Renal Physiology Flashcards
What is the kidney?
Bilateral bean-shaped organ which is reddish-brown in colour, is retroperitoneal and located in the posterior abdomen at T12-L3 which is responsible for filtration, excretion and blood pressure control.
What vertebral level is the kidney situated at?
T12-L3
What are the physiological functions of the kidney?
- Regulation of body fluid volume and osmolality
- Maintenance of ion balance
- Acid-base balance
- Waste excretion
- Vitamin D hydroxylation (25-hydroxycholecalficerol + 1a hydroxylase 1,25 a hydroxycholecalciferol (calcitriol))
- EPO
- Renin production
Define blood pressure.
pressure exerted by ventricles (circulatory system) against arterial walls
Give the equation for Blood Pressure.
BP = CO x TPR
Which factors affect arteriolar radius.
- Neural controls: SNS vs NO-releasing nerves
- Hormonal controls: AGT/Adrenaline/AVP vs Adrenaline/ANP
- Local controls: Myogenic response/Endothelin-1 vs Hypoxia/Potassium/Carbon Dioxide/Acid/Adenosine/Nitric Oxide/Bradykinin
List 4 hormonal controls responsible for vasoconstriction and vasodilation of blood vessels.
Which variable of the cardiac output equation does this affect?
Hormonal controls: AGT/Adrenaline/AVP vs Adrenaline/ANP
TPR
List 4 local controls responsible for vasoconstriction and vasodilation of blood vessels.
Which variable of the cardiac output equation does this affect?
Myogenic response/Endothelin-1 vs Hypoxia/Potassium/Carbon Dioxide/Acid/Adenosine/Nitric Oxide/Bradykinin
What is cardiac output?
rate of blood pumped out of LV into systemic circulation (L/min)
List the variables for Cardiac Output and the factors for each.
• Heart Rate:
- PSNS (Brake)
- SNS (Accelerator)
- Adrenaline
- Drugs
• Stroke Volume:
- SNS (increased)
- EDV (SNS veins/ BV/ skeletal muscle pump/ respiratory pump -> venous pressure -> venous return)
In the case of hypovolemia, outline how the RAAS mediates homeostatic changes.
• Hypovolemia ± low osmotic pressure -> reduced BP + increased Na+ -> macula densa detects elevated salts -> reduced baroreceptor firing = reduced SNS drive (= NA) -> renin release (kidney) = angiotensinogen (liver) -> angiotensin I + ACE (lungs) -> angiotensin II…
- Arteriolar vasoconstriction (TPR increases)
- Efferent glomerular arteriole vasoconstriction (maintain GFR and salt reabsorption)
- ADH secretion (AGT II binds posterior pituitary)
- Salt + water reabsorption via aldosterone release (AGT II binds zona glomerulosa of adrenal cortex = aldosterone release)
What mnemonic can be used to remember the effects of Angiotensin II?
Mnemonic: ‘Pressure to get 5 As’
Aldosterone release (zona glomerulosa)
Arteriolar vasoconstriction
Arteriole (glomerular efferent) vasoconstriction
ADH release (posterior pituitary)
Absorption (re-absorption): Proximal tubule
Outline the role of ADH in low blood pressure?
Is ADH more responsive to:
A. Hypovolemia
B. Osmotic pressure (increased osmolarity)
C. Hypervolemia
• Low osmotic pressure (increased osmolarity) ± reduced blood volume -> reduced BP -> hypothalamic osmoreceptors detect ∆ -> neuronal afferents to posterior pituitary gland = ADH/AVP released:
- Increased water permeability (renal collecting ducts) = increased blood volume + reduced urinary output
- Vasoconstriction = increased TPR
- Dipsogenic: Hypothalamic thirst center
B. Osmotic pressure (increased osmolarity)
What 3 main effects does ADH have to mediate changes in blood pressure?
Mnemonic: People Value Dipsogenesis
Permeability
Vasoconstriction
Dipsogenic
Outline how ANP functions in response to raised blood pressure.
• Increased osmotic pressure/increased blood volume -> increased BP -> detected by atrial cardiopulmonary baroreceptors in atrial cardia = increased baroreceptor firing -> ANP release -> afferent arteriole vasodilation + increased flow through vasa recta (reduce osmolarity of medullary interstitium) + increase collecting duct Na+ excretion -> reduce blood volume = reduce BP
- Natriuresis:
- Arteriole (afferent) vasodilation
- Aldosterone reduced (zona glomerulosa)
- Vasodilation (vascular)
- Fibrosis (anti-fibrotic)
State the mnemonic used to remember the effects ANP has on blood pressure.
Mnemonic: FAVourite NA
Fibrosis reduced
Arteriole (afferent) vasodilation
Vasodilation
Natriuresis
Aldosterone reduced
Outline the effect PGs have on renal control of blood pressure.
• Reduced BP -> Prostacyclin (PGI2) and PGE2 released -> afferent arteriole vasodilation -> increased GFR -> reabsorption of ions across nephron -> increase BP
Outline the effect EPO has on mediating blood pressure control.
Include the drive for EPO production.
State the site of production of EPO.
• Reduced blood volume (hypovolemia) -> reduced O2 availability ≈ Hypoxia -> HIF-2 -> EPO enhancer -> EPO production (kidney) -> increased erythropoiesis ≈ increased Hematocrit (increased MCV; reduced MCHC?) = increased BP
Kidney
Define Mean Cell Volume.
Give the equation for MCV.
State the three classifications for MCV.
• Average volume of RBCs
MCV = Hct/ RBC
- Microcytic (60-80fl): iron deficiency, thalassemia
- Normocytic (80-100fl): blood loss, chronic disease anaemia, renal impairment
- Macrocytic (100-120fl): megaloblastic anaemia, B12/folate deficiency, myelodysplasia
Should a patient have a MCV of 70fl, what MCV category is this?
Microcytic (60-80fl)
Should a patient have a MCV of 90fl, what MCV category is this?
Normocytic (80-100fl)
Should a patient have a MCV of 110fl, what MCV category is this?
Macrocytic (100-120fl)
What is MCH? Give the equation.
MCH = Hb/RBC
• Average mass of Hemoglobin per red blood cell
What is MCHC? Give the equation.
MCHC = Hb/Hct
• Average concentration of Hemoglobin per volume of red blood cells
Give the two divisions/classifications of MCHC (Hb/Hct).
- Normochromic: Cells with normal [Hb]
- Hypochromic: Cells with low [Hb]
Describe the connective tissue layers and state their function generally.
1) Fibrous capsule
Layer of collagen fibres that covers outer surface of entire organ
Surrounds the adrenal gland but there is a septum between the 2 structures to separates them
2) Perinephric fat
Thick layer of adipose tissue that surrounds fibrous capsule
Adipose tissue acts as shock absorber and provides protection
3) Renal fascia
Dense, fibrous outer layer that anchors kidney to surrounding structures
Posteriorly, renal fascia fuses with deep fascia surrounding muscles of the body wall
Anteriorly, renal fascia forms thick layer that fuses with peritoneum
Outline the neurovasculature of the kidney.
Arteries
- Renal arteries (abdominal aorta)
- Renal hilum
- Segmental branches —> interlobular arteries —> arcuate arteries —> vasa rata —> afferent arterioles —> capillary network
Veins:
- Renal veins
- Leave hilum anteriorly, crossing abdominal aorta and empties into IVC ; L longer than R as IVC on RHS of body
Which vein is longer and why, left renal vein or right renal vein?
L is longer than R, as IVC is on RHS of body
What are the tributaries to the renal veins?
Left gonadal and left suprarenal veins drain into L renal vein; Right gonadal and right suprarenal veins drain into R renal vein
What is the outermost renal area termed?
A. Medulla
B. Cortex
C. Renal pelvis
D. Major Calyx
B. Cortex
What is the innermost renal area termed?
A. Medulla
B. Cortex
C. Renal pelvis
D. Major Calyx
A. Medulla
What is the region of the cortex bearing the majority of the nephrons termed?
A. Medulla
B. Renal pyramids
C. Renal pelvis
D. Major Calyx
B. Renal pyramids
What is the region of the extending from the cortex into the renal medulla termed?
A. Medulla
B. Renal pyramids
C. Renal columns
D. Major Calyx
C. Renal columns
What is the region of the kidney whereby the renal pyramids empty into the medulla termed?
A. Medulla
B. Renal pyramids
C. Renal papilla
D. Major Calyx
C. Renal papilla
What is the region of the kidney whereby urine is received from the renal papilla and transferred to the major calyx termed?
A. Medulla
B. Minor Calyx
C. Renal papilla
D. Major Calyx
B. Minor Calyx
What is the region of the kidney whereby urine is received from the minor calyx and transferred to the renal pelvis termed?
A. Medulla
B. Minor Calyx
C. Renal papilla
D. Major Calyx
D. Major Calyx
What is the region of the kidney whereby urine is received from the major calyx and ureter termed?
A. Medulla
B. Minor Calyx
C. Renal pelvis
D. Major Calyx
C. Renal pelvis
What is the term for the point at which the renal pelvis joins with the ureter?
Pelviureteric junction
List the order of connective tissue layers around the kidney.
- Fibrous capsule
- Perinephric fat
- Renal fascia (Gerota’s fascia)
Which connective tissue layer of the kidney fuses with the peritoneum anteriorly and deep fascia posteriorly?
Renal fascia (Gerota’s Fascia)
What is the eponymous term for Renal Fascia?
Gerota’s Fascia
Which vessel gives rise to the afferent arteriole.
A. Interlobular vein
B. Interlobular artery
C. Intertubular capillary
D. Intersegmental artery
B. Interlobular artery
Outline the flow of blood from the aorta to the glomerulus.
Ascending aorta –> Desceding Aorta –> Renal artery (L1/L2) –> Intersegmental artery –> Interlobular artery –> Afferent arteriole
Outline the flow of blood to and from the glomerulus.
Intersegmental artery –> Interlobular artery –> Afferent arteriole –> Peritubular capillary bed –> Interlobular vein –> Descending and Ascending Vasa Recta –> Intersegmental vein
What is the term for the continuation of peritubular capillaries.
A. Vasa recta
B. Intertubular capillary bed
C. Interlobular artery
D. Interlobular vein
A. Vasa recta
What are the two types of nephron?
i) Superficial nephron: Glomeruli in outer cortex, shorter LoH dipping into outer medulla
ii) Juxtamedullary nephron: Glomeruli near corticomedullary border with larger glomeruli and higher GFR; LoH deeper into inner medulla and papilla which concentrate urine more
What is the term for a nephron with its glomeruli situated in the outer cortex.
A. Juxtamedullary nephron
B. Standard Nephron
C. Peritubular Nephron
D. Superficial nephron
D. Superficial nephron
What is the term for a nephron with its glomeruli situated in the medulla.
A. Juxtamedullary nephron
B. Standard Nephron
C. Peritubular Nephron
D. Superficial nephron
A. Juxtamedullary nephron
What type of nephron concentrates urine more?
A. Juxtamedullary nephron
B. Standard Nephron
C. Peritubular Nephron
D. Superficial nephron
A. Juxtamedullary nephron
Describe the glomerulus.
A. Ball of blood vessels with intersegmental arteriole entering then efferent arteriole leaving
B. Ball of blood vessels with afferent arteriole entering then efferent arteriole leaving
C. Ball of blood vessels with efferent arteriole entering then afferent arteriole leaving
D. Double-walled capsule contiguous with glomerulus bearing parietal SSE.
B. Ball of blood vessels with afferent arteriole entering then efferent arteriole leaving