Digestive System PDF

# Digestive System ## Chapter 3.3 - The digestive system is the organ system that takes in food, digests it, absorbs nutrients and excretes the remaining waste. - The digestive system is made up of the digestive tract and accessory organs. ## The Digestive Tract - **mouth→ esophagus → stomach → sma...

# Digestive System ## Chapter 3.3 - The digestive system is the organ system that takes in food, digests it, absorbs nutrients and excretes the remaining waste. - The digestive system is made up of the digestive tract and accessory organs. ## The Digestive Tract - **mouth→ esophagus → stomach → small intestine → large intestine** - **2 major mechanisms:** - **Mechanical digestion:** physical breakdown - **Chemical digestion:** breakdown by enzymes and chemicals ## The Oral Cavity - **Mouth (Oral Cavity):** - **Lips** - **Gingiva (gums)** - **Hard palate** - **Uvula** - **Papillae of tongue** - **Soft palate** - **Palatine tonsil** - **Molars** - **Premolar** - **Canine** - **Tongue** - **Incisor** - **Mechanical Digestion in the Oral Cavity:** - **Teeth:** incisors, canines, pre molars and molars. Solid food masses are torn, ground, and crushed. - **Tongue:** manipulates food during chewing, pushing it back to the molars. - **Chemical Digestion in the Oral Cavity:** - **Salivary glands:** on the sides of the mouth, produce amylase a chemical enzyme that breaks down starch and helps moistens food. - **Result:** a moistened ball-like mass called a bolus that moves down into the digestive tract. - The bolus passes through the pharynx and glides over the **epiglottis** (a trap door to prevent food from entering the trachea). - Food then drops into the **esophagus**. ## Esophagus - A muscular tube, 2cm in diameter that connects the **mouth to the stomach**. - **Cardiac sphincter:** point of connection between the esophagus and stomach. - The cardiac sphincter prevents reflux of food from the stomach to esophagus. What happens when the constriction is weak? - **Movement in the esophagus:** - **Peristalsis:** occurs in the digestive tract. Peristalsis is a series of muscle contractions. In the esophagus it allows the bolus to move down from the esophagus and into the stomach. ## The Stomach - A J-shaped organ that is used to **store and digest food**. - Mechanical and chemical digestion occurs in the stomach. - **Mechanical digestion:** the stomach is lined with smooth muscle tissue that contracts and further churns the bolus of food. - **Chemical digestion:** enzymes and acids (aka "digestive juices") to chemically break down the food particles for absorption. - The resulting liquefied paste is called **chyme**. - **Chyme** is then released into the small intestine, controlled by the **pyloric sphincter**. ## Small Intestine - Is the major site of **digestion and absorption** into the bloodstream. - **Three major parts:** duodenum, jejunum, ileum. - The small intestine is approximately 6m long. Called "small" because of the diameter. ## Accessory Organs - **The liver and pancreas** help digestion by supplying digestive enzymes. - **The liver** produces bile. - **Bile** is a fluid that breaks down large molecules of fat to smaller molecules. - **Bile** is secreted into the **duodenum**. - **The pancreas** secretes **pancreatic juice**, which contains digestive enzymes that further breaks down carbohydrates, proteins and fats in the **duodenum**. - **The pancreas** also produces an important hormone called **insulin**. - **Insulin** regulates the concentration of **glucose** in the blood. - **Diabetes** develops when there is not enough insulin in the bloodstream or when the body cannot properly use the insulin the body makes. - Without insulin, glucose cannot get into the cells and **blood glucose levels** can increase to life-threatening levels. ## Large Intestine - The main function of the large intestine is to reabsorb **water and vitamins**. - The large intestine, or colon, is about 1.5 m long but **larger** in diameter than the small intestine. - All undigested matter and toxins are stored in the last part of the large intestine, the **rectum**. - The remaining solid matter is excreted as **feces** from the **anus**. - **Diagram:** A diagram of the digestive system showing the following parts: - Mouth - Pharynx - Esophagus - Stomach - Gallbladder - Small Intestine - Large Intestine - Rectum - Anus - Salivary Glands - Liver - Pancreas # Digestive System with the Amoeba Sisters - An image of a cartoon digestive system with the amoeba sisters is shown. - The text "Digestive System with the Amoeba Sisters" is displayed.