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53 Cards in this Set
- Front
- Back
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Digestive system
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(mostly) one way tube through body, mouth to anus [aka GI tract] + accessory glands (salivary, liver & pancreas)
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Digestive system Function
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: move nutrients (food) into body cells
– Requires food in, break-down, absorb, & remove undigested material |
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Digestive system Path
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Oral cavity -> pharynx -> esophagus -> stomach -> small intestine -> large intestine -> anus
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Tissue layers (tunics): inner -> outer
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– Mucosa: mucous epithelium + connective + muscle tissue
– Submucosa: LCT + nerves (plexus) + blood vessels + glands – Muscularis: smooth muscle (enteric system) – Serosa (epithelia + CT) OR adventitia (CT found in surrounding tissue) |
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Mucosa
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mucous epithelium + connective + muscle tissue
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Submucosa
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LCT + nerves (plexus) + blood vessels + glands
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Muscularis
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smooth muscle (enteric system)
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Serosa OR adventitia
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Serosa (epithelia + CT) OR adventitia (CT found in surrounding tissue)
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Oral Cavity
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• Food breakdown initiates: mechanical + chemical
– Teeth = mastication (with cheeks, lips, tongue) • Baby/milk teeth (primary): 20 • Adult teeth (secondary): 32 • Incisors + canines + premolars + molars (+wisdom) • Teeth parts: Crown, neck, root |
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Food breakdown initiates: mechanical + chemical
– Teeth |
mastication (with cheeks, lips, tongue)
• Baby/milk teeth (primary): 20 • Adult teeth (secondary): 32 • Incisors + canines + premolars + molars (+wisdom) • Teeth parts: Crown, neck, root |
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Oral Cavity Con’t
• Salivary glands |
= chemical breakdown
– Parotid (inflames during mumps) [serous] – Submandibular [serous] – Sublingual [mucous] |
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Saliva
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• All 3 glands secrete max of ~1.5L of saliva per day
– Saliva is watery mix of enzymes + mucous – Enzymes are catalysts (salivary amylase starts carbohydrate digestion) – Also lysozyme present: digests bacteria • Immune protection key since digestive system is 2nd largest internal organ in contact w/outside |
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Saliva
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is watery mix of enzymes + mucous
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Enzymes
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are catalysts (salivary amylase starts carbohydrate digestion)
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Saliva:
Also lysozyme present |
digests bacteria
• Immune protection key since digestive system is 2nd largest internal organ in contact w/outside |
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Pharynx + Esophagus
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• Transport from oral cavity to stomach via peristalsis
• Sphincters = muscular rings that prevent backflow – Esophageal sphincters present at superior & inferior regions of esophagus (against stomach = cardiac sphincter - heartburn?) • Tongue pushes bolus (‘food ball’) to back of throat, enters pharynx; pharyngeal constrictor muscles press into esophagus – Soft palate prevents bolus moving into nasal cavity – Epigottis prevents bolus entering lungs |
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peristalsis
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Transport from oral cavity to stomach
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Sphincters
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= muscular rings that prevent backflow
– Esophageal sphincters present at superior & inferior regions of esophagus (against stomach = cardiac sphincter - heartburn?) |
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bolus
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Tongue pushes bolus (‘food ball’) to back of throat, enters pharynx; pharyngeal constrictor muscles press into esophagus
– Soft palate prevents bolus moving into nasal cavity – Epigottis prevents bolus entering lungs |
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Stomach
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• (cardiac sphincter), cardiac region, fundus, body, pyloric region (aka antrum) (pyloric sphincter)
• Stomach = muscular bag for mechanical & chemical breakdown – 3 muscle layers in opposing directions – Mucosa + submucosa lie in rugae when stomach is empty (allows expansion) |
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Stomach lining
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: gastric pits hold gastric glands
– Surface mucous cells line pits – Glands contain: 1. Mucosal neck cells (mucous) 2. Parietal cells (HCl + intrinsic factor) 3. Endocrine cells (regulatory chemicals) 4. Chief cells (pepsinogen => pepsin) |
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Stomach Glands contain:
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1. Mucosal neck cells (mucous)
2. Parietal cells (HCl + intrinsic factor) 3. Endocrine cells (regulatory chemicals) 4. Chief cells (pepsinogen => pepsin) |
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Stomach Regulation
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• Up to 2L of secretions per day in stomach
– Secretions + food bolus + mechanical breakdown = chyme • Control/regulation: – Cephalic phase (sensory perception of food => brain; stomach secretions – Gastric phase (response to food present in stomach through stretching + peptides; stomach secretions) – Intestinal phase (response to food leaving stomach & entering sm intestine; stomach secretions) |
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chyme
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Secretions + food bolus + mechanical breakdown
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Cephalic phase
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(sensory perception of food => brain; stomach secretions
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Gastric phase
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(response to food present in stomach through stretching + peptides; stomach secretions)
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Intestinal phase
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(response to food leaving stomach & entering sm intestine; stomach secretions)
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Stomach Circulation
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Stomach muscles contract in different directions to achieve movement of chyme
– Mixing waves move liquid chyme toward pyloric sphincter; opens slightly to release sm amount into intestine • Emptying controlled (chyme has optimum time spent in stomach - depends on composition [ie what you ate]) |
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Intestines
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• Small & large (colon): primary job = absorption (nutrients + water)
• Accessory glands help with breakdown of food – Liver – Pancreas |
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– Liver
– Pancreas |
Accessory glands help with breakdown of food
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Small & large (colon):
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primary job = absorption (nutrients + water)
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Small Intestine
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• 3 sections: duodenum, jejunum, ileum
• Duodenum: first, shortest section – From pyloric sphincter chyme moves into sm. intestine – Liver (via common bile duct) and pancreas (pancreatic duct) secrete to help digestion |
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Duodenum
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first, shortest section
– From pyloric sphincter chyme moves into sm. intestine – Liver (via common bile duct) and pancreas (pancreatic duct) secrete to help digestion |
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Liver
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• 2 large lobes (R & L) + 2 smaller lobes (caudate & quadrate)
• Major blood vessels = hepatic artery + hepatic veins; hepatic portal vein picks up nutrients from sm. intestine into liver for screening/detox before distribution • Liver has hepatocytes, which produce bile -> hepatic ducts (combines w/cystic duct from gallbladder) to form common bile duct -> duodenum via duodenal papilla |
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Liver has hepatocytes
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which produce bile -> hepatic ducts (combines w/cystic duct from gallbladder) to form common bile duct -> duodenum via duodenal papilla
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Bile
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• Digests lipids
• Mostly composed of bile salts (emulisifiers) & excretory products (cholesterol, fats, & pigments (esp. bilirubin, from breakdown of RBCs) – Lack of bilirubin release causes buildup elsewhere (jaundice), dark urine, & colorless feces |
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bilirubin
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breakdown of RBCs
Lack of bilirubin release causes buildup elsewhere (jaundice), dark urine, & colorless feces |
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Summary of Liver Functions
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Digestion, Excretion, Nutrient Storage, Nutrient Conversion, Detoxification of harmful chemicals, synthesis of new molecules.
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Pancreas
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• Endocrine (secrete into blood) & exocrine (secrete onto surface) tissue
– Endocrine: pancreatic islets [insulin & glucagon] – Exocrine: acini -> pancreatic duct -> duodenum • Major jobs of the pancreas in digestion: – Reduce acidity (release bicarbonate HCO3-) • Denatures pepsin – Release digestive enzymes • Trypsin, chymotrypsin, carboxypeptidase [proteins] • Pancreatic amylase [carbs] • Lipase [lipids] • Nucleases [nucleic acids] |
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Pancreas
• Endocrine & exocrine tissue |
Endocrine (secrete into blood) pancreatic islets [insulin & glucagon] & exocrine (secrete onto surface) tissue : acini -> pancreatic duct -> duodenum
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Major jobs of the pancreas in digestion
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– Reduce acidity (release bicarbonate HCO3-)
• Denatures pepsin – Release digestive enzymes • Trypsin, chymotrypsin, carboxypeptidase [proteins] • Pancreatic amylase [carbs] • Lipase [lipids] • Nucleases [nucleic acids] |
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Small Intestine Anatomy
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• Roles in digestion + absorption
• Increase surface area to maximize absorption – Accomplished through: circular folds, villi (‘finger-like’ projections), & microvilli (villi on the villi) – Mucosa = simple columnar epithelium 1. Absorptive cells (secrete enzymes, absorb nutrients) 2. Goblet cells (secrete mucus) 3. Granular cells (bacterial defense/immunity) 4. Endocrine cells (secrete hormones) |
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Small Intestine Anatomy
• Increase surface area to maximize absorption |
– Accomplished through: circular folds, villi (‘finger-like’ projections), & microvilli (villi on the villi)
– Mucosa = simple columnar epithelium 1. Absorptive cells (secrete enzymes, absorb nutrients) 2. Goblet cells (secrete mucus) 3. Granular cells (bacterial defense/immunity) 4. Endocrine cells (secrete hormones) |
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Mucosa = simple columnar epithelium
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1. Absorptive cells (secrete enzymes, absorb nutrients)
2. Goblet cells (secrete mucus) 3. Granular cells (bacterial defense/immunity) 4. Endocrine cells (secrete hormones) |
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Small Intestine
Absorption |
• Mesentary = membrane that holds sm. intestine to body cavity walls; lined with
vessels (absorb nutrients), lymphatic vessels (+ nodules = Peyer patches) (immune response) • Mix of contractions in intestine help spread food out to max. food absorption – Peristaltic contractions: long, directional (1-way) – Segmental contractions: short, 2-way |
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Mesentary
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membrane that holds sm. intestine to body cavity walls; lined with
vessels (absorb nutrients), lymphatic vessels (+ nodules = Peyer patches) (immune response) |
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Large Intestine
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• Move from ilium to large intestine via ileocecal junction
• Enter cecum, which attaches to appendix • After cecum, enter colon: ascending, transverse, & decending into sigmoid colon leading to rectum (muscular tunic is thick here) into anal canal: internal & external anal sphincters control excretion |
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Large Intestine
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: re-absorb water & bile salts (recycling); transform chyme into feces
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Large Intestine cont.
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Feces physically stimulate the rectal wall, inducing defecation reflex -> relaxation of internal anal sphincter (involuntary); IF external anal sphincter (skeletal muscle - voluntary) also relaxes, feces expelled
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Digestion in Detail
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• Different macromolecules digested, absorbed in different regions
– Stomach absorbs very small molecules via diffusion – Most absorption of nutrients = duodenum & jejunum (+ a little ileum) – Most absorption of water = colon |
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Carbohydrates
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• Begin breakdown in oral cavity (salivary amylase); also mechanical breakdown
• In stomach, gastric juice, contractions continue breakdown • Pancreatic amylase in sm intestine – After absorption, move to liver, where simple sugars -> glucose [insulin is a hormone that helps glucose enter cells] |
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Proteins
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• Begin digestion in stomach via pepsin (activated pepsinogen)
• Sm intestine secretions continue producing enzymes to break down proteins • Once in circulation, insulin also helps transport proteins into cells |
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Lipids
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• No digestion in oral cavity OR stomach because water does not break them down (hydrophobic)
• Bile salts from liver/gallbladder emulsify to allow digestion; lipase from pancreas continues digestion of smaller droplets (micelles) of lipids • Absorbed by cells, then transformed into necessary molecules |
