Lecture 7 : Gastrointestinal System I : Overview, Ingestion, and Swallowing Flashcards
1
Q
Organs of the digestive system include two groups :
A
the alimentary canal & accessory digestive organs
2
Q
Digestive System =
A
Gastrointestinal System =“Gut”
3
Q
Alimentary Canal =
A
Gastrointestinal tract = GI tract = Gut tube
4
Q
Inside the tube (lumen) is outside the body – food passes through the _______ organs during digestive activity.
A
alimentary canal
5
Q
________ provide chewing, enzymes and buffers that assist in mechanical and chemical breakdown of food.
A
Accessory organs
6
Q
Six (6) essential digestive functions and processes :
A
Ingestion
Propulsion
Mechanical breakdown
Digestion
Absorption
Defecation
7
Q
Ingestion
A
taking in food and water via the mouth
8
Q
Propulsion
A
movement of food/water by swallowing (voluntary) or peristalsis (alternating waves of contraction of smooth muscle)
9
Q
Mechanical breakdown
A
increases surface area of food, preparing for chemical digestion by enzymes:
In mouth: chewing, tongue mix food with saliva
Churning: pummeling of food in stomach
Segmentation: back and forth movement in SI
10
Q
Digestion
A
enzymes secreted into lumen break food into chemical building blocks (catabolic process)
11
Q
Absorption
A
movement of nutrients from lumen to blood or lymph
12
Q
Defecation
A
elimination of solid waste (feces): indigestible substances and metabolic wastes
13
Q
endocrine & exocrine ____ will aid in digestive processes
A
gland secretions
14
Q
GI _____ moves food in an _____ direction and facilitates mixing
A
Motility
aboral
15
Q
Aboral =
A
from mouth to anus
16
Q
Motility (movement) due to smooth muscle layers of the muscularis externa
Two types of movement:
A
- Peristalsis:
mostly propulsive (forward movement) - Segmentation:
mostly for mixing and mechanical breakdown
17
Q
The _____ is the Serous Membrane in the Abdominal Cavity
A
Peritoneum
18
Q
Peritoneum:
A
slippery, continuous serous membrane sac
19
Q
_______ – lines the inner surface of the body wall
A
Parietal peritoneum
20
Q
_________ - lines the surface of digestive organs
A
Visceral peritoneum
21
Q
___________– fluid filled potential space between the peritoneal layers (sterile space)
A
Peritoneal cavity
22
Q
_____ organs are surrounded or suspended by peritoneum
A
Intraperitoneal
23
Q
_______ lie posterior to peritoneum
A
Retroperitoneal organs
24
Q
Most digestive organs are intraperitoneal and are suspended from the body wall by a _____
A
dorsal mesentery
25
some intraperitoneal digestive organs are also suspended from the wall by _____
ventral mesenteries
26
some digestive organs are _____ because they have lost their mesentery during development
retroperitoneal
27
______ are folds of peritoneum that suspend organs in abdomen
Mesenteries
28
Abdominal cavity is completely lined by _____
parietal peritoneum
29
______ is sterile space with slippery fluid
Peritoneal cavity
30
Functions of Mesenteries
Provide routes for blood vessels, lymphatics and nerves to reach the abdominal viscera
Hold the organs in place – highly organized
Store fat
Create channels and spaces in which infections can travel
>Endometriosis
> ovarian cancer
31
_______ attach to the stomach
Greater and Lesser Omentum
32
The Mesentery
Small intestine
Mesocolon for parts of large intestine (colon)
33
The alimentary canal (GI tract) wall has four (4) layers
(Innermost) : Mucosa
Submucosa
Muscularis Externa
Adventitia/Serosa
34
Mucosa
innermost layer of the alimentary canal
35
Mucosa (has 3 layers)
Epithelium – usually simple columnar; rich in mucous secreting cells
Lamina propria – loose areolar connective tissue with lymphoid follicles (MALT)
Muscularis mucosa – thin smooth muscle layer
36
Functions of Mucosa:
Secrete mucus, digestive enzymes and hormones
Absorb the end products of digestion into the blood
Protect against infectious disease this is the protective barrier of the alimentary canal
37
Submucosa :
Connective tissue between mucosa and muscularis externa
Areolar connective tissue with blood vessels, lymphatic vessels, lymphoid follicles, nerve fibers, glands; location of submucosal plexus
38
Muscularis Externa :
Major smooth muscle layer of the alimentary canal
39
Muscularis Externa (2 layers)
Inner circular smooth muscle
Outer longitudinal smooth muscle
stomach has 3 layers
40
Muscularis Externa
Function:
Segmentation & peristalsis
Churning actions of stomach
41
Muscularis Externa
Other facts:
myenteric nerve plexus between muscle layers
Inner circular smooth muscle can contribute to sphincters
42
Outermost layer :
Serosa or Adventitia
43
Serosa (visceral peritoneum)
Areolar connective tissue with mesothelium (simple epithelium
44
Adventitia (if no peritoneum)
Dense connective tissue
45
Digestive system activities are controlled by the __________
nervous and endocrine systems
46
Enteric nervous system (ENS)
consists of neurons wall of the gut which are involved in local reflexes
47
Nerves of the sympathetic and parasympathetic nervous systems innervate the _____
enteric neurons of the digestive tract (involved in long reflexes).
48
Autonomic nerves also carry sensory feedback from _____
GI organs to CNS.
49
The ANS, ENS and GI hormones control GI organs and _______ of the digestive system
coordinate motility and secretions
50
______ resides in wall of GI tract
Enteric Nervous System
51
Enteric Nervous System =
“Third Division” of ANS
consists of Intrinsic Nerve Plexuses (ganglia plus networks of nerves)
52
Myenteric Plexus :
Between layers in muscularis externa
53
Submucosal Plexus :
In submucosa layer
54
Enteric Nervous System Controls local _____ reflexes
gut
55
Enteric nervous system (ENS)
Neurons arranged in ____ within wall of GI tract
ganglia
56
Ganglia and axons form intrinsic nerve plexuses:
submucosal plexus and myenteric plexus
57
Respond to stimuli within GI tract – mediate _____ that regulate digestive system activity
short reflexes
58
Pacemaker cells:
Interstitial cells of Cajal
modified smooth muscle cells that act like pacemakers
Intermediary between intrinsic nerve plexus and smooth muscle
59
_______ control GI smooth muscle and glands
Short reflexes (ENS), Long reflexes (ANS) and hormones
60
_____ reflexes promote digestive system activity:
Long and short
Motility : muscle contraction
Secretion of digestive juices or hormones
61
Stimuli: Digestive activity is provoked by range of mechanical and chemical stimuli
stretch of wall by food in lumen
changes in osmolarity (solute concentration)
pH of contents and end products of digestion
CNS regulation of GI activity in response to sights, smells, thoughts, anxiety, fear
62
Effectors : digestive activity is affected by the action of smooth muscle and glands.
stimulate smooth muscle in walls of GI tract to increase motility (mixing and propulsion)
activate or inhibit glands that secrete digestive juices into lumen or hormones into blood
63
Digestive activity is controlled by:
intrinsic nervous controls (short reflexes within ENS)
extrinsic nervous controls (long reflexes via ANS)
64
Enteroendocrine cells :
hormone producing cells within the gut wall
release their hormones into interstitial fluid in extracellular space
enter the blood and are distributed to target cells in the same organ or different organs where they affect secretion or contraction
65
Autonomic Nerves travel to GI tract in ____
Mesenteries
66
Blood supply through 3 branches of :
abdominal aorta
67
Parasympathetic innervation through:
vagus nerve and sacral spinal levels
68
Sympathetic innervation from :
thoracic levels
69
The oral cavity performs :
ingestion, mechanical breakdown, digestion and propulsion
70
Epithelium of the Oral Cavity:
Stratified squamous epithelium (wear and tear)
71
Tonsils :
Palatine and lingual tonsils provide immune defense
72
____________ involved in mastication and manipulation of food.
Teeth, tongue and hard palate
73
___________ block nasopharynx during swallowing
Soft palate and uvula
74
_____ contain skeletal muscles to control muscles of palate and pharynx.
“Arches”
75
The tongue aids in:
chewing, initiates swallowing and aids in speech
76
Tongue:
Interlacing bundles of skeletal muscle
Mix food with saliva to produce a bolus
Articulation: form sounds during speech
Taste buds located on sides of papillae; contain taste cells
77
Salivary glands secrete saliva which is delivered to ____ through ducts
oral cavity
78
Why Saliva?
Cleanse the mouth (prevent tooth decay)
Dissolve food chemicals – taste
Moistens food to help compact the bolus
Begin digestion of starch by enzyme amylase
79
What is Saliva?
Mostly water – 97 to 99%
Electrolytes
Digestive enzymes (amylase & lipase)
Proteins mucin, lysozyme, and IgA
Metabolic wastes
80
____ input increases salivation (watery, enzyme rich)
Parasympathetic
81
_____ input decreases salivation: stimulate mucous secretion (dry mouth), constrict blood vessels
Sympathetic
82
Salivary output ______
1.5 Liters per day or more
83
The Pharynx provides a common pathway for :
food, fluids and air
84
Mucosa of the Oropharynx & Laryngopharynx contains ______ (continuous with the oral cavity)
stratified squamous epithelium
85
______ contains skeletal muscle
Longitudinal and circular layers
Muscularis externa
86
The pharynx is involved in propulsion of food:
swallowing – a voluntary activity that also has some involuntary aspects (coordination).
87
The Esophagus propels food from the laryngopharynx to the :
stomach
88
Mucosa of esophagus contains ____________ (continuous with the oral cavity)
non-keratinized stratified squamous epithelium
Transition to simple columnar near stomach
89
_____ contains esophageal glands (mucus-secreting for lubrication)
Submucosa
90
Muscularis externa contains _____ in the upper third, _____ in middle third,________ in inferior third – role in peristalsis – propel food to stomach
skeletal muscle
skeletal/smooth
smooth muscle
91
Adventitia –
dense CT, no serous layer
92
esophagus lies posterior to the ____
trachea
93
______ blocks the opening of the larynx to divert food into the esophagus
epiglottis
94
There is a ____ at each end of the esophagus
sphincter
95
Upper esophageal sphincter –
skeletal muscle
prevents passage of air into esophagus while breathing
96
Lower esophageal sphincter (LES)-
(also called gastroesophageal sphincter)
smooth muscle
prevents reflux of stomach contents into esophagus – thickening of smooth muscle that is reinforced by diaphragm
97
Issues of lower esophageal sphincter :
GERD
Achalasia
98
GERD =
Gastroesophageal reflux disease – acid reflux from stomach inflames epithelium and esophagus wall
99
Achalasia –
difficulty opening LES sphincter, or weakness of peristalsis – failure of myenteric plexus coordination?
100
_____ = Swallowing
Deglutition
We swallow 600 times per day!
101
Dysphagia
difficulty swallowing
Can be due to nervous system or muscular system issue
102
Oral phase: voluntary
Tongue pushes bolus back
Sensory receptors in pharynx initiate next phase
103
Swallowing : Pharyngeal-Esophageal phase
Nasopharynx blocked by soft palate
Larynx rises, epiglottis blocks airway
Coordinated by brainstem centers and cranial nerves
104
(Propulsion of food into Esophagus)
Continuation of pharyngeal-esophageal phase (involuntary):
Pharyngeal constrictor muscles push food into upper esophagus
Peristalsis will take over in esophagus
105
Propulsion through Esophagus: Peristalsis
Alternating waves of muscle push food through esophagus – peristalsis
Muscle transition : Upper 1/3 esophagus is skeletal muscle, Middle 1/3 is skeletal + smooth mixed, Lower 1/3 is smooth
