The kidneys: structure and function Flashcards
What are the 10 functions of the kidney?
1) Water balance
2) Salt balance
3) Maintenance of plasma volume
4) Maintenance of plasma osmolarity
5) Acid-base balance
6) Excretion of metabolic waste products
7) Excretion of exogenous foreign compounds
8) Secretion of renin (control of arterial blood pressure)
9) Secretion of erythropoietin (RBC production)
10) Conversion of vitamin D into active form (Calcitriol: Ca2+ absorption in GI tract)
what is the main function of the kidney?
Regulates volume, composition and osmolarity of body fluids
what is the balance concept of any substance?
Total ingested + Total excreted= Total produced + Total consumed
how can kidneys contribute to the balance of these substances?
Kidneys role is the controlled excretion of ions such as Na+ and K+ and fluids such as urine to maintain constant internal environment
what does the urinary system consist of?
- the kidneys (produce urine)
- the structures that store and carry the urine from the kidneys to the outside for elimination from the body
what veins and arteries go into the kidneys?
Renal artery and renal veins
what is the kidney made up of?
- renal cortex
- renal medulla
- renal pyramid
- renal pelvis
- ureter
what is the appearance of the renal cortex and renal medulla?
Cortex- granulated
medulla- striated
how much cardiac output does the kidneys receive?
25%
what makes up the renal medulla?
renal pyramids
where does urine travel in the kidneys?
urine comes from the renal pyramids and collects in the renal pelvis before draining into the ureter
what is a nephron?
the functional unit of the kidney
what are the functional mechanisms of the nephron?
- Filtration
- Reabsorption
- Secretion
what are the two parts to the renal artery?
- afferent arteriole
- efferent arteriole
what is the tubular loop in a nephron?
loop of Henle
what are the 2 types of nephron?
- juxtamedullary (20%)
- cortical (80%)
what are the differences between juxtamedullary and cortical nephron?
- the juxtamedullary has a bigger loop of henle so it depends down further into medulla
- it doesn’t have peritubular capillaries but has vasa recta capillaries
what is the difference in diameter between afferent and efferent arterioles/
the diameter of the afferent arteriole is larger than that of efferent arterioles
what is the outer layer of bowman capsule made of?
Epithelial cells
what is the inner layer of bowman capsule made of?
podocytes
what is the juxtaglomerular apparatus?
where the distal tubule of the nephron passes between the efferent and afferent arterioles
what are macula densa?
a group of specialised tubular cells that are salt sensitive to see its concentration in tubular fluid
what is urine?
Modified filtrate of the blood
what do the kidneys incorporate?
- Filtration system
- Rich blood supply
- Mechanisms for urine modification
i) reabsorption and ii) secretion
what are the 3 basic renal processes?
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
what happens to the plasma that enters the glomerulus?
- 20% is filtered
- 80% is not filtered and leaves through the efferent arteriole
why is the renal tubule described as a “conveyor belt”?
substances are added or removed as urinary filtrate moves from proximal to distal end
what is the equation for rate of excretion?
Rate of excretion = rate of filtration + rate of secretion - rate of reabsorption
what is the rate of filtration of a substance?
[X}plasma x GFR ( glomerular filtration rate)
what is the rate of excretion of a substance?
Rate of excretion of X = [X]urine x Vu (urine flow rate)
what happens if rate of filtration is higher than rate of excretion?
net reabsorption of that substance has occurred
what is the equation for rate of reabsorption?
Rate of reabsorption of X = rate of filtration of X – rate of excretion of X
what is the equation for rate of secretion?
Rate of secretion of X = rate of excretion of X – rate of filtration of X
