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29 Cards in this Set
- Front
- Back
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2 Functions of GI tract secretions:
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1. Production of digestive enzymes
2. Production of mucus |
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4 main types of secreting glands:
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1. Unicell Goblet mucous glands
2. Crypts of Lieberkuhn 3. Tubular glands 4. Complex glands |
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What are Goblet cells?
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Unicellular cells that excrete mucus in response to irritation or damage along epithelial tract surface most of the gut length.
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Function of the mucus secreted by goblet cell mucous glands:
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lubricant
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What are Crypts of Lieberkuhn?
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Pits in the GI tract surface that contain specialized cells.
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What/where are tubular glands?
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Glands mostly in the stomach and upper duodenum that secrete cell-specific secretions.
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Example of a tubular gland:
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Oxyntic glands - secrete acid and pepsinogen
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3 types of complex glands:
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-Salivary
-Liver -Pancreatic |
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What is the function of secretions of complex glands?
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Digestion and emulsification of food.
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Main stimulus for release of mucus from GI tract:
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Presence of food in contact with epithelium - causes release of mucus in that local vicinity and adjacent regions.
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2 Ways that physical stimulus causes secretion:
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-Direct contact with epithelium
-Reflex stimulus of ENS to both surface and deep glands |
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3 types of physical stimuli for gland secretions:
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-Tactile
-Chemical irritation -Gut wall distention |
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3 total ways to stimulate gland secretions:
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-Physical stimulus
-Autonomic - PNS/SNS -Hormonal |
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Effect of PNS on secretion:
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-Increases rate of secretion especially in upper portions.
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What nerves carry PNS fibers for secretion?
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9 and 10
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What nerves innervate the distal part of the large intestine?
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Pelvic sympathetics - S2-S4
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What is the effect of SNS on secretion?
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DUAL:
-Can increase secretion -But causes vasoconstriction of vessels to glands so decrease. |
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When does the SNS increase secretions?
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When acting alone
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When does the SNS decrease secretions?
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When the PNS or hormones are already active
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What stimulates the release of hormones from the stomach and intestine?
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Presence of food in gut - different types
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What do hormones then do?
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Stimulate secretions
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1st step in secretion mechanism of glandular cells:
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Deliver substrate to make secretion - by active transport and pinocytosis from capillaries.
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What do gland cells need to do to form secretions?
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-Make ATP via mitochondria
-Use ATP for synthesis |
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Where do the cells make their secretions?
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In rough ER and Golgi
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How are secretions secreted?
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After packaging into secretory vesicles Calcium influx causes exocytosis.
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What gets secreted along with secretions? Why?
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Water and electrolytes - to wash the secretions through the secretory border of cells.
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Mechanism for excretion of water and electrolytes with secretions:
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1. Nerve stimulates basal cell membane -> AT of Cl into cell
2. Cell hyperpolarizes ~15 mV to result in Na influx 3. Increased osmolarity; water follows into cell 4. Cell swells and hydrostatic pressure incr causes small ruptures of secretory border - releases water / electrolytes |
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What is Mucus made of?
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-Water
-Electrolytes -Glycoproteins |
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Functions/qualities of Mucus:
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-Lubricant/protectant/buffer
-Adheres to surfaces -Coats particles -Low resistance -Aggregates fecal particles |
