digestive system - mouth to stomach Flashcards
tongue functions
- position food for optimal chewing
- gather food into bolus
- position food so it can be swallowed
lingual glands
in the tongue, secrete mucus and a watery serous fluid that contains the enzyme ‘lingual lipase’ which plays a minor role in breaking down triglycerides, but fully activated in stomach
three pairs of salivary glands
- submandibular glands which are on the floor of your mouth
- sublingual gland which lies below the tongue , use to secrete saliva into oral cavity
- parotid gland: between skin and master muscle, near ears and secret saliva into mouth from parotid duct
saliva contains enzyme..
salivary amylase- involved in break down of starch to glucose. deactivated when reach stomach acids
three divisions in pharynx
- nasopharynx
- oropharynx
- laryngopharynx (part continues to larynx, part continues to esophagus)
esophagus
- muscular tube that connects pharynx to stomach.
- closed off at top by upper esophageal sphincter
- rhythmic movements of peristalsis which propels food to stomach
- passed through lower esophageal sphincter to the stomach
deglutination/swallowing phases
1.voluntary phase
2. pharyngeal phase
3. esophageal phase
voluntary phase
control when you swallow food. tongue moves upwards and backwards against palate pushing bolus to back of oral cavity into the oropharynx
pharyngeal phase
- impulses are sent back and forth to uvula and soft palate, causing them to move upward and close of nasopharynx
- deglutition apnea- breathing ceases for a brief time
- contraction of pharyngeal constrictor muscles move bolus through the oropharynx and laryngopharynx
- relaxation of upper esophageal sphincter then allows food to enter esophagus
esophageal phase
peristalsis triggered as food enters esophagus.
- peristalsis occurs through alternating contractions of circular and longitudinal muscles
- muscle contractions force food in one direction
- once reaches end, relaxation of Lower esophageal sphincter allows bolus to pass to stomach
stomach divide into
cardia, funds, body, pylorus
cardia
point where esophagus connects to the stomach
stomach vs rest of digestive tract
on top of longitudinal circular smooth muscle layers, muscular has inner clique smooth muscle layer.
means that stomach can contract in three directions, facilitates ability to mash and turn material with digestive enzymes - facilitate mechanical digestion
mucosa lining secretes
alkaline mucus.
- basic mucus to help protect underlying cells and tissues from acidic gastric juices
- gastric pits: mark entry into gastric glands
cells involved in gastric glands which are important in formation of gastric juices:
- parietal cells:
- secrete HCL and intrinsic factor
- HCL needed for pepsin activation
- acidity helps kill lots of microbes, denatures proteins
- intrinsic factor: very important for absorbing B12 which help make RBC
- chief cells
- secrete pepsingon which activate with HCL to pepsin - Enteroendocrine cells:
- secrete various hormones including gastrin, the primary stomach stimulatory hormone
to prevent self-digestion, stomach is covered in
mucosal barrier.
- alkaline mucus (bicarbonate rich) forms barrier
- epithelial cells of stomachs mucosa meet at tight junctions which block gastric juice from penetrating
- stem cells that replace damaged epithelial cells: lining of stomach is rapidly rebuilt
gastric secretion is regulated in 3 phases:
- cephalic phase
(before you even eat food) - gastric phase
- intestinal phase
intestinal phase
- intestinal phase
- presence of digested food triggers release of intestinal gastrin hormone: stimulates more secretion of gastric juice from stomach
- when intestine distends with chyme, enterogastric reflex inhibits gastric emptying, pyloric sphincter blocks any more chyme from entering duodenum
- presence of fats in small intestine triggers secretion of cholecystokinin which works to Inhibit gastrin.
gastric phase
- gastric phase
- triggered by entry of food into the stomach, which causes distention that activates the stretch receptors.
- partially digested proteins, caffeine, increase in pH are also detected by chemoreceptors and will result in release of gastrin
- increase in gastric secretion increases amount of gastric churning - causes stomach to gurgle when hungry
mechanical digestion in stomach
- mixing waves occur when food enters stomach, leads to creation of chyme
- gastric emptying
what is gastric emptying
- rhythmic mixing waves of chyme through pyloric sphincter into duodenum until stomach is empty.
- regulated by stomach and small intestine
chemical digestion in stomach
- acidity of gastric juices turns off salivary amylase
- stops digestion of carbs in stomach
- activates lingual lipase which increased break down of Triglycerides
- breakdown of proteins begin in stomach through actions of HCL and pepsin
- production of intrinsic factor
