Urinary Flashcards
Q1: Why does the cortex generally appear darker compared to the medulla of the kidney (in a fresh specimen)?
90-95% of the blood flow through the kidneys is through the cortex compared to
the medulla.
Q2: Describe to your tablemates how you would distinguish the histological cortex from the medulla.
To find the “histological “ cortex, I would look for renal corpuscles. To complicate matters, the cortex containing renal corpuscles protrudes between the medullary pyramids. This layer containing medullary pyramids and renal corpuscles are anatomically termed as medulla.
Q3: Describe the general structure of the kidney. Include: cortex, medulla, renal pyramids, columns, papillae, calyces pelvis and ureter.
The kidney is composed of lobes, which are composed of lobules. A lobe contains a renal pyramid and associated cortex plus ½ of the renal column on either side of the renal pyramid. Each renal pyramid empties into a minor calyx which empty into a major calyx, which empties into the renal pelvis that continues as the ureter. See lecture slides 9-17.
Q4: What is the functional significance of a brush border in the proximal tubule? What organelle is abundant in the basal domain of these cells?
Microvilli maximize absorption. Absorption is driven indirectly by the high permeability of the apical surface to extracellular Na+. Intracellular Na+ equilibrium is maintained by Na/K-ATPase which pumps Na+ out from the cells of the proximal tubule. This requires ATP produced by mitochondria. The basal domains of these cells are rich in mitochondria, a characteristic of ion transporting epithelial cells.
Q5: Describe the endocrine functions of the kidney.
- Renin-angiotensin-aldosterone mechanism
- Synthesis & secretion of erythropoietin
- Hydroxylation of 25-OH vitamin D3
Q7: What is the function of the mesangium?
1 Structural support for glomerular capillaries
2 Phagocytosis – to keep GBM clean
3 Proliferate in certain kidney diseases – therefore may serve as an indicator of pathological conditions
4 Secretes molecules in reponse to glomerular injury
Q8: What structures are included in the juxtaglomerular apparatus and what is its function?
- Macula densa
- Juxtaglomerular cells
- Extraglomerular (lacis) mesangila cells
Q9: Describe the renin-angiotensin-aldosterone system and relate it to hypertension.
The juxta-glomerular cells in the kidney release renin in response to a decrease in blood pressure or a low blood sodium level. Circulating renin catalyzes the conversion of circulating angiotensinogen to angiotensin I, which in turn is converted by angiotensin-converting enzyme (ACE) to angiotensin II. Angiotensin II then stimulates the cells of the zona glomerulosa to secrete aldosterone. As the blood pressure, sodium concentration, and blood volume increase in response to aldosterone, the release of renin from the juxtaglomerular cells is inhibited. Drugs that inhibit ACE are effective in the treatment of chronic essential hypertension which is believed to be due to excessive production of angiotensin II.
Q10: Describe to your tablemates how you would distinguish [histologically] proximal convoluted tubules from distal convoluted tubules from collecting tubules.
In a slide of the DCTs, PCTs and CTs in cross section one should look for the following distinguishing characteristics of each:
DCT: NO brush border, clean/white lumen
PCT: Brush border, star-like lumen
CT: Clear cellular boundaries
Q11: Describe the blood supply to the kidney.
The kidneys receive blood from the renal arteries, which branch directly from the abdominal aorta. Each renal artery branches into segmental arteries, dividing further into interlobar arteries which penetrate the renal capsule and extend through the renal columns between the renal pyramids. The interlobar arteries then supply blood to the arcuate arteries that run through the boundary of the cortex and the medulla. Each arcuate artery supplies several interlobular arteries that feed into the afferent arterioles that supply the glomeruli.
After filtration occurs the blood moves through a small network of venules that converge into interlobular veins. These veins follow the same pattern; the interlobular provide blood to the arcuate veins then back to the interlobar veins which come to form the renal vein exiting the
Q13: List the features of transitional epithelium which will help you distinguish it from the different ‘stratified’ tissues previously discussed and seen.
Should be able to see a scalloped or mushroom shaped luminal surface to the transitional epithelium. You should also see large round, perhaps binucleated cells in transitional epithelium, whereas the stratified squamous should have flattened nuclei in the luminal layer of cells.
Q14: How many layers of smooth muscle can you identify?
Some specimens display an inner longitudinal, middle circular, and an outer longitudinal layer or mixed layer.
