Histology Flashcards
Describe the appearance of the cortex and medulla
Cortex: dark, renal corpuscles and mitochondria
Medulla: Lighter, less biologically active - less mitochondria
What are the properties of renal epithelia, what holds them together and what are the 2 types?
Protective, absorptive and secretory
*tight junctions on luminal side
Squamous: filtration and diffusion
Cuboidal: active transport
Explore the structure and function of different epithelial cells along the nephron
PCT: large cuboidal cells (active transport), microvilli
LOH:
- Thick segments (upper): cuboidal (resorbing sodium, Na-K-Cl co transporter)
- Thin segments (lower): squamous (passive water outflux)
DCT and CT: cuboidal cells (few mitochondria, no microvilli)
What is the purpose of the JGA and where is it? and how does it perform its role?
Thickened region of ductal epithelia where DCT passes close to glomerulus
Macula densa cells sense increase sodium -> vasoactive compounds -> constrict around afferent -> reduces GFR ->
-> less Na and Cl makes it to DCT -> Shuts off macula
What are the 2 types of cells that contain renin?
JG cells: modified sm muscle cells (renin in their zygotes granules)
Lacis cells: support, (pale), outside the glomerulus
What is meant by the vascular pole? Where does the PCT leave the corpuscle?
The afferent and efferent arterioles
PCT leaves corpuscle at the tubular pole
Describe the parietal and visceral layer of the glomerulus
Parietal: simple squamous cells
Visceral: podocytes - processes extend to form pedicles that envelop BM of capillaries, between pedicles are filtration slits
Discuss the levels of filtration as substances move through the glomerular capillaries
- Capillary endothelia: fenestrations prevent RBCs and platelets
- BM: negatively charged, repels proteins
- Filtration slits between pedicels, -ve to restrict passage of small proteins and organic anions
- > Bowman’s space -> PCT
What should happen to any proteins that are accidentally absorbed in the glomerulus?
Degraded into amino acids and resorbed in PCT
What keeps fluid in the PCT isotonic?
Glomerular filtrate has same osmolarity as plasma
Water and salt are absorbed into the PCT in equal amounts
Discuss the differing epithelial cells as you progress through the LOH
What is the overall function of the LOH?
Descending thick: simple cuboidal actively resorbs Na+
Descending thin: simple squamous, water passively leaves (hypertonic medullary interstitium)
Ascending thin: simple squamous, IMPERMEABLE to water, active and passive reabsorption of ions
Ascending thick: cuboidal epithelium: lots of Na-K-Cl cotransporters to actively recover Na+ and Cl
-> dilute urine?
What is the role of aldosterone? What stimulates it?
Angiotensin II -> aldosterone -> Na+ and water reabsorption in DCT (and K+ loss)
What does PTH stimulate?
Ca2+ reabsorption in the DCT.
What is a histological difference between the CT and the LOH?
The CT lumen is larger and more irregular
What’s the other name for ADH?
Vasopressin
What buffers the H+ in the filtrate?
H+ joins phosphate or ammonia and is excreted.
What are the 3 layers of the ureters?
- Mucosa: transitional epithelium
- Circular,longitudinal layers of muscularis externa
- Adventitia
What are umbrella cells?
Outer layer, lipid rafts in membranes and plaques containing uroplakins (protective protein).
Rafts unfold -> SA increases
What is the function of transitional cells and where are they found?
Distension, protects tissues from urine.
Renal calyces -> proximal urethra
What type of tissue surrounds the bladder?
Serosa superiorly, adventitia the rest
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?
Transitional -> stratified squamous
