Digestive system Flashcards Preview

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Flashcards in Digestive system Deck (47):
1

Digestive tract/alimentary tract or canal

Tube from oral cavity to anus

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GI tract

Refers to stomach and intestines

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Accessory organs

Primarily glands
Secrete fluids into tract

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Ingestion - function

Introduction of food into the stomach

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Mastication

Chewing
Increases surface area

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Propulsion - function

Two types
Deglutition
Peristalsis

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Deglutition

Swallowing

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Peristalsis

Moves material through digestive tract

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Secretion - function

Mucus - along entire digestive tract to lubricate food
Water - food easier to digest and absorb
Bile - emulsifies fats
Enzymes - chemical digestion

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Digestion - function

Mechanical and chemical

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Absorption - function

Movement from tract into circulation or lymph

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Elimination - function

Waste products removed from body
Defecation

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Functions of digestive system

Ingestion
Mastication
Propulsion
Mixing
Secretion
Digestion
Absorption
Eliminator

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Mixing - function

Wave of smooth muscle relaxation moves ahead of bolus
Wave of contraction of smooth muscle behind bolus

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Nervous regulation of digestive system (local)

Enteric nervous system
Coordinates peristalsis and regulates local reflexes

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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)

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Chemical regulation of digestive system

Production of hormones (gastrin, secretin)
Production of paracrine chemicals like histamine

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Saliva produced by

Compound alveolar salivary glands

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Saliva function

Prevent bacteria infection
Lubrication
Break down starch (salivary amylase)
Help form bolus for swallowing

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Salivary production caused by

Parasympathetic input

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Stomach openings

Gastroesophageal - from esophagus
Pyloric - to duodenum

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Small intestine

Site of greatest amount of digestion and absorption of nutrients and water

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Divisions of small intestine

Duodenum - first 25cm
Jejunum - 2.5m
Ileum - 3.5m

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Major sites of nutrient absorption

Duodenum and Jejunum

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Between Jejunum and Ileum there is a gradual decrease in

Diameter
Thickness of intestinal walls
Number of circular folds
Number of vili

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Hepatic ducts

Carry bile from liver lobes
Combine to form common hepatic duct

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Common hepatic duct

Combines with cystic duct from gallbladder to form common bile duct

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Common bile duct

combine with pancreatic duct to form hepatopancreatic ampulla

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Hepatopancreatic ampulla

Empties bile and pancreatic secretions into duodenum at major duodenal papilla

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Accessory pancreatica duct

Empties pancreatic secretions into duodenum at minor duodenal papilla

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Functions of the liver

Bile production
Storage
Nutrient interconversion
Detoxification
Phagocytosis
Synthesis

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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

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Storage - function of liver

Glycogen, fat, vitamins, copper and iron

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Detoxification - function of liver

Hepatocytes remove ammonia and convert to urea

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Synthesis - function of liver

Albumins
Fibrinogen
Globulins
Heparin
Clotting factors

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Pancreas - endocrine

Pancreatic islets
Produce insulin, glucose and somatostatin

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Pancreas - exocrine

Grape-like clusters from lobules separated by septa

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Large intestine

Chyme converted to faeces
90% volume of chyme is reabsorbed in large intestine

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Large intestine divisions

Cecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal

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Cecum

Appendix attached
Part of large intestine

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Rectum

Straight muscular tube
Thick muscular tunic

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Anal canal

Internal anal sphincter - smooth muscle
External anal sphincter - skeletal muscle

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Digestion

Breakdown of food molecules for absorption into circulation

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Mechanical digestion

Breaks large food particles to small

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Chemical digestion

Breaking of covalent bonds by digestive enzymes

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Absorption and transport

Molecules moved out of digestive tract and into circulation for distribution throughout body

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Water and ions in small intestine

Water - move in either direction depending on gradient
Ions - actively transported