GI Flashcards
What are the main functions of the GIT?
Nutrition
Excretion
Microbiome
Electrolyte balance
Immunity
What is the definition of motility?
Motility describes the contraction of the muscles that mix and propel contents in the gastrointestinal (GI) tract.
What are the two main excretory products?
Carbon dioxide and Urea.
GI motor activity can be divided into two sections. What are the two sections? and explain their individual role.
Functional activity: segmentation, peristalsis and storage
Contractile activity: phasic (alternative contractions – said to be rhythmic) and tonic (sustained)
Why is contractile activity referred as highly coordinate and regulated? / What controls the relaxation and contraction of the GI tract?
Segmentation and peristalsis
What coordinates the movement of food from the stomach to the small intestines?
pyloric sphincter
Outline the differences between peristalsis and segmentation.
Segmentation is another kind of involuntary muscle movement that occurs in your digestive system. But unlike peristalsis, which occurs throughout your GI tract (especially oesophagus), segmentation occurs mainly in your intestines.
What is gastric motility?
Gastrointestinal (GI) motility refers to the movement of food from the mouth through the pharynx (throat), esophagus, stomach, small and large intestines and out of the body
Explain why the stomach withholds a specific amount of gastric content.
To reduce pressure and allow hormones to mix
Describe the motility patterns for gastric emptying and explain how gastric emptying is regulated.
Stomach stage
When food is chewed and swallowed, the mushed-up food travels down the oesophagus and into the stomach, where it sits for a while. The stomach then releases gastric acid and an enzyme called pepsin to start the process of digestion, turning the mush into a semi-digested acidic liquid called chyme.
The stomach has four parts. The upper part is called the fundus (food is stored here temporarily). Next is the body of the stomach. The lower part of the stomach is called the antrum - mixing occurs here and the end of the stomach is called the pylorus (contracts to limit chyme from stomach). The pyloric sphincter sits at the bottom end of the pylorus where it connects to the first part of the small intestine, called the duodenum. This sphincter is like a valve that opens slightly (about 3.75 mm) and periodically squirts small bits of chyme into the duodenum. When chyme goes into the duodenum, the muscle becomes distended, and this triggers the enterogastric reflex. When this reflex happens, the pyloric sphincter takes a temporary pause. No more gastric acid is secreted, no more chyme is released into the duodenum, and gastric motility is halted until the duodenum has digested the chyme and is ready to receive more. A functioning pyloric sphincter is important for proper digestion. If the sphincter is diseased and does not open and close properly, it may lead to problems with digestion and nutrient absorption.
Small intestine
But just how is the chyme digested? The contraction of intestinal circular smooth muscles that mixes chyme is called segmentation. The small intestine is the site where segmentation occurs. Segmentation plays a large part in both digestion and nutrient absorption and begins once chyme is dumped into the duodenum (beginning of the small intestine). However, these muscle contractions do not transport partially digested food through the intestines but rather mechanically mix them in one place.
What is peristalsis?
Peristalsis is a type of involuntary muscle movement that occurs in your digestive system. Peristalsis occurs throughout your GI tract, but especially in your esophagus. When food or fluids enter your GI tract, nerves trigger the muscles to initiate a series of wave-like contractions. These muscle contractions automatically move food and fluids forward until they reach their exit at your anus or urethra.
What are the three main controls of gut motility movement?
Myogenic control: Intrinsic rhythm of GI smooth muscles set by pacemakers cells of ICC. RHYTHM IS USUALLY SLOW WAVES
Hormonal control: Utilizes various hormones including cholecystokinin, gastrin, and secretin, among multiple others for a myriad of functions
Neuronal control: The gastrointestinal (GI) tract is controlled both intrinsically by the enteric nervous system (ENS) – known as the “brain of the gut” is pivotal for normal muscle activity in the gut and is independent of the CNS, and extrinsically by visceral sensory afferent and visceral motor efferent (sympathetic and parasympathetic) fibers.
Where is the ENS located?
Within the GI Tissue inside the:
myenteric plexus (controls motility)
submucosal plexus (controls secretory functions)
Explain the process of how myogenic muscles regulate their movement?
Hormonal and neuronal activity determines whether slow waves reach their threshold and cause an action potential. These action potential leads to smooth muscle contraction.
What are the pacemakers of the gut called?
Interstitial Cells of Cajal (ICC) generates slow waves that may lead to contraction.
