Histology Flashcards
Name 3 histological features of the Cortex and 2 for the medulla
Cortex: dark staining, many renal corpsules (blood filtering component of the nephron), and mitochondira
Medulla: Lighter staining, less biologically active and therefore less mitochondria
What are the 3 properties of renal epithelia, what holds them together and what are the 2 types?
Protective, absorptive and secretory
Held together by tight junctions (on the luminal side)
Squamous: filtration and diffusion is easy
Cuboidal: active transport
Explore the structure and function of different epithelial cells along the nephron
PCT: large cuboidal cells, brush border microvilli (many mitochondria)
LOH: squamous cells, passive flux out of water, and simple cuboidal cells which recover Na+ and Cl- via the Na+-K-+Cl- cotransporter
DCT: smaller cuboidal cells, fewer mitochondria, no microvilli
CT: cuboidal cells with few mitochondria and no microvilli
What is the purpose of the JGA and how does it perform its role?
JGA controls the GFR and stabilizes the BP: when macula densa cells sense increased sodium, they release vasoactive compounds to constrict the afferent arteriole.
A negative feedback loop: Since afferent arteriole has been constricted, the subsequently reduced amounts of Na+ and Cl- that make it to the DCT shuts off this signal/need.
What are the 2 types of cells that contain renin?
JG cells: modified sm muscle cells with renin in their zygotes granules
Lacis cells: also used for support, (pale staining), outside the glomerulus
What is meant by the vascular pole? Where does the PCT leave the corpuscle?
The afferent and efferent arterioles, the PCT leaves the corpuscle at the tubular pole
Describe the parietal and visceral layer of the glomerulus
Parietal: outer layer of the capsule simple squamous cells
Visceral: Inner layer, is the epithelial layer of the glomerulus, it has podocytes that envelop the Basement membrane of capillaries that forms filtration slits
Discuss the levels of filtration as substances move through the glomerular capillaries
- Endothelium of capillary has fenestrated pores (70-90nm) that prevents passageway of RBCs and platelets
- BM: negatively charged, repels proteins
- Filtration slits between pedicels also negatively charged, restricting passageway of small proteins and organic anions
What should happen to any proteins that are accidentally absorbed in the glomerulus?
Degraded into amino acids and reabsorbed in the PCT
Which substances are normally found in filtrate? (fluid leaving the glomerulus on its way to the PCT)
glucose, amino acids, ions, urea, hormones, vitamins and small amounts of protein
What keeps fluid in the PCT isotonic?
The glomerular filtrate has the same osmolarity as the plasma, and in the PCT water and salt are absorbed in equal amounts
Discuss the differing epithelial cells as you progress through the LOH
What is the overall function of the LOH?
Descending thick segment: simple cuboidal actively resorbs Na+
Descending thin segment: simple squamous, allows water to passively leave (due to hypertonic medullary interstitium)
Ascending thin segment: simple squamous, impermeable to water, active and passive resorption of ions
Ascending thick segment: cuboidal epithelium: lots of Na-K-Cl cotransporters to actively recover Na+ and Cl-
Overall forming concentrated urine
What is the role of aldosterone? What stimulates it?
Angiotensin II stimulates aldosterone, which stimulates Na+ and water resorption in the DCT (and K+ loss) increasing plasma volume + BP
What does PTH stimulate?
Ca2+ reabsorption in the DCT.
What is the name of the simple cuboidal cells that continue off the DCT into the CD? What do they do?
Principle cells:
Basolateral side: Na-K+ pump to resorb Na+, and bring K+ into the epithelia
Luminal: Na-K-Cl- cotransporter pumps Na+ and Cl- into the cell, and K+ into the filtrate
