Download The Digestive System

The Digestive System
Functions of Digestive System
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Take in food
Breakdown food into nutrients
Absorb nutrients into bloodstream
Get rid of indigestible remains
Parts of Digestive System
Parts of Digestive System
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Alimentary Canal
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Continuous, muscular tube that starts at the mouth and ends
at the large intestine
Accessory Digestive Organs
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Organs not directly part of the canal that help with digestion
such as teeth, gall bladder, liver, pancreas, or salivary gland
Digestive Process
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Ingestion
Propulsion
Mechanical Digestion
Chemical Digestion
Absorption
Defecation
Digestive Process
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Ingestion
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Taking in of food usually in the mouth
Propulsion
Mechanical Digestion
Chemical Digestion
Absorption
Defecation
Digestive Process
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Ingestion
Propulsion
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Movement of food through alimentary canal either voluntarily
(swallowing) or involuntarily (peristalsis)
Mechanical Digestion
Chemical Digestion
Absorption
Defecation
Digestive Process
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Ingestion
Propulsion
Mechanical Digestion
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Physical breakdown of food in preparation for chemical
digestion and includes chewing, mixing, and churning
Chemical Digestion
Absorption
Defecation
Digestive Process
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Ingestion
Propulsion
Mechanical Digestion
Chemical Digestion
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Enzymes breakdown complex food molecules into simpler
building blocks (nutrients)
Absorption
Defecation
Digestive Process
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Ingestion
Propulsion
Mechanical Digestion
Chemical Digestion
Absorption
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Passage of nutrients into the bloodstream
Defecation
Digestive Process
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Ingestion
Propulsion
Mechanical Digestion
Chemical Digestion
Absorption
Defecation
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Eliminates indigestible material through the anus in the form of
feces
Anatomy of the Digestive
System
The Mouth
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Mucus-lined cavity that takes in food
The Mouth
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Lips and Cheeks
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Core of muscles covered by skin
Helps keep food in between teeth when chewing
Palate
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Roof of the mouth that separates the oral and nasal cavities
made up of two regions – hard and soft
The Mouth
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Tongue
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Made up of skeletal muscles that mixes food and saliva into the
bolus and initiates swallowing
Salivary Glands
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Glands around the oral cavity that secretes saliva
Anatomy of the Digestive
System
The Mouth
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Teeth
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Hard structures that help us masticate
Types
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Incisors: Front teeth adapted for cutting
Canine: adapted for tearing and piercing
Premolars/Molars: back teeth adapted for grinding
The Mouth
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Tooth Structure
Crown
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Exposed part of the tooth that is covered in enamel
Root
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Imbedded in the gums and jaw bone.
Anchors the tooth
Pharynx
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Mucus-coated passage between the mouth and esophagus
Anatomy of the Digestive
System
Esophagus
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Muscular tube that is collapsed when not propelling food
Anatomy of the Digestive
System
Stomach
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Muscle-lined storage tank where chemical digestion
begins
Major Regions of Stomach
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Cardia: upper portion
Fundus: curved upper portion
Body: mid-region
Pyloric Region: lower region
Pyloric Sphincter: separates stomach and small intestine
Small Intestine
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Major digestive organ made up of twisted tubing
Most absorption happens here
Small Intestine: Regions
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Duodenum
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Jejunum
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First part that is immovable
Bile and pancreatic ducts here
8 foot middle region
Ileum
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12 feet that lead into large intestine
Liver
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Lobed gland that makes bile
Gall Bladder
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Thin-walled, green sac lined with muscles that secretes
bile
Pancreas
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Gland in between the stomach and duodenum that
secretes pancreatic juice directly into duodenum
Large Intestine
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Larger tubing that absorbs water
Regions
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Cecum: first, sac-like region
Appendix: small mass of lymphoid tissue
Colon: largest portion with three parts
Rectum: end portion of large intestine
Anal Canal: contains two sphincters that function during
defecation
Part II:
Digestive System
Physiology
Overview
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II.
III.
IV.
Mouth, Pharynx, and Esophagus
Stomach
Small Intestine
Large Intestine
I. Mouth, Esophagus, and Pharynx
Food breakdown
Mechanical digestion
Chewing- breaks food down to make chemical digestion easier
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B. Chemical digestion
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Saliva- enzymes which start to break down food molecules
Salivary Amylase: breaks down starches into simpler sugars
(ex: Potato chips)
II. Mouth, Esophagus, and Pharynx:
Food Propulsion
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Swallowing: Tongue forces the food (bolus) into the
pharynx
Peristalsis: involuntary waves of contraction move food
along
I. Mouth, Esophagus, and Pharynx
Why we can swallow without choking
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The trachea (air passage) is anterior to the pharynx
(digestive tract)
Epiglottis: flap of tissue that extends from pharynx to
cover trachea
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Choking: epiglottis malfunctions, food goes down air passage
I. Mouth, Esophagus, and Pharynx:
How food exits
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Cardioesophageal
Sphincter
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Opens when food presses
upon it and allows the food
into the stomach
II. Stomach:
Food Breakdown
A. Chemical Digestion
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Breaks down proteins (not lipids or carbohydrates)
B. Mechanical Digestion
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muscular lining of the stomach causes contractions which
breaks down food into smaller particles
II. Stomach:
Food Breakdown
C. Gastric Juices
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Hormones and nerves regulate the release of digestive juices
when food enters stomach
Contain
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Hydrochloric acid
Protein-digesting enzymes
mucus
II. Stomach:
Food Breakdown
D. Mucus Lining
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Epithelial cells that line the stomach release mucus as
protection against the harsh acids
II. Stomach:
Food Propulsion
A. Chyme
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End product of the stomach that is liquid with very small
particles
B. Pyloric Sphincter
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Opens and closes to allow chyme into the duodenum
III. Small Intestine:
Breakdown & Absorption
A. Chyme in the Duodenum
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So far food is only partially digested with none absorbed.
Digestive enzymes are dumped by accessory organs and mixed
with the chyme
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Pancreas: produces/secretes pancreatic juices
Liver: produces bile
Gall bladder: contracts to secrete bile into duodenum
III. Small Intestine:
Breakdown and Absorption
B. Digestive Fluid
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Pancreatic Juices
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Finish starch digestion started in mouth
Half of protein digestion started in stomach
All of fat digestion
All of nucleic acid digestion
Bile
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Breaks fats into smaller pieces
III. Small Intestine:
Breakdown and Absorption
C. Absorption: Process
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Smaller food particles are actively transported across the
membrane into bloodstream
D. Absorption: Microvilli Lining
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Increases the amount of blood capillaries that are able to
absorb nutrients
What are microvilli?
III. Small Intestine:
Food Propulsion
Peristalsis
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Segments of the small intestine contract and relax to push
chyme through
IV. Large Intestine:
Breakdown and Absorption
Digestive Enzymes
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No digestive enzymes are secreted into the colon
B. Bacteria
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Bacteria in the colon breakdown remaining nutrients and
produce some vitamins
IV. Large Intestine:
Breakdown and Absorption
C. Water
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Water is reabsorbed into the body
D. Feces
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More or less solid product of undigested materials that goes
into the rectum
IV. Large Intestine:
Defecation
A. Peristalsis
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Slower in the colon than in the rest of the digestive tract
B. Mass movements
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Long, slow-moving contraction waves that move over the
entire length of the colon to empty it into the rectum
IV. Large Intestine:
Defecation
C. Defecation Reflex
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After mass movements, the colon and rectum contract moving
contents into anal canal
Pause to allow voluntary control of external sphincter
**Closer Look at Small Intestine**
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1. Mucosa- intestine wall
2. Villi (in jejunum)- finger-like projections made of
epitheleal cells
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High surface area Æ efficient absorption
3. Capillary- blood supply
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Adjacent to villi
Nutrients diffuse across villi directly into capillary.