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Chapter 24
The Digestive System
Functions of the Digestive System
• Ingest food
• Digest food
• Absorb nutrients
• Eliminate indigestible waste
Digestive anatomy overview
Organization of the Digestive organs
Alimentary Canal Mouth Pharynx Esophagus Stomach Small intestine Large intestine Anus
Accessory organs Teeth Tongue Salivary glands Gall bladder Liver Pancreas
The Digestive Process
IngestionPropulsionMechanical DigestionChemical DigestionAbsorptionDefecation
Motility vs. MixingThe difference between peristalsis and segmentation:
Peristalsis moves food along the tract. Segmentation is mixing and part of the mechanical digestion
process.
Daddy, what does “retroperitoneal” mean?
This is your basic alimentary tract structure.
The oral cavity and pharynx
Say “ahhh”…
Road map of the tongue
Salivary glands
Human dental formula:Baby teeth
Human dental
formula: Permanent
teeth
Anatomy of a Tooth
The Stomach
Gastroesophageal junctionEsophagus
Stomach
Stratified squamous epitheliumSimple columnar epithelium
Gastric histology
Stimulus and control of gastric activity
HCl secretion
The stately process of gastric emptying
Control mechanisms
of gastric contractions
The duodenum, gall bladder and pancreas
Histology of the small intestine
Adaptation for absorption
Duodenal mucosa
Duodenal glands
VilliGoblet cells
Crypts of Lieberkuhn!
Brunner’s (duodenal) glands
You only find us here,In the duodenum!
Absorption of Nutrients• Nearly all occurs in the small intestine.
– 80% of the electrolytes and virtually all food
• Most nutrients are absorbed by active transport.– Glucose, amino acids, & nucleic acids are absorbed
by secondary active transport with sodium.– Iron and calcium require transport proteins (ferritin) or
cofactors (vitamin D).– Anions follow Na+.
• Vitamins -– Fat soluble (A, D, E & K) vitamins are carried with
micelles. Much of the K is absorbed in the colon.– Water soluble vitamins diffuse with the exception of
B12, which requires intrinsic factor.
Crypts of Lieberkuhn!
Paneth cells
The Liver
Hormonal regulation of bile release
Exocrine tissues of the pancreas
Pancreas: Acinar cells
Activation of pancreatic proteases in the duodenum
Regulatory mechanisms for release of pancreatic juice
Anatomy of the large intestine
The Colon
Look at all those goblet cells!
The rectum and anus
The peritoneum
The Defecation
reflex
Location of mesentary:The lesser omentum
Location of mesentary:The greater omentum
Chemical Digestion Carbohydrates & proteins
Chemical Digestion Lipids & Nucleic acids
Protein digestion in the small intestine
Bile salts emulsify fats
Absorption of lipid
Dietary fats are absorbed into the “lacteals” of the lymphatic system before being transferred to the circulatory system.
Lacteals