Topic 14 Flashcards
Digestion involves..
- digestive tract
- accessory organs
Digestion
breakdown of large food pieces into smaller molecules
Absorption
from human to enterocytes (small intestinal cells) of villi to blood/lymph
Motility
smooth muscle contractions in tract. mix (segmentation, churning) move (peristalsis)
Secretion
digestive juice into lumen
Mouth contains..
salivary glands
Salivary glands
saliva moistens and prevents cavities (lysozyme and antibodies)
PSNS stimulate secretion of what saliva
thin, enzyme rick saliva
SNS stimulate secretion of what saliva
much rich saliva
Mouth aids in what processes
digestion and absorption
Mouth digestion
mechanical (chewing) and chemical.
Mouth breaks down carbohydrates into..
disaccharides and oligosaccharides. (using salivary amylase)
Mouth breaks down triglycerides into..
fatty acids and monoglycerides (using lingual lipase)
Mouth absorption
no food just some drugs (ex: nitroglycerine for angina/ vasodilator)
Pharynx and esophagus aids in..
swallowing
Swallowing occurs in 3 phases
- buccal phase
- pharyngeal phase
- esophageal phase
Buccal phase
voluntary. food is compacted by the tongue into a bolus and moves pharynx by tongue pressing on hard palate.
Pharyngeal phase
involuntary. food in pharynx triggers signals to swallowing centre (medulla) and initiates swallowing reflex
Esophageal phase
food mols down esophagus (peristalsis). somatic motor neurons to skel. muscle (upper 1/3). middle is mix of PSNS and motor. lower 1/3 is PSNS to smooth muscle.
Food can’t enter or re enter..
- mouth: tongue on hard palate
- nasopharynx: uvula, soft palate elevated.
- trachea: glottis and epiglottis closed
Stomach mechanical digestion
churning/motility
Stomach chemical digestion consists of..
- carbohydrates
- lipids
- proteins
Stomach chemical digestion of carbohydrates
salivary amylase unti pH <7
Stomach chemical digestion of lipids
lingual lipase (tongue), gastric lipase (chief cells), until pH <5-6
Food in stomach digestion =
buffer: pH doesn’t change right away
Stomach chemical digestion of proteins
HCl (pariental cells) denatures proteins and acts on pepsinogen (chief cells)
Stomach protected from self digestion by..
alkaline mucus (mucus cells) barrier can be penetrated by alcohol, aspirin, vinegar, bile.
Stomach absorption
very little absorption of food. some drugs like alcohol and aspirin.
Small intestine mechanical digestion
segmentation and peristalsis