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Saliva on a baby's lips. Saliva (commonly referred to as spit or drool) is an extracellular fluid produced and secreted by salivary glands in the mouth.In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be extracted), enzymes (such as lingual lipase and amylase), and antimicrobial agents (such as secretory IgA, and lysozymes).
The paired submandibular glands (historically known as submaxillary glands) are major salivary glands located beneath the floor of the mouth.In adult humans, they each weigh about 15 grams and contribute some 60–67% of unstimulated saliva secretion; on stimulation their contribution decreases in proportion as parotid gland secretion rises to 50%. [1]
The sympathetic nervous system's primary process is to stimulate the body's fight or flight response. It is, however, constantly active at a basic level to maintain homeostasis. [4] The sympathetic nervous system is described as being antagonistic to the parasympathetic nervous system.
The α 2-adrenergic receptor binds both norepinephrine released by sympathetic postganglionic fibers and epinephrine (adrenaline) released by the adrenal medulla, binding norepinephrine with slightly higher affinity. [4] It has several general functions in common with the α 1-adrenergic receptor, but also has specific effects of its own.
Parasympathetic stimulation evokes a copious flow of saliva. Parasympathetic innervation to the salivary glands is carried via cranial nerves . The parotid gland receives its parasympathetic input from the glossopharyngeal nerve (CN IX) via the otic ganglion , [ 14 ] while the submandibular and sublingual glands receive their parasympathetic ...
The myenteric plexus (or Auerbach's plexus) provides motor innervation to both layers of the muscular layer of the gut, having both parasympathetic and sympathetic input (although present ganglion cell bodies belong to parasympathetic innervation, fibers from sympathetic innervation also reach the plexus), whereas the submucous plexus provides secretomotor innervation to the mucosa nearest the ...
Preganglionic fibers en route to the pterygopalatine ganglion (destined to ultimately innervate the lacrimal gland and the mucosal glands of the nose, palate, and pharynx) subsequently form the greater petrosal nerve, whereas those en route to the submandibular ganglion (destined to ultimately innervate the submandibular and sublingual salivary glands) subsequently form the chorda tympani.
Saliva moistens and softens food, and along with the chewing action of the teeth, transforms the food into a smooth bolus. The bolus is further helped by the lubrication provided by the saliva in its passage from the mouth into the esophagus. Also of importance is the presence in saliva of the digestive enzymes amylase and lipase.