The Digestive System

The Digestive System: Function

• Preparation of food for absorption and use by the millions of body cells

• Alimentary canal - tube through your body that performs the above function.

The Mouth Structure

• Lips: outer boundary

• Cheeks: mucous membrane lateral boundary

• Hard/soft palate - uvula extends from

• Tongue

Tongue

• Places food during chewing

• Papillae contain taste buds

• Multiple blood vessels under tongue = high absorption of soluble drugs into circulation– Ex. Nitroglycerin pills

for heart attack,– Vitamins

Salivary Glands

• Parotid = largest– Located in front of and

below ear– Produces watery

substance with enzymes

• Submandibular– Located below

mandibular angle– Produces enzymes and

mucus

• Sublingual = smallest– Under floor of mouth– Produces mucous type

of saliva

Salivary Glands: Function

• Begins the break down of food through hydrolysis.

• Carbohydrate digestion begins in the mouth with aid of saliva.

Teeth

• Crown - exposed covered with enamel

• Neck - surrounded by gums (gingiva)

• Root - fits into socket

Teeth Coverings

• Enamel - Hardest substance in body

• Dentin - tissues, nerves, blood vessels

• Cementum - covers dentin

Dentition

• Deciduous Teeth– Baby teeth– Primary teeth

• 20 total– 8 incisors– 4 cuspids– 8 molars

Dentition

• Permanent Teeth– Adult teeth– Secondary teeth

• 32 Total

• 3rd set of molars come in after age 17 (wisdom teeth)

Other Organ Components

• Pharynx– Receives bolus

(rounded mass of food)– Carries bolus to

esophagus

• Esophagus– Collapsible tube that

enters the stomach– Posterior to trachea and

heart– Protected by a thick

layer of mucus

Esophagus Continued

• Food (Bolus) moves through the esophagus and the rest of the alimentary canal by peristalsis - involuntary muscle contractions.

Stomach

• Located below diaphragm and liver

• Enlarges after meals then collapses

• Size of large sausage

Stomach Divisions

• Fundus - large portion at end of esophagus

• Body - central portion

• Pylorus - lower portion near small intestine

Sphincter Muscles

• Guard openings to stomach– Cardiac - esophagus

to stomach– Pyloric - lower

portion of stomach to small intestine.

• Pylorospasm - muscle will not relax to allow passage of bolus = vomiting

Stomach Function

• Food storage

• Secretion of gastric juices

• Churning of food and breakdown into chyme - liquid food.

• Absorption = water, alcohol, and drugs

• Glands of stomach– Gastric - secret gastric juice– Mucus - contains enzymes and

hydrochloric acid.

Small Intestines

• 20 feet long• Divisions

– Duodenum = uppermost area, attaches to stomach.

– Jejunum = middle area

– Ileum = end portion, leads to large intestine.

• All set in place by mesentery (membrane)

Small Intestines Continued

• This is where most digestion occurs.

• Absorption of digestive products.

• Inside surface of small intestines covered with tiny projections called villi.– 1mm projections– Increase surface area by

160x

Large Intestines

• 5-6 feet long• Divisions

– Ascending colon - right side of abdomen

– Transverse colon - horizontally across abdomen and under liver

– Descending colon - left side of abdomen

– Rectum - last 7-8 inches– Anus - contains many

arteries and veins• Hemorrhoids -

enlargement of veins in anal canal.

Large Intestines Continued

• Water/electrolyte absorption

• Forms/stores feces

Large Intestines Continued

• Appendix– Located just behind

cecum– No functional

importance in digestion.

– Appendicitis = inflammation of the appendix

Accessory Organs

• Liver structure– Largest gland in body– Under diaphragm– Able to regenerate

• Liver function– Detoxifies many

substances– Makes and secretes bile– Metabolizes proteins,

fats, and carbs

Accessory Organs

• Gall bladder– Stores bile, increases

its concentration• Bile breaks down fat.

– During digestion, empties bile into small intestines

Accessory Organs

• Pancreas– Secretes digestive

enzymes– Secretes insulin– Secretes glucagon

(raises blood glucose levels)