Digestive System Flashcards
Main structures of the digestive system
oral cavity
esophagus
stomach
small and large intestines
accessory organs in digestive system + basic role
pancreas- releases pancreatic juice that neutralizes chyme and contains enzymes needed for carbs, pro, lipid digestion
liver- produce bile for lipid digestion
gallbladder- stores and releases bile for lipid digestion
state layers of the lumen
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
Mucosa function
epithelial on contact with food, innermost layer
- acts as a membrane, lined with epithelial cells
- 3 parts: mucosal membrane, lamina propria (connective and lymphoid tissues), muscularis mucosa (smooth muscle)
submucosa function
controls GI secretions, local blood flow control
o Connective tissues
o Blood
o Lymphatic vessels
o Lymphoid tissues
o Submucosal plexus
Muscularis externa function
o Outer smooth muscle around submucosal
o Controls movement (strength, frequency)
Serosa Function
Outermost layer, lubricant fluids
o Flat mesothelial cells
Oral cavity structures
mouth and pharynx
salivary glands:
- parotid
- submandibular
-sublingual
enzymes in saliva (amylase)
esophagus functions
Moves bolus (chewed food) from oral cavity to stomach
Swallowing stages: Voluntary, pharyngeal, esophageal
Peristalsis (rhythmic contraction and relaxation of esophagus muscles, happens throughout entire GI tract)
Gastroesophageal sphincter (relaxed = open esophagus)
Esophagus disorder: GERD (Acid)
stomach 4 regions
- cardia region
- fundus
- body
- Antrum or distal pyloric
3 gastric glands
cardiac, oxyntic, pyloric
3 phases of digestion
- Before food reaches the stomach
o Acetylcholine, gastrin
o Prepares GI system for food (salivation) - Once food is in stomach
o Stomach distension enhances gastric secretions
o Digestion
o Prepare for absorption - After food has left stomach
o Reduction in chyme volume and pH (below 2) trigger release of somatostatin
Somatostatin: helps reset stomach to normal and prepare for more food
pancreas functions
- Ductless endocrine cells that secrete hormones into the blood (insulin, glucagon)
- Digestive enzymes produces by acinar exocrine cells
pancreatic juice contains:
o Water
o Electrolytes
o Bicarbonate
o Pancreatic digestive enzymes
liver structure
- Consists of lobes made of lobules (right and left)
- Portal circulation
- Bile canaliculi (between liver cells)
- makes bile
bile functions
o Bile composed of bile acids and salts, cholesterol, phospholipids and bile pigments in alkaline solution
o Bile acts like a detergent to emulsify fats and oils
o Large fat globules to droplets
gallbladder function
- Concentrates and stores bile
- Disorders: gallstones
o Common in older adults
o Cholesterol bile is not released
o Lipids and Calcium deposit around cholesterol - Recirculation and excretion of bile:
o Most bile salts are reabsorbed - Bile circulation and hypercholesterolemia
Absorptive process/path
- Absorption beings in the duodenum and continues through jejunum and ileum
- Absorption is rapid (few hours for macros)
- Absorption methods:
o Diffusion, facilitated diffusion, active transport or pinocytosis/endocytosis
large intestine function
- Contracts to mix materials
- proximal colonic mucosal cells absorb sodium and water (influenced by hormones, materials dehydrated)
- colonic secretions:
o goblet cells secrete mucus- help move remaining material through large GI
o bicarbonate- gastric juice, acidic
Neural regulation
- local regulation
- myenteric plexus: peristalsis, motility
- submucosal plexus: secretions, local blood flow
- regulatory peptides: hormones, paracrines
Regulation of Gastric Motility and Gastric emptying
- peristaltic waves propel digestive contents:
o basic electrical rhythm is initiated by pacemaker cells - gastric emptying is affected by factors in stomach and duodenum
- dietary fat intake has an inhibitory effect on gastric emptying (increase fat = decrease digestion)
regulatory peptides
- paracrine-acting substances
- Neurocrine peptides
- Other hormones: ghrelin, leptin, CRH
o Appetite and satiety
EAR
average amount of a nutrient required for good health. If everyone in the population consumed this amount, only 50% would obtain enough of the nutrient to meet their requirements
RDA
set by adding a safety factor to the EAR. About 98% of the population meets its needs by consuming this amount
- RDA= EAR + 2SD (standard deviations)
UL
set well above the needs of everyone in the population. Represents the highest amount of the nutrient that will not cause toxicity symptoms in the majority of healthy people
- RDA= EAR + 2SD (standard deviations)
