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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
mastication
chewing, mixing food with saliva and enzymes
26
oral cavity lined by which kind of tissue
stratified squamous epithelium
27
Palate
roof of the mouth
28
Which palate closes has muscle underneath and closes off the nasopharynx when we swallow?
soft palate
29
Which palate has bone underneath?
hard palate
30
oropharynx contains palatine tonsils and bounded by two paired sets of arches
Fauces
31
connects oral cavity to oropharynx
Isthmus of the fauces
32
Know slide 14
yes
33
Bolus
compact mass before swallowing
34
secures tongue to the floor of the mouth
lingual frenulum
35
Peg-like projections on the superior surface of tongue
papillae
36
Provide friction for manipulating food | Other papillae house taste buds
Filiform papillae
37
Posterior portion of tongue is in the oropharynx; it contains the
lingual tonsil
38
Most saliva is produced by paired (BLANK) that empty secretions into mouth
extrinsic salivary glands
39
Parotid glands
near ears; ducts open into upper jaw Mumps is a viral infection of the parotid glands, which can lead to sterility in adult males
40
Submandibular glands
Located beneath oral cavity floor; ducts open near base of frenulum
41
Under tongue; ducts open into floor of mouth
sublingual glands
42
Intrinsic salivary glands
scattered around mouth add saliva, mostly keep mouth moist
43
2 types of salivary glands
Serous cells--produce watery secretion containing enzymes and ions Mucous cells--produce mucus (a stringy, viscous solution containing mucin)
44
Amylase
enzyme that helps digest starchy foods
45
Role of saliva (3)
1) Cleanses and lubricates mouth and teeth 2) Dissolves food chemicals to be tasted 3) Moistens food and helps make bolus
46
Saliva Composition
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)
47
Intrinsic salivary glands
keep mouth moist
48
Extrinsic salivary glands
activated when we eat
49
Salivation stimulated by...
chemoreceptors | mechanoreceptors
50
Halitosis
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) ```
51
Pharyngeal constrictor muscles
muscles propel food into esophagus below
52
Esophogeal hiatus
opening in diagphragm
53
The esophagus joins
cardial orifice of the stomach, which surrounded by gastroesophageal sphincter
54
when it's not being used, the esophagus
collapses
55
esophageal mucosa
- -nonkeratinized stratified squamous epithelium ( resists abrasion) - -changes abruptly to the simple columnar epithelium of stomach (secretion)
56
esophageal submucosa
--mucus-secreting esophageal glands--bolus compresses--causing secrete mucus “greases” esophageal walls, aids food passage
57
muscularis externa
- -skeletal muscle (outermost) - -a mixture of skeletal and smooth muscle (middle) - -and entirely smooth muscle (innermost)
58
Serosa (visceral peritoneum) is replaced by what in the esophagus?
adventitia (dense connective tissue binds esophagus to surroundings)
59
GERD (gastroesophageal reflux disease)
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
Phases of Swallowing
1) Buccal phase (voluntary) 2) Pharyngeal-esophogeal phase (involuntary) 3) Pharyngeal-esophogeal phase continues (involuntary)
61
Stomach is a...
storage tank where protein digestion begins asymmetrical
62
Food converted into (in stomach)
chyme
63
esophagus enters stomach at the...
cardia
64
Mesenteries called “omenta” extend from curvatures to tether stomach in place
Greater omentum lacey apron b/c fatty deposits; | also lymph nodes and immune cells patrol peritoneal cavity
65
Pyloric sphincter controls stomach emptying into the
duodenum
66
all 4 layers present in stomach, but only two specialized
1) muscularis externa (3rd layer of smooth muscle cells) | 2) outer layer of stomach mucosa
67
majority of the digestion occurs in the
small intestine
68
Stomach mucosa specialization
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
Stomach muscularis externa specialization
(3rd layer of smooth muscle cells)
70
H20+CO2=>H2CO3=>
H + HCO3
71
most gastric juice is produced in the
fundus and body
72
mucous neck cells
Produce soluble, acidic mucus; function unknown
73
Parietal cells
produce HCl and intrinsic factor (VIt B12) | only essential fxn of the stomach
74
Enzyme digests protein
pepsin
75
: Secrete pepsinogen (inactive pepsin)
chief cells in stomach
76
Release paracrines and hormones into interstitial fluid of lamina propria (stomach)
Enteroendocrine cells | --regulate local internal activity in the stomach
77
Acid and pepsin could destroy the stomach itself, were it not for the mucosal barrier, which is made up of three factors:
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
Gastritis--Inflammation of stomach wall due to breach in
mucosal barrier
79
Gastric ulcer
Erosion of the stomach wall Could lead to perforation of the stomach wall, peritonitis, and massive hemorrhage
80
Ulcer caused by
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
Phase 1 of gastric juice secretion
``` 1) Cephalic phase “Head” stimulus Only lasts a few minutes Parasympathetic Stimulates gastric glands ```
82
Phase 2 of gastric juice secretion
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
Intestinal phase
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
Inhibition during intestinal phase prevents acid from damaging small intestine and from
too much chyme overwhelming the digestive and absorptive capacity of the small intestine
85
HCl secreted by
parietal cells in lumen
86
Fundus and body serve primarily as
storage areas involved in chemical digestion. Food gets a real physical beating in the pylorus.
87
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.
30 mL 3 mL 27 mL
88
Enteric pacemaker cells
(muscle-like cells do not contract) set peristalsis pace in the stomach: 3 waves/minute by spontaneous depolarization
89
stomach empties completely within
4 hours of a meal
90
enterogastrones and enterogastric reflexes
turn off stomach emptying
91
fatty meals take longer because
most digestion of fatty food happens in the small intestine, so digestion slows
92
Vomiting (emesis)
triggered by extreme stretching of the stomach or irritants controlled by emetic center of the medulla oblongata can expel duodenal contents
93
Severe vomiting
disturbs electrolyte balance | increases blood pH (stomach reestablishes acidic environment)
94
liver's digestive function
produce bile (emulsifies fat)
95
liver can regenerate to former size in
6-12 months, even if 80 percent was removed
96
liver is the largest
gland in the body | it's on the right side
97
four lobes of the liver
right left quadrate caudate
98
accommodates gall bladder
right lobe
99
fibrous remnant of the fetal umbilical vein
round ligament (liver)
100
Porta hepatis
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
Common hepatic duct
fuses with cystic duct (draining gallbladder), forming bile duct
102
Sesame seed-sized structural and functional units
liver lobules
103
liver lobules made of:
Plates of hepatocytes (liver cells) radiate from central vein (like pages of a folded paperback book)
104
Hexagonal with “portal triads” at each corner (3)
- -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
Liver sinusoids
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
Stellate (hepatic) macrophages
make up sinusoid walls, gobbling up debris, pathogens, worn-out RBCs
107
Bile made by hepatocytes
Bile canaliculi => Bile ducts (in portal triad) => Common hepatic duct => Duodenum
108
Blood and bile flow in which direction relative to each other?
opposite
109
plasma proteins in hepatocytes help
maintain blood osmolarity
110
Bile (steroid)
yellow-green alkaline (basic) solution containing bile salts, bile pigments, cholesterol, triglycerides, phospholipids, & electrolytes Only bile salts and phospholipids aid digestion
111
Bile salts are derivatives of what?
cholesterol (e.g., cholic acid) that help in digestion and absorption of fats
112
Chief bile pigment is
bilirubin (yellow breakdown product of heme)
113
What do liver cells do with bilirubin?
absorb and excrete it | small intestinal bacteria convert bilirubin into stercobilin (why poop is brown)
114
gall bladder
Thin sac; 4 inches long; size of kiwi | Stores bile not needed immediately for digestion and removes water to concentrate it
115
Bile flow:
Cystic duct => Bile duct
116
Gallstones
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
pancreas
secretes enzymes that break down food molecules
118
Exocrine function of pancreas
Produce pancreatic juice (enzymes + bicarbonate)
119
Clusters of secretory acinar cells that produce lots of enzymes; contain zymogen granules (which contain inactive enzymes called proenzymes)
Acini (exocrine function of pancreas)
120
transport proenzymes; epithelial cells of ducts secrete water and bicarbonate (pH 8)
Ducts (exocrine function of pancreas)
121
'Pancreatic juice
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
Bile duct and main pancreatic duct (which carries pancreatic juice) unite at
wall of duodenum Fuse at bulblike structure called hepatopancreatic ampulla
123
Hepatopancreatic sphincter (where bile duct and main pancreatic duct meet)
controls entry of bile and pancreatic juice
124
empties directly into duodenum
accessory pancreatic duct
125
don't need to know slide 45
no
126
small intestine
virtually all absorption pyloric sphincter to ileocecal valve 7-20 feet) 1-1.6 inches in diameter
127
3 segments of small intestine
duodenum jejunum ileum
128
Duodenum
10 inches long (major duodenal papilla receives secretion
129
jejunum
8 feet long
130
ileum
12 feet long | joins large intestine at ileocecal valve
131
Small intestine structural adaptations (3)
circular folds villi microvilli
132
circular folds in small intestine
About 1 cm tall; cause chyme to slow down and spiral through lumen
133
villi
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
microvilli
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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