Please enable JavaScript.
Coggle requires JavaScript to display documents.
Pathway through the Digestive System (SMALL INTESTINES (Regions of small…
Pathway through the Digestive System
MOUTH/PHARYNX
Mechanical breakdown of food through chewing
Involuntary swallowing of bolus
Occurrs in three phases: voluntary phase, pharyngeal phase, esophageal phase
To Esophagus
Chemical breakdown through salivary amilase
ESOPHAGUS
Epiglottis covers respiratory tract during swallowing
End of esophagus is the lower esophageal spincter (LES)
Contraction occurs behind the bolus and relaxation occurs ahead of bolus
Bolus moves from pharynx to stomach through paristalic movements
STOMACH
Chemical breakdown of bolus
through
G-cells that stimulates
Gastrin
Stimulates motility of stomach & secretions of mucus and acid
Parietal cells stimulates
Production Hydrochoric acid
Kill bacteria
Secretion of Intrinsic Factor
To help absorb B12
Chief cells
Secretion of Pepsinogen
Converts to Pepsin
Digests proteins
Pacemaker Cells
Control the rate of muscular contractions
Goblet cells
Produce mucus
Enterochromaffin-like cells (ECL)
Produce histamine and serotonin
D cells
Somatostatin
Inhibits the secretion cholecystokinin and insulin.
Passes bolus to Duodenum and small intestines
Rugae are folds in the stomach
Three phases of digestion:
Cephalic
Regulated by vagus nerve
Activated by sight, smell, taste
Gastric
Stimulated by distension of stomach (Chyme) and chemical nature of chyme
Vagus nerve and amino acids in stomach lumen stimulate gastrin release by G-cells
Intestinal
Inhibition of gastric activity
due to
Neural reflex
Stretch of duodenum inhibits gastric motility and secretion
Hormone
Fat in chyme stimulates an inhibitory hormone
Functions: Stores food, initiate digestion of proteins, kill bacteria, make chyme
Digests only proteins
No absorption
SMALL INTESTINES
Digestion of starches and absorption of some nutrients
Secretin
Cholecystokinin (CCK)
From pyloric spincter to ileoccecal valve
Regions of small intestines
Duodenum
Absorption of carbohydrates, lipids, amino acids, Ca2+, iron
Jejuneum
Absorption of carbohydrates, lipids, amino acids, Ca2+, iron
Ileum
Absorption of bile salts, vitamin B12, water electrolytes
text
Columnar epithelial cells
Villi/microvilli
Increases surface area for absorption
Core of villus
Blood capillaries:
Absorption of monosaccharides, amino acids
Lymphatic vessels
absorption of fats
Chyme in duodenum stimulates
Gastric inhibition, pancreatic secretion, bile secretion
Passes digested material to colon
LARGE INTESTINES, Rectum, Anus
Absorption of water and salt,
Feces formed
Moves to Rectum and anus
Defication
From ileocecal valve to the anus
Columnar epithelial cells
goblet cells
Scattered lymphocytes
Lympathic nodules
Contains no villi
Involved in absorption of water, electrolytes, vitamins
Contains bacteria which serve a number of functions
Absorption of vitamin B & K
Passes digested material from descending colon to sigmoid colon to Rectum
Rectum passes feeces to Anus
Expulsion from Anus
ACCESSORY ORGANS
Liver and Gallbladder
Detoxification of blood
Secretion and storage of glucose
Production of albumin
Connected via bile duct and then to small intestine
Production and secretion of bile
Pancreas
Endocrine Gland
Secretion into blood: Insulin & Glucagons
Exocrine Gland
Secretion into GI system
Pancreatic juice
Water
Bicarbonate (HCO3-)
Amylase
Digests starch
Trypsin
Digests protein
Lipase
Digests fatty acids
Secretion controlled by secretin and cholecystokinin (CCK)