Transcript Digestive System IDigestive System II

Essentials of Anatomy and Physiology
Fifth edition
Seeley, Stephens and Tate
Chapter 16: Digestive System
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Slide 2.1
Stomach Anatomy
 “J” shaped flat bag
 Located in epigastric, left hypochondriac
regions
 Food enters through gastroesophageal
(cardiac) sphincter
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Slide 14.15a
Stomach Anatomy
Figure 14.4a
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Slide 14.17
Stomach Anatomy
 Regions of the stomach
 Cardiac region
 Fundus
 Body
 Pylorus – terminal end
 Food empties into the small intestine at
the pyloric sphincter
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Slide 14.15b
Stomach Anatomy
 Rugae – internal folds of the mucosa
 External regions
 Lesser curvature
 Greater curvature
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Slide 14.16a
Stomach Anatomy
 Layers of peritoneum attached to the
stomach
 Lesser omentum
 Greater omentum
 Contains fat to insulate, cushion, and
protect abdominal organs
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Slide 14.16b
Stomach Anatomy
Figure 14.4a
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Slide 14.17
Stomach Functions
 Acts as a storage site for food
 Chemical digestion of protein begins
 Delivers chyme (processed food) to the
small intestine
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Slide 14.18
Specialized Mucosa of the Stomach
 Simple columnar epithelium
 Gastric glands – secrete gastric juice
 Chief cells – produce pepsinogens
 Parietal cells – produce hydrochloric acid
 Endocrine cells – produce gastrin
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Slide 14.19
Structure of the Stomach Mucosa
 Gastric pits
formed by folded mucosa
 Glands and specialized cells
are deeper in the gastric gland region
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Slide 14.20a
Structure of the Stomach Mucosa
Figure 14.4b, c
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Slide 14.20b
Small Intestine
 Site of nutrient absorption
 Muscular tube ~20’ long
 extends from pyloric sphincter to
ileocecal valve
 Suspended from the posterior
abdominal wall by mesentery
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Slide 14.21
Subdivisions of the Small Intestine
 Duodenum
 Attached to the stomach
 Curves around the head of the pancreas
 Jejunum
 Second portion, ~8’
 Ileum
 Longest portion, ~10’
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Slide 14.22
Chemical Digestion in the Small
Intestine
 Enzymes mix with chyme. Come from:
Intestinal cells
Pancreas (also adds HCO3-)
 Bile enters from the gall bladder
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Slide 14.23a
Chemical Digestion in the Small
Intestine
Figure 14.6
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Slide 14.23b
Villi of the Small Intestine
 Fingerlike
structures formed
by the mucosa
 Provide more
surface area
Figure 14.7a
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Slide 14.24
Structures Involved in Absorption of
Nutrients
 Absorptive cells
 Blood capillaries
 Lacteals (specialized
lymphatic capillaries)
Figure 14.7b
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Slide 14.26
Folds of the Small Intestine
 Called circular folds or plicae circulares
 Submucosal specialization
 has Peyer’s patches
collections of lymphatic tissue
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Slide 14.27
Large Intestine
 Larger in diameter, but shorter than the
small intestine
~6’ long
 Has subdivisions
Named for direction of food movement
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Slide 14.28
Large Intestine
Figure 14.8
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Slide 14.28
Functions of the Large Intestine
 Absorption of water
 Eliminates indigestible food as feces
 Does not participate in digestion
 Goblet cells produce mucus for
lubrication
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Slide 14.29
Functions of the Large Intestine
 Contains many bacteria (mostly E. coli)
 Bacteria digest our wastes
Produce vitamins, amino acids
 Vits. B, K
We absorb their “wastes”
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Slide 14.29
Structures of the Large Intestine
 Cecum – saclike first part
 Appendix
Accumulation of lymphatic tissue that
may become inflamed (appendicitis)
Hangs from the cecum
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Slide 14.30a
Structures of the Large Intestine
 Colon
 Ascending
 Transverse
 Descending
 Sigmoid (S-shaped)
 Rectum
 Anus – external body opening
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Slide 14.30b
Large Intestine
Figure 14.8
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Slide 14.28
Modifications to the Longitudinal
Layer of Muscle
 Smooth muscle reduced to three bands
(taeniae coli)
 Muscle bands are shorter than colon
 Walls are formed into pouches called
haustra
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Slide 14.31
Accessory Digestive Organs
 Salivary glands
 Teeth
 Pancreas
 Liver
 Gall bladder
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Slide 14.32
Organs of the Digestive System
Figure 14.1
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Slide 14.2b
Salivary Glands
 Salivary glands: 3 pairs
 Parotid glands – located anterior to ears
 Submandibular glands
 Sublingual glands
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Slide 14.33
Saliva
 Mixture of mucus and serous fluids
 Helps to form food into a bolus
 Contains salivary amylase
starch digestion
 Dissolves chemicals for taste buds
 We produce ~1 liter/day
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Slide 14.34
Teeth
 Function to masticate (chew) food
 Humans have two sets
 Deciduous (baby or milk) teeth
 20 teeth are fully formed by age two
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Slide 14.35a
Teeth
 Permanent teeth
 Replace deciduous teeth beginning ~6
years of age
 A full adult set is 32 teeth
 some people do not have wisdom teeth
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Slide 14.35b
Classification of Teeth
 Incisors (2)
 Canines (1)
 Premolars (2)
 Molars (3)
 Same number and type of teeth in each
“quadrant” so….
 “Dental Formula”: 2-1-2-3
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Slide 14.36a
Classification of Teeth
Figure 14.9
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Slide 14.36b
Liver
 Largest gland in the body
 Located in right hypochondriac region
 Four lobes
 Suspended by the falciform ligament
 Connected to gall bladder via common
hepatic duct
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Slide 14.39
Primary Function of Liver
 Produces bile for fat emulsification
Composition: water, plus…
 Bile salts
 Bile pigment (mostly bilirubin)
 Cholesterol
 Phospholipids
 Electrolytes
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Slide 14.40
Role of the Liver in Metabolism
 Final metabolism of most food
 Detoxifies drugs and alcohol
 Degrades hormones
 Produces cholesterol, blood proteins
 Regulates distribution of nutrients
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Slide 14.77
Gall Bladder
 Sac attached to inferior surface of liver
 Stores, concentrates bile
 Bile enters duodenum in the presence
of fatty food
 Requires hormonal signals, autonomic
innervation
 Gallstones can cause blockages
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Slide 14.41
Pancreas
 Exocrine function: Produces digestive enzymes
 Enzymes: secreted into duodenum
 Bicarbonate ions: neutralize acidic chyme
 Endocrine products of pancreas
 Insulin
 Glucagon
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Slide 14.38