Digestive System
Organization of the Digestive System
* The organs of the digestive system are divided into TWO main groups:
* The ______– also called the gastrointestinal (GI) tract
* ______– teeth, tongue, salivary glands, liver, gallbladder, pancreas
Gastrointestinal (GI) Tract
* A long, winding, continuous tube that extends from the ______
* Averages about 9 meters (______)
* Consists of: ______
Accessory Organs
* Located either ______the alimentary canal or ______it
* Communicates by way of ______
* ______the organs of the alimentary canal in their functions
* Includes: ______
Digestive Processes
* Food needs to be turned into a ______
* This needs to be done by:
* ______reducing the food
* ______reducing the food
* ______the food into the blood through the intestinal wall
* Carried by blood to the ______
Digestive Processes
* ______
* Taking food into the mouth (mechanical)
* ______
* Chewing (mechanical)
* Salivary action (chemical)
* ______
* Swallowing (mechanical)
* ______
* Wavelike contractions that move food through the GI tract (mechanical)
* ______
* Passage of food molecules from GI tract into circulatory system (mechanical & chemical)
* ______
* Elimination of undigestible wastes (mechanical)
SPECIAL FEATURES OF THE DIGESTIVE SYSTEM
* Peritoneum: serous membrane, lubricating tissue (pericardium of the heart, pleurae of lungs)
* Parietal Peritoneum: ______of the abdominal cavity
* Visceral Peritoneum: ______
* Extensions of the Parietal Peritoneum
* ______– attaches liver to diaphragm & anterior body wall
* ______– extends between liver and the lesser curvature of the stomach
* ______– extends from greater curvature of stomach to transverse colon
* ______– supports the intestine
* ______– supports large intestine
* Wall Structure of the Alimentary Canal
* ______
* Mucous membrane that ______of the alimentary canal
* Consists of a thin layer of loose connective tissue & a small amount of smooth muscle in the external layer
* Major functions: ______
* ______
* External to the mucosa
* Composed of loose connective tissue, rich in blood vessels, lymphatic vessels, nerve endings, & small glands
* ______
* Smooth muscle that externally encircles the submucosa
* Thickened at certain points along the alimentary canal to ______
* Provides the ______of food during mechanical digestion as well as the ______of food through the alimentary canal by ______
* ______
* The ______
DIGESTIVE ORGANS
* Mouth
* Function: process of ______(______)
* Moistening of food with saliva begins process of ______
* Accessory organs associated with mouth: ______
* Space between tongue and palate is called ______
* Cheeks and lips are separated by a space called the vestibule
* Palate: forms the ______
* ______: hard, bony anterior part of oral cavity
* ______: muscular, posterior part, forms archway bordering pharynx
* ______: along both sides of the archway
* ______: extends from the archway in a downward projection
* Tongue
* Anchored to the floor of the mouth by a membranous fold extending from its midline along its undersurface, called the lingual ______
* Contains ______and also help to provide friction for moving food
* Teeth
* Provide mastication
* Dentition: ______different sets of teeth during normal development
* First set: appear at about 6 months, continue to erupt until all ______are present by about 24 months
* Referred to as deciduous teeth
* Second set: appear between 6 and 12 years
* By the end of adolescence, all permanent teeth have erupted except for the third molars, or wisdom teeth (17 and 25 years)
* In a full set, there are ______
* Types:
* ______– pointed chisel (cutting)
* ______– cone-shaped (serve as tearing tool)
* ______– broad, flattened surfaces (grinding)
* Tooth Structure
* ______: visible part of tooth above the gum line
* ______: buried below the gum line
* ______: covers the crown – hardest substance in the body
* Salivary Glands
* Collection of accessory organs surrounding the mouth that secrete a fluid called saliva
* Saliva consists of ______
* Medium for dissolving soluble food molecules
* Solutes include mucus and enzymes
* Lysozyme destroys bacteria
* Salivary amylase ______
* Parotid Glands
* ______salivary glands
* Located in front of and slightly below each ear between the skin of the cheek and the masseter muscle
* Secretes a ______that is rich in ______
* Submandibular Glands
* Located along the inner surface of the jaw in the floor of the mouth
* Secrete a more viscous fluid than parotids due to the mucus in their secretions
* Sublingual Gland
* Lies ______
* Secrete a ______fluid due to the abundance of mucus
* Digestion in the Mouth:
* Digestion begins here
* Mastication – ______
* Creates a ______
* Pharynx
* Chamber located ______extending from the internal nares to the larynx
* Its walls are composed of skeletal muscle ______
* Divided into ______: nasopharynx, oropharynx, and laryngopharynx
* Function: transports food from ______
* Plays an important role in the act of swallowing
* Act of Swallowing:
* Begins as food ______from the mouth into the pharynx by the tongue
* ______to keep food from entering the nasal cavity
* Followed by contraction of muscles in the wall of the pharynx, which moves the larynx upward as the epiglottis presses downward (______)
* Muscles in lower pharynx relax, opening the passage into the ______
* The food bolus is pushed into the esophagus and onward to the stomach by ______, which begins in the pharynx and continues along the length of the esophagus
* Esophagus
* Muscular tube that extends from the pharynx to the stomach for about 25 cm (______)
* Located ______in the neck and upper thorax
* ______
* ______(lower esophageal sphincter/ cardiac sphincter) near its union with the stomach
* Acts as a valve to ______from the stomach
* Opens as peristaltic waves reach the stomach
* Stomach
* ______that is about 25 cm (10 inches) long and in most people can hold over 2 liters of food
* When empty, its inner linings form deep folds known as ______(ROO-JE)
* The convex lateral margin of the stomach is called the ______
* The greater omentum extends from the greater curvature
* The concave medial margin is known as the ______
* The lesser omentum extends from the lesser curvature
* Parts of the stomach
* ______– small area surrounding the opening that receives food from the esophagus
* ______– expanded region that bulges above the cardia; serves as a temporary holding area for food
* ______– main part of the stomach; lies between the fundus and the pylorus
* ______– narrowed, inferior region
* At the terminal end is the ______
* Serves as a valve to control the movement of food from the stomach to the small intestine
* Stomach Wall – MUCOSA
* Characterized by millions of tiny openings that can be seen only with a magnifying lens or microscope called gastric pits
* Gastric pits lead into tube-like gastric glands that secrete a collection of chemicals called ______
* ______of gastric juice pour out from these glands each day
* Glands contain secratory cells called ______, which secrete digestive enzymes
* ______
* Mucous cells secrete ______
* ______will develop if this lining breaks down
* Functions of the Stomach:
* Mechanical Digestion – accomplished by mixing and churning actions
* Chemical Digestion – provided by gastric juice
* Several enzymes are present, but most importantly, ______is present – secreted by zymogenic cells in an inactive form called pepsinogen
* Pepsin is a powerful ______capable of beginning the breakdown of nearly all proteins
* Pepsin and its acidic environment are kept from digesting the stomach wall by the protective layer of mucus that coats the ______
* Absorption
* Limited amount of absorption takes place across the stomach lining
* Materials the can cross this barrier are: ______
* Propulsion
* Provided by ______
* The material that is ready to enter the small intestine has been converted by mechanical and chemical digestion into a semi-fluid paste of small food particles and gastric juice known as ______
* Additional role of the stomach:
* Secretes a substance called ______, which ______(vital for survival due to its role in the production of mature red blood cells)
* Pancreas
* An accessory organ of the digestive system and has an ______function
* Soft, oblong organ that lies ______in the upper abdominal cavity
* Extends across the abdomen from its ______near the duodenum to its ______, which touches the spleen – middle portion is the ______
* Within the pancreas are groups of exocrine secretory cells called ______
* The secretory cells release a mixture of enzymes known as ______into the duct
* The ducts from all the acini drain into the pancreatic duct, which fuses with the ______before entering the small intestine
* Scattered among the acini are clusters of endocrine cells called the ______, which contain the cells that produce the hormones ______and release them right into the blood
* Functions of the pancreas
* Digestive function of the pancreas is the secretion of pancreatic juice, which finds its way into the duodenum of the small intestine
* In an average adult, about 1500mL of this watery, clear fluid is produced daily
* The pancreatic enzyme responsible for digesting carbs is known as ______
* The enzyme that aids in the digestion of fats is called ______
* The enzymes that digest nucleic acids are called ______
* Liver
* ______visceral organ of the body
* Occupies the ______of the abdominal cavity and presses against the diaphragm
* Like the pancreas, the liver is associated with the small intestine by way of the common bile duct
* One of its primary functions is the production of ______that is necessary in ______
* Structure of the Liver
* Divided into two main sections, called ______
* The large right lobe and the smaller left lobe
* The falciform ligament, a fold of the peritoneum, separates the right and left lobes and suspends the liver from the diaphragm and anterior abdominal wall
* Each lobe is further divided into numerous liver lobules
* Liver cells, which are known as ______, are arranged within each liver lobule into columns that converge toward a central vein
* Columns are separated from adjacent columns by channels lined with endothelial cells
* These channels are filled with flowing blood and are called ______
* ______remove bacteria arriving with blood from the digestive tract
* Bile canaliculi carry a fluid secreted by hepatocytes known as ______
* Bile is a ______that contains water, bile salts, bile pigments, cholesterol, and electrolytes
* Functions of the Liver
* Digestive role of the liver is the ______
* Emulsification – breaking apart clumps of ______into tiny droplets
* HDL (high density lipoproteins) – ______lipoproteins
* LDL (low density lipoproteins) – ______, can cause health problems
* Gallbladder
* The gallbladder is a small, thin-walled sac that serves as an accessory organ associated with the liver
* It is located immediately behind the liver, where it lies in a shallow depression tucked in against the lower margin of the right lobe
* The main function of the gallbladder is to ______
* Small Intestine
* Body’s ______digestive organ
* It completes the processes of mechanical and chemical digestion, and is the ______
* Longest segment of the alimentary canal
* Extends from the stomach to the large intestine for about 6 m (______)
* It is 2.5cm (______) in diameter
* Suspended in the abdominal cavity by the ______, which anchors it to the abdominal wall
* It is framed by the large intestine
* Has three segments: duodenum, jejunum, and ileum
* Segments of the Small Intestine
* ______
* Receives chyme from the stomach through the pyloric sphincter
* Only about 25cm (10 inches) long and is relatively immovable
* At the distal end of the duodenum, the small intestine continues as the more mobile jejunum
* ______
* Extends for about 2.5m (8 feet) to the third segment, the ileum
* ______
* Longest segment at about 3.6m (12 feet)
* It unites with the large intestine at the ______, which helps regulate the flow of material from the ileum to the large intestine
* Small Intestine Wall
* Mucosa
* Extremely ______
* Has tiny projections known as intestinal ______
* Villi project about 1mm into the lumen of the small intestine where they come in contact with its contents
* Covering each villus is the mucosa, whose cells are bristled with thousands of tiny microprojections called ______
* Within each villus are capillaries and a lymphatic vessel (called a lacteal), which carry absorbed nutrients away with blood
* Submucosa
* Contains numerous lymphatic nodules, known as ______, which protect the body against infectious microorganisms that try to penetrate the intestinal wall
* Also contains a collection of mucous glands, called ______, found only in the duodenum – help ______
* Functions of the Small Intestine
* Chemical Digestion
* ______by using a mixture of enzymes and bile
* Receives a wide spectrum of pancreatic enzymes from the pancreas and bile from the liver by way of the common bile duct
* Breaks down a wide spectrum of food (maltase, lactase, sucrase, and dextrase – all digest monosaccharides, which are carbs)
* Absorption
* Small intestine is the main site of nutrient absorption
* Effectiveness is due to the vast surface area of its mucosa (villi)
* Carb digestion begins in the mouth and ends in the small intestine
* Protein digestion by pepsin in the stomach and later in the small intestine by enzymes from the pancreas and intestinal mucosa results in the availability of amino acids
* Fat digestion occurs by the action of bile salts and enzymes within the small intestine