Chapter 14 Urinary system Flashcards
Large, bean shaped organs in the abdominal cavity that function to remove wastes and excess solutes from the ECF in the form of urine.
Kidney
What are the 10 main functions of the kidneys?
1) maintaining H2O balance in the body
2) Maintaining proper osmolarity of body fluids
3) Regulating concentration of ECF ions: Na+, Cl−, K+, Ca2+, H+, HCO3−, PO43−, SO42−, Mg2+
4) Maintaining proper plasma volume—important for blood pressure
5) Maintaining proper acid-base balance of the body—by adjusting urinary output of H+ and HCO3−
6) Eliminating the wastes of metabolism—including urea (from proteins), uric acid (from nucleic acids), creatinine (from muscle creatine), bilirubin (from hemoglobin), and hormone metabolites
7) Excreting foreign compounds—drugs, food additives, pesticides, etc.
8) Producing renin—hormone that triggers salt conservation
9) Producing erythropoietin—hormone that stimulates red blood cell production
10) Converting vitamin D into its active form
Pathway of urine
renal pelvis -> ureter -> urinary bladder -> urethra
Is the blood flow to the kidneys just enough to oxygenate the kidneys, or more?
20-25% of cardiac output flows through the kidneys
The smallest unit of the kidney that performs all of the kidney’s function
Nephron
5 parts of a nephron
Glomerulus, Afferent arteriole, Efferent Arteriole, Peritubular capillaries, Bowman’s capsule
What are the 2 types of nephrons? (based on length of loop of henle)
-Cortical nephron (80% of nephrons) short loop
-Juxtomedullary nephron (20% of nephrons) long loop
What are the two regions of the kidney?
Renal cortex and renal medulla
ball like tuft of capillaries where some water and solutes are filtered from blood passing through
Glomerulus
blood vessel entering glomerulus
afferent arteriole
blood vessel exiting the glomerulus
efferent arteriole
supply renal tissue and aid in reabsorption and secretion to form urine
peritubular capillaries
hollow tube surrounding glomerulus (filtered plasma flows into)
Bowmans capsule
filtering of plasma thru the glomerulus
Glomerular filtration
What the three basic renal processes?
Glomerular filtration, Tubular reabsorption, and Tubular secretion
reabsorption of substances of value from the filtrate in the tubules back into the blood vessels
Tubular reabsorption
selective transfer of substances from the peritubular capillary blood into the tubule
Tubular secretion
What are the three layers of the glomerular membrane?
Glomerular capillary wall, Basement membrane, and Inner layer of Bowman’s capsule
What does the glomerular capillary wall do?
It’s a layer of endothelial cells, however they have large pores between and in the middle of the cells. They are very permeable to H2O and solutes
What is the basement membrane?
-It is acellular, and helps block large plasma proteins from getting into the glomerular capillary wall.
-They are negatively charged and repel small plasma proteins that are also negatively charged
What is the inner layer of Bowmans capsule?
They consist of podocytes that give off interdigitating foot process, which form filtration slits that filtrate can pass through
What forces cause plasma to leave the glomerular capillaries and enter Bowman’s capsule?
Glomerular capillary pressure, plasma-colloid osmotic pressure, and Bowmans capsule hydrostatic pressure
glomerular capillary pressure
- blood pressure within the glomerular capillaries (pushing in)
plasma colloid pressure
- plasma proteins stuck in glomerular capillaries displacing water (pushing out)
Bowman’s capsule hydrostatic pressure
- pressure exerted by the fluid in Bowman’s capsule (pushing out)
Why is glomerular pressure typically higher than in systemic capillaries?
afferent arteriole has little vascular resistance and the glomerulus is specialized for filtration
What is the glomerular filtration rate (GFR) and what factors does it depend on?
GFR is the volume entering Bowman’s capsule per min
depends on filtration coefficient (Kf) and net filtration pressure
How does arterial blood pressure affect glomerular capillary pressure?
increased arterial blood pressure increases the glomerular capillary pressure
How does arterial blood pressure affect plasma-colloid osmotic pressure?
does not have any effect on plasma colloid pressure
How does arterial blood pressure affect the GFR?
increased pressure causes more fluid to be lost to urine
What are the two intrinsic mechanisms used by the kidneys to counteract changes in GFR?
Myogenic mechanism and Tubuloglomerular feedback
stretch of afferent arteriolar smooth muscle (bc increased blood pressure) causes automatic contraction
myogenic mechanism
tubular cells in the macula densa (of the juxtaglomerular apparatus) sense the increase/decrease salt concentration and release cytokines that activate granular smooth muscle to dilate around afferent arteriole
Tubuloglomerular feedback
How can GFR be controlled extrinsically?
sympathetic nervous system
cells that contain actin that hold the glomerular capillary bundle together
mesangial cells
How are mesangial cells affected by sympathetic activity?
sympathetic causes them to contract, which closes off some capillaries/decreases filtration surface area
all steps in transepithelial transport of the solute are passive—no energy spent to move substance down gradient
Passive reabsorption
one or more steps of transepithelial transport require energy to be used to move solute against gradient
Active reabsorption
What is transepithelial transport?
-steps the filtrate must pass through:
1) Luminal membrane
2) cytosol of tubular cell
3) Basolateral membrane
4) interstitial fluid
5) peritubular capillary wall
plasma membrane of tubular epithelial cell facing lumen
Luminal membrane
plasma membrane of tubular epithelial cell facing interstitial fluid
Basolateral membrane
If you saw a diagram of the mechanisms of Na+ reabsorption, could you explain what was going on?
1) Na+/K+ pump in basolateral membrane dumps Na+ from tubular cell into interstitial fluid of kidney
2) Na+ leak channels or passive carriers in luminal membrane allows Na+ to pass from tubule lumen into tubular cell
total amount of Na+ in the body (not the same as concentration)
Na+ load
How does the Na+ load affect blood pressure?
affects BP because greater salt load increases osmotic gradient (water retention, increased ECF and blood plasma volume) which increases BP
How is Na+ reabsorption regulated?
aldosterone (RAAS)
When is renin released? Where is it released from?
-in response toe reduced salt/ECF volume/BP
-from the granular cells of juxtaglomerular apparatus
Where does angiotensin come from?
liver
promotes insertion of additional Na+ leak channels into luminal membrane and Na+/K+ pumps into basolateral membrane
Aldosterone
Where does aldosterone come from?
from the adrenal glands
hormone produced in atrial cardiac muscle cells
Atrial natriuretic peptide (ANP)
hormone produced in ventricular cardiac muscle cells (also found in brain)
Brain natriuretic peptide (BNP)
What happens when there is an increased NaCl and H2O retention?
-increased bp
-increased blood plasma
-additional stretching of cardiac muscle during filling
-release of ANP and BNP from stretched cardiac muscle cells
The process of excretion of large amounts of Na+ in the urine
Natriuresis
T/F RAAS and natriuretic system work in opposition to each other in adjusting Na+ reabsorption
True
Glucose and amino acids reabsorbed from filtrate back into peritubular capillaries using energy from Na+ gradient
Secondary active transport
How is reabsorption of glucose accomplished?
Through secondary active transport
moves Na+ down its concentration gradient in order to move glucose against its concentration gradient
Sodium and glucose cotransporter (SGLT)
facilitated diffusion—moves glucose down its concentration gradient
Glucose transporter (GLUT)
What are the two hormones involved with Natriuresis?
Atrial natriuretic peptide (ANP) and Brain natriuretic peptide (BNP)
