Week-13 Digestive System 2024 PDF

At the end Identify the overall function of the digestive system of the Describe the general activities of each digestive system organ lesson I Name the organs of the alimentary canal and accessory digesti...

At the end Identify the overall function of the digestive system of the Describe the general activities of each digestive system organ lesson I Name the organs of the alimentary canal and accessory digestive organs will be able Explain the contribution of accessory organs to digestion to: Describe the processes of mixing and moving food along the digestive tract  OV EW H DI T E Y EM C O S Ingestion Digestion Absorption Defecation (Marieb & Keller, 2018) DIGESTIVE SYSTEM FUNCTION Ingestion- placing of food or fluid into the mouth In vertebrates, the teeth, saliva, and tongue play important roles in mastication (preparing the food into bolus). While the food is being mechanically broken down, the enzymes in saliva begin to chemically process the food as well. DIGESTIVE SYSTEM FUNCTION Propulsion - Movement of foods from one region of the digestive system to another. Peristalsis - alternating waves of contraction and relaxation that squeeze food along the GI tract Segmentation - movement of materials back and forth to foster mixing in the small intestine DIGESTIVE SYSTEM FUNCTION Digestion - occurs when enzymes break chemically down large molecules into their building blocks. Each major food group uses different enzymes Carbohydrates are broken down to simple sugars (like glucose). Proteins are broken down to amino acids. Fats are broken down to fatty acids and glycerol. TWO TYPES OF DIGESTION 1. Mechanical digestion - involves physically breaking down food substances into smaller particles to more efficiently undergo chemical digestion. This begins in the mouth with chewing or mastication and continues with churning, mixing actions in the stomach, and segmentation in the small intestine TWO TYPES OF DIGESTION 2. Chemical digestion - is to further degrade the molecular structure of the ingested compounds by digestive enzymes into a form that is absorbable into the bloodstream. Enzymes break bonds of macronutrient molecules Chemical digestion of carbohydrates begins in the mouth. Protein digestion begins in the stomach, and fat digestion begins in the small intestine All digestion is completed in the small intestine DIGESTIVE SYSTEM FUNCTION Absorption - simple molecules resulting from chemical digestion are absorbed into the blood or lymph. These molecules pass through the cell membranes (mucosal cells) of the lining in the small intestine and enter the bloodstream or lymphatic capillaries for distribution throughout the body. DIGESTIVE SYSTEM FUNCTION Defecation - Elimination of indigestible substances from the GI tract in the form of feces TWO MAIN GROUPS OF ORGANS 1. Alimentary Canal Gastrointestinal, or GI, tract continuous, coiled, hollow tube These organs ingest, digest, absorb, defecate ❖ Mouth ❖ Pharynx ❖ Esophagus ❖ Stomach ❖ Small intestine ❖ Large intestine ❖ Anus 2. Accessory Digestive Organ Include teeth, tongue, and several large digestive organs Assist digestion in various ways 1. ALIMENTARY CANAL : Mouth Mastication (chewing) of food Taste buds on the tongue allow for taste Tongue mixes masticated food with saliva Tongue initiates swallowing 1. ALIMENTARY CANAL : Tongue Is a muscular organ in the mouth. The tongue is covered with moist, pink tissue called mucosa. In the back of the mouth, the tongue is anchored into the hyoid bone. The tongue is vital for chewing and swallowing food, as well as for speech. The four common tastes are sweet, sour, bitter, and salty.  Tongue is covered with four kinds of papillae, fungiform, circumvallate, foliate and filiform papillae. With the exception of the filiform papillae, these types of papillae contain taste buds and are known as the gustatory papillae. Your filiform papillae's function is as a coating mechanism for your tongue. They create a rough texture on the surface of the tongue that helps when you're: Chewing your food. Filiform, do not contain taste buds. 1. ALIMENTARY CANAL : Pharynx ✔ Serves as a passageway for foods, fluids, and air ✔ Food is propelled to the esophagus by two skeletal muscle layers in the pharynx ✔ Alternating contractions of the muscle layers (peristalsis) propel the food ✔ on the left side are the regions of the pharynx 1. ALIMENTARY CANAL : Esophagus Anatomy About 10 inches long Runs from pharynx to stomach through the diaphragm Physiology Conducts food by peristalsis (slow rhythmic squeezing) to the stomach Passageway for food only (respiratory system branches off after the pharynx) 1. ALIMENTARY CANAL : Stomach Anatomy 1. ALIMENTARY CANAL : Stomach Anatomy -As food reaches the end of the esophagus, it enters the stomach through a muscular valve called the lower esophageal sphincter. -The lower esophageal sphincter (LES) is a bundle of muscles at the low end of the esophagus, where it meets the stomach. When the LES is closed, it prevents acid and stomach contents from traveling backwards from the stomach. The cardia is the first part of the stomach below the esophagus. It contains the cardiac sphincter, which is a thin ring of muscle that helps to prevent stomach contents from going back up into the esophagus. -The pylorus is the part of the stomach that connects to the small intestine. -When the stomach is empty, the inside has small folds called rugae. -Rugae allow the stomach to expand to accommodate large meals. It also grip the food inside the stomach to help physically break it down -The pyloric sphincter is a band of smooth muscle at the junction between the pylorus of the stomach and the duodenum of the small intestine. It plays an important role in digestion, where it acts as a valve to controls the flow of partially digested food from the stomach to the small intestine. -The antrum holds the broken-down food until it is ready to be released into the small intestine. It is sometimes called the pyloric antrum. Layers of Tissue in the Alimentary Canal Organs 1. ALIMENTARY CANAL : Small Intestine Anatomy of the Small Intestine ✔ The body’s major digestive organ ✔ Longest portion of the alimentary tube (2–4 m, or 7–13 feet, in a living person ✔ Site of nutrient absorption into the blood ✔ Muscular tube extending from the pyloric sphincter to the ileocecal valve ✔ Suspended from the posterior abdominal wall by the mesentery Subdivision ✔ Duodenum ✔ Jejunum ✔ Ileum 1. ALIMENTARY CANAL : Parts of the Small Intestine a. Duodenum ✔ 1st 9-10 in. ✔ Digestive enzymes & Bile Carbohydrates (C): Pancreatic amylase in the duodenum continues breaking down carbohydrates into simple sugars. Proteins (P): Enzymes like trypsin and chymotrypsin break down proteins into smaller peptides and amino acids. Lipids (L): Bile helps emulsify fats, making it easier for lipase (from the pancreas) to digest them into fatty acids and glycerol. b. Jejunum ✔ 8 ft long ✔ Finalize food digestion c. Ileum ✔ 12 ft. long ✔ Absorptive fnx. ✔ Connects with Large intestine 1. ALIMENTARY CANAL : Liver, Bile and Pancreas ✔ Chemical digestion begins in the small intestine ✓ Enzymes produced by intestinal cells and pancreas carries to are duodenum the pancreatic ducts by ✓ Bile, formed by the liver, enters the duodenum via the bile duct 1. ALIMENTARY CANAL : Large Intestine Larger in diameter, but shorter in length at 1.5 m, than the small intestine Extends from the ileocecal valve to the anus Subdivisions ✔ Cecum ✔ Appendix ✔ Colon ✔ Rectum ✔ Anal canal 1. ALIMENTARY CANAL : Large Intestine Cecum—saclike first part of the large intestine Appendix Hangs from the cecum Accumulation of lymphoid tissue that sometimes becomes inflamed (appendicitis) Colon Ascending—travels up right side of abdomen and makes a turn at the right colic (hepatic) flexure Transverse—travels across the abdominal cavity and turns at the left colic (splenic) flexure Descending—travels down the left side Sigmoid—S-shaped region; enters the pelvis 7a. Anal canal – Terminal segment of the large intestine, between the rectum and anus, located below the level of the pelvic diaphragm. – It is located within the anal triangle of the perineum, between the right and left ischioanal fossa. – The anus is the aperture at the terminal portion of the anal canal. Colonoscopy or coloscopy - is a medical procedure involving the endoscopic examination of the large bowel and the distal portion of the small bowel. This examination is performed using either a CCD camera or a fiber optic camera, which is mounted on a flexible tube and passed through the anus. 2. ACCESSORY DIGESTIVE ORGANS Teeth - are hard bony appendages that are borne on the jaws and serve especially for the prehension and mastication (chewing) of food Humans have two sets of teeth during a lifetime ✔ Permanent teeth ✔ Deciduous (baby or milk) teeth Replace deciduous teeth between A baby has 20 teeth by age 2 ages 6 and 12 First teeth to appear are the lower central incisors A full set is 32 teeth (with the wisdom teeth) 2. ACCESSORY DIGESTIVE ORGANS Teeth - are hard bony appendages that are borne on the jaws and serve especially for the prehension and mastication (chewing) of food. Teeth are classified according to shape and function Humans have two sets of teeth during a lifetime ✔ Permanent teeth ✔ Deciduous (baby or milk) teeth Replace deciduous teeth between A baby has 20 teeth by age 2 ages 6 and 12 First teeth to appear are the lower central incisors A full set is 32 teeth (with the wisdom teeth) 2. ACCESSORY DIGESTIVE ORGANS Salivary Gland - Mixture of mucus and serous fluids Helps to moisten and bind food together into a mass called a bolus Contains: Salivary amylase—begins starch digestion Lysozymes and antibodies—inhibit bacteria Dissolves chemicals so they can be tasted. 2. ACCESSORY DIGESTIVE ORGANS Three pairs of salivary glands empty secretions into the mouth Parotid glands Found anterior to the ears Mumps affect these salivary glands Submandibular glands and Sublingual glands Both submandibular and sublingual glands empty saliva into the floor of the mouth through small ducts 2. ACCESSORY DIGESTIVE ORGANS Pancreas Soft, pink triangular gland Found posterior to the parietal peritoneum Mostly retroperitoneal Extends across the abdomen from spleen to duodenum Produces a wide spectrum of digestive enzymes that break down all categories of food Secretes enzymes into the duodenum Alkaline fluid introduced with enzymes neutralizes acidic chyme coming from stomach Hormones produced by the pancreas Insulin Glucagon 2. ACCESSORY DIGESTIVE ORGANS Liver Largest gland in the body Located on the right side of the body under the diaphragm Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament Digestive role is to produce bile Bile leaves the liver through the common hepatic duct and enters duodenum through the bile duct Bile is yellow-green, watery solution containing: Bile salts and bile pigments (mostly bilirubin from the breakdown of hemoglobin) Cholesterol, phospholipids, and electrolytes Bile emulsifies (breaks down) fats 2. ACCESSORY DIGESTIVE ORGANS Gallbladder Green sac found in a shallow fossa in the inferior surface of the liver When no digestion is occurring, bile backs up the cystic duct for storage in the gallbladder While in the gallbladder, bile is concentrated by the removal of water When fatty food enters the duodenum, the gallbladder spurts out stored bile