulates the
    passage of chyme into the duodenum
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26
Q

What nervous signals does the stomach recieve?

A

– Parasympathetic fibers from vagus
– Sympathetic fibers from celiac ganglia

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27
Q

What is the microscopic anatomy of the stomach?

A
  • Stomach has a simple columnar epithelium
    covers mucosa
    – Apical regions of its surface cells are filled with mucin
    – Mucin swells with water and becomes mucus after it is
    secreted
  • Mucosa and submucosa are flat when stomach is
    full, but form longitudinal wrinkles called gastric
    rugae when empty
  • Muscularis externa has three layers (instead of
    the two seen elsewhere)
    – Outer longitudinal, middle circular, and inner oblique
    layers
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28
Q

What are gastric pits? What glands are found there?

A

—depressions in gastric mucosa
* Cardiac glands in cardiac region
* Pyloric glands in pyloric regions
* Gastric glands in the rest of the stomach

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29
Q

What are the cells in the stomach?

A

mucous, regenerative, parietal, chief, enteroendocrine

30
Q

What is gastric juice?

A

water, HCl, pepsin

31
Q

What does HCl do?

A
  • HCl activates pepsin and lingual lipase
  • Breaks up connective tissues and plant cell walls
    – Helps liquefy food to form chyme
  • Converts ingested ferric ions (Fe3+) to ferrous
    ions (Fe2+)
    – Fe2+ absorbed and used for hemoglobin synthesis
  • Contributes to nonspecific disease resistance
    by destroying most ingested pathogens
32
Q

What is the only necessary function of the stomach?

A

secretion of intrinsic factor to make B12 to synthesize Hb

33
Q

What influences gastric motility?

A
  • Swallowing center of medulla oblongata
    signals stomach to relax
  • Soon stomach shows a rhythm of peristaltic
    contractions controlled by pacemaker cells in
    longitudinal layer of muscularis extern
34
Q

Where does absorption occur?

A

small intestine

35
Q

How is the stomach protected?

A

– Mucous coat: thick, highly alkaline mucus resists action
of acid and enzymes
– Tight junctions between epithelial cells prevent gastric
juice from seeping between them and digesting deeper
tissue
– Epithelial cell replacement: cells live only 3 to 6 days
* Sloughed off into the chyme and digested with food
* Replaced rapidly by cell division in gastric pits

36
Q

What are most ulcers caused by?

A

H pylori

37
Q

What does the liver do?

A

secretes bile to contribute to digestion

38
Q

What are the 4 lobes of the liver

A
  • Four lobes—right, left, quadrate, and caudate
    – Falciform ligament separates left and right lobes
  • Sheet of mesentery that suspends the liver from the
    diaphragm
    – Round ligament (ligamentum teres)—fibrous remnant
    of umbilical vein
  • Carries blood from umbilical cord to liver of the fetus
39
Q

What is the porta hepatis?

A

—irregular opening between
quadrate and caudate lobes
– Point of entry for hepatic portal vein and proper
hepatic artery
– Point of exit for the bile passages
– All travel in lesser omentumWha

40
Q

What is the hepatic triad?

A

two vessels
and a bile ductule
– Other vessel: branch of hepatic portal vein
– One vessel: branch of hepatic artery proper
– Both vessels supply blood to sinusoids which receive a
mixture of nutrient-laden venous blood from the
intestines, and freshly oxygenated arterial blood from
the celiac trunk
25-68

41
Q

What are hepatocytes?

A

– After a meal, hepatocytes absorb from the blood:
glucose, amino acids, iron, vitamins, and other nutrients
for metabolism or storage
– Between meals, hepatocytes break down stored
glycogen and release glucose into the blood
– Remove and degrade: hormones, toxins, bile pigments,
and drugs
– Secrete into the blood: albumin, lipoproteins, clotting
factors, angiotensinogen, and other products

42
Q

What are bile canaliculi?

A
  • Bile canaliculi—narrow channels into which the
    liver secretes bile
    – Bile passes into bile ductules of the triads
    – Ultimately into the right and left hepatic ducts
    – Common hepatic duct: formed from convergence of
    right and left hepatic ducts on inferior side of the liver
    – Cystic duct coming from gallbladder joins common
    hepatic duct
    – Bile duct: formed from union of cystic and common
    hepatic ducts
  • Descends through lesser omentum toward the duodenum
43
Q

What happens where the bile duct joins the pancreas?

A

Microscopic Anatomy of the Liver
(Continued)
– Near duodenum, bile duct joins duct of pancreas
– Forms expanded chamber: hepatopancreatic ampulla
* Terminates in a fold of tissue—major duodenal papilla on
duodenal wall
– Major duodenal papilla contains muscular
hepatopancreatic sphincter (sphincter of Oddi)
* Regulates passage of bile and pancreatic juice into
duodenum
* Between meals, sphincter closes and prevents release of
bile into the intestines

44
Q

What is the gallbladder?

A

—a pear-shaped sac on underside of
liver
– Serves to store and concentrate bile by absorbing
water and electrolytes
– About 10 cm long
– Internally lined by highly folded mucosa with simple
columnar epithelium
– Head (fundus) usually projects slightly beyond inferior
margin of liver
– Neck (cervix) leads into the cystic duct

45
Q

What is bile?

A

—yellow-green fluid containing minerals,
cholesterol, neutral fats, phospholipids, bile
pigments, and bile acids
– Bilirubin: principal pigment derived from the
decomposition of hemoglobin
– Bacteria in large intestine metabolize bilirubin to
urobilinogen
* Responsible for the brown color of feces
– Bile acids (bile salts): steroids synthesized from
cholesterol
* Bile acids and lecithin, a phospholipid, aid in fat digestion and
absorption

46
Q

How much bile is reabsorbed?

A

– 80% of bile acids are reabsorbed in the ileum and
returned to the liver
* Hepatocytes absorb and resecrete them
* Enterohepatic circulation—route of secretion, reabsorption,
and resecretion of bile acids two or more times during digestion
of an average meal
– 20% of the bile acids are excreted in the feces
* Body’s only way of eliminating excess cholesterol
* Liver synthesizes new bile acids from cholesterol to replace
those lost in feces

47
Q

What are the 2 portions of the pancreas?

A
  • Endocrine portion—pancreatic islets that secrete insulin
    and glucagon
    – Concentrated in the tail of the gland
  • Exocrine portion—99% of pancreas that secretes 1,200 to
    1,500 mL of pancreatic juice per day
    – Secretory acini release their secretion into small ducts that
    converge on the main pancreatic duct
    25-78
48
Q

What are the ducts of the pancreas?

A

– Pancreatic duct runs lengthwise through middle of the
gland
* Joins the bile duct at the hepatopancreatic ampulla
* Hepatopancreatic sphincter controls release of both bile
and pancreatic juice into the duodenum
– Accessory pancreatic duct: smaller duct that
branches from the main pancreatic duct
* Opens independently into the duodenum
* Bypasses the sphincter and allows pancreatic juice to
be released into duodenum even when bile is not
25-81

49
Q

What is pancreatic juice?

A

– Pancreatic juice: alkaline mixture of water, enzymes,
zymogens, sodium bicarbonate, and other electrolytes
* Acini secrete the enzymes and zymogens
* Ducts secrete bicarbonate
– Bicarbonate buffers HCl arriving from the stomach

50
Q

What are the pancreatic zymogens?

A

– Trypsinogen
* Secreted into intestinal lumen
* Converted to trypsin by enterokinase that is secreted by
mucosa of small intestine
* Trypsin is autocatalytic—converts trypsinogen into still
more trypsin
– Chymotrypsinogen: converted to chymotrypsin by
trypsin
– Procarboxypeptidase: converted to carboxypeptidase
by trypsin

51
Q

What are the other pancreatic enzymes?

A

– Pancreatic amylase: digests starch
– Pancreatic lipase: digests fat
– Ribonuclease and deoxyribonuclease: digest RNA
and DNA respectively

52
Q

What are the 3 stimuli responsible for the release of pancreatic juice and bile?

A

Ach, cholesystokinin, and secretin
25-86
– Acetylcholine (ACh): from vagus and enteric nerves
* Stimulates acini to secrete enzymes during cephalic phase
of gastric control even before food is swallowed
– Enzymes remain in acini and ducts until chyme enters the
duodenum
– Cholecystokinin (CCK): secreted by mucosa of
duodenum in response to arrival of fats in small intestine
* Stimulates pancreatic acini to secrete enzymes
* Strongly stimulates gallbladder
* Induces contractions of gallbladder and relaxation of
hepatopancreatic sphincter to discharge bile into duodenum
– Secretin: released from duodenum in response to acidic
chyme arriving from the stomach
* Stimulates ducts of both liver and pancreas to secrete more
sodium bicarbonate
* Raises pH to the level required for activity of the pancreatic
and intestinal digestive enzymes

53
Q

What are the regions of the small intestine?

A

– Duodenum: first 25 cm (10 in.)
* Begins at pyloric valve
– Major and minor duodenal papilla distal to pyloric valve
– Receives major and minor pancreatic ducts respectively
* Arches around head of the pancreas
* Ends at a sharp bend called the duodenojejunal flexure
* Most is retroperitoneal
– Jejunum: first 40% of small intestine beyond duodenum
* Has large, tall, closely spaced circular folds
* Its wall is relatively thick and muscular
* Especially rich blood supply which gives it a red color
– Ileum: forms last 60% of the postduodenal small intestine
* Thinner, less muscular, less vascular, and paler pink color
* Peyer patches—prominent lymphatic nodules in clusters on
the side opposite the mesenteric attachment
– Visible to naked eye; become larger near large intestine
* Ileocecal junction—end of the small intestine
– Where the ileum joins the cecum of the large intestine
* Ileocecal valve—a sphincter formed by the thickened
muscularis of the ileum
– Protrudes into the cecum
– Both jejunum and ileum are intraperitoneal and covered
with serosa

54
Q

What helps with small intestine absorption?

A

– Lumen lined with simple columnar epithelium
– Muscularis externa is noted for a thick inner circular layer
and a thinner outer longitudinal layer
– Large internal surface area - great length and three
types of internal folds or projections
* Circular folds (plicae circulares)—increase surface area
by a factor of 2 to 3
* Villi—increase surface area by a factor of 10
* Microvilli—increase the surface area by a factor of 20
* Circular folds (plicae circulares)—largest folds of
intestinal wall

55
Q

What are the features of villi?

A

– Villus covered with two types of epithelial cells
* Absorptive cells (enterocytes)
* Goblet cells—secrete mucus
– Epithelia joined by tight junctions that prevent digestive
enzymes from seeping between them
– Core of villus filled with areolar tissue of lamina propria
* Contains arteriole, capillaries, venule, and lymphatic
capillary called a lacteal

56
Q

What are the features of microvilli?

A

—form a fuzzy brush border on apical
surface of each absorptive cell
– About 1 μm high
– Increases absorptive surface area
* Brush border enzymes—contained in plasma
membrane of microvilli
– Carry out some of the final stages of enzymatic digestion
– Not released into the lumen
– Contact digestion: chyme must contact the brush border
for digestion to occur
– Intestinal churning of chyme ensures contact with the
mucosa

57
Q

What do the contractions of small intestine do?

A

– To mix chyme with intestinal juice, bile, and
pancreatic juice
* To neutralize acid
* Digest nutrients more effectively
– To churn chyme and bring it in contact with the
mucosa for contact digestion and nutrient absorption
– To move residue toward large intestine
25-100

58
Q

What does intestinal motility start with?

A

segmentation set by pacemaker cells

59
Q

What is the purpose of segmentation

A

mix and churn

60
Q

What does peristalsis do?

A
  • Peristalsis moves contents of small intestine toward
    colon
  • Peristaltic wave begins in duodenum, travels 10 to 70 cm
    and dies out
61
Q

What does the ileocecal valve do?

A

usually closed
– Food in stomach triggers gastroileal reflex that enhances
segmentation in the ileum and relaxes the valve
– As cecum fills with residue, pressure pinches the valve shut
* Prevents reflux of cecal contents into the ileum

62
Q

Walk through carbohydrate digestion

A

Mouth: starch gets broken up by salivary amylase into oligosaccharide and maltose, sucrose and lactose continue down
Stomach: none
Small intestine (lumen): pancreatic amylase creates more maltose
Small intestine (epithelium): sucrase and lactase break down sugars into fructose and galactose, maltase breaks down maltose into glucose
Goes into blood capillary

63
Q

Walk through protein digestion

A

Mouth: none
Stomach: pepsin breaks down into peptides
Small intestine (lumen): trypsin, chymotrypsin, and carboxypeptidase create dipeptides
Small intestine (epithelium): dipeptidase and aminopeptidase create amino acids
goes into blood capilary

64
Q

Walk through fat digestion

A

mouth: none
stomach: lingual lipase activated
small intestine (lumen): the lipases create monoglycerides and free fatty acids
small intestine (epithelium): monoglyerice + ffa = triglyceride, + cholesterol etc lead to chylomicrons
goes into lacteal

65
Q

what digests nucleic acids?

A

nucleases, nucleosidases, and phosphatases

66
Q

What happens to vitamins?

A

absorb most

67
Q

Where is most water absorbed?

A

small intestine

68
Q

What makes diarrhea happen?

A

too little water absorbed

69
Q

What makes constipation happen?

A

too much water absorbed

70
Q

What is the large intestine anatomy?

A

– Begins as cecum inferior to ileocecal valve
– Appendix attached to lower end of cecum
* Densely populated with lymphocytes—a significant source
of immune cells
– Ascending colon, right colic (hepatic) flexure,
transverse colon, left colic (splenic) flexure, and
descending colon frame the small intestine
– Sigmoid colon is S-shaped portion leading down into
pelvic cavity
– Rectum: portion ending at anal canal
* Has three curves and three infoldings, called the
transverse rectal folds (rectal valves)
– Anal canal: final 3 cm of the large intestine
* Passes through levator ani muscle and pelvic floor,
terminates at the anus
* Anal columns and sinuses—exude mucus and
lubricant into anal canal during defecation
* Large hemorrhoidal veins for superficial plexus in
anal columns and around orifice
* Hemorrhoids—permanently distended veins that
protrude into anal canal or bulge outside the anus
– Muscularis externa of colon is unusual
* Taenia coli—longitudinal fibers concentrated in
three thickened, ribbon-like strips
* Haustra—pouches in the colon caused by the
muscle tone of the taeniae coli
* Internal anal sphincter—smooth muscle of
muscularis externa
* External anal sphincter—skeletal muscle of pelvic
diaphragm
– Omental appendages—club-like, fatty pouches of
peritoneum adhering to the colon; unknown function

71
Q

Where is feces found?

A

transverse colon

72
Q

What moves feces?

A

Haustral contractions, gastrocolic and duodenocolic reflexes

Anatomy (14 decks)

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