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