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Salivary secretion & regulation (Salivary regulation ((ii) Simple…
Salivary secretion & regulation
Saliva is slightly acidic (pH6.4-6.9)
Saliva is adequate to moist buccal/oral cavity
Saliva is secreted by salivary gland-lie outside the mouth (parotid,sublingual,submandubular glands)
Saliva lubricates,dissolve,initiates chemical breakdown of food
Salivary regulation
(ii) Simple salivary reflex: response to ingestion of irritant/nausea
(iii) Conditioned salivary reflex: smell,sight,sound,memory of food
(i) ANS control: parasympathetic nerve-facial(VII),glossopharyngeal(IX)
Saliva is a fluid that continuously secreted into the mouth.
Intestinal secretion & regulation
Intestinal juice is clear yellow fluid,slightly alkaline pH 7.6
Together with pancreatic juice provides vehicle for absorption of substance from chyme
The absorptive epithelial synthesize several brush border enzymes (eg. lactase,maltase,nuclesidase,peptidase)
Intestine regulation
Small intestine
absorption of water occurs passively as a result of osmotic gradient created by active transport (aldosterone stimulates NaCl and water absorption in ileum)
most fluid and electrolytes are absorbed by small intestine
Large intestine
absorb about 90% remaining volume
absorption of water occurs passively as a result of osmotic gradient created by active transport of Na+, Cl-
Gastric secretion & regulation
Gastric gland secrete gastric juice:
Goblet cell/neck cell: mucous
Parietal cell/oxyntic cell: HCL,intrinsic factor
Chief cell: pepsinogen
Enterochromaffin-like cells(ECL): histamine,serotonin
G cell: gastrin
D cell: somatostatin
Stomach: ghrelin
Gastric regulation (3 phases)-controlled by both neural & hormonal mechanism
(i)
Cephalic phase
: stimulated by sensory receptors mediated through parasympathetic nerve
(ii)
Gastric phase
: food reach stomach, it stretch & stimulates chemoreceptor by alkaline of food. Submucosal plexus stimulates parasympathetic nerve fibres to increase stomach motility and gastrin secretion
(iii)
Intestinal phase
: Stretch receptor detects duodenal distension, chemoreceptor detects fatty acid & glucose
triggers GL hormones secretion (GIP-inhibits gastric secretion,motility),secretin(decrease gastric secretion),CCK(inhibit stomach emptying)