lecture 25 - secretion Flashcards
What is secretion?
Movement of solutes and water from the body to the lumen, across some kind of membrane or barrier
What is absorption?
Movement of solutes and water from the lumen into the body across some kind of membrane
What are exocrine secretions produced by?
Epithelia, can then move into the lumen
What are the 3 key components of GI exocrine secretions?
Mucus, electrolyte solution/serous fluid, digestive enzymes
What is the function of electrolyte solution/serous fluid in the GI tract?
Dilutes food, provides optimal pH and aids in chemical digestion
What are the functions of digestive enzymes?
Chemical digestion and aid in absorption
What part of the GI tract has the lowest pH?
The stomach (~1)
What part of the GI tract shows the greatest change in pH?
The duodenum and upper jejunum as stomach acid is neutralised
Is the pancreas slightly acidic or slightly basic?
Basic - ion produces bicarbonate
What is osmolarity?
The total ion/solute concentration
What part of the GI system has the lowest osmolarity?
Saliva - 100mOsm
Why is reabsorption of electrolyte solution from the stomach important?
Approx. 8L a day is secreted, while we only have about 3L of plasma
What is the approximate volume of electrolyte solution secretied from the GI tract daily?
8L
What is the basal/resting secretion rate of saliva?
0.3ml/min
What is the stimulated secretion rate of saliva?
1.5mL/min
What are the 3 key components of saliva?
Mucus, dilute solution of NaHCO3/NaCl, digestive enzymes
What is the function of the mucus found in saliva?
lubrication
What is the function of the dilute solution of NaHCO3 (sodium bicarbonate) and NaCl (sodium chloride) in saliva?
Dilution of food and providing an optimal pH for digestive enzymes
What are the 2 types of digestive enzyme secreted in saliva?
Lingual lipase, alpha-amylase
Where are the sublingual glands located?
Under the tongue
Where are the submandibular glands located?
Under the jaw
Where are the parotid glands located?
Just below/in front of the ears
What salivary gland secretes the majority of the saliva?
Submandibular glands
How does salvia aid in chewing and swallowing?
dissolves and lubricates food
What is the condition resulting in a dry mouth from reduced or absent saliva?
Xerostomia
What does lingual lipase digest, and where?
Fats, in the mouth as secreted in saliva
What does alpha-amylase digest, and where is it found?
Starch, released from salivary glands and the pancreas
What is nervous system regulation of salivary secretion triggered by?
Thought, smell sight of food or prescience of food in the mouth
What is the result of parasympathetic activation of salivary glands?
Secretion of copious quantities of fluid
What is the result of sympathetic activation of salivary glands?
secretion of small volumes of viscous fluid
What is the volume of gastric fluid secreted each day?
2-3L
What do the surface epithelial cells off the stomach secrete?
Bicarbonate, and goblet cells secrete mucus
What is the function of intrinsic factor, which is secreted by parietal cells?
binds to vitamin b12, stabilising it to prevent it being digested so it can be absorbed in the small intestine
What is needed to convert pepsinogen to pepsin?
HCl
Where are enteroendocrine cells found in gastric glands?
At the very bottom of gastric glands
What is the upper part of a gastric gland called?
a gastric pit
What is the function of the mucus secreted n the stomach?
Protects against abrasion. Contains surface bicarbonate which buffers the acid
What is pepsin?
Gastric proteolytic enzyme - begins digestion of proteins in the stomach
How does stomach acid have a protective role?
Natures bacteria and viruses to prevent infection
How does pH impact protein?
low pH denatures protein structure