(F) L4: Renal Function (Part 1: Introduction) Flashcards
- Paired bean-shaped organs located retroperitoneally on either side of the spinal column below the ribcage
- Is 4-5 inches in length, 2-3 inches in width, and 3 inches thick
- Is divided into a cortex and medulla with an outer renal capsule layer
Kidneys
Recall the 3 main urine waste products (no choices, recall NPNs in CC):
1. From protein metabolism (ammonia first, then this)
2. From muscle metabolism (a marker for GFR)
3. From purine metabolism
- Urea
- Creatinine
- Uric Acid
If NPNs are (elevated/decreased) in blood, one possibility is because of kidney disease
Elevated
- Aka vasopressin
- Purpose: For water absorption
Antidiuretic Hormone (ADH)
Antidiuretic Hormone (ADH)
Hypothalamus vs. Posterior Pituitary Gland
1. Which endocrine gland synthesizes ADH?
2. Which endocrine gland released/secretes ADH?
- Synthesis - Hypothalamus
- Release/Secretion - Posterior Pituitary
Recall in Anaphy/Histo that the pituitary merely STORES hormones produced by the hypothalamus until they are needed
Antidiuretic Hormone (ADH)
The posterior pituitary releases ADH whenever blood volume is (increased/decreased) while blood osmolality is (increased/decreased)
Blood volume: Decreased
Blood osmolality: Increased
Antidiuretic Hormone (ADH)
ADH promotes water reabsorption which makes what part of the kidney more permeable to water?
Distal Convoluted Tubules (DCT)
Antidiuretic Hormone (ADH)
A deficiency of ADH causes what disease?
Diabetes Insipidus (increased frequency of urination)
These 3 electrolytes may be secreted or absorbed depending on the hormones present (e.g. aldosterone)
Note: Where sodium goes, water follows
- Sodium (Na+)
- Potassium (K+)
- Chlorine (Cl-)
Aside from sodium, potassium, and chlorine, what are the other 3 electrolytes in the blood?
- Phosphate
- Calcium
- Magnesium
What 2 organs are responsible for the maintenance of the acid-base balance?
- Kidneys
- Lungs
The kidneys maintain the acid-base balance by reabsorbing (blank) and excreting (blank)
- Reabsorption of bicarbonate
- Excretion of acids (hydrogen ions)
Endocrine Functions
- Is released when BP and/or sodium is low
- There is a vasoconstriction and regulation of osmolarity
- Part of the RAAS and produced by the juxtaglomerular apparatus
- This decreases blood volume
Renin
Endocrine Functions
- Is secreted to stimulate the production of RBCs
- There is a chance of acquiring anemia secondary to chronic kidney disease because of the affected production of this hormone
- Can cause hypoxia and anemia
Erythropoietin (EPO)
Endocrine Functions
- Aka Calcitriol (active vitamin D)
- Increased blood calcium levels
1,25-dihydroxy vitamin D3
Endocrine Functions
- A vasodilator
- Increases permeability, renal blood flow, sodium and H2O secretion and release of renin
Prostaglandins
- The basic functional unit of the kidney
- Around 1 to 1.5 million of these per kidney
- Has a glomerulus, renal tubules, and collecting ducts
Nephron
What is the number 1 requirement in order to filter metabolic waste products for urine formation?
Renal blood flow
Familiarize with the general renal blood flow
- Renal artery
- Afferent arteriole
- Glomerulus
- Efferent arteriole
- Peritubular capillaries
- Vasa recta
- Renal vein
RAGE-PVR
Give the corresponding values for urine formation:
1. Cardiac output in percent?
2. Renal blood flow in mL/min.?
3. Renal plasma flow in mL/min.?
4. Renal filtrate in mL?
A. 600-700
B. 21-25
C. 1,200
D. 130
- Cardiac: 21-25%
- Blood flow: 1,200 mL/min.
- Plasma flow: 600-700 mL/min.
- Renal filtrate: 130 mL/min.
Give the 3 major steps of urine formation
- Glomerular filtration
- Tubular reabsorption
- Tubular secretion
Filtration
This acts as a non-selective sieve/filter
Glomerulus
Filtration
- Aka basal lamina
- Substances with a MW of < 70k (or 66k) can pass through this
- Cells and large molecules are not able to pass here
Glomerular Basement Membrane
Filtration
Passage through the GBM, possible or not?
1. Water, Glucose, Amino Acids, Low MW proteins, and Waste products (creatinine and urea)
2. Cells, plasma proteins, and conjugated proteins (lipoproteins and bilirubin)
3. Albumin
- Possible
- Not possible
- Not possible
Filtration
Albumin cannot pass through the GBM despite its MW being only 69k because the glomerulus has what?
Shield of negativity (will only pass through if the glomerulus is damaged)
Note: Albumin is (-) charged; like signs repel
Reabsorption
- This receives the glomerular filtrate
- The major site of reabsorption of important substances
Proximal Convoluted Tubule (PCT)
Reabsorption (important substances)
- Reabsorbed by BOTH PCT and DCT
- Aldosterone is responsible for regulating this substance
Sodium (Na+)
Reabsorption (important substances)
- Reabsorbed by the PCT, DCT, and Collecting Ducts
- This gets reabsorbed because of ADH/vasopressin (effective towards the collecting duct)
Water
Reabsorption (important substances)
- Has a threshold of 180 mg/dL
- Once it surpasses the threshold, it will now be present in the urine
Glucose
Reabsorption (important substances)
Is not commonly used anymore for Clearance Tests because of the tendency of tubules to reabsorb it
Urea
Reabsorption
Reabsorbed by BOTH PCT and DCT
A. Water
B. Sodium
C. Both
D. Neither
C. Both
Reabsorption
Reabsorbed by the collecting duct only
A. Water
B. Sodium
C. Both
D. Neither
A. Water
Reabsorption
This portion regulates the osmolarity of the interstitial fluid from the renal medulla
Loop of Henle
Reabsorption (Loop of Henle: Countercurrent Multiplier System)
- Impermeable to water
- Sodium (Na+) and Chloride (Cl-) are reabsorbed
Ascending
Reabsorption (Loop of Henle: Countercurrent Multiplier System)
Highly reabsorbs water (passive movement)
Descending
Secretion
- The major site of secretion
- Able to eliminate waste products such as creatinine and urea
- Regulates sodium and potassium and releases vasopressin
Distal Convoluted Tubule (DCT)
Secretion
What are the 3 secreted hydrogen ions for acid-base balance?
- Ammonium ions
- Dihydrogen phosphate
- Weak organic acids
Specimen: Urine
Secretion
The final site of urine concentration and/or dilution
Collecting Ducts
Secretion
Aldosterone, RAAS, and ADH act on what 2 parts of the kidney?
- Distal convoluted tubule (DCT)
- Collecting duct
Familiarize yourself with the pathway of urine formation
- Kidneys
- Renal pelvis
- Ureter
- Urinary bladder
- Urethra
- Excretion
Glomerular Filtration (can be filtered)
A. Cells
B. Large Molecules
C. Both
D. Neither
D. Neither (these CANNOT be filtered)
Tubular Reabsorption
A. Distal Convoluted Tubule
B. Loop of Henle
C. Both
D. Neither
B. Loop of Henle (the DCT is for tubular secretion, PCT is for reabsorption)
Tubular Reabsorption
A. Countercurrent Multiplier System
B. Amino acids and Vitamins
C. Both
D. Neither
C. Both
Loop of Henle: Countercurrent Multiplier System (Ascending)
A. Permeable to water
B. Potassium is reabsorbed
C. Both
D. Neither
D. Neither (is IMPERMEABLE to water and it is SODIUM and CHLORINE that get reabsorbed)
Loop of Henle: Countercurrent Multiplier System (Descending)
A. Passive reabsorption of water
B. Active reabsorption of water
C. Both
D. Neither
A. Passive only
Tubular Secretion
A. Distal Convoluted Tubule
B. Waste product recycling
C. Both
D. Neither
A. DCT only (waste products are to be eliminated, not recirculated back to the system)