Renal Anatomy + Histology Flashcards
describe the path of arterial blood flow in the kidneys
- renal artery
- segmental artery (end arteries - no collaterals)
- interlobar artery
- arcuate artery
- interlobular artery
- afferent arteriole
- glomerulus
*kidneys receive ~20% of CO
what are the anatomical differences in the right vs left kidney?
right kidney is smaller due to less development in utero (because of sharing space with the liver)
left kidney has longer renal vein because it has to pass over the midline where the descending aorta is… for this reason, L kidney preferentially taken for transplant
*note kidneys are about the level of T12-L3
where are kidney transplants usually attached?
dead/dying kidney is usually not removed, rather, new kidney is attached to iliac artery/vein
transplanted kidney is placed in the iliac fossa
Which embryonic structures form the nephron and the collecting system, respectively? Which structures are included in the collecting system?
metanephros = nephron
ureteric bud (of mesonephric duct) = collecting system: collecting tubules/ducts, minor/major calyces, renal pelvis, ureter
nephron + collecting tubule/duct = uriniferous tubule
Area between the medullary rays in the cortex of the kidney
cortical labyrinth
renal lobule = medullary ray + cortical labyrinth on both sides
which of these structures are found in the renal cortex versus medulla?
a. Renal corpuscle.
b. Proximal convoluted tubule
c. Descending limb of Henle
d. Macula densa
e. Distal convoluted tubule
f. Collecting tubule
g. Collecting duct.
Cortex:
a. Renal corpuscle.
b. Proximal convoluted tubule
Medulla:
c. Descending limb of Henle
Cortex:
d. Macula densa
e. Distal convoluted tubule
f. Collecting tubule
Medulla:
g. Collecting duct.
nephrons with the longest loops of Henle are found in which region of the renal cortex?
a. superficial
b. juxtamedullary
c. intermediate
b. juxtamedullary - note nephrons are found in cortex but the loops of Henle dip into the medulla
blood leaves the glomerulus via efferent arterial and forms a plexus of ____ that serve both the cortex and the medulla
blood leaves the glomerulus via efferent arterial and forms a plexus of PERITUBULAR CAPILLARIES that serve both the cortex and the medulla
What type of epithelium makes up Bowman’s capsule in the kidney? in which layer are podocytes found?
squamous epithelial cells in both parietal and visceral layer, podocytes are found in visceral layer
glomerulus + Bowman’s capsule = renal corpuscle
*note corpuscle has a vascular pole and a urinary pole - glomerular filtrate enters the proximal convoluted tubule of the nephron at the urinary pole
what kind of capillaries make up the glomerulus of the kidney?
Fenestrated capillaries
glomerulus + Bowman’s capsule = renal corpuscle
*note corpuscle has a vascular pole and a urinary pole - glomerular filtrate enters the proximal convoluted tubule of the nephron at the urinary pole
what three structures make up the filtration barrier of the renal glomerular capillaries?
- Fenestrated capillary endothelial cells.
- fused basement membranes
- podocytes
describe the composition of the glomerular basement membrane
GPM is composed of glycosaminoglycans contributed from both the endothelial cells in the podocytes
Three layer structure – lamina rara, interna adjacent to the capillary, lamina rara externa adjacent to the podocytes, overlap produces the lamina densa
Where does most reabsorption occur in the nephron?
proximal convoluted tubule – most of water and sodium reabsorption into the peritubular capillaries occurs here
Brush border made of microvilli and basal infoldings increases surface area, very wide cells with lots of mitochondria and ion pumps (Na/K ATPase)
Is the tubular fluid within the loop of Henle hypotonic, isotonic, or hypertonic?
in the loop of Henle, more salt than water is reabsorbed – tubular fluid becomes hypotonic while the interstitium becomes hypertonic
A hypertonic medulla is essential for water reabsorption from the collecting ducts
Where is the macula densa found?
ascending thick limb of Henle comes very close to the vascular pole of the glomerulus at the macula densa (in the cortex)
macula densa marks the beginning of the distal convoluted tubule
what are the functions of uromodulin? (2)
protein produced by the thick ascending limb of the loop of Henle, a.k.a. Tamm-Horsfall protiein - most abundant protein in human urine
functions:
1. binds bacteria to reduce UTI
2. hinders formation of calcium deposits in the tubules (renal calculi)
which cells produce renin, and where they found?
juxtaglomerular cells (modified smooth muscle cells) of the afferent (“arriving”) arterial produce renin granules
what is the function of the macula densa?
Cells of the macula densa sense the Na+ concentration of the tubular fluid and regulate GFR (via tubular-glomerular feedback) and the release of renin from the juxtaglomerular cells of the afferent arteriole
part of the juxtaglomerular apparatus, located at the vascular pole of the glomerulus
Which structures make up the juxtaglomerular apparatus and what is its function?
macula densa (ascending limb of Henle) + JG cells (afferent arteriole) + mesangium (extraglomerular) = JG apparatus
located at vascular pole of glomerulus, regulates BP by activity renin-angiotensin-aldosterone (RAAS) system
—> renin released from JG cells and converted into angiotensin II
What is the function of the mesangium in the kidney?
extraglomerular mesangium: part of the juxtaglomerular apparatus
Intra-glomerular mesangium: enclosed by glomerular basement membrane - provides structural support to podocytes, phagocytosis of old basement membrane components, and is site of diabetic nephropathy and lupus nephropathy
what structure in the nephron is primarily affected by diabetic nephropathy and lupus nephropathy?
Intra-glomerular mesangium: enclosed by glomerular basement membrane - provides structural support to podocytes, phagocytosis of old basement membrane components
which ions are reabsorbed and secreted, respectively, at the distal convoluted tubule?
Reabsorbed: Na+, HCO3-, Ca2+
Secreted: K+, H+, NH4+
- note that there is NO brush border in the DCT as there is in the PCT
What goes on in the connecting tubule of the nephron?
connecting tubule is the first part of the collecting system
Aldosterone mediated Na+ reabsorption / K+ secretion occurs here
what is the function of principal cells in the nephron?
Principal cells: simple columnar epithelium in the cortical collecting tubules and the medullary collecting ducts
Reabsorb water driven by ADH and the hypertonic medulla
Also reabsorb Na+ and secrete K+, driven by aldosterone
Where in the nephron does water reabsorption mediated by antidiuretic hormone take place?
both the cortical collecting tubules and the medullary collecting ducts - principal cells (simple columnar epithelium) reabsorb water (via ADH and hypertonic medulla)
[ADH = vasopressin]
What is the function of the intercalated cells in the cortical collecting tubules and the medullary collecting ducts of the nephron?
intercalated cells secrete H+ or HCO3- ions, depending on the body’s needs
how does antidiuretic hormone work in the nephron?
ADH/vasopressin induces water reabsorption by opening Aquaporin2 (Aqp2) channels in the principal cells of the collecting tubules and ducts
Interstitial tissue must be hypertonic for net water movement from the tubules – this was accomplished by the countercurrent multiplier in the loop of Henle
Polyanionic glycosaminoglycans in the renal medulla sequester sodium ions to keep the medulla hypertonic
when 2 collecting ducts in the kidney merge, they form _____
when 2 collecting ducts in the kidney merge (in the papilla), they form a larger PAPILLARY DUCT
where in the kidney do cells activate vitamin D3?
proximal convoluted tubule - cells hydroxylate 25-OH Vit. D3 to the active form, 1,25-dihydroxy vitamin D3
which cells in the kidneys produce erythropoietin?
interstitial fibroblasts in the renal cortex
where in the kidney is renin secreted?
Renin is secreted by the juxtaglomerular cells in the afferent arterial to regulate blood pressure via the renin angiotensin aldosterone system (RAAS)
what kind of epithelium lines the minor calyces, major calyx, ureter, and urinary bladder of the kidney?
Urothelium - transitional epithelium
at what vertebral level does bifurcation of the abdominal aorta occur, and what is an important anatomical landmark of this?
abdominal aorta bifurcates at L4, which is where the iliac crest lies
nephroptosis
drooping kidney, caused by loose supportive fascia - kidney drops more than the normal range of ~1 vertebral level
ureter will have kinks
where do the R/L renal arteries and R/L gonadal arteries branch off of the abdominal aorta, respectively? (Spinal segment)
renal arteries branch off abdominal aorta at L1, and longer right renal artery passes posterior to the IVC - note these are end arteries (no collaterals)
gonadal arteries branch at L2 - have anastomoses but are very small, so at risk for ischemia regardless
renal vein entrapment syndrome, aka Nutcracker Syndrome
left renal vein is wedge anteriorly to abdominal aorta and posteriorly to superior mesenteric artery
compression of left renal vein —> impeded draining into IVC, hematuria or proteinuria, left flank pain, left testicular pain, left-sided varicocele (enlarged vein)
where is the ureter in relation to the uterine artery in females?
“water under the bridge”: ureter is inferior to the uterine artery - important relationship for surgeons to be aware of when ligating the uterine arteries during hysterectomy
what do the aorticorenal plexus and the inferior hypogastric plexus supply in the abdomen, respectively?
aorticorenal plexus: supplies nearby kidneys and upper part of the ureters
inferior hypogastric plexus: supplies the nearby urinary bladder and lower parts of the ureters
what do sympathetic fibers do in the aorticorenal plexus and inferior hypogastric plexus, respectively?
SNS activation:
aorticorenal plexus - vasoconstriction of renal vessels to slow urine formation
inferior hypogastric plexus - smooth muscle contraction of the internal urethral sphincter at the neck of the bladder to maintain urinary continence
what do parasympathetic fibers do in the aorticorenal plexus and inferior hypogastric plexus, respectively?
PSNS activation:
aorticorenal plexus - contraction of smooth muscle in proximal part of ureters for peristalsis to move urine towards the bladder
inferior hypogastric plexus - induce contraction of smooth muscle in the lower part of the ureters for peristalsis via 1) stimulating contraction of detrusor muscle of bladder wall and 2) inhibiting contraction of the smooth muscle in the internal urethral sphincter
which bladder muscle is made of skeletal muscle and which nerve is it controlled by?
external urethral sphincter - skeletal muscle, under somatic regulation via pudendal nerve
which nerves carry parasympathetic vs sympathetic signaling, respectively, to the kidneys and bladder?
Sympathetic – splanchnic nerves, carry visceral pain sensations
parasympathetic – vagus nerve (CN X) and pelvic splanchnic nerves that originate in S2, S3 and S4, carry sensations associated with bladder wall stretching as it fills with urine
which nerves sense bladder stretching as it fills with urine and what is the nerve response?
parasympathetic fibers - vagus nerve (CN X) and pelvic splanchnic nerves originating at S2/S3/S4
bladder stretching is sensed through afferents traveling along the parasympathetic pelvic splanchnic nerves —> efferent signals return along the parasympathetic pelvic splanchnic nerves —> contract the detrusor muscle and relax the internal urethral sphincter
pudendal nerve innervates the external urethral sphincter, which needs to relax for urination to take place
Nephrolithiasis / urolithiasis
aka calculi, or kidney stones
Causes urine to back up proximal to the stone —> Hydronephrosis (kidney swelling) and colic (pain)
symptoms usually relieved when stone reaches bladder and urethra, because they have larger lumens than the ureter
can use shockwaves to break stones into fragments that can be passed (lithotripsy)
what are the three bilateral construction points in the ureters that may be potential sites for obstruction by ureteric stone/calculi?
- ureteropelvic junction: where the renal pelvis becomes the ureter
- bony pelvic brim: ureter crosses from abdomen into the pelvis and over the bifurcation of the common iliac artery
- ureterovesical junction: as the ureter traverses the urinary bladder wall, the narrowest and therefore most common site for impaction with a stone
Where are the renal vein, renal artery, and renal pelvis in relation to each other?
renal vein is anterior to the renal artery, which are both anterior to the renal pelvis (at the superior end of the ureter)
superior surface of the urinary bladder is supplied by superior vesical arteries that branch from umbilical arteries. Umbilical arteries and inferior vesical arteries are branches of the _______
superior surface of the urinary bladder is supplied by superior vesical arteries that branch from umbilical arteries. Umbilical arteries and inferior vesical arteries are branches of the INTERNAL ILIAC ARTERIES
in nutcracker syndrome, the ___ is compressed by the ___ and the ____
in nutcracker syndrome, the RENAL VEIN is compressed by the ABDOMINAL AORTA and the SUPERIOR MESENTERIC ARTERY (SMA)
Peristalsis that moves urine through the proximal part of the ureters occurs through smooth muscle innervation by parasympathetic fibers in the _____ nerve that reach the _____ plexus. Pain from a stone in these proximal part of the ureters course along lesser and least splanchnic nerves and are felt in the ______.
Peristalsis that moves urine through the proximal part of the ureters occurs through smooth muscle innervation by parasympathetic fibers in the VAGUS nerve that reach the AORTICORENAL plexus. Pain from a stone in these proximal part of the ureters course along lesser and least splanchnic nerves and are felt in the LOIN.
The urinary bladder in the male is anterior to the rectum with the _____ pouch in between.
The urinary bladder in the female is anterior to the _____, an inferior to the ____.
The urinary bladder in the male is anterior to the rectum with the VESICORECTAL pouch in between.
The urinary bladder in the female is anterior to the VAGINA an inferior to the UTERUS.
Smooth muscle in the wall of the urinary bladder is called the ____, and is under parasympathetic innervation during urination. The nerves carrying fibers to contract the ____ are the _______.
Smooth muscle in the wall of the urinary bladder is called the detrusor, and is under parasympathetic innervation during urination. The nerves carrying fibers to contract the detrusor are the pelvic splanchnic nerves (S2-S4).
The ______ is smooth muscle that contracts under sympathetic innervation to maintain urinary continence.
The internal urethral sphincter is smooth muscle that contracts under sympathetic innervation to maintain urinary continence.
