Digestive system Flashcards
Digestive tract/alimentary tract or canal
Tube from oral cavity to anus
GI tract
Refers to stomach and intestines
Accessory organs
Primarily glands
Secrete fluids into tract
Ingestion - function
Introduction of food into the stomach
Mastication
Chewing
Increases surface area
Propulsion - function
Two types
Deglutition
Peristalsis
Deglutition
Swallowing
Peristalsis
Moves material through digestive tract
Secretion - function
Mucus - along entire digestive tract to lubricate food
Water - food easier to digest and absorb
Bile - emulsifies fats
Enzymes - chemical digestion
Digestion - function
Mechanical and chemical
Absorption - function
Movement from tract into circulation or lymph
Elimination - function
Waste products removed from body
Defecation
Functions of digestive system
Ingestion Mastication Propulsion Mixing Secretion Digestion Absorption Eliminator
Mixing - function
Wave of smooth muscle relaxation moves ahead of bolus
Wave of contraction of smooth muscle behind bolus
Nervous regulation of digestive system (local)
Enteric nervous system
Coordinates peristalsis and regulates local reflexes
Nervous regulation of digestive system (general)
Coordination with CNS
May initiate reflexes because of sight, cell or taste of food
Primarily parasympathetic
Sympathetic inhibits (muscle contraction, secretion, blood flow to digestive tract)
Chemical regulation of digestive system
Production of hormones (gastrin, secretin)
Production of paracrine chemicals like histamine
Saliva produced by
Compound alveolar salivary glands
Saliva function
Prevent bacteria infection
Lubrication
Break down starch (salivary amylase)
Help form bolus for swallowing
Salivary production caused by
Parasympathetic input
Stomach openings
Gastroesophageal - from esophagus
Pyloric - to duodenum
Small intestine
Site of greatest amount of digestion and absorption of nutrients and water
Divisions of small intestine
Duodenum - first 25cm
Jejunum - 2.5m
Ileum - 3.5m
Major sites of nutrient absorption
Duodenum and Jejunum
Between Jejunum and Ileum there is a gradual decrease in
Diameter
Thickness of intestinal walls
Number of circular folds
Number of vili
Hepatic ducts
Carry bile from liver lobes
Combine to form common hepatic duct
Common hepatic duct
Combines with cystic duct from gallbladder to form common bile duct
Common bile duct
combine with pancreatic duct to form hepatopancreatic ampulla
Hepatopancreatic ampulla
Empties bile and pancreatic secretions into duodenum at major duodenal papilla
Accessory pancreatica duct
Empties pancreatic secretions into duodenum at minor duodenal papilla
Functions of the liver
Bile production Storage Nutrient interconversion Detoxification Phagocytosis Synthesis
Bile production - function of liver
600 - 1000ml per day
Neutralises and dilutes stomach acid
Bile salts emulsify fats
Increase water and bicarbonate ion content of bile
Storage - function of liver
Glycogen, fat, vitamins, copper and iron
Detoxification - function of liver
Hepatocytes remove ammonia and convert to urea
Synthesis - function of liver
Albumins Fibrinogen Globulins Heparin Clotting factors
Pancreas - endocrine
Pancreatic islets
Produce insulin, glucose and somatostatin
Pancreas - exocrine
Grape-like clusters from lobules separated by septa
Large intestine
Chyme converted to faeces
90% volume of chyme is reabsorbed in large intestine
Large intestine divisions
Cecum Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Anal canal
Cecum
Appendix attached
Part of large intestine
Rectum
Straight muscular tube
Thick muscular tunic
Anal canal
Internal anal sphincter - smooth muscle
External anal sphincter - skeletal muscle
Digestion
Breakdown of food molecules for absorption into circulation
Mechanical digestion
Breaks large food particles to small
Chemical digestion
Breaking of covalent bonds by digestive enzymes
Absorption and transport
Molecules moved out of digestive tract and into circulation for distribution throughout body
Water and ions in small intestine
Water - move in either direction depending on gradient
Ions - actively transported