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1. Pharynx cavity not involved in digesting food passageway leads to stomach
connection between nasal & oral cavities to larynx & esophagus
3 parts to pharynx1. nasopharynx- connects w/
nasal cavity2. oropharynx- passageway
food moving down & air moving into trachea
3. laryngopharynx- passageway to esophagus
3 Stages of Swallowing
1st stage: › voluntary › food chewed- mixed w/ saliva
› rolled into mass by tongue- BOLUS- forced into pharynx
2nd Stage- swallowing reflex stimulated
food is prevented entrance to nasal cavity
epiglottis slaps shut over larynx to keep food from going down trachea
tongue seals off oral cavity different muscle actions open
esophagus & forces food down it
epiglottis
trachea
3rd Stage
breathing momentarily inhibited peristalsis transports food down into &
through esophagus
choking occurs when food lodges in larynx
Heimleich maneuver can dislodge food
Heimleich maneuver
2. Esophagus straight tube ~ 25 cm long food passageway from pharynx to
stomach goes thru opening in diaphragm contains mucous glands w/
secretions that moisten & lubricate inner lining
Peristalsis
wavelike motion propels food down tubular structures
contraction of muscle occur above food & relaxation below it
hiatal hernia acid reflux Barrett’s esophagus
Caution!
3. Stomach j-shaped, pouched organ ~ 1 L capacity fxns: receives food from
esophagus, mixes food w/ gastric juices, begins protein digestion, limited absorption, moves food into small intestines
Regions of stomach:
1. cardiac-2. fundus- temp storage area3. body- main part4. pylorus- approaches small
intestines
inner lining contains gastric glands w/ 3 types secretory cells:A. mucous cells- secrete mucus w/ other
secretions keeping stomach from digesting itself
B. chief cells- secrete digestive enzymes- pepsinogen
C. parietal cells- release HCl & intrinsic factors
all these form GASTRIC JUICE (2-3 L/day)
Ulcer
inner lining= RUGAE- disappears when stomach is distended
ulcer is open sore in the lining of stomach
may be caused by presence of H pylori bacteria
pepsinogen is released & when hits HCl forms PEPSIN which digests almost ALL types of protein
intrinsic factors aid in vitamin B12 absorption in small intestines
mostly digestion occurs in stomach, but some absorption of water, salts, and drugs does occur
mechanical & chemical digestion begin here
resulting in a semi-paste called CHYME
rate at which this enters sm intestine depends of type of food liquids pass thru quicklyfatty foods 3-6 hoursproteins & carbs pass thru more quickly
Vomiting medulla oblongata-
vomiting center body prepares for the
process by closing off nasal cavity, trachea, contraction of diaphragm, contraction of abdominal muscles, etc
4. Pancreas dual fxn- endocrine gland &
digestive gland closely associated w/ small
intestine in the curve of duodenum
fxn: release pancreatic juice juice contains enzymes that digest
carbs, fats, nucleic acids, proteins
PANCREATITIS- condition where there is a blockage in release of juice
essentially pancreas digests itself
5. Liver & Gallbladder
largest internal organ in body inferior to diaphragm on right
side of body (under ribs) 4 lobed organ (2) connected to sm intestines by
ducts main fxn: manufacture bile salts
Functions:
imp role in carb metabolism› regulates glucose in bld
imp in lipid metabolism- converting subst into fats (bile salts)
imp in protein metabolism
produce plasma proteins
destroy bacteria/old rbc & wbc
produce enzymes that break down poisons that are harmful to body
stores certain vitamins/minerals needed by body
also stores poisons that can’t be broken down & excreted
activates vitamin D
Diseases of Liver
cirrhosis hepatitis cancer
surrounds gallbladder- small, green sac embedded in liver
stores & concentrates bile
gallstones gallbladder attacks
6. Small Intestine major digestive organ ~ 21 feet long 3 subdivisions:
A. duodenum- ~10” long (25cm)diameter: ~ 2” (5cm)C-shaped around the pancreas
B. jejunum- ~ 8’ longgreater diameterthicker walls, more vascularized
C. ileum- ~ 12’ longhard to distinguish between jejunum
& ileum
mesentery- thin membrane that suspends the portions of the intestines from walls
contains blood vessels, nerves, lymphatic vessels
only processes small amount of food at a time so pyloric sphincter muscle considered gatekeeper
produces enzymes to digest food (w/ help of pancreatic enzymes & bile)
enzymes secreted by mucosal cells break down proteins, carbs, fats
wall of intestine has many tiny projections called villi
microvilli project off the villi
the epithelial lining is replaced every 3 to 6 days
food absorption occurs thru these structures
carries on mixing movements & peristalsis
chyme moves slowly; 3-10 hours
if wall becomes distended/irritated, a peristaltic rush pushes contents to large intestine so quickly that water, nutrients, & electrolytes aren’t absorbed - diarrhea
8. Large Intestine
~ 5’ length greater diameter than small int fxns:
1. dry out indigestible food residue by absorbing water2. eliminate residues from body as feces
little or no digestive fxns no secretions except mucus by goblet
cells in wall› protects inner wall› binds fecal matter
normally absorbs water & electrolytes many bacteria, intestinal flora, inhabit
organ (100 trillion) help break down substances that aren’t
by our digestive system
4 principle regions:1. cecum- beginning; dilated pouchlike
contains appendix (appendicitis)2. colon- subdivided into 4 parts:
a. ascending colon- right sideb. transverse colon- acrossc. descending colon- left sided. sigmoid colon- s-shaped
3. rectum4. anal canal
mixing & peristalsis occurs but slower
2-3 mass movements happen per day
forces feces into lower 2 regions until eliminated
if feces stay in too long leads to constipation
major prob: colon cancer