Fon 241 Chapter 3
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Transcript of Fon 241 Chapter 3
FON 241; Digestion: L. Zienkewicz
Digestion, Absorption, and Transport
Chapter 3
FON 241; Digestion: L. Zienkewicz
To become part of your body, food must first bedigested and absorbed.
FON 241; Digestion: L. Zienkewicz
Digestion: The process by which food is broken down into absorbable nutrients
Absorption: The passage of nutrients from the GI tract into either the blood or the lymph
FON 241; Digestion: L. Zienkewicz
Anatomy of the gastrointestinal (GI)
tract:
FON 241; Digestion: L. Zienkewicz
The Gastrointestinal Tract
Stomach
Upper esophageal sphincter
Rectum
Pharynx
Small intestine(duodenum, jejunum, ileum)
Esophagus
Pancreatic duct
Anus
Large intestine (colon)Appendix
Liver
Loweresophagealsphincter
Epiglottis
Salivary glands
Trachea (to lungs)
Mouth
PancreasGall bladder
Pyloric sphincter
Bile duct
Ileocecal valve
Liver
Appendix
Rectum
Anus
Loweresophagealsphincter
FON 241; Digestion: L. Zienkewicz
Start at the beginning…
The mouth- Teeth crush your food; saliva blends with the food.
FON 241; Digestion: L. Zienkewicz
The TeethIncisors have chiselededges that cut
Canines (cuspids) havepointed crowns that tear
Premolars (bicuspids)and molars have ridgedsurfaces that crushand grind
Tongue
FON 241; Digestion: L. Zienkewicz
The Teeth
Enamel
Root
Neck
Root canal
Blood vesselsand nervesin pulp
Dentin
Pulp cavity
Gum (gingiva)
Bone
Crown
FON 241; Digestion: L. Zienkewicz
Digestion:
Pharynx- Tube shared by the digestive and respiratory systems.
Epiglottis- Cartilage that prevents food from entering the lungs during swallowing.
FON 241; Digestion: L. Zienkewicz
Normal Swallowing and Choking
Larynx rises
Food
Tongue
Esophagus (to stomach)
Trachea (to lungs)Epiglottis closesover larynx
FON 241; Digestion: L. Zienkewicz
Next… Esophagus- the food pipe; a long tube that
carries a food bolus from the pharynx to the stomach.
Preventive measures: Esophageal sphincters two sphincters on each end of the esophagus.
They function to: 1. Upper ES- allow food into the esophagus2. Lower ES- allow food into the stomach
and prevents backflow of stomach contents.
FON 241; Digestion: L. Zienkewicz
An Example of a Sphincter Muscle
Esophagus muscles contract,squeezing on the inside.
Esophagus muscles relax,opening the passageway.
Diaphragm muscles relax,opening the passageway.
Longitudinal muscle
Esophagus
Diaphragm muscles contract,squeezing on the outside.
When the circular muscles of a sphincter contract, thepassage closes; when they relax, the passage opens.
Circular muscle
Stomach
FON 241; Digestion: L. Zienkewicz
FON 241; Digestion: L. Zienkewicz
What happens in the stomach?
• A bolus enters the stomach via the lower esophageal sphincter.
• The stomach gradually transfers the bolus from the upper portion to the lower portion of the stomach.
• Stomach acids are added and the food is ground by muscular forces
• The bolus is now called chyme.
• The stomach slowly releases chyme through the pyloric sphincter into the small intestine.
FON 241; Digestion: L. Zienkewicz
Stomach Muscles
Circular
Diagonal
Longitudinal
The stomach has three layers of muscles.
FON 241; Digestion: L. Zienkewicz
Still going…• Small intestine: Made of three
parts- 1. The duodenum2. The jejunum3. The ileum
In beginning of the small intestine, fluids from the gallbladder and pancreas, flow through the common bile duct and interact with the chyme. The chyme then moves through the 3 parts of the small intestine.
FON 241; Digestion: L. Zienkewicz
The Small Intestine
Pyloric Sphincter
FON 241; Digestion: L. Zienkewicz
The surface area of the small intestine is roughly the size of a tennis court.
FON 241; Digestion: L. Zienkewicz
And going… through the large intestine• Chyme passes through the Ileocecal valve, the
entrance to the large intestine.
• Chyme bypasses the appendix.
• Chyme travels through the large intestine; water is withdrawn and a semi-solid mass forms.
• The mass moves to the rectum; rectal muscles relax.
• 2 sphincters of the anus relax, thus passing the mass through the anus.
FON 241; Digestion: L. Zienkewicz
The Colon or Large Intestine
Opening from smallintestine to large intestine
Transverse colon
Ascending colon
Anus
Descendingcolon
End of small intestine
Appendix
Rectum
Sigmoid colon
FON 241; Digestion: L. Zienkewicz
The whole picture:
Large Intestine
Small Intestine
Esophagus
Stomach
FON 241; Digestion: L. Zienkewicz
The Digestive Fate of a Sandwich
STOMACH: COLLECTING AND CHURNING, WITH SOME DIGESTION
MOUTH: CHEWING AND SWALLOWING, WITH LITTLE DIGESTION
FON 241; Digestion: L. Zienkewicz
The Digestive Fate of a Sandwich
LARGE INTESTINE: REABSORBING AND ELIMINATING
SMALL INTESTINE: DIGESTING AND ABSORBING
FON 241; Digestion: L. Zienkewicz
How does food move through?
• Peristalsis- wavelike muscular contractions that push contents along.
• Segmentation- the circular muscles of the small intestine rhythmically squeeze and contract the contents; chyme is mixed with digestive juices, etc.
• Sphincter contractions- opening and closing of a sphincter to allow contents to enter or exit.
FON 241; Digestion: L. Zienkewicz
Peristalsis and Segmentation
FON 241; Digestion: L. Zienkewicz
Digestive Secretions:
Source Secretion
Salivary Glands SalivaStomach Gastric juice
Pancreas Pancreatic
juiceLiver (via gallbladder) BileSmall intestine Intestinal Flora
FON 241; Digestion: L. Zienkewicz
The Salivary Glands
Salivary glands
FON 241; Digestion: L. Zienkewicz
The pH Scale
Basic
Acidic
pH neutral
pH’s of common substances:
Oven cleaner
BilePancreatic juice
Concentrated lye
Battery acid
Gastric juiceLemon juice
Vinegar
Orange juice
Urine
BloodWater
Baking soda
Household ammonia
Saliva
Coffee
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
FON 241; Digestion: L. Zienkewicz
Absorption
• The small intestine:•Villi- Small intestinal projections•Microvilli- Microscopic hairs on the villi •Crypts- crevices between the villi
All of these components make up the massive absorptive area of the intestine.
FON 241; Digestion: L. Zienkewicz
Absorption of Nutrients
Cellmembrane
Absorption of nutrients into intestinal cells typicallyoccurs by simple diffusion or active transport.
Carrier loadsnutrient onoutside of cell . . .
Energy
ACTIVETRANSPORT
FACILITATEDDIFFUSION
SIMPLEDIFFUSION
Energy
. . . and thenreleases it oninside of cell.
Outsidecell
Insidecell
Carrier loadsnutrient onoutside of cell . . .
. . . and thenreleases it oninside of cell.
FON 241; Digestion: L. Zienkewicz
The Small Intestinal Villi
Folds with villi on them
Longitudinal muscles
Circular muscles
Small intestine
Stomach
FON 241; Digestion: L. Zienkewicz
The Small Intestinal Villi
Goblet cells
Capillaries
Vein
A villus
Artery
Crypts
Lymphaticvessel
Lymphatic vessel (lacteal)
(cont’d next slide)
FON 241; Digestion: L. Zienkewicz
The Small Intestinal VilliMicrovilli
FON 241; Digestion: L. Zienkewicz
Nutrient Transport• The nutrient crosses the cell and can…
•1. Enter the blood stream (water soluble)
or•2. Enter the lymphatic system
• Water soluble nutrients and smaller fat products are released into the bloodstream.
• Larger fats, fat-soluble vitamins and turned into chylomicrons and released into the lymphatic system
FON 241; Digestion: L. Zienkewicz
The Vascular System
Heart
= Arteries= Capillaries= Veins= Lymph vessels
Liver
Leftside
Rightside
Hepatic artery
Digestivetract
Portal vein
Lymph
Entire body
Pulmonary vein
Hepatic vein
Pulmonary artery
Head andupperbody
Lungs
Aorta
Digestivetract
Hepatic artery
Portal vein
Aorta
Leftside
Heart
FON 241; Digestion: L. Zienkewicz
The Vascular System• Blood delivers Oxygen and
Nutrients to organs and tissues; CO2 and waste products are carried away by the blood.
• The digestive system supplies nutrients to the blood.
• Heart ArteriesCapillaries
Veins
FON 241; Digestion: L. Zienkewicz
The Vascular System (cont.)
• Blood leaving the digestive system is taken to the liver via a vein.
• The liver is the bodies major metabolic organ.
• It receives nutrients and other products from the digestive system; a gatekeeper.
FON 241; Digestion: L. Zienkewicz
Route of blood from intestines to heart.
Heart Arteries Capillaries
(in intestines)
Vein Capillaries Veins
(in liver)
FON 241; Digestion: L. Zienkewicz
The Lymphatic System:
• A route for fluid from tissue to enter the blood.
• Large fats and fat-soluble vitamins use the lymph system
• Ultimately end up in the heart• Once in the blood stream, the
nutrients can be delivered to cells, organs, etc.
FON 241; Digestion: L. Zienkewicz
Chylomicron: travels via the Lymphatic System
Hydrophilic head
Hydrophobic tail
FON 241; Digestion: L. Zienkewicz
Common GI Problems…
• Choking- improper closing of the epiglottis, food lodged in the pharynx, etc.
• Vomiting- stomach contents expelled; sometimes the contents of the duodenum are expelled.
• Diarrhea- frequent loose stools, lack of absorption and increased water in the intestine; fast motility
• Constipation- inability to defecate
FON 241; Digestion: L. Zienkewicz
Common GI Problems (cont.)…
• Gas- excessive gas in the GI tract• Belching-excessive gas in the stomach• Reflux- relaxation of the lower
esophageal sphincter, causing stomach acid to touch the lining of the esophagus
• Ulcers- erosion of the lining of the GI tract• Diseases of the GI tract………
FON 241; Digestion: L. Zienkewicz
Diverticula in the Colon
Diverticulum (singular)
Diverticula (plural)
Diverticula may develop anywhere along the GI tract,but are most common in the colon.
FON 241; Digestion: L. Zienkewicz
In-text Figure Page 74
Eat a variety of food to keep your gastrointestinal tract happy.