36. The Urinary System Flashcards
What comprises a renal corpuscle?
What are the ‘supporting cells’ of the renal corpuscle?
Describe the journey blood takes through the capillary from the renal artery.
What comprises a nephron?
Glomerulus (tuft of capillary loops) and Bowman’s capsule.
Mesangial cells: secrete ECM, macrophage-like activity
Renal artery -> main branch renal artery -> interlobar artery -> arcuate artery -> interlobular artery -> afferent arteriole -> renal glomerulus -> efferent arteriole -> cortical capillary plexus OR vasa recta -> interlobar vein -> return alongside renal arterial supply.
Bowman’s capsule and renal tubule. Processes blood filtrate, produces urine
What 3 things make up the glomerular filtration barrier?
What is the function of the PCT?
What does the PCT look like?
Fenestrated capillary endothelium, BM, podocyte layer of Bowman’s capsule.
Reabsoprtion - facilitated by Na+/K+ ATPase in basolateral membranes. Reabsorbs 70-80% H2O, Na+ and Cl-, 100% of AA and glucose, some bicarbonate reabsorbed/H+ secreted. Larger proteins and carbs reabsorbed via endocytosis.
Microvillus brush border, endocytotic vesicles and lysosomes (take up large carbs and proteins, contrituent parts reutilised once degraded). Simple cuboidal epithelial cells.
What is the function of the Loop of Henle?
Describe the characteristics of the sections of the LoH (epithelium type, what goes out/in).
Create and maintain high ionic concentration of medulla.
Thin segments: simple squamous epithelium, descending = permeable to urea and H2O but less permeable to NaCl; urine gains urea and loses H2O which is removed by vasa recta (countercurrent exchange). Ascending = impermeable to H2O, allows some NaCl diffusion.
Thick ascending limb: simple cuboidal epithelium actively transports Na+ (with Cl-) out of tubule without H2O. Get hypotonic urine and hypertonic conc gradient of NaCl in medulla.
What are the 2 functions of the DCT?
Describe the appearance of the DCT.
Describe the 3 components of the JGA.
1) Water balance (tubules reabsorb water in presence of ADH)
2) Electrolyte and acid-base balance - Na+ reabsorption coupled to K+ or H+ secretion under control of aldosterone
Simple cuboidal epithelium, few microvili or endocytotic vesicles, basal and lateral interdigitations reflecting ion transport requirements. Macula densa: specialised region at vascular pole of nephron, dense cell packing, part of JGA. Tubular glomerular feedback
1) JG cells: afferent arteriole senses decreases in BP and secretes renin. SM cells. Mechanosensitive too
2) Macula densa: sense decreased Na+ content of distal tubule
3) Extraglomerular mesangial cells/lacis cells: support/info transfer between MD and KG
Also sympathetic NS can stim renin secretion via B1 adrenoreceptors
Label A-D in the glomerulus
A: DCT
B: macula densa
C: extraglomerular mesangial cells
D: JG cells
What is the function of the collecting duct?
Describe the appearance of the CD.
What comprises the ‘urinary passageways’, and what kind of epithelium lines them?
Similar to DCT: final conc of urine (ADH sensitive), electrolyte and acid-base balance (aldosterone sensitive). Urea diffusion helps maintain high solute conc of medulla.
Simple cuboidal to columnar epithelium, distinct lateral membranes (few interdigitations)
Calyces, renal pelvis, ureter, bladder, urethra. Transitional urothelium - protects tissue from urine toxins
Describe the structure (layers) of the urinary passageways.
What are umbrella cells?
Mucosa: transitional urothelium, plaques (membrane folds, allows distension), tight junctions/thick imperveous cell membranes. Lamina propria but NO muscularis mucosae
Submucosa: merges with lamina propria
Muscularis: 2-3 layers of SM, innermost = longitudinal (loose spiral), then circular (tight spiral), then longitudinal (loose spiral) NB: gut innermost = circular
Adventitia: outer layer of loose CT carrying larger BV and nerves
Multinucleated superficial cell of the transitional epithelium, thin but covers multiple underlying transitional cells in a parasol-like fashion (U in pic)
Describe the bladder.
Distensible reservoir and muscular pump. Ureters enter at acute angle in posterolateral wall. Filling closes lumen (prevents backflow). Internal spincter formed by middle circular SM at neck of urethra. Micturation controlled by parasympathetic NS input.
