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
How are the a-intercalated cells and the principle cells related?
What happens at this stage to the HCO3 that is metabolically created?
They use the K+ pumped out by the Na-Cl-K+ pump in the principle cells for energy to pump K+ back into the cell and secrete H+ into the filtrate.
The HCO3 can be in these cells: CO2 released from metabolism + H20 H+ and HCO3-, the HCO3- can then pass through the basolateral membrane into the blood
What is a histological difference between the CT and the LOH?
The CT lumen is larger and more irregular
What stimulates ADH? What 2 things does it do and what is it’s overall job?
The hypothalamus triggers thirst and ADH release from the posterior pituitary: (ADH is a neurotransmitter)
- Mainly, this stimulates aquaporins to form on the basolateral membrane on the DCT and CT to allow more resorption of water
- Stimulates vasoconstriction in blood vessels
Main job: increase BP!
What is unique about the production, storage and travelling of ADH?
Produced: hypothalamus
Stored: posterior pituitary
Travels: through the neuroendocrine system, going down axons and released as a neurotransmitter (aka, not through bloodstream)
What’s the other name for ADH?
Vasopressin
What buffers the H+ in the filtrate?
H+ can join onto phosphate or ammonia and then be excreted.
What are the 3 layers of the ureters?
- Mucosa: lined with transitional epithelium
- Circular and longitudinal layers of muscularis externa, peristalsis conveys urine towards the bladder
- Adventitia
What are umbrella cells?
The outer layer, have lipid rafts in their membranes and plaques containing uroplakins (protective protein). When the rafts unfold, the SA increases
What is the function of transitional cells and where are they found?
Distension, protects tissues from urine. Found in renal calyces, pelvis, ureter, bladder and proximal urethra
What type of tissue surrounds the bladder?
Serosa superiorly, and the remainder is surrounded by adventitia
How many layers are there in the detrusor muscle?
How much can the bladder hold?
3 layers.
The bladder can hold up to 600 mL for 5 hours, then a sharp rise in pressure will give the urge to urinate
What type of epithelia lines the different regions of the male urethra?
Prostatic urethra: urothelium
Membranous urethra: stratified and pseudostratified columnar
Spongy: stratified squamous
What type of epithelia is present in the female urethra?
Proximally: transitional
Changes to stratified squamous
