Physiology 2

Front 1

difficulty swallowing =

Back 1

dysphagia

Front 2

The most obvious functions of the GI tract are to:
-separate ingested food into essential nutrients & unnecessary wastes
-absorb the former while getting rid of the latter

To successfully carry out these tasks, the GI tract has developed a number of elaborate mechanisms involving what four functions:

Back 2

motility
secretion
digestion
absorption

Front 3

Smooth muscle in the walls of the GI tract maintains a constant low level of contractions known as

Back 3

tone or bowel sounds

Front 4

Superimposed on ongoing tone are 3 basic types of motility:

Back 4

1) propulsive or peristalis
2) mixing movements or segmentation
two fold function
-promote mechanical digestion
-facilitate absorption by exposing all portions of intestinal contents to absorbing surfaces of GI tract
3) tonic contractions of sphincters or valves

Front 5

Smooth muscles are responsible for GI movements with two exceptions where motility involves skeletal muscle:

Back 5

the mouth through the early portion of the esophagus

the external anal sphincter

Front 6

Secretion in the GI tract involves the diverse processes by which water, electrolytes and proteins are exported out of cells. It is remarkable for both its magnitude and diversity. In a typical day, the human body makes over:

Back 6

1.5 L saliva
2.5 L gastric juice
0.5 L bile
1.5 L pancreatic juice
1.0 L intestinal secretions
2.0 L mucus

Front 7

A disorder where secretions from the SI are far in excess of the absorptive capacity of the colon, resulting in life-thretening diarrhea and dehydration.

Back 7

cholera

Front 8

The breakdown process whereby the structurally complex foodstuffs of the diet are converted into smaller absorbable units:
Occurs ___________ via motility and _________ via enzymes.

Back 8

digestion, mechanically, chemically

Front 9

The breaking up of large molecules of carbohydrate, lipid and protein into their components.

Back 9

hydrolysis

Front 10

Insertion of H+ and OH- ions derived from water. The underlying mechanism of most chemical digestion.

Back 10

hydrolysis

Front 11

Many of the enzymes are secreted into the GI tract lumen from places like the stomach and pancreas, whereas others are part of the plasma membrane of ________ (brush border enzymes), the epithelial cells that make up the mucosal surface of the GI tract.

Back 11

enterocytes

Front 12

The accessory digestive organs include the:

Back 12

-salivary glands
-pancreas
-biliary system (liver & gall bladder)

Front 13

Below the diaphragm, the GI organs reside in the _________ cavity, the largest of the ventral body cavities.

Back 13

abdominopelvic

Front 14

The slick serous membrane of the abdominopelvic cavity:

Back 14

peritoneum

Front 15

The ___________ covers the external surfaces of most digestive organs and is continuous with the ____________ that lines the walls of the abdominopelvic cavity.

Back 15

visceral peritoneum
parietal peritoneum

Front 16

Between the two peritoneums is the _____________, a slit-like space containing peritoneal fluid secreted by the two membranes.

Back 16

peritoneal cavity

Front 17

Inflammation of the peritoneum, may occur when one suffers a piercing wound of the abdomen, a perforating ulcer, or a ruptured appendix.

Back 17

peritonitis

Front 18

A condition characterized by the accumulation of peritoneal fluid.

Back 18

Ascites

Front 19

Peritoneal fold that binds SI to posterior abdominal wall:

Back 19

mesentery

Front 20

Peritoneal fold that binds the large intestine to the posterior abdominal wall.

Back 20

mesocolon

Front 21

Peritoneal fold that attaches the liver to the anterior wall and diaphragm.

Back 21

falciform ligament

Front 22

Peritoneal fold that hangs loosely from the transverse colon and SI.

Back 22

greater omentum

Front 23

Peritoneal fold that suspends the stomach and duodenum from the liver.

Back 23

lesser omentum

Front 24

This peritoneal fold contains considerable adipose tissue and lymph nodes and contributes macrophages and anti-body producing plasma cells that help combat an infection of the GI tract and prevent an infection from spreading:

Back 24

greater omentum

Front 25

When HCl or gastric juice penetrates the gastric mucosal barrier, injuring the gastric wall with its acidic and enzymatic contents.

Back 25

peptic ulcer disease
(PUD)

Front 26

Occurs when pancreatic juice escapes the pancreas and/or duodenum. The pancreatic digestive enzymes in the juice can cause widespread destruction of pancreatic tissue and possible hemorrhage.

Back 26

acute pancreatitis

Front 27

The pathogenesis of acute pancreatitis usually involves active secretion of pancreatic juice while the ____________ is obstructed at its entrance into the duodenum. The build-up of obstructed secretions greatly increases the pressure within the duct system, causing the ducts to rupture and the pancreatic juice to escape.

Back 27

main pancreatic duct

Front 28

In the case of a _________________, the colon wall tears open, allowing intestinal bacteria ("flora") to escape to the abdominal and pelvic cavities, causing peritonitis or even death.

Back 28

ruptured appendix or perforated diverticulitis

Front 29

Contents: stomach (gastritis), pancreas (acute pancreatitis) spleen, majority of the heart, lower left lung

Back 29

LUQ

Front 30

liver (acute hepatitis), gall bladder (acute cholecystitis), duodenum (duodenal ulcer), pancreas (acute pancreatitis)

heart, lower right lung

Back 30

RUQ

Front 31

Contains descending & sigmoid colon (diverticulosis)

Back 31

LLQ

Front 32

Contains appendix (appendicitis)

Back 32

RLQ

Front 33

The innermost layer of the GI tract in contact with the contents of the lumen.

Back 33

mucosa

Front 34

This serves as a protective surface as well as being modified in particular areas for secretion and absorption. What layer of the GI tract is this in?

Back 34

mucous membrane, mucosa

Front 35

Mucouse membranes (mucosa layer of GI tract) contain _______ cells for secretion of digestive juices, __________ cells for secretion of GI hormones and ________ cells specialized for absorbing digestive nutrients.

Back 35

exocrine, endocrine, epithelial

Front 36

A thick layer of connective tissue that supports the mucose structurally and provides the GI tract with its distensibility and elasticity.

Back 36

submucosa

Front 37

Contained within the submucosa is a collection of neurons called the:

Back 37

submucosal (Meissner's) plexus

Front 38

Major smooth muscle coat of the GI tract:

Back 38

muscularis externa

Front 39

The muscularis externa, in most parts of the tract, consists of what two layers?

Back 39

inner circular layer and outer longitudinal layer

Front 40

Between the circular muscle layer and the longitudinal muscle layer of the muscularis externa is a group of neurons known as the

Back 40

myenteric (Aurbach's) plexus

Front 41

Outer connective covering of the GI tract.

Back 41

Serosa (Visceral peritoneum)

Front 42

Secretes watery serous fluid that lubricates and prevents friction between the digestive organs and the surrounding viscera

Back 42

serosa (visceral peritoneum)

Front 43

One cause of hernias is __________ tearing.

Back 43

mesenteric

Front 44

Some smooth muscle cells are "pacemaker" cells that display rhythmic, spontaneous variations in membrane potential.
The prominent type of self-induced electrical activity in digestive smooth muscle is called _______________, alternatively referred to as the GI tract's ________________(BER) or pacemaker potential

Back 44

slow-wave potential, basal electrical rhythm (BER)

Front 45

These two plexuxes are often termed the intrinsic nerve plexuses or the enteric nervous system (ENS).
Some are sensory neurons, which possess receptors that respond to specific local stimuli (e.g. - pain) in the GI tract
Others are motor neurons that innervate smooth muscle cells, exocrine cells & endocrine cells of the GI tract to directly affect GI tract motility, secretion of digestive juices, and secretion of GI hormones

Back 45

submucosal plexus and myenteric plexuse

Front 46

The neurons of the submucosal and myenteric plexuses are often termed the intrinsic nerve plexuses or ______________________.

Back 46

the enteric nervous system (ENS)

Front 47

These nerves originate outside the GI tract and innervate the various GI organs -- namely, nerve fibers from both branches of the autonomic nervous system.

Autonomic nerves influence GI tract motility and secretion either by
-modifying ongoing activity in the enteric nervous system
-manipulating BER (basal electrical rhythm)
-altering the level of GI hormone secretion
-acting directly on smooth muscle and glands

Back 47

Extrinsic nerves

Front 48

GI (Gut) Hormones
The mucosa of certain regions of the GI tract contain ______ cells that secrete hormones
GI hormones are carried through blood to other areas of the GI tract, where they exert either _________ or _______ influences on smooth muscle and exocrine cells.

Back 48

endocrine, excitatory, inhibitory

Front 49

Salivary gland secretions aid in lubrication and digestion of food, and enhance speech, taste and swallowing. Moreover, patients who cannot produce saliva (a rare condition known as ___________) suffer from dental caries (cavities), dry mouth and inflammation of the buccal mucosa.

Back 49

xerostomia

Front 50

The principal glands of salivation are the _______, __________, _________ glands; in addition, there are many small _________ glands. The daily secretion of saliva normally ranges between 800 - 1500 ml.

Back 50

parotid, submandibular, sublingual, buccal

Front 51

Saliva is composed of about 99.5% water and 0.5% _________ and _______.

Back 51

electrolytes, protein

Front 52

An enzyme that begins digestion of carbohydrates in the mouth:

Back 52

salivary amylase

Front 53

Part of saliva that mixes with water to become mucus, which lubricates food.

Back 53

mucin

Front 54

Antibodies in saliva that provide the first immunologic defense against bacteria and viruses.

Back 54

IgA

Front 55

Found in saliva; attacks the bacteria in the saliva

Back 55

lysozyme

Front 56

Found in saliva; protects tooth enamel.

Back 56

proline-rich proteins

Front 57

This exists in the mouth, but is inactive and it is an enzyme that begins digestion of lipids in the stomach.

Back 57

lingual lipase

Front 58

Salivary secretion is under ______ control. The continuous, spontaneous secretion of saliva, even in the absence of apparent stimuli, is due to constant low-level stimulation by the _______________ nerve endings that terminate in the salivary glands. This basal secretion is important in keeping the mouth and pharynx moist at all times.

Back 58

neural, parasympathetic

Front 59

An unconditioned ___________ occurs when chemoreceptors and pressure receptors within the oral cavity respond to the presence of food. On activation, these receptors initiate impulses in ______ nerve fibers that carry the information to the salivary center of the _______. The salivary center sends impulses via the extrinsic autonomic nerves (VII and IX) to the salivary glands to promote increased salivation.

Back 59

salivary reflex, afferent, medulla

Front 60

The SNS and PNS responses in the salivary glands are not _______________.

Back 60

antagonistic

Front 61

Both SNS and PNS stimulation increase salivary secretion. ___________, which exerts the dominant role in salivary secretion, produces a prompt and abundant flow of watery saliva that is rich in enzymes. ______________ stimulation, on the other hand, produces a much smaller volume of thick saliva that is rich in mucus.

Back 61

parasympathetic nervous system, SNS

Front 62

__________ and other _____________ blocking agents reduce salivary secretion.

Back 62

atropine, cholinergic blocking agents

Front 63

Swallowing = _____________, is a reflex response that is triggered by afferent impulses in CNs ___________(3 of them). These impulses are integrated in the _______ of the brainstem.

Back 63

deglutition, V, IX, X, medulla

5,9,10

Front 64

The efferent fibers that pass to the pharyngeal musculature and the tongue during swallowing (_________) are CNs ____________(6 of them)

Back 64

deglutition, V, VII, IX, X, XII

5,7,9,10,12

Front 65

Swallowing consists of what three phases:

Back 65

1) oral or voluntary phase
--swallowing is initiated by the voluntary action of collecting the oral contents on the tongue and propelling them backward to the pharynx (oral phase).
2) pharyngeal phase
--This starts a wave of involuntary contraction in the pharyngeal muscles that pushes the material into the esophagus, as the upper esophageal sphincter (UES) relaxes and opens (pharyngeal phase).
3) esophageal phase
--Once food enters the esophagus, peristalsis takes over (esophageal phase).
--Inhibition of respiration and stimulation of glottic closure are part of the reflex response. Also, the material tilts the epiglottis backward and down over the closed glottis as further protection from food entering the respiratory airways. Swallowing is difficult if not impossible when the mouth is open, as anyone who has spent time in the dentist's chair feeling saliva collect in the throat is aware.

Front 66

A polymicrobial lung infection that results from inhaling food or secretions. This common consequence of failure to properly coordinate breathing and swallowing is due to impaired oropharyngeal motility. Proper positioning of these patients is crucial.

Back 66

aspiration pneumonia

Front 67

__________involves a progressive wave of ring-like smooth contractions that propels food down to the ______________ (LES). Once triggered by swallowing, esophageal peristalsis will occur whether or not food is present, although the presence of food will ______ the peristaltic contractions. If the primary peristaltic wave fails to move food into the stomach, the persistence of the food bolus in the esophagus will set off secondary peristaltic waves to complete the job.

Back 67

esophageal peristalsis, lower esophageal sphincter, intensify

Front 68

The LES, like most sphincters, is tonically contracted. However, this tonic contraction can be influenced either to relax (thereby opening the LES) or to contract further. In a condition called ___________, the LES fails to relax; food that has been swallowed has difficulty passing into the stomach, and the esophagus above the LES becomes enlarged. One or several meals may lodge in the esophagus and pass slowly into the stomach over time. There is danger of aspiration of esophageal contents into the lungs when the person lies down.

Back 68

achalasia

Front 69

Various agents have been showed to decrease LES pressure, which in turn, decreases it's closing strength. This permits reflux of acidic gastric contents into the esophagus ____________. This common condition causes heartburn and __________ and can lead to ulceration and stricture of the esophagus due to scarring. Furthermore, current research indicates that there may a strong causal relationship between GERD and esophageal ____________.

Back 69

GERD (gastroesophageal reflux disease), esophagitis, adenocarcinoma

Front 70

Complications can result from persistent reflux, producing a cycle of mucosal damage that causes edema and erosion of the luminal surface. These complications include strictures and a condition called ____________ esophagus.

Back 70

Barrett's

Front 71

_________ are caused by a combination of scar tissue, spasm and edema. They produce narrowing of the esophagus and cause dysphagia when the lumen becomes sufficiently constricted.

Back 71

Strictures

Front 72

____________ is characterized by a repair process in which the squamous mucosa that normally lines the esophagus is gradually replaced by columnar epithelium (________) resembling that in the stomach and intestines. It, too, is associated with increased risk of developing esophageal cancer.

Back 72

Barrett's esophagus, metaplasia