Transcript digestion - gozips.uakron.edu

DIGESTION
ABSORPTION
GI
TRACT
ANATOMY OF GI TRACT
MOUTH
Chewing  surface area of food
Mixes fluid (saliva) in with food
Taste
Ease of swallowing
CHO digestion (amylase) NO digestion of
fibers and sugars
Epiglottis prevents choking
cartilage in throat to close off
windpipe
NORMAL SWALLOW STAGES
ORAL PHASE- food bolus moves to back
of mouth (voluntary)
PHARYNGEAL PHASE – triggering of the
swallow (reflexive stage)
ESOPHAGEAL PHASE – actual swallow
(reflexive)
DYSPHAGIA - SYMPTOMS
ORAL PHASE
drooling
pocketing
facial droop
inadequately chewed foods
food falling out of the mouth
excessive tongue movement
DYSPHAGIA CONT’D
PHARYNGEAL PHASE
“Gurgling” voice
food getting stuck
nasal regurgitation
delayed swallowing reflex
coughing while eating or drinking
TEST OF SALIVARY SECRETIONS
GI TRACT
BOLUS – mouthful of swallowed food
PERISTALSIS –
powerful rhythmic waves
propels food along
circular and longitudinal muscles
speed varies
PERISTALISIS
ESOPHAGUS TO STOMACH
Esophagus  diaphragm
Cardiac sphincter – 1 way valve between
esophagus and stomach
Stomach
CHO digestion stops in the stomach
Saliva – is a protein and is digested
Problems:
Hiatal hernia
GERD
Heartburn – acidic stomach contents into
esophagus
HERNIA
GERD
STOMACH
Muscular, elastic, saclike, thickest walls,
strongest muscles in GI tract
Parietal cells on wall release Gastrin
Gastrin stimulates release of HCl (1.5-1.7 pH)
HCl denatures protein
HCl activates pepsinogen (enzyme)  pepsin
Pepsin  large proteins smaller amino
acids
Digestion of protein – little else
STOMACH
Churning
circular
longitudinal
diagonal
Food mixed with water ~ 2 liters per day
Chyme (“kime”) – very acidic
semiliquid mass of partly digested food and
fluid
Stomach protected by mucus membrane-from
goblet cells
STOMACH
pH VALUES
STOMACH SURGERY
PYLORIC SPHINCTER
Circular muscle-1 way valve
Opens 3 times/minute
Waits to re-open until chyme
neutralized
Chyme released in small squirts
Neutralized by bicarbonate from
pancreas
SMALL INTESTINE
Three segments
Duodenum
Jejunum
Ileum
Digestion completed for CHO, PRO, Fat
Pancreatic enzymes-specific to need
proteases, lipases, carbohydrases
Intestinal enzymes
Bile (emulsifier)-livergallbladder
SMALL INTESTINE - ABSORPTION
Microvilli- fingerlike projections
Crypts – secrete digestive enzymes
Specific areas for absorption of specific
nutrients- absorption of most nutrients
Absorbed into lymph or blood
BLOOD – liver via portal vein
LYMPH – bloodstream via thoracic duct
and subclavian vein
SMALL
INTESTINAL
VILLI
ABSORPTION OF NUTRIENTS
Diffusion – freely crosses cell membrane
Facilitated diffusion – specific carriers
required but no energy
Active transport – requires carriers and
energy
ILEOCECAL VALVE
One way valve between small and
large intestine
ABSORPTION
SITES
LARGE INTESTINE
Colon – three segments
Ascending colon
Transverse colon
Descending colon
Normal bacterial action
Fiber  kcals
Vitamin K + others?
Absorption
water and some minerals
LARGE INTESTINE FUNCTION
Food in large intestine 20-36 hours
Water reabsorbed – if not diarrhea
Home for bacteria
Feces formed here
Few minerals absorbed
STOMAS
CROSSSECTION
THE END
Rectum – semisolid waste (feces)
Defecation – elimination of waste from
body – “moving of bowels”
Anus – terminal sphincter, opens to
outside of body – YOU control this valve