Final: Salt and Water Balance and Nitrogen Excretion Slides Flashcards
Osmolarity of a solution
Moles of osmotically active particles per liter of solvent
What macromolecules do nitrogenous wastes come from?
Proteins and nucleic acids
What are the nitrogenous wastes? (3)
Urea, ammonia, uric acid
What are ureotelic, ammonotelic, and uricotelic animals?
- Ureotelic: mostly produce urea (humans, mammals)
- Ammonotelic: mostly produce ammonia (fish)
- Uricotelic: mostly produce uric acid (reptiles)
Functions of the renal system (6)
- Regulates water concentration
- Regulates ion concentration
- Excretes metabolic wastes: urea, uric acid, creatinine
- Removes foreign molecules
- Gluconeogenesis
- Releases hormones
Composition of blood dictates and reflects composition of _____ ____
interstitial fluid (want to maintain isosmolarity)
Parts of the renal system (4)
Kidneys, ureters, bladder, urethra
Main function of kidneys
Maintain homeostasis in blood by getting rid of waste products or anything in excess
Function of bladder
Storage of urine for later excretion
Function of ureters
Long, muscular tubes connecting kidney and bladder
Structure of kidneys
Tiny microscopic tubes called nephrons, the functional unit of the kidney
Classifications of nephrons
Cortical or juxtamedullary
Parts of nephrons (6)
- Glomerular capsule
- Proximal convoluted tube
- Descending loop of Henle
- Ascending loop of Henle
- Distal convoluted tubule
- Collecting duct
What happens at the collecting duct of nephrons?
Nephrons empty their contents
When does the fluid in nephrons become urine, and what is it before then?
Becomes urine when it reaches collecting duct, called filtrate until then
What are nephrons surrounded by?
Many capillaries, as their job is to maintain homeostasis
Characteristics of glomerular capsule
Highly permeability so lots of substances can move into nephron (beginning of nephron)
What is in the glomerulus?
Capillaries
What is the renal corpuscle?
Initial blood-filtering component of nephron (many openings to increase permeability)
What are the openings in the renal corpuscle called?
Filtration slits in glomerular capsule, fenestration in glomerulus/capillaries
Path of filtrate in renal corpuscle (3)
- When blood is in glomerulus, filtrate passes through pores in between endothelial cells
- Filtrate goes through basement membrane leading to glomerular capsule
- Passes through filtration slits in between podocytes
Interactions between capillaries and nephron (4)
Filtration, reabsorption, secretion, excretion
What is reabsorption in the kidneys?
Substance needs to cross multiple membranes to reach blood: gets “mistakenly” absorbed by nephrons and needs to get back to blood
Steps in reabsorption in the kidneys
- Move from nephron lumen to apical side of nephron epithelial cells
- Move to basal side of nephron epithelial cells
- Cross basement membrane to reach interstitial fluid
- Cross endothelial cells to reach lumen of capillaries
What substances are filtered into the lumen of the nephron? (9)
Na+, Cl-, K+, HCO3-, H+, glucose, amino acids, urea, water
Where does sodium reabsorption occur? (3). Give percentages.
- 67% at proximal convoluted tubule
- 25% in loop of Henle
- 8% in distal convoluted tubule and collecting duct
Function of sodium reabsorbed at proximal convoluted tubule
Drives reabsorption of glucose, amino acids, water, and chloride ions through secondary active transport
Function of sodium reabsorbed at loop of Henle
Drives reabsorption of water and sodium chloride
Function of sodium reabsorbed at distal convoluted tubule and collecting duct
Subject to hormonal control to help secrete more potassium and hydrogen ions
Substances filtered/secreted at proximal convoluted tube (2)
H+ and NH3
Substances reabsorbed at proximal convoluted tube (6)
HCO3-, NaCl, H2O, amino acids, glucose, K+
Substances filtered/secreted at distal convoluted tube (2)
H+, K+
Substances reabsorbed at distal convoluted tube (3)
NaCl, H2O, HCO3-
Characteristics of descending loop of Henle (2)
- Highly permeable to water (water reabsorbed)
- does not absorb NaCl
Characteristics of ascending loop of Henle (2)
- Active reabsorption of NaCl
- Impermeable to water
What is reabsorbed at the collecting duct?
NaCl, urea, H2O
What is very highly concentrated urine?
Lots of waste, minimal water
What two substances help maintain osmolarity in nephrons?
Na+ and water (where Na+ goes, water follows)
In nephrons, what happens when more Na+ is absorbed?
More K+ is secreted/released
What hormone controls sodium reabsorption?
Aldosterone
Characteristics of aldosterone (4)
- Released from adrenal cortex
- Increases blood pressure
- Acts on distal convoluted tubule and collecting duct
- Increases amount of sodium channels on membrane
What controls water balance (give region of brain, gland and hormone)?
Antidiuretic hormone (ADH), or vasopressin, released from posterior pituitary (controlled by hypothalamus)
How do we obtain water? (3)
Ingested in food, ingested in liquid, derived from metabolism (cellular respiration)
How do we lose water? (3)
Urine (major regulation), feces, evaporation (sweating)
Mechanism of ADH action in kidney
ADH released in blood (peptide hormone), binds to extracellular receptors on collecting duct - G protein pathway to activate protein kinase A - causes increase in aquaporins - increases water reabsorption (losing less water)
When would ADH be released in the body?
When the water level in the body is low (ADH increases plasma water level)
What should happen to urine water volume when plasma water level is low?
Should decrease (don’t want to lose more water)
What should happen (regarding kidneys/urine) when you want to retain more water?
Low urine water level, which increases plasma water level
What happens to plasma water level when urine water volume increases?
Plasma water level decreases
