RAT 16 Flashcards
if a waste molecule is in the peritubular capillary lumen, which structures must it pass through in order to move into the tubule lumen? what is this process called?
- from filtrate in the lumen of the tubule, across/between the tubule cells, into the endothelial cells of the peritubular capillaries to re-renter the blood
- tubular reabsorption
what is the paracellular route?
substances pass between adjacent tubule cells; tight junctions
what is the transcellular route?
- substances must move through the tubule cells
- glucose and amino acids
- first crosses apical membrane to the cytosol and exits through basolateral membrane
what is the apical side of the tubule cell?
membrane facing the tubule lumen
what is the basolateral side of the tubule cell?
side of the membrane facing the interstitial fluid
define facilitated diffusion
carrier protein passively transports a solute with its concentration gradient, no ATP
define primary active transport
carrier protein “pump” directly uses ATP to move a solute against its concentration gradient
define secondary active transport
concentration gradient set up by a primary active transport pump is used to drive the transport of a second solute against its concentration gradient
define antiport pumps (antiporter)
move two or more solutes in the opposite directions
define symport pumps (symporter)
move two or more solutes in the same direction
define transport maximum
where all carrier protein sites are full
define saturation
when a carrier protein has all its protein sites full
what cellular feature is found on the apical surface of the cells lining the proximal tubule? how does this aid in the fucntion of these cells?
- sodium leak channels
- allows for a slower more gradual diffusion of ions to control gradients
how active are the cells in the PT? what are the primary roles of these cells?
- very active! most metabolically active part
- reabsorption of a large percentage of electrolytes, reabsorption of 100% of nutrients, reabsorption of many bicarbonate ions, reabsorption of 65% of water
what substances are reabsorbed in the PT?
- electrolytes, nutrients, bicarbonate ions, water
- sodium, calcium, potassium, phosphate, glucose, amino acids
why is sodium ion reabsorption so important?
key to reabsorbing many other substances in the PT
what are the carriers/pumps in sodium ion reabsorption?
- carrier proteins specific for sodium ions
- sodium ion symporter
- sodium/hydrogen ion antiporter
what are the carriers/pumps in the reabsorption of organic solutes?
- sodium/glucose symporters
- faciltiated diffusion
what other substances are transported in a similar fashion? (reabsorption of organic solutes)
chloride ions
what are the carriers/pumps in the reabsorption of chloride ions?
- paracellular route
- faciltiated diffusion
what is the name of the enzyme that catalyzes the bicarbonate reabsorption reaction?
carbonic anhydrase
what creates the gradient that drives the passive reabsorption of water?
accumulation of solutes in the cytosol and interstitial fluid
what is obligatory water reabsorption?
water reabsorption in the kidneys that occurs without the regulation of hormones and irrespective of the medullary concentration gradient
what is an aquaporin?
a type of water channel in the plasma membrane that greatly enhances rapid water reabsorption
what substances are secreted in the PT?
- nitrogenous waste products and drugs
- uric acid
- ammonium ions
- creatine
- small amounts of urea
- penicillin and morphine
describe the permeability of the descending limb of the nephron loop to water and solutes. how does this impact the osmolarity of the filtrate?
- freely permeable to water but much less permeable to solutes ( like sodium and chloride ions)
- water can move out by osmosis but few solutes follow, causing osmolarity to increase as it passes down the descending limb
describe the permeability of the ascending limb of the nephron loop to water and solutes. how does this impact the osmolarity of the filtrate?
- impermeable to water but, transport NaCl with sodium/potassium/chloride symporters
- filter loses solutes gradually and becomes less concentrated as ions are pumped unto the interstitial fluid
what is reabsorbed in the nephron loop?
- water
- sodium ions
about how much sodium and water has already been reabsorbed before reaching the DT?
- 85% of water
- 90% of sodium ions
what is the major difference in the histology of the cells in the DT composed to the PT?
cells of the DT lack microvilli
why is reabsorption in the DT important?
if we excreted the remaining water and sodium in urine, we would lose 29 liters of water, which is incompatible with life
what is facultative water reabsorption
water reabsorption that is controlled by hormones to maintain a constant extracellular fluid osmolarity
describe the three hormones involved in facultative water reabsorption.
- aldosterone (increase permeability to sodium ions)
- antidiuretic hormone (diuresis)
- atrial natriuretic peptide (triggers natriuresis)
what are the major modifications to filtrate that occur in the collecting ducts and papillary ducts?
- impermeable to water in the absence of ADH
- permeable to urea
- continue to reabsorb ion (sodium, calcium, bicarbonate) from the filtrate
explain how the lining of the digestive tract is considered an external body surface
because it is open to the outside of both ends
what is the endocrine fucntion of the pancreas?
insulin and glucagon released from pancreatic islets into the blood and affect most cells in the body
what is the exocrine function of the pancreas?
enzymes secreted primarily by clusters of acinar cells - they help with digestion
where is the pancreas located and what are the regions of the pancreas?
- left upper quadrant of the abdomen extends from the duodenum to the spleen
- head, body, tail
what is an acinus?
clusters of acinar cells
what is found in pancreatic juice?
- water
- multiple digestive enzymes
- other proteins
- bicarbonate ions
what are the two ducts that deliver pancreatic juice to the duodenum?
- main pancreatic duct
- accessory pancreatic duct
name two hormones that stimulate pancreatic secretion
- cholecystokinin (CCK)
- secretin
describe the shape and location of the liver
- pyramid shaped
- located in the right upper quadrant against the inferior surface of the diaphragm
describe the shape and location of the gallbladder
- small sac
- located on the liver’s posterior side
name the four lobes of the liver
- right lobe
- left lobe
- caudate lobe
- quadrate lobe
what separates the left and right lobes?
falciform ligament
what does the hepatic artery carry?
oxygen-rich blood to the liver
what does the hepatic portal vein carry?
nutrient-rich, deoxygenated blood to the liver
what does the hepatic vein carry?
drains blood from the sinusoids
what is the basic unit of the liver?
liver lobule
what cells compose the liver lobule?
hepatocytes
what is found in the center of the liver lobule?
central vein
what is found at each corner of a lobule?
portal triad
what three structures compose the portal triad
- hepatic arteriole
- portal venule
- bile duct
what is the main digestive function of the liver?
produce bile
what are the two primary functions of bile?
- required for digestion and absorption of lipids
- it is the mechanism by which the liver excretes wastes and other substances that they kidney cannot excrete
what are some other functions of the liver?
- nutrient metabolism
- detoxification
- excretion
what is the primary function of the gallbladder?
stores bile, concentrates it, and release it when stimulated
what hormone triggers the release of bile?
CCK
what is the source of CCK?
cells in the lining of the duodenum
which duct is connected to the gallbladder?
cystic duct
which sphincter controls release of bile into the duodenum?
hepatopancreatic sphincter
do we really need to “detox”? why or why not?
no because of our liver, which convert harmful chemical (toxins) into nonharmful substances that can be excreted in bile or urine
what hormone leads to the release of bile?
CCK
what is the source of CCK?
duodenum cells
what is the stimulus for the release of CCK?
fats, digestive proteins
what is another important stimulus that leads to the release of bile? how is this a positive feedback loop?
- bile salts
- bile salts re0renter the liver, bile secretion increases dramatically, bile secretion continues until the duodenum empties
