Module 7 - Digestive Tract Flashcards
Gastrointestinal Tract
Gastrointestinal Tract
Tube open at both ends
Mouth to anus
Processes food for use during transit
Functional Structures
Functional Segments
Mouth
Pharynx
Esophagus
Stomach
Small Intestine
Large Intestine
Accessory Structures
Accessory Structures
Teeth
Tongue
Salivary glands
Liver
Gallbladder
Pancreas
Digestion Processes
Digestion Processes
Ingestion
Secretion
Mixing and Propulsion
Digestion
Absorption
Defecation
Secretion
Secretion – chemical break down
Cells in walls of GI & accessory organs
Release of water, acid, buffers, and enzymes
Lumen of tract
Mixing and Propulsion
Mixing and Propulsion – alternating contractions and relaxation
Peristalsis
Smooth muscle
Mixing with digestive juices
Digestion
Digestion – breaking food down into small molecules
Mechanical – physical – teething breaking apart – stomach tossing around
Chemical – secretions – molecular scissors – break down molecules into smaller
Absorption
Absorption – body taking in nutrients to be distributed by cells Blood – nutrients
Lymph – fats
Defecation
Defecation – emptying indigestible substances from rectum
Walls of GI Tract – Alimentary Canal
Walls of GI Tract – Alimentary Canal
Mucosa – mucous membrane
Submucosa – dense connective tissue
Muscalaris – double layer smooth muscle
Serosa – visceral peritoneum
Mucosa – mucous membrane - Sublayers
Mucosa – mucous membrane
Gut epithelium
Lamina propria
Muscularis Mucosa
Mucosa - Gut epithelium
Gut epithelium – mucous production
Direct contract with food
Protective layer – non-keratinized stratified cells – secretion and absorption
Mucus-secreting cells
Endocrine cells for hormones
Mucosa - Lamina Propria
Lamina propria – loose connective tissue
Blood and lymph vessels – take nutrients
Immune function – clusters of lymphocytes
Make up villi in small intestine
Mucosa - Muscularis Mucosa
Muscularis Mucosa – smooth muscle – constant tension
Causes folding of mucosal layer – increasing surface area for digestion and absorption
Submucosa
Submucosa – dense connective tissue
Highly vascular - Blood vessels
Lymph tissue
Submucosal glands – secreting digestive enzymes
Submucosal plexus – regulate secretions
Muscalaris
Muscalaris – double layer smooth muscle
Nerve supply
Myenteric plexus – controls motility
fibers for ANS – restrict or promote digestion – fight or flight – rest and digest
Mouth pharynx, and superior esophagus – skeletal muscle for voluntary swallowing
Anal sphincter – skeletal muscle – voluntary defecation
Inner circular layer
Outer longitudinal layer – Both promote mechanical digestion – move food along
Serosa – visceral peritoneum
Serosa – visceral peritoneum
Squamous epithelial surrounded by loose connective tissue
Only in organs at abdominal cavity
Peritoneum
Peritoneum
Protection
Largest serous membrane
Folds
Greater Omentum
Falciform
Lesser Omentum
Mesentery
Mesocolon
Peritoneum - Parietal Layer
Parietal layer – lines abdominal cavity wall
Peritoneal cavity
Peritoneal cavity – space b/w – serous fluid – reduces friction
Peritoneum - Visceral Layer
Visceral layer – envelopes abdominal organs – outer layer of GI tract
Retroperitoneal
Retroperitoneal – organs behind abdominal wall – kidneys & pancreas - posterior
Peritoneum - Greater Omentum
Greater Omentum – apron-like – Superficial to small intestine and transverse colon
Fat deposition in overweight people
Peritoneum - Falciform
Falciform – Anchors liver to anterior ab wall – Inferior border of diaphragm
Peritoneum - Lesser Omentum
Lesser Omentum – Suspends the stomach from inferior border of liver
Pathway for structure to connect to liver
Peritoneum - Mesentery
Mesentery – Vertical band of tissue anterior to lumber verte – Anchors all small intestine except duodenum
Peritoneum - Mesocolon
Mesocolon – Attaches two portions of large intestine to ab wall
Salivary Glands
Salivary Glands
Saliva – 99.5% water and 0.5% solutes – salts, dissolved gases, organic substances, and enzymes
1.5L daily
pH 7-8 (alkaline)
Major glands located outside of mouth – pour product into ducts – empty into oral cavity
Parotid
Submandibular (submaxillary)
Sublingual glands – below tongue – sublingual ducts
Rest – buccal glands
Salvia Function
Moisten and lube lining of mouth and pharynx
Moisten, soften, and dissolve food – especially carbs
Clean mouth and teeth
Salivary Amylase breaks down food
Salivary Gland - Parotid
Parotid – b/w skin & masseter muscle (near ears) – parotid duct – second upper molar
Salivary Gland - Submandibular
Submandibular (submaxillary) – floor of mouth – submandibular ducts
Salivary Glands - Sublingual
Sublingual glands – below tongue – sublingual ducts
Salivary Glands - Buccal Glands
buccal glands (cheeks) in mucous membrane
Pharynx
Pharynx
runs from nostrils to esophagus & larynx
Swallowing
Short tube of skeletal muscle
Lined with mucous membrane
Subdivisions
Nasopharynx – breathing and speech
Oropharynx – respiratory & digestion
Laryngopharynx – resp & digs
Swallowing
Swallowing
Elevator skeletal muscle contracts – expands pharynx for bolus – push bolus
Elevator relaxes
Constrictor muscles contract – force bolus to esophagus
Soft palate & uvula close off nasopharynx
Larynx pulled superiorly
Epiglottis – folds coving glottis – blocks trachea – “wrong way”
Esophagus
Esophagus
Muscular tube – behind trachea
Lined stratified squamous epithelium
Connects pharynx to stomach – thru mediastinum
Collapsed when not swallowing
Penetrates diaphragm – esophageal hiatus
Upper 2/3s of esophagus – smooth and skeletal muscle
Lower 1/3 – smooth muscle
Peristalsis
Peristalsis – rhythmic waves of muscle contraction in Muscularis to move bolus
Upper esophageal sphincter
Upper esophageal sphincter – b/w trachea and eso – controls food movement from laryngopharynx to esophagus
Lower esophageal sphincter
Lower esophageal sphincter – entrance to stomach – relaxed food enters – contracts to keep stomach acids (chime) from coming up
Deglutition – phases
Deglutition – phases
Voluntary – chewing complete – tongue goes upward – bolus to oropharynx
Pharyngeal – uvual and soft palate move upward to close nasopharynx
Esophageal – peristalsis
Stomach
Stomach
Links esophagus to duodenum
Highly active – contracting and changing position and size
Stretch to hold 4L
Absence of food – deflates inward
Temp holding chamber – slowly releases to duodenum
Continues carb digestion
Initiates digestion of proteins and triglycerides
Stomach - Regions
regions
Cardia – connects to esophagus – food passageway
Fundus – roof – top
Body – main part
Pylorus – funnel-shaped – connects to duodenum
Pyloric antrum – connects to body
Pyloric sphincter – at duodenum – controls emptying
Stomach - Lining
Lining
Mucosa
Surface Mucous cells – simple columnar cells
Lamina propria – gastric pits and glands – secrete gastric juices
Inner oblique smooth muscle added to Muscularis – helps churn and mix
Gastric Glands
Exocrine Glands
Mucous neck cells
Chief cells
Parietal cells
Enteroendocrine cells
Stomach - Mucous neck cells
Mucous neck cells – secrete thin acidic mucus
Stomach - Chief cells
Chief cells – pepsinogen (inactive pepsin) & gastric lipase – breaks down molecules
Stomach - Parietal Cells
Parietal – secrets HCI and intrinsic factor
Hydrochloric acid – activates pepsin (digestive enzyme) – breaks down proteins
Intrinsic – B12 absorption – allows DNA synthesis – RBC production
Stomach - Digestion
Mechanical digestion – peristaltic movements – mixing waves
Chemical digestion – conversion of proteins into peptide by Pepsin – pH2 – acidic
Gastric emptying – periodic release of chyme into duodenum
Pancreas
Pancreas
In retroperitoneum – behind stomach
Head into c-shaped curve of duodenum
End at hilum of spleen
Exocrine and endocrine gland
Pancreas - Exocrine
Exocrine – cell clusters – Acinus – produce pancreatic juice into tiny ducts – merge into two dominant ducts
Pancreatic (Wirsung) duct fuses w/ common bile duct
Smooth muscle sphincter controls release of juice & bile into small intest.
Accessory (Santorini) duct – runs into duodenum
Pancreas - Endocrine
Endocrine – islets of Langerhans – produce hormones
Hormone pancreatic polypeptide
Insulin & glucagon – b & a cells
Somatostatin
Pancreatic Juice
Pancreatic Juice – 1L/day – clear – water w/ salt, sodium bicarbonate, & digestive enzymes
Ductal cells
Pancreatic enzymes
Active enzymes
Pancreatic Juice - Ductal cells
Ductal cells around pancreatic duct ends – Sodium bicarbonate – alkaline – neutralized gastric juices in chyme
Pancreatic Juice - Pancreatic Enzymes
Pancreatic enzymes to be activated digest sugars, proteins, and fats
Inactive enzymes – would eat pancreas – need to be activated by enzymes in duodenum – activated by enteroendocrine in duodenum
Proteins – trypsin, chymotrypsin, & carboxypeptidase
Pancreatic Juice - Active Enzymes
Active enzymes
Starch – pancreatic amylase
Fat – lipase
Nucleic acids – ribonuclease and deoxyribonuclease
Pancreas Regulation
Regulated by parasympathetic NS and hormones
Acidic chyme enters duodenum – stims secretin by enteroendocrine cells – tells pancreas to release sodium bicarb juice – balances HCI produced in stomach
Proteins and fats in duodenum – stims CCK – stims acini – secrete pancreatic juice and enhances secretin secretion
Liver
Liver
Accessory digestive organ
Metabolism and regulation
Two primary lobes – larger right & smaller left – separated by Falciform Ligament
Lobes made up of lobules – each arranged by central vein
Hepatocytes
Sinusoids
Kupffer’s cells – macrophages
Connected to abdominal wall and diaphragm
Liver - Porta hepatis
Porta hepatis – gate – hepatic artery and hepatic portal vein enter liver
Hepatic artery
Hepatic artery – delivers oxygenated blood from heart to liver
Hepatic portal vein
Hepatic portal vein – delivers partially deoxygenated blood w/ nutrients, toxins, and waste – absorbed by small intest. – most O2 for liver is here
Blood in the liver
Blood w/ nutrients, toxins, and waste pass thru – everything is filtered
Nutrients – back into blood – for cells
Drains into central vein
Then hepatic vein
To inferior vena cava
Gallbladder
Gallbladder – sac located in depression posterior to liver
Stores bile
No submucosa
Muscularis – ejects bile into cystic duct (merges into common duct)
Outer layer – visceral peritoneum
Bile
Bile – produced by hepatocytes
Yellow-brown alkaline solution
Water, bile salts, bile pigments, phospholipids, electrolytes, proteins, cholesterol
Breaks down fats – emulsification
Secretion regulated by nervous and hormones
Absorption of fat-soluble vitamins – A, D, E, & K
Emulsification of triglycerides
Emulsification of triglycerides – bile salts and phospholipids
Reabsorbed by enterohepatic circulation – reused
Small Intestine
Small Intestine
Primary digestive organ
All absorption
Large surface area for absorption
Coil tube of smooth muscle
Duodenum
Duodenum – after stomach
Chyme is slowly release by Pyloric sphincter
Hepatopancreatic ampulla – opening for bile and pancreatic juices enter – controlled by hepatopancreatic sphincter
Jejunum
Jejunum – more villi
Ileum
Ileum – largest section
Thicker, more vascular, more developed mucosal folds
Joins the Cecum (larger intest.) at ileocecal sphincter
Peyer’s patches – lymph tissue – keeps bacteria from blood
Small Intest - Mucosa
Mucosa
Absorptive cells
Goblet cells – secrete mucus
Endocrine cells – hormones producing
Small Intest - Absorptive cells
Absorptive cells
Circular folds
Villi
Microvilli
Small Intest - Absorptive cells -Circular folds
Circular folds – plicae circulares – deep ridges in mucosa and sub – being at end of duodenum and end middle ileum – facilitate absorption – chyme will spiral slowly = more absorption
Small Intest - Absorptive cells - Villi
Villi – hair-like vascular projections – increase surface area – each contains capillary bed – contain Lacteal – proteins and carbs nutrients drain straight into blood – fats drain into lacteal
Small Intest - Absorptive cells - Microvilli
Microvilli – cylindrical surface extensions of plasma membrane – brush border – finish digesting carbs and proteins – enhance absorption – contain enzymes
Small Intest - Submucosa
Submucosa – contains duodenal glands – secrete alkaline mucus – neutralize gastric acid in chime
Small Intest - Intestinal Juice
Intestinal juice – vehicle of absorption of substances from chyme
Blood in Small Intest
Superior mesenteric artery – blood supply
Superior mesenteric vein – drains
Nutrient rich blood – carried to liver – hepatic portal vein
Phases of Digestion
Phase of digestion
Cephalic phase
Gastric phase
Intestinal phase
Cephalic Phase of Digestion
Cephalic phase – saliva & gastric juice – sight, smell, thought of food
Hypothalamus stims medulla
Medulla tells parasym. To stim gastic secretion
Gastric Phase of Digestion
Gastric phase – food enter stomach – gastric juices breakdown – chyme leaves
pH increases – stims gastric breakdown of food
Intestinal Phase of Digestion
Intestinal phase – chyme enters small intest. – digestion occurs – acidity is buffered
Small Intest - Digestion
Mechanical Digestion – movement of chyme
Segmentation
Migrating motility complex
Chemical Digestion – breakdown of molecules
Segmentation
Segmentation – smooth muscle contract and relax – pinching chyme – pushes it back and forth – mixing with digestive juices – pushes particle against mucosa for absorption
Migrating motility complex
Migrating motility complex – peristalsis – transport movement – duodenum secrets motilin to stim – circular pattern of contraction – push everything towards large intest.
Proteins and carbs digestion
Proteins and carbs digestion completed
Proteins – amino acids – begins in stomach
Carbs – monosaccharides
Lipid Digestion
Lipid – emulsification with bile salts and pancreatic juices
Bile breaks into triglycerides droplets
Pancreatic juices hydrolyze triglycerides – fatty acids & monoglycerides
Not water soluble – needs fluid medium for absorption – osmosis
Carb Absorption
Carbs –polysaccharides – starch, glycogen, and cellulose
absorbed into blood capillaries
broken into Monosaccharides – Glucose, galactose, and fructose
gastric juices trigger enteroendocrine cells – chemical into bloodstream – CCK
CCK – stims pancreas to release juice – a-amylase – breaks down poly bonds
Disaccharides– maltose, malt triose, sucrose, lactose – pulls water towards it
Brush border cells – produce enzymes – breakdown disaccharides into monosaccharides
Monosaccharides – Glucose, fructose, galactose
Cell – Na+ comes in – glucose & galactose uses this to get into cell – sodium glucose transporter – fructose moves thru its own channel – glucose transporter 5 channel
Glucose transporters bring monosaccharides into blood stream
CCK function
CCK – stims pancreas to release juice – a-amylase – breaks down poly bonds
CCK - triggers gallbladder contraction to release bile into small intestine - breaks down fats
Absorption - Proteins
Absorption - Proteins
active transport into blood capillaries of villi
Single amino acids, dipeptides, and tripeptides
Gastric pits in stomach
Chief cells – release pepsinogen – inactive when stored
Parietal cells – release hydrochloric acid – activates pepsinogen to pepsin
Denature – H+ breakdown the protein – unravels proteins – 3D to line
Pepsin – cuts up unraveled protein
Small intestine – polypeptides go
Enteroendocrine cells – releases CCK – stims pancreas to release juice w/ inactive proteases – stim enterokinase cells in duodenum activate proteases
Cut up amino binds in polypeptides– with Brush border in villi
Enterocyte Cell – Na+ brings amino acids, di and tripeptides
Bloodstream – channels bring amino – facilitated diffusion to liver
Nucleic Acid Absorption
Nucleic acids – active transport into blood
Pentose sugars, phosphates, and nitrogenous bases
Electrolyte Absorption
Electrolytes – active transport
Dissociate into ions
Water Absorption
Water – osmosis – lumen of intestine – epithelial cells in capillaries
Vitamin Absorption
Vitamins – Fat soluble (A, D, E, & K) – ingested dietary lipids in micelles – simple diffusion – Water (B & C) – simple diffusion
Dietary Lipids Absorption
Dietary Lipids – simple diffusion
Lipid Absorption
Triglycerides, Monoglycerides & long fatty chains – Micelles
Micelles
After fats broken down into small bits following bile and pancreatic juices – push
Bile salts facilitate the diffusion on the intestinal wall – across membrane’s bilayer
Bile salts left behind – reused – back to liver
Golgi packages separated fats – into triglycerides – resynthesize w/ ApoB (hat) – CHYLOMICRON
Chylomicron – goes into lymph – distributes into organs of the body
Lipid Absorption - Micelles
Micelles – tiny lipid-transport compound made of bile salts and phospholipids w/ fatty acid and monoglyceride cord
Large Intestine
Large Intestine
Finish absorption of nutrients, electrolytes & water
Synthesize some vitamins
Forms and eliminates feces – defecation
Appendix to anus
Regions of Large Intestine
4 regions
Cecum
Colon
Rectum
Anal Canal
Cecum
Cecum – opens from small intest. via ileocecal valve – controls flow of chyme – continued absorption of water and salts
Appendix
Appendix
Appendix – winding tube attached to cecum – lymph tissue – repopulates the gut with flora
Colon Subdivision
Colon – ascending, transverse, descending, & sigmoid
Rectum
Rectum – separates feces from gases – bacteria flora creates gas during fermentation
Anal Canal
Anal Canal – opens to exterior – sphincters control defecation
Internal – smooth muscle – involuntary
External – skeletal muscle – voluntary
Large Intest - Mucosa
Mucosa – no circular folds or villi – contains lots of enterocytes and goblet cells
Enterocytes – absorb water and salts – vitamins produced by flora
Goblet cells – secrete mucus to ease feces
Large Intest - Muscularis
Muscularis – specialized muscles – taeniae coli – contract – gather colon into pouches
Movements – churching, peristalsis, and mass peristalsis
Hepatitis
Hepatitis
Inflammation of liver – caused by viruses, autoimmune disorders, alcohol, drugs, and toxic chemicals
Symptoms – yellowish skin, poor appetite, abdominal pain
Treatment – meds and transplant
A, B, C, D, & E – most common A, B, & C
Hepatitis A
A – Fecal-oral infection
highly contagious – spread by fecal contamination of food and fomites
mild and acute (short term)
Hepatitis B
B – sexual contact, syringes, razors, tears and saliva
Chronic inflammation
Liver failure and cancer
Hepatitis C
C – sexual contact, syringes, razors, tears and saliva
Can be passed at birth
25% can defeat – 75% infected for life
