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Digestive System
AKA
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G-I Tract
Alimentary Canal
Overview
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Consists of
Mouth, pharynx, esophagus, stomach,
small intestine, large intestine, anus
About 30’ in length
Accessory Organs
• Teeth, tongue, gall bladder, salivary glands,
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liver and pancreas
Glands secrete saliva, bile and enzymes
GI System
Process Includes
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Ingestion
Mechanical – chewing, churning
Propulsion – swallowing and peristalsis
Chemical – breakdown via enzymes
Absorption – transport of end products
into blood
Defecation – elimination as feces
GI Process
Peritoneum and cavity
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Parietal peritoneum surrounds cavity, lines
body wall
Visceral surrounds organ
Serous membrane allows organs to
glide/expand
Retroperitoneal refers to organs in the dorsal
region
Peritonitis = inflammation of peritoneum
Perforation = infection
Peritoneum
Quadrants
Regions
Regions
Mesentery
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Double layer of peritoneum, holds
organs in place
Omentums - protection
Lesser = fatty skin, superficial near the
stomach
Greater = deeper, made of connective
tissue, significant fat
Three layers of fascia – Skin, Fascia,
mesentary
Messentery
Messentary
Omentum
Greater Omentum
Histology
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Smooth muscle - peristalsis
Glands with ducts
Nerves, arteries and veins
Histology
Mouth
Point of Origin
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Oral cavity
Tongue
Soft and hard palate
Uvula
Oropharynx
Epiglottis
Larynx/pharynx
Esophagus
Mouth Anatomy
Mouth Anatomy
Salivary glands
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Produce saliva, a mixture of water, ions, mucous,
and enzymes
Dissolve food
Wets food to help bind it to become a bolus
Neutralizes acids, helps growth of beneficial bacteria
Intrinsic –in tongue, palate, lips and cheeks
Extrinsic = outside mouth
• Parotids
• Submandibular
• Sublingual
Salivary Glands
Pharynx
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Oso
Laryngopharynx
Lined with epithelial cells for protection
Pharynx
Esophagus
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Muscular tube
Propels swallowed food to stomach
Passes through diaphragm (esophageal
hiatus) into abdomen
Join the stomach at cardiac orifice
Cardiac sphincter prevents reflux or
regurgitation of acid
Esophagus
Esophagus
Esophagus
Stomach
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Food churned into chyme; a paste
Secretes pepsin – a protein digesting enzyme
and HCl
Waters, electrolytes, some drugs absorbed
through stomach
Anatomy
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Cardiac orifice, fundus, lesser and greater curvature,
pylorus
Rugae = numerous longitudinal folds of mucosa which
flatten as stomach fills, allows expand
Stomach
Stomach
Stomach
Junction
Stomach
Small Intestine
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Longest part of alimentary canal
Most enzymes involved in small intestine
come from pancreas
Three divisions – each approximately
• Duodenum – 5%
• Jejunum – 40%
• Ileum – almost 50%
Duodenum
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Receives digestive enzymes from
pancreas
Bile from gall bladder and liver
Almost all nutrients are absorbed in
small intestine
Large surface area, great length
Small Intestine
Small Intestine
Duodenum
Gall Bladder
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Cystic duct
Bile duct – empties into small cystic duct
Secrete bile for duodenum digestion
Bile – Right and Left hepatic ducts to
common cystic duct to Gall bladder for
storage
From GB to bile duct to duodenum
Gall Bladder
Pancreas
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Exocrine gland – produces most
enzymes for digestion in small intestine
Endocrine function = produce hormones
that regulate levels of sugar in the blood
Main pancreatic duct
Gall Bladder and Pancreas
Pancreas
Large Intestine
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Most material has been digested by the time it
reaches LI
12-24 hours in large bowel
Little breakdown
Performs some absorption, especially water
Components
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Ascending colon
Transverse colon
Descending colon
Sigmoid to rectum and anus
Large Intestine
Large Intestine
Cecum and appendix
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Cecum is a small sac (blind pouch)
Valve prevents a back up of fecal matter
to ileum
Appendix
• Lymph tissue neutralizes bacteria
Diverticulosus – a small outward
herniation of colon, especially sigmoid
Diverticulitis – infection with leaks into
peritoneal cavity may lead to peritonitis
Anal Canal
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ANS balance between defecation or not
PNS = increase movement
SNS = decrease
Voluntary control via external sphincter
muscles
Anal Canal
Defecation
Liver
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Largest gland in the body (1.4 kg – 3 lbs.)
Produces bile
Stored in GB
Emulsifies fats
Involved in metabolism
Diaphramatic and visceral surface
Right and left lobes
Porta hepatis = major vessels and nerves
Right and left hepatic ducts, common bile,
common
Liver
Liver
Liver
Liver