From Mouth to RectumFrom Mouth to Rectum

the journey of our foodthe journey of our food

Gastrointestinal (Digestive System) Gastrointestinal (Digestive System) OverviewOverview

What is digestion?What is digestion? Digestion is the process by which food Digestion is the process by which food

and drink broken down into nutrients and drink broken down into nutrients These nutrients are then absorbed into These nutrients are then absorbed into

the blood and carried to cells throughout the blood and carried to cells throughout the body for energythe body for energy

What does the digestive What does the digestive system do?system do?

The digestive system involves:The digestive system involves:Mixing foodMixing foodMovement of foodMovement of foodChemical breakdown of foodChemical breakdown of foodMechanical breakdown of foodMechanical breakdown of food

What are the parts of the digestive What are the parts of the digestive system?system?

The digestive system includes the DIGESTIVE The digestive system includes the DIGESTIVE TRACT and other organs that aid in digestion .TRACT and other organs that aid in digestion .

Digestive tract:Digestive tract:mouth mouth

esophagus esophagus stomach stomach

small intestine small intestine large intestine large intestine

rectum rectum anus anus

Parts of other organ systems, such as Parts of other organ systems, such as nerves and blood, also play a major nerves and blood, also play a major

role in the digestive process.role in the digestive process.

Other organs that aid in Other organs that aid in digestion:digestion:tongue tongue

glands in the mouth that make glands in the mouth that make saliva saliva

pancreas pancreas

liver liver

gallbladdergallbladder

A trip down the digestive tract…A trip down the digestive tract… The SIX step process overviewThe SIX step process overview

Down the mouth: swallowing food or liquid Down the esophagus Through a ring-like valve where esophagus

and stomach are joinedinto the stomachContents of stomach emptied into small

intestine than large intestine lastly in the rectum and anus

We will now begin our fieldtrip down the digestive system in Ms. Frizzle’s magic school bus!

We begin our tour in the oral cavity:We begin our tour in the oral cavity:

IMPORTANT THINGS TO NOTICE:1.Teeth MASTICATE food

2. Saliva contains enzymes that dissolve food also acts like a LUBRICANT moving food along3. Tongue moves food and arranges it into a ball

called BOLUS

Moving along…through the throat Moving along…through the throat down the esophagus…into the down the esophagus…into the

stomachstomachIMPORTANT THINGS TO NOTICE:

1. Food is swallowed- we are headed down the esophagus

which connects the throat to the stomach

2. Watch out for the GLOTTIS which is heading towards the lungs**epiglottis**

3. Not the rhythmical contraction of the smooth muscle of esophagus

PERISTALSIS: moving food to stomach

4. We now reach the ESOPHAGEAL SPHICTER

CAUTIONCAUTION: keep all body parts : keep all body parts inside the bus now entering the inside the bus now entering the

STOMACHSTOMACH

IMPORTANT THINGS TO NOTICE:1. the churning action of the stomach

2. highly acidic environment: pH 1.5-2.5

3. edges of stomach have glands secreting GASTRIC JUICE

4. mucus lining of stomach: prevents stomach from eating itself

Crossing the Pyloric Sphincter into Crossing the Pyloric Sphincter into the Small Intestinethe Small Intestine

IMPORTANT THINGS TO NOTICE:1. Crossing the “Panama Canal of the Body”2. Majority of the digestion and absorption occur in small

intestine3. Walls of small intestine area arranged into folds and ridges

(VILLI)4. Walls of SI: BRUSH BORDER- large amounts of

MICROVILLI

Other things occurring right about Other things occurring right about now…now…

Hormones are vital to turning digestive Hormones are vital to turning digestive glands off and on.glands off and on.

The acidity of the food entering from the The acidity of the food entering from the stomach promotes the secretion of stomach promotes the secretion of numerous enzymes from the PANCREAS numerous enzymes from the PANCREAS and other local glands.and other local glands. lipase, amylase, trypsin, chymotrypsinlipase, amylase, trypsin, chymotrypsin

LIPASE: digests fat and gets help from BILE

**BILE: stored in gallbladder and dumped into the small intestine upon the arrival of food acting like an EMULSIFIER

TRYPSIN & CHYMOTRYPSIN: handle digestion of peptides (protein)

AMYLASE: carbohydrate digestion

HomonesHomones

GastrinGastrin: simulates secretion of gastric : simulates secretion of gastric juicesjuices

SecretinmSecretinm: stimulates the pancreas to : stimulates the pancreas to release bicarbonate in order to neutralize release bicarbonate in order to neutralize the acid (from the stomach)the acid (from the stomach)

CholecystokininCholecystokinin: (aka CCK) stimulates the : (aka CCK) stimulates the pancreas to release enzymes and gall pancreas to release enzymes and gall bladder to release bilebladder to release bile

NOTE: duodenum is the first part of the small NOTE: duodenum is the first part of the small intestine and where digestion occurs (other parts intestine and where digestion occurs (other parts

are for absorption)are for absorption)

Caecum: the first part of the large intestine (the connection betweenthe small intestine and the large

From the small intestine to the From the small intestine to the large intestine and into the rectumlarge intestine and into the rectum

Small and large intestine meet at the lower right Small and large intestine meet at the lower right corner of the abdomencorner of the abdomen

Large intestine (colon) has three parts: Large intestine (colon) has three parts: ascending, transverse, and descendingascending, transverse, and descending

Functions of large intestine: reabsorb water lost Functions of large intestine: reabsorb water lost during digestion and excrete salts when their during digestion and excrete salts when their concentration in the blood is too highconcentration in the blood is too high

The pathway: we enter the large intestine, travel The pathway: we enter the large intestine, travel up the ascending colon, across the transverse up the ascending colon, across the transverse colon, and down the descending colon into the colon, and down the descending colon into the rectum where food is stored until it gets rectum where food is stored until it gets eliminatedeliminated

Specialized Cells of the GI system:Specialized Cells of the GI system:

The gastrointestinal tract is a muscular tube The gastrointestinal tract is a muscular tube lined by mucous membrane, with regional lined by mucous membrane, with regional variations and specialized functions.variations and specialized functions. Esophagus: stratified squamous epithelium, cells Esophagus: stratified squamous epithelium, cells

resists cuttingresists cutting Stomach: epithelium renewed in approximately 4-Stomach: epithelium renewed in approximately 4-

5 days, prevent self-digestion5 days, prevent self-digestion Small Intestine: villi increase surface areaSmall Intestine: villi increase surface area Large Intestine: absorbtive cells Large Intestine: absorbtive cells