Organs of the Digestive System PDF

Organs of the Digestive System Lesson 2  Learning Goals Today I will… ❏ use appropriate terminology related to animal anatomy; ❏ explain the anatomy of the digestive system and the importance of digestion in providing nutrients needed for energy and growth. Human Digestive System A complete dig...

Organs of the Digestive System Lesson 2  Learning Goals Today I will… ❏ use appropriate terminology related to animal anatomy; ❏ explain the anatomy of the digestive system and the importance of digestion in providing nutrients needed for energy and growth. Human Digestive System A complete digestive system organized into specialized regions. 7 - 9 metres long when stretched out. ○ Length varies according to feeding habits → herbivores & omnivores are longer relative to body size than carnivores. This is because cellulose is harder to digest. The Mouth Site of mechanical and chemical digestion. Primary structures include: teeth, tongue, hard and soft palate, salivary glands. The Mouth: Saliva Produced by three pairs of salivary glands. Lubricates the food. Mostly water but does contain amylase (enzyme that begins the breakdown of starch). The Mouth: Swallowing Tongue: pushes food around to form a bolus. When we swallow, the soft palate rises to prevent food from going into the nasal passages. The epiglottis covers the trachea to prevent food going into the lungs. The Esophagus Swallowed food goes down the esophagus. Made of smooth muscle and epithelial tissue. The muscle contracts in a wave-like motion called peristalsis. The Stomach Physical and chemical digestion A J-shaped sac made of smooth muscle and epithelial tissue. Contains a mucous lining to protect it from acidic gastric juices. The Stomach: Digestion When food enters the stomach the nervous system sends a signal to release gastrin - a hormone that stimulates the release of gastric juices. Gastric juices have a pH of 2.0 - 3.0; they stop the action of amylase and cause pepsinogen to convert to pepsin (begins to break down protein into amino acids). The Small Intestine Breaks down large particles so that the nutrients can be absorbed. Receives enzymes from the liver and pancreas to help with digestion. The inner layer is folded into ridges with finger-like projections called villi. Each epithelial cell that make up the villi are covered in microvilli = surface area is increased 500X. Intestinal Villi The Duodenum The first section of the small intestine, 25cm long. Chyme (food ground to 1-2mm) is squirted from the stomach into the first part of the intestine by the teaspoon. Enzymes from the pancreas and liver are added in here. Jejunum Second section. About 2 - 2.5m long. Thicker and redder than the duodenum. Digestion continues and some nutrients are absorbed. Ileum 3rd and longest section (3.5m) Site of nutrient absorption Parts of the Large Intestine Cecum: links the large and small intestines Colon: 1.5 m long Rectum: 20 cm The Large Intestine (Colon) Converts liquid chyme into semi-solid feces. Absorbs water (approx. 20L filters through each day). Filled with "good" bacteria that help digest cellulose and create vitamins K and B. Rectum Elimination (Egestion) = opposite of ingestion Cellulose and fibre are important for bulk and maintaining water to help with egestion. Peristaltic waves push feces through the rectum which triggers defecation.  Digestive Time Food Spends in Primary Function Structure Structure Mouth Mechanical and chemical digestion 5 - 30s Esophagus Transport (swallowing) 10s Stomach Mechanical and chemical digestion 2 - 24h Small Intestine Mechanical and chemical digestion 3 - 4h Large Intestine Water absorption 18h - 2 days Accessory Organs Accessory Organs Involved in digestion but are not part of the continuous muscular tube that makes up the digestive system Includes the: ○ Pancreas ○ Liver ○ Gallbladder ○ Salivary glands The Pancreas 6 inch long, pink/gray organ that looks like a leaf. produces enzymes that break down proteins, lipids, and carbohydrates. neutralizes the acidic chyme. empties into the duodenum. The Liver Nutrient rich blood arrives from the intestine and filters through the liver. Has 250 different functions, the most important are: ○ storing and releasing blood sugar (glucose) for energy ○ sorting and processing vitamins and minerals ○ breaking down toxins into less harmful substances ○ recycling old blood cells The Liver and Gallbladder Produces 1L of bile daily. Bile assists in emulsification of fats into micelles. Bile is stored and concentrated in the gallbladder. Bile is released into the duodenum. Enzymes Specialized proteins coded for by DNA. Allow chemical reactions (breaking or forming bonds) to happen faster than they would otherwise Are specialized to only work with certain substrates. Hydrolysis Chemical digestion done with water and enzymes  Chemical Digestion Breakdown macronutrients into their monomers that the body can absorb and use. Carbohydrates Proteins Lipids Nucleic Acids Carbohydrases Proteases Lipases Nucleases Ex. Amylase, Ex. Pepsin, Trypsin, dissacharidases Erepsin