2. Functional Histology of the Urinary Tract Flashcards
What is the gross anatomy of the kidney?
It is surrounded by a fibrous capsule and is organised into two layers - the outer cortex and inner medulla.
What does the renal cortex contain?
Renal corpuscles and medulla tubules.
What is the renal blood supply?
From the renal artery which is a branch off the abdominal aorta.
What are the main components of the nephron?
Renal corpuscle (glomerulus and Bowman’s capsule), proximal convoluted tubule, loop of Henle, and distal convoluted tubule.
What are the two poles of the renal corpuscle?
Vascular pole and urinary pole.
What is the vascular pole of the renal corpuscle?
Afferent/efferent arterioles, glomerulus.
What is the urinary pole of the renal corpuscle?
Bowman’s capsule.
What is the renal tubule derived from?
Ureteric bud.
Briefly, describe how the Bowman’s capsule develops.
Renal tubule derived from ureteric bud which envelops the growing glomerulus, resulting in a double-layered cover - Bowman’s capsule.
What makes up the filtration barrier in the kidney?
Capillary endothelium, visceral layer of Bowman’s capsule - podocytes.
What makes the capillary endothelium in the kidneys so leaky?
They are fenestrated and the podocytes invest in it, making filtration slits.
What does the parietal layer of the Bowman’s capsule make up?
A funnel to collect ultrafiltrate to drain into the PCT and urinary pole.
Where does reabsorption begin in the kidneys?
Proximal convoluted tubule.
What lines the proximal convoluted tubule?
Simple cuboidal epithelium with a pronounced brush border membrane.
What are the four parts of the loop of Henle?
Pars recta, thin descending limb, thin ascending limb, thick ascending limb.
What lines the thin limb of the loop of Henle?
Simple squamous epithelium.
How does the thin limb of the loop of Henle appear histologically?
It looks like a small capillary but without any red blood cells, also no brush border.
Where is the thick ascending limp of the loop of Henle best seen?
In the medulla, interspersed with thin limbs, vasa recta, and collecting duct.
What lines the thick ascending limb?
Simple cuboidal epithelium.
How can the thick ascending limb be differentiated from the proximal convoluted tubule?
It has no brush border.
What does the distal convoluted tubule contain lots of?
Mitochondria.
How does the distal convoluted tubule differ from the proximal convoluted tubule?
It has no brush border and a larger lumen.
What does the juxtaglomerular apparatus consist of?
Macula densa, juxtaglomerular cells, and extraglomerula mesangial cells.
How do macula densa cells of the juxtaglomerula apparatus appear histologically?
They are the dense staining region of the distal convoluted tubule.
What are the juxtaglomerular cells?
Cells of afferent arteriole of the glomerulus.
What is the collecting duct a continuation of?
The distal convoluted tubule.
How does the histological appearance of the collecting duct differ from the thick limbs of Henle’s loop?
Similar but the lumen is larger and tends to be more irregular than circular.
What forms the renal pyramids?
Progressively larger ducts merging together and emptying at the renal papilla.
What is the ureter?
A tube running from the renal pelvis to the bladder.
How many layers of muscle does the ureter have?
Two, but a third appears in the lower third.
What lines the ureter?
Transitional epithelium.
How many layers of muscle does the bladder have?
Three, like the lower ureter.
What lines the urinary bladder?
Transitional epithelia, surrounded by an outer adventitia.
What is urothelium?
Stratified epithelium on the surface of the bladder that makes it impermeable.
