Renal physiology Flashcards
What is the major function of the Kidney?
To maintain homeostasis for a large number of solutes and water
How is homeostasis maintained?
Through the kidney by changing its rate of excretion
What is the key solute in renal physiology?
Sodium (Na+)
In what fluid compartment is Na restricted to?
Sodium is restricted to the extracellular space.
What electrolyte determines the (ECFV) extracellular fluid volume
Total body sodium
What does ECFV determine?
Blood Pressure and Blood Volume
Since Na+ determines osmolality what does that influence?
Total body water
What is Vasopressin?
Peptide hormone that stimulates water reabsorption in principal cells of collecting ducts and constriction of arterioles
How does Vasopressin work?
Vasopressin regulates the body’s retention of water by acting to increase water absorption in the collecting ducts of the kidney nephron. Vasopressin increases water permeability of the kidney’s collecting duct and distal convoluted tubule by inducing translocation of aquaporin-CD water channels in the kidney nephron collecting duct plasma membrane.
Which is the major intracellular cation?
Potassium K+
What is the major extracellular anion?
Cl-
Which organ regulates the total body content of Cl-
Kidney
What is the other major extracellular anion?
Bicarbonate HCO3−
What is the percentage of Body water in humans?
Males:60% Females:50%
What is the major ECFV buffer?
Bicarbonate
What is the key factor in Acid-Base balance?
Bicarbonate
What is the normal body pH?
7.40
What are some of the waste materials that the kidney excretes?
- Urea (by-product of protein metabolism)
- Creatinine
- Uric acid
What glycoprotein produced by the kidney is responsible for rbc production?
Erythropoietin
In terms of anemia what what kind of anemia would reduced kidney function be associated with?
- Low reticulocyte count
2. Normocytic normochromic anemia
What is the major source of 1-alpha hydroxylase
Kidney
What are the minor sources of 1-alpha hydroxylase?
Skin (kerationocytes) Bone (osteoblasts) and immune cells
What is the function of 1-alpha hydroxylase?
1-alpha hydroxylase is located in the proximal tubule of the kidney and a variety of other tissues, including skin, immune cells, and bone. The enzyme catalyzes the hydroxylation of calcidiol to calcitriol which is the bioactive form of Vitamin D
Would reduced kidney function result in reduced 1-alpha hydroxylase as well as reduced Vitamin D?
Yes.
What is the Chief source of Renin in the body?
Kidney
What is Renin?
proteolytic enzyme produced by granular cells in the kidney that catalyzes the formation of angiotensin I from angiotensinogen
Where is renin produced?
Juxtaglomerular apparatus by specialized cells
granular cells
What is Bradykinin?
nonapeptide hormone that causes a slowly developing contraction of intestinal smooth muscle, vasodilation, and increased renal sodium excretion
Which of the Prostaglandins are perticularly important in maintaining homeostasis and are vasodilatory?
PGI2 & PGE2
Which is the critical organ that maintains BP?
Kidney
What is angiotensin II?
peptide hormone formed from the proteolysis of angiotensin I by converting enzyme in the lungs; potent vasoconstrictor, enhances the effectiveness of sympathetic nerve stimulation to blood vessels, and promotes salt and water retention in the body primarily by stimulating the release of aldosterone from
the adrenal cortex.
What are some of the secondary functions of the kidney?
- Catabolism of small peptides i.e Insulin (decreased nephron mass = slower degradation of insulin)
- Produce small amounts of glucose via gluconeogenesis during fasting
- Elimination of many medications
What is meant by positive balance?
State in which intake plus endogenous production > renal excretion rate
2.Leads to increased total body content of the substance
What is meant by negative balance?
Intake plus endogenous production < renal excretion rate
How does one examine whether the kidney is functioning correctly?
Examine the urine
Where is the plasma ultrafiltrate formed?
At the Glomerulus
What is the Glomerulus essentially?
A Big BAll of Capillaries
What is Ultrafiltration?
filtration through a selectively permeable membrane that allows passage of small molecules but restricts the passage
of large molecules, such as proteins
What is Glomerular ultrafiltrate normally free of?
Proteins and cells
What does the kidney require in order to make this filtrate?
An enormous amount of blood flow.
What percentage of the Cardiac output does the kidney receive?
10%
What percentage of the Glomerular filtrate must be reabsorbed?
98-99%
What would result from disability to absorb renal filtrate?
Go into shock.
Approximately how many litres a day are reabsorbed?
178
What is the major site of Oxygen consumption in the kidney?
Renal tubules
What is the best index of overall kidney function?
(GFR) Glomerular filtration rate
What are the processes involved in renal function?
- Glomerulafiltration
- Reabsorption
- Secretion
- Excretion
What very potent vasosonstrictor is produced by the kidney in response to endothelial injury?
Endothelin
What is the primary function of the tubules?
Re-absorption
What is involved in secretion?
Addition of some solutes i.e K+ from peritubular capillaries to the tubules
What percentage of renal blood flow does the cortex receive?
90%
Where do ALL glomeruli reside?
Renal cortex
What resides in the renal Medulla?
Tubular structures:
- Loops of Henle
- Collecting Ducts
- Vasa recta
What is in the Hilum?
- Main renal artery
- Main renal vein
- renal pelvis
- Ureter
- Renal nerves
- Lymphatics
Where does urine exit?
One urine is formed it exits at the renal papillae of the medulla and goes through a number of minor calyces that come together in 3-5 major calyces then coalesce into the renal pelvis.
What is the flow of urine out of the body?
- Renal Pelvis joins the ureter
- Descends in the retroperitoneum
- Crosses over the pelvic brim across vascular structures
- Down into the urinary trigone of the bladder
What are the three points of potential obstruction within the ureter?
- Pelvic uretal juction
- Crossover of pelvic brim
- Urinary trigone (bladder)
What are the differences between male and female urethra?
- Male urethra goes through median lobe of the prostate
2. The male urethra is longer and less UTI prone
What is common among aging pertinent to the urethra?
Enlargement of the prostate which obstructs the the prostatic urethra
What are the principle type of bacteria associated with female urinary tract infections?
Gram-negative
What arteriole enters the Glomerulus?
Afferent arteriole
What arteriole leaves the Glomerulus?
Efferent arteriole
What are the two types of Nephrons?
- Cortical
2. Juxtamedullary
What percentage of the nephrons are Cortical?
85%
What are the differences in the cortical nephrons?
- NEVER OPERATION @ 100% always have some reserve capacity
- Closest to renal capsule (superficial nephron)
- Smaller than Juxtamedullary nephron
- Perfusion pressure is lower than that of Juxtamedullary nephrons
- Filtration is lower than that of Juxtamedullary nephrons
- Have short loops of Henle
What are some differences in Juxtamedullary Nephrons?
- Longer loops of Henle
- Some will descend into the renal papilla
- Higher perfusion pressure than Cortical nephrons
- Filtration rate is higher than in cortical nephrons
What are the important functions linked to the Juxtamedullary nephrons? (long loop)
- Maximal water conservation making maximally concentrated urine
- Medullary thick ascending limb is major site of Na+ transport (produces hypertonic medullary interstitium)
- Efferent arterioles becomes descending vase recta which is the only arterial blood supply to medulla
What brings the blood supply to the medulla?
Vasa recta
What is important in maintaining the medulla in hypertonic fashion pertaining to the vasa recta.
Solute transfer between ascending and descending vasa recta
What do the efferent arterioles from CORTICAL nephrons become?
Peritubular capillary network in the renal cortex.
