Renal Histology Lecture Flashcards
What is another term for the renal system?
The genitourinary system
What makes up the renal system?
2x kidney
2x ureter
1x bladder
1x urethra
How does the location of the right and left kidney vary?
What are the landmarks for this?
The reight kidney is lower than the left kidney (due to the presence of the liver above the right kidney)
The right kidney is found between T12 and L3
The left kidney is found between T11 and L2
What are the different functions of the kidney?
Regulate blood volume
Regulate concentration of Ions
Regulate pH of blood through long term balance of acids and bases
Metabolic process - regulate glucose and Vitamin D synthesis (role in blood calcium levels)
Excretion of urea, waste, toxins and bioactive substances such as drugs
Endocrine funtion - renin and EPO
Very Clever PIgeons Migrate East Easily
What is the functional unit of a kidney?
The uriniferious tubulue
Consisting of the nephron and the collecting duct
What makes up the barrier between the glomerulus and the bowmans space?
Capillary endothelium
Basement membrane
Pericytes
What is the renal sinus?
Branches of adipose tissue between the calyx system in the kidney (mainly between the minor calycx)
Roughly where in the kidney is EPO produced.
In the cortex of the kidney in the interstitial cells near the proximal convoluted tubule of the kidney.
What makes up the renal corpuscle?
The bowmans capsule
The glomerulus
What is the flow of structures in the nephron?
Renal corpuscle - glomerulus
Proximal convoluted tubule
Thick descending segment of the PCT
Thin descending segment of the loop of henle
Thick ascending segment of the loop of henle
Thick ascending segment of the DCT
Distal convoluted tubules
Connecting tubulue
Collecting duct
What is important to note about the position of the macula densa cells?
Located in the DCT - are identifiable are simple columnar rather than simple cuboidal.
In the DCT closest to opposite to the tubular pole
What is the cell type of the proximal convoluted tubule?
Simple cuboidal with microvilli
What is the cell type of the DCT?
Simple cuboidal without microvilli
What is the cell type of the thin descending limb of the loop of henle?
SImple sqaoumous
What is the cell type of the thick ascending limb loop of henle?
Simple cuboidal
What is the cell type of the collecting tubule?
Simple cuboidal to columnar
What features of the PCT adapt it to absorption?
Microvilli brush border + large surface area
Lots of mitochondria
What are the two different types of nephrons based on their location in the kidney?
The cortical nephrons - PCT/DCT/G located in cortex, long loop of henle dippping down into medullar
The juxtamedullary nephron - near the junction of the cortex and the medulla, shorter loop of henle dipping down into the medulla
What are the different poles of the glomerulus?
The tubular pole - where filtrate leaves to enter PCT
The vascular pole - where the afferent and efferent arteriole are.
What is the cell type of bowmans capsule?
Simple sqaoumous
What are the two difference layers of the bowmans capsule?
The visceral layer - podocytes fused to the basement mebrane of the glomerular capillaries
The parietal layer - the simple sqaoumous cells with an outer basal lamina
The visceral and parietal layer are seperated by bowmans space
What are the key features of podocytes, how does this contribute to filtration?
Pododcyts have a cell body
Then primary processes (big arm)
THen secondary processes (fingers)
Between the seconadry processes are filtration slits
These allow some substances to pass through but are a barrier to small protein.
What are pedicles in relation to the glomerurulus?
Secondary processes of podocytes
What are filtration slit diaphragms?
The space between podocyte pedicles in the glomerulus filtration barrier.
What is a key way to distinguish between the PCT and DCT on a histological image?
The PCT stains darker and cells are larger
The DCT has a larger lumen
The DCT has a more prominent nucleus
How is the CT distinguished from the PCT and the DCT on a histological image?
Is typically larger with a bigger lumen
Cells are more columnar is shape
Cells are lighter in stain
The cell membranes are easier to distinguish apart from the rest of the cell.
What is the role of ADH in relation to the nephron?
ADH is secreted by the posterior pituitary gland
Increases permeability of the CD to water by inserting aquaporins in the apical membrane this increases water reabsoprtion.
How are macula densa cells identified on a histological image?
Are located in the wall of a DCT
Are typically darker stained, in a thicker ridge as close proximity to juxtaglomerula cells
Are in close proximity to the bowmans capsule
What makes up the juxtaglomerular apparatus?
Where is it located?
Made of macula densa cells in the wall of the DCT and juxtaglomerular cells surrounding the afferent and efferent arteriole around the macula densa
Found at the vascular pole
What is the function of the juxtaglomerular cells?
Macula densa cellls - monitor sodium levels in the nephron
Juxtaglomerular cells - modified smooth muscle cells, release renin to regulate blood pressure when stimulated.
What triggers renin release in the kidney?
Low renal perfusion
Often low blood pressure = low sodium levels
Detected by Macula densa cells (osmoreceptor)
Activates juxtaglomerula cells
What is the role of aldosterone in blood pressure regulation in the kidney?
Angiotensin 2 bind to AT receptors in the renal medulla causing aldosterone release.
Aldosterone acts on the collecting ducts and DCT to increase ENaC activity to increase sodium ion reabsoprtion hence water reabsoprtion.
What structure are the juxtaglomerular cell a part of?
Specialised part of smooth muscle of the afferent arteriole
What are the key features you may be able to identify in a cross section of a kidney medulla?
A thick ascedning limb of loop of henle
A thin descending limb of loop of henle
INterstitial cells
Collecting ducts
Vasa Recta
How can vasa recta and interstitial cells be indentified on a histological cross-section of a renal medulla?
Interstitial cells - visible nuclei, in connective tissue, no associated lumen
Vas recta - very small lumen, may be able to identify rbcs in the lumen
How can you distinguish between the thin LOH, thick LOH and the collecting ducts in a cross section of the renal medulla?
CD - simple columnar, widest dimateri
thin and thick LOH - compare thickness of lumen walls, thick is generally darker stained aswell.
What are the three layers of the ureter?
The mucosa (epithelium and lamina propria)
The muscularis externa
Serosa
How is the muscle in the ureter muscularis externa arranged?
Inner longitudinal
Outer circular
Near the bladder contains an additional outer longitudinal - this layer is present in the bladder.
What are the key features of the ureter epithelium?
Is a transitional epithelium (domed when empty- not distened, changes to flat when distended)
Consists of a surface cuboidal (changing) layer followed polyhedral cells then simple sqaoumous cells
Undistended lumen epithelium folds into longitudinal mucosal folds
What are some features of the lamina propia of the ureter?
Is very thick
Has fibroblast in higher concentration and more dense tissue under the epithelium
Then decreases fibroblasts and less dense before the muscularis externa
What is found in the tissue surrounding the ureter?
Is mainly made of adipose tissue
Contains numerous arterioles, venuoles and innervation
How is urine transported down the ureter?
By peristalsis
Due to smooth muscle content
What are the key histological features of the urinary bladder?
Has a transitional epithelium
Well vascularised lamina propia
Has three layers to the muscularis externa (inner longitudinal, middle circular and outer longitudinal) - very thick wall.
Serosa/adventita
How does the outer layer of the urinary bladder vary depedning on where in the bladder the section is taken from?
Superior bladder = serosa
Inferior bladder = adventitia as no longer covered by peritoneum.
What are the differences histologically between the ureter and the bladder?
Bladder - thicker epithelium, lamina propia and muscularis externa
Proptionally the bladder has a thicker muscular wall.
Bladder contains more elastic than the ureter.
Bladder has mucosal folds
What is the purpose of the mesothelium in the bladder?
Is an outer covering of the bladder
Is highly specialised to protect the underlying tissue from mechanical stress and seperate them from the overlying fluid space.
What are the medullary rays?
The straight parts of the the loop of henle, the thick descending PCT and thick ascending DCT and the straight portion of the collecting ducts, just superior to the medullar travelling into the cortex
Identify the PCT DCT CD and renal corpuscle on this image
Identify the features of this image.
Proximal convoluted tubule
Macula densa
Distal convoluted tubule
Glomerulus
Bowman’s space
Parietal layer of bowman’s capsule
Differentiate between the proximal and distal convoluted tubules
What do the arrows yellow/black represent.
1 distal convoluted tubule clearer nucleus, more white lumen
2 proximal convoluted tubule brush border gives a fluffy appearance
Yellow arrows are venules
Identify the features of the renal medulla
1 vasarecta
2 collecting duct
3 interstitial cells lilkey a fibroblast nuclei
4 thick al of lop
5 think dl of lop
Identify the key features in the image of the ureter
Identify the features of the urinary bladder
5 and 6 are of minor importance
What is the most distal part of the collecting duct?
Papillary duct
Label the key features of the kidney
Label the image
Identify the renal pyramid
Renal column
Renal sinus
Calyx
Label the key arteries of the kidney
Identify the highlighted features
Green = pct
Blue = juxtaglomerular apparatus
Yellow = DCT
Red = collecting tubule
Identify the pct DCT and CT
Identify the thin limbs, thick limbs, collecting ducts and vasa recta
Collecting ducts have clearer cell membranes
Identify the DCT efferent arteriolar and juxtaglomerular apparatus
