1What are the 4 processes of digestion? Explain them...
Motility - Mix food and move it forward
Secretion - Movement of water, electrolytes into ECF. Enzymes, bile salts and mucus are secreted into GI tract.
Digestion - Hydrolysis of polysaccharides into dissacharides into monosaccharides. Triglycerides into monoglycerides.
Absorption - Transport of small absorbable material across GI wall into blood.
2What regulates motility and secretion?
Autonomous smooth muscle, Intrinsic nerve plexus, Extrinsic nerves, Gastrointestinal hormones.
3What electrical activity from the autonomous smooth muscles drives GI motility and secretion?
Pacemaker unit and slow wave potential
4What is the intrinsic nerve plexus?
Enteric nervous system (myenteric plexus and submucous plexus). Dedicated to digestive system and contains sensory and motor neurons.
5How do extrinsic nerves regulate GI activity?W
Autonomic nervous system:
SNS decreases motility and secretion, PNS increases motility and secretion
6Explain Gastrointestinal Hormones...
Releases from portion of GI tract and produce excitation or inhibition in regions of GI tract.
7What are the major types of receptors in the Digestive system?
Chemoreceptors - Detect chemicals in lumen
Mechanoreceptors - Detect stretch in cheeks
Osmoreceptors - Detect changes in osmolarity
8What are the components/primary organs of the GI tract?
Mouth - Mechanical digestion
Pharynx and Esophagus - Move food forward
Stomach - Digestion
Small intestine - Digestion and absorption (workhorse)
Large intestine - Absorption (salt and water)
9What are the accessory organs of the GI tract?
Pancreas, liver, gallbladder, salivary glands
Does not touch food, secretes substance into digestive tract to ease digestion.
10What are the 4 functions of saliva?
Speech
Oral hygiene - Lysozomes and HCO3
Lubricates food - Mucus moistens food and eases its digestion via mucin
Begins carb digestion - Salivary amylase breaksdown polysaccharides
11Explain the regulation of saliva...
Basal levels controlled by pns
Simple reflexes occur when chemo or mechano receptors respond to food in mouth, salivary center in medulla triggers extrinsic ANS.
Acquired reflex requires no physical stimulation or receptors.
12Explain how the Pharynx and Esophagus moves food from mouth to stomach...
Tongue pushes food bolus to back of mouth, pharyngeal pressure receptor triggers swallowing center in medulla, activates muscles.
Perastaltic waves push food into stomach
13What happens if food bolus becomes stuck?
Seconday peristaltic wave will occur regulated by intrinsic reflexes.
14What are the 2 major components of the stomach?
Oxyntic mucosa and pyloric gland area
15What is the purpose of Oxyntic mucosa? What are the cells?
Exocrine secretions aid in digestion
Mucuos (goblet) cells - mucus
Chief cells - pepsinogen
Parietal cells - HCL and intrinsic factors
16What is the purpose of Pyloric gland area? What are the cells?
Chemical signals needed to regulate digestion
Enterochromaffin - Like (ECL) cells, releases histamine
G-cells - releases Gastrin
D-cells - releases Somastatin
17What is the function of HCL in digestion?
Activates pepsinogen into pepsin, autocatalytic process
Provides an acidic environment that is optimal for pepsin acitivity
Aids in breakdown of muscles
Denatures proteins
18What pathways regulate parietal and chief cell secretions? explain
Ach - Stimulatory, neurotransmitter from nerve plexus in response to short reflexes
Gastrin - Stimulatory, endocrine signals release from g cells in response to protein production in stomach.
Histamine - Stimulatory to parietal cells, paracrine signals released from enterochromaffine like cells in response to gastrin or ach.
Somatostatin - Inhibitory, paracrine signals release from D cells in response to acid, causes negative feed back of parietal cells, g cells and enterochromaffin like cells.
19What signals promote stomach emptying?
Stretch of smooth muscle
Intrinsic plexus via mechanoreceptors
Gastrin production from stomach
Fluid volume of stomach
20What inhibits stomach opening?
closing of pyloric sphincter
21What signals from the duodenum inhibit emptying?
Fat, acid, hypertonicity, distension, fluid volume of the duodenum
22Which receptors detect these inhibitory signals?
Chemoreceptors (fats and acids)
Osmoreceptors (hypertonicity)
Mechanoreceptors (Distension)
23What are the neural and hormonal responses that regulate stomach emptying?
Enerogastric reflex and enterogastrons, secretin, cholecystokinin
24What are the digestive enzymes of the small intestine?
Enterokinase - activates pancreatic trypsinogen
Disaccharidases - Complete CHO digestion
Aminopeptidases - Breaks small peptides down into amino acids
25What are the pancreatic exocrine secretions?
NaHCO3
Proteolytic zymogens (inactive)
Pancreatic amylase (active)
Pancreatic lipase (active)
Trypsinogen
Chymotrypsinogen
Procarboxypeptidase
26What activates trypsin? Chymotripsin? Procarboxypeptidase?
Enterokinase, Trypsin, Trypsin
27What is unique about pancreatic lipase and what does it digest?
Only one to digest fats, digests triglycerides to monoglycerides to 2 fatty acids.
28Regulation of pancreatic secretions, what are the secretions?
Secretin and CCK
Secretin produced in response to acid in duodenum, regulates release of NaHCO3
CCK produced in response to fat and protein content, regulates release of digestive enzyme
29What is the billary system?
Consist of liver which will produce bile that aids in fat digestion and absorption.
30What aids in fat digestion of the billary system?
Cholesterol, bile salts, lecithin
31Where does most absorption occur in the small intestine? Why?
Duodenum and Jejunum, large surface area and folds
32What are capillary networks function?
Carries absorbed nutrients away