Digestive system

• Functions of the Digestive System: 1. Take in food. 2. Digestion of food. 3. Absorption of digested food. 4. Provide nutrients. 5. Eliminate waste.
• The mouth is also known as buccal cavity or oral cavity, which includes lips, teeth, tongue, palate, salivary glands, and cheeks.
• Teeth - used for biting, cutting, crushing, and grinding food
• Tongue: A muscular organ in the mouth. It helps position food during mastication and gathers food into a bolus in preparation for swallowing. It is also used for taste.
• Cheeks: Muscles that aid in chewing and holding food in place while being masticated.
• Salivary Glands: Produce saliva to moisten food and begin digestion with enzymes like amylase.
• Three pairs of salivary glands are the parotid, submandibular, and sublingual glands.
• Functions of saliva: moistens food, neutralises stomach acid, begins chemical digestion of food, lubricates the mouth and protects the mouth against pathogens.
• The digestive tract consists of the mouth or oral cavity, pharynx, esophagus, stomach, small and large intestines and anus.
• Accessory organs of the digestive tract include salivary glands, liver, gall bladder and pancreas.
• Four layers of the digestive tract are: Mucosa, submucosa, muscularis, serosa/adventitia
• The four types of papillae—circumvallate, fungiform, foliate, and filiform—are all located on the sides or upper surface (dorsum) of the tongue.
• THE PHARYNX: Connects the mouth to the esophagus. Only the oropharynx and laryngopharynx transmit food.
• THE ESOPHAGUS: a narrow muscular tube lined with stratified squamous epithelium and extends from the pharynx to the stomach. There are upper and lower esophageal sphincters that regulate the movement of food into and out of the esophagus. The lower esophageal sphincter is sometimes called the cardiac sphincter.
• THE STOMACH: a J-shaped organ that expands to store food. It is positioned in the left hypochondriac, epigastric region.
• The stomach has 3 divisions: Fundus, Body, and Pyloric region,
• The curvatures of the stomach are called the lesser (upper right surface) and greater (lower left surface) curvatures.
• Gastric mucosa: contains goblet cells, chief cells, parietal cells, and enteroendocrine cells.
• Goblet cells: are simple columnar epithelium that secrete mucus which protects the mucosa from acid and digestive enzymes.
• Parietal cells: secrete HCl and intrinsic factor needed for vitamin B12 absorption.
• Chief cells: secrete pepsinogen which is converted into active enzyme pepsin. Pepsin is a protease that breaks down protein.
• Enteroendocrine cells: produce hormones such as gastrin, somatostatin, and histamine.
• Functions of the stomach: food is stored in the stomach until it can be partially digested and moved farther along the gastrointestinal tract. ■ Secretes gastric juice, which contains acid and enzymes that aid in the digestion of food. ■ Churns the food (by contractions of its muscular coat), breaking it into small particles and mixing them well with the gastric juice ■ Secretes intrinsic factor.
• THE SMALL INTESTINE: consists of three parts: the duodenum, jejunum and the ileum.
• Duodenum: The first part of the small intestine, where chyme is mixed with digestive juices such as pancreatic juice and bile
• Jejunum: The middle part of the small intestine, where the small intestine splits into the large intestine and the rectum.
• Ileum: the last section of the small intestine where nutrients are absorbed. It ends with the ileocecal valve which regulates the movement of chyme into the large intestines.
• Functions of the small intestines: mechanical digestion, chemical digestion and absorption.
• Large intestines: has 4 divisions. The cecum, colon, rectum, and anus. It also contains the appendix.
• Cecum: It is a blind pouch located in the lower right quadrant of the abdomen.
• Appendix: a finger-like attachment to the cecum that contains lymphatic tissue and serves immunity functions.
• Colon: The colon is divided into the following portions: ascending, transverse, descending, and sigmoid.
• Rectum: the last 7 to 8 inches of the large intestine, where feces are stored before being expelled.
• Anus: The opening of the digestive system that allows feces to leave the body. It is controlled by an internal and external sphincter muscle.
• Functions of the large intestines: 1) peristalsis, 2) bacterial digestion, 3) absorption, 4) defecation.
• Pancreas: an accessory organ to digestion, secretes pancreatic juices containing various enzymes.
• Pancreatic enzymes: trypsin, chymotrypsin, amylase, lipase, and carboxypeptidase.
• The pancreas also releases insulin and glucagon, which are hormones that control blood glucose levels.
• Liver: largest glandular organ in the body, located below the diaphragm on the right side of the abdominal cavity.
• Functions of the liver include detoxification (removing waste products from the blood), synthesis (producing bile salts, clotting factors, and albumin), storage (storing vitamins, minerals, and carbohydrates).