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Chapter 26
The Urinary System
28
Anatomy
Undergraduate 2
02/22/2018

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Term
Excretion
Definition
Removal of organic wastes from body fluids
Term
Elimination
Definition
Discharge of waste products
Term
3 functions of the urinary system
Definition
1. Excretion
2. Elimination
3. Homeostatic regulation
Term
5 homeostatic functions of the urinary system
Definition
1. Regulates blood volume and blood pressure
-adjusts volume of water lost in urine
-Releases erythropoietin and renin
2. Regulates plasma ion concentrations
-Sodium, potassium, & chloride ions (controls quantities lost in urine)
-Calcium ion levels (through synthesis of calcitriol)
3. Helps stabilize blood pH
-Controls loss of hydrogen ions & bicarbonate ions in urine
4. Conserves valuable nutrients
-Prevents excretion while excreting organic waste products
5. Assists liver in detoxifying poisons
Term
Goal of urine production-
Definition
maintain homeostasis by regulating volume and composition of blood
Term
Nephrons
Definition
Microscopic, tubular structures in cortex of each renal lobe
Where urine production begins
Term
Glomerulus
Definition
Consists of 50 intertwining capillaries
Blood delivered via afferent arteriole
Blood leaves in efferent arteriole
Flows into peritubular capillaries
Which drain into small venules
And return blood to venous system
Term
Filtration
Definition
Occurs in renal corpuscle
-Driven by blood pressure
-Forces water and dissolved solutes out of glomerular capillaries into capsular space
-Produces protein free solution (filtrate) similar to blood plasma
Term
Three Functions of Renal Tubule
Definition
1. Reabsorb useful organic nutrients that enter filtrate
2. Reabsorb more than 90% of water in filtrate
3. Secrete waste products that failed to enter renal corpuscle through filtration at glomerulus
Term
Proximal convoluted tubule function
Definition
reabsorb ions, vitamins, water, organic molecules
Term
Loop of Henle function
Definition
reabsorb water (down), reabsorb ions (up)
Term
Distal convoluted tubule
Definition
reabsorb Na+ & Ca2+; secrete toxins, ammonia, drugs
Term
Collecting ducts
Definition
Receive fluid from many nephrons
Each collecting duct
Begins in cortex
Descends into medulla
Carries fluid to papillary duct that drains into a minor calyx
Term
Cortical nephrons
Definition
85% of all nephrons
Located mostly within superficial cortex of kidney
Loop of Henle relatively short
Efferent arteriole delivers blood to a network of peritubular capillaries
Term
Juxtamedullary nephrons
Definition
15% of nephrons
Nephron loops extend deep into medulla
Peritubular capillaries connect to vasa recta
Vasa recta- capillaries wrap around Loop of Henle
Term
3 processes in the DCT
Definition
1. The active secretion of ions, acids, drugs, and toxins into the tubule
2. The selective reabsorption of sodium ions and calcium ions from tubular fluid
3. The selective reabsorption of water
Term
3 organic wastes
Definition
1. Urea-the most abundant waste
2. Creatinine-generated through the breakdown of creatine phosphate
3. Uric acid-formed during the recycling of the nitrogenous bases from RNA molecules.
Term
Secretion
Definition
The transport of solutes from the peritubular fluid, across the tubular epithelium, and into the tubular fluid
Term
Characteristics of Carrier-mediated transport
Definition
1. A specific substrate binds to a carrier protein that facilitates movement across the membrane.
2. A given carrier protein typically works in one direction only.
3. The distribution of carrier proteins can vary among portions of the cell surface.
4. The membrane of a single tubular cell contains many types of carrier proteins.
5. Carrier proteins, like enzymes, can be saturated.
Term
Facilitated diffusion
Definition
A carrier protein transports a molecule across the plasma membrane without expending energy..
-Always follows the concentration gradient for the ion or molecule transported.
Term
Active transport
Definition
Driven by the hydrolysis of ATP to ADP
Can operate despite an opposing concentration gradient.
Term
Cotransport
Definition
-not directly linked to the hydrolysis of ATP
-2 substrates cross the membrane while bound to the carrier protein
-always follows the concentration gradient of at least one of the transported substances.
Term
Countertransport
Definition
-resembles cotransport except the 2 transported ions move in opposite directions
Term
renal threshold
Definition
the plasma concentration at which a specific substance or ion begins to appear in the urine
Term
Glomerular filtration rate
Definition
The amount of filtrate the kidneys produce each minute.
Term
3 levels of control to stabilize the
GFR
Definition
1. Autoregulation at the local level
2. Hormonal regulation-initiated by the kidneys
3. Autonomic regulation-by the sympathetic division of the ANS
Term
3 triggers for the release of renin by the juxtaglomerular complex (JGC)
Definition
1. A decrease in blood pressure
2. stimulation by sympathetic innervation
3. a decrease in the osmotic concentration of the tubular fluid at the macula densa
Term
5 functions of the PCT
Definition
1. Reabsorption of organic nutrients
2. Active reabsorption of ions
3. Reabsorption of water
4. Passive reabsorption of ions
5. Secretion
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