Transcript Chapter 24

Chapter 24
The Digestive System
Functions of the Digestive System
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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
Ingestion
Propulsion
Mechanical Digestion
Chemical Digestion
Absorption
Defecation
Daddy, what does “retroperitoneal” mean?
This is your basic alimentary tract structure.
Sagittal view of abdominal viscera
Mesenteries
Figure 24–2a, b
Mesenteries
Figure 24–2c, d
Peristalsis
Figure 24–4
Segmentation
• Cycles of contraction:
– Churn and fragment bolus
– mix contents with intestinal secretions
• Does not follow a set pattern:
– does not push materials in any 1 direction
The oral cavity and pharynx
Say “ahhh”
Salivary Glands
Road map of the tongue
Anatomy of Teeth
Primary and
Secondary Dentitions
Figure 24–9
Histology of the Esophagus
Gastroesophageal junction
Esophagus
Stomach
Stratified squamous epithelium
Simple columnar epithelium
The Swallowing Process
Figure 24–11
The Stomach
Figure 24–12a
The Stomach
Figure 24–12b
The Stomach Lining
Figure 24–13
It’s the
pits!
(Gastric
pits that
is…)
Micrograph of the
Fundic region of the
gastric mucosa
Secretion of
HCl
Details of HCl
secretion
The Regulation of Digestive Activities
Figure 24–5
Stimulus and
control of gastric
activity
The phases of gastric secretion
Control
mechanisms
of gastric
contractions
The duodenum, gall bladder and pancreas
Hormonal
Regulation of
Pancreatic
secretions
The small intestine
Histology of the small intestine
Cells of
the
mucosa
Duodenal wall
Duodenal
mucosa
You only find us here,
In the duodenum!
Brunner’s (duodenal) glands
Crypts of Lieberkuhn!
Paneth cells
Peyer’s patches in the ileum
The Pancreas
Figure 24–18
Exocrine tissues of the pancreas
Pancreas: Acinar cells
Activation of pancreatic proteases in the duodenum
Regulatory mechanisms for release of pancreatic juice
The Liver
• Is the largest visceral organ (1.5 kg)
• Lies in right hypochondriac and epigastric
regions
• Extends to left hypochondriac and
umbilical regions
• Performs essential metabolic and
synthetic functions
The Anatomy of the Liver
Figure 24–19
Liver Histology
Figure 24–20
3 Functions of the Liver
1. Metabolic regulation
2. Hematological regulation
3. Bile production
Metabolic Regulation
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The liver regulates:
1.
2.
3.
4.
5.
composition of circulating blood
nutrient metabolism
waste product removal
nutrient storage
drug inactivation
Metabolic Activities of the Liver
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Carbohydrate metabolism
Lipid metabolism
Amino acid metabolism
Waste product removal
Vitamin storage
Mineral storage
Drug inactivation
The Gallbladder and Bile Ducts
Figure 24–21
The Gallbladder
• Stores bile
• Releases bile into duodenum:
– only under stimulation of hormone
cholecystokinin (CCK)
Gallstones
• Are crystals of insoluble minerals and salts
• Form if bile is too concentrated
• Small stones may be flushed through bile
duct and excreted
Activities of
Major
Digestive
Tract
Hormones
Figure 24–22
Hormones of Duodenal
Enteroendocrine Cells
• Coordinate digestive functions:
– secretin
– cholecystokinin (CCK)
– gastric inhibitory peptide (GIP)
– vasoactive intestinal peptide (VIP)
– gastrin
– enterocrinin
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.
Chemical Digestion & absorption of nutrients
Movement of absorbed nutrients
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.
Digestive
Secretion
and
Absorption
Figure 24–27
Absorption of Ions and Vitamins
Table 24–4
Lacteals
Anatomy of the
large intestine
The rectum
and anus
3 Parts of the Large Intestine
1. Cecum:
– the pouchlike first portion
2. Colon:
– the largest portion
3. Rectum:
– the last 15 cm of digestive tract
Histology of the colon
The Colon
Look at all those goblet cells!
Large intestine wall
Close-up of
the colonic
mucosa
Characteristics of the Colon
• Lack of villi
• Abundance of goblet cells
• Presence distinctive intestinal glands
The
Defecation
reflex
Absorption of Nutrients: redux
• 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.
Summary:
Chemical
Events in
Digestion
Figure 24–26
Clinical terms
• Ascites – Fluid accumulation in the peritoneal cavity. Possible
causes: hypertension, cirrhosis, renal or heart disease
• Bulimia & anorexia nervosa – eating disorders
• Cholecystitis – gallbladder inflammation. Can be caused by
gallstones.
• Diverticuliosis/diverticulitis – herniations of the colon wall which may
become inflammed.
• Dysphagia – difficulty swallowing.
• GERD – Gastroesophogeal reflux disease. Excess acid and/or
dyfunction of the gastroesophogeal sphincter.
• IBS – inflammatory bowel syndrome. Related to Crohn’s disease or
ulcerative colitis.
• Pancreatitis – inflammation of the pancreas. Pancreatic enzymes
activated in the within the duct. Can be caused by excessive dietary
fats hyperstimulating the pancreatic secretion.
• Peptic ulcers – usually caused by Helicobacter pylori.
Helicobacter
pylori
Worldwide Distribution of H. pylori
The End
Next, Energy Metabolism