DIGESTIVE SYSTEM Jhia Anjela D. Rivera 1 1 BS Biology, Department of Biology, College of Science, Polytechnic University of the Philippines
DIGESTIVE SYSTEM Consists of the digestive tract (gastrointestinal tract (GIT), alimentary canal/tract) and other associated organs Meals on wheels (with the aid of circulatory system) Digests foods into soluble form
FUNCTIONS OF DIGESTIVE SYSTEM INGESTION solid and liquid food intake through the mouth MASTICATION chewing, grinding of food into smaller pieces (teeth) PROPULSION movement of food from one end of the digestive tract to the other Degluttion (swallowing) moves liquids or a soft mass of food and liquid from the oral cavity into the esophagus Peristalsis lower the food in the stomach Mass movements
FUNCTIONS OF DIGESTIVE SYSTEM MIXING mixture of masticated food with different juices/enzymes SECRETION added to lubricate, liquify, buffer and digest the food DIGESTION break down of food into smaller molecules that can be absorbed by the body ABSORPTION movement of molecules out of the DT and into the circulation or into the lymphatic vessels (AA, FA, MS, V, M, H 2 O)
FUNCTIONS OF DIGESTIVE SYSTEM ELIMINATION waste products excretion in the form of feces
REGIONS OF THE DIGESTIVE TRACT ORAL CAVITY PHARYNX ESOPHAGUS STOMACH SMALL INTESTINE LARGE INTESTINE ANUS
PERITONEUM Walls and organs of the abdominal cavity are lined with serous membranes Visceral peritoneum serous membrane that covers organs Parietal peritoneum covers the interior surface of the wall of the abdominal cavity Mesenteries» These are connective tissue sheets that hold many organs in place within the abdominal cavity» They provide a route by which vessels and nerves can pass from the abdominal wall to the organs
PERITONEUM Walls and organs of the abdominal cavity are lined with serous membranes Visceral peritoneum serous membrane that covers organs Parietal peritoneum covers the interior surface of the wall of the abdominal cavity Mesenteries» These are connective tissue sheets that hold many organs in place within the abdominal cavity» They provide a route by which vessels and nerves can pass from the abdominal wall to the organs
PERITONEUM Retroperitoneal - refers to the abdominal organs that doesn t have mesenteries Duodenum, pancreas, ascending and descending colon, rectum, kidneys and urinary bladder Mesentery proper - mesentery associated with the small intestines Transverse mesocolon, sigmoid mesocolon and mesoappendix
PERITONEUM
ORAL CAVITY Mouth Divided into 2 regions: Vestibule space between the lips Oral cavity proper lies medial to the teeth
ORAL CAVITY
TONGUE Large muscular organ that almost occupies all of the area in the oral cavity Holds the food in place in cooperation with the lips and cheeks during mastication Major sensory organ for taste and speech, plays a role in swallowing Frenulum a thin fold of tissue that is attached anteriorly to the floor of the mouth
SALIVARY GLANDS Produce saliva (mixture of mucous and serous fluids) Branching ducts with clusters of alveoli at the ends of the ducts Three pairs of salivary glands Parotid Sublingual glands Submandibular glands
SALIVARY GLANDS Parotid Gland largest of the salivary glands, serous glands located just anterior to each ear Enter the oral cavity adjacent to the second upper molars Submandibular Glands Produce more serous than mucous secretions Open into the oral cavity on each side of the frenulum of the tongue
SALIVARY GLANDS Sublingual Glands Smallest of the three paired salivary glands, produce primarily mucous secretions Lie immediately below the mucous membrane in the floor of the oral cavity Each has 10-12 small ducts opening onto the floor of the oral cavity
SALIVARY GLANDS
PHARYNX Oropharynx and laryngopharynx transmit the food Epiglottis covers the opening of the larynx and keeps food and drink from entering the larynx
PHARYNX
ESOPHAGUS Extends between the pharynx and the stomach about 25 cm long and lies in the mediastinum, anterior to the vertebrae and posterior to the trachea passes through the esophageal hiatus (opening) of the diaphragm and ends at the stomach Transports food from the pharynx to the stomach
ESOPHAGUS Esophageal sphincter Upper and lower ES Regulate the movement of materials into and out of the esophagus
ESOPHAGUS
STOMACH Enlarged segment of the digestive tract in the left superior part of the abdomen Acts as storage and mixing chamber Located on the left superior part of the abdomen
STOMACH
STOMACH Most dilated part of the GIT and has a j- like shape Located in the epigastric, umbilical and left hypochondrium regions of the abdomen Divided into 4 regions Cardia gastroesophageal opening Fundus of the stomach superior to the cardia Body largest part of the stomach Pyloric part
STOMACH Pyloric part Antrum wider part of the funnel Canal narrow part Orifice opening of stomach to small intestine Sphincter/pylorus - thick ring of smooth muscle, which helps regulate the movement of gastric contents into the small intestine
SMALL INTESTINE Longest part of the GIT Extends from the pyloric orifice of the stomach to the ileocecal fold Approximately 6-7m long with a narrowing diameter from beginning to end Where the greatest amount of digestion and absorption occurs
SMALL INTESTINE Longest part of the GIT Extends from the pyloric orifice of the stomach to the ileocecal fold Approximately 6-7m long with a narrowing diameter from beginning to end Where the greatest amount of digestion and absorption occurs
SMALL INTESTINE Consists of three parts: Duodenum (12 inches long) Jejunum (2.5m) Ileum (3.5m) Two major accessory glands, the liver and the pancreas, are associated with the duodenum
SMALL INTESTINE
SMALL INTESTINE Duodenum First part of small intestine C-shaped, adjacent to the head of the pancreas 20-25cm long, above the level of umbilicus Divided into 4 parts:» Superior part extends from pylori orifice of the stomach to the neck of the gallbladder, just right to the body of L1 vertebra, clinically, it is called as duodenal cap or ampulla
SMALL INTESTINE Duodenum First part of small intestine C-shaped, adjacent to the head of the pancreas 20-25cm long, above the level of umbilicus Divided into 4 parts:» Superior part extends from pylori orifice of the stomach to the neck of the gallbladder, just right to the body of L1 vertebra, clinically, it is called as duodenal cap or ampulla
SMALL INTESTINE Duodenum» Descending part located just to right of the midline and extends from the neck of the gallbladder to the lower border of L3 vertebra; contains the entrance of major duodenal papilla and minor duodenal papilla» Inferior part longest section, crossing the IVC, aorta and vertebral column» Ascending part passes upward on or to the left of the aorta to approximately the upper border of L2 vertebra
SMALL INTESTINE Jejunum» Represents the proximal two-fifths of the small intestine» Mostly on the left upper quadrat» Larger in diameter and has thicker wall than ileum Ileum» Makes up the distal three-fifths of the small intestine» Mostly on the right lower quadrat and opens into the large intestine (jejunum and ileum major sites of absorption)
SMALL INTESTINE Ileocecal junction site where the ileum connects to the large intestine Ileocecal fold two flaps projecting into the lumen of the large intestine Ileocecal valve allows the intestinal contents to move from the ileum to the large intestine, but not in the opposite direction (also a sphincter)
LARGE INTESTINE Extends from the distal end of the ileum to the anus Absorbs fluids and salts from the gut contents, thus forming feces Consists of: Cecum and appendix Colon Rectum Anal canal
LARGE INTESTINE
LARGE INTESTINE Cecum and Appendix Cecum First part of the large intestine Inferior to the ileocecal opening and in the right iliac fossa Appendix Narrow, hallow, blind-ended tube connected to the cecum
LARGE INTESTINE Colon Extends superiorly from the cecum Consists of: Ascending colon Transverse colon Descending colon Sigmoid colon
LARGE INTESTINE Ascending colon extends superiorly from the cecum and ends at the right colic flexure (hepatic flexure) near the right inferior margin of the liver Transverse colon extends superiorly from the cecum and ends at the right colic flexure (hepatic flexure) near the right inferior margin of the liver
LARGE INTESTINE Descending colon extends from the left colic flexure to the superior opening of the true pelvis, where it becomes the sigmoid colon Sigmoid colon - forms an S- shaped tube that extends into the pelvis and ends at the rectum
LARGE INTESTINE Rectum - straight, muscular tube that begins at the termination of the sigmoid colon and ends at the anal canal Anal canal - begins at the inferior end of the rectum and ends at the anus (external GI tract opening) Anus external and internal sphincter
LIVER largest internal organ of the body in the right-upper quadrant of the abdomen, tucked against the inferior surface of the diaphragm consists of two major lobes: left and right, and two minor lobes, caudate and quadrate
LIVER
LIVER Surfaces of the liver include: Diaphragmatic surface anterior, superior and posterior directions (smooth and domed) Visceral surface inferior directions, covered with visceral peritoneum except for fossa of the gallbladder and porta hepatis Porta hepatis PoE into the liver for the hepatic arteries and the portal vein, and the exit point for the hepatic ducts
LIVER Lobes Consists of two major lobes, right and left lobes Separated by a falciform ligament two minor lobes: caudate and quadrate (inferior view)
GALLBLADDER A pear-shaped sac lying on the visceral surface of the right lobe of the liver in a fossa between the right and quadrate lobes Cystic duct Fundus of the GB rounded end Body of the GB major part of the fossa Neck of the GB narrow part To store bile released by the liver
GALLBLADDER
PANCREAS complex organ composed of both endocrine and exocrine tissues that perform several functions Lies mostly posterior to the stomach and consists of: Head of the pancreas lies within the C-shaped concavity of the duodenum Uncinate process lower part of the head Neck of the pancreas Body of the pancreas elongate and extends from the neck to the tail of the pancreas Tail of the pancreas
PANCREAS
PANCREAS Pancreatic duct begins in the tail of the pancreas Hepatopancreatic ampulla (Vater s ampulla) Sphincter of Oddi surround the ampulla Accessory pancreatic duct empties into the duodenum just above the major duodenal papilla at the minor duodenal papilla
PANCREAS
QUIZ 1. Which of these glands does not secrete saliva into the oral cavity? a. submandibular glands c. sublingual glands b. pancreas d. parotid glands 2. The portion of the digestive tract in which digestion begins is the a. oral cavity. c. stomach. e. jejunum. b. esophagus. d. duodenum
QUIZ 3. Given these parts of the small intestine: 1. duodenum 2. ileum 3. Jejunum Choose the arrangement that lists the parts in the order food encounters them as it passes from the stomach through the small intestine. a. 1,2,3 c. 2,1,3 e. 3,1,2 b. 1,3,2 d. 2,3,1
QUIZ 4. Given these structures: 1. ascending colon 2. descending colon 3. sigmoid colon 4. transverse colon Choose the arrangement that lists the structures in the order that food encounters them as it passes between the small intestine and the rectum. a. 1,2,3,4 c. 2,3,1,4 e. 3,4,1,2 b. 1,4,2,3 d. 2,4,1,3
QUIZ 3. The tongue a. holds food in place during mastication. b. plays a major role in swallowing. c. helps form words during speech. d. is a major sense organ for taste. e. all of the above.