Download Digestive System

The Digestive System
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Functions
• Chemical and physical breakdown of
nutrients
• Elimination of solid waste
• Absorption of nutrients into bloodstream
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2 Types of Digestion
--Mechanical Digestion is physical.
• Chew, tear, grind, mash, mix
• Occurs in the mouth (teeth & tounge)
• Occurs in stomach (churning and
mixing)
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2 Types of Digestion
– Chemical
• Catabolic reactions
• Enzymatic hydrolysis
–Carbohydrate- in mouth with salivase
& intestines with carbohydrase
–Protein- in stomach with protease
–Lipid- in small intestines with bile
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Digestion
• Phases
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Ingestion
Movement
Digestion
Absorption
Further digestion
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Terms to know
• Alimentary canal – 30-33 ft. long, runs from
mouth to anus
• Digestion – chemical breakdown of nutrients
(begins in mouth, but mostly in stomach)
• Ingestion – taking in of nutrients through the
mouth
• Absorption – passing of materials through
alimentary wall to bloodstream
• Defecation – release of solid waste through anus
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Phases of Digestion
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Digestive System Organization
• Gastrointestinal (Gl) tract (Alimentary canal)
– Tube within a tube
– Structures
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Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum
Anus
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Digestive System Organization
• Accessory structures
– Not in tube path
– Organs
• Teeth
• Tongue
• Salivary glands
• Liver
• Gall bladder
• Pancreas
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Anatomy of the Mouth and
Throat
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Human Deciduous and
Permanent Teeth
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Dorsal Surface of the Tongue
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The Major Salivary Glands
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Deglutition
• Deglutiton – act of
swallowing
• Peristalsis – wavelike contractions
that move the
nutrients
• Uvula – bundle of
nerves to alert
throat that food is
entering
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Deglutition
• Pharnyx – common passageway for food
and air.
– Branches into trachea (air) and esophagus
(food and liquid)
• Epiglottis – flap that blocks either tube to
prevent materials from going down the
wrong tube. (If this doesn’t work you
choke.)
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Esophagus
• Usually collapsed (closed)
• Functions
– Carry food and liquid to stomach through peristalsis
• Features
– Long, hollow muscular tube
– Dimensions – 2cm by 25 cm
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Peristalsis and Segmentation
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Stomach
• Usually “J” shaped
• Functions – most of chemical breakdown occurs
here
• Rugae – ridges on inside
– allows for increased surface area and increased
expansion
• chyme – slushy mixture – dissolved bolus
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Stomach
• Four regions
– Fundus – upper curve, stores excess bolus for
digestion
– Body – main part of stomach, where digestion
occurs (makes bolus into chime)
– Cardia – upper end, produces mucus to coat
lining of stomach
– Pyloric – last section before small intestine,
where acidity in chyme is neutralized
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Anatomy of the Stomach
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Small Intestine
• Functions – absorption of
nutrients into bloodstream
• Regions
– Duodenum
– Jejenum
– Ileum
• Movements
– Peristalsis
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Small Intestine
• Dimensions – 6m by 4cm-25cm
• Longest part of alimentary canal
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Structure of the Villi in the
Small Intestine
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Small Intestine
• Requires pancreatic
enzymes & bile to
complete digestion
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Large Intestine
• Function – reabsorption of water form chime and
compaction of waste into feces (solid waste)
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Large Intestine
• Regions
– Rectum – storage of feces until release
through anus
– Cecum - appendix
– Colon – has 3 regions, main part of large
intestine
• Ascending
• Transverse
• Descending
– Anal canal
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Anatomy of the Large Intestine
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Feces Formation and Defecation
• Chyme dehydrated to
form feces
• Feces composition
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Water
Inorganic salts
Epithelial cells
Bacteria
Byproducts of digestion
• Control
– Parasympathetic
– Voluntary
• Defecation
– Peristalsis pushes feces
into rectum
– Rectal walls stretch
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Liver
• Functions – blood cell formation, blood
detoxification, bile (emulsifies fats) formation
• Features – lobed, doesn’t grow much from birth
to death
• 4 Lobes
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Left
Quadrate
Caudate
Right
• Each lobe has lobules – Contains hepatocytes –
Surround sinusoids – Feed into central vein
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Liver
– Detoxifies/removes
• Drugs
• Alcohol
– Stores
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Gycolgen
Vitamins (A, D, E, K)
Fe and other minerals
Cholesterol
– Activates vitamin D
– Metabolizes absorbed food
molecules
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The Duodenum and Related
Organs
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Gallbladder
• Functions – storage of bile
• Features – small, pear-shaped organ; found
in lobes of liver; muscular
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Appendix
• Functions – may have been a 2nd stomach;
new research shows it may make digestive
enzymes produced no where else in the
body
• Features – 7-9 cm (varies); redish, wormlike sac; open only at one end; attached to
cecum
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The Organs and Positions in the
Abdominal Cavity
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Structures of the Alimentary
Canal
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Crohn’s Disease
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Acid Reflux
• Stomach acid flows backwards causing
irritation.
• Symptoms – burning pain in the chest after
eating or lying down
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Gastritis
• Inflammation of the stomach lining due to
infection, injury, regular use of NSAIDs,
too much alcohol
• Symptoms - upper stomach pain, nausea,
vomiting
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Ulcers
• A sore on the lining of the esophagus,
stomach, or small intestine
• Caused by damage due to stomach acid
• Symptoms – upper abdominal pain
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Diverticulitis
• Inflammation or infection of the pouches
of the intestine
• More common after 40
• Symptoms – abdominal pain, fever,
nausea, change in bowel movements
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Gastric Bypass surgery
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