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Name 5 key charachteristics about the GI system
- 1) series of hollow organs
- 2) separated by sphincters
- 3) specialized secretions
- 4) characteristic layered structure
- 5) dibgestion consists of mechanical and chemical processes
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Name 2 purposes for uptake of nutrients
- 1) energy replenishment
- 2) building blocks for metabolism (essential AA, fatty acids, minerals, vitamins)
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What is the difference between hunger/satiety and appetite?
hunger/satiety: regulates energy intake
appetite: regulates specific nutrient intake
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Name some stimulatory and inhibitory regulators of food intake
stimulatory: ghrelin (released by stomach during fasting)
- inhibitory:
- stomach stretch receptors;
- CCK, insulin, and PYY (gastro-intestinal hormones)
- leptin (released by growing fat cells)
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What factors control the conditions in the lumen of the GIT?
- 1) food motility
- 2) secretion of enzymes
- 3) acidity
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Describe parasymp innervation of the GIT
Vagus: esophagus, stomach, pancreas, a little to SI and LI, stimulates ENS
Sacral nerves: distal half of LI, anus, defecation reflexes
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Describe sympathetic innervation of the GIT
celiac ganglion and the meseteric ganglion
innervate all parts
release norepinephrine which inhibits peristalsis and increases sphincter tone
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List 4 major GI hormones
gastrin: released by stomach (releases HCL, increase intestine movement, release of pepsinogen)
Secretin: released by SI, pancrease secretes alkaline, pro-enzyme, stimulates intestinal motility
CCK: secreted by SI, secretion of proenzymes and bile
Gastric Inhibitory Peptide: insulin secretion, inhibits gastric secretion and motility
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Describe the 3 phases of digestion regulation
1) celiac: you know food is coming, increased salivation and blood flow, stomach motility inhibited, initiates secretions
2) Gastric phase: food is in stomach, increases blood flow, increases SM stimulation, secretion of bile, panc juices, intestinal juices, intestinal mobility
3) Intestinal phase: chyme in duodenum, inhibits stomach to prevent overloading, secretion of bile, panc juices, intest. juices, increase blood flow to intest., gallbladder constriction and relaxation of sphincter of Oddi
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List the muscles of the abdominal wall
Superficial to deep: Rectus abdominus, external oblique, internal oblique, transverse
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List the layers of the lateral abdominal wall
- Superficial to deep:
- skin, Camper's fascia, external oblique, internal oblique, transverse abdominal, transversalis fascia, parietal peritoneium
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what is the linea semilunaris
semilunar line that marks the border of the rectus abdominus
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List the layers of the anterior abdominal wall
skin, camper's fascia, external oblique apon., internal oblique apon., rectus abd., internal oblique apon., transvers abd. apon., transversalis fascia, parietal perit.
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What are the components of the inguinal region?
- inguinal ligament
- inguinal canal
- spermatic cord (round ligament in females)
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What ate the contents of the spermatic cord?
- Vas def.
- testicular a (off aorta)
- testicular v
- lymphatics
- Cremaster muscle (raise and lower testes based on temp)
- sympathetic fibres
- genital branch of genitofemoral n
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What is the difference between direct and indirect inguinal hernias?
indirect: enters deep inquinal ring, exits superficial inguinal ring, can cause strangulation
direct: inters in Hasselbach's triangle and exits superficial inguinal ring, more common in old men, less serious
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What does each saliva gland secrete
- parotid: watery, little mucus, amylase-rich
- submadibular: high in lysozyme
- lingual: mixed
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What are the functions of saliva
- lubrication
- amylase (breaks down starch)
- protective functions (mucins coat, acts as a buffer, control of water intake (dry mouth), antimicrobial, drug absorption
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Describe ho saliva is secreted
- 1) liquid comes from capillary
- 2) acinar cells add mucin, amylase, etc
- 3) primary secretion is isotonic with plasma
- 4) duct cells remove Na and add K (more K is added therefore secretion becomes more hypotonic)
- 5) add bicarbonate and remove CL AND Vice versa
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Describe the three phases of swallowing
- 1) voluntary phase: tongue moves bolus to back of mouth
- 2) pharyngeal phase: bolus activates pressure sensors, triggers reflexes in teh swallowing centers of the brain stem. close epiglottis, esophagal sphincter opens
- 3) esophagal phase: peristaltic wave. Primary wave is goes from pharynx to stomach, secondary waves continue in esophagus (if necessary) until food is all in stomach
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list the major cells in the gastric glands in the corpus
- 1) parietal cells (acid and intrinsic factor)
- 2) chief cells (pepsinogen)
- 3) mucous cells (secrete mucus, bicarbonate, sodium)
- 4) enterochromaffin-like (ECL) cells secrete histamine
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List the major cells in the gastric glands in the antrum
- 1) cheif cells (pepsinogen)
- 2) endocrine cells (gastrin, somatostatin)
NO PARIETAL CELLS AND THEREFORE NO ACID
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What are the 4 phases of acid secretion?
- 1) basal state: low rate, huge variation between individuals, low pH (no buffers)
- 2) Cephalic phase (food is coming): stimulates vagus nerve, stimulates H+ and gastrin, inhibits somatostatin (30% of secretion)
- 3) Gastric phase: distension of stomach stimulates vagus, dig protein activates antral G cells (gastrin) (50-60% of secretion)
- 4) Intestinal phase: intestinal cells and absorbed AA's cause small amount of secretion (5-10%)
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describe how the duodenum regulates stomach empyting based on the type of meal
- water/saline: leaves quickly
- acid meal: takes longer
- presence of lipids: takes even longer
Makes sure the duodenum doesn't get overloaded.
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Some side effects of gastric bypass surgery
- B12 deficiency
- can't convert Fe3 to Fe2
- need to regulate food intake
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How do pancreatic ducts cells make bicarbonate?
- 1) tubulovesicles have H+ pumps
- 2) t. vesicles move to the basilar membrane when duct cell is activated
- 3) pump H+ into the blood and HCO3- into the cell and ultimately into the duct.
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Discuss how proteins, carbs, and fats are broken down in the duodenum.
- proteins: trypsin, chymotrypsin, carboxypolypeptidase
- carbs: pancreatic amylase
- fat: pancreatic lipase, phospholipase, others
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Describe the different types of diarrhoea
-secretory: oversecretion of water, absorption cant cope, caused by bacterial toxins or overstim. of ENS
-defective ion transport: fat malapsorption, bile acids, diabetes, inflammatory mediators like histamine
-osmotic diarrhoea: hyperosmotic fluid in lumen, fermentation can cause hyperosmotic
-hypermotility of intestines: bacterial toxins
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List the hormones that affect peristalsis and motility
Increase motility: CCK, secretin, gastrin,
Increase peristalsis: motilin (hormone relseased after chyme turns alkaline)
Decrease peristalsis: enteroglucagon (when glucose and fat in chyme)
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describe the gastro-ileal reflex
- -fluidity of contents promotes emptying
- -pressure and chem irritation in ilium increase peristalsis and relaxes sphincter
- -pressure or chem irritation in cecum inhibits peristalsis and excites sphincter
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What happens to carbs after they are absorbed
- 1)Sent to liver
- 2) liver converts fructose and galactose to glucose
- 3) glucose released back into blood
- -enters cells for glycolysis and citric acid cycle
- -liver converts to glycogen (skeletal muscle) and TAG (adipose tissue)
- -
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What are the three sources of energy for adipose tissue?
- glucose
- very LDL's (from liver)
- chylomicrons
All stored as TAGs
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What organs drain into the portal venous system
stomach, spleen, small intestine, pancreas, large intestine
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What is jaundice?
lots of bilirubin in the blood (bile reflux into blood). Urine is dark because of conjugate bilirubin excretion.
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What are gall stones?
Cholesterol stones: cholesterol precipitates in gall bladder. Due to chronically high bile acid : lecithin (phospholipid) ratio. Increased risk in women. low bile salts.
Pigment stones: overload of unconjugated bilirubin
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Describe the three types of oral mucosa
1) lining (red) flexible: over loosely fibrous LP, not many dermal papillae. Found: soft palate, inside lips and cheeks, ventral tongue, over alveolar bone (except where it is gingiva)
2) Masticatory (pink) immobile: in contact with food, keratinized or para keratinized, found: gingiva, hard palate
3) Specialized: aterior 2/3 of dorsum of tongue, may be keratinized has papillae.
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Describe the 4 types of lingual papillae:
1) filliform: heavily keratinized, no taste buds, why we brush our teeth.
2) Circuvallate papillae: taste buds flushed by von Ibner's glands, may be keratinized
3) fungiform papillae: not keratinized, taste buds on surface,
4) foliate papillae: no keratinized, taste buds on lateral wall
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Describe the secreting cells in salivary glands
Serous (red, look like pizza slice): secretes watery or albuminous fluid
Mucous (look like adipocyte): secrete mucus
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Discuss the ductal system in the pacreas
- 1) centroacinar cells: beginning of duct
- 2) intercalated duct: secrete sodium and bicarbonate, stimulated by secreting
- 3) intralobular
- 4) interlobular
- 5) pancreatic duct
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Discuss the cells of the liver
-Hepatocytes: 80% of liver vol, many microvilli facing blood plasma (in space of Disse), cell surface of adjacent cells form microscopic channels called bile canaliculi, lots of breakdown (therefore lots of RER)
- -Ito cells: may form part of sinusoid wall, make vit A, make most of liver's CT, can diff into myofibroblasts
- -Kupffer cells: macrophage, also form wall of sinusoid, degrade old RBCs, filter the lumen
-sinusoidal epithelial cells: form a fenestrated epithelium, line the sinusoid, BM forms outer wall of the space of Disse
-pit cells: NK cells,
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Describe the three ways to describe liver lobules
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Describe the basic structure of the GIT
- -Mucosa:
- -3 layers (epithelium, lamina prop (BV's and lymphocytes), muscularis mucosae(gentle agitation));
- -4 types (protective, secreting, absorptive, absorptive/protective)
-Submucosa: strongest layer in gut; Meissner's plexus, glands in esophagus and upper duodenum
-muscularis externa: long and circular muscle, myenteric nerve plexus
-serosa, adventitia:
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What factors affect liver enzyme levels in plasma or serum?
- 1) entry of enzymes into blood (leakage, production)
- 2) efflux of enzymes from damaged cells
- 3) clearance of enzymes
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Describe what liver enzymes you expect to see in hepatocellular disease, biliary tract disease
HC disease: elevated AST, ALT, LD
BT disease: elevated ALK, GGT, 5'NT
Observe relative increase over Upper Limit of Normal (ULN)
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Describe what happens to AST and ALT levels in hepatitis and necrosis of hepatocytes
viral hepatitis (acute): cell damage causes release of cytoplasmic AST and ALT (ALT>=AST)
Necrosis of hepatocytes: release of both cytoplasmic and mitochondrial AST and ALT (AST>ALT)
chronic alcoholism: AST>ALT (>2:1)
Recall that there is lots of AST in the mitochondria, not so much for ALT
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Name some common causes of acute hepatocellular injury
- All three hepatitises
- Alcoholic hepatitis
- toxic injury
- ischemic injury
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List 4 major sources of ALP, how would you determine if elevated ALP was due to a liver problem?
Sources: liver, bone, placenta, ilium
Check and see if GGT or 5'NT are also elevated
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What do bacteria in the gut do?
- -riboflavin, thiamin, B12, K are made
- -fermentation of cellulose
- -recirculation of bile salts
- -prevent growth of harmful bacteria
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List the cells found in a gastric gland (fundus/body)
- -surface and neck mucous cells
- -stem cells
- -Chief cells (pepsinogen and lipase) - apical granules
- -Parietal cells (HCl and intrinsic factor) - proton pumps in tubulovesicles (bigger than chief)
- -enteroendocrine cells: secretes hormones into lamina propria
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Where does the stomach mucous blanket get bicarbonate from?
- surface cells
- fenestrated capillaries that pick it up from the basal side of parietal cells
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Describe the epithelial cells found in the SI
- -enterocyte: absorptive cell, glycocalyx on microvilli
- -goblet cells: mucous
- -enteroendocrine cells: secerete gastrin, somatostatin, CCK, secretin, others
- -paneth cells: at base of cells, innate immune system
- -M cells: antigen-presenting cells
- -stem cells (in crypts): make other cells
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Describe the three regions of the SI
duodenum: brunner's glands, sphincter of Oddi, intestinal glands (=crypts)
Jejunum: long and finger-like with well-developed lacteals
Ilium: Peyer's patches (lymphoid tiss., capped by M cells), shorter villi
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What causes obesity?
- genes
- lifestyle
- abnormal feeding
- childhood overnutrition
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Describe some drug treatments for obesity
- amphetamines: inhibit feeding centres
- Sibutramine: inhibit feeding centres and increase metabolism
- -both of these overexcite the CNS
- Orlistat: lipase inhibitor (you will just poop out lipids)
- Gastric bypass surgery: decrease amount of food being eaten.
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Define the following: Inanition, anorexia, anorexia nervosa, cachexia, bulemia nervosa, ednos
- Inanition: extreme weight loss
- anorexia: diminished appetite
- a. nervosa: abnormal psychic state with aversion to food
- cachexia: abnormally high metabolism
- bulemia nervosa: highly irregular feeding pattern with NO extreme weight loss
- Ednos: extreme preoccupation with weight.
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Describe the 4 lobes of the liver
- Right
- Left
- quadrate (anterior)
- Caudate (posterior)
- 1st 2 separated by the falciform lig
- last 2 on inferior surface of liver
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List the 4 portal-systemic anastomoses
- esophageal
- peri-umbilical
- colic
- rectal
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Describe diverticular disease
out-pouchings of intestinal mucosa
-usually asymptomatic: can rupture causing BRB to be in stool, other minor GI symptoms
-may also become infected like an appendix
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Describe colon cancer
symptoms: abdom. pain, change in stool habits, weight loss, anorexia, fatigue, occult bleeding, BRB, may be palpable
treatment: combination of surgery and medical care
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Why do a digital rectal exam?
- males: prostate, deep lymph nodes,
- females: internal genitalia, pelvic bones, deep LNs
both: rectal tumors, occult blood
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