Overview of the Digestive System Digestive Tract: Mouth, pharynx, and esophagus, stomach, small intestine, and large intestine (colon) Accessory Organs: Teeth, tongue, salivary glands, pancreas, liver, and gallbladder
Dec 25, 2015
Overview of the Digestive System
Digestive Tract: Mouth, pharynx, and esophagus, stomach, small intestine, and large intestine (colon)
Accessory Organs:Teeth, tongue, salivary glands, pancreas, liver, and gallbladder
Functions of the Digestive System
• Ingestion• Mechanical
processing• Chemical
digestion• Secretion• Absorption• Excretion
Mucosa (Innermost Layer)
• Epithelium• Connective
Tissue (Blood vessels, lymphatic vessels, lymphatic nodules)
• Smooth Muscle
Submucosa
Connective tissue
• Blood vessels
• Lymphatic vessels
• Nerve plexus
• May have glands and lymphatic tissue
Muscularis ExternaSmooth or Skeletal Muscle
If smooth muscle, usually 2 layers (circular and longitudinal)
Components of the Digestive System
GI Tract:
•Oral Cavity•Pharynx•Esophagus•Stomach•Small Intestine•Large Intestine
The Esophagus
• Stratified squamous epithelium
• Mucous glands
• Muscularis externa – skeletal muscle first third of length
Peristalsis in EsophagusLE 21-8
Bolus offood
Muscles relax,allowingpassagewayto open
Stomach
Musclescontract,constrictingpassagewayand pushingbolus down
Musclesrelax
Muscles contract
Muscles relax
Muscles contract
Small Intestine – Gross Anatomy• Longest portion of
the alimentary canal
• Site of most enzymatic digestion and absorption
• Three subdivisions• Duodenum,
jejunum, and ileum
Duodenum and Related OrgansLE 21-11a
LiverBile
Gall-bladder
Bile
Duodenum ofsmall intestine
Acid chyme
Pancreaticjuice
Intestinal enzymes
Stomach
Pancreas
LE 21-11b
Veinwith blooden route tothe liver
Musclelayers
Lumen
Largecircular folds
Villi
Nutrientabsorption
Lymphvessel
Intestinal wall
Villi
Bloodcapillaries
Epithelialcells
Nutrientabsorption
Lumen of intestine
Epithelial cells
Lymph
Blood
Fats
Aminoacidsand
sugars
Fattyacidsand
glycerol
Nutrient absorptioninto epithelial cells
Microvilli
Small Intestine: Duodenum
Br = Brunner glands
V = Villus
G = Goblet cells
Cr = Intestinal glands
MM = Muscularis Mucosae
LP = Lamina Propria
Gross Anatomy of Large Intestine
•Cecum
•Appendix
•Ascending
•Transverse
•Descending
•Sigmoid colon
•Rectum
•Anus
LE 21-12
Largeintestine(colon)
Sphincter
Endof smallintestine
Nutrientflow
Appendix
Cecum
Anus
Rectum
Smallintestine
Gross Anatomy of Large Intestine• Rectum – descends along the inferior half of the
sacrum
• Anal Canal – the last subdivision of the large intestine
Microscopic Anatomy of Large Intestine
• Villi are absent
• Contains numerous goblet cells
• Intestinal crypts – simple tubular glands
• Lined with simple columnar epithelial tissue
• Epithelium changes at anal canal• Becomes stratified squamous epithelium
Liver
• Largest gland in the body
• Performs over 500 functions
• Digestive function – bile production
• Performs many metabolic functions
The Peritoneal Cavity and Peritoneum• Mesentery – a
double layer of peritoneum• Holds organs in
place
• Sites of fat storage
• Provides a route for circulatory vessels and nerves
Disorders of the Digestive System
• Intestinal obstruction • Mechanical obstructions
• Adhesions, tumors, or foreign objects
• Nonmechanical obstruction • Halt in peristalsis
• Trauma
• Intestines touched during surgery
Disorders of the Digestive System
• Inflammatory bowel disease • Inflammation of intestinal wall
• Crohn’s disease
• Ulcerative colitis
• Viral hepatitis – jaundice and flu-like symptoms • Major types – A, B, C, and G
• Cystic Fibrosis and the Pancreas