the digestive system. stages of food processing ingestion taking in of nutrients digestion breakdown...
TRANSCRIPT
IngestionTaking in of nutrients
DigestionBreakdown of complex organic molecules into smaller components by physical and chemical means
AbsorptionTaking up of digested molecules into the cells of the digestive tract
EgestionRemoval of waste food materials from the body
Humans●Digestive system is one
long tube, open at both ends
●Gastrointestinal tract/alimentary canal
Rat●Very similar to humans – really only size that
varies●One long tube that goes from mouth to anus
Mouth●Digestion begins here●Teeth begin the physical
breakdown of food●Action of chewing
stimulates salivary glands (parotid, sublingual & submandibular)
●Saliva: water, mucus (mucin) & enzymes that breaks down carbs into maltose (amylase)
●Tongue: forms bolus out of food
Neck Area●Pharynx: double purpose
tube – bolus from mouth comes to pharynx to get to digestive tract
●Epiglottis: flap over your airway to make sure food does not go down
●Esophagus: tube that joins the mouth and the stomach. Food moves down by smooth muscle contractions “peristalsis”
Stomach●Movement in and out of the stomach is
controlled by sphincters – like drawstrings on a bag
●Stomach has 3 muscle layers – contract/relax to churn food
●Cells in stomach lining secrete gastric juice (HCl + enzymes) and mucus●HCl + enzymes break down fibrous food●HCl kills foreign invaders●Mucus protects the stomach lining
Stomach●Our stomach is super acidic – without mucus
barrier, our stomach would digest itself●Damage to the mucus – gastric ulcers●Pepsin – breaks down proteins, needs an
acidic environment●Minimal absorption (small amounts of water,
medicine, alcohol)
A Small Detour – the Liver●Produces bile – emulsifying agent – digest fats●Bile contains bile salts that break large fat
globules into small ones●Bile is secreted continuously by the liver and
stored in the gallbladder●Liver stores carbs, vitamins, and is a detox
organ
A Small Detour – the Pancreas●Produces sodium bicarbonate to raise the pH
of chyme from 2.5 to 9.0 (acidic to basic)●Also secretes digestive enzymes such as
lipase (fat digesting), pancreatic amylase (carb digesting), trypsin (protein)
Small Intestine●Duodenum: receives secretions from the
pancreas and the liver●food from the stomach is called chyme –
water, food, gastric juice●UH OH! Chyme is very acidic but the small
intestine can’t handle it...what do we do?●Thankfully, the pancreas secretes sodium
bicarbonate to raise the pH●Structure contains ridges and folds as well as
villi and microvilli to increase surface area for absorption.
Small Intestine●Secretes maltase (converts maltose to
glucose)●Secretes peptidases (complete digestion of
protein – amino acids)●Once digestion is complete, the products are
ready to be removes from the digestive tube and transported
●Most absorption takes place in the small intestine – villi increase surface area, microvilli further increase surface area for absorption
●Lacteals transport materials
Large Intestine (aka Colon)●Shorter than the small
intestine but larger in diameter
●Absorbs usable materials – primarily water
●Has bacteria that produce vitamin K and some B
●Cellulose (from plants) reaches large intestine pretty much undigested
●Feces = cellulose, living/dead bacteria, water
●As waste builds up, CNS prompts to void the waste
Rectum and Anus●Bowel (large intestine) movements propel
waste through the rectum and anus●Allow our bodies to get rid of potentially very
toxic wastes
Where does Homeostasis fit?●Seeing, smelling, tasting, thinking about food will
stimulate glands to produce hormone secretions●Stimulation of salivary glands – saliva●Gastrin (hormone) stimulates gastric juice release●Secretin (hormone) travels to the pancreas to
initiate release of sodium bicarbonate●Large meal – more forceful stomach contractions,
faster emptying●Fatty meal – slow peristalsis – more time for fat
digestion and absorption – feel full longer after a high fat meal
Case Study●Jess came to the hospital with significant
weight loss and fever. ●She was also was bleeding from the rectum
(both red and black)●She was found to be anemic●What’s wrong?
Let’s look at her symptoms:●Weight loss
● If she’s eating properly, something may be wrong with her digestive system
● Ideas?●Fever
● Infection● Inflammation (body trying to attack invader)
●Rectal bleed● Red – small intestine● Black – large intestine
●Anemia● Low iron● Nutrients may not be getting where they need to go?
How do we figure out the cause?●Blood tests – anemia●Colonoscopy – insert camera into the anus –
look for inflammation or bleeding in the large intestine
●Upper Gastrointestinal examination – look at small intestine ●patient drinks Barium solution that coats lining
of the small intestine ●shows up white on X-ray film to show
abnormalities or inflammation
Crohn’s Disease●Chronic inflammation of the intestines●Causes ulcers●Can affect anywhere in the digestive system●Kids can have stunted growth and
development●Treatment: correct nutritional deficiencies,
relieve symptoms●Treatment: drugs, nutrition supplements,
surgery, combination●NO CURE! Chronic means will act up again
and again
Other Digestive System Disorders●Appendicitis - appendix●Tape Worm – stomach/intestine●Dysentery - intestine●Gallstones – gallbladder, liver, pancreas●Gingivitis - mouth●Hiatus Hernia - stomach
Digestive System●Our digestive system is an open ended tube
that starts at the mouth and ends at the anus●It is necessary to receive nutrients to keep our
bodies running with the energy that we need●Each area of the digestive system has a
particular role to play in the big picture●The nervous and endocrine systems control
the actions of the digestive system in various ways