The Digestive System

Anatomy of the Digestive System The digestive System has two main parts: The Digestive tract Digestive Glands

The Digestive Tract The Digestive Tract is a long tube that starts at the mouth and ends at the anus (30ft long) This long tube is a passageway of several organs that help to breakdown food

It can take up to 24 hours for food to cover the length of the digestive tract.

Made up of: 1)The Mouth 2) Pharynx 3) Esophagus 4) Stomach 5) Small Intestine 6) Large Intestine(colon)

The Mouth Contains: Teeth: mechanically break down food. Oral Cavity where food enters the body. Contains: Teeth: mechanically break down food. Tongue: tastes and manipulates food. Enclosed by: Lips, Cheek, Palate *Uvula: small flap hanging at back of throat, lifts to close nasal cavity when swallowing *Salivary glands: produce saliva that lubricate food and start chemical digestion of sugars

uvula teeth tongue

The Pharynx At back of throat Passageway for both food and air. Epiglottis: flap that closes the airway (respiratory tract) when food is swallowed.

The Esophagus Elastic muscular tube that connects pharynx to stomach 2.5 cm wide and 25 cm long

FUNCTION: Churn, digest, store food STOMACH Muscular, j-shaped bag about 12 cm wide Left side of abdomen FUNCTION: Churn, digest, store food Two Sphincters: (Muscular rings)control the entrance and exit of food 1)Cardia is at entrance to the stomach after the esophagus. It prevents food from going back up. 2) Pyloric Sphincter controls what leaves stomach and goes to small intestine.

The Small Intestine (largest organ) Muscular tube ~ 3m long (folded several times) Most nutrient digestion and absorption takes place here Lined with intestinal villi: small folds lining small intestine which increase surface area for absorption of nutrients.

Large Intestine (Colon) Muscular tube, 1.5 m long, with smooth mucus lining to facilitate the passage of waste. Absorbs most of the water. Rectum- storage of waste(feces) Anus- opening for elimination of waste

Digestive Glands: are glands that secrete enzymes to help break down food for digestion These include: 1) Salivary Glands 2) Liver 3)Pancreas 4) Gastric Glands 5) Intestinal Glands

Salivary Glands Found in Mouth Located at level of upper, lower jaws and under tongue. Secretes about 1-2 liters of saliva a day Function: **Saliva contains an enzyme called AMYLASE Which starts the chemical digestion of Carbohydrates **Saliva also protects against bacteria

The Liver Located on the right side of the abdomen Largest gland in the human body Produces bile (1L a day) which helps the break down of fats by physically separating fat molecules. Bile is stored in the gall bladder

Pancreas Located on the left side of the abdomen beneath the stomach Secretes 2 things: pancreatic juices and insulin Pancreatic juices (1.3L a day), contain enzymes that help chemically digest fats, proteins and carbs. Insulin is a hormone which regulates blood sugar levels.

Gastric Glands Line the inside of the stomach About 35 million of them Produce 2-3 L of Gastric Juices a day Gastric Juices contain hydrochloric acid (HCl) and Pepsin(enzyme) which starts the chemical digestion of proteins Mucin – mucus layer to protect the stomach from digesting itself because of all the acid that the gastric juices have. ***Acid in stomach is the reason for heartburn or acid reflux

Intestinal Glands Located at the bottom of the villi that line the surface of the small intestine 50 million of them Secrete intestinal juices into that contain enzymes that complete the chemical digestion of fats, proteins and carbs.

Stages of Digestion Ingestion of food- taking in of food Digestion of food- the breakdown of food Absorption of nutrients-the taking up of nutrients Elimination of waste – the removal of waste materials from the body.

We ingest carbs, fats, proteins, water, vitamins and minerals. **Water, minerals, vitamins are absorbed directly as they go through digestive tract at the level of the intestines.

**Fats, carbs and proteins are more complex and cannot be directly absorbed but need to be broken down through digestion:

Digestion: is the transformation of complex molecules contained in food into simpler molecules that the body can use. For food absorption to occur, the food has to be broken down into smaller nutrients

Breakdown!!! Carbohydrates = glucose (simple glucose) Fats = glycerol and fatty acids Proteins = amino acids Glucose, amino acids, glycerol and fatty acids are the nutrients that will be absorbed

2 types of Food Transformations Mechanical Transformation nature of substance remains the same, only physical appearance changes Ex: chewing Chemical Transformation Bonds of molecules are broken, which gives rise to new substances Ex. Complex Molecules broken down by stomach acid into simpler molecules

Mouth Insalivation: saliva is mixed with food Mechanical Transformations Mastication (Chewing): using teeth to break food into smaller pieces. Tongue helps move food around. Insalivation: saliva is mixed with food Bolus: lump of food after it has been chewed and covered in saliva Swallowing (Deglutition) tongue helps push bolus back

Chemical Transformations Salivary Amylase The salivary amylase begins the digestion of carbohydrates (starch) by breaking them down into smaller chains of glucose.

Pharynx Mechanical Transformations Swallowing (Deglutition) How it works: *Tongue pushes bolus back *Uvula raises to close off access to nasal cavity *Epiglottis lowers to cover trachea (respiratory tract) *Bolus goes through the pharynx into the esophagus

Esophagus Mechanical Transformations After swallowing, food enters Peristalsis is the muscular contractions of the esophagus which moves the food through the esophagus down to the stomach

Stomach Mechanical Transformations Churning: muscular contractions of the stomach wall *Purpose: to soak food and mix it with gastric juices. *After mixing for a few hours the bolus becomes chime Peristalsis: Muscular contractions of stomach will move food to next section of digestive tract.

Stomach Chemical Transformations Pepsin digests proteins by breaking them down into smaller chains of amino acids. Pepsin needs an acidic environment to work. Gastric juices, which include hydrochloric acid, help pepsin work.

Small Intestine Mechanical Transformations Peristalsis: Muscular contractions of stomach will move food to next section of digestive tract. Churning: to mix with digestive juices and make absorption easier.

Small Intestine Chemical Transformations Bile from the liver turns fat into smaller pieces to make digestion of fats easier. The pancreatic and intestinal juices(containing enzymes) complete the digestion of carbohydrates, proteins and fats. All the chains of complex molecules will be broken down to their simplest form: Carbohydrates = Simple glucose Proteins= simple amino acids Fats = glycerol and fatty acids

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Large Intestine Mechanical Transformations Peristalsis: Muscular contractions of large intestine will move food to its exit of the body

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Small Intestine is where most absorption of Nutrients obtained through digestion must be absorbed to be used by the blood and lymphatic systems. Small Intestine is where most absorption of glucose, amino acids, fatty acids and glycerol happens. Large Intestine absorbs water, minerals and vitamins

(last part of digestion) Elimination of Waste (last part of digestion) Rectum (last section of large intestine) stores fecal matter (poop) Defecation is the process of removing poop from the body. Fecal matter is made up of bacteria, debris, fibre, and nutrients that have not been absorbed.

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