Transcript Human Digestion and Absorption - 35-206-202

HUMAN DIGESTION AND
ABSORPTION
CHAPTER 4
ORGANIZATION OF THE HUMAN BODY
• Chemical Level
• Atoms combine to
form molecules
• Cell Level
• Molecules form
organelles
• Use ATP
• Tissue Level
• Similar cells make up
tissues
ORGANIZATION OF THE HUMAN BODY
• Organ Level
• Different tissues
combine to form
organs
• Organ System Level
• Organs make up an
organ system
• Organism Level
• Organ systems make
up an organism
DIGESTIVE ORGAN SYSTEM
•GI tract
• Mouth, esophagus, stomach, small
intestine, large intestine
•Accessory organs: Liver, pancreas
and gall bladder
DIGESTIVE ORGAN SYSTEM
DIGESTIVE SYSTEM OVERVIEW
• Digestion
• Process of breaking down foods into a form
the body can use
• Absorption
• Uptake of nutrients from the GI tract into
the blood or lymph
ANATOMY OF THE GI TRACT
• GI tract
• Long hollow muscular canal. Nutrients pass
through the wall of the canal to be absorbed
• Four layers (listed from inner most layer to
outermost layer)
• Mucosa
• Submucosa
• Muscle
• Serosa
GI MOTILITY
• Peristalsis
• Contractions of the GI tract, mainly in esophagus,
stomach, and small intestine
• Segmentation
• Back and forth movement-happens in small
intestine so there is mixing with digestive juices
• Mass movements
• Slow peristalsis over widespread area- in large
intestine to help propel fecal matter to rectum
• Elimination
ONE WAY STREET
Sphincters: Ring like muscles along
the GI tract that control the flow of
contents
MOUTH (ORAL CAVITY)
Chewing breaks up food and increases surface
area. These smaller food particles are mixed
with saliva and forms a bolus.
Saliva
• Lysozyme
• Break down bacteria
• Amylase
• Break down starch
• Mucus
• Lubricate and hold bolus together
TASTE AND SMELL
• Taste buds on the tongue and soft palate
• Salty (from metal ions)
• Sour (from acids)
• Sweet (from organic compounds)
• Bitter (many diverse compounds like
phytochemicals)
• Umami or savory (from amino acids)
• Olfactory glands
• Sense of smell (enhances sense of taste)
ESOPHAGUS
• Swallowing
• Moves bolus from the mouth to the esophagus
• Epiglottis
• Prevents food from lodging in the trachea
• Covers the larynx
http://youtu.be/sM6uxd1uS6M
STOMACH
• Bolus goes through lower esophageal sphincter into
stomach
• Mixed with stomach secretions becomes chyme
• Pyloric sphincter allows chyme into the small
intestine
• Gastric inhibitory peptide (hormone) slows release of
chyme into the small intestine to allow time for acid
neutralization and digestion (only one teaspoon is
allowed into the SI at a time).
STOMACH SECRETIONS
Chief cells produce:
• Pepsinogen (an inactive protein-digesting
enzyme)
Other secretions include,
Gastric lipase
• Gastrin
• Hormone stimulated when food is in stomach; controls
release of HCl and pepsinogen and stimulates motility
• Mucus
• Protects the stomach from being digested
STOMACH SECRETIONS
Parietal cells produce hydrochloric acid
which:
• Inactivates proteins
• Destroys bacteria and viruses
• Aids in mineral absorption (dissolves them)
• Converts pepsinogen (protein digesting
enzyme) into pepsin (active form)
SMALL INTESTINE
Most digestion
and absorption
occurs here
Sections:
Duodenum,
Jejunum
Ileum
SMALL INTESTINE
Villi (finger like projections on interior of SI) that are
lined with:
• Goblet cells make mucus
• Endocrine cells produce hormones
• Cells (enterocytes) that produce enzymes for
absorption
HORMONES OF THE SMALL INTESTINE
• Gastrin
• Also released by stomach, stimulates intestinal motility
• Cholecystokinin (CCK)
• Stimulated by dietary fat in chyme, stimulates release of
pancreatic enzymes and bile
• Secretin
• Stimulated by acidic chyme, stimulates release of
pancreatic bicarbonate
• Gastric Inhibitory peptide
• Stimulates stomach to limit gastric juices, slows motility
ACCESSORY ORGANS: LIVER, GALLBLADDER AND
PANCREAS
• Liver
• Provides bile
• Needed to emulsify fat (disperse into droplets and suspend
in water) so it can be absorbed
• Gallbladder
• Bile storage
• Pancreas
• Produces sodium bicarbonate, lipases, proteases and
pancreatic amylase
ACCESSORY ORGANS: LIVER, GALLBLADDER
AND PANCREAS
LARGE INTESTINE
Functions: Absorption of water and
electrolytes, house bacterial flora, and form
and expel feces.
• Colon
• Cecum, ascending colon, transverse colon,
descending colon and sigmoid colon
• Rectum
• Anus
LARGE INTESTINE
ABSORPTION
ABSORPTION
• Passive (fat, water, some minerals)
• High concentration to low
• Facilitated (ex. fructose)
• High concentration to low + carrier protein
• Active (amino acids, glucose)
• Low concentration to higher + energy
• Endocytosis (large proteins like immune
factors)
• Engulfment
ABSORPTION
MOVING NUTRIENTS
• Cardiovascular System
• Includes heart, blood
vessels and blood
• Water-soluble nutrients
transported via capillaries in
villi to portal vein, which
leads to liver
• Allows liver to process
nutrients before entering
general circulation
• Lymphatic System
• Includes lymph
• Fat-soluble nutrients and
large particles transported
via lacteals into the lymph
vessels to thoracic duct,
where it connects to the
blood stream.
BACTERIAL FLORA
• Beneficial bacterial flora
• Controls pathogenic bacteria
• Synthesize Vitamin K and Biotin
• Aid lactose digestion and fermentation
• Pro-biotic
• Live bacteria
• Pre-biotic
• Non digestible carbohydrates that promote the
growth of beneficial bacteria
PUTTING IT ALL TOGETHER
Be able to trace the pathway of food from when
you first eat it until it is eliminated or absorbed
Know the major function of each organ and if it
secretes any major enzymes or hormones
DIGESTION GONE AWRY
Heartburn and Gastroesphogeal reflux
(GERD)
Causes
Overweight, alcohol, smoking, pregnancy
Foods that increase reflux
Citrus, caffeine, chocolate, fatty foods, spicy
foods, onion, garlic and tomato based foods
Medications include
H2 blockers (blocks histamine formation) and
proton pump inhibitors
DIGESTION GONE AWRY
Heartburn and Gastroesphogeal reflux (GERD)
DIGESTION GONE AWRY
Ulcers
Causes:
H pylori, alcohol, aspirin and smoking (not stress)
Treatment:
• Medications (abx, same as GERD)
• Avoid foods that increase symptoms
DIGESTION GONE AWRY
• Gallstones
• Food Intolerances
• Lactose, gluten, MSG
• Intestinal Gas
• Flatulence
• Air and undigested CHO in large intestine
DIGESTION GONE AWRY
DIGESTION GONE AWRY
• Constipation
• Fiber, fluid and exercise
• Laxative use (bulk, osmotic, stimulants, softeners,
and lubricants)
• Diarrhea
• Replace fluid and electrolytes
• Irritable bowel
• Cause unknown, examine dietary factors
• Hemorrhoids