Digestive & Renal Flashcards
compare & contrast cortical nephrons from juxtamedullary nephrons:
cortical nephron:
- 85% of all nephrons
- lie mostly in cortical cap of renal lobes
- short nephron loop
- efferent arteriole supplies peritubular capillaries (porous & low pressure)
- intertwine w the renal tube
- needed for tubular reabsorption & secretion
juxtamedullary nephron:
- 15%
- glomerulus is closer to corticomedullary junction
- long nephron loop
- efferent arteriole supplies vasa recta that run parallel to nephron loops
- needed to produce concentrated urine
both:
- have glomerular capillaries
- very permeable
- afferent arteriole feeds into capillaries
- efferent arteriole drains from the capillaries
- keeps blood in the glomerulus under high pressure; needed for filtration
vasa recta
- special capillary networks that supply blood to the medulla
- found on juxtamedullary nephron loop of henle
ADH function, target in nephron, & outcome:
- ADH = antidiuretic hormone; regulates final reabsorption of water
- targets the collecting ducts = makes them more permeable to water
- increases water reabsorption = lowers plasma osmolarity to normal
loop of henle function:
- reabsorb water (ascending loop) & NaCl (descending loop) from filtrate = conserves water = produces concentrated urine
- juxtamedullary nephron loop of Henle goes deeper into the medulla
path of urine flow:
- nephrons (cortex)
- pyramids (medulla)
- papillae
- minor calyces
- major calyces
- renal pelvis
- ureter
- bladder
- urethra
net filtration pressure (NFP):
- directly proportional to glomerular filtration rate (GFR = how fast filtrate forms)
- calculation: NFP = outward pressure - inward pressures
(HPgc) - (HPcs+OPgc)
Brunner’s Glands:
- located in duodenum submucosa
- secrete an alkaline mucin that coats the intestineal walls to protect them from acid chyme
Agentaffin cells:
- located in mucosa of small intestine
- secrete serotonin into lamina propria = stimulates intestinal peristalsis
lactose intolerance:
- lactase enzyme is defective or missing in people who are lactose-intolerant
- 3 types of lactose intolerance:
1. primary (most common) = developed after babies weened from milk
2. secondary = developed after illness, injury or surgery involving small intestine
3. congenital = (rare) babies are born lacking the enzyme lactase - Tx = taking lactase tablets/droplets
alimentary canal & layers:
- alimentary canal = aka digestive tract; long tube of organs that make a pathway for food to travel through the body
- layers (from innermost to outermost):
1. mucosa (stratified squamous epithelium)
2. submucosa = esophagus = has esophageal glands that secrete mucus to lubricate the bolus of food; small intestine = has major blood vessels/lymphatic vessels & lymph nodes
3. muscularis externa (longitudinal muscle & circular muscle) = carry out peristalsis
4. serosa (epithelium & CT) adventitia in the esophagus
what hormone stimulates peristalsis in the small intestine?:
- serotonin
- serotonin is secreted by agentaffin cells from the mucosa layer
intraperitoneal vs retroperitoneal:
- intraperitoneal organs have a mesentary holding them together = stomach, small intestine, transverse colon, liver, gallbladder
- retroperitoneal organs = kidneys, adrenal glands, pancreas, nerve roots, lymph nodes, abdominal aorta & inferior vena cava
order in which feces would pass through the large intestine:
- cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
- rectum
stratified squamous epithelium location & purpose:
- found in: mouth, oropharynx, laryngopharynx, esophagus, & anal canal
- protection from friction
simple columnar epithelium location & purpose:
- found in: stomach, small intestine & large intestine
- secretion, excretion, & absorption
bile:
- synthesized in the liver
- stored in the gallbladder
- enters from the gallbladder into the duodenum == digestion of fats (bile salts mix with fat globules in the lumen of small intestine)
order of swallowing (deglutition) reflex:
- upper esophageal sphincter is contracted, tongue forces bolus into oropharynx
- uvula ascends & epiglottis bends down to keep food out of airways; upper esophageal sphincter relaxes to allow food to enter the esophagus
- pharyngeal constrictor muscles contract, forcing food into esophagus inferiorly
- food bolus is propelled down the esophagus by peristalsis
- gastroesophageal sphincter opens; food enters the stomach & becomes chyme
teniae coli:
- within the muscularis layer
- three bands of longitudinal smooth muscle
- muscle tone of teniae coli draws colon up in haustra
= contraction of circular muscle
carbohydrate digestion:
- salivary amylase
- CHO digestion stops in stomach due to acid denaturing amylase
- CHO digestion resumes in lumen of small intestine
- pancreatic amylase secreted into duodenum
- brush border enzymes = disaccharides: lactase, maltase, sucrase
gomphosis:
- joint between tooth & bone (anchors root of tooth into its bony socket within the maxillary bone (upper jaw) or mandible bone (lower jaw)
frenulum:
- labial frenula = anchors lips to the gingivae
- lingual frenulum = median fold that anchors the tongue to the floor of the oral cavity
uvula:
- most posterior aspect of palate
- helps to retain food in the mouth until ready to swallow
rugae location & purpose:
- rugae = ridges
- palatine rugae = aid the tongue in holding & manipulating food
- stomach rugae = longitudinal folds in mucosa & submucosa = help stomach collapse/expand like an accordion
solvent drag:
- solutes that are transported back from the renal tubule by the flow of water
- occurs in proximal convoluted tubule
- removes undesirable substances that have been passively reabsorbed (ex = uria & uric acid)
splanchnic circulation:
- consists of blood supply to GI tract, liver, spleen, & pancreas
(review image)
parasympathetic fibers:
- facial nerves & glossopharyngeal nerves = innervate salivary glands
- vagus nerves = innervate liver, gallbladder, stomach, pancreas & proximal half of large intestine
- sacral spinal nerves = innervate distal half of large intestine
sympathetic fibers:
- thoracolumbar division
- activate during emergency/exercise = inhibits digestion, salivation, & peristalsis
amylases:
- digestive enzymes for carbohydrates
- breaks carbs down into monosaccharides = glucose, fructose, galactose
small intestine:
- regions in order: duodenum, jejunum, ileum
- HCO3- (bicarbonate) is secreted by the pancreas into the duodenum to neutralize acidic chyme
- brush border of small intestine = secretes proteases for protein digestion
- bile & pancreatic lipase: secreted into lumen of duodenum = form micelles (transport lipids to brush border) = lipid digestion = micelles form chylomicrons
- chylomicrons are too large to enter capillaries so they are absorbed into == lacteals (lymph system filters fats!)
stomach cell types:
- gastric pits on top of surface (columnar) epithelium
- parietal cells = secrete HCl, intrinsic factor, & ghrelin (appetite-regulating hormone)
- G cells = secrete gastrin to stimulate secretion of HCl
- enteroendocrine cells = secrete hormones that regulate digestion
- foveolar (mucous neck) cells = secrete mucus to protect stomach lining
- chief cells = secrete enzymes: gastric lipase, leptin & pepsinogen
4 regions of the stomach:
- cardia = surrounds opening where esophagus enters
- fundus = dome-shaped region beneath diaphragm muscle
- corpus (body) = large mid-portion
- pylorus = slightly narrower pouch in inferior aspect
structures that increase absorption:
- microvilli (brush border) contain villi
- villi = absorptive cells (simple columnar) mixed with goblet cells
- fat globules = emulsified by bile salts in duodenum; bile salts coat fat droplets = increases surface area for pancreatic lipase to act
- muscularis mucosae = thin layer of smooth muscle wrinkles the mucosa to increase surface area
Glomerular filtration rate (GFR):
- volume of filtrate formed each minute
- high GFR = too little time for reabsorption; water & valuable solutes (glucose & Na+) are lost in the urine
- low GFR = too much time for reabsorption; unwanted wastes (urea) are returned to blood
Distal convoluted tubule (DCT):
- along w collecting duct (CD) = two final segments of kidney nephron
- receives urine from glomerulus
- in DCT = water & salts are secreted
compare glomerular capillaries with systemic capillaries:
glomerular:
- have arterioles @ each end
- can vasodilate or vasoconstrict
- give precise control of blood flow through capillaries
- extremely permeable fenestrated capillaries
- function = filter water & solutes from blood into glomerular capsule
systemic:
- arteriole @ one end; venule (lacking smooth muscle) @ other end
- continuous capillaries (only slightly permeable to water & solutes)
- function = deliver O2 & nutrients from blood to tissue cells; pick up CO2 & wastes
loop of henle function:
- part of the nephron
- function = reabsorb water & NaCl from filtrate of kidney tubules === concentrated urine
location of ions that are filtered by the kidney:
- occurs in the proximal tubule
- Na+ = pumped out of tubule by Na+/K+ pump = Na+ enters peritubular capillaries = low Na+ inside tubule cell
- Na+ in filtrate enters via transport protein
- 100% of glucose & amino acids are cotransported with Na+
- water is reabsorbed through aquaporins by osmosis (follows other solutes = obigatory)
- urea = lipid soluble waste product follows water by solvent drag (goes directly through membrane)
- Cl- & K+ & other ions are passively reabsorbed down their gradients (paracellular route = through the tight junctions)
diabetes mellitus relation to kidneys:
- high blood sugar = carriers reach a transport maximum = cannot absorb all the glucose
- results in: glucosuira (glucose lost in urine), polyuria (water is lost in urine as it follows glucose) === dehydration & extreme thirst
Podocytes:
- “foot-cells” = wrap around glomerular capillaries
- put down foot processes to form filtration slits
normal vs abnormal constituents of urine:
- normal = water, urea, sodium, potassium, phosphate, sulfate ions
- abnormal = glucose, amino acids, fatty acids, leukocytes, erythrocytes, proteins, ketone bodies
hepatic (portal) triad:
actually a quintad
1. bile ducts
2. proper hepatic artery
3. hepatic portal vein
4. lymphatic vessels
5. branch of vagus nerve
nephron processes in order:
- glomerular filtration = dumps a protein-free cell-free filtrate into waste container (renal tubule); happens @ renal corpuscle == everything except blood cells & large proteins are filtered from glomerular capillaries into glomerular capsule
- tubular reabsorption = selectively reclaims what the body needs; happens @ renal tubule == filtered substances move from filtrate into peritubular capillaries (anything not absorbed becomes urine)
- tubular secretion = selectively adds back to waste container what the body does not need; happens along renal tubule & collecting duct; second chance to remove substances from the blood
afferent arterioles role in vasoconstriction/vasodilation:
- part of myogenic mechanism = negative feedback
- vascular smooth muscle in afferent arterioles responds to moderate changes in systemic blood pressure (due to posture, exercise, etc.)
- when stimulus increases systemic BP = stretch on afferent arteriole == response: afferent arteriole vasoconstricts
- when stimulus decreases systemic BP = relax on afferent arteriole == response: afferent arteriole vasodilates
