Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

2 - Keiser A&P 2 > 0-1 Chapter 25 - digestive system > Flashcards

0-1 Chapter 25 - digestive system Flashcards

1
Q

gastroenterology

A

the study of the digestive tract and the diagnosis and treatment of its disorders

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

digestive system

A

the organ system that processes food, extracts nutrients from it, and eliminates the residue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

five stages of digestion

A 
ingestion
digestion
absorption-
compaction
defecation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

ingestion

A

selective intake of food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

digestion

A

mechanical and chemical breakdown of food into a form usable by the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

absorption-

A

uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

compaction

A

absorbing water and consolidating the indigestible residue into feces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

defecation

A

elimination of feces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

mechanical digestion

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 the action of digestive enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

chemical digestion

A

aseries 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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

results:

A
  • polysaccharides into monosaccharides
  • proteins into amino acids
  • fats into monoglycerides and fatty acids
  • nucleic acids into nucleotides
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

some nutrients are present in a usable form in ingested food

A

–absorbed without being digested

–vitamins, free amino acids, minerals, cholesterol, and water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

digestive system has two anatomical subdivisions

A

digestive tract

gastrointestinal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

digestive tract

A

(alimentary canal)
–30 foot long muscular tube extending from mouth to anus
–mouth, pharynx, esophagus, stomach, small intestine, and large intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

gastrointestinal (GI) tract

A

is the stomach and intestines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

accessory organs

A

teeth, tongue, salivary glands, liver, gallbladder, and pancreas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

General Anatomy

A

•digestive tract is open to the environment at both ends
•most material in it has not entered the body tissues
–is considered to be external to the body until it is absorbed by the epithelial cells of the alimentary canal
•in a strict sense, defecated food residue was never in the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

basis structural plan

A

most of the digestive tract follows the basis structural plan with digestive tract wall consisting of the following tissue layers, in order from inner to outer surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

basis structural plan

order

A 
•mucosa
–epithelium
–lamina propria
–muscularis mucosae
•submucosa
•muscularis externa
–inner circular layer
–outer longitudinal layer
•serosa
–areolar tissue
–mesothelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

mucosa

A

(mucous membrane) –lines the lumen and consists of:
–inner epithelium
–lamina propria –
–muscularis mucosa
–mucosa-associated lymphatic tissue (MALT) –

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

inner epithelium

A
  • simple columnar in most of digestive tract

* stratified squamous from mouth through esophagus, and in lower anal canal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

lamina propria

A

loose connective tissue layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

muscularis mucosa

A

thin layer of smooth muscle
•tenses mucosa creating grooves and ridges that enhance surface area and contact with food
•improves efficiency of digestion and nutrient absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

mucosa-associated lymphatic tissue (MALT)

A

the mucosa exhibits an abundance of lymphocytes and lymphatic nodules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

submucosa

A

thicker layer of loose connective tissue
–contains blood vessels, lymphatic vessels, a nerve plexus, and in some places mucus secreting glands that dump lubricating mucus into the lumen
–MALT extends into the submucosa in some parts of the GI tract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

muscularis externa

A

consists of usually two layers of muscle near the outer surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

inner circular layer

A

•in some places, this layer thickens to form valves (sphincters) that regulate the passage of material through the tract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

outer longitudinal layer

A

•responsible for the motility that propels food and residue through the tract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

serosa

A

composed of a thin layer of areolar tissue topped by simple squamous mesothelium
–begins in the lower 3 to 4 cm of the esophagus
–ends just before the rectum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

adventitia

A

a fibrous connective tissue layer that binds and blends the pharynx, most of the esophagus, and the rectum into the adjacent connective tissue of other organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

enteric nervous system

A

a nervous network in the esophagus, stomach, and intestines that regulated digestive tract motility, secretion, and blood flow
–thought to have over 100 million neurons
–more than the spinal cord
–functions completely independently of the central nervous system
•CNS exerts a significant influence on its action

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

composed of two networks of neurons

A

submucosal (Meissner) plexus

myenteric (Auerbach) plexus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

submucosal (Meissner) plexus

A

in submucosa
•controls glandular secretion of mucosa
•controls movements of muscularis mucosae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

myenteric (Auerbach) plexus

A

parasympathetic ganglia and nerve fibers between the two layers of the muscularis externa
•controls peristalsis and other contractions of muscularis externa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

enteric nervous system contains sensory neurons that

A

monitor tension in gut wall and conditions in lumen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

mesenteries

A

connective tissue sheets that loosely suspend the stomach and intestines from the abdominal wall
–allows stomach and intestines to undergo strenuous contractions
–allow freedom of movement in the abdominal cavity
–hold abdominal viscera in proper relationship to each other
–prevents the intestines from becoming twisted and tangled by changes in body position and by its own contractions
–provides passage of blood vessels and nerves that supply digestive tract
–contain many lymph nodes and lymphatic vessels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

parietal peritoneum

A

a serous membrane that lines the wall of the abdominal cavity
–turns inward along posterior midline
–forms dorsal mesentery –a translucent two-layered membrane extending to the digestive tract
–the two layers of the mesentery separate and pass around opposite sides of the organ forming the serosa
–come together on the far side of the organ and continue as another sheet of tissue –the ventral mesentery
•may hang freely in the abdominal cavity
•may attach to the anterior abdominal wall or other organs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

lesser omentum

A

a ventral mesentery that extends from the lesser curvature of the stomach to theliver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

greater omentum

A

hangs from the greater curvature of the stomach
–covers the small intestines like an apron
–the inferior margin turns back on itself and passes upward
–forming a deep pouch between its deep and superficial layers
–inner superior margin forms serous membranes around the spleen and transverse colon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

mesocolon

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

intraperitoneal

A

when an organ is enclosed by mesentery on both sides
–considered within the peritoneal cavity
–stomach, liver, and other parts of small and large intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

retroperitoneal

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

motility and secretion of the digestive tract are controlled by

A

neural, hormonal, and paracrine mechanisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

neural control

A

short (myenteric) reflexes

long (vagovagal) reflexes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

short (myenteric) reflexes

A

stretch or chemical stimulation acts through myenteric plexus
•stimulates peristaltic contractions of swallowing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

long (vagovagal) reflexes

A

parasympathetic stimulation of digestive motility and secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

hormones

A

–chemical messengers secreted into bloodstream, and stimulate distant parts of the digestive tract
–gastrin and secretin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

paracrine secretions

A

–chemical messengers that diffuse through the tissue fluids to stimulate nearby target cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

The Mouth

A

the mouth is known as the oral, or buccal cavity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

functions include:

A

–ingestion (food intake)
–other sensory responses to food –chewing and chemical digestion
–swallowing, speech, and respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

mouth enclosed by

A

cheeks, lips, palate, and tongue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

oral fissure

A

anterior opening between lips

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

fauces

A

posterior opening to the throat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

stratified squamous epithelium

A

lines mouth
–keratinized in areas subject to food abrasion –gums and hard palate
–nonkeratinizedin other areas –floor of mouth, soft palate, and inside of cheek and lips

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

cheeks and lips

A

–retain food and push it between the teeth for chewing
–essential for articulate speech
–essential for sucking and blowing actions, including suckling by infants
–fleshiness due to subcutaneous fat, buccinator muscle of the cheek, and the orbicularis oris of the lips

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

labial frenulum

A

median fold that attaches each lip to the gum between the anterior incisors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

vestibule

A

the space between cheek or lips and the teeth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

lips divided into three areas:

A

cutaneous area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

cutaneous area

A

colored like the rest of the face

•has hair follicles and sebaceous glands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

red (vermillion) area

A

hairless region where lips meet
•tall dermal papilla that allows blood vessels and nerves to come closer to epidermal surface
•redder and more sensitive than cutaneous area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

labial mucosa

A

the inner surface of the lips facing the gums and teeth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

tongue

A

muscular, bulky, but remarkably agile and sensitive organ
–manipulates food between teeth while it avoids being bitten
–can extract food particles from the teeth after a meal
–sensitive enough to feel a stray hair in a bite of food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

nonkeratinized stratified squamous epithelium covers

A

its surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

lingual papillae

A

bumps and projections on the tongue that are the sites of the taste buds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

body

A

anterior two-thirds of the tongue occupies oral cavity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

root

A

posterior one-third of the tongue occupies the oropharynx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

vallate papillae

A

a V-shaped row of papillae that mark the boundary between the body and root of the tongue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

terminal sulcus

A

groove behind the V-shaped vallate papillae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

lingual frenulum

A

median fold that attaches the body to the floor of the mouth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

intrinsic muscles

A

are contained entirely within the tongue

•produce the subtle tongue movements of speech

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

extrinsic muscles

A

with origins elsewhere and insertions in the tongue
•produce stronger movements of food manipulation
•genioglossus, hyoglossus, palatoglossus, and styloglossus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

lingual glands

A

serous and mucous glands amid the extrinsic muscles

•secrete a portion of the saliva

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

lingual tonsils

A

contained in the root

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

palate

A

separates the oral cavity from the nasal cavity

–makes it possible to breathe while chewing food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

hard (bony) palate

A

anterior portion that is supported by the palatine processes of the maxillaeand the palatinebones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

palatine rugae

A

transverse ridges that help the tongue hold and manipulate food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

soft palate

A

posterior with a more spongy texture
–composed of skeletal muscle and glandular tissue
–no bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

uvula

A

conical medial projection visible at the rear of the mouth

–helps retain food in the mouth until one is ready to swallow

79
Q

pair of muscular arches on each side of the oral cavity

A

–palatoglossal arch –anterior arch
–palatopharyngeal arch –posterior arch
–palatine tonsils are located on the wall between the arches

80
Q

dentition

A

the teeth

81
Q

masticate food into smaller pieces

A

–makes food easier to swallow

–exposes more surface area for action of digestive enzymes speeding chemical digestion

82
Q

32 adult teeth –20 deciduous (baby) teeth

A

–16 in mandible

–16 in maxilla

83
Q

from midline to the rear of each jaw

A
  • 2 incisors–chisel-like cutting teeth used to bite off a piece of food
  • 1 canine–pointed and act to puncture and shred food
  • 2premolars –broad surface for crushing and grinding
  • 3 molars–even broader surface for crushing and grinding
84
Q

alveolus

A

tooth socket in bone

85
Q

gomphosis joint

A

between tooth and bone

86
Q

periodontal ligament

A

modified periosteum whose collagen fibers penetrate into the bone on one side and into the tooth on the other
–anchors tooth firmly in alveolus
–allows slight movement under pressure of chewing

87
Q

gingiva (gum)

A

covers the alveolar bone

88
Q

regions of a tooth

A

crown
root
neck
gingival sulcus

89
Q

crown

A

portion above the gum

90
Q

root

A

the portion below the gum, embedded in alveolar bone

91
Q

neck

A

the point where crown, root, and gum meet

92
Q

gingival sulcus

A

space between the tooth and the gum

•hygiene in the sulcus in important to dental health

93
Q

dentin

A

hard yellowish tissue that makes up most of the tooth

94
Q

enamel

A

covers crown and neck

95
Q

cementum

A

covers root
•cementum and dentin are living tissue and can regenerate
•enamel is noncellular secretion formed during development

96
Q

root canal

A

in the roots leading to pulp cavity in the crown

–nerves and blood vessels

97
Q

apical foramen

A

pore at the basal end of each root canal

98
Q

occlusion

A

meeting of the teeth with the mouth closed

99
Q

Deciduous Teeth

A

20 deciduous teeth (milk teeth or baby teeth)
•teeth develop beneath the gums and erupt in a predictable order
–erupt from 6 to 30 months
–beginning with incisors
–between 6 and 32 years of age, are replaced by 32 permanent teeth

100
Q

(wisdom teeth

A 
third molars (wisdom teeth) erupt from 17 –25
–may be impacted–crowded against neighboring teeth and bone so they cannot erupt
101
Q

Tooth and Gum Disease

A

the human mouth is home to more than 700 species of microorganisms, especially bacteria

102
Q

plaque

A

sticky residue on the teeth made up of bacteria and sugars
–calculus –calcified plaque
–bacteria metabolize sugars and release acids that dissolve the minerals of enamel and dentin to form dental caries (cavities

103
Q

root canal therapy

A

is necessary if cavity reaches pulp

104
Q

calculus

A

in the gingival sulcus wedges the tooth and gum apart
–allows bacterial invasion of the sulcus
–gingivitis–inflammation of the gums
–periodontal disease –destruction of the supporting bone around the teeth which may result in tooth loss

105
Q

mastication(chewing)

A

breaks food into smaller pieces to be swallowed and exposes more surface to the action of digestive enzymes

106
Q

mastication

process

A

–first step in mechanical digestion
–food stimulates oral receptors that trigger an involuntary chewing reflex
–tongue, buccinator, and orbicularis oris manipulate food
–masseter and temporalis elevate the teeth to crush food
–medial and lateral pterygoids, and masseter swing teeth in side-to-side grinding action of molars

107
Q

saliva

A

–moisten mouth
–begin starch and fat digestion
–cleanse teeth
–inhibit bacterial growth
–dissolves molecules so they can stimulate the taste buds
–moistens food and binds it together into bolus to aid in swallowing

108
Q

Saliva

contents

A

hypotonic solution of 97.0% to 99.5% water and the following solutes:
–salivary amylase –enzyme that begins starch digestion in the mouth
–lingual lipase –enzyme that is activated by stomach acid and digests fat after the food is swallowed
–mucus–binds and lubricates the 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

109
Q

saliva

ph

A

pH of 6.8 to 7.0

110
Q

intrinsic salivary glands

A

small glands dispersed amid other oral tissues
–lingual glands –in the tongue –produce lingual lipase
–labial glands –inside of the lips
–buccal glands –inside of the cheek
–all secrete saliva at a fairly constant rate

111
Q

extrinsic salivary glands

A

three pairs connected to oral cavity by ducts
–parotid
–submandibular gland
–sublingual glands –

112
Q

parotid

A

–located beneath the skin anterior to the earlobe

•mumps is an inflammation and swelling of the parotid gland caused by a virus

113
Q

submandibular gland

A

–located halfway along the body of the mandible

•its duct empties at the side of the lingual frenulum, near the lower central incisors

114
Q

sublingual glands

A

–located in the floor of the mouth

•has multiple ducts that empty posterior to the papilla of the submandibular duct

115
Q

Histology of Salivary Glands

A

•compound tubuloacinar glands
–branched ducts ending in acini
•mucous cells secrete mucus
•serous cells secrete thin fluid rich in amylase and electrolytes
•mixed acinus has both mucous and serous cells

116
Q

Salivation

A

extrinsic salivary glands secrete about of 1 to 1.5 L of saliva per day

117
Q

cells of acini

A

filter water and electrolytes from blood and add amylase, mucin, and lysozyme

118
Q

salivary nuclei

A

in the medulla oblongata and pons respond to signals generated by presence of food
–tactile, pressure, and taste receptors
–salivary nuclei receive input from higher brain centers as well
•odor, sight, thought of food stimulates salivation
–send signals by way of autonomic fibers in the facial and glossopharyngeal nerves to the glands

119
Q

parasympathetics

A

stimulate the glands to produce an abundance of thin, enzyme-rich saliva

120
Q

sympathetic stimulation

A

stimulates the glands to produce less, and thicker saliva with more mucus

121
Q

bolus

A

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

122
Q

pharynx

A

a muscular funnel that connects oral cavity to esophagus and allows entrance of air from nasal cavity to larynx
–digestive and respiratory tracts intersect

123
Q

pharyngeal constrictors

A

(superior, middle, and inferior) -circular muscles that force food downward during swallowing
–when not swallowing, the inferior constrictor remains contracted to exclude air from the esophagus
–this constriction is considered to be the upper esophageal sphincter although it is not an anatomical feature
–disappears at the time of death when the muscles relax, so it is a physiological sphincter, not an anatomical structure

124
Q

esophagus

A

a straight muscular tube 25-30 cm long
–begins at level between C6 and the cricoid cartilage
–extends from pharynx to cardiac orifice of stomach passing through esophageal hiatus in diaphragm

125
Q

lower esophageal sphincter

A

food pauses at this point because of this constriction
•prevents stomach contents from regurgitating into the esophagus
•protects esophageal mucosa from erosive effect of the stomach acid

126
Q

heartburn

A

burning sensation produced by acid reflux into the esophagus

127
Q

esophagus

tissue type

A

–nonkeratinized stratified squamous epithelium
–esophageal glands in submucosa secrete mucus
–deeply folded into longitudinal ridges when empty
–skeletal muscle in upper one-third, mixture in middle one-third, and only smooth muscle in the bottom one-third
–meets stomach at level of T7
–covered with adventitia

128
Q

swallowing

A

(deglutition) –a complex action involving over 22 muscles in the mouth, pharynx, and esophagus

129
Q

swallowing center

A

pair of nuclei in medulla oblongata that coordinates swallowing
•communicates with muscles of the pharynx and esophagus by way of trigeminal, facial, glossopharyngeal, and hypoglossal nerves

130
Q

swallowing occurs in two phases:

A

buccal phase

pharyngoesophageal phase

131
Q

buccal phase

A

under voluntary control
•tongue collects food, presses it against the palate forming a bolus, and pushes it posteriorly
•food accumulates in oropharynx in front of the „blade‟ of the epiglottis
•epiglottis tips posteriorly and food bolus slides around it
•bolus enters laryngopharynx and stimulates tactile receptors and activates next phase

132
Q

pharyngoesophageal phase

A

•three actions prevent food and drink from reentering the mouth or entering the nasal cavity or larynx
–the root of the tongue blocks the oral cavity
–the soft palate rises and blocks the nasopharynx
–the infrahyoid muscles pull the larynx up to meet the epiglottis while laryngeal folds close the airway
•food bolus is driven downward by constriction of the upper, then middle, and finally the lower pharyngeal constrictors
•bolus enters esophagus, stretches it, and stimulates peristalsi

133
Q

peristalsis

A

wave of muscular contraction that pushes the bolus ahead of it
–an entirely involuntary reflex

134
Q

stomach

A

a muscular sac in upper left abdominal cavity immediately inferior to the diaphragm
–primarily functions as a food storage organ
•internal volume of about 50 mL when empty
•1.0 –1.5 L after a typical meal
•up to 4 L when extremely full and extend nearly as far as the pelvis

135
Q

stomach

function

A

mechanically breaks up food particles, liquefies the food, and begins chemical digestion of protein and fat
–chyme –soupy or pasty mixture of semi-digested food in the stomach
•most digestion occurs after the chyme passes on to the small intestine

136
Q

chyme

A

soupy or pasty mixture of semi-digested food in the stomach

137
Q

stomach

divided into four regions

A 
cardiac region (cardia)
fundic region (fundus
body (corpus)
138
Q

cardiac region (cardia)

A

small area within about 3 cm of the cardiac orifice

139
Q

fundic region (fundus

A

dome-shaped portion superior to esophageal attachment

140
Q

body (corpus)

A

makes up the greatest part of the stomach

141
Q

pyloric region

A

narrower pouch at the inferior end
–subdivided into the funnel-like antrum
–and narrower pyloric canal that terminates at pylorus
–pylorus –narrow passage to duodenum

142
Q

pyloric (gastroduodenal) sphincter

A

regulates the passage of chyme into the duodenum

143
Q

stomach receives:

–parasympathetic fibers from

A

vagus

144
Q

stomach receives:

sympathetic fibers from

A

celiac ganglia

145
Q

supplied with blood by branches of the

A

celiac trunk

146
Q

all blood drained from stomach and intestines enters

A

hepatic portal circulation and is filtered through liver before returning to heart

147
Q

stomach

simple columnar epithelium covers

A

mucosa
–apical regions of its surface cells are filled with mucin
–swells with water and becomes mucusafter it is secreted

148
Q

gastric rugae

A

mucosa and submucosa flat when stomach is full, but form longitudinal wrinkles called gastric rugae when empty

149
Q

muscularis externa

A

has three layers instead of two

•outer longitudinal, middle circular and inner oblique layers

150
Q

gastric pits

A

depressions in gastric mucosa
–lined with simple columnar epithelium
–two or three tubular glands open into the bottom of each gastric pit

151
Q

cardiac glands

A

in cardiac region

152
Q

pyloric glands

A

in pyloric regions

153
Q

gastric glands

A

in the rest of the stomach

154
Q

Cells of Gastric Glands

A

mucous cells

155
Q

mucous cells

A

secrete mucus
–predominate in cardiac and pyloric glands
–in gastric glands, called mucous neck cells since they are concentrated at the neck of the gland

156
Q

regenerative (stem) cells

A

found in the base of the pit and in the neck of the gland

–divide rapidly and produce a continual supply of new cells to replace cells that die

157
Q

parietal cells

A

found mostly in the upper half of the gland

–secrete hydrochloric acid (HCl), intrinsic factor, and a hunger hormone called ghrelin

158
Q

chief cells

A

most numerous
–secrete gastric lipase and pepsinogen
–dominate lower half of gastric glands
–absent in pyloric and cardiac glands

159
Q

enteroendocrine cells

A

concentrated in lower end of gland

–secrete hormones and paracrine messengers that regulate digestion

160
Q

gastric juice

A

2 –3 liters per day produced by the gastric glands

•mainly a mixture of water, hydrochloric acid, and pepsin

161
Q

gastric juice has a high concentration of

A

hydrochloric acid

–pH as low as 0.8

162
Q

parietal cells produce

A

HCl and contain carbonic anhydrase (CAH)

163
Q

Functions of Hydrochloric Acid

A

•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

164
Q

zymogens

A

digestive enzymes secreted as inactive proteins

–converted to active enzymes by removing some of their amino acids

165
Q

pepsinogen

A

zymogen secreted by the chief cells
–hydrochloric acid removes some of its amino acids and forms pepsin that digests proteins
–autocatalytic effect –as some pepsin is formed, it converts more pepsinogen into pepsin

166
Q

pepsin digests dietary proteins into

A

shorter peptide chains

–protein digestion is completed in the small intestine

167
Q

gastric lipase

A

produced by chief cells
•gastric lipase and lingual lipase play a minor role in digesting dietary fats
–digests 10% -15% of dietary fats in the stomach
–rest digested in the small intestine

168
Q

intrinsic factor

A

a glycoprotein secreted by parietal cells
•essential to absorption of vitamin B12 by the small intestine
–binds vitamin B12 and intestinal cells absorb this complex by receptor-mediated endocytosis

169
Q

vitamin B12 is needed to

A

synthesize hemoglobin

–prevents pernicious anemia

170
Q

indispensable function of the stomach

A

secretion of intrinsic factor is the only indispensable function of the stomach
–digestion can continue if stomach is removed (gastrectomy), but B12supplements will be needed

171
Q

Chemical Messengers

A

gastric and pyloric glands have various kinds of enteroendocrine cells that produce as many as 20 chemical messengers
–some are hormones enter blood and stimulate distant cells
–others are paracrine secretions that stimulate neighboring cells
–several are peptides produced in both the digestive tract and the central nervous system –gut-brain peptides

172
Q

Gastric Motility

A

swallowing center of medulla oblongata signals stomach to relax
•food stretches stomach activating a receptive-relaxation response
–resists stretching briefly, but relaxes to hold more food
•soon stomach shows a rhythm of peristaltic contractions controlled by pacemaker cells in longitudinal layer of muscularis externa

173
Q

allowing only a small amount into the duodenum enables the duodenum to:

A
  • neutralize the stomach acid

* digest nutrients little by little

174
Q

vomiting

A

the forceful ejection of stomach and intestinal contents (chyme) from the mouth

175
Q

emetic center

A

in the medulla oblongata integrates multiple muscle actions

176
Q

vomiting is usually preceded by

A

nausea and retching

177
Q

retching

A

thoracic expansion and abdominal contraction creates a pressure difference that dilates the esophagus

178
Q

vomiting –occurs when

A

abdominal contractions and rising thoracic pressure force the upper esophageal sphincter to open
–esophagus and body of the stomach relax
–chyme is driven out of the stomach and mouth by strong abdominal contractionscombined with reverse peristalsis of gastric antrum and duodenum

179
Q

projectile vomiting

A

sudden vomiting with no prior nausea or retching

–common in infants after feeding

180
Q

chronic vomiting causes:

A

dangerous fluid, electrolyte, and acid-base imbalances

181
Q

bulimia–

A

eating disorder in which the tooth enamel becomes eroded by the hydrochloric acid in the chyme

182
Q

most digestion and nearly all absorption occur after

A

the chyme has passed into the small intestine

•stomach does not absorb any significant amount of nutrients

183
Q

alcoholis absorbed mainly by

A

small intestine

–intoxicating effects depends partly on how rapidly the stomach is emptied

184
Q

living stomach is protected in three ways from the harsh acidic and enzymatic environment it creates

A

–mucous coat –
–tight junctions -
–epithelial cell replacement
•breakdown of these protective measures can result in inflammation and peptic ulcer

185
Q

mucous coat

A

thick, highly alkaline mucus resists action of acid and enzymes

186
Q

tight junctions

A

between epithelial cells prevent gastric juice from seeping between them and digesting the connective tissue of the lamina propria and beyond

187
Q

epithelial cell replacement

A

stomach epithelial cells live only 3 to 6 days
•sloughed off into the chyme and digested with the food
•replaced rapidly by cell division in the gastric pits

188
Q

gastritis

A

inflammation of the stomach can lead to a peptic ulceras pepsin and hydrochloric acid erode the stomach wall
•most ulcers are caused by acid-resistant bacteria, Helicobacter pylori that can be treated with antibiotics and Pepto-Bismol

189
Q

Regulation of Gastric Function

A

nervous and endocrine systems collaborate

190
Q

gastric activity is divided into three phases:

A

cephalic phase
gastric phase
intestinal phase
•phases overlap and can occur simultaneously

191
Q

cephalic phase

A

stomach being controlled by brain

192
Q

gastric phase

A

stomach controlling itself

193
Q

intestinal phase

A

stomach being controlled by small

2 - Keiser A&P 2 (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions