16.4 Histology: Of the urinary system Flashcards
What zones is the kidney divided into?
Cortex (outer), medulla (inner)
Where do blood vessels of the kidney enter and exit?
What is at the boundary between cortex and medulla?
Enter and exit at the hilum
Arcuate vessels at the boundary
What is the nephron? What does it consist of?
Functional unit of kidney (0.3-1.5 million/kidney)
Renal corpuscle, tubule (nephron joins collecting duct in the cortex)
What are the roles of the corpuscle, the tubule and the collecting duct?
Corpuscle: filters blood
Tubule: modifies filtrate
Collecting duct: carries urine away
What are the differences in components of the cortex and medulla?
Cortex contains all of the corpuscles
What are the two types of nephron?
Juxta medullary (15%), base of cortex, loops deep into medulla
Cortical (85%), higher in cortex, tubule loops halfway into medulla
What is the glomerulus? Where does it sit?
Glomerulus is a tuft of capillaries connected to arteriole, pushes into expanded tubular end
What is Bowman’s space? What is it lined by?
A space continuous with the lumen of the tubules that doesn’t have capillaries. (the urinary space)
Lined by podocytes over capillaries, parietal cells over outer layer.
What cells support the glomerulus?
Mesangial cells (limited connective tissue)
What are the two poles of the renal corpuscle?
Vascular pole (capillaries enter)
Urinary pole (tubule drains Bowman’s space)
What is the renal corpuscle lined with?
Squamous parietal cells give way to cuboidal epithelium of tubule
What covers glomerular capillaries? What is inbetween the processes?
Podocytes, glycocalyx and slit membranes between the processes
What is the filtration barrier in the renal corpuscle? (3)
A barrier that contains slit membranes with small pores (3-5nm), a basal lamina that traps molecules (>69kD), and the fenestrated capillary that lacks diphragms
What is the role of the kidney tubule? What does this result in?
Modify ultrafiltrate, recover and secrete substances=hyperosmotic urine (rich in urea)
What does the proximal tubule do? What part is in the cortex?
Proximal tubule reabsorbs glucose, aa’s, protein
Part in cortex is convoluted tubule
What happens on the folded basal membrane of proximal tubule?
Na+/K+ ATPase pumping Na+ across cell, Cl/H2O follow, Na/Cl/H2O moves passively across apical membrane (needs ATP from mitochondria)
What is the Loop of Henle permeable to?
Urea and electrolytes, (descending limb more permeable to water)
What does the distal tubule lack?
What is it permeable/impermeable to?
How is it different to the proximal tubule?
Which part is in the cortex?
Lacks microvilli (cuboidal cells)
Impermeable to water/urea (has Cl/Na pumps)
More mitochondria than proximal tubule
Distal convoluted tubule in cortex
What makes the collecting duct permeable to water?
Antidieuretic hormone (vasporessin)
What are the juxtamedullary nephrons critical for?
Hyperosmotic urine
What do juxtaglomerular apparatus do? What do the JG cells do?
Monitor filtrate volume/Na+ concentation
Release renin (eventually AngII)
What are vasa recta? What do they do?
Capillaries from efferent arteriole that envelop tubule (crucial for urine concentration)
What does the medulla consist of?
Thick/thin loops of Henle
Collecting ducts
Capillaries of vasa recta
What is the structure of the ureter? (3)
Lined with transitional epithelium, has LP, thick muscularis of SM
