Intro to the Digestive System
● Digestive processes (mechanically– physical force to break down food; and chemically)
○ Ingestion– the intake of food/liquids (via the mouth)
○ Propulsion– movement(transit); move the food around (down the digestive tract)
○ Digestion– chemical= using acid and enzymes to break down food
○ Absorption– the uptake of nutrients across the epithelial cells of the digestive
tract and into blood/lymph
○ Defecation– the removal of undigested materials
● Two parts
○ Digestive tract (one long tube)
■ Gastrointestinal (GI) tract or alimentary canal
■ Muscular tube (smooth muscle)
■ Extends from oral cavity to anus
○ Accessory organs
■ Teeth, tongue, and various organs (liver, pancreas, gallbladder)
,Regulation of the digestive system by the autonomic nervous system
● Parasympathetic (“rest and digest”) – generally cause an increase in digestive activities
○ Increase secretion of digestive “juices”-- enzymes, acid, etc.(things involved in
chemical digestion)
○ Increase movement of materials through GI tract
■ Open sphincters(valves), increased peristalsis
● Sympathetic– generally inhibit digestive activities
● Enteric Nervous system (just for GI tract nervous system)
Peritoneal cavity
● Part of abdominal cavity(umbrella) that contains stomach, intestines, liver, pancreas,
appendix, and liver
● Peritoneum
○ Serous membrane lining peritoneal cavity
○ Visceral peritoneum (serosa)
■ Covers organs within peritoneal cavity
○ Parietal peritoneum
■ Lines inner surfaces of body wall
● Peritoneal fluid
○ Produced by serous membrane lining
○ Allows sliding of parietal and visceral surfaces without friction or irritation
○ About 7 liters produced and absorbed daily, but very little in peritoneal cavity at
one time
■ Ascites– abdominal swelling due to buildup of peritoneal fluid (edema)
Blue(visceral); red(parietal)
, Mesenteries
● Stabilize positions of attached organs (usually sheets of connective tissue that attach
organs to each other to help lock them in place or stabilize them or connect/anchor the
organs to some part of the wall of the abdomen)
● (mesentery proper– connective tissue that in particular attaches parts of the small
intestine [jejunum and ileum] to the posterior wall of abdomen)
● (transverse mesocolon– attaches transverse colon to the posterior wall)
● (Great omentum– attaches stomach to the transverse colon, and for fats storage)
● (Lesser omentum– attach stomach and duodenum to the liver)
Layers of the digestive tract
● Mucous membrane (Mucosa)-- involved in secretion, absorption, and protection (inner
layer)-- has a lot of mucus secreting goblet cells
○ Varies by region
○ Lamina propria– areolar connective tissue– has blood capillaries to absorb
glucose, carbohydrates
○ Muscularis mucosae– enhances secretions (squeezes the glands of secreting cells)
● Submucosa– provides nutrients for other layers via blood vessels
○ Contains nerves and lymphatic vessels(lacteals)
● Muscularis externa(smooth muscle)-- mixes and moves the contents of that section of
the tube (longitudinal and circular muscles)
● Serous layer– lubricates the organs and reduces friction (aka visceral peritoneum; works
with peritoneal fluid)
● Digestive processes (mechanically– physical force to break down food; and chemically)
○ Ingestion– the intake of food/liquids (via the mouth)
○ Propulsion– movement(transit); move the food around (down the digestive tract)
○ Digestion– chemical= using acid and enzymes to break down food
○ Absorption– the uptake of nutrients across the epithelial cells of the digestive
tract and into blood/lymph
○ Defecation– the removal of undigested materials
● Two parts
○ Digestive tract (one long tube)
■ Gastrointestinal (GI) tract or alimentary canal
■ Muscular tube (smooth muscle)
■ Extends from oral cavity to anus
○ Accessory organs
■ Teeth, tongue, and various organs (liver, pancreas, gallbladder)
,Regulation of the digestive system by the autonomic nervous system
● Parasympathetic (“rest and digest”) – generally cause an increase in digestive activities
○ Increase secretion of digestive “juices”-- enzymes, acid, etc.(things involved in
chemical digestion)
○ Increase movement of materials through GI tract
■ Open sphincters(valves), increased peristalsis
● Sympathetic– generally inhibit digestive activities
● Enteric Nervous system (just for GI tract nervous system)
Peritoneal cavity
● Part of abdominal cavity(umbrella) that contains stomach, intestines, liver, pancreas,
appendix, and liver
● Peritoneum
○ Serous membrane lining peritoneal cavity
○ Visceral peritoneum (serosa)
■ Covers organs within peritoneal cavity
○ Parietal peritoneum
■ Lines inner surfaces of body wall
● Peritoneal fluid
○ Produced by serous membrane lining
○ Allows sliding of parietal and visceral surfaces without friction or irritation
○ About 7 liters produced and absorbed daily, but very little in peritoneal cavity at
one time
■ Ascites– abdominal swelling due to buildup of peritoneal fluid (edema)
Blue(visceral); red(parietal)
, Mesenteries
● Stabilize positions of attached organs (usually sheets of connective tissue that attach
organs to each other to help lock them in place or stabilize them or connect/anchor the
organs to some part of the wall of the abdomen)
● (mesentery proper– connective tissue that in particular attaches parts of the small
intestine [jejunum and ileum] to the posterior wall of abdomen)
● (transverse mesocolon– attaches transverse colon to the posterior wall)
● (Great omentum– attaches stomach to the transverse colon, and for fats storage)
● (Lesser omentum– attach stomach and duodenum to the liver)
Layers of the digestive tract
● Mucous membrane (Mucosa)-- involved in secretion, absorption, and protection (inner
layer)-- has a lot of mucus secreting goblet cells
○ Varies by region
○ Lamina propria– areolar connective tissue– has blood capillaries to absorb
glucose, carbohydrates
○ Muscularis mucosae– enhances secretions (squeezes the glands of secreting cells)
● Submucosa– provides nutrients for other layers via blood vessels
○ Contains nerves and lymphatic vessels(lacteals)
● Muscularis externa(smooth muscle)-- mixes and moves the contents of that section of
the tube (longitudinal and circular muscles)
● Serous layer– lubricates the organs and reduces friction (aka visceral peritoneum; works
with peritoneal fluid)
