PowerPoint Presentation

The Digestive System

Organs of the Digestive SystemOrgans of the Digestive System

Two main groups

Alimentary canalor GI tract

Accessorydigestive organs

Organs of the Alimentary CanalOrgans of the Alimentary Canal

Mouth

Pharynx

Esophagus

Stomach

Small intestine

Large intestine

Accessory Digestive OrgansAccessory Digestive Organs

Salivary glands

Teeth

Pancreas

Liver

Gall bladder

The Mouth (Oral Cavity)The Mouth (Oral Cavity)

Lips – sense temp.and texture; protectmouth

Hard palate andSoft palate – formthe roof

Uvula – fleshyprojection at theback of the softpalate

The Mouth (Oral Cavity)The Mouth (Oral Cavity)

Tonsils

palatine tonsils - oneither side of theback of the mouth

lingual tonsils– atthe back of thetongue

both play a role inthe immune system

Digestive Processes in the MouthDigestive Processes in the Mouth

mastication (chewing) of food

mixing of masticated food with saliva(secreted by salivary glands)

saliva contains enzymes that begin thedigestion of carbohydrates

initiation of “deglutition” (swallowing) bythe tongue

The Pharynx (throat)The Pharynx (throat)

food and air share thispassageway

muscular tube thatmoves food into theesophagus

when we swallow food,a flap of tissue knownas the “epiglottis”covers the trachea

The EsophagusThe Esophagus

muscular tube that runsfrom pharynx to stomachthrough the diaphragm

moves food byperistalsis (slowrhythmic contractions)

cardiac sphincter (loweresophageal sphincter)

group of muscles, at thebottom of the esophagus,that contracts and closesthe entrance to thestomach when food ispresent – this preventsbackflow

The StomachThe Stomach

pouch-like organ in the left hypochondriac regionof the abdominal cavity

regions of the stomach:

cardiac region – portion closest to the heart

fundus – upper rounded portion

body – middle portion

pylorus – narrow bottom portion

pyloric sphincter – circular muscle at the base ofthe stomach which controls the emptying of thestomach’s contents into the small intestine

Stomach AnatomyStomach Anatomy

•the lining of the

stomach is thick

and has many

folds called “rugae”

•as the stomach fills

up, the wall distends

and the folds

disappear

Digestive Processes in the StomachDigestive Processes in the Stomach

food is mixed with gastric juice (containshydrochloric acid and enzymes)

pepsin begins to break down protein

muscle movements of the stomach form asemifluid mass called “chyme” (processedfood)

muscles move chyme, in small batches,into the small intestine

The Small IntestineThe Small Intestine

it is about 20 feet longfrom stomach to largeintestine

lined with villi (tiny, one-cell-thick fingerlikeprojections withcapillaries) throughwhich digested nutrientsare absorbed into thebloodstream

Subdivisions of the Small IntestineSubdivisions of the Small Intestine

“Dogs Just Itch!”“Dogs Just Itch!”

Duodenum

10 inches long

chyme mixes with bile (digests fat), pancreaticjuice (digests starch, proteins, and fat) andintestinal juice (digests sugars)

Jejunum

8 feet long

Ileum

connects small intestine to large intestine

Subdivisions of the Small IntestineSubdivisions of the Small Intestine

“Dogs Just Itch!”“Dogs Just Itch!”

The Large IntestineThe Large Intestine

about 5 feet long

forms a rectangle around the tightlypacked small intestine

waste products usually remain in thelarge intestine from 12 – 24 hours

Large IntestineLarge Intestine

Subdivisions of the Large IntestineSubdivisions of the Large Intestine

Cecum

saclike first part of the large intestine

has 3 openings: one from the ileum into cecum,one from the cecum into the colon, and one fromthe cecum into the appendix

Appendix is filled with lymphatic tissue and canbecome inflamed (appendicitis)

Water and necessary substances are absorbedinto the bloodstream and feces is formed

Subdivisions of the Large IntestineSubdivisions of the Large Intestine

Colon

ascending colon:extends upward

transverse colon:extends across

descendingcolon: extendsdownward,where itconnects to thesigmoid colon

Subdivisions of the Large IntestineSubdivisions of the Large Intestine

Sigmoid Colon

S-shaped body that goes across the pelvisto the middle of the sacrum, where itconnects to the rectum

Rectum

attaches to the anal canal

sphincter muscles of the anus open duringthe release of feces from the body(defecation)