CH 26 Packet (BIO 181-171) Flashcards
What are the functions of the urinary system
- Excretion (Removal of organic wastes from body fluids)
- Elimination (Discharge of waste products)
- Homeostatic regulation (Of blood plasma volume and solute concentration)
What are the five homeostatic functions of the urinary system
- Regulates blood volume and blood pressure
- Regulates plasma ion concentrations
- Helps stabilize blood pH
- Conserves valuable nutrients
- Assists liver in detoxifying poisons
What is the hilum
- Point of entry for renal artery and renal nerves
* Point of exit for renal vein and ureter
What are the inner and outer portions of the kidney known as?
inner-> renal medulla
outer->renal cortex
What are the renal columns
- Bands of cortical tissue that separate adjacent renal pyramids
- Extend into medulla
- Have distinct granular texture
What is a renal lobe?
- Consists of: Renal pyramid, Overlying area of renal cortex and, Adjacent tissues of renal columns
- site of urine production
What is the renal papilla
• Ducts that discharge urine into the minor calyx (a cup-shaped drain)
Where does urine production begin
nepheines
HOw mich of your total cardiac output do your kidneys receive?
20-25%
Map out a summary of the flow of filtrate during renal circulation
renal artery->segmental artery->interlobar artery-> arcurate artery-> interlobular artery
Describe the sympathetic innervation of the kidneys
- Adjusts rate of urine formation
* Stimulates release of renin
What is the fundamental and functional unit of the kidneys
nephron
What two parts make up the renal corpuscle
- Bowman’s capsule (glomerular capsule)
* Glomerulus
How is blood delivered to and from the glomerulus
- Blood is delivered to the glomerulus via the afferent arteriole
- Blood leaves the glomerulus via the efferent arteriole
Name all of the segments of the renal tubule
- Proximal Convoluted tubule (PCT)
- Loop of Henle (connects the PCT and DCT)(Descending and ascending limb)
- Distal convoluted tubule (DCT)
Describe the characteristics of the proximal convoluted tubule
- Lots of microvilli in epithelial lining, which increases surfaces area for reabsorption
- Functions primarily in reabsorption
- Permeable to water and solutes
Describe the characteristics of the ascending and descending limb of the loop of Henle
- Descending limb(Permeable to water, Not to solutes)
* Ascending limb (Not permeable to water, Contains active transporters for Na+ and Cl-)
Describe the characteristics of the distal convoluted tubule
- Epithelial cells lack microvilli
* Very permeable to solutes and NOT water
What three processes occur in theDCT?
- Active secretion of ions, acids, drugs, and toxins
- Selective reabsorption of sodium and calcium from tubular fluid
- Selective reabsorption of water: (concentrates tubular fluid)
What structure carries filtrate away from the nephron
collecting duct
Describe the characteristic of the collecting system
- Adjusts fluid composition
- Determines final osmotic concentration and volume of urine
- Hormonal regulation
What parts of the nephron are under hormonal regulation
collecting ducts and DCT
What is the juxtaglomerular complex
• Site at which DCT contacts the afferent and efferent arterioles
What is the function of the macula densa cells
• Monitor and respond to changes in osmolarity of the filtrate in the tubule
What is the function of the Juxtaglomerular cells
• Contain baroreceptors that are sensitive to the blood pressure within the arterioles
What are the two types of nephrons based on their location
- Cortical Nephrons
* Juxtamedullary Nephrons
Describe the characteristic of Juxtamedullary Nephrons
- Comprises only 15% of nephrons
* Loop of Henle is long and extends deep into the medulla of the kidney
Describe the characteristics of cortical nephrons
- Comprise 85% of all nephrons
- Located mostly within cortex of kidney
- Loop of Henle is relatively short
What are the three basic processes of urine formation
- Glomerular filtration
- Reabsorption
- Secretion
Define glomerular filtration and where is comes from
movement of filtrate from glomerulus to Bowman’s capsule (from renal corpusule)
Define reabsorption
from tubules to peritubular capillaries (and back into general circulation)
Define secretion
from peritubular capillaries back into the filtrate in the tubules
Define excretion
from tubules out of body
What do the glomerular capillaries do
- Prevent passage of blood cells
* Allow diffusion of solutes, including plasma proteins
The lamina densa allows for the diffusion of what substances
- Small plasma proteins
- Nutrients
- Ions
What are the characteristic of the filtration slits and what do they do
- Are the finest filters
- Have gaps only 6–9 nm wide
- Prevent passage of most small plasma proteins
What is the glmerular hydrostatic pressure do to the filtrate
• Favors filtration and tends to push water and solutes Out of plasma and Into the filtrate
What does the capsular hydrostatic pressure do to the filtrate
• Apposes filtration and pushes water and solutes Out of filtrate and Into plasma
Define net Hydrostatic Pressure
• Is the difference between Glomerular hydrostatic pressure and capsular hydrostatic pressure
What does the Colloid Osmotic Pressure do to the filtrate
- Tends to draw water out of filtrate and into plasma
- Because osmolarity of the blood is higher than in the filtrate
- Opposes filtration
Describe the overall filtration pressure
• Is the average pressure forcing water and dissolved materials Out of glomerular capillaries and Into capsular spaces
Define GFR
- Is the amount of filtrate that the kidneys produce each minute
- Averages 125 mL/min
How much filtrate actually enters the capsular space and how much gets reabsorbed
- However, only 10% of the fluid that is delivered to kidneys leaves bloodstream and enters capsular spaces
- 90% of filtrate is reabsorbed
What factor(s) can alter GFR
• Any factor that alters filtration pressure, alters GFR
An increase in blood pressure or volume will have what type of affect on GFR
- Automatically increases GFR
* Which will promote fluid loss
name three ways in which your body keeps GFR consistent
- Autoregulation (local level)
- Hormonal regulation (initiated by kidneys)
- Autonomic regulation (by sympathetic nervous system)
Describe the auto regulation of GFR
• Maintains GFR despite changes in LOCAL blood pressure and blood flow By changing the diameter of afferent and efferent arterioles
Describe the hormonal regulation of GFR
ANP, BNP, and dilation of afferent arterioles and constriction of efferent arterioles
Describe the autonomic regulation of GFR via the sympathetic nervous system
• Sympathetic activation is triggered by blood loss or extreme stress
– Constricts renal blood vessels
– Decreases kidney function (Blood is shunted to other vital organs)
– Decreases GFR to achieve minimal fluid loss from the blood
What is the normal GFR in a healthy adult
125 ml/min
Define clearance
• The volume of plasma from which a substance is completely removed by the kidney in a given amount of time (usually per minute)
What two substances can be used to measure GFR based on their clearance values?
- Creatinine Clearance Test
* Inulin is a more accurate test for GFR
Describe the characteristics of creatinine and inulin
- Creatinine:Is a natural by-product of muscle metabolism; Freely filtered and NOT reabsorbed; Measuring the concentration of creatinine in the urine gives an estimatation of GFR
- Inulin is a more accurate test for GFR but is NOT naturally made in the body or easily metabolized But when injected into patient, it has a clearance that is equal to GFR (125 ml/min), This is because inulin is freely filtered and is NEITHER reabsorbed NOR secreted
What is the fate of a substance if its clearance value is greater than CFR
• Net secretion has occurred
What is the fate of a substance if its clearance value is less than CFR
• Net reabsorption has occurred
Name three mechanisms that are involved in secretion and reabsorption
- Diffusion
- Osmosis
- Carrier-mediated transport
What is the transport maximum?
- Rate of transport that occurs when carrier proteins are completely saturated
- If certain solute concentrations rise in tubular fluid, the Tm is reached, and ultimately, renal threshold is reached
What is the renal threshold?
• Point at which the solute concentration exceeds the Tm (and can no longer be reabsorbed)
What is the fate of of glucose in a normal, healthy adult
complete reabsorption
Where does filtration take place?
renal corpusle
Where does most of the reabsorption take place
proximal convoluted tubules
Describe the reabsorption and secretion that takes places at the PCT
- Reabsorption in the PCT
- Primarily via active transport
- 60-70% of Na+, K+, Cl-, and HCO3 (bicarbonate) ions
- LOTS of water
- 100% of glucose or amino acids
- Secretion in the PCT
- Organic acids and bases
- H+ ions
Describe the countercurrent multiplication system in the loop of Henle
• Is exchange that occurs between two parallel segments of loop of Henle
What are the benefits of countercurrent multiplication
- Efficiently reabsorbs solutes and water:
* Establishes concentration gradient:
What occurs as the filtrate is traveling down the descending limb to the loop of Henle
- Is permeable to water
- Is relatively impermeable to solutes
- Little or no active transport
- Primarily involved in reabsorption of water
- As a result, osmolarity of fluid increases as it travels to bottom of loop (highest osmolarity at the bottom of loop of Henle)
Describe the secretion and reabsorption that takes place in the ascending limb of the loop of Henle
- Reabsorption in the ascending limb( 2/3 of remaining Na+ and Cl- ions and As a result, the osmolarity of the fluid decreases as the fluid travels up to the DCT)
- Secretion in the ascending limb is minimal (H+ ions)
Describe the secretion and reabsorption that takes place in the DCT
- Reabsorption at the DCT (via active transport) (Na+, Cl-, Ca+,Mg)
- Secretion at the DCT (K+ (through channels),H+ (through pumps))
What hormones regulate the reabsorption of Na and Ca in the DCT
- Aldosterone from adrenal gland (Regulates Na+ reabsorption (so there is minimal Na+ loss in the urine))
- Parathyroid hormone and Calcitriol (Regulate Ca reabsorption)
- (Some regulation of water via ADH)
What hormones regulate solute and water loss in the collecting system
- Aldosterone (Controls sodium ion pumps and regulates Na+ reabsorption)
- ADH (Controls permeability to water (increases water reabsorption))
Describe the reabsorption and secretion that takes place in the collecting ducts
- Reabsorption in the Collecting System (Na+, Bicarbonate ions, Water, Urea)
- Secretion in the Collecting System (Of hydrogen or bicarbonate ions; Secretion functions in controlling body fluid pH)
Describe the normal responses of the collecting system to changes in body fluid pH
- > Low blood pH (Peritubular Fluid) = Acidosis; Carrier proteins; Pump H+ into tubular fluid (renal tubule);Reabsorb bicarbonate ions (back into blood)
- > High blood pH (Peritubular Fluid) = Alkolosis; Collecting system; Secretes bicarbonate ions into renal tubules; Pumps H+ into peritubular fluid
Differentiate between obligatory and Facultative water reabsorption, and state where they occur
—>Obligatory Water Reabsorption
• Is water movement that cannot be prevented
• Usually recovers 85% of filtrate produced
• Primarily in the PCT
—>Facultative Water Reabsorption
• Controls volume of water reabsorbed along DCT and collecting system (because they are hormonally regulated)
• 15% of filtrate volume (27 liters/day)
• Segments are relatively impermeable to water
• Except in presence of ADH
What structure carries reabsorbed substances back into the general circulation
vasa recta
Where in the nephron does the filtrate reach its highest osmolarity?
bottom of loop of Henle
Describe the filtrate in the presence and the absence of ADH
Presence: small volume and ??
Absence: large volume and dilute urine
What structures make up the urinary tract
ureters, urinary bladder, urethra
How often do peristaltic contractions occur in the ureters
every 30 seconds
What is the function of the urinary bladder
temporary reservoir for urine storage
The muscularis layer of the bladder contains an important muscle. name the muscle and give its function
- The Muscularis Layer consists of the detrusor muscle of the bladder
- Contraction of this muscle compresses the bladder and expels urine
Describe the characteristics of the internal urethral sphincter
- Made of smooth muscle
- Located in the neck of the urinary bladder
- Involuntary control
Describe the characteristics of the external urethral sphincter
- Is a circular band of skeletal muscle that acts as a valve
- Is under voluntary control
- Voluntarily relaxation of this sphincter permits micturition
Describe the chain of events that occur during the micturition reflex and urination
stretch receptos signal to sacral spinal cord and efferent fibers stimulate ganglionic neurons in wall of bladder. Post ganglionic neuron stimulates detrusor muscle contraction
What gives your the awareness that you have to urinate
projection of information from the thalamus to the cortex
