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Digestive System Anatomy
Digestive tract Alimentary tract or
canal
GI tract
Accessory organs Primarily glands
Regions Mouth or oral cavity
Pharynx
Esophagus Stomach
Small intestine
Large intestine
Anus
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Digestive System Regulation
Nervous regulation
Involves enteric nervous
system
Types of neurons: sensory,motor, interneurons
Coordinates peristalsis
and regulates local
reflexes
Chemical regulation
Production of hormones
Gastrin, secretin Production of paracrine
chemicals
Histamine
Help local reflexes in ENS
control digestive
environments as pH levels
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Oral Cavity
Mouth or oral cavity Vestibule: Space
between lips or cheeksand alveolar processes
Oral cavity proper
Lips (labia) and
cheeks
Palate: Oral cavityroof Hard and soft
Palatine tonsils Tongue: Involved in
speech, taste,mastication,swallowing
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Teeth
Two sets
Primary, deciduous,
milk: Childhood
Permanent orsecondary: Adult (32)
Types
Incisors, canine,
premolar and molars
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Tooth structure:
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Salivary Glands
Produce saliva Prevents bacterial
infection
Lubrication
Contains salivaryamylase
Breaks down starch
Three pairs
Parotid: Largest
Submandibular
Sublingual: Smallest
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Pharynx and Esophagus
Pharynx
Nasopharynx
Oropharynx: Transmitsfood normally
Laryngopharynx:
Transmits food
normally
Esophagus Transports food from
pharynx to stomach
Passes through esophageal
hiatus (opening) ofdiaphragm and ends atstomach Hiatal hernia
Sphincters
Upper Lower
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Deglutition (Swallowing)
Three phasesVoluntary
Bolus of food moved by tongue from oral cavity topharynx
Pharyngeal
Reflex: Upper esophageal sphincter relaxes, elevatedpharynx opens the esophagus, food pushed intoesophagus
Esophageal Reflex: Epiglottis is tipped posteriorly, larynx elevated
to prevent food from passing into larynx
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Phases of Deglutition
(Swallowing)
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Stomach Anatomy:
Openings
Gastroesophageal:
To esophagus
Pyloric: To
duodenum
Regions
Cardia
Fundus
Body
Pylor
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Stomach Histology:
Layers Serosa or visceral
peritoneum:
Outermost
Muscularis: Threelayers
Outer longitudinal
Middle circular
Inner oblique
Submucosa
Mucosa
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Phases of Gastric
Secretion
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Movements in Stomach
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Small Intestine
Site of greatest amount ofdigestion and absorption
Divisions Duodenum
Jejunum
Ileum: Peyers patches orlymph nodules
Modifications Circular folds or plicae
circulares, villi, lacteal,
microvilli Cells of mucosa
Absorptive, goblet, granular,endocrine
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Small Intestine Secretions
Mucus Protects against digestive enzymes and stomach acids
Digestive enzymes
Disaccharidases: Break down disaccharides tomonosaccharides
Peptidases: Hydrolyze peptide bonds
Nucleases: Break down nucleic acids
Duodenal glands Stimulated by vagus nerve, secretin, chemical or tactile
irritation of duodenal mucosa
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Duodenum and Pancreas
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Liver
Lobes Major: Left and right
Minor: Caudate and
quadrate
Ducts Common hepatic
Cystic
From gallbladder
Common bile
Joins pancreatic duct at
hepatopancreatic ampulla
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Functions of the Liver
Bile production Salts emulsify fats, contain pigments as bilirubin
Storage Glycogen, fat, vitamins, copper and iron
Nutrient interconversion
Detoxification Hepatocytes remove ammonia and convert to urea
Phagocytosis Kupffer cells phagocytize worn-out and dying red and white blood cells,
some bacteria
Synthesis Albumins, fibrinogen, globulins, heparin, clotting factors
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Duct System
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Gallbladder
Bile is stored and concentrated
Stimulated by cholecystokinin and vegal
stimulation
Dumps into small intestine
Production of gallstones possible
Drastic dieting with rapid weight loss
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Pancreas
Anatomy
Endocrine
Pancreatic islets produce
insulin and glucagon
Exocrine
Acini produce digestive
enzymes
Regions: Head, body, tail
Secretions
Pancreatic juice (exocrine) Trypsin
Chymotrypsin
Carboxypeptidase Pancreatic amylase
Pancreatic lipases
Enzymes that reduce DNAand ribonucleic acid
L I i
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Large Intestine:
Extends from ileocecal junction to anus
Consists of cecum, colon, rectum, anal canal
Movements sluggish (18-24 hours)
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Large Intestine
Cecum Blind sac, vermiform appendix attached
Colon Ascending, transverse, descending, sigmoid
Rectum Straight muscular tube
Anal canal Internal anal sphincter (smooth muscle) External anal sphincter (skeletal muscle)
Hemorrhoids: Vein enlargement or inflammation
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Movement in Large Intestine
Mass movements Common after meals
Local reflexes in enteric plexus Gastrocolic: Initiated by stomach
Duodenocolic: Initiated by duodenum
Defecation reflex Distension of the rectal wall by feces
Defecation Usually accompanied by voluntary movements to expel feces
through abdominal cavity pressure caused by inspiration
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Digestion Absorption
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Digestion, Absorption,
Transport
Digestion
Breakdown of food molecules for absorption into
circulation
Mechanical: Breaks large food particles to small
Chemical: Breaking of covalent bonds by digestive
enzymes
Absorption and transport Molecules are moved out of digestive tract and into
circulation for distribution throughout body
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Functions of the Liver
Bile production Salts emulsify fats, contain pigments as bilirubin
Storage Glycogen, fat, vitamins, copper and iron
Nutrient interconversion
Detoxification Hepatocytes remove ammonia and convert to urea
Phagocytosis Kupffer cells phagocytize worn-out and dying red and white blood cells,
some bacteria
Synthesis Albumins, fibrinogen, globulins, heparin, clotting factors
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Lipoproteins
Types
Chylomicrons
Enter lymph
VLDL LDL
Transports cholesterol
to cells
HDL Transports cholesterol
from cells to liver
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W d I
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Water and Ions:
Water Can move in either direction
across wall of small intestine
depending on osmotic
gradients
Ions
Sodium, potassium, calcium,
magnesium, phosphate are
actively transported
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