From Mouth to Rectum the journey of our food

Gastrointestinal (Digestive System) Overview What is digestion? What is digestion? Digestion is the process by which food and drink broken down into nutrients Digestion is the process by which food and drink broken down into nutrients These nutrients are then absorbed into the blood and carried to cells throughout the body for energy These nutrients are then absorbed into the blood and carried to cells throughout the body for energy

What does the digestive system do? The digestive system involves: The digestive system involves: Mixing food Mixing food Movement of food Movement of food Chemical breakdown of food Chemical breakdown of food Mechanical breakdown of food Mechanical breakdown of food

What are the parts of the digestive system? The digestive system includes the DIGESTIVE TRACT and other organs that aid in digestion. Digestive tract: mouth esophagus stomach small intestine large intestine rectum anus

Parts of other organ systems, such as nerves and blood, also play a major role in the digestive process. Other organs that aid in digestion: tongue glands in the mouth that make saliva pancreaslivergallbladder

A trip down the digestive tract… The SIX step process overview The SIX step process overview Down the mouth: swallowing food or liquid Down the esophagus Through a ring-like valve where esophagus and stomach are joined into the stomach Contents 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: IMPORTANT THINGS TO NOTICE: 1.Teeth MASTICATE food 2. Saliva contains enzymes that dissolve food also acts like a LUBRICANT moving food along 3. Tongue moves food and arranges it into a ball called BOLUS

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

CAUTION: keep all body parts inside the bus now entering the STOMACH IMPORTANT THINGS TO NOTICE: 1.the churning action of the stomach 2. highly acidic environment: pH edges of stomach have glands secreting GASTRIC JUICE 4. mucus lining of stomach: prevents stomach from eating itself

Crossing the Pyloric Sphincter into the Small Intestine IMPORTANT THINGS TO NOTICE: 1.Crossing the “Panama Canal of the Body” 2.Majority of the digestion and absorption occur in small intestine 3.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 now… Hormones are vital to turning digestive glands off and on. Hormones are vital to turning digestive glands off and on. The acidity of the food entering from the stomach promotes the secretion of numerous enzymes from the PANCREAS and other local glands. The acidity of the food entering from the stomach promotes the secretion of numerous enzymes from the PANCREAS and other local glands. lipase, amylase, trypsin, chymotrypsin lipase, 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

Homones Gastrin: simulates secretion of gastric juices Gastrin: simulates secretion of gastric juices Secretinm: stimulates the pancreas to release bicarbonate in order to neutralize the acid (from the stomach) Secretinm: stimulates the pancreas to release bicarbonate in order to neutralize the acid (from the stomach) Cholecystokinin: (aka CCK) stimulates the pancreas to release enzymes and gall bladder to release bile Cholecystokinin: (aka CCK) stimulates the pancreas to release enzymes and gall bladder to release bile

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

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

From the small intestine to the large intestine and into the rectum Small and large intestine meet at the lower right corner of the abdomen Small and large intestine meet at the lower right corner of the abdomen Large intestine (colon) has three parts: ascending, transverse, and descending Large intestine (colon) has three parts: ascending, transverse, and descending Functions of large intestine: reabsorb water lost during digestion and excrete salts when their concentration in the blood is too high Functions of large intestine: reabsorb water lost during digestion and excrete salts when their concentration in the blood is too high The pathway: we enter the large intestine, travel up the ascending colon, across the transverse colon, and down the descending colon into the rectum where food is stored until it gets eliminated The pathway: we enter the large intestine, travel up the ascending colon, across the transverse colon, and down the descending colon into the rectum where food is stored until it gets eliminated

Specialized Cells of the GI system: The gastrointestinal tract is a muscular tube lined by mucous membrane, with regional variations and specialized functions. The gastrointestinal tract is a muscular tube lined by mucous membrane, with regional variations and specialized functions. Esophagus: stratified squamous epithelium, cells resists cutting Esophagus: stratified squamous epithelium, cells resists cutting Stomach: epithelium renewed in approximately 4- 5 days, prevent self-digestion Stomach: epithelium renewed in approximately 4- 5 days, prevent self-digestion Small Intestine: villi increase surface area Small Intestine: villi increase surface area Large Intestine: absorbtive cells Large Intestine: absorbtive cells