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Anatomy and physiology > Digestive System > Flashcards

Digestive System Flashcards

1
Q

6 functions of digestive system

A

1) Ingestion
2) Propulsion: Movement of food via peristalsis
3) Mechanical breakdown: Increases surface area of food by chewing, stomach churning, and segmentation
4) Digestion: Breakdown of food into chemical building blocks via enzymes
5) Absorption: Digested end products, water, vitamins, and minerals cross lumen of GI tract into blood or lymph vessels
6) Defecation: Elimination of indigestible waste

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2
Q

Segmentation (water balloon squeezed from both ends and mix inside) mixes food with digestive juices and makes absorption more efficient by

A

repeatedly moving different parts of the food mass over the intestinal wall

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3
Q

alimentary canal

A

Gastrointestinal (GI) tract–Digests food (i.e., breaks it down into smaller fragments) and absorbs molecules
~30 feet long
–Inside GI tract is considered “outside” the body because tube is open at both ends

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4
Q

Accessory digestive organs

A

Aid digestion
Teeth, tongue, gall bladder
Glands: Salivary glands, liver, pancreas (which connect to GI tract via ducts)

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5
Q

,Mesentery

A

Double layer of peritoneum (a double double membrane)
Two serous membranes fused back-to-back

routes for blood vessels, lymphatics, and nerves to reach digestive viscera
Hold organs in place
Store fat

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6
Q

Inflammation of peritoneum

A

Peritonitis (often lethal)

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7
Q

Peritonitis causes

A

Most common: Burst appendix that sprays bacteria-containing feces all over peritoneum

Piercing abdominal wound

Perforating ulcer that leaks stomach juices into the peritoneal cavity

Infection acquired during abdominal surgery

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8
Q

Mucosa (mucous membrane)

A

Innermost layer: Secretes mucus, digestive enzymes, hormones
Absorbs end products into blood
Protects against disease

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9
Q

1st sublayer of mucosa

A

Simple columnar epithelium (in most places)

mucus-producing cells protect organs from being digested by own juices; some places enzyme-producing and hormone-secreting cells

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10
Q

2nd sublayer of mucosa: lamina propria

A

(loose areolar connective tissue)
Capillaries nourish epithelium and absorb nutrients
MALT (mucosa-associated lymphoid tissue) protects us from pathogens

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11
Q

3rd sublayer of mucosa: Muscularis muscosae

A

Scant sublayer of smooth muscle movement helps with absorption and secretion

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12
Q

Submucosa

A

Loose areolar connective tissue

contain blood and lymph vessels, lymphoid follicles, nerve fibers

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13
Q

Muscularis externa

A

two layers smooth muscle (peristalsis and segmentation)

sphincters

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14
Q

Serosa

A

Outermost layer
visceral peritoneum
Areolar connective + simple squamous epithelium (mesothelium)

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15
Q

Muscle fibers run parallel to long axis of organ

Contraction shortens organ

A

longitudinal layer

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16
Q

Fibers run circumference of organ
Contraction constricts the lumen (cavity inside)
This layer forms sphincters

A

circular layer

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17
Q

Splanchic Circulation

A

arteries serve digestive organs and hepatic portal circulation
–receives about 25% of cardiac output (plus after eating)

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18
Q

Hepatic Portal Circulation

A

collects nutrient-rich venous blood from digestive organs and delivers it to liver

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19
Q

Enteric System

A

GI tract’s own nervous system (Semiautonomous)

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20
Q

Regulating Digestion

A

=>Receptors in walls of GI tract provoked by chemical and mechanical stimuli
=>Effectors of digestive activity include smooth muscle (peristalsis, segmentation) and glands (which secrete enzymes, hormones, etc.)
=>Neurons (intrinsic and extrinsic) and hormones control digestive activity

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21
Q

Short Reflex Arc

A

mediated by enteric nervous system (ENS) in response to stimuli within GI tract
Regulates segmentation and peristalsis
Involves pacemaker cells and reflex arcs between enteric neurons (“intrinsic control”)

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22
Q

Long Reflex Arc

A

ENS and CNS
Initiated by stimuli
Enteric nervous system sends info to CNS, receives impulses from autonomic nervous system (“extrinsic control”)

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23
Q

Sympathetic response “turns off” digestion

A

Parasympathetic response “Turns on” digestion

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24
Q

oral cavity

A

mouth

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25
Q

mastication

A

chewing, mixing food with saliva and enzymes

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26
Q

oral cavity lined by which kind of tissue

A

stratified squamous epithelium

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27
Q

Palate

A

roof of the mouth

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28
Q

Which palate closes has muscle underneath and closes off the nasopharynx when we swallow?

A

soft palate

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29
Q

Which palate has bone underneath?

A

hard palate

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30
Q

oropharynx contains palatine tonsils and bounded by two paired sets of arches

A

Fauces

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31
Q

connects oral cavity to oropharynx

A

Isthmus of the fauces

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32
Q

Know slide 14

A

yes

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33
Q

Bolus

A

compact mass before swallowing

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34
Q

secures tongue to the floor of the mouth

A

lingual frenulum

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35
Q

Peg-like projections on the superior surface of tongue

A

papillae

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36
Q

Provide friction for manipulating food

Other papillae house taste buds

A

Filiform papillae

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37
Q

Posterior portion of tongue is in the oropharynx; it contains the

A

lingual tonsil

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38
Q

Most saliva is produced by paired (BLANK) that empty secretions into mouth

A

extrinsic salivary glands

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39
Q

Parotid glands

A

near ears; ducts open into upper jaw

Mumps is a viral infection of the parotid glands, which can lead to sterility in adult males

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40
Q

Submandibular glands

A

Located beneath oral cavity floor; ducts open near base of frenulum

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41
Q

Under tongue; ducts open into floor of mouth

A

sublingual glands

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42
Q

Intrinsic salivary glands

A

scattered around mouth add saliva, mostly keep mouth moist

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43
Q

2 types of salivary glands

A

Serous cells–produce watery secretion containing enzymes and ions

Mucous cells–produce mucus (a stringy, viscous solution containing mucin)

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44
Q

Amylase

A

enzyme that helps digest starchy foods

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45
Q

Role of saliva (3)

A

1) Cleanses and lubricates mouth and teeth
2) Dissolves food chemicals to be tasted
3) Moistens food and helps make bolus

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46
Q

Saliva Composition

A

97%-99.5% water
pH 6.5-7.0(slightly acidic)
Contains electrolytes, mucin, immune proteins (IgA, lysozyme, defensins), and digestive enzymes (amylase and lipase)

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47
Q

Intrinsic salivary glands

A

keep mouth moist

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48
Q

Extrinsic salivary glands

A

activated when we eat

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49
Q

Salivation stimulated by…

A

chemoreceptors

mechanoreceptors

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50
Q

Halitosis

A

if inhibits saliva secretion, then promotes tooth decay
Decomposing food particles accumulate, causing bacteria to flourish

Hydrogen sulfide (rotten egg smell)
Methyl mercaptan (also in feces)
Cadaverine (also in rotting corpses)
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51
Q

Pharyngeal constrictor muscles

A

muscles propel food into esophagus below

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52
Q

Esophogeal hiatus

A

opening in diagphragm

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53
Q

The esophagus joins

A

cardial orifice of the stomach, which surrounded by gastroesophageal sphincter

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54
Q

when it’s not being used, the esophagus

A

collapses

55
Q

esophageal mucosa

A
  • -nonkeratinized stratified squamous epithelium ( resists abrasion)
  • -changes abruptly to the simple columnar epithelium of stomach (secretion)
56
Q

esophageal submucosa

A

–mucus-secreting esophageal glands–bolus compresses–causing secrete mucus “greases” esophageal walls, aids food passage

57
Q

muscularis externa

A
  • -skeletal muscle (outermost)
  • -a mixture of skeletal and smooth muscle (middle)
  • -and entirely smooth muscle (innermost)
58
Q

Serosa (visceral peritoneum) is replaced by what in the esophagus?

A

adventitia (dense connective tissue binds esophagus to surroundings)

59
Q

GERD (gastroesophageal reflux disease)

A

Caused by conditions that push abdominal contents upward

(obesity, pregnancy, running)

also caused by hiatal hernia, in which stomach bulges upward into esophagus; sphincter can’t close

60
Q

Phases of Swallowing

A

1) Buccal phase (voluntary)
2) Pharyngeal-esophogeal phase (involuntary)
3) Pharyngeal-esophogeal phase continues (involuntary)

61
Q

Stomach is a…

A

storage tank
where protein digestion begins
asymmetrical

62
Q

Food converted into (in stomach)

A

chyme

63
Q

esophagus enters stomach at the…

A

cardia

64
Q

Mesenteries called “omenta” extend from curvatures to tether stomach in place

A

Greater omentum lacey apron b/c fatty deposits;

also lymph nodes and immune cells patrol peritoneal cavity

65
Q

Pyloric sphincter controls stomach emptying into the

A

duodenum

66
Q

all 4 layers present in stomach, but only two specialized

A

1) muscularis externa (3rd layer of smooth muscle cells)

2) outer layer of stomach mucosa

67
Q

majority of the digestion occurs in the

A

small intestine

68
Q

Stomach mucosa specialization

A

outer layer of stomach mucosa (mucous cells arranged as simple columnar epithelium, neutralize acid)
two-layer coat of mucus
–Surface layer=viscous, insoluble mucus
–Inner layer=bicarbonate (a base)
Epithelium has deep gastric pits lead to gastric glands that produce gastric juice

69
Q

Stomach muscularis externa specialization

A

(3rd layer of smooth muscle cells)

70
Q

H20+CO2=>H2CO3=>

A

H + HCO3

71
Q

most gastric juice is produced in the

A

fundus and body

72
Q

mucous neck cells

A

Produce soluble, acidic mucus; function unknown

73
Q

Parietal cells

A

produce HCl and intrinsic factor (VIt B12)

only essential fxn of the stomach

74
Q

Enzyme digests protein

A

pepsin

75
Q

: Secrete pepsinogen (inactive pepsin)

A

chief cells in stomach

76
Q

Release paracrines and hormones into interstitial fluid of lamina propria (stomach)

A

Enteroendocrine cells

–regulate local internal activity in the stomach

77
Q

Acid and pepsin could destroy the stomach itself, were it not for the mucosal barrier, which is made up of three factors:

A

1) Bicarbonate-rich mucus (stomach wall) neutralize HCl
2) Epithelial cells of mucosa joined by tight junctions prevent gastric juice from leaking into underlying tissues

3) Damaged epithelial mucosal cells quickly replaced by division of stem cells (that reside where gastric pits join gastric glands)
(((((((Surface epithelium of mucous cells is completely replaced every 3-6 days))))))) <=SUPER IMPT

78
Q

Gastritis–Inflammation of stomach wall due to breach in

A

mucosal barrier

79
Q

Gastric ulcer

A

Erosion of the stomach wall

Could lead to perforation of the stomach wall, peritonitis, and massive hemorrhage

80
Q

Ulcer caused by

A

Helicobacter pylori
–about half of people are infected, but most uninfected

Some caused by long-term use of NSAIDs (nonsteroidal anti-inflammatory drugs like aspirin)

81
Q

Phase 1 of gastric juice secretion

A 
1) Cephalic phase
“Head” stimulus
Only lasts a few minutes
Parasympathetic
Stimulates gastric glands
82
Q

Phase 2 of gastric juice secretion

A

Local neuronal and hormonal controls
Lasts 3-4 hours
2/3 gastric juice released
Most important stimuli: distension, peptides, low acidity (higher pH)
Gastrin stimulates HCl
Sympathetic activation (fight-or-flight) inhibits

83
Q

Intestinal phase

A

Initially, it is stimulatory (gastrin encourages gastric glands to continue their activity)
Then, distension of duodenum and acidic chyme inhibit gastric secretions via neuronal and hormonal controls
2c = Negative feedback

84
Q

Inhibition during intestinal phase prevents acid from damaging small intestine and from

A

too much chyme overwhelming the digestive and absorptive capacity of the small intestine

85
Q

HCl secreted by

A

parietal cells in lumen

86
Q

Fundus and body serve primarily as

A

storage areas involved in chemical digestion. Food gets a real physical beating in the pylorus.

87
Q

Pylorus only holds about BLANK of chyme. Each peristaltic wave squirts BLANK of chyme into duodenum. The other BLANK undergoes retropulsion for further churning. This converts solids into liquids.

A

30 mL
3 mL
27 mL

88
Q

Enteric pacemaker cells

A

(muscle-like cells do not contract) set peristalsis pace in the stomach: 3 waves/minute by spontaneous depolarization

89
Q

stomach empties completely within

A

4 hours of a meal

90
Q

enterogastrones and enterogastric reflexes

A

turn off stomach emptying

91
Q

fatty meals take longer because

A

most digestion of fatty food happens in the small intestine, so digestion slows

92
Q

Vomiting (emesis)

A

triggered by extreme stretching of the stomach or irritants
controlled by emetic center of the medulla oblongata
can expel duodenal contents

93
Q

Severe vomiting

A

disturbs electrolyte balance

increases blood pH (stomach reestablishes acidic environment)

94
Q

liver’s digestive function

A

produce bile (emulsifies fat)

95
Q

liver can regenerate to former size in

A

6-12 months, even if 80 percent was removed

96
Q

liver is the largest

A

gland in the body

it’s on the right side

97
Q

four lobes of the liver

A

right
left
quadrate
caudate

98
Q

accommodates gall bladder

A

right lobe

99
Q

fibrous remnant of the fetal umbilical vein

A

round ligament (liver)

100
Q

Porta hepatis

A

allows passage of the hepatic artery proper, hepatic portal vein, and common hepatic duct (formed by merger of right and left hepatic ducts, which carry bile)

101
Q

Common hepatic duct

A

fuses with cystic duct (draining gallbladder), forming bile duct

102
Q

Sesame seed-sized structural and functional units

A

liver lobules

103
Q

liver lobules made of:

A

Plates of hepatocytes (liver cells) radiate from central vein (like pages of a folded paperback book)

104
Q

Hexagonal with “portal triads” at each corner (3)

A
  • -Branch of hepatic artery proper (O2-rich blood to liver)
  • -Branch of hepatic portal vein (carries nutrient-rich blood from digestive organs)
  • -Bile duct
105
Q

Liver sinusoids

A

blood vessels working their way through liver lobules
take blood from hepatic artery proper and from hepatic portal veins

Blood flow: Portal triads => Central veins => Hepatic veins (drain the liver) => Inferior vena cava

106
Q

Stellate (hepatic) macrophages

A

make up sinusoid walls, gobbling up debris, pathogens, worn-out RBCs

107
Q

Bile made by hepatocytes

A

Bile canaliculi => Bile ducts (in portal triad) => Common hepatic duct => Duodenum

108
Q

Blood and bile flow in which direction relative to each other?

A

opposite

109
Q

plasma proteins in hepatocytes help

A

maintain blood osmolarity

110
Q

Bile (steroid)

A

yellow-green alkaline (basic) solution containing bile salts, bile pigments, cholesterol, triglycerides, phospholipids, & electrolytes
Only bile salts and phospholipids aid digestion

111
Q

Bile salts are derivatives of what?

A

cholesterol (e.g., cholic acid) that help in digestion and absorption of fats

112
Q

Chief bile pigment is

A

bilirubin (yellow breakdown product of heme)

113
Q

What do liver cells do with bilirubin?

A

absorb and excrete it

small intestinal bacteria convert bilirubin into stercobilin (why poop is brown)

114
Q

gall bladder

A

Thin sac; 4 inches long; size of kiwi

Stores bile not needed immediately for digestion and removes water to concentrate it

115
Q

Bile flow:

A

Cystic duct => Bile duct

116
Q

Gallstones

A

Bile (excreting cholesterol)
Too much cholesterol crystalize => gallstones (can be painful or asymptomatic)
If gallbladder removed, bile duct enlarges to assume the bile-storing role

117
Q

pancreas

A

secretes enzymes that break down food molecules

118
Q

Exocrine function of pancreas

A

Produce pancreatic juice (enzymes + bicarbonate)

119
Q

Clusters of secretory acinar cells that produce lots of enzymes; contain zymogen granules (which contain inactive enzymes called proenzymes)

A

Acini (exocrine function of pancreas)

120
Q

transport proenzymes; epithelial cells of ducts secrete water and bicarbonate (pH 8)

A

Ducts (exocrine function of pancreas)

121
Q

‘Pancreatic juice

A

High pH neutralize acidic chyme
Enzymes: Proteases (proteins), amylase (starch), lipases (fats), nucleases (nucleic acids)
Enzymes secreted as inactive proenzymes and are activated in the duodenum (prevents pancreas from digesting itself)

122
Q

Bile duct and main pancreatic duct (which carries pancreatic juice) unite at

A

wall of duodenum

Fuse at bulblike structure called hepatopancreatic ampulla

123
Q

Hepatopancreatic sphincter (where bile duct and main pancreatic duct meet)

A

controls entry of bile and pancreatic juice

124
Q

empties directly into duodenum

A

accessory pancreatic duct

125
Q

don’t need to know slide 45

A

no

126
Q

small intestine

A

virtually all absorption
pyloric sphincter to ileocecal valve
7-20 feet)
1-1.6 inches in diameter

127
Q

3 segments of small intestine

A

duodenum
jejunum
ileum

128
Q

Duodenum

A

10 inches long (major duodenal papilla receives secretion

129
Q

jejunum

A

8 feet long

130
Q

ileum

A

12 feet long

joins large intestine at ileocecal valve

131
Q

Small intestine structural adaptations (3)

A

circular folds
villi
microvilli

132
Q

circular folds in small intestine

A

About 1 cm tall; cause chyme to slow down and spiral through lumen

133
Q

villi

A

1 mm high that give organ a velvety texture

Each villus has absorptive cells around a core of blood and lymph vessels (see next slide)

134
Q

microvilli

A

Cytoplasmic extensions absorptive cells collectively called brush border

Brush border enzymes help complete digestion of carbohydrates and proteins

Anatomy and physiology (21 decks)

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