Urinary System (Notes) Flashcards
What are the three functions of the Urinary System?
Excretion
Elimination
Homeostatic Regulation
How much do the kidneys filter per hour?
200 Liters
What are the three layers of the kidney?
- Renal fascia
- Perirenal fat capsule (adipose)
- Fibrous capsule (renal capsule)
What is the function of the perirenal fat capsule?
To cushion the kidney and hold it in its position.
What is pyelitis?
Infection of renal pelvis and calyces.
What is pyelonephritis?
Inflammation/Infection of the entire kidney.
What is the main function of the kidney?
Filtration.
What are the arteries involved in renal blood circulation?
Renal Art-Segmental arts-Interlobar arts-Arcuate arts-corical radiate arts-afferent arterioles-glomerulus-efferent arterioles
What are the veins involved in renal blood circulation?
Peritubular capillaries-Vasa Recta-venules-cortical radiate veins-arcuate veins-interlobar veins-renal vein
What is the fibrous capsule (renal capsule) composed of?
Dense Irregular Connective Tissue
What is the renal fascia composed of?
Dense Fibrous Irregular Connective Tissue
What is the purpose of the fibrous (renal) capsule?
To prevent spread of infection to kidneys.
What is renal ptosis (nephroptosis)?
“Floating Kidneys.” Kidneys drop to a lower position.
What are potential causes of renal ptosis (nephroptosis)?
Rapid weight loss, some degree of weakening of fibrous bands (10x more common in women).
What is hydronephrosis?
Urine backup. Can be from ureter blockage or something else. This can cause severe damage!
What are renal calculi?
Kidney stones.
What are renal calculi composed of?
Crystallized calcium, magnesium, or uric acid salts.
What are potential causes of renal calculi?
- Chronic bacterial infections
- Urine retention
- Increased Ca2+ in blood
- Increased pH of urine
Where is the nerve supply for kidneys?
Hilum of kidney, via sympathetic fibers from renal plexus.
What are the two layers of the glomerular (bowman’s) capsule?
Parietal layer and visceral layer.
What makes up the parietal layer of Bowman’s capsule?
Simple squamous epithelium.
What is the purpose of the parietal layer of Bowman’s?
To act as a cup, enclosing everything.
What makes up the visceral layer of Bowman’s?
Podocytes
What type of tissue are podocytes composed of?
Modified simple squamous epithelium
What are the feet of podocytes called?
Pedicels
What segment is the descending limb of the nephron loop?
Thin segment made of simple squamous epithelial
What segment is the ascending limb of the nephron loop?
Thick segment made of simple cuboidal epithelial, also thin segment (simple squamous)
Where does most reabsorption occur?
Proximal Convoluted Tubule (PCT)
What does the PCT reabsorb?
Amino acids, glucose, vitamins, some electrolytes
What is secreted into the PCT?
Drug metabolites, waste, etc.
Where is the site of H20 reabsorption?
Descending limb of loop of Henli (Nephron loop)
Where is the site of reabsorption of ions?
Ascending limb of nephron loop
What are the two ccell types in the collecting duct?
Principle Cells and Intercalated Cells
What type of tissue makes up the PCT?
Simple cuboidal w/ dense microvilli with a brush border
What type of tissue makes up the DCT?
Simple cuboidal w/ few microvilli
What are the two major groups of nephrons?
Juxtamedullary and Cortical
How many of the nephrons are cortical, how many are juxtamedullary?
85% cortical nephrons
15% juxtamedullary nephrons
What is the function of juxtameduallary nephrons?
Control concentration of urine
What is the significance of the depth of the Nephron loop?
The deeper the loop goes, the greater the ability to concentrate the urine.
What are the four cells in the juxtamedullary apparatus (complex)?
- Macula Densa
- Juxtaglomerular Cells/Granular Cells
- Extraglomerular Mesangial Cells
- Glomerular Mesangial Cells
What are macula densa?
Cells in JGA/JGC which contain chemo and osmoreceptors that sense NaCl content (solute content) of filtrate
What are juxtaglomerular (granular) cells?
Cells in afferent arteriole which act as mechanoreceptors to sense BP. They have secretory granules which contain renin.
What are extraglomerular mesangial cells?
Cells which are loaded with gap junctions. These cells act as a bridge to pass signals between macula densa and granular cells.
What are glomerular mesangial cells?
Cells which contain actin. When these cells contract, they reduce surface area of glomerular capsule.
What are the three layers of the ureter wall and what is each layer composed of?
- Mucosa-transitional epithelium (has goblet cells)
- Muscularis-smooth muscle sheets which contract
- Adventitia-fibrous connective tissue for support
How much can a moderately full bladder hold?
500 ml
What kind of muscle is the internal urethral sphinctor?
Smooth muscle
What kind of muscle is the external urethral sphinctor?
Skeletal
What needs to happen to the internal and external sphinctors, and the detrusor muscle in order to pee?
Both internal and external urethral sphinctors must relax, and detrusor must contract.
How much do the kidneys process daily?
180 L
How much of the body’s oxygen do the kidneys use at rest?
20-25%
What happens in glomerular filtration?
It produces cell-free and large to medium sized protein-free filtrate
What happens in tubular reabsorption?
Selectively returns 99% of substances to blood in renal tubules and collecting ducts
What happens in tubular secretion?
Selectively moves substances from blood to filtrate in renal tubules and collecting ducts
What is outward pressure?
Forces that PROMOTE filtrate formation
What is glomerular blood hydrostatic pressure (GBHP)?
Chief force pushing H20 and solutes out of blood (55 mmHg)
What are inward pressures?
Forces that inhibit filtrate formation.
What is capsular hydrostatic pressure (CHP)?
Filtrate pressure in the capsule (15 mmHg)
What is Blood colloid osmotic pressure (BCOP)?
The pull of proteins in blood (30 mmHg)
How do you find Net Filtration Pressure?
GBHP - (CHP + BCOP) = NFP
What does it mean if the NFP is positive?
Filtration is occuring
What does it mean if the NFP is negative?
Reabsorption is occuring
What is the NFP equal to?
The Glomerular Filtration Rate (GFR)
What does the Intrinsic branch control?
80-180 mmHg blood pressure.
What does the Extrinsic branch control?
Anything under 80 mmHg and anything over 180 mmHg
What are the two types of autoregulation?
Myogenic Mechanism and Tubuloglomerular Feedback Mechanism.
What happens if there is an increase in MAP?
Myogenic mechanism takes place. Afferent arteriales constrict.
What if there is a decrease in MAP?
Myogenic mechanism takes place. Dilation of afferent arterioles.
What is the tubuloglomerular feedback mechanism dependent upon?
Flow, directed by macula densa cells of JGC/JGA.
Which is the slow acting branch of renal autoregulation?
Tubuloglomerular feedback mechanism
Which is the fast acting branch of renal autregulation?
Myogenic feedback mechanism
What does the tubuloglomerular feedback mechanism respond to?
Filtrate’s NaCl concentration (filtrate’s osmolarity), and/or flow of filtrate in renal tubules
What is the purpose of extrinsic controls?
To regulate GFR to maintain systemic BP
True or False: Extrinsic controls override renal intrinsic controls if blood volume needs to be increased.
True.
What do Norephinephrine and Epinephrine cause in the kidneys?
Systemic vasoconstriction of renal blood vessels
Strong constriction of afferent arterioles
What is ANP (Atrial Natriuretic Peptide)?
Hormone released by atria when blood pressure increases or blood volume increases
What does Atrial Natriuretic Peptide (ANP) do?
Causes relaxation of glomerular mesangial cells, increasing capillary surface area, increasing GFR
What is RAAS (Renin-Angiotensin-Aldosterone-System)?
When blood pressure/blood volume decreases, this is the main mechanism for increasing BP/Blood Volume
What are the three pathways to renin release by Granular cells?
- Direct stimulation of granular cells by sympathetic nervous system
- Stimulation by activated macula densa cells when filtrate NaCl concentration is low
- Reduced stretch of granular cells
What is anuria, and what measurements decide if you have anuria?
Abnormally low urine output.
Less than 50 mL per day
What can anuria be an indicator of?
Glomerular blood pressure is too low to cause filtration
What can renal failure and anuria be results of?
Situations in which the nephrons stop functioning, like acute nephritis, transfusion reactions, and crush injuries
What are the two routes for tubular reabsorption?
- Transcellular route (transcellular reabsorption)
2. Paracellular route (paracellular reabsorption)
How does transcellular reabsorption work?
Solute enters apical membrane of tubule cells
travels through cytosol of tubule cells
exits basolateral membrane of tubule cells
enters blood through endothelium of peritubular capillaries
How does paratubular reabsorption work?
travels between the tubule cells
What is paratubular reabsorption limited by?
Tight junctions, leaky in PCT
What does ADH do?
Increase water reabsorption.
Increases the number of sodium-chloride-potassium symporters
Increases the activity of the sodium potassium pump
Makes aquaporins in principal cells
Where is ADH active?
Ascending limb, late DCT, collecting duct
What does aldosterone do?
Increase BP and decrease potassium levels
Makes symporters, increases number of potassium symporters, increase activity of sodium-potassium pump, increased chloride channels
