Renal Anatomy + Histology

Question 1

describe the path of arterial blood flow in the kidneys

Answer 1

1. renal artery
2. segmental artery (end arteries - no collaterals)
3. interlobar artery
4. arcuate artery
5. interlobular artery
6. afferent arteriole
7. glomerulus

*kidneys receive ~20% of CO

Question 2

what are the anatomical differences in the right vs left kidney?

Answer 2

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

Question 3

where are kidney transplants usually attached?

Answer 3

dead/dying kidney is usually not removed, rather, new kidney is attached to iliac artery/vein

transplanted kidney is placed in the iliac fossa

Question 4

Which embryonic structures form the nephron and the collecting system, respectively? Which structures are included in the collecting system?

Answer 4

metanephros = nephron

ureteric bud (of mesonephric duct) = collecting system: collecting tubules/ducts, minor/major calyces, renal pelvis, ureter

nephron + collecting tubule/duct = uriniferous tubule

Question 5

Area between the medullary rays in the cortex of the kidney

Answer 5

cortical labyrinth

renal lobule = medullary ray + cortical labyrinth on both sides

Question 6

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.

Answer 6

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.

Question 7

nephrons with the longest loops of Henle are found in which region of the renal cortex?
a. superficial
b. juxtamedullary
c. intermediate

Answer 7

b. juxtamedullary - note nephrons are found in cortex but the loops of Henle dip into the medulla

Question 8

blood leaves the glomerulus via efferent arterial and forms a plexus of ____ that serve both the cortex and the medulla

Answer 8

blood leaves the glomerulus via efferent arterial and forms a plexus of PERITUBULAR CAPILLARIES that serve both the cortex and the medulla

Question 9

What type of epithelium makes up Bowman’s capsule in the kidney? in which layer are podocytes found?

Answer 9

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

Question 10

what kind of capillaries make up the glomerulus of the kidney?

Answer 10

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

Question 11

what three structures make up the filtration barrier of the renal glomerular capillaries?

Answer 11

1. Fenestrated capillary endothelial cells.
2. fused basement membranes
3. podocytes

Question 12

describe the composition of the glomerular basement membrane

Answer 12

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

Question 13

Where does most reabsorption occur in the nephron?

Answer 13

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)

Question 14

Is the tubular fluid within the loop of Henle hypotonic, isotonic, or hypertonic?

Answer 14

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

Question 15

Where is the macula densa found?

Answer 15

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

Question 16

what are the functions of uromodulin? (2)

Answer 16

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)

Question 17

which cells produce renin, and where they found?

Answer 17

juxtaglomerular cells (modified smooth muscle cells) of the afferent (“arriving”) arterial produce renin granules

Question 18

what is the function of the macula densa?

Answer 18

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

Question 19

Which structures make up the juxtaglomerular apparatus and what is its function?

Answer 19

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

Question 20

What is the function of the mesangium in the kidney?

Answer 20

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

Question 21

what structure in the nephron is primarily affected by diabetic nephropathy and lupus nephropathy?

Answer 21

Intra-glomerular mesangium: enclosed by glomerular basement membrane - provides structural support to podocytes, phagocytosis of old basement membrane components

Question 22

which ions are reabsorbed and secreted, respectively, at the distal convoluted tubule?

Answer 22

Reabsorbed: Na+, HCO3-, Ca2+

Secreted: K+, H+, NH4+

• note that there is NO brush border in the DCT as there is in the PCT

Question 23

What goes on in the connecting tubule of the nephron?

Answer 23

connecting tubule is the first part of the collecting system

Aldosterone mediated Na+ reabsorption / K+ secretion occurs here

Question 24

what is the function of principal cells in the nephron?

Answer 24

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

Question 25

Where in the nephron does water reabsorption mediated by antidiuretic hormone take place?

Answer 25

both the cortical collecting tubules and the medullary collecting ducts - principal cells (simple columnar epithelium) reabsorb water (via ADH and hypertonic medulla)

[ADH = vasopressin]

Question 26

What is the function of the intercalated cells in the cortical collecting tubules and the medullary collecting ducts of the nephron?

Answer 26

intercalated cells secrete H+ or HCO3- ions, depending on the body’s needs

Question 27

how does antidiuretic hormone work in the nephron?

Answer 27

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

Question 28

when 2 collecting ducts in the kidney merge, they form _____

Answer 28

when 2 collecting ducts in the kidney merge (in the papilla), they form a larger PAPILLARY DUCT

Question 29

where in the kidney do cells activate vitamin D3?

Answer 29

proximal convoluted tubule - cells hydroxylate 25-OH Vit. D3 to the active form, 1,25-dihydroxy vitamin D3

Question 30

which cells in the kidneys produce erythropoietin?

Answer 30

interstitial fibroblasts in the renal cortex

Question 31

where in the kidney is renin secreted?

Answer 31

Renin is secreted by the juxtaglomerular cells in the afferent arterial to regulate blood pressure via the renin angiotensin aldosterone system (RAAS)

Question 32

what kind of epithelium lines the minor calyces, major calyx, ureter, and urinary bladder of the kidney?

Answer 32

Urothelium - transitional epithelium

Question 33

at what vertebral level does bifurcation of the abdominal aorta occur, and what is an important anatomical landmark of this?

Answer 33

abdominal aorta bifurcates at L4, which is where the iliac crest lies

Question 34

nephroptosis

Answer 34

drooping kidney, caused by loose supportive fascia - kidney drops more than the normal range of ~1 vertebral level

ureter will have kinks

Question 35

where do the R/L renal arteries and R/L gonadal arteries branch off of the abdominal aorta, respectively? (Spinal segment)

Answer 35

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

Question 36

renal vein entrapment syndrome, aka Nutcracker Syndrome

Answer 36

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)

Question 37

where is the ureter in relation to the uterine artery in females?

Answer 37

“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

Question 38

what do the aorticorenal plexus and the inferior hypogastric plexus supply in the abdomen, respectively?

Answer 38

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

Question 39

what do sympathetic fibers do in the aorticorenal plexus and inferior hypogastric plexus, respectively?

Answer 39

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

Question 40

what do parasympathetic fibers do in the aorticorenal plexus and inferior hypogastric plexus, respectively?

Answer 40

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

Question 41

which bladder muscle is made of skeletal muscle and which nerve is it controlled by?

Answer 41

external urethral sphincter - skeletal muscle, under somatic regulation via pudendal nerve

Question 42

which nerves carry parasympathetic vs sympathetic signaling, respectively, to the kidneys and bladder?

Answer 42

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

Question 43

which nerves sense bladder stretching as it fills with urine and what is the nerve response?

Answer 43

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

Question 44

Nephrolithiasis / urolithiasis

Answer 44

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)

Question 45

what are the three bilateral construction points in the ureters that may be potential sites for obstruction by ureteric stone/calculi?

Answer 45

1. ureteropelvic junction: where the renal pelvis becomes the ureter
2. bony pelvic brim: ureter crosses from abdomen into the pelvis and over the bifurcation of the common iliac artery
3. ureterovesical junction: as the ureter traverses the urinary bladder wall, the narrowest and therefore most common site for impaction with a stone

Question 46

Where are the renal vein, renal artery, and renal pelvis in relation to each other?

Answer 46

renal vein is anterior to the renal artery, which are both anterior to the renal pelvis (at the superior end of the ureter)

Question 47

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 _______

Answer 47

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

Question 48

in nutcracker syndrome, the ___ is compressed by the ___ and the ____

Answer 48

in nutcracker syndrome, the RENAL VEIN is compressed by the ABDOMINAL AORTA and the SUPERIOR MESENTERIC ARTERY (SMA)

Question 49

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 ______.

Answer 49

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.

Question 50

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 ____.

Answer 50

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.

Question 51

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 _______.

Answer 51

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).

Question 52

The ______ is smooth muscle that contracts under sympathetic innervation to maintain urinary continence.

Answer 52

The internal urethral sphincter is smooth muscle that contracts under sympathetic innervation to maintain urinary continence.