Anatomy of the Digestive System Tutorial PDF

ANATOMY OF THE DIGESTIVE SYSTEM: ORAL CAVITY, STOMACH , LIVER AND PANCREAS FAP WEEK 2 TUTORIAL 1 LEARNING OUTCOMES 1. Identify the organs of the digestive system, list their major functions. 2. Discuss the anatomy of the oral cavity and list the functions of its major structures and region...

ANATOMY OF THE DIGESTIVE SYSTEM: ORAL CAVITY, STOMACH , LIVER AND PANCREAS FAP WEEK 2 TUTORIAL 1 LEARNING OUTCOMES 1. Identify the organs of the digestive system, list their major functions. 2. Discuss the anatomy of the oral cavity and list the functions of its major structures and regions. 3. Describe the structure and functions of the pharynx and the esophagus and stomach. INTRODUCTION TO DIGESTIVE SYSTEM All living organisms must get nutrients from their environment to sustain life. These nutrients are used as raw materials for synthesizing essential compounds (anabolism). They are also broken down to provide the energy that cells need to continue functioning (catabolism). The digestive system, working with the cardiovascular and lymphatic systems, provides the needed nutrients in the form of organic molecules (such as carbohydrates, fats, or proteins). In effect, the digestive system supplies both the fuel that keeps all the body’s cells functioning and the building blocks needed for cell growth and repair.  The digestive system (alimentary system) consists of a muscular tube, the digestive tract, also called the gastrointestinal (GI) tract or alimentary canal, and various accessory organs. The digestive tract begins at the oral cavity (mouth). It continues through the pharynx (throat), esophagus, stomach, small intestine, and large intestine, which opens to the exterior at the anus. Accessory digestive organs include the teeth, tongue, and various glandular organs, such as the salivary glands, liver, and pancreas, as well as the gallbladder, which only has a secretory function. 1. FUNCTIONS AND PROCESSES OF THE DIGESTIVE SYSTEM Food enters the digestive tract and passes along its length. Along the way, the digestive system performs six integrated processes. Which are: 1. Ingestion takes place when food enters the oral cavity. Ingestion is an active process involving choices and decision making. 2. Mechanical digestion and propulsion involve the crushing and shearing of food and then propelling the food along the digestive tract. Mechanical digestion may not functions and processes of the digestive system. 3.Chemical digestion refers to the chemical breakdown of food into small organic and inorganic molecules suitable for absorption by the digestive epithelium. 4. Secretion is the release of water, acids, enzymes, buffers, and salts by the epithelium of the digestive tract, glandular organs, and the gallbladder. The glandular organs and gallbladder secrete their products into ducts that empty into the digestive tract. 5. Absorption is the movement of organic molecules, electrolytes (inorganic ions), vitamins, minerals, and water across the digestive epithelium. These materials are absorbed into the interstitial fluid of the digestive tract for distribution to body cells. 6. Defecation is the elimination of wastes from the body. The digestive tract and glandular and secretory organs discharge wastes in secretions that enter the lumen of the tract. Most of these wastes mix with the indigestible food of the digestive process. These wastes are dehydrated and compacted into matter called feces and ejected from the digestive tract through the anus. Anatomy of the oral cavity and its function: The functions of the oral cavity include: 1. Sensory analysis of food before swallowing 2. Mechanical digestion through the actions of the teeth, tongue, and palatal surfaces 3. lubrication by mixing with mucus and saliva 4. Limited chemical digestion of carbohydrates and lipids Anatomy and function of the stomach: The stomach is an expandable tube-like organ found in the upper left quadrant of the peritoneal cavity. The major functions of the stomach are to (1) Temporarily store ingested food received from the esophagus (2) Mechanically digest food through muscular contractions (3) Chemically digest food through the action of acid and enzymes. Ingested substances combine with the secretions of the stomach glands, producing a viscous, acidic, soupy mixture of partially digested food called chime  Anatomy and function of pancreas: The pancreas lies posterior to the stomach. It extends laterally from the duodenum toward the spleen. The pancreas is primarily an exocrine organ that produces digestive enzymes and buffers. The pancreas is an elongate, pinkish-gray organ about 15 cm (6 in.) long and weighing about 80 g (3 oz). The broad head of the pancreas lies within the loop formed by the duodenum as it leaves the pyloric part. The slender body of the pancreas extends toward the spleen, and the tail is short and bluntly rounded. The pancreas is retroperitoneal and is firmly bound to the posterior wall of the abdominal cavity.  The surface of the pancreas has a lumpy, lobular texture. A thin, transparent capsule of connective tissue wraps the entire organ. The pancreatic lobules, associated blood vessels, and excretory ducts are visible through the anterior capsule and the overlying layer of peritoneum. Blood supply: splenic, superior mesenteric and common hepatic arteries. The large pancreatic duct delivers the secretions of the pancreas to the duodenum. The pancreas has two distinct functions: One endocrine and the other exocrine. The endocrine cells of the pancreatic islets secrete insulin and glucagon into the bloodstream to control blood sugar. The exocrine cells include the acinar cells and the epithelial cells that line the duct system. Together, these exocrine cells secrete pancreatic juice (an alkaline mixture of digestive enzymes, water, and ions) into the small intestine. Acinar cells secrete pancreatic enzymes. ( which do most of the digestive work in the small intestine)  Pancreatic enzymes break down ingested materials into small molecules suitable for absorption.  The water and ions, secreted primarily by the cells lining the pancreatic ducts, help dilute and neutralize acid in the chyme. Anatomy and function of liver: The liver is the largest visceral organ, a firm, reddish-brown organ weighing about 1.5 kg (3.3 lb). Most of its mass lies in the right hypochondriac and epigastric regions, but it may extend into the left hypochondriac and umbilical regions as well. The versatile liver performs essential metabolic and synthetic functions. Most of surface of the liver is wrapped in a tough fibrous capsule and is covered by a layer of visceral peritoneum. Anterior surface of liver Posterior surface of liver Physiology of the Liver The liver carries out more than 200 functions. They fall into three general categories: (1) Metabolic regulation: The liver is the primary organ involved in regulating the composition of circulating blood. (2) Hematological regulation: The liver receives about 25 percent of cardiac output. It is also the largest blood reservoir in your body. (3) Bile production: The liver synthesizes bile and secretes it into the lumen of the duodenum. Hormonal and neural mechanisms regulate bile secretion. Bile consists mostly of water, with minor amounts of ions, bilirubin (a pigment derived from hemoglobin), cholesterol, and an assortment of lipids collectively known as bile salts. References: ​ Martini, F.H., Nath, J.L., Bartholomew, E.F. (2018). Fundamentals of Anatomy & Physiology (11th Ed.). Global Edition, Pearson Publisher. Any Questions? Thank you