DIGESTIVE SYSTEM

drg. ANIS A. MAKKY, MKes

ORAL BIOLOGY DEPARTEMENT

AIRLANGGA UNIVERSITY

SURABAYA, APRIL 16, 2007

1. ingest food

2. break food down physically and chemically into

absorbable nutrient molecule

3. absorb those molecules into the bloodstream

4. eliminate any indigestible remains.

FUNCTION

2 MAJOR GROUPS OF ORGANS

IN THE DIGESTIVE SYSTEM

ALIMENTARY CANAL :

organs thrue which food actually passes

ACCESSORY ORGANS :

they assist in digestion, but no food actually

passes through them

ALIMENTARY CANAL

* oral cavity

* esophagus

* pharynx

* stomach

* small intestine

* large intestine.

ACCESSORY

ORGANS

* teeth

* tongue

* salivary glands

* pancreas

* liver

* gallbladder.

Ingestion

Propulsion

Mechanical Digestion

Chemical Digestion

Absorption

Defecation

THE DIGESTIVE SYSTEM PERFORMS 6 BASIC ACTIVITIES:

1. deciduous teeth (20)

    2. permanent teeth (32)

    3. tongue

       a. skeletal muscles

       b. moves food mass “bolus”

       c. appropriate use of “lingual” terminology

ORAL CAVITY STRUCTURES

    4. major salivary glands (3 pair)

       a. parotid

- masseter

- mumps     

b. submandibular

- medial aspect of the mandibular body

- duct : lingual frenulum

       c. sublingual

- anterior submandibular gland & under the tongue

- its 10-12 ducts : floor of the mouth.

   

ORAL CAVITY STRUCTURES

    5. minor salivary glands

* lingual glands (on the tongue)

* buccal & labial glands (in the cheek & lip)

* palatine glands (in the palate)

* glossopalatine glands (on the glossopalatine

fold)    

ORAL CAVITY STRUCTURES

contains : enzymatic & nonenzymatic protein

calcium

phosphorus

sodium

other salt

dissolve gasses : N2, O2, CO2

cells (leukocytes : ginggival sulcus)

saliva is 99% water

SALIVA

pH : depends on the rate of secretion

faster : more alkaline (meal)

sleep : low

resting : 5, 81 (parotid gland)

6,39 (submandibular gland)

average : 6,7

secretion : follow diurnal rhytms

total volume : 600 – 700 ml up to 1500 ml

secretion parotid gland : 60-65%

submandibular : 20-30%

sublingual : 2-5%

minor gland : 6-7%

sulcus gingival : 10-100 µl/h

Function of the saliva1.digestive

2.antibacterial

3. lubrication

4. taste

5.buffering action

6.hygienic action

7.blood coagulation & tissue repair

8. inhibition of dental caries

9.water balance

Control of saliva secretion

1. taste

2.smell

3.mechanical stimulation

4.mechanical irritation

5.mastication of the food

6.chemical irritation

7.distention or irritation of the oesophagus

8.chemical irritation of the stomach

9.pregnancy

    1. oropharynx

    2. esophagus :

connects pharynx to stomach

    3. peristalsis - rhythmic smooth muscle

contractions propel material inside

PHARYNX

mucosa

submucosa

muscularis

serosa

LAYER of DIGESTIVE ORGAN

functions :

protecting against pathogens; absorbing nutrients;

and secreting mucus, enzymes, hormones

the mucosa consists of 3 sublayers:

* epithelium : hormone, enzyme, goblet cell

* lamina propria : blood vessels, lymph vessels,

and lymph nodules

* muscularis mucosae :

local movements of the mucosa

MUCOSA

submucosa :

* contains :

** blood vessels, lymphatic vessels

** lymphatic nodules

** nerve fibers :

submucosal plexus

= Meissner plexus

muscularis externa :

* 2 layers of smooth muscle :

circular & longitudinal

* between 2 layers :

myenteric plexus = Auerbach plexus

* functions : segmentation & peristalsis

* in several places :

the circular layer thickens to form sphincters

Serosa :

most exterior layer

MUSCLE of GIT : most smooth m.

2 types : 1. multi unit smooth m. 2. visceral smooth m.

Smooth m. consist of : actin dense bodies : actin +

actin myosin

SMOOTH MUSCLE POTENTIAL

1. Slow waves : rhytmic, not action potential, resting

freq. 3-12 per minutes

gaster 3/min.

duodenum 12/min.

ileum 8-9/min.

cause ?

“ sodium-potasium pump”

SMOOTH MUSCLE POTENTIAL

2. Spike potential : true action potential

occurs automatically

firing level : -40 mvolt

RMP : 50-60 mvolt

stimulation : stretch, asetilkolin,

parasympathetic

SMOOTH MUSCLE CONTRACTION

ESOPHAGUS

regulated by :

cardiac or gastroesophageal sphincter

collapsed when : empty

upper 1/3 is skeletal

middle 1/3 a mixture

lower 1/3 smooth

its functions include :

* storage of food

* chemical and mechanical digestion

bolus chyme (paste)

it is found nearly hidden by the liver

when it is empty : its J-shaped

and collapsed : folds known as rugae

STOMACH

 general anatomic regions

    a. cardia

    b. fundus

    c. body

    d. pyloric region

it is important in the process of physical digest

gastric pits

pyloric sphincter regulates

entry into the duodenum

 gastric pits 4 major secretory cells:

       a. chief cells

       b. parietal cells

       c. G-cell

       d. mucus cell

           

    

a.chief cells : pepsinogen

* activation : by low pH to form pepsin

* pepsin is a protease for protein digestion

b. parietal cells

i. HCl

   * secretion enhanced by histamine via H2 recep.

   * tagamet blocks H2 histamine receptors to

inhibit HCl secretion

ii. intrinsic factor

    binds to and allows B12 absorption in intestines     

c. G-cell : gastrin hormone

    * activates gastric juice secretion &

gastric smooth muscle “churning”

    * activates gastroileal reflex which moves

chyme from ileum to colon

d. mucus cell :

    protective role of mucus against acids

and digestive enzymes

    

What prevents the proteolytic enzymes and HCl secreted by the stomach from

damaging itself?

There are 3 basic reasons :

a thick coat of alkaline mucus coats the

stomach walls

mucosal epithelial cells are joined by tight

junctions and are impermeable to HCl

damaged epithelial cells are quickly shed and

replaced