Digestive system intro and overview Flashcards
function of the digestive system
mechanical and chemical breakdown of food
Accessory digestive organs includes
salivary glands, liver, gallbladder, pancreas
liver producing bile in gall bladder helps with digesting ___ (detergent)
fat
pancreas producing juice with digestive enzymes can break down all nutrients. It also contains ____ which neutralizes the acid coming from the stomach into the duodenum
bicarbonate
___ ___ performs most of the work, and is the main site of digestion and absorption
small intestine
Four basic digestive process of the digestive system are:
motility
secretion
digestion
absorption
Digestion can be mechanical or chemical:
____ is accomplished by physical means, such as chewing, mushing, mixing, mashing action of digestive tubes
____ - Involves chemical operation of the food with the help of digestive enzyme and bile juices produced by the liver
mechanical
chemical
contractions of smooth muscle in the wall of the tube that crush, mix and propel its contents is called ____
Motility
delivery of enzymes, mucus, ions, water into the lumen, and (specialized endocrine cells) hormones into the blood is called ___
Secretion
food is broken down into smaller molecules suitable for absorption (chemical and mechanical). this process is called ___
digestion
the transport of water, ions and nutrients from the lumen, across the epithelium and into the blood is called
absorption
The digestive tract wall has four layers:
mucosa, submucosa, muscularis externa, serosa
The ___ layer covers the digestive tube, and provides a protective barrier
epithelial
inner most layer highly folded mucous membrane, exocrine, endocrine gland cells and epithelial cells specialized for absorption.
Mucosa
thick layer of connective tissue
gives digestive tube elasticity
Submucosa
inner circular and outer longitudinal smooth muscle layers
Muscularis externa
In the muscularis externa, when circular muscle contract we ___ the diameter of digestive tube, when longitudinal contracts, the digestive tube ____
decrease
shortens
Between the submucosa and muscularis externa theres a network of nerves called___ ____ – together the submucosal and the myenteric plexus make up the enteric (intrinsic) nervous system
myenteric plexuses
outer connective tissue, secretes serous fluid to lubricate and prevent friction
Serosa
secrete water slippery fluid in the digestive organ and surroundings to lubricate and prevent friction. Throughout the digestive tract, its continuous with mesentery which suspends the digestive tract organ from the abdominal wall
Serosa cells
True or false? The contents of the stomach lumen are outside the body
True
Substances inside the lumen of Digestive Tube are considered inside the body and are part of internal body environment only after they have been absorbed by the intestinal ____ cells
epithelial
Conditions essential for digestion can be tolerated ___ the body but not ___ the body within the bodies internal environment
outside
inside
existence of microbes in our colon, in lumen they are not harmful but beneficial, however, if bacteria gets in the internal environment, they become ___
harmful
Content of ___ in Digestive Tube are part of external environment and are outside body
lumen
Ist layer of cells which encounter any nutrients in digestive tube is the ____ layer, and are arranged in invaginations called ___ and finger-like projection called ___ —- this arrange helps increase absorptive surface area.
epithelial
crypt
vilus
Most epithelial are ___, tight junctions —essential for absorption of nutrients. It also provides the barrier that prevents harmful substance from getting in from the outside
columnar
Together, the absorption by the epithelial of nutrients and the barrier preventing harmful substance from entering is called “____ ____” — tight junction plays important role. Another important component is the ___ layer secreted by the specialized cells.
gastrointestinal barrier
mucus
Efficient transport of nutrients across the epithelium while passage of harmful molecules and organisms is rigorously excluded
gastrointestinal barrier
___ ___ also divide the membranes into two separate compartment with specific function (apical and basolateral membrane)
Tight junctions
The gastrointestinal epithelial is a ___ epithelia
polarized
Transport from the lumen to extracellular fluid (ECF) - ___. Transport from ECF to lumen - ___
absorption
secretion
___ epithelia have different transport proteins on apical and basolateral membranes allowing selective directional transport across the epithelium
Polarized
Epithelial cells arise from stem cells that are located at the base of ___ in the intestine and in the middle of gastric glands in the stomach. The cell travels from the crypt to the tip of the villus takes ~___ days
the lining of the digestive tube is completely replaced
crypts
3 days
we have the speciaized stem cells that constantly divide and diff and travel from bottom of the crypt to the tip of villus where they undergo cell death, or ___. They then shed into ____ to be replace by newly diff epithelial cells. — lining of the digestive tube is completely replaced
apoptosis
lumen
GIT its highly populated with macrophages, lymphoctyes etc, invloved in the ___ response.
immune
GIT is the ____ organ. The ____ tissue associated with the GIT is call the GUT-associated lymphoid tissue (GALT), which its said to contain as many lymphocytes as our spleen
lymphoid
lymphoid
GUT-associated lymphoid tissue (GALT)
the lymphocytes in our GIT are divided into three major population depending on location
Peyer’s Patches
Lamina propria lymphocytes
Intraepithelial lymphocytes
peyer’s patches are ____ follicals
lymphoid
peyer’s patch are ___ cells (M cells) on epithelial layer that sample different antigens from the lumen. Via endocytosis it engulfs them and transfers them to the macrophages and dendritic cells instead of digesting them. Macrophages and Dendritic cells present them to ___ and this results in appearance of plasma cells that secrete ___ into the lumen and help prevents the colonization of pathogens and bacteria in lumen. In addition the ___ cells they sample antigens in lumen
microfold
tcells
IgA
dendritic
In the post-prandial period (after a meal) blood is diverted from the skeletal muscles and other body systems. The blood volume in the GIT increases up to __ folds
5
Enteric nervous system consist of two neural plexus:
myenteric and submucosal plexus
The autonomic nervous branches controls the enteric nervous system (sympathetic and parasympathic nervous system), however some reflexes are integrated within the ENS not requiring ANS or CNS action at all, because the ENS can serve as its own information processing center. “consider GIT ___ ___”
little brain
The ____ plexus is mainly involved with control of gut motility
myenteric
The ___ plexus coordinates intestinal absorption and secretion
submucosal
What kind of adverse gastrointestinal effect will most likely develop as a result of prolonged treatment with anticholinergic drugs?
constipation
____ is the primary neurotransmitter involved in the stimulation of secretion and motility in GIT.
Acetylcholine
__ and __ function as inhibitory neurotransmitters.
ATP
NO
___ neurotransmitters, e.g. vasoactive intestinal polypeptide (VIP), stimulates intestinal fluid and electrolyte secretion but inhibits motility.
Peptide
___ is active in emergency situations. In general it decrease all aspect of digestive function.
___ dominates in quiet situations, when the digestion can reach its optimum, that is why it stimulates all aspect of the digestive function
Sympathetic
Parasympathetic
In the digestive tract wall, there are 3 types of receptors:
chemoreceptors
mechanoreceptor
osmoreceptors
___ are activated by various chemicals present in lumen, ____ are stimulated by the stretch and distension of the digestive wall , ___ stimulated by different osmolarity of the lumen content
chemoreceptors
mechanoreceptor
osmoreceptors
Stimulation of chemoreceptors, mechanoreceptor, &b osmo-receptors receptors can stimulate or inhibit the___ nervous system: the neurons of the submucosa plexus, myenteric plexus, change activity of autonomic nervous fibers and change secretion of gastrointestinal hormones.
intrinsic
All processes in digestive system are under physiological control under three types of mechanisms:
neural
endocrine
paracrine
involves regulation of the intrinsic nervous system, the submucosal nervous system, and myenteric plexus and by fibers of autonomic nervous system
Neural regulation
refers to the presence of highly specialized entero-endocrine cells that secrete various hormones into the blood circulation, and then the gastrointestinal hormones can reach the distant sites in the digestive tube and change their function
Endocrine regulation
There are more than 13 different hormones secreted in the GI tract; it is considered one of the largest ____ organ in our bodies
endocrine
Some agent and substances are not stable enough to persist in the blood circulation, instead when they are released they change the function of the neighboring cell– this is called the ___ ___
the paracrine regulation
A good example of paracrine regulation would be the release of ___ by the stomach cells, in which they stimulate the neighboring parietal cells in the stomach to secrete the gastric acid
histamine
the smooth muscle cells allow the digestive tube to perform two major patterns of motility:
propulsive movements
mixing movements
____ moves content so that the digest tube move forward.
Mixing movement have two purposes: 1st they have to mix the content with the digestive juices and they have digestion but also they have to expose all parts of the lumenal content to the absorptive surface of the small intestine so they also facilitate absorption
Propulsive movements
So the major type of the propulsive movements, which is seen particularly well in the esophagus and the small intestine is called ____
peristalsis
refers to the ring-like contraction of the circular smooth muscle cells that move progressively forward and push bolus in the relax area ahead of contraction
Peristalsis
segmental ringlike contractions with mixing movement that chop and mix the food
Segmentation
Electrical activity of smooth muscle cell in GIT activity is induced by pace-maker cells called interstitial cells of
Cajal
the __ junctions serve the main purpose of cell cell communication. In particular, the charged ions can freely pass, which means the electrical activity initiated by the pacemaker cells by the interstitial cells of cajal can be easily passed to the smooth muscle cells
gap
When partially digested food enter small intestine we have a stretch and distention of the intestinal wall which in turn activates the ____ within the gut wall
This causes release of excitatory neurotransmitters, which leads to membrane potential becoming more depolarized, followed by muscle contractions. The contraction moves around and along through the ___ junctions
If inhibitory neurons are released, the opposite will occur
mechanoreceptors
gap
Saliva is produces by three major salivary glands:
parotid glands, submandibular gland, and sublingual gland
The saliva help to start the digestion of complex carbohydrate bc it contains the enzyme called ___ ___
salivary amylase
the saliva is very important for oral hygiene bc it contains the ___ which helps kill the majority of microorganisms that enter the oral cavity
it also facilitates the movement of lips and tongue
lysozyme
Both parasympathetic and sympathetic induce salivary secretion, however the amount is very different. The ___ produces a lot more saliva, the ___ generates smaller volumes of viscous saliva which is reached in mucous.
parasympathetic
sympathetic
Food goes from the oral cavity (bolus) into the ___ (the throat). The throat/pharynx participates in the swallowing reflex. ___ can be voluntary, but once it is initiated it cannot be stopped.
pharynx
Swallowing
The ___ elevates closing the nasal passages, then the ___ is pushed down closing respiratory airways. With them closed, the pharyngeal muscles contract and pushes bolus into esophagus.
uvula
epiglottis
we don’t perform strong respiratory activity during swallowing bc the swallowing center in ___ of brain stem temporarily inhibits nearby ligated respiratory centers
medulla
Esophagus contains ___ muscle in addition to circular and longitudinal muscle like the rest of the digestive tract.
skeletal
___ ____ deals with skeletal muscle fatigue. One of the common symptoms is difficulty swallowing
Myasthenia gravis
The esophagus is guarded by sphincters on both ends, ____ sphincter and the ____ sphincter—- these sphincters are closed most off the time except during swallowing.
___ is closed to prevent large amount of air getting into the digestive tube and accumulation of gas. The ___ sphincter is always closed to prevent the high acidic gastric content from getting into the esophagus and damaging wall
pharyngoesophageal sphincter
gastroesophageal sphincter
pharyngoesophageal
gastroesophageal
The ___ nerve ending release acetylcholine which can act on the excitatory or inhibitory neurons of the myenteric plexus
vagus
The excitatory neurons of the myenteric plexus release mainly ___ and _____
substance P
acetylcholine
a neurotransmitter that modulates the pain perception. It also acts as an important peptide neurotransmitter in the digestive tract
SUB P
The inhibitory neurons of the myenteric plexus that release nitric oxide and vasoactive peptide causes smooth muscle ___.
relaxation
Acid from the stomach in the esophagus cause
GERDs
symptoms of GERDs
regurgitation, burning chest pain(heart burn)
Minor symptoms of GERDs are
dysphagia (difficulty swallowing), non-burning chest pain
Atypical extra-esophageal symptoms of GERDs include
sore throat, coughing, increased salivation shortness of breath
refers to the presence of inflammatory cells within the esophageal mucosa.
Esophagitis
major complications of GERDs
esophagitis
Esophageal stricture
Barret’s esophagus
– inflammation of esophageal wall and the presence of various types of pro-inflammatory and infiltration of immune cells in the esophageal epithelial
esophagitis
– where the lumen of the esophagus becomes abnormally narrow, due to the thickening of the esophageal wall – which happens bc of the persistant inflammatory process—- main cause is GERD, and is responsilbe of 70% of all cases
Esophageal stricture
esophageal stricture can interphere with the normal passages of food bolus across esophagus
and causes the ____ (difficulty swallowing)
dysphagia
Treated by dilation using endoscopically inserted balloons. Its also important to manage GERD in order to heal esophageal wall and prevent stricture from return again.
Esophageal stricture
The esophageal wall contains same epithelial as the oral cavity and skin called ___ epithelial
The stomach and rest of digestive tube are covered with ___ epithelium.
Between stomach and esophagus there’s a demarcation line called ____ columnar junction. The ___ epithelium appears whitish pink and the ___ appears reddish salmon pink.
squamous columnar squamous squamous columnar
The abnormal healing of the erosions where the normal squamous becomes columnar epithelium which is normally present in the stomach and father in the digestive tube
—–at higher risk 10X esophageal cancer
This is called
Barret’s esophagus
achalasia
Another disorder associated with the dysfunction of the lower esophageal sphincter
is translated as failure to relax. Theres a constant contract of the lower esophageal sphincter. If constantly closed the food cant pass normally in the esophagus to stomach.
achalasia
the main symptom of achalasia is
dysphagia
undigested food in the esophagus can result in pulmonary ___
aspiration
studies show that in achalasia patients there’s a degeneration loss of neurons of ___ plexus which regulate the contraction of smooth muscle lower esophageal sphincter
myenteric
the smooth muscle of the lower esophageal sphincter contains the presence of the myenteric plexus with excitatory neurons that release __ that stimulate smooth muscle contraction and inhibitory neuron which release ___, a major inhibitory neuron found in GI system
Ach
nitric oxide
measures the pressure as the swallowing proceeds, so it increases as we swallow, but then at the level of lower esophageal sphincter (LES), the pressure drops as the sphincter relaxes and opens to let the food into the stomach
manometry
Patients with Achalasia, theres a loss and degeneration mainly of the neurons that release inhibitory neuron transmitter ___. In this case the Lower Esophageal Sphincter fails to relax resulting in difficulty swallowing
nitric oxide
if there’s no presence of excitatory or inhibitory neurons due to major loss of mysenteric neurons, this leads to ___
dysphagia/diff swallowing
achalasia is managed with balloon, which is inserted with endoscope, allowing the sphincter to stay constantly open. This however results in ___. Because ___ is easily manageable with medications — it’s a reasonable tradeoff.
GERDs
GERDs
the injection on ___ __ has also been tested to treat achalasia.
botulin toxin
inhibits Ach release so without Ach the smooth muscle is not contracting so strong, allowing swallowing to proceed normally by relaxing the sphincter.
Botulin toxin
