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53 Cards in this Set

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  • Back
Digestive system
(mostly) one way tube through body, mouth to anus [aka GI tract] + accessory glands (salivary, liver & pancreas)
Digestive system Function
: move nutrients (food) into body cells
– Requires food in, break-down, absorb, & remove undigested material
Digestive system Path
Oral cavity -> pharynx -> esophagus -> stomach -> small intestine -> large intestine -> anus
Tissue layers (tunics): inner -> outer
– 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)
Mucosa
mucous epithelium + connective + muscle tissue
Submucosa
LCT + nerves (plexus) + blood vessels + glands
Muscularis
smooth muscle (enteric system)
Serosa OR adventitia
Serosa (epithelia + CT) OR adventitia (CT found in surrounding tissue)
Oral Cavity
• 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
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
Oral Cavity Con’t
• Salivary glands
= chemical breakdown
– Parotid (inflames during mumps) [serous]
– Submandibular [serous]
– Sublingual [mucous]
Saliva
• 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
Saliva
is watery mix of enzymes + mucous
Enzymes
are catalysts (salivary amylase starts carbohydrate digestion)
Saliva:
Also lysozyme present
digests bacteria
• Immune protection key since digestive system is 2nd largest internal organ in contact w/outside
Pharynx + Esophagus
• 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
peristalsis
Transport from oral cavity to stomach
Sphincters
= muscular rings that prevent backflow
– Esophageal sphincters present at superior & inferior regions of esophagus (against stomach = cardiac sphincter - heartburn?)
bolus
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
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
Stomach
• (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)
Stomach lining
: 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)
Stomach Glands contain:
1. Mucosal neck cells (mucous)
2. Parietal cells (HCl + intrinsic factor)
3. Endocrine cells (regulatory chemicals)
4. Chief cells (pepsinogen => pepsin)
Stomach Regulation
• 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)
chyme
Secretions + food bolus + mechanical breakdown
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)
Stomach Circulation
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])
Intestines
• Small & large (colon): primary job = absorption (nutrients + water)
• Accessory glands help with breakdown of food
– Liver
– Pancreas
– Liver
– Pancreas
Accessory glands help with breakdown of food
Small & large (colon):
primary job = absorption (nutrients + water)
Small Intestine
• 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
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
Liver
• 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
Liver has hepatocytes
which produce bile -> hepatic ducts (combines w/cystic duct from gallbladder) to form common bile duct -> duodenum via duodenal papilla
Bile
• 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
bilirubin
breakdown of RBCs
Lack of bilirubin release causes buildup elsewhere (jaundice), dark urine, & colorless feces
Summary of Liver Functions
Digestion, Excretion, Nutrient Storage, Nutrient Conversion, Detoxification of harmful chemicals, synthesis of new molecules.
Pancreas
• 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]
Pancreas
• Endocrine & exocrine tissue
Endocrine (secrete into blood) pancreatic islets [insulin & glucagon] & exocrine (secrete onto surface) tissue : 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]
Small Intestine Anatomy
• 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)
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)
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)
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
Mesentary
membrane that holds sm. intestine to body cavity walls; lined with
vessels (absorb nutrients), lymphatic vessels (+ nodules = Peyer patches) (immune response)
Large Intestine
• 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
Large Intestine
• Function
: re-absorb water & bile salts (recycling); transform chyme into feces
Large Intestine cont.
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
Digestion in Detail
• 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
Carbohydrates
• 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]
Proteins
• 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
Lipids
• 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