Transcript Digestion, Absorption, & Transport

Digestion, Absorption, &
Transport
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Digestion & The Digestive
System
 Digestion- the process by which food is broken
down into absorbable units.
 Digestive system- all the organs and glands
associated with the ingestion and digestion of
food.
 GI tract- the gastrointestinal tract.
Gastro- stomach.
Intestinalis- intestine.
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Anatomy Of The
Gastrointestinal Tract
Mouth- chews and mixes food with saliva.
Salivary glands- secrete saliva.
Epiglottis- cartilage in the throat that guards the
entrance to the trachea. Protects airway
during swallowing.
Trachea (windpipe)- allows air to pass to and
from the lungs.
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Anatomy Of The
Gastrointestinal Tract {continued}
Esophagus (food pipe)- passes food from the mouth
to the stomach.
Cardiac sphincter (lower esophageal sphincter)allows passage from the esophagus to stomach.
Prevents backflow from the stomach.
* Sphincter- a circular muscle surrounding, and able to
close, a body opening. They are found at specific points
along the GI tract and regulate the flow of food particles.
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Anatomy Of The
Gastrointestinal Tract {continued}
Stomach- adds acid, enzymes, and fluid. Churns,
mixes, and grinds food to a liquid mass.
Pyloric sphincter- allows passage from stomach to
small intestines. Prevents backflow from small
intestines.
Liver- manufactures bile salts, detergent-like
substances to help digest fats.
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Anatomy Of The
Gastrointestinal Tract
{Continued}
Gallbladder- stores bile until needed.
Bile duct- conducts bile from the gallbladder to the
small intestine.
Ileocecal valve- allows passage from the small to
large intestine. Prevents backflow from the colon.
Appendix- stores lymph cells.
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Anatomy Of The
Gastrointestinal Tract {continued}
Small intestine- A 10 ft. length of small diameter
intestine that is the major site of digestion of food
and absorption of nutrients. Its segments include
the duodenum, jejunum, and ileum.
Pancreas- a gland that secretes digestive enzymes
and juices into the duodenum.
Pancreatic duct- conducts pancreatic juice from the
pancreas to the small intestine.
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Anatomy Of The
Gastrointestinal Tract {continued}
Large intestine (colon)- reabsorbs water and
minerals. Passes waste along with water to the
rectum. Its segments include the ascending,
transverse, descending, and sigmoid colon.
Rectum- stores waste prior to elimination.
Anus- the terminal sphincter of the GI tract. Opens
to allow elimination.
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Muscular Actions Of
Digestion
Peristalsis- wavelike muscular
contractions of the GI tract that push its
contents along.
Stomach action- contains circular,
longitudinal, and diagonal muscles that
contract and relax to force the chyme
downward to the pylorus.
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Muscular Actions Of
Digestion {continued}
 Segmentation- periodic squeezing or partitioning
of the intestine at intervals along its length by its
circular muscles.
 Sphincter contractions- four major sphincter
muscles divide the GI tract into its principal
divisions. Contraction of these sphincters allows
food to pass along the entire length of the GI
tract.
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Secretions of Digestion
The five organs which produce secretions
during digestion:
Salivary glands
Stomach
Pancreas
Liver (via gallbladder)
Small intestine
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The Salivary Glands
Secrete saliva into the mouth and begin
the digestive process
Its principal enzyme, amylase, begins
carbohydrate metabolism.
Saliva contains water, salts, and enzymes.
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The Stomach
 Cells in the stomach produce gastric juice
which is a mixture of water, enzymes, and
hydrochloric acid.
 Gastric gland are also referred to as exocrine
glands.
 The major digestive event of the stomach is
the partial breakdown of proteins.
 Gastro = stomach
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Pancreatic Juice And
Intestinal Enzymes
 Pancreatic juice is the exocrine secretion of
the pancreas, containing enzymes for the
digestion of carbohydrate, fat, and protein.
 The pancreas contributes digestive juices by
way of ducts leading to the intestines.
 In addition to enzymes, pancreatic juice also
contains sodium bicarbonate to neutralize the
acid chyme from the stomach.
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The Liver
The liver produces bile which is stored in the
gallbladder.
Bile flows from the gallbladder to the
duodenum.
Bile emulsifies fat for absorption.
* an emulsifier is ...
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Anatomy Of The Absorptive
System
Absorption- the passage of nutrients
from the GI tract into either the blood
or lymph.
Villi- fingerlike projections from the
folds of the small intestines.
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Anatomy Of The Absorptive
System
{continued}
Microvilli- tiny, hairlike projections on each
cell of every villus that trap nutrient
particles and transport them into the cells.
Crypts- tubular glands that lie between the
intestinal villi and secrete intestinal juices
into the small intestines.
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Overview of Macronutrients
And Their Digestive Fate
Mouth
• Carbohydrate
digestion
begins.
Stomach
• Carbohydrate
digestion continues.
• Protein digestion
begins.
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Overview of Macronutrients
And Their Digestive Fate
Small Intestines
• Starch
digestion/absorption is
completed.
Large Intestines
• Fluid reabsorbed.
• Some fibers continue
digestion.
• Fat is emulsified and
absorbed.
• Some fibers pass
through the large
• Protein digestion/
intestine and get
absorption is completed.
excreted.
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Hormones
 Hormones- chemical messengers secreted by a
variety of glands in response to altered conditions.
 They travel to target tissues or organs where they
elicit a specific response to maintain homeostasis.
 Homeostasis- the maintenance of constant
internal conditions by the body’s control systems.
 Homeo = the same.
 Stasis = staying.
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Gastrointestinal Hormones
Gastrin- the hormone secreted by the cells
of the stomach wall. Gastrin stimulates
the stomach glands to secrete the
components of hydrochloric acid.
Hydrochloric acid (HCL)- an acid
composed of hydrogen and chloride
atoms.
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Hormones Of The Small
Intestines
 Secretin- produced by cells in the duodenum wall.
Target organ is the pancreas. Response is the
release of bicarbonate-rich pancreatic juice.
 Cholecystokinin (CCK)- produced by cells of the
intestinal wall. Target organ is the gallbladder.
Response is the release of bile and slowing of GI
motility.
 Gastric-inhibitory peptide- produced by the intestine.
Target organ is the stomach. Response is slowing 22the
secretion of gastric juice and slowing of GI motility.
Common Digestive
Problems
 Choking- when food has slipped into the air passage
(trachea) and breathing has been blocked.
 Vomiting- when the waves of peristalsis reverse
direction and the stomach contents are propelled up
the esophagus and out of the mouth. Arising from a
variety of situations.
 Diarrhea- characterized by frequent loose, watery
stools. Indicating that the intestinal contents have
moved too rapidly through the intestines for fluid
absorption to take place. This can be a symptom of
a
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variety of medical conditions.
Common Digestive Problems
{continued}
 Constipation- longer than usual time between
bowel movements and there is difficulty, pain, or
discomfort when having a bowel movement.
Each person’s GI tract responds differently to
food, digestion, absorption, and transport.
 Heartburn- a painful sensation a person feels
when the cardiac sphincter fails to prevent the
contents of the stomach from refluxing into the
esophagus.
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Strategies For Prevention Of
Common GI Problems
 Choking
 Take small bites.
 Chew thoroughly.
 Don’t talk with food
in your mouth.
 Diarrhea
 Rest.
 Drink plenty of fluids
to replace losses.
 Seek medical
attention if problem
persists.
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Strategies For Prevention Of
Common GI Problems {continued}
 Constipation
 Eat a high fiber diet.
 Drink plenty of fluids.
 Exercise regularly.
 Do not delay
defecation.
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Strategies For Prevention Of
Common GI Problems {continued)
 Heartburn
 Eat small meals
 Follow a low fat diet
 Sit up while eating
 Drink liquids in between
meals
 Wait 1 hour after eating
before lying down
 Wait 2 hours before
exercising
 Refrain from smoking
 Obtain a healthy weight27