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214 Cards in this Set
- Front
- Back
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6 functions of the digestive system |
Ingestion Secretion Mixing and Propulsion Digestion Absorption Defecation |
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GI tract alimentary canal includes... |
mouth, pharynx, esophagus, stomach, small intestine, and large intestine |
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Accessory structures of the GI tract |
teeth, tongue, salivary glands, liver, gall bladder, pancreas |
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4 layers of alimentary canal |
1) Mucosa (innermost) 2) Submucosa 3) Muscularis 4) Serosa |
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Mucosa layer of alimentary canal characteristics |
Innermost mucous membrane Inner layer - epithelium Middle layer - lamina propria Outer layer - smooth muscle |
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Mucosa layer of alimentary canal layers |
Inner layer - epithelium Middle layer - lamina propria Outer layer - smooth muscle |
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Lamina propria of mucosa layer of alimentary canal characteristics |
Areolar connective tissue with many blood and lymphatic vessels
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Submucosa layer of alimentary canal characteristics |
Areolar connective tissue with many blood and lymphatic vessels and extensive network of neurons |
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Muscularis layer of alimentary canal parts that have skeletal and smooth muscle |
skeletal muscle - mouth, pharynx, upper esophagus, external anal sphincter
smooth muscle - remaining GI tract. Circular and longitudinal layers |
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Serosa layer of alimentary canal characteristics |
outermost layer - serous membranes (portion of the peritoneum)
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Peritoneum characteristics |
Largest serous membrane in the body Simple squamous epithelium and areolar connective tissue |
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Visceral peritoneum function |
covers organs |
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peritoneal cavity is filled with ___. |
serous fluid |
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Parietal peritoneum lines what? |
the abdominopelvic cavity |
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Peritoneum contains what? |
Blood, lymphatic vessels, nerves, and sometimes fat to insulate, cushion, and protect |
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2 Major folds of the peritoneum that we discussed |
Greater Omentum Mesentery |
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Greater Omentum (fold of peritoneum) anatomy |
Double sheet Attachments from stomach to large intestine |
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Mesentery fold of the peritoneum function |
Binds digestive organs to posterior abdominal wall |
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Two nervous systems of the gut |
Enteric nervous system Autonomic nervous system |
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Enteric nervous system location |
Esophagus to anus |
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Enteric nervous system plexuses |
Myenteric and submucosal |
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Myenteric plexus location |
Between longitudinal and circular smooth muscle |
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Submucosal plexus location |
within submucosa |
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Enteric nervous system is extrinsic/intrinsic set of nerves |
intrinsic |
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Sensory neurons in enteric nervous system detect ____ present in lumen or ____ of GI tract organs. |
Chemicals Stretch |
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What connects myenteric and submucosal plexuses? |
Interneurons |
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Motor neurons in the myenteric plexus function |
Increases GI tract motility |
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Motor neurons in the submucosal plexus function |
Secretions of the GI tract organs |
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Autonomic nervous system has extrinsic/intrinsic nerves |
Extrinsic |
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ANS parasympathetic function |
Increases activity of ENS |
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ANS sympathetic function |
Inhibits neurons of ENS |
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GI reflex pathways |
Sensory receptors detect amount and type of food in GI tract |
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GI reflex pathways sensory receptors synapse where to regulate what? |
Synapse with neurons in the CNS, ENS, and ANS to regulate GI secretion and motility |
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Salivary glands are located where and have what function? |
Lie outside the mouth and empty their contents into ducts with deliver saliva into the oral cavity |
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3 major salivary glands |
Parotid Submandibular Sublingual |
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Parotid salivary gland location |
between skin and masseter muscle |
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submandibular salivary gland location |
Floor of the mouth Medial and partly inferior to mandible |
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Sublingual salivary gland location |
Beneath tongue |
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How much saliva do we produce in a day |
1 to 1.5 L |
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What makes up saliva? |
99.5% water 0.5% solutes |
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What solutes are in saliva? |
ions, dissolved gasses, organic molecules, mucus, IgA, lysozyme salivary amylase |
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Which nervous system increases salivation? Which decreases salivation? |
Increases - Parasympathetic Decreases - Sympathetic |
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The upper and lateral surfaces of the tongue are covered with what? |
papillae, some of which contain taste buds |
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Lingual gland secretes what? |
Mucus and lingual lipase |
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Teeth are located in what processes? |
Alveolar |
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___ cover alveolar processes and extend slightly into each socket. |
Gingivae |
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Periodontal ligament function |
Dense connective tissue anchors teeth to the socket |
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Three regions of a tooth |
Crown, neck, and roots |
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Crown region of tooth |
Exposed portion |
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Neck region of tooth |
Constricted junction of crown and root |
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Root region of tooth |
1 to 3 roots embedded in sockets |
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Enamel of a tooth |
Protective coat 95% calcium salts (hardest substance in the body) |
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Dentin of tooth |
calcified connective tissue- bulk of tooth |
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Pulp cavity of tooth |
Connective tissue, blood vessels, and nerve fibers |
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____ (baby) teeth are lost between the ages of ___ and ___ years of age. After they are lost they become ___ teeth. |
Deciduous 6 and 12 Permanent |
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32 teeth |
8 incisors 4 canines 8 premolars (bicuspids) 12 molars (first second and third) |
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Incisors function |
Cutting |
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Canines function |
Tearing and piercing |
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Premolars function |
crushing and grinding |
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Molarsfunction |
Crushing and grinding |
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Mechanical digestion in the mouth |
Mastication mixes food with saliva and forms a bolus which can be easily swallowed |
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Bolus |
What food becomes after it is masticated |
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Chemical digestion - what begins the breakdown of starch into ____? |
Salivary amylase Breaks down starch into disaccharides and other smaller molecules |
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Chemical digestion- What begins the breakdown of triglycerides into ____. |
Lingual lipase fatty acids and diglycerides |
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Pharynx definition |
A funnel shaped tube that extends from the internal nares to the esophagus |
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What is the pharynx composed of? |
Skeletal muscle and is lined with a mucous membrane |
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Food passes from the mouth to the ____ then ____ then ____ |
oropharynx laryngopharynx esophagus |
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Where does the esophagus pass through the diaphragm? |
Esophageal hiatus |
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Esophagus- mucosa consists of what type of cell? |
Stratified squamous epithelium |
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At each end of the esophagus, the ____ is thickened forming the upper and lower ____ _____. |
muscularis esophageal sphincters |
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Upper esophageal sphincter is made up of what kind of muscle? |
Skeletal |
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Lower esophageal sphincter (cardiac sphincter) is made up of what kind of muscle? |
Smooth |
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Deglutition |
swallowing |
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3 stages of deglutition (swallowing) |
Voluntary Pharyngeal stage Esophageal |
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Deglutition voluntary phase |
Bolus pushed to oropharynx by tongue |
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Deglutition pharyngeal stage |
Bolus in oropharynx stimulates deglutition center in brainstem. Soft palate and uvula move upward Bolus moves through oropharynx and laryngopharynx. Upper esophageal sphincter relaxes and bolus enters the esophagus (involuntary) |
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Bolus in oropharynx stimulates what? |
deglutition center in brainstem |
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What happens to the soft palate and uvula during deglutition? |
they move upward |
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What happens to the upper esophageal sphincter during deglutition? |
It relaxes and bolus enters the esophagus |
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Esophagus secretes ___ to lubricate the ___ |
Mucus Bolus |
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Where is the cardia of the stomach located? What does it surround? |
Near the heart Surrounds opening of esophagus to stomach |
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Fundus of the stomach location |
Rounded portion lateral to the cardiac region |
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Body of the stomach location |
Large central portion |
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Pyloric part of stomach |
Funnel-shaped terminal end connects to duodenum (pyloric sphincter located here) |
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When the stomach is empty, how does the mucosa lie? |
In large folds or rugae |
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Surface cells of the stomach |
simple columnar cells and surface mucous cells |
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____ cells extend down into the ____ ____ forming gastric glands. |
Epithelial Lamina propria |
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4 types of secretory cells of the stomach (Gastric glands) |
Parietal Chief cells Mucous neck cells G cell (endocrine) |
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3 Exocrine secretory cells of the stomach (Gastric glands) |
Parietal Chief Mucous neck cells |
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1 endocrine secretory cell of the stomach (Gastric glands) |
G Cell |
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Parietal cell (endocrine secretory cell of the stomach - gastric gland) produce what? |
intrinsic factor for absorption of Vitamin B12 and HCl |
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Chief cell (endocrine secretory cell of the stomach - gastric gland) secrete what? |
Secrete gastric lipase and pepsinogen |
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Mucous neck cells (endocrine secretory cell of the stomach - gastric gland) secrete what? |
secrete mucus |
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G cell (exocrine secretory cell of the stomach - gastric gland) secrete what? |
Secrete gastrin which stimulates release of HCl |
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Mechanical digestion in stomach |
food is churned in the stomach via peristalsis because pyloric sphincter is mostly closed |
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Mechanical digestion in stomach produces what that slowly enters the duodenum |
Chyme |
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Chemical digestion in stomach- HCl responsible for what? |
Responsible for acidic pH of gastric juice |
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Purpose of acidic gastric juice in digestion in stomach |
Destroys many microbes and begins denaturing proteins |
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Chemical digestion in stomach - HCl inactivates what? Activates what? |
Inactivates salivary amylase Activates lingual lipase |
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What does HCl with pepsin convert pepsinogen to? (in Chemical digestion in stomach) |
Active pepsin |
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Function of pepsin in digestion? |
Begins breakdown of polypeptides (proteins) |
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Function of gastric lipase in digestion? |
Breakdown of triglycerides (minimal importance in adults) |
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Little or a lot absorption in the stomach? |
Little absorption (some water, short chain fatty acids, aspirin, and alcohol) |
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Digestion in the small intestine depends on what organs? |
Pancreas, Liver, and Gall Bladder |
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Pancreatic juices secreted into small ducts that unite to form what two major ducts? |
Pancreatic duct and accessory duct
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Pacreatic duct joins what and enters where? |
Common bile duct. Enters duodenum |
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Accessory duct enters where? |
Duodenum |
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How much pancreatic juice is produced every day? |
About a quart |
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What makes up pancreatic juice? |
Water, sodium bicarbonate, and many enzymes |
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What enzyme digests carbohydrates? |
Pancreatic amylase |
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What enzymes digest proteins?
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Trypsin Chymotrypsin Carboxypeptidase Elastase Digest proteins |
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What enzymes digest nucleic acids? |
Ribonuclease and deoxyribonuclease |
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What enzyme is the principle triglyceride digesting enzyme? |
Pancreatic lipase |
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Falciform ligament location? |
Extends from the diaphragm and divides the liver into right and left lobes |
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3 components of the Liver |
Hepatocytes Bile canaliculi Hepatic sinusoids |
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Hepatocytes function |
Metabolic secretory and endocrine functions |
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Hepatocytes are arranged where and how? |
In lamellae One cell thick Branched and bordered by sinusoids |
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Bile caniculi anatomy and function |
Small ducts between cells that collect bile |
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Bile passes to larger ducts which form the right and left ____ ducts which unite as the ______. |
Hepatic Common bile duct |
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Hepatic sinusoids are _____ capillaries |
Highly permeable |
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Hepatic sinusoids receive oxygenated blood from where? |
Hepatic artery |
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Hepatic sinusoids receive nutrient rich blood from where? |
Hepatic portal vein Hepatic artery Hepatic vein Bile duct |
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Portal triad of the Liver |
Bile duct Branch of hepatic portal vein Branch of hepatic artery |
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Hepatic lobule anatomy |
Hexagon with central vein. Radiating outward are rows of hepatocytes and sinusoids |
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Hepatic acinus is considered a ___ and ___ unit of the liver. |
structural and functional |
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Hepatic acinus of the liver anatomy |
Somehwat oval mass that includes portions of two lobules. Arranged in 3 zones |
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Which zone of the hepatic acinus if the last to die when circulation is impaired? |
Zone 1 |
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Which zone of the hepatic acinus if the last to show effects of toxins or bile obstruction? |
Zone 3 |
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Functions of the liver |
Bile production Carb, lipid, protein metabolism Process and produce hormones Detoxification Excretes thyroid and steroid hormones Bilirubin excretion Storage of glycogen and vitamins Phagocytosis by leukocytes Vitamin D activation |
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Bile salts have what two ends? |
Hydrophobic and hydrophilic |
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Bile salts emulsify fats by doing what? |
Physically breaking large fat globules into smaller particles and suspending them in micelles |
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What two ducts merge to form the CBD? |
Common hepatic duct and cystic duct(gall bladder) |
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Where does the CBD enter? |
Duodenum |
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Between meals, what sphincter is closed? Where does bile go during this time? |
Sphincter of the hepatopancreatic ampulla (Sphincter of Oddi). Bile enters the gall bladder and is stored there |
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Small intestine beginning and end |
Extends from the pyloric sphincter at the stomach Ends at the ileocecal valve at the large intestine |
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About how long and wide is the small intestine in a living person? |
10 feet long and 1 inch in diameter |
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Order of names for small intestine |
1.) Duodenum 2.) Jejunum 3.) Ileum |
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The majority of digestion and absorption happens where? |
in the small intestine |
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What structures increase the surface area for digestion and absorption in the small intestine? |
Circular folds (plicae circularis) Folds of the mucosa Folds of the Submucosa |
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Fingerlike projections of the mucosa |
Villi |
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Projection of the apical membrane of absorptive cells? |
Microvilli |
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Villus mucosa (SI) epithelial layer contains what? What is the function of these cells? |
Absorptive cells Release enzymes that digest food and contain microvilli that absorb nutrients. |
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Function of goblet cells in SI |
secrete mucus |
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Mucosa in the SI contains crevices lined with what which forms what? |
epithelium forming the intestinal glands (Paneth cells, several types of enteroendocrine cells which secrete hormones) |
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Paneth cells (SI) function |
Phagocytic cells that seecrete lysozyme |
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What secretes hormones in the SI? |
Enteroendocrine cells |
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Lamina propria of SI contains MALT. What does this stand for? |
Mucosa-associated lymphoid tissue |
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Peyer's patches |
Aggregated lymphatic nodules |
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What two lymphatic structures are located in the ileum of the SI? |
Peyer's patches (aggregated lymphatic nodules) and solitary lymphatic nodules |
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Submucosa contains what gland? What do they secrete? |
Duodenal glands (Brunners glands) Secrete alkaline mucus |
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Villus also contains what embedded in the lamina propria? |
Blood vessels and a lacteal (lymphatic capillary) |
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What part of the SI do the microvilli cover? |
The apical portion |
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Why is the apical portion of the SI called the brush border? |
Due to fuzzy appearance because of microvilli |
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What is the function of intestinal juice? |
Alkaline fluid that provides a vehicle for absorption of substances from chyme as they come in contact with the villi |
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Brush border enzymes |
Carbohydrate, protein, and nucleotide digesting enzymes |
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Where are enzymes in the SI produced? |
By epithelial layer of absorptive cells |
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Where are enzymes produced in the epithelial layer of absorptive cells in the SI inserted? Why? |
Inserted into plasma membrane of microvilli As absorptive cells slough off they break apart and release enzymes |
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Segmentation movement of SI has what function? |
Mixes chyme |
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Describe segmentation in the SI |
Localized contractions of portions of circular muscles. These portions relax, then middle portion contracts. This action does not move chyme, but instead mixes it to digest and absorb. |
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Peristalsis has what function? |
Moves chyme
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Describe peristalsis in the SI. |
Propulsive contractions from stomach to end of ileum |
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What are carbohydrates converted to during digestion? |
monosaccharidesWhat are carbohydrates converted to during digestion? |
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What are proteins converted to during digestion? |
Amino acids, dipeptides, tripeptides |
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What are lipids converted to during digestion? |
Fatty acids, glycerol, monoglycerides |
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What are nucleic acids converted to during digestion? |
nucleotides |
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What causes digestion of carbs, proteins, lipids, and nucelic acids in SI? |
Pancreatic juice, bile, and intestinal juice |
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When is digestion completed? |
When molecules are small enough to be absorbed into blood or lymph |
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How are monosaccharides transported? |
Facilitated diffusion or active transport |
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How are amino acids, dipeptides, and tripeptides transported? |
Active transport |
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How are lipids absorbed from lumen of SI? |
Very short fatty chains by simple diffusion Larger lipids incorporated into micelles |
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How are large lipids absorbed from lumen of SI? |
Incorporated in micelles Fuse with plasma membranes of absorptive cells Release lipids inside absorptive cells Lipids aggregate, reassemble, and become coated with protein forming chylomicrons |
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How do chylomicrons leave absorptive cells? |
By exocytosis and enter lymph capillaries (lacteals) From lymph they enter blood via lymphatic ducts |
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How are electrolytes mainly transported in SI? |
Active transport and diffusion |
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What stimulates active transport of Ca2+? |
Calcitrol |
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What vitamins are incorporated into micelles in the SI? |
Fat soluble A, D, E, and K |
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How do water soluble vitamins leave absorptive cells? |
Most B and vitamin C by simple diffusion |
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How is B12 absorbed in the lumen? |
B12 combines with intrinsic factor and is absorbed in the ileum |
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How is water absorbed? |
Osmosis |
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About how long is the large intestine is a living adult? |
About 5 feet |
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Rectum is how long in a living adult? |
about 6 inches |
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Mucosa of large intestine made up of what? |
Simple columnar epithelium- mostly absorptive and goblet cells. Located in tubular intestinal glands |
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Absorptive cells (with microvilli) primary function |
Mostly absorb water |
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Solitary lymphatic nodules of the mucosa may extend into the ____. |
Submucosa
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Muscularis of the large intestine anatomy |
External longitudinal muscle and internal circular smooth muscle |
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Portions of longitudinal muscle are thickened forming bands called the ____. |
Teniae coli |
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Contractions of the teniae coli gather the colon into pouches called ___. |
Haustra |
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Passage of chyme from ileum to cecum is regulated by what? |
ileocecal sphincter (usually partially closed) |
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After a meal, what reflex occurs? |
Gastroileal reflex |
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What does the gastroileal reflex do? |
Increases contractions in the ileum and opens the ileocecal valve moving chyme into the cecum |
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Haustral churning caused by what? |
Distension reaches a certain point and the walls of the haustra contract to mix and squeeze contents onward |
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Peristalsis |
Propulsive contractions |
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Mass peristalsis |
strong peristaltic wave that begins in the transverse colon and quickly drives the contents of the colon into the rectum |
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What in the large intestine that completes digestion? |
Bacteria |
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Carbohydrates are _____ by bacteria |
fermented |
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Bilirubin is decomposed to ___ and other pigments by bacteria |
stercobilin |
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What vitamins are synthesized by bacterial metabolism? |
Some B vitamins and vitamin K |
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What does the colon absorb? |
Water, electrolytes, and some vitamins |
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After chyme has been in the colon 3-10 hours what does it become? |
Feces |
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Defecation reflex regarding rectal wall |
Distends |
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Defecation reflex regarding stretch receptors |
Send sensory nerve impulses to the sacral spinal cord |
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Defecation reflex regarding motor impulses |
Travel back to large intestines |
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Longitudinal rectal muscles ___ and the internal anal sphincter ___. |
Contract Opens |
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What occurs when the external anal sphincter is voluntarily relaxed? |
Defecation |
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Cephalic stage of digestion |
Smell, sight, thought, and initial taste of food activates centers in the cerebral cortex hypothalamus and brain stem. Brain stem stimulates cranial nerves which increase salivation and gastric juice secretion. |
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Neural response during gastric phase once food reaches the stomach |
Presence of food stimulates stretch receptors. Increase in pH stimulates chemoreceptors |
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Neural receptors in gastric phase (once food reaches the stomach) activate what? |
Parasympathetic and enteric neurons, stimulate peristalsis, and flow of gastric juice. |
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Hormonal mechanisms of the gastric phase (once food reaches the stomach) |
Gastrin is secreted in response to distension of the stomach, increased pH, and partially digested proteins |
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What does gastrin stimulate? |
Secretion of gastric juice and increased motility of the stomach |
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Intestinal phase of digestion. Neural. |
Distension of duodenum causes enterogastric reflex. Stretch receptors send impulses to the medulla and stimulate sympathetic output to the stomach decreasing gastric motility |
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Hormonal mechanisms of intestinal phase |
Cholycystokinin (CCK) secreted by intestinal glands in response to partially digested food |
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Why is CCK (cholycystokinin) secreted? |
in response to partially digested food (by the intestinal glands) |
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What does CCK (cholycystokinin) stimulate? |
Secretion of pancreatic juice Contraction of gallbladder Relaxation of sphincter of Oddi Feeling of satiety |
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What stimulates secretin to be secreted from intestinal glands? |
Acidic chyme |
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What does secretin stimulate? |
Flow of pancreatic juice and bile |
