E3: Urinary Flashcards
What are the components of the Urinary system?
2 kidneys
2 ureters
Bladder
Urethra
What are the functions of the urinary system?
Functions:
- Blood filtration: Removal of toxic waste
- Protein metabolism (urea), some drugs
- Water-electrolyte balance: Na+, K+, Ca2+
- Acid-base balance (pH): H+ and HC03-
- BP control: Renin-angiotensin system
- RBC production during hypoxia
- Vitamin D synthesis
Describe the basic anatomy of the Kidney
Renal Anatomy & Function:
Cortex: Initial Filtration
Medulla: Modification of Filtrate
Renal pelvis/Ureter: Drainage of Urine
What is the pathway of Urine flow?
What about blood flow?
Urine flow:
Cortex > Medulla > Papilla > Calyces > Pelvis > Ureter
Blood flow:
Renal artery > Cortex > Medulla > Renal vein
ID the tissue in the image.
What does it primarily consist of?
Renal Cortex
Primarily consists of PCT’s & DCT’s
What is the functional unit of the Kidney?
What is the composition?
Functional Unit: The Nephron
Components:
1. Renal corpuscle (filter)
- Glomerulus + capsule
2. The renal tubules:
- Tubules specialized for absorption/secretion
- PCT, loop of Henle, DCT
3. Collecting ducts
The Renal Corpuscle is composed of what?
Describe it’s formation
Renal Corpuscle = Glomerulus & Capsule
Glomerulus Formation:
- Renal artery splits into numerous arterioles
- Each afferent arteriole splits into fenestrated capillaries, which form a knot (the glomerulus)
* Blood leaves via the efferent arteriole
Capsule Formation:
- Developing renal tubule wraps around the glomerulus, forming Bowman’s capsule
- Visceral layer: Lines glomerular capillaries
- Podocyte Layer
- Parietal layer: Lines the capsule wall
- Visceral layer: Lines glomerular capillaries
What are the (3) layers of filtration?
(3) Layers of Filtration:
- Capillary Epithelium (fenestrated)
- Glomerular BM
- Podocyte Foot processes (epithelial cells of the capsule)
Describe what ultrafiltration is
What molecules can pass through?
Which can’t?
What factors influence permeability?
Ultrafiltration:
Glomerulus: a molecular sieve
- Small molecules can pass
- Glucose, Na+, K+, H+, Cl-, HC03-
- Large molecules stay in plasma
- RBCs, large proteins
Factors that influence permeability:
- Hydrostatic pressure of blood
- Opposed by osmotic pressure of albumin and other plasma proteins
- Size: very little protein can cross
- Charge: (BM is negative)
What are podocytes?
What role do they play in Ultrafiltration?
Podocytes
- Pedicels (Foot processes) wrap around Endothelial cells
- Filtration slits
- Gap bridged by a slit-diaphragm
ID the tissue in this image
Renal Cortex
What are Mesangial cells?
What are their function?
Glomerular mesangial cells
- Located between the capillaries
- Analogous to Pericytes within vasculature
Function:
- Support
- Contractile
- Similar to pericytes in vessels
- Regulate glomerular flow
Where does the majority of reabsorption occur?
What are the methods of reabsorption?
Proximal Convoluted Tubules (PCT):
- Cuboidal epithelium with brush border (microvilli)
- Reabsorbs 80% of filtrate to tissue fluid
- Diffuses into surrounding capillaries
Methods of reabsorption:
- Active transport:
- Glucose
- Amino acids
- Vitamins
- Electrolytes
- Osmosis: water
Some Urea is reabsorbed into the blood stream via diffusion @ PCT
Where does Vitamin D metabolism & conversion occur?
What is the signal pathway associated with it and what is the net effect?
Proximal Convoluted Tubule:
- Brush border contains vitD receptors
- Activation triggers hydroxylase synthesis
- Converts dietary/dermal vit D to active form
VitD functions to Increase Ca2+ absorption from gut
How does the kidney regulate blood oxygen content?
Renal Cortex:
Hypoxia (Low O2 levels)
> Triggers peritubular fibroblasts in the cortex to synthesize erythropoietin (Epo)
> Epo acts on the BM to increase RBC production