Urinary System Flashcards
Functions of the kidneys
(Hint: 6 )
Structure of urinary system
Urine produced from the kidneys move from:
Kidney ➡️ renal pelvis ➡️ ureters ➡️ bladder ➡️ urethra
The kidney has two regions :
Cortex and Medulla
Arterial blood enters the kidney through which artery ?
Renal artery
The renal artery divides into ______________________ , then subdivides into numerous ____________________.
Interlobar arteries
Afferent arterioles
Which blood vessels deliver blood to the glomeruli
Afferent arterioles
What are glomeruli
Capillary networks that produce blood filtrate that enters the urinary tubules
(It filters the blood from the afferent arterioles, and that filtrate moves into the urinary tubules while the now filtered blood continues into the efferent arteriole.)
The blood remaining in the glomerulus leaves through an ________________________.
Efferent arteriole
The efferent arteriole delivers the blood to _________________.
Peritubular capillaries
Peritubular capillaries surround what structure ?
Renal tubules
Where does the blood from the Peritubular capillaries drain into
Veins and eventually leaves the kidney as a single RENAL VEIN
Renal circulation summary steps:
- Blood goes from Renal artery > interlobar arteries > afferent arteriole
- Afferent arterioles delivers blood into glomeruli
- Glomerulus filters the blood and the blood filtrate enters urinary tubules + the remaining filtered blood leaves through efferent arteriole
- The blood moves from efferent arteriole > peritubular capillaries > veins > renal vein
what is a nephron
Function unit of the kidney where urine is formed
How many nephrons in a kidney
About one million
Nephron blood circulation
Nephron filtrate flow in tubules
(After being filtered in the golmerulus , where does the filtrate go?)
Very important to know ALL these parts to understand the rest of the note
I know
3 main types of nephrons + how much each type makes up of total nephrons %
- Juxta-medullary (10%)
- Cortical nephrons (20%)
- Mid-cortical (70%)
Characteristics of juxta-medullary nephrons
- deep glomeruli (in cortex near medulla)
- long loops of Henle
- their peritubular capillaries are modified into VASA RECTA
What is vasa recta
Long hair-pin shaped blood vessels that surround the loop of Henle
(Modified peritubular capillaries in juxta-medullary nephrons)
What feature of the juxta-medullary nephron plays a role in concentrating urine (more water absorption) ?
Long loop of henle
Juxta-medullary nephrons play an important role in :
Concentration of urine
Vasa recta are modified ___________________________ for juxta-medullary nephrons .
Peritubular capillaries
Characteristics of cortical nephrons
- glomeruli in superficial cortex
- short loops of Henle
Characteristics of mid-cortical nephrons
- glomeruli in mid cortex
- loops of Henle are of intermediate length
Sympathetic stimulation effect on the kidney
(Important and easy)
- Contracts smooth muscles of major branches of renal artery + afferent arterioles + efferent arterioles = VASOCONSTRICTION
(Vasoconstriction > less blood flow > less blood filtration > ⬇️GFR)
- Acts on β adrenergic receptors in the juxtaglomerular apparatus to cause the release of RENIN (enzyme)
(Angiotensinogen ➡️ ٍRenin ➡️ Angiotensin 1)
(Angiotensin 1 ➡️ ACE ➡️ Angiotensin 2)
AND ANGIOTENSIN 2 IS A VASOCONSTRICTOR (so also ⬇️ GFR)
NOTE:
Renin and ACE are enzymes
- Acts on α adrenergic receptors in the collecting ducts to increase Na+ reabsorption
What converts angiotensinogen to angiotensin 1
Renin
Where is angiotensinogen produced
Liver
What produces Renin
Kidney (specifically juxtaglomerular apparatus)
What two cell types are present in the Juxtaglomerular apparatus
Granular cells
Macula dense
What happens to GFR when the sympathetic nervous system is activated and why
⬇️ GFR
Why?
- vasoconstriction
- renin (angiotensin 2 is vasoconstrictor)
Sympathetic stimulation effect on β adrenergic receptors
Release of renin from juxtaglomerular apparatus
Sympathetic stimulation effect on α adrenergic receptors in collecting duct
Increase Na+ reabsorption
What is renal blood flow
Blood volume delivered to the kidneys per unit time 
Unit of renal blood flow RBF
ml / min
L / min
Renal blood flow is _____ % of cardiac output
20%
If cardiac output if 5 L/min, then what is renal blood flow?
RBF is 20% of cardiac output so
20/100 x 5 = 1 L/min
What is renal plasma flow
Volume of plasma delivered to the kidneys every minute
Renal plasma flow depends on two things:
- Renal blood flow
- Hematocrit
Renal blood flow is regulated through three different ways:
- Autoregulation
- Neural regulation
- Humoral regulation
What is meant by renal autoregulation
Maintaining renal blood flow constant under changes in blood pressure in order to maintain constant GFR
(Meaning in order for the GFR to remain constant , the renal blood flow has to be constant as well , so that’s why we need autoregulation in case of changes in blood pressure) 
What is the blood flow formula
During autoregulation, which blood vessel is manipulated to control renal blood flow to kidneys?
Afferent arteriole
Describe what happens to the afferent arteriole during changes in blood pressure to keep the GFR constant !
BP ⬆️ = VASOCONSTRICTION = constant GFR
BP ⬇️ = VASODILATION = constant GFR
(We need to maintain blood flow to maintain constant GFR)
In autoregulation , increased blood pressure leads to ___________________ of afferent arteriole.
Vasoconstriction
In autoregulation , decreased blood pressure leads to ___________________ of afferent arteriole.
Vasodilation
In the absence of neural and hormonal factors, the kidney maintains renal blood flow and GFR ( through autoregulation) within what pressure range ?
80 to 200 mmHg
Neural regulation of renal blood flow is done by
Sympathetic noradrenergic (NE) nerve fibers
Humoral regulation of renal blood flow is done through
( you must know which causes vasoconstriction and vasodilation and which are involved in autoregulation)
Answer in the picture
Hints:
Vasoconstriction: AE
Vasodilation : NAP
Autoregulation: PEN
What is the first step in urine formation
Filtration
(Or glomerular filtration)
What occurs during filtration
Blood passes through the glomerulus and a fraction of it is filtered through the glomerular filtration barrier GFB
How much of plasma is filtered as blood passes through the glomerulus
20% of plasma
What is reabsorption
The retrieval of water and some solutes (NaCl, glucose, amino acids) from the tubule fluid back into the peritubular capillary blood
What is secretion
The addition of some substances from the peritubular capillary blood or from the tubule cells into the luminal fluid