Lecture #30: Renal Histology Flashcards
What is the functional unit of the kidney?
Nephron
Approximately how many nephrons are there per kidney?
1 million
What are the two different types of nephrons?
> Cortical Nephron
> Juxtamedullary Nephron
What do the glomeruli of cortical nephrons empty into?
Peritubular capillary networks that surround the proximal and distal convoluted tubules of their own nephrons and those of surrounding nephrons.
What do the glomeruli from juxtamedullary nephrons empty into?
Vasa recta consisting of long, straight arterioles and venules that run parallel to the loops of Henle and collecting ducts.
True or False:
Juxtamedullary nephrons have long loops of Henle that extend deeply into the medulla.
True
True or False:
Cortical nephrons have long loops of Henle that do not extend deeply into the medulla.
False -> Cortical nephrons have SHORT loops of Henle that do not extend deeply into the medulla.
True or False:
The renal corpuscles of both juxtamedullary and cortical nephrons are located in the cortex of the kidney.
True
*but the juxtamedullary nephrons are in the cortex next to the cortical-medullary junction (hence the name).
Starting at the renal artery and ending at the renal vein, list out the sequence of vessels in which blood flow through the kidney.
renal artery ->
interlobar arteries ->
arcuate arteries ->
interlobular arteries ->
afferent arterioles -> Glomeruli -> efferent arterioles ->
vasa recta or peritubular capillaries ->
interlobular veins ->
arcuate veins ->
interlobar veins ->
renal vein
What are the two different routes that an efferent arteriole can feed into?
> a capillary loop, the vasa recta
> a capillary network, the peritubular capillaries
What are juxtaglomerular cells? Also, what do they secrete?
Circular smooth muscle cells located at the vascular pole.
They secrete renin (hypertensive factor)
What makes up the glomerulus?
Afferent arteriole
Glomerular formation of capillaries
Efferent arteriole
What are the 2 layers of the Bowman’s capsule?
1) Parietal layer
2) Visceral layer
What epithelium lines the parietal layer, and what epithelium is this continuous with?
Parietal layer is the outer layer of the Bowman’s capsule and is simple squamous epithelium.
The squamous epithelium is continuous with the simple cuboidal epithelium of the proximal convoluted tubule.
What is the visceral layer of the Bowman’s capsule?
This is the inner layer of podocytes in contact with the endothelium of the glomerular capillaries.
Is the visceral layer or the parietal layer the outer layer of the Bowman’s capsule?
Parietal Layer is the outer layer.
True or False:
The visceral layer is the inner layer of the Bowman’s capsule of podocytes in contact with the endothelium of the glomerular capillaries.
True
Where is the Bowman’s space located?
Bowman’s space is located between the parietal and visceral layers and is continuous with the lumen of the proximal convoluted tubule.
What is the difference between the function of the renal corpuscle and the rest of the nephron, including the convoluted portions and the loop of Henle, as well as the collecting tubules?
Renal Corpuscle -> involved in producing a filtrate of blood.
The Rest -> involved in modifying the filtrate.
What 3 processes are involved in the formation of urine?
Filtration (occurring in renal corpuscle)
Reabsorption (occurring in renal tubule)
Secretion (occurring in renal tubule)
True or False:
The mesangium is part of the glomerulus.
True
Where are intraglomerular mesangial cells located?
Between nearby capillaries in the glomerulus and cover endothelium not covered by podocytes.
Where are extraglomerular mesangial cells located?
Between the afferent and efferent arterioles at the vascular pole and are associated with the juxtaglomerular apparatus.
True or False:
The mesangium is formed by mesangial cells embedded in a mesangial matrix.
True
What are the characteristics and functions of mesangial cells?
> contractile: utilize cytoskeletal contractile proteins to modify blood flow through glomerular capillaries
> phagocytic: take up worn out glomerular basal lamina for recycling and also phagocytose immunoglobulins trapped in the basal lamina
> proliferative
> synthesize matrix and collagen
> secrete prostaglandins and endothelins
> respond to angiotensin II
> provide mechanical support and regulate blood flow
Look at figure 14-6 and figure 14-9 in the lecture.
Specifically at the macula densa and mesangial structures.
What does the urinary system consist of?
> 2 Kidneys
2 Ureters
Urinary Bladder
Urethra
What makes up the juxtaglomerular apparatus?
> macula densa
> extraglomerular mesangial cells
> juxtaglomerular cells
What is the macula densa formed by?
Formed by elongated, densely packed cells in the wall of the convoluted tubule.
- polarity of these cells is reversed.
Made does the macula densa function to do?
> responds to changes in sodium and chloride concentration in the urine or hypotenssin.
> signals renin release from juxtaglomerular cells
> involved in regulation of fluid-electrolyte balance and blood pressure regulation.
What are juxtaglomerular cells? Also, what do they secrete, what are they stimulated by, and what are they innervated by?
Modified smooth muscle cells associated with macula densa and afferent arterioles.
Secrete -> renin
Stimulated by -> macula densa
Innervated by -> sympathetic nerve endings, which increase renin release.
What are the components of the renal filtration barrier?
> fenestrated endothelium of glomerular capillaries
> fused basal laminae of endothelial cells and podocytes
> filtration slits
What is the selectivity of the renal filtration barrier?
> water, glucose, and most ions pass through filter into Bowman’s space
> proteins are typically excluded from passing across the filter
> molecules with a large negative charge are excluded
What are the filtration slits of the renal filtration barrier?
> fenestrated endothelium of capillaries
basal lamina:
- contains type IV collagen, fibronectin, laminin, heparin sulfate
filtration slits created by adjacent pedicels of podocytes:
- covered by filtration slit diaphragm
- pedicels are attached to basal lamina via alpha3beta1 integrins
What are the functions of the proximal convoluted tubule?
> reabsorbs most of the filtrate, including water
> removes essentially all the glucose and amino acids from the filtrate
> reabsorbs most of the sodium and chloride ions
> characterized by a complex set of transporters, co-transporters, channels, and exchangers
Describe the histology of the proximal convoluted tubule and the specifics of the cells that make up the tubular wall.
> extends from the urinary pole of the renal corpuscle to the beginning of the loop of Henle.
> Characteristics:
- simple cuboidal epithelium made up of truncated pyramidal cells
- apical (facing lumen of tubule) tight junctions and brush border - basolateral infoldings and interdigitations - basal striations with abundant mitochondria (for active transport across basal membrane) - large, pale-staining nuclei - eosinophilic cytoplasm
