Histology of the Kidney and Urinary Tract (Cirillo) Flashcards
What are the three functions of the kidney?
Excretory -removes drugs, toxins, metabolic products
Homeostatic- Regulates water and ion balance
Endocrine- monitors oxygen in the blood (erythropoietin) and blood pressure
What are the divisions of the kidney?
Outer layer is the cortex
Inner layer is the medulla
What is a lobe?
How many does a typical kidney have?
A lobe is a renal pyramid (medulla) and the surrounding cortex.
A kidney has 6-18 lobes.
Where is the renal papilla? What does it do and why is it important?
The renal papilla is the tip of the medulla. It is where the urine empties into the ureter.
It is extremely sensitive and nephrotoxins/dehydration typically work here to cause renal papillary necrosis.
Is the kidney a blood rich system or a blood poor system?
The kidney is a blood rich system; it filters total blood volume every 4-5 minutes.
What are the two divisions of the kidney blood flow? What parts of the vasculature are shared between these two systems?
Blood to be filtered and blood to nourish the kidney
The Renal, Lobar, and Interlobar arteries are common; afterwards, they split into the arcuate arteries and the afferent arterioles.
What happens to the blood that goes to the afferent arterioles?
What is unique about that?
afferent arterioles lead to the glomerulus and then some of the blood goes to the efferent arteriole while some goes to the vasa recta before rejoining the efferents.
This is a two capillary system.
What are the four components of the renal corpuscle?
Glomerulus
Visceral layer of renal capsule
Parietal layer of renal capsule
mesangium
Where are corpuscles found?
In the renal cortex
What is the design of the vascular pole of the glomerulus?
Larger afferent arteriole than efferent arteriole
macula densa adjacent to arterioles
What is between the visceral and parietal renal capsule layers? Why is it important?
The urinary space; this is where ultrafiltrate collects and moves to the tubules.
What does the visceral renal capsule look like histologically?
simple epithelium
pores
foot processes of podocytes
glycocalyx
What is nephrin?
a connective protein that attaches podocyte across filtration slits in the visceral renal capsule.
What does the mesangium do?
physical support
regulates blood flow
regenerates the glomerular basement membrane
How does the mesangium regulate blood flow?
smooth muscle cells can constrict blood vessels
ANP and ANGII receptors moderate endocrine release
what does the parietal layer of the renal capsule look like histologically?
simple squamous epithelium
What does the proximal tubule look like histologically?
simple cuboidal
cells appear grainy
pink lumen (glycocalyx)
Name the four parts of the Loop of Henle in order that the ultrafiltrate would pass through it. Where is the majority of every Loop of Henle located in the kidney?
1) Thick descending limb
2) Thin descending limb
3) Thin ascending limb
4) Thick ascending limb
Majorly in the renal medulla
1) What is the primary difference between cortical and juxtomedullary nephrons?
2) What do cortical nephrons lack in comparison to juxtomedullary nephrons?
1) Length
2) Cortical nephrons lack an ascending thin limb
1) What epithelial cell type lines the thick segments of the loop?
2) The thin segments?
1) Thick: Cuboidal
2) Thin: Simple Squamous
Is the ascending thin limb water permeable or impermeable? The ascending thick limb?
BOTH thick & thin ascending segments are water impermeable due to interdigitations between epithelial cells.
What are the functions of the thick ascending loop of Henle?
First two are similar to PT:
1) Na+, Cl-, water reabsorption
2) glucose, amino acid, protein reabsorption
Also functions to secrete H+
Which part of the nephron is responsive to aldosterone?
Convoluted (aka “Early”) Distal Tubule
What are the functions of the convoluted distal tubule?
1) Reabsorption of Na+, Cl-, K+, bicarbonate
2) Secretion of K+, H+, NH3, urate
Name the two types of cuboidal cells that make up the collecting tubules (aka “late distal tubule”). What are their functions and how do they appear under microscopy?
1) Principal (aka “Light”) cells. Lighter under microscopy. ADH-responsive site of aquaporin (AQP-2) insertion for water reabsorption.
2) Intercalated (aka “Dark”) cells. Darker under microscopy (abundant mitochondria). Function is acid/base balance (bicarbonate/H+ balance).
Which parts of the nephron are responsive to ADH?
Collecting Tubules (Late Distal Tubule) & Collecting Ducts
In the presence of ADH, what follows water out of the collecting duct as it is reabsorbed? What does this help accomplish?
Urea. This helps the kidney to produce hyperosmotic urine.
Lack of ADH would cause urine production of what osmolarity?
Hypotonic urine
1) What special cellular structure do principal cells of the collecting ducts feature?
2) What is its function?
3) What proteins mediate this function?
4) What disease results from defects in these proteins?
1) A single, nonmotile Primary Cilium
2) Acts as a flow sensor
3) Polycystin 1 & 2
4) Polycystic Kidney Disease
What is the name for the space between the tubules of various nephrons? What does it contain?
Renal Interstitium (stroma). Contains connective tissue and fibroblasts.
What three microstructures of the kidney are required for modification and concentration of urine?
1) Tubules (incl. Loops of Henle & Collecting Ducts)
2) Vasculature (vasa recta)
3) Renal Interstitium
What three components make up the Juxtaglomerular (JG) apparatus, and what are their functions?
1) JG cells - produce renin
2) Lacis (aka extraglomerular mesangial) cells - not well understood. Eryhthropoietin secretion?
3) Macula Densa - columnar cells that act as Na+/Cl- sensors for JG cells
What two functions does erythropoietin have? What three things stimulate erythropoietin production?
Functions: 1) Increased mitosis of RBC precursors 2) Increased release of RBCs from bone marrow Stimulation: 1) High altitude 2) Hemorrhage 3) Impaired pulmonary function
What part of the kidney are the renal corpuscles and convoluted segments of tubules found in?
Renal cortex
What three layers are the walls of the ureters made up of? What makes up each?
1) Mucosa - transitional (uro)epithelium w/ elastic lamina propria
2) Muscularis - smooth muscle cells
3) Adventitia - fibrous connective tissue
How many layers of SMCs are present in the walls of the ureter? Are they circular or longitudinal?
Proximal 2/3 of ureter: 2 layers of circular SMCs
Distal 1/3 of ureter: 3 layers of SMCs: 1 longitudinal (inner), 2 circular (outer)
(tl;dr: Distal 1/3 has additional inner layer of longitudinal SMCs)
How many layers of SMCs are present in the walls of the bladder? Are they circular or longitudinal?
3 layers of SMCs: 1 longitudinal (inner), 2 circular (outer)
N.B. This is opposite from the GI tract, where the circular SMCs are the inner layer
What are the three parts of the male urethra?
1) Prostatic
2) Membranous
3) Penile
Name three conditions/diseases that result in obstruction of the excretory passages.
1) BPH (aka nodular hyperplasia)
2) Renal Calculi (Kidney Stones)
3) Bladder Cancer
The majority of bladder cancers in the US involve what tissue?
Uroepithelium
Recall: What is a “lamina propria”? Describe it.
(From Wiki) A thin layer of connective tissue that lies beneath the epithelium, and with the epithelium constitutes the mucosa.
About how long is the female urethra? The male urethra?
Female: 3-5cm
Male: 13-15cm
