Flashcards in Ward Gastric Physiology of digestion Deck (87):
(blank) are secreted from the mouth to the terminal regions of the intestine.
(blank) is secreted throughout the GI tract by glands to provide lubrication and protection of the epithelial lining.
What are the two primary types of secretion?
What are the four types of glands associated with secretion?
single cell mucous glands
crypts of Leberkuhn
Salivary glands, pancreas and liver
What is this:
(mucous cells/goblet cells) Are located in the epithelium and are found in most parts of the GI tract and respond to local stimulation of the epithelium by extruding their mucus onto the epithelial surface to act as a lubricant and to protect the epithelial surface.
Single cell mucous glands
What is this:
These are in the small intestine and are invaginations of epithelium into the submucosa. These are usually deep and contain specialized secretory cells.
Crypts of Leiberkuhn
What is this:
Located in the stomach and upper duodenum are large numbers of deep tubular glands which often secrete acid and pepsinogen.
What is this:
More complex glands with a primary function to provide secretions for digestion and emulsification of food. Two of these glands are compound acinus (containing many acinar cells) glands that lie outside the wall of the GI tract and are connected via ducts that empty into the GI tract itself.
Salivary glands, pancreas and liver
The (blank) and (blank) are compound acinus (containing many acinar cells) glands that lie outside the wall of the GI tract and are connected via ducts that empty into the GI tract itself.
salivary and pancreatic glands
Transportation of nutrient material needed for the formation of the secretory material must diffuse or be transported into the base of the glandular cell from (blank)
Synthesis of the secretory substance occurs in the (blank) and (blank)
ER and golgi complex
The secretory substance is transported through the ER, passing into the (blank)
In the golgi, secretory substances are modified, concentrated and discharged into the cytoplasm in the form of (blank)
Secretory vesicles are normally stored in the (blank) ends of the cell until (blank) cause them to empty their contents through the cell's surface.
neural or hormonal signals
The mechanism by which the secretory vesicle fuses to the plasma membrane (exocytosis) is usually (blank) dependent.
The neural or hormonal substance causes an increase in (blank), which leads to a fusion of the secretory vesicle with the apical membrane.
Sufficient water and electrolytes need to be secreted along with (blank).
Nerve stimulation has a specific effect on the (blank) portion of the cell membrane, causing (blank) transport of (blank) ions into the cell.
When you have nerve stimulation that causes active tranport of Cl- into the cell you have a resultant (blank) charge inside the cell which causes (blank) to move into the cell.
When nerve stimulation causes Cl- to enter the cell and as a result, Na+ into the cell, the excess of both these ions inside the cell creates a (blank) condition within the cell and a force that does what?
OSMOTIC force -> pulls water into the cell increasing the hydrostatic pressure
The increase in hydrostatic pressure resulting from nerve stimulation and the subsequent increase in Na+ and Cl- ions into the cell causes (blank) of the secretory border. Release of water through these openings results in the flushing of (blank) and (blank) out of the apical end of the cell and into the lumen of the gland
electrolytes and organic substances
The increase in hydrostatic pressure resulting from nerve stimulation and the subsequent increase in Na+ and Cl- ions into the cell causes minute rupturing of the secretory border. Release of water through these openings results in the flushing of electrolytes and organic substances out of the (blank) end of the cell and into the lumen of the gland
The presence of (blank) in a particular segment of the GI tract causes glands, in that region and often in adjacent regions to secrete digestive juices.
What are the two types of local stimulation of the GI tract glands?
direct contact-> of food with glands
epithelial stimulation-> neural activity causes secretion
What kind of GI stimulation is this:
activates the autonomic nervous system via tactile, chemical and distension mechanisms. The increase in neural activity causes mucus glands and deeper glands in the mucosa to increase secretion.
Epithelial stimulation of GI tract glands
What is the parasympathetic stimulation of secretion?
increase rate of glandular secretion
-> upper portion of GI tract (Vagus)
->distal portion of large intestine (Pelvic Parasympathetics)
What are the components of the upper GI tract that the parasympathetics increase stimulation of secretion in? What are these innervated by?
brunner's glands in
Innervated by the vagus!
What parasympathetics innervate the distal portion of the large intestine?
the pelvic parasympathetics
Secretion in the remainder of the small and large intestine not innervated by parasympathetics is controlled how?
by local neural and hormonal stimuli in each segment of the gut
What is the sympathetic stimulation of secretion?
causes slight/moderate increase in secretion
constriction of blood vessels
When will sympathetic stimulation cause an increase in secretion?
if parasympathetic nerve stimulation of salivary glands is low. If parasympathetic stimulation of salivary glands is high,then sympathetic stimulation will result in a reduction in secretion.
Summarize the hormonal stimulation of secretion:
GI hormones (polypeptides) from stomach and intestines are liberated from mucosa in response to food. They are absorbed into circulatory system and carried to particular gland to stimulate secretion
What is saliva necessary for and what is it dependent on?
Speech and mucus
What are the 6 constituents of saliva?
binding glycoprotein for IgA
(blank) an enzyme for digesting starches.
ph of saliva is optimal for this
(blank) Chelates iron and inhibits the growth of organisms that require it for growth.
(blank) attack bacterial cell walls
proteolytic enzymes (lyzozomes)
(blank) With IgA forms secretory IgA that is immunologically active against viruses and bacteria.
Binding glycoprotein for IgA
What is Composed of electrolytes, glycoproteins and water. Composition varies in the GI tract, but is an excellent lubricant and protectant.
(blank) properties of mucus allow it to tightly bind to food and spread a thin film over the surface of particles.
What are the functions of mucus
binds to food
acts as a barrier to mucosa
binds fecal material
can buffer (amphoteric properties)
(blank) allows for the easy passage of food along the GI tract and also prevents abrasions or chemical damage to the epithelium.
What are the three majory salivary glands and what are they all drained by?
parotid, sublingual, submandibular
a single major excretory duct
What is a minor salivary gland consisting of many single packages and are polystomatic.
In (blank) glands, sexual dimorphosism often exists
(Blank) lie outside the wall of the GI tract and are connected via ducts that empty into the GI tract itself.
(blank) are involved with directing fluids into the oral cavity.
(blank) are contractile and are involved in helping move serous and mucous secretions into ducts.
(blank) are Secretions of ptyalin (-amylase) and/or mucin from acinar cells in a solution of ions similar to that found in extracellular fluid.
Explain the intracellular mechanism for the movement of ions in salivary glands
Na+ ions are reabsorbed, K+ ions are secreted. This leads to a membrane potential of -70mV. This allows for passive reabsorption of Cl- ions. Cl- and Na+ ions are now at a low level in the ducts. Ca ions and bicarb are secreted by the ductal epithelial by an exchange of bicarb for chloride (actively)
What is the net result o the intracellular movements of ions in the duct?
Na+ and Cl- ions are low (10% of plasma)
K+ ions are higher
Bicarb ions are higher
During (blank) of the salivary glands, Na+ and Cl- ion concentration approaches levels found in plasma. In the presence of excess (blank) secretion, Na+ and Cl- ion absoprtion and K+ ion secretion is greatly increased!
Conditioned reflexes, smell, taste, pressure, and nausea do what to the salivary nucleus of the medulla?
Fatigue, sleep, fear, and dehydration do what to the salivary nucleus of the medulla?
What is the primary regulator of the salivary glands?
What parasympathetic nerves stimulate the release of aCH thus increasing salivary secretion, vasodilation, myoepithelial contraction, metabolism and growth?
CN IX and X
What sympathetics effect secretion and through which ganglion?
T1-3 through the superior cervical ganglion
(blank) nerve stimulation to the salivary glands begins and maintains salivary secretion.
Increased secretion is enhanced by (blank) which are also innervated by the parasympathetic system.
Myoepithelial cell contractions,
Increased cellular activity in response to parasympathetic stimulation causes a release of (blank) resulting in the production of (blank) potent vasodilator) and also growth of the salivary glands.
(blank) is Associated with chronic ulcerations of the buccal mucosa and with dental caries.
xerostomia (dry mouth)
(blank) is the absence of saliva
(blank) is the Atrophy of the glands and decreased saliva production. In cystic fibrosis, salivary sodium, calcium and protein are elevated. Digitalis drugs cause increased calcium and potassium concentrations in saliva.
(blank) is when sodium concentrations are increased.
(blank) can create Excessive salivation
tumors or parkinsons's disease
(blank) activity aids digestion.
gastric motor activity
What are four constituents of gastric juice that have physiologic functions?
What is required for the absorption of vitamin B12 by the ileal mucosa (released from parietal cells)
What is necessary for the conversion of pepsinogen to pepsin. Also kills bacterial
What, along with acid, begins to breakdown protein and is released from chief cells
What protects the mucosa lining of the stomach, lubricates and neutralizes a small amount of acid (released from goblet/mucus cells)
What are the 2 gland areas of the gastric mucous?
oxyntic and pyloric
What does this:
secretes acid, pepsinogen, mucus and intrinsic factor and is located on the proximal 80% of the stomach.
oxyntic gland area
What does this:
The distal 20% (antrum) synthesizes and secretes the hormone gastrin and mucus.
pyloric gland area
The line of demarcation between the oxyntic and pyloric gland mucosa is in the region of the (blank) on the lesser curvature.
incisura or angulus
The (blank) lie deep in the stomach wall and receive a rich blood supply and autonomic innervation.
(blank) Contain the acid-producing parietal cells and the peptic or chief cells, which secrete the enzyme precursor pepsinogen.
(blank) are Present where the glands open into the pits. These cells divide and the daughter cells migrate to the surface where they become mature mucous cells and down into the glands where they become parietal cells in the oxyntic gland area or G cells in the region of the pyloric gland mucosa.
mucous neck cells
(blank) are capable of mitosis, but they can also arise from mucus neck cells during the repair of damage to the mucosa.
To generate the massive concentration of H ions brought to us by the 3 billion parietal cells that secrete HCL at a conc. of 150-160 mMolar, how many calories/L of gastric juice is required?
Between meals the cytoplasm of the parietal cell is dominated by numerous (blank) and intracellular (blank) that is continuous with the lumen of the oxyntic gland. During acid secretion, what happens to the tubulovesicles?
they become microvilli and project into the canaliculus (which expand)
What enzymes are located in the microvilli of the parietal cells during acid secretion?
carbonic anhydrase, ATPase enzymes
What is the mechanism of HCL acid secretion by parietal cells?
in apical membrane active H+/K+ATPase pumps H+ ions out of cell (from dissociated water) and pumps K in (from acid secretion).
Basolateral membrane has a Cl/HCO3 exchanger that brings cl into the lumen and HCO3 into the blood.
To obtain the H needed in the HCL secretion of parietal cells, what do we need? How do we replenish this?
we need to breakdown water
To replenish water we need carbonic acid which is made from OH and CO2 (provided by metabolic sources in cell)
To get the H secretion from the parietal cell you need an abundance of H (given by water) and an increased K conductance, where does this increase in K come from?
from active acid secretion
Because of the HCO3- that is secreted into the blood stream during active acid secretion into the lumen of the oxyntic gland, the blood is quite alkaline, a phenomenon known as the (blank). Water is also drawn into the lumen, maintaining the iso-osmolallity of acid secretion.