digestive system Flashcards Preview

physiology > digestive system > Flashcards

Flashcards in digestive system Deck (149):
1

the function of the digestive system?

to transfer nutrients, water, and electrolytes from the food we eat into the bodies internal environment

2

What percentage of injected food is available for the bodies use?

95%

3

What is motility?

refers to the motility of muscular contractions that mix and move forward the contents of the digestive tract
-includes propulsive movements and mixing movements

4

Propulsive movements

-propel or push contents forward
-moves food forward in a given segment at the appropriate velocity to allow that segment to perform its functions
ex. protein rich foods move more slowly through the stomach

5

Mixing movements

-mix food with digestive juices (promotes digestion)
-facilitates absorbing, exposes all portions of the food contents to the absorbing surface of the digestive tract

6

What is secretion?

-digestive juices that are secreted into the digestive tract lumen by exocrine glands
-secretions consist of water, electrolyses, and specific organic constituents that are used for synthesis of enzymes ,bile sates, and mucus.
-requires neural or hormonal stimulation to release the secretion from plasma into digestive tract

7

What 3 different biochemical categories does digestion include?

-carbohydrates (CHO)
-proteins
-fats

8

what is digestion?

refers to the biochemical breakdown of structurally complex foodstuff into smaller, absorbable units by enzymes produced in the tract

9

The most injected form of carbohydrates are in the form of

polysaccharides

10

types of carbohydrates and thier sources

starch: from plants
cellulose: found in plant walls
glycogen- body muscles (meat)

11

Proteins are degraded primarily into..

thier constitutes amino acids as well as few small polypeptides
-found in dairy products

12

Most dietary fats are in the form of

triglycerides, which consist of glycerol and 3 fatty acids

13

Process of fat digestion and end products?

during digestion, two fatty acid molecules split off, leaving a monoglycerdies and free fatty acids
-the end products of fat digestion are monoglycerides and free fatty acids, which are absorbable units of fat

14

Where does complete digestion and absorption take place?

in the small intestine
-small absorbable units along with water, electrolytes, and vitamins from the digestive tract are absorbed into the blood and lymph

15

what are the accessory digestive organs?

-salivary glands
-exocrine pancreas
-biliary system (gall bladder and liver)

16

what are the digestive organs?

mouth
pharynx (throat)
esophagus
stomach
small intestine
large intestine
booty hole

17

From inner to outer layer, what is the order of the digestive tract structure?

1) mucosa - inner layer
2) submucosa
3) mascularis externa
4) serosa- outer layer

18

What layers are the in mucosa?

1) Mucosa membrane
2) Lamina propria
3) Muscularis mucosa

19

mucosa membrane

-serves as a protective surface
-contains exocrine gland cells for secretion of juices
-contains endocrine glands for secretion of blood-borne GI hormones
-epithelial cells- for absorbing digested nutrients

20

Lamina propria

-thin layer of connective tissue
-houses GALT, which is important against the defence of disease-causing intestinal bacteria

21

Muscularis mucosa

layer of smooth muscle
outermost layer in innermost layer, lol

22

submucosa

middle layer
elasticity
contains larger blood and lymph vessels

23

Muscularis mucosa

-major smooth muscle coat of digestive tube
-has two layers:
1) circular layer- contraction decreases the diameter of the lumen
2) longitudinal layer- contraction shorters tube
-together, contractile activity of these smooth muscles produces the propulsive and mixing movements

24

Serosa

outer connective tissue
-secretes serous fluid that lubricates and prevents friction between digestive organs

25

Salivas composition

99.5% water
0.5% electrolytes and proteins (amylase, mucus, and lysozyme)

26

Salivary amylase does what

it's an enzyme that breaks down carbohydrates
1) polysaccharides
2) amylase
3) disacchride
4) maltose

27

what does the antibacterial portion of saliva do?

contains antibacterial action by lysozymes which destroy bacteria by breaking their cell wall

28

What does pancreatic amylase in GHO digestion do?

Polysaccharides
(pancreatic amylase)
-> disaccorides
-> monosacchorides

29

Parasympathetic influences on salivary secretion?

stimulates a prompt and abundant flow of water saliva rich enzymes

30

sympathetic influence on salivary secretion?

stimulates elicit smaller volume of saliva, the mouth is drier than usual (during stress)

31

When is swallowing initiated?

-When bolus is voluntarily forced by tongue rear of mouth into the pharynx, it cannot be stopped once it has begun since that portion is involuntary "all or none response"

32

What are the two stages of swallowing?

1) oropharyngeal stage -voluntary
2) esophageal stage- involuntary

33

Openings sealed off during swallowing:

-The position of the tongue against hard plate keeps food from re-entering the mouth
-uvula is elevated against the back of the throat, which seals off the nasal passage
-epiglottis folds over closed glottis
-elevation of larynx and closure of vocal cords prevents food from entering trachea - the respiratory passage is sealed off

34

The esophagus contains:

contains two sphincters at each end
1) pharyngoesophageal sphincter:
-keeps entrance closed to prevent large volumes of air from entering esophagus and stomach during breathing
2) gastroesophageal sphincter:
-prevents reflux of gastic contents

35

What is the stomach?

A j-shaped chamber lying between the esophagus and small intestine that is divided into 3 sections

36

What are the three sections of the stomach and what they do?

1) Fundus
2) body: middle/main part of stomach
3) antrum: lower part of stomach

37

what are the three main functions of the stomach?

1) storage of food
2) secretes HCL and enzymes that begin protein digestion
3) mixing movements that convert pulverized food into chyme

38

What is the Plylonic sphincter?

serves as a barrier between the stomach and upper parrt of the small intestine

39

What are the four aspects of gastric motility?

1) filling
2) storage
3) mixing
4) emptying

40

What does "filling" in gastric motility involve?

-involves receptive relaxation which enhances the stomachs ability to accommodate the extra volume of food with little rise in stomach pressure
-triggers act of eating
-mediated by vagus nerve

41

what happens when too much food is consumed?

The stomach becomes overdistended and intragastric pressure rises along with discomfort

42

Where does storage in the stomach take place?

in the body

43

where does mixing in the stomach take place?

in the antrum

44

What is empyting largely controlled by?

factors in the duodenum

45

Factors in the stomach that regulate gastric emptying

- the amount of chyme in the stomach influences the strength of contractions

46

factors in the duodenum that regulates gastic emptying

1) fat
2)acid
3) hypertonicity
4) distension

47

where does digestion and absorption of fat take place?

within the lumen of the small intestine

48

is fat digestest faster or slower than other nutrients?

slower

49

When fat is already in the duodenum, what happens?

Further gastric emptying of additional fatty stomach contents id prevented until the small intestine has processed the fat that already exists there

50

what acid does the stomach secrete?

HCL, a highly acidic chyme

51

what does unneutralized acid int he duodenum do?

inhibits further emptying of acidic gastic contents until neutralization can be accomplished in the small intestine

52

How does hypotonicity (more water) influence gastic emptying?

-large amounts of water entering the intestine leads to disturbance
When osmolarity (more content) is high, gastric emptying is inhibited so that the content being digested can catch up

53

How does distention regulate gastric emptying?

- is too much chyme is in the duodenum, it inhibits emptying of further gastric contents so the duodenum can cope with the excess volume of chyme it already contains before it gets anymore

54

where in brain is vomiting controlled?

medulla of the brain stem

55

What is vomiting caused by?

1) deep inspiration
2) closure of glottis

56

what happens in body for vomiting to occur?

-contracting of diaphragm downwards on the stomach which squeezes it
-contraction of the abdominal cavity, which increases the intraabdominal pressure, the abdominal cavity is compressed from below
-Gastric contents are forced upward through relaxed sphincters and esophagus through the mouth

57

causes of vomiting

-tactile stimulation of back of throat (finger)
-distention or irritation of stomach
-rotation of acceleration of head
-chemicals agents
-emotional factors
-odors
-elevated intracranial pressure

58

Effects of vomiting:

-loss of fluid and acid
-reduction in plasma volume
-dehydration and circulatory problem

59

Advantages of vomiting

-removes toxic materials from stomach
-removes affending substances from body

60

three factors that trigger gastric motility

1) neural response
2) hormonal response
3)emotional response

61

How does the hormonal response trigger gastric motility

releases hormones such as secretion or CCK

62

how does sadness/fear affect gastric motility?

decreases it

63

how does anger or aggression affect gastric motility?

-increases it

64

how does intense pain affect gastric motility?

inhibits it

65

three types of gastric exocrine glands:

1) mucous cells
2) cheif cells
3) parietal (oxyntic) cells

66

what does mucous cells secrete?

thin, watery mucus

67

what do cheif cells secrete?

enzyme precursor: pepsinogen

68

what do parietal cells secrete?

HCL and intrinsic factor

69

what are the three phases gastric secretions?

1) cephalic phase
2) gastric phase
3) intestinal phase

70

What is the cephalic phase?

-refers to the increased secretion of HCL and pepsinogen that occurs in response to stimuli acting in the head before food reaches the stomach
-thinking, chewing, seeing food

71

What is the gastric phase?

begins when food reaches stomach
-presence of protein increases gastric secretions

72

what is the intestinal phase?

when the other phases are excitatory, the intestinal phase is inhibitory
helps shut off flow of gastric juices as chyme beings to empty into the small intestine

73

What is the pancreas and what are its endocrine and exocrine functions

- its a mixed gland that is located behind and below the stomach
Endocrine function is to secrete insulin and glucagon
Exocrine function is to secrete pancreatic juices that contain pancreatic enzymes

74

What are the three proteolytic enzymes?

1) trypsinogen
2) chymotrypisogen
3) procarboxypeptidase

75

What is pancreatic endocrine secretion regulated by?

secretin and CCK

76

what is trypsinogen converted to

active form of trypsin

77

what is chymotrypsiogen converted to

active form of chymotrysin

78

what is procarboxpeptidase converted to

active form of caboxpeptidase

79

what does pancreatic amylase do?

converts polysaccrides into the disacchoride

80

what is pancreatic lipase?

fat digesting enzyme secreted through entire digestive system

81

are the functions of the liver related to digestion?

No

82

what does the liver do?

-metabolically processes the major categories of nutrients
-detoxify body wastes, hormones, drugs, or foreign compounds
-synthesizes plasma proteins
-stores glycogen, fats, and vitamins
-removes bacteria and worn out RBCs
-Excretes cholesterol and bilirubin

83

What is bile actively secreted by?

the liver and is diverted to the gallbladder between meals

84

where is bile stored?

the gallbladder

85

Where does bile go after a meal?

it enters the duodenum

86

What is bile made up of?

bile salts
cholesterol
lecithin
bilirubin

87

What is bile salt important for?

the digestion and absorption of fats

88

where to bile salts go after participation in fat digestion/

the are reabsorbed back into the blood view active transport

89

what is enterhepatic ciriculation?

the recycling of bile salts

90

What is hepatisis?

the inflammation of the liver that can result in viral infections

91

what is cirrhosis?

Prolonged heptatic inflammation in association with chronic alcoholism

92

what does the submusca and myetric plexus complete?

regulation of gut activity

93

What happens to fat when to stomach contents are emptied into the duodenum?

the ingested fat is collected into a large oily triglyceride droplets that float in chyme
-in the small intenstine, these droplets are dispersed into small droplets so they are exposed to a greater surface area for digestion by pancreatic lipase

94

productions of lipid digestion?

triglycerides
(pancretic lipase)
monoglycerides and free fatty acids

95

What component can facilitate absorption of fatty end products?

micelles

96

what are micelles?

water soluable particles that can carry end products of fat digestion within their lipid soluable interiror

97

What facilitales fat digestion?

micelles
choesterol
lecitin
bile salts

98

Is Na absorbed passivley or acitvely?

both
Na passively enters the epithelial cells across the luminal border through Na+ channals or in the company of glucose or amino acids by using co-transport molecules

99

What does Na absportion depend on?

its electrochemical gradient from the lumen of the blood through the intestinal epitheal cells

100

how is water absorbed?

it is absorbed from the lumen into the villus according to the hydrostatic pressure and picked up by capillary networks

101

What is iron essential for?

haemoglobin production

102

what are the two processed of iron absorption?

1) absorption of iron from the lumen into the small intestine
2) absorption of iron from the epithieal cells into the blood

103

where does excess iron go?

its dumped into the ferritin pool, unused iron is lost in feces.

104

what are the three segments of the small intestine

1) duodenum
2) jejunum
3) ileum

105

motility of the small intestine includes:

1) segmentation
2) migrating motility complex

106

what is the mirgrating motility complex?

weak, repetative peristaltic waves that move a short distance down the intestine that sweeps intestines clean between meals

107

what is segmentation?

the primary method of motility in the small intestines
refers to mixing and propelling the chyme
consists of ringlike contractions that mix chyme

108

what is segmentation initiated by?

a pacemaker cell in the small intestine which produces basic eletrical rhythms (BER)
frequency of segmentation follows frequency of BER

109

What happens when the small intestine becomes stretched with chyme?

it initiates the intestine to begin localized contractions

110

what is circular smooth muscle responsivness influenced by?

distention of intestine and extensic nerve activity

111

what are the functions of segmentation?

1) mixing chyme with digestive juices secreted into small intestine lumen
2) exposing all chyme to absoptive surfaces of small intestine mucosa

112

small intestine secretion contains three enzymes:

1) enterokinase
2)disaccridase
3) amiopelidase

113

how is digestion in the small intestine accomplished?

its accomplsihed by pancreatic enzymes with fat digestion being enhanced by bile secretion

114

does juice secreted in small intestine contain any digestive enzymes

no

115

what are the membrane bound enzymes along the luminal surface?

they are brush -border membrane cells of the epitheal cells

116

what do the brush border enzymes do?

they continue carbohydrate and protein digestion

117

what are the adaptions that increase small intestines surface area?

-inner surface har circular folds
-microscopic finger like projections called villi
-brush-border

118

what does the large intestine consist of?

colon, cecum, appendix, booty hole

119

what is haustra?

pouches /sacs that actively change the location as result f contraction of circular smooth muscle
the contractions of the haustra are the main motility

120

what do mass movements do?

happen 3-4 times a day after each meal
moves colonic contents to distal end of the large intestine

121

what is the gastrocolic reflex?

mediated from stomach to colon by gastric and autonomic nerves
-most evident after first meal of the day, followed by urge to poo

122

What is the defecation reflex?

when a mass movement of the colon moves feces to the rectum, distention of rectum stimulates stretch receptors in the rectal wall

123

what pressures lead to defecation?

intra-abdominal pressure plus forcible expiration against a closed glottis

124

what causes constipation?

-feces that has stays in the colon for a longer period of time
-more h20 is absorbed
-causes by delayed pooping- longer than normal

125

symptoms of constipation?

abdomial discomfort
dull headache
loss of appetite
depression
nausea

126

what causes the appendix to become inflammed?

hardened feces in the appendix, results in pus and tissue will start to die

127

what are the four factors that affects the regulation of the digestive system?

1) autonomic smooth muscle function
2) intrisnic nerve plexus
3) extrisic nerve
4) gastrointestineal homrones

128

What does the exteric nerve plexus consist of?

1) myenteric plexus
2) submucus plexus

129

what does the myenteric plexus consist of?

contains many neurons that aid digestion and self regulation
contains both sensory and local neurons that are connected with interneurons

130

what three sensory receptors does the digestive system include

1) chemoreceptors
2) mechanoreceptors
3) osmoreceptors- sensitive to osmolarity

131

What does the long reflex involve?

involves pathways between CNS and digestive system

132

Short reflex

- all elements of the reflex are located within the wall of the GI tract
-coordinated by secretion in response to specific local stimulation

133

What does the neural and hormonal control of cephalic phase of the GI tract refer to?

refers to the increase of secretion of HCO and pepsiongen in response in head before food reaches the stomach

134

Food increases gastric secretion by stimuation of vagal nerve activity in two ways:

1) intrisic plexus
2) G-cells

135

What does the intrisic plexus do?

promotes increases ach secretion
stimulates secretion cells to secret more HCL and pepsionogen

136

What do G-cells do

release gastrin
secretes HCL and pepsiogen

137

what are the hormones that control gastrointestinal activites

1) gastrin
2)secretin
3) CCK
4) GIP

138

what causes gastrin release?

presence of proteinous foods in the stomach

139

what does gastrin do

-increases HCL and pepsinogen secretion, which promotes protein digestion
-enhances gastric motility
-induces mass movements in the colon

140

what causes secretin release?

presence of acid in the duodenum

141

what does secretin do

inhibits emptying to prevent acid from entering duodenum
stimulates pancreatic duct to produce a basic solution to neutralize acid

142

what causes CCK release?

presence of fat in duodenal muscosa

143

what does CCK do?

inhibits gastric motility, allowing more time for the nutrients to be digested and absorbed
-stimulates pancreatic enzmyes to be secreted
causes contraction of gall bladder and relaxation of sphichters of oddi to empty the bile into the duodenum

144

what does GIP do?

promotes metabolic processing of nutrients after their absorption
-stimulates insulin release by the pancreas
-promotes use and storage of newly arrived nutrients

145

what hormones act on the small intestine?

secretin and CCK

146

what does the pyloric gland area of the stomach antrum secrete?

gastrin

147

What does secretin stimulate?

the secretion of bicarbonate

148

what do micelles do?

aid fat digestion through micelle formation

149

what is the major stimulus for secretion of secretin?

entry of acid chyme into the small intestine