PSC1002/L11 Renal System Flashcards
What is the functional unit of the kidney?
Nephron
What are juxtamedullary nephrons involved in?
Making concentrated urine
Describe the structure of a nephron. (6)
Bowman’s capsule into proximal convoluted tubule
Descending limb
Loop of Henle
Ascending limb
Distal convoluted tubule
Collecting tubules/duct
What is the approximate renal blood supply?
1.2 L/min
Describe the vascular supply to nephrons. (5)
Afferent arterioles feed into glomeruli
Efferent arterioles leave glomeruli and wrap around nephron
Peritubular capillaries or vasa recta
Renal veins
Inferior vena cava
What can be inferred from the fact that an arteriole leaves the capillary bed of the nephron?
Role is not to supply oxygen but for reabsorption
Give 3 functions of the kidney.
Homeostatic regulation of water and ion content of blood
Excretion of metabolic waste products and foreign substances
Production of hormones
Give 3 hormones produced by the kidney.
Erythropoietin
Renin
Bone prostaglandins & kinins
What 3 processes occur in the kidney?
Glomerular filtration
Tubular reabsorption
Tubular secretion
What is glomerular filtration and where does it occur?
Blood filtered at glomerulus
Renal corpuscle
What is tubular reabsorption?
Fluid and solutes are reabsorbed from the filtrate and returned to the blood
What is tubular secretion?
Substances are secreted from blood into filtrate
What is filtered in the kidneys?
All plasma constituents except proteins >67kDa
How does the filtration barrier restrict solute movement? (2)
On size and charge
What is the average glomerular filtration rate (GFR)?
180 L/day
Total plasma filtered 2.5x per hour
What are fenestration pores?
Small spaces within the endothelial cell layer of filtration barrier
What is a podocyte?
Modified epithelial cells of the capsular epithelium and renal glomerulus
Name 4 substances that get filtered in the kidneys.
H2O
Na+
K+
Ca2+
Cl-
Glucose
NH4+
Creatinine
Uric acid
What 3 pressures contribute to filtration?
Hydrostatic pressure of blood in glomerular capillaries (P(H))
Colloid osmotic pressure (Pi)
Hydrostatic pressure of fluid in Bowman’s space (Pfluid)
What is the equation for net filtration pressure? Give an approximation.
NFP = P(H) - Pi - Pfluid
55 - 30 - 15 = 10 mmHg
How would an increase in resistance of afferent arteriole affect renal blood flow? (2)
Decrease hydrostatic pressure
Decrease GFR
How would an increase in resistance in the efferent arteriole affect renal blood flow?
Decreases blood flow out of glomerulus
Increases pressure in glomerulus
What mechanisms maintain RBF and GFR within narrow limits?
Myogenic response
Tubuloglomerular feedback
Describe the myogenic response. (5)
Increased BP
Stretch of SMC
Vasoconstriction
Decreased RBF
Decreased PH & GFR
Define tubuloglomerular feedback.
Fluid flow through tubule influences arteriole resistance and GFR
Explain how tubuloglomerular feedback works. (8)
GFR increases
Flow through tubule increases
Flow past macula densa increases (sensed ions)
Paracrine factors released from macula densa (Adenosine, ATP, NO)
Afferent arteriole constricts
Resistance in afferent arteriole increases
Hydrostatic pressure in glomerulus decreases
GFR decreases
