Transcript 38–2 The Process of Digestion

38–2 The Process of
Digestion
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38–2 The Process of Digestion
38–2 The Process of Digestion
The Digestive System
Mouth
Pharynx
Salivary
glands
Esophagus
Stomach
Liver
Pancreas
Gallbladder
Large intestine
Small intestine
Rectum
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38–2 The Process of Digestion
The Mouth
The function of the digestive system is to
convert foods into simpler molecules that
can be absorbed and used by the body.
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38–2 The Process of Digestion
Human Digestive System
• Tongue – taste buds, swallow, help chew
• Teeth – mechanical digestion
• Salivary glands – saliva, lubricate, carb’s
• Pharynx – back of throat, pathways cross
• Esophagus – food tube to stomach
• Epiglottis – covers trachea to prevent choking
• Peristalsis – wave of muscular contractions
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38–2 The Process of Digestion
The Esophagus
Esophagus
Peristalsis:
Bolus
Muscles
contracted
Stomach
The cardiac
sphincter closes
the esophagus
after food has
passed to the
stomach.
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38–2 The Process of Digestion
The Stomach
The Stomach
• Muscular Organ – 3 layers of muscle
• Churns food – mechanical digestion
• Sphincter muscles close off both ends
• Stores food for up to 4 hours
• Digests proteins
• Gastric glands – produce pepsin & HCl
• Chyme – mixture of stomach contents
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38–2 The Process of Digestion
The Small Intestine
The Small Intestine
• Small Int – 20’long, 1” wide, digests all foods
and absorbs all nutrients
• Intestinal glands produce some enzymes
• Villi – fingerlike projections for absorption
• Large Int – 4’ long, 2” wide, absorbs water
• Rectum – stores feces for elimination
• Anus – final sphincter of digestive track
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38–2 The Process of Digestion
The Small Intestine
Accessory Structures of Digestion
Liver
Bile duct
Gallbladder
Pancreas
Duodenum
Pancreatic
duct
To rest of small
intestine
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38–2 The Process of Digestion
The Small Intestine
Accessory Structures of Digestion
• Liver – largest gland in body
• Liver produces bile to assist fat digestion
• Gall Bladder – stores bile, delivers to sm.int.
• Liver stores sugar & fat soluble vitamins
• Pancreas – produces enzymes for all foods
• Also produces insulin to help cells absorb
glucose.
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38–2 The Process of Digestion
The Stomach
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38–2 The Process of Digestion
The Small Intestine
Most chemical digestion and
absorption of food occurs in
the small intestine.
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38–2 The Process of Digestion
Absorption in the Small
Intestine
Absorption in the Small Intestine
Villi - fingerlike projections of the small
intestine.
They provide an enormous surface area.
Nutrients are absorbed into the cells lining
the villi.
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38–2 The Process of Digestion
Absorption in the Small
Intestine
The Small Intestine
Villus
Small intestine
Circular folds
Epithelial
cells
Villi
Capillaries
Lymph
vessel
Vein
Artery
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38–2 The Process of Digestion
The Large Intestine
The Large Intestine
The large intestine absorbs water from the
chyme.
Concentrated wastes are stored in the rectum.
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38–2 The Process of Digestion
Digestive System
Disorders
•Ulcer – hole in stomach or intestines
•Appendicitis – infection of appendix
•Gallstones – cholesterol in gall bladder
•Malnutrition – over, under, poor (deficiencies)
•Obesity – overweight, 25% US population
–Leads to health problems:diabetes, heart disease
•Anorexia – severe underweight
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38–2
Food is moved through the esophagus into the
stomach by
a. air pressure.
b. muscle contractions.
c. gravity.
d. swallowing.
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38–2
A gland that has both endocrine and exocrine
functions is the
a. liver.
b. spleen.
c. pancreas.
d. gallbladder.
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38–2
The enzyme in saliva that begins the digestion
of starch is
a. amylase.
b. pepsin.
c. lysozyme.
d. peptidase.
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38–2
Stomach muscles contract to churn and mix
stomach fluids and food, producing a mixture
known as
a. chyme.
b. amylase.
c. bile.
d. acid.
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38–2
Absorption of vitamins, minerals, and digested
food molecules takes place in the
a. stomach.
b. small intestine.
c. large intestine.
d. duodenum.
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