Anatomy and Physiology of the Digestive System PDF

# Anatomy and Physiology of the Digestive System ## Anatomy of the Digestive System ### Digestive Tract The digestive tract is a muscular tube approximately 11 meters long and of irregular diameter that runs longitudinally through the trunk in a ventral position. It is lined with epithelial tissu...

# Anatomy and Physiology of the Digestive System ## Anatomy of the Digestive System ### Digestive Tract The digestive tract is a muscular tube approximately 11 meters long and of irregular diameter that runs longitudinally through the trunk in a ventral position. It is lined with epithelial tissue. The digestive tract is composed of five regions: - **Mouth:** The entrance of the digestive tract, where food is ingested. It is supported by the maxilla and mandible bones, and delimited anteriorly by the lips and laterally by the cheeks. Structures in the mouth include the palate, tongue, and teeth. - **Palate:** The roof of the mouth. The soft palate in the back of the mouth contains the uvula, which aids in swallowing. - **Tongue:** A muscular organ in the floor of the mouth. It mixes food with saliva and assists in swallowing. It contains taste buds for the sense of taste. - **Teeth:** Hard, bony structures that are attached to the gums. The exposed portion of the tooth is called the crown, and the root is below the gum line, attached to the jawbone by the periodontal ligament. - **Pharynx:** A muscular cavity located in the neck that connects the mouth to the esophagus. Its walls contain tonsils, which are part of the immune system. The pharynx connects to the middle ear through the Eustachian tubes, to the nasal cavity through the coanas, and to the larynx through the glottis. - **Esophagus:** A muscular tube that continues from the pharynx through the thorax. It passes through the diaphragm and enters the abdomen, where it connects to the stomach. The esophagus carries food from the pharynx to the stomach. - **Stomach:** A dilated part of the digestive tract that is shaped like a sac. It is located in the abdominal cavity below the diaphragm and is slightly shifted to the left. The stomach contains two sphincter muscles that control the movement of food: the cardia at the entrance of the stomach and the pylorus at the exit. The stomach secretes gastric juice, which contains: - water and mineral salts - mucin: a lubricant that assists in food passage and protects the stomach lining from gastric juices - pepsin: a protease enzyme digests proteins - hydrochloric acid (HCl): maintains the low pH necessary for pepsin to function - **Small Intestine:** A tube approximately 7-8m long that extends from the pylorus to the ileocecal valve, which is the entrance to the large intestine. There are three regions of the small intestine: - **Duodenum** - **Jejunum** - **Ileum** The small intestine is lined with enterocytes, which are absorptive cells. The small intestine contains numerous folds and projections called villi and microvilli, which increase the surface area for absorption. The small intestine secretes intestinal juice, which contains: - water, mineral salts, and mucin - amylase: digests carbohydrates - protease: digests proteins - lipase: aids in fat digestion - **Large Intestine:** The last part of the digestive tract. It extends from the ileocecal valve to the anus. It is approximately 1.5 m long and three times thicker than the small intestine. It is lined with goblet cells, which secrete mucus. The large intestine has three regions: - **Cecum:** The first portion of the large intestine. It contains the appendix, which is a small, finger-like projection that plays a role in the immune system. - **Colon:** The longest part of the large intestine. It is divided into four parts: - **Ascending Colon** - **Transverse Colon** - **Descending Colon** - **Sigmoid Colon** - **Rectum:** The final portion of the large intestine. - **Anus:** The end of the digestive tract, where waste is eliminated from the body. It is controlled by two sphincter muscles: - **Internal Anal Sphincter:** made of smooth muscle and involuntary control - **External Anal Sphincter:** made of skeletal muscle and voluntary control ### Accessory Glands These glans are located outside the digestive tract but contribute to digestion by secreting enzymes, hormones, and fluids into the digestive tract. - **Salivary Glands:** Three pairs of salivary glands exist: - **Parotid Glands:** Located behind the angle of the mandible, below and in front of the ear. - **Sublingual Glands:** Located below the tongue. - **Submandibular Glands:** Located in the floor of the mouth. Salivary glands secrete saliva, which is composed of: - water, mineral salts, and mucin - salivary amylase (ptyalin): breaks down starch - lysozyme: an antibacterial enzyme - **Pancreas:** A gland located in the upper left abdomen behind the stomach. It is both an exocrine and endocrine gland. - **Exocrine Function:** Secretes pancreatic juice, which contains digestive enzymes and bicarbonate into the duodenum. - **Endocrine Function:** Secretes insulin and glucagon, which regulate blood sugar levels. - **Liver:** The largest internal organ in the body. It is located in the right upper abdomen. It produces bile, which is stored in the gallbladder. - **Bile:** Helps digest fats by emulsification and neutralizing stomach acids. - **Other Functions:** The liver performs many functions, including: - detoxification of blood - synthesis of proteins - storage of glycogen - production of glucose - regulation of blood volume and pressure - production of bile, which is important for digestion ## Physiology of the Digestive System ### Digestion Digestion is the process of breaking down food into smaller molecules that can be absorbed by the body. This occurs due to mechanical and chemical processes. - **Mechanical Digestion:** Involves the physical breakdown of food into smaller pieces. - **Mouth:** Mastication (chewing) - **Stomach:** Churning movements - **Chemical Digestion:** Breaking down large molecules into smaller ones using enzymes. **Stages of Digestion** 1. **Ingestion:** The process of taking food into the mouth. 2. **Mastication:** The mechanical breakdown of food by the teeth. 3. **Insalivation:** The mixing of food with saliva, which lubricates and dissolves food. 4. **Deglutition:** The process of swallowing food. 5. **Digestion in the Stomach:** The stomach breaks down proteins by the action of pepsin and HCl. 6. **Digestion in the Small Intestine:** The majority of digestion occurs in the small intestine. - **Intestinal Enzymes:** Breakdown carbohydrates, proteins, and fats. - **Pancreatic Enzymes:** Break down carbs, proteins, and fats. - **Bile:** From the liver, aids fat digestion. - **Absorption:** The process of absorbing the digested nutrients into the bloodstream. This mainly occurs in the small intestine. 7. **Digestion in the Large Intestine:** Absorbs the remaining water and electrolytes and forms feces. 8. **Egestion (Defecation):** The elimination of waste products from the body. ## Health and the Digestive System ### Common Digestive System Diseases - **Mouth:** - **Aftas:** (canker sores) ulcerations caused by infections or trauma - **Caries:** (decay of teeth) caused by bacteria that produce acids; can be prevented by good oral hygiene. - **Stomach:** - **Dyspepsia:** (indigestion) caused by poor motility or low enzyme production - **Gastritis:** inflammation of the stomach lining, can be caused by infections and the use of certain medications. - **Ulcers:** Open sores in the stomach lining; can be caused by bacteria, medications, alcohol, stress, smoking. - **Intestine:** - **Appendicitis:** Inflammation of the appendix, a small finger-like extension attached to the cecum. Requires surgical removal. - **Celiac Disease:** An autoimmune response to gluten, affecting the small intestine. It can causes damage to the villi affecting absorption. - **Crohn's Disease:** Chronic inflammatory bowel disease that can affect any part of the digestive tract. - **Liver:** - **Cholecystitis:** Inflammation of the gallbladder most often caused by gallstones. - **Hepatitis:** Inflammation of the liver, viral hepatitis is the most common cause. - **Cirrhosis:** Chronic liver disease characterized by scarring of the liver, often caused by hepatitis, alcoholism, and fatty liver disease. ### Maintaining Digestive Health Maintaining a healthy digestive system is important for overall health. Here are some tips: - **Eat a balanced diet:** Include plenty of fruits, vegetables, whole grains, lean proteins, and healthy fats. - **Stay hydrated:** Drink plenty of water throughout the day. - **Avoid excessive alcohol consumption:** Alcohol can irritate the digestive tract. - **Be mindful of portion sizes:** Eating too much at once can put stress on the digestive system. - **Manage stress:** Stress can have a negative impact on digestion. - **Get regular exercise:** Physical activity can help improve digestive health. - **See your doctor if you experience persistent digestive problems:** Some digestive disorders require medical treatment. This document provides an overview of the anatomy and physiology of the digestive system. It is important to note that this is a complex system, and there are many other aspects to consider. It is always best to consult with a healthcare professional for personalized advice regarding digestive health.