Chapter 38 Structure and Function of the Digestive System

advertisement
Chapter 38
Structure and Function of the
Digestive System
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
Gastrointestinal Tract







Mouth
Esophagus
Stomach
Small intestine
Large intestine
Rectum
Anus
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
2
Gastrointestinal Tract
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
3
Gastrointestinal Tract Functions:
Overview





Breaks down ingested food
Prepares food for uptake by the body’s cells
Provides body water
Eliminates wastes
Controlled by hormones and the autonomic
nervous system (except for chewing, swallowing,
and defecation)
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
4
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 by defecation
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
5
Gastrointestinal Tract

Histology








Mucosa
Submucosa
Muscularis
Serosa or adventitia
Enteric plexus
Submucosal plexus
Myenteric plexus
Subserosal plexus
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
6
Gastrointestinal Tract
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
7
Mouth


Reservoir for chewing and mixing of food with
saliva
Taste buds



Salty, sour, bitter, and sweet
Olfactory nerves
Teeth

32 permanent teeth
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
8
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
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
9
Swallowing


Complex event mediated by the swallowing
center, located in the reticular formation of the
brainstem; also involves other brain regions,
including the insula/claustrum and cerebellum
The swallowing center and respiratory center
provide the coordinating innervation



Superior constrictor muscle of the pharynx contracts,
prevents movement of food into the nasopharynx
Respiration inhibited and epiglottis slides downward
to prevent bolus from entering larynx and trachea
Movements of tongue and pharyngeal constrictors
propel the food into the esophagus in a series of
coordinated events taking 1 or 2 seconds
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
10
Swallowing


Esophagus
Peristalsis




Primary and secondary
Upper esophageal sphincter
Lower esophageal sphincter
Phases


Oral and pharyngeal phases
Esophageal phase
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
11
Stomach


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
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
12
Stomach

Boundaries




Cardiac orifice
Pyloric sphincter
Pylorus
Functional areas



Fundus
Body
Antrum
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
13
Stomach
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
14
Gastric Motility






Swallowing
Gastrin
Cholecystokinin
Motilin
Secretin
Gastric emptying
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
15
Gastric Secretion

The stomach secretes large volumes of
gastric juices

Mucus
 Acid
 Enzymes
 Hormones
 Intrinsic factor
 Gastroferrin
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
16
Gastric Secretion


Gastric pits
Gastric glands

Parietal cells
• Hydrochloric acid and intrinsic factor
 Chief cells
• Pepsinogen
 G cells
• Gastrin
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
17
Gastric Secretion

Gastric glands


Enterochromaffin-like cells
• Histamine
D cells
• Somatostatin
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
18
Gastric Pits and Gastric Glands
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
19
Gastric Secretion

Phases of gastric secretion



Cephalic phase
Gastric phase
Intestinal phase
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
20
Small Intestine


5 to 6 meters long
Three segments




Duodenum
Jejunum
Ileum
• Ileocecal valve
Peritoneum

Peritoneal cavity
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
21
Small Intestine

Muscle layers





Mucosal folds (plica)
Villi
Microvilli



Outer—longitudinal
Inner—circular
Brush border
Lamina propria
Lacteal
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
22
Small Intestine
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
23
Intestinal Digestion and
Absorption





Hydrochloric acid
Pepsin
Pancreatic enzymes
Intestinal enzymes
Bile salts
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
24
Intestinal Digestion and
Absorption





Carbohydrates
Proteins
Fats
Water
Electrolytes
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
25
Intestinal Digestion and Absorption
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
26
Intestinal Digestion and Absorption
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
27
Intestinal Digestion and Absorption
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
28
Intestinal Motility






Movements of the small intestine facilitate
digestion and absorption
Segmentation
Peristalsis
Ileogastric reflex
Intestinointestinal reflex
Gastroileal reflex
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
29
Large Intestine



Cecum
Appendix
Colon






Ascending
Transverse
Descending
Sigmoid
Rectum
Anus
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
30
Large Intestine
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
31
Large Intestine






Ileocecal valve
O’Beirne sphincter
Internal anal sphincter
External anal sphincter
Taenia coli
Haustra
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
32
Gastrointestinal Absorption
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
33
Intestinal Bacteria




Stomach environment is relatively sterile
because of secreted stomach acid
Bile acid secretion, motility, and antibody
production keep bacterial numbers in the
duodenum to a minimum
A low concentration of aerobes in the jejunum
Anaerobic bacteria distal to the ileocecal
valve

Anaerobes are 95% of the fecal flora in the colon
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
34
Accessory Organs of Digestion
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
35
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
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
36
Liver
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
37
Hepatic Portal Circulation
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
38
Liver

Liver lobules

Hepatocytes
 Lipocytes
 Sinusoids
 Bile canaliculi
 Common bile duct
 Major duodenal papilla (sphincter of Oddi)
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
39
Liver Lobules
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
40
Liver




Kupffer cells
Stellate cells
Pit cells
Disse space
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
41
Secretion of Bile



Alkaline, bitter-tasting, yellowish green fluid
that contains bile salts, cholesterol, bilirubin,
electrolytes, and water
Formed by hepatocytes and secreted into the
bile canaliculi
Enterohepatic circulation

Recycling of bile salts
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
42
Enterohepatic Circulation
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
43
Metabolism of Bilirubin





A byproduct of the destruction of aged red
blood cells
Gives bile a greenish black color and
produces the yellow tinge of jaundice
Unconjugated bilirubin
Conjugated bilirubin
Urobilinogen
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
44
Metabolism of Bilirubin
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
45
Vascular and Hematologic
Liver Functions





Blood storage
Bacterial and foreign particle removal
Synthesizes clotting factors
Produces bile to absorb fat-soluble vitamins
Metabolizes fats
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
46
Vascular and Hematologic
Liver Functions




Metabolizes proteins
Metabolizes carbohydrates
Metabolic detoxification
Storage of minerals and vitamins
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
47
Gallbladder



A sac-like organ that lies on the inferior
surface of the liver
Function is to store and concentrate bile
between meals
Gallbladder holds about 90 ml of bile
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
48
Exocrine Pancreas



Composed of acini and networks of ducts that
secrete enzymes and alkaline fluids to assist
in digestion
Pancreatic duct
Ampulla of Vater
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
49
Exocrine Pancreas
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
50
Exocrine Pancreas

Secretions


Potassium, sodium, bicarbonate, magnesium,
calcium, and chloride
Enzymes

Trypsinogen, chymotrypsinogen, and
procarboxypeptidase
 Trypsin inhibitor
 Pancreatic α-amylase
 Pancreatic lipase
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
51
Aging and the Digestive Function





Tooth enamel and dentin wear down
Teeth are lost
Periodontal disease
Gum recession
Osteoporotic bone changes
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
52
Aging and the Digestive Function




Number of taste buds decline
Sense of smell diminishes
Salivary secretion decreases
Decreased esophageal and gastric motility
Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.
53
Download