Transcript Cellular Biology

Structure and Function of
the Digestive System
Chapter 38
1
Gastrointestinal Tract







Mouth
Esophagus
Stomach
Small intestine
Large intestine
Rectum
Anus
2
Mosby items and derived items © 2006 by Mosby, Inc.
Gastrointestinal Tract
3
Mosby items and derived items © 2006 by Mosby, Inc.
Gastrointestinal Tract







Ingestion of food
Propulsion of food and wastes from the mouth
to the anus
Secretion of mucus, water, and enzymes
Mechanical digestion of food particles
Chemical digestion of food particles
Absorption of digested food
Elimination of waste products by defecation
4
Mosby items and derived items © 2006 by Mosby, Inc.
Gastrointestinal Tract

Histology








Mucosa
Submucosa
Muscularis
Serosa or adventitia
Enteric plexus
Submucosal plexus
Myenteric plexus
Subserosal plexus
5
Mosby items and derived items © 2006 by Mosby, Inc.
Gastrointestinal Tract
6
Mosby items and derived items © 2006 by Mosby, Inc.
Mouth


Reservoir for chewing and mixing of food
with saliva
Taste buds



Salty, sour, bitter, and sweet
Olfactory nerves
Teeth

32 permanent teeth
7
Mosby items and derived items © 2006 by Mosby, Inc.
Salivary Glands

Three pairs




Submandibular
Sublingual
Parotid
Saliva


Water with mucus, sodium, bicarbonate, chloride,
potassium, and salivary α-amylase (carbohydrate
digestion)
Controlled by sympathetic and parasympathetic fibers
8
Mosby items and derived items © 2006 by Mosby, Inc.
Swallowing


Esophagus
Peristalsis




Primary and secondary
Upper esophageal sphincter
Lower esophageal sphincter
Phases


Oral and pharyngeal phases
Esophageal phase
9
Mosby items and derived items © 2006 by Mosby, Inc.
Stomach


The stomach is a hollow, muscular organ that
stores food, secretes digestive juices, mixes
food with the juices, and propels partially
digested food (chyme)
Muscle layers



Longitudinal
Circular
Oblique
10
Mosby items and derived items © 2006 by Mosby, Inc.
Stomach

Boundaries




Cardiac orifice
Pyloric sphincter
Pylorus
Functional areas



Fundus
Body
Antrum
11
Mosby items and derived items © 2006 by Mosby, Inc.
Stomach
12
Mosby items and derived items © 2006 by Mosby, Inc.
Gastric Motility






Swallowing
Gastrin
Cholecystokinin
Motilin
Secretin
Gastric emptying
13
Mosby items and derived items © 2006 by Mosby, Inc.
Gastric Secretion

The stomach secretes large volumes of gastric
juices






Mucus
Acid
Enzymes
Hormones
Intrinsic factor
Gastroferrin
14
Mosby items and derived items © 2006 by Mosby, Inc.
Gastric Secretion


Gastric pits
Gastric glands

Parietal cells


Chief cells


Hydrochloric acid and intrinsic factor
Pepsinogen
G cells

Gastrin
15
Mosby items and derived items © 2006 by Mosby, Inc.
Gastric Secretion

Gastric glands

Enterochromaffin-like cells


Histamine
D cells

Somatostatin
16
Mosby items and derived items © 2006 by Mosby, Inc.
Gastric Pits and Gastric Glands
17
Mosby items and derived items © 2006 by Mosby, Inc.
Gastric Secretion

Phases of gastric secretion



Cephalic phase
Gastric phase
Intestinal phase
18
Mosby items and derived items © 2006 by Mosby, Inc.
Small Intestine


5 to 6 meters long
Three segments



Duodenum
Jejunum
Ileum


Ileocecal valve
Peritoneum

Peritoneal cavity
19
Mosby items and derived items © 2006 by Mosby, Inc.
Small Intestine

Muscle layers





Mucosal folds (plica)
Villi
Microvilli



Outer—longitudinal
Inner—circular
Brush border
Lamina propria
Lacteal
20
Mosby items and derived items © 2006 by Mosby, Inc.
Small Intestine
21
Mosby items and derived items © 2006 by Mosby, Inc.
Intestinal Digestion and Absorption





Hydrochloric acid
Pepsin
Pancreatic enzymes
Intestinal enzymes
Bile salts
22
Mosby items and derived items © 2006 by Mosby, Inc.
Intestinal Digestion and Absorption





Carbohydrates
Proteins
Fats
Water
Electrolytes
23
Mosby items and derived items © 2006 by Mosby, Inc.
Intestinal Digestion and Absorption
24
Mosby items and derived items © 2006 by Mosby, Inc.
Intestinal Digestion and Absorption
25
Mosby items and derived items © 2006 by Mosby, Inc.
Intestinal Digestion and Absorption
26
Mosby items and derived items © 2006 by Mosby, Inc.
Intestinal Motility






The movements of the small intestine
facilitate both digestion and absorption
Segmentation
Peristalsis
Ileogastric reflex
Intestinointestinal reflex
Gastroileal reflex
27
Mosby items and derived items © 2006 by Mosby, Inc.
Large Intestine



Cecum
Appendix
Colon






Ascending
Transverse
Descending
Sigmoid
Rectum
Anus
28
Mosby items and derived items © 2006 by Mosby, Inc.
Large Intestine
29
Mosby items and derived items © 2006 by Mosby, Inc.
Large Intestine






Ileocecal valve
O’Beirne sphincter
Internal anal sphincter
External anal sphincter
Taenia coli
Haustra
30
Mosby items and derived items © 2006 by Mosby, Inc.
Gastrointestinal Absorption
31
Mosby items and derived items © 2006 by Mosby, Inc.
Intestinal Bacteria




The environment of the stomach is relatively sterile
because of secreted stomach acid
Bile acid secretion, motility, and antibody production
keeps bacterial numbers in the duodenum to a
minimum
There is a low concentration of aerobes in the
jejunum
Anaerobic bacteria are distal to the ileocecal valve

Anaerobes are 95% of the fecal flora in the colon
32
Mosby items and derived items © 2006 by Mosby, Inc.
Accessory Organs of Digestion
33
Mosby items and derived items © 2006 by Mosby, Inc.
Accessory Organs of Digestion

Liver

Lobes


Separated and attached to the anterior abdominal wall
by the falciform ligament
Right lobe



Caudate and quadrate lobes
Left lobe
Glisson capsule
34
Mosby items and derived items © 2006 by Mosby, Inc.
Liver
35
Mosby items and derived items © 2006 by Mosby, Inc.
Hepatic Portal Circulation
36
Mosby items and derived items © 2006 by Mosby, Inc.
Liver

Liver lobules






Hepatocytes
Lipocytes
Sinusoids
Bile canaliculi
Common bile duct
Major duodenal papilla (sphincter of Oddi)
37
Mosby items and derived items © 2006 by Mosby, Inc.
Liver Lobules
38
Mosby items and derived items © 2006 by Mosby, Inc.
Liver




Kupffer cells
Stellate cells
Pit cells
Disse space
39
Mosby items and derived items © 2006 by Mosby, Inc.
Secretion of Bile



Bile is an alkaline, bitter-tasting, yellowish
green fluid that contains bile salts, cholesterol,
bilirubin, electrolytes, and water
Bile is formed by hepatocytes and secreted
into the bile canaliculi
Enterohepatic circulation

Recycling of bile salts
40
Mosby items and derived items © 2006 by Mosby, Inc.
Enterohepatic Circulation
41
Mosby items and derived items © 2006 by Mosby, Inc.
Metabolism of Bilirubin





Bilirubin is a by-product of the destruction of
aged red blood cells
Bilirubin gives bile a greenish black color and
produces the yellow tinge of jaundice
Unconjugated bilirubin
Conjugated bilirubin
Urobilinogen
42
Mosby items and derived items © 2006 by Mosby, Inc.
Metabolism of Bilirubin
43
Mosby items and derived items © 2006 by Mosby, Inc.
Vascular and Hematologic Liver
Functions





Blood storage
Bacterial and foreign particle removal
Synthesizes clotting factors
Produces bile to absorb fat-soluble vitamins
Metabolizes fats
44
Mosby items and derived items © 2006 by Mosby, Inc.
Vascular and Hematologic Liver
Functions




Metabolizes proteins
Metabolizes carbohydrates
Metabolic detoxification
Storage of minerals and vitamins
45
Mosby items and derived items © 2006 by Mosby, Inc.
Gallbladder



The gallbladder is a saclike organ that lies on
the inferior surface of the liver
The function of the gallbladder is to store and
concentrate bile between meals
The gallbladder holds about 90 mL of bile
46
Mosby items and derived items © 2006 by Mosby, Inc.
Exocrine Pancreas



The exocrine pancreas is composed of acini
and networks of ducts that secrete enzymes
and alkaline fluids to assist in digestion
Pancreatic duct
Ampulla of Vater
47
Mosby items and derived items © 2006 by Mosby, Inc.
Exocrine Pancreas
48
Mosby items and derived items © 2006 by Mosby, Inc.
Exocrine Pancreas

Secretions


Potassium, sodium, bicarbonate, magnesium,
calcium, and chloride
Enzymes




Trypsinogen, chymotrypsinogen, and
procarboxypeptidase
Trypsin inhibitor
Pancreatic α-amylase
Pancreatic lipase
49
Mosby items and derived items © 2006 by Mosby, Inc.
Aging and the Digestive Function





Tooth enamel and dentin wear down
Teeth are lost
Periodontal disease
Gum recession
Osteoporotic bone changes
50
Mosby items and derived items © 2006 by Mosby, Inc.
Aging and the Digestive Function




Number of taste buds decline
Sense of smell diminishes
Salivary secretion decreases
Decreased esophageal and gastric motility
51
Mosby items and derived items © 2006 by Mosby, Inc.