The Digestive System
Introduction
The digestive tract and accessory organs perform the following functions:
Ingestion
Mechanical processing
Digestion
Secretion
Absorption
Excretion
Compaction
Overview of the Digestive System
Histology
Mucosa: plica circularis
Epithelial layer
Microvilli
Connective tissue: lamina propria
Blood, nerves, lymph vessels & nodes (MALT)
Muscularis mucosae
Submucosa
Areolar tissue
Exocrine glands
Submucosal plexus
Histology
Muscularis externa
Circular: inner
Longitudinal: outer
Myenteric Plexus: autonomic system
Serosa – Stomach and intestines
Adventitia- Oral cavity, pharynx and esophagus
Histology of the Digestive Tract
Smooth muscle contractions
Peristalsis
Peristaltic wave
Mass peristalsis
Segmentation
Movement of Digestive Materials
Serous Membranes
Visceral peritoneum
Parietal peritoneum
Mesenteries
Greater omentum (lace apron)
Lesser omentum
Mesentery proper
Mesecolon
Transverse
Sigmoid
Serous Membranes
Intraperitoneal
Retroperitoneal
Kidneys, ureters and aorta
Secondarily retroperitoneal
Duodenum, pancreas, colon and rectum
The Peritoneum
Anatomy of the Oral Cavity
Oral Cavity
Tongue
Root, Body Tip
Papillae
Vallate, fungiform and filliform
Lingual frenulum
Lips
Superior and inferior labial frenulum
Ducts of Salivary glands – parotid, sublingual and submandibular
Palatoglossal and palatopharyngeal arches
Palatine tonsil
Pharynx
See respiratory system notes
Swallowing reflex
The Salivary Glands
The Teeth
Teeth Types
Incisors
Cuspids (canines)
Bicuspids (premolars)
Tricuspids (molars)
The Teeth
Teeth Structure
Crown
Enamel, dentin, pulp
Neck
Root
Cementum, dentin, pulp
Apical foramen & root canal
Associate Gingiva (gingival sulcus)
Associate peridontal ligament
The Esophagus
Esophagus
Adventitia
Stratified squamous epithelium
Muscularis starts as skeletal but is all smooth muscle at stomach
Ends at cardiac orifice
The Stomach
Stomach
Cardiac, body, pylorus
Greater and lesser curvatures
Rugae
Pyloric sphincter
Three layers in muscularis
Lesser omentum
Greater omentum
The Stomach
The Stomach: Histology
The Small Intestine
Small Intestine
Duodenum (4cm), jejunum (2.5m)and ileum (3.5m)
Ileocecal valve
Mesentery proper
Duodenal ampulla, duodenal papilla
Duodenal glands
Its all about surface area!
Plicae circularis
Villi: capillaries and lacteals
Microvilli
Histology of the Small Intestine
The Large Intestine
Large Intestine
Cecum – vermiform appendix
Ascending colon to hepatic or right flexure
Transverse colon – gastrocolic ligament
Splenic or left colic flexture
Descending colon
Sigmoid colon
Rectum
Anal canals and columns to anus
Internal and external anal sphincters
Columnar becomes stratified squamous epithelium
Associated Structures – Haustra, taenia coli and epiploic appendages
Histology of the Large Intestine
The Liver
Liver
Largest exocrine gland
Filters blood: fenestrated capillaries (sinusoids)
Nutrients, pathogens, toxins, worn out rbc’s
Synthesis of plasma proteins and bile
Right, left, caudate and quadrate lobes
Coronary, falciform and round ligament
Liver lobule – hepatic vein
Hepatocytes and kupffer cells
Hepatic triad – hepatic portal vein, hepatic artery and bile duct
Right, left and common hepatic duct
The Liver Lobule
Gall Bladder
Stores 40-70 milliliters of bile
Cystic duct fuses with common hepatic to form common bile duct
Hepatopancreatic sphincter
Cholecystokinin causes sphincter to relax and gall bladder to contract
The Gallbladder
Pancreas
As an exocrine gland
Pancreatic acini
Produces digestive lipases, carbohydrases, proteinases, nucleases
Secondarily retroperotineal
Head, body and tail
Pancreatic duct fuses with common bile duct at duodenal ampulla
The Pancreas