Renal Anatomy & Histology Flashcards
In what category of organs are kidneys?
retroperitoneal organs
At what vertebral levels are the kidneys located?
T12-L3
-right kidney is a little lower d/t the liver
What sits on top of the kidneys?
suprarenal glands
What is the size of the kidney?
10 cm long
5 cm wide
2 cm thick
How far away from the median plane are the kidneys?
5 cm from median plane to the hilum
Where does the transpyloric plane “run through” each kidney?
left - hilum
right - superior pole
The superior parts of the kidneys lie at which rib levels?
Ribs 11 and 12
How is the right kidney related anatomically to the iliac crest?
the inferior pole of the right kidney is one index finger’s width above the iliac crest
What tissue layers surround each kidney, deep to superficial?
perinephric fat - extends into renal hilum
renal fascia - also covers suprarenal gland and vessels
paranephric fat
Do the kidneys move?
Yes, during respiration, the can move approx 3 cm
Delineate the arterial supply to the kidneys.
Renal A. off of descending aorta
-segmental aa., interlobar aa. (pass through renal columns to get to the renal cortex), arcuate aa., interlobular aa., afferent arterioles, glomerulus, efferent arterioles
What are the two capillary beds of the renal system?
glomerulus
peritubular capillaries
Delineate the venous return leaving the peritubular capillaries.
interlobular vv.
arcuate vv.
interlobar vv.
Renal V.
What is the blood supply to the ureters?
- opportunistic; grab whatever blood supply they can as they descend
- renal A., gonadal A., abdominal aorta branches, iliac branches
What is the sympathetic nerve supply to the kidneys?
lesser splanchnic N. (T10-T11)
least splanchnic N. (T12)
lumbar splanchnic nn. (L1-L2)
What is the parasympathetic nerve supply to the kidneys?
posterior vagal trunk
–from R vagus N.
Where is EPO made in the kidneys?
in the interstitial area of the renal cortex
What is the renal cortex?
the outer portion containing the renal corpuscles
What is the renal medulla?
the collection of pyramids and columns
What are the renal pyramids?
cone-shaped masses in the medulla
What comprises a renal lobe?
single pyramid and the surrounding cortex
What is the renal column?
tissue lying b/w pyramids
runs from cortex to calyx
What is the renal capsule?
a covering of dense irregular connective tissue w/ inner myofibroblasts
What is a renal papilla?
projection of pyramid apex into the calyx
Delineate the flow from the minor calyx to the ureter.
minor calyx
major calyx
renal pelvis
ureter
What comprises a nephron?
a corpuscle and its tubules
What are the two types of nephrons?
cortical nephrons - superficial, do most of the filtering, high GFR
juxtamedullary nephrons - deeper in the cortex, set the concentration of urine
What structures come together in the renal papillae before heading into the minor calices?
collecting ducts of each nephron
What type of epithelium comprises the glomerulus?
fenestrated
What are the two parts of the peritubular capillaries (the second capillary bed in addition to the glomerulus)?
cortical = surrounds PCT and DCT; fenestrated epithelium
vasa recta = in the medulla surrounding the Loop of Henle
What type of epithelium comprises the vasa recta around the descending and ascending Loops of Henle?
descending = continuous epithelium ascending = fenestrated epithelium
What comprises a renal corpuscle?
glomerulus
Bowman’s capsule
What are the layers, deep to superficial of a Bowman’s capsule?
visceral layer = in contact w/ capillaries, has podocytes
glomerular space = contains primary filtrate
parietal layer = simple squamous epithelium
What are mesangial cells?
- structural support for glomerular loops and ECM of podocytes
- contractile phagocytic cells that prevent glomerular distention (since glomerular BP is high)
What are mesangial cells capable of secreting?
secrete growth factors and cytokines in response to injury
What are the three components of the renal filtration barrier?
glomerular endothelium
glomerular basement membrane
podocytes of the visceral layer of Bowman’s capsule
What are characteristics of the glomerular endothelium?
fenestrated
thick luminal glycocalyx
lots of aquaporin channels
can generate NO and PGE2 (vasodilators)
What are characteristics of the glomerular basement membrane?
consists of Type IV and XVIII collagens, laminin, entactin, and proteoglycans
How does the glomerular basement membrane serve as a physical barrier?
it restricts particles larger than 70 kD from entering into the urinary system
How does the glomerular basement membrane serve as a chemical barrier?
it’s stronly anti-ionic
-repels negatively charged molecules (ex: proteins)
thus, albuminia is indicative of damage
What are characteristics of podocytes?
- part of the visceral layer of Bowman’s capsule
- foot-like processes that interdigitate to make filtration-like slits
What is the purpose of the renal filtration barrier?
- restricts passage of blood cells, immunoglobulins and large proteins into the urine
- allows passage of water, ions, glucose, amino acids, and urea into the urine … literally makes the urine
What are the characteristics of the proximal convoluted tubule (PCT)?
- lumen looks like a star (highly folded)
- most active tubule in resorption and secretion
- simple cuboidal to columnar epithelium
- abundant microvilli
- abundant mitochondria for transporters (sGLT2)
What are the characteristics of the proximal straight tubule?
- not as tall as PCT
- less well-developed brush border
- high-affinity sodium-glucose transporters (sGLT1)
What are the characteristics of the thin segment of the Loop of Henle?
- permeable simple squamous epithelium
- no brush border
- some nuclei bulge into the lumen
What are the characteristics of the thick segment of the Loop of Henle?
- simple cuboidal epithelium
- numerous microvilli, but no visible brush border
What is the purpose of the Loop of Henle?
sets up the hyperosmotic gradient
In what part of the kidney is the PCT located?
in the renal cortex
In what part of the kidney is the Loop of Henle?
- loops down into the medulla and then back up into the cortex
- terminates near the vascular pole of the corpuscle
In what part of the kidney is the DCT?
-in the renal cortex
What are the characteristics of DCT?
- round lumen
- simple cuboidal epithelium
- sparse microvilli
- angiotensin II has a big role in sodium reabsorption
What are the two components of the Juxtaglomerular Apparatus?
- juxtaglomerular cells
- macula densa
What are juxtaglomerular cells?
- mechanosensory cells that are right up against the afferent arterioles
- signaled by the macula densa to secrete renin if BP is low
What is the macula densa?
- tight nuclei at distal end of the thick ascending Loop of Henle
- monitor sodium levels in urine and signal the juxtaglomerular cells to secrete renin
What is the role of collecting ducts?
determine final osmolality by reabsorbing water
What hormones primarily target the collecting ducts?
ADH
aldosterone
What are the two types of mechanosensory cells of the collecting ducts?
- principal cells aka light cells (target of aldosterone)
- intercalated cells (H+ and HCO3- transport)
-these cells are the targets of many pharmaceuticals
What type of cells comprise the collecting tubules?
simple cuboidal epithelium
-transitions to columnar near the papillae
Where in the kidney are the collecting tubules and ducts located?
run through the cortex and deep into the medulla
-several tubules join together at papilla to form a duct before draining into the minor calyx
What are the components of the urinary tract?
-ureters, bladder, urethra
What is the major type of cell lining the urinary tract?
urothelium (transitional epithelium)
Where is the urothelium found?
- lining the calices
- ureters
- bladder
- proximal parts of the urethra
What are the three layers deep to superficial of the urothelium?
- deep: one layer of basal cells on basement membrane
- intermediate: “sliding layer” of cuboidal/columnar layers
- superficial = umbrella cells that stretch and relax
- -binucleated cells
What is the urothelium’s special function that is significant to the urinary tract?
- as urine fills, cells flatten and membrane thickens
- urothelial plaques form impermeable barrier
- -made with uroplakin proteins that protect from urine
- when urine empties, the proteins are endocytosed
- -stored in vesicles until needed
What are the characteristics of the ureters?
- fibromuscular tube from kidneys to the bladder
- superficial urothelium folded around lumen
- muscularis (3 layers) that moves with peristaltic waves
- adventitia (connective tissue)
- empty bladder at an oblique angle to avoid retroflow
What are the characteristics of the bladder?
- normally holds 400-600 mL (up to 1L)
- enclosed by the detrusor muscle (smooth muscle), muscular sac enclosing bladder
Where is the bladder located?
- anterior to uterus and rectum
- sits within the pelvis, but expands into abdomen
What is the trigone of the bladder?
-the inferior/posterior wall where the ureters and urethra open
What are the layers, superficial to deep, of the bladder wall?
- urothelium
- detrusor muscle
- fibrous adventitia
What is the length of the female urethra versus the male urethra?
female: 3-5 cm
male: 20 cm
What are the three types of epithelium in the urethra and their locations?
- urothelium = near the bladder
- pseudostratified columnar = majority
- stratified squamous = distal end
What is the female urethra called?
membranous urethra = the portion that passes through the urogenital diaphragm
What are the sphincters of the bladder and their muscular qualities?
- internal sphincter = involuntary
- external sphincter = voluntary skeletal muscle; part of the pelvic floor
What does the female urethra facilitate versus the male urethra?
female = urine male = urine and semen
What are the regions of the male urethra?
- prostatic urethra
- membranous urethra
- spongy (penile) urethra
- -through corpus spongiosum, the cylindrical erectile tissue in the penis
