Renal Anatomy & Histology Flashcards
Describe renal gross anatomy
retroperitoneal organs in posterior of abdomen, extend from T12-L3, surparenal glands atop each, renal hilum entrance of blood vessels, renal pelvis, nerves
posteriorly, transpyloric plane at L1, superior poles deep to 11th and 12th ribs
What are the points of constriction for the ureters?
uretopelvic junction, over the common/external iliac, and uretovesical junction
What is the renal blood supply starting at the aorta and ending at the inferior vena cava?
Aorta •Renal artery (branches in the renal sinus and sends...) •Segmental artery •Interlobar arteries (between pyramids to the cortex, then turn to the base of the pyramids between medulla and cortex as...) •Arcuate arteries •Interlobular arteries ascend in the cortex, give off... •Afferent arterioles •Glomerular capillaries •Efferent arteriole •Peritubular capillaries/vasa recta •Interlobular veins •Arcuate veins •Interlobar veins •Renal vein Inferior vena cava
What is the renal nerve supplu?
Sympathetic: Renal plexus - lesser splanchnic (T10-T1), least splanchnic (T12), Lumbar splanchnic (L1-L2)
Parasympathetic: Vagus nerve
Cortex contains…
renal corpuscles, convoluted and straight tubules of the nephron, and portions of collecting ducts
The medulla contains…
renal columns and cone-shaped masses called renal pyramids
What are cortical medullary rays?
aggregation of collecting ducts and straight tubules running between the renal corpuscles and convoluted tubules within the cortex (arrows in image); axis of renal lobule
What is made in the fibroblasts of the renal interstitium?
erythropoietin
Cortical labyrinth =
between the medullary rays; contains the RC + convoluted tubules + collecting tubules
Urine carrying unit made of:
- Nephron (urine forming unit) - consists of renal corpuscle and renal tubules (>1-2 million/kidney)
- Cortical and medullary collecting ducts – final concentration of urine
List the renal tubular structures starting at the glomerulus
Bowman’s capsule Proximal convoluted tubule Proximal straight tubule Thin loop of Henle Thick ascending loop of Henle Macula densa location Distal convoluted tubule Collecting tubule Collecting duct-cortical Collecting duct-medullary Papillary duct
What constitutes the renal corpuscle?
glomerular capillary tuft: fenestrated with truly open pores; afferent and efferent arteriole
bowman’s capsule: parietal layer (simple squamous), visceral layer (podocytes), glomerular space (ultrafiltrate)
What is special about the glomerular endothelium?
Fenestrated, no diaphragm, AQP-1 water channels, secretes NO and PGE2, glycocalyx
Describe the function of podocytes.
Located in visceral layer of Bowman’s capsule, extend secondary processes around capillaries called pedicels which interdigitate to create filtration slits that act as a size selective barrier
Describe the Glomerular Basement Membrane
both a physical and ion selective barrier
Type IV and XVIII collagens, laminin, fibronectin, entactin, proteoglycans and glycosaminoglycans (heparin sulfate)
Restricts proteins larger than 70kD such as albumin and hemoglobin
•Albuminuria or hematuria indicate physical or
functional damage to the GBM
Negative charge also restricts movement of anionic particles
Protein that does leak through is typically reabsorbed by the proximal convoluted tubule
What are the three components of the renal corpuscular filtration apparatus?
- glomerular endothelium
- GBM
- visceral layer of bowman’s capsule
What is bowman’s space?
Space between the visceral and parietal layers of Bowman’s capsule
- Receptacle for glomerular ultrafiltrate (primary filtrate/urine)
- Continuous with the proximal convoluted tubule at the urinary pole of renal corpuscle
Where are mesangial cells located and what is their function?
located in the renal corpuscle; mesangial cells + ECM = mesangium; like pericytes; function in phagocytosis and endocytosis, structural support, secretion of IL-1, PGE2, PDGF, and modulation of glomerular distention (contraction)
*clinical note: proliferation of mesangium is pathognomonic for certain kidney diseases
Describe the PCT
Found only in renal cortex, receives ultrafiltrate from Bowman’s space (180 L/day)
•65% reabsorbed (120/Lday)
Simple cuboidal to columnar epithelium with apical brush border/microvilli and mitochondria
Na/K/ATPase pumps actively reabsorb Na+ , Cl- passively diffuses, H2O follows via AQP-1
Reabsorbs amino acids, sugars (sGLT2), polypeptides
Proteins and large peptides are endocytosed
Describe the PROXIMAL STRAIGHT TUBULE/ Thick descending limb
- Shorter than the PCT
- Less well-developed brush border
- Contain high-affinity sodium-glucose co-transporters (sGLT1)
What is the function of the thin segment of the loop of henle?
structurally: Juxtamedullary nephrons – long; cortical nephrons – short
•Simple squamous epithelium without brush border
•Some nuclei bulge into lumen
Functionally:
Thin descending limb:
•Highly permeable to water, less permeable to NaCl,
urea
•Water diffuses out
Thin ascending limb:
•Highly permeable to NaCl
•NaCl diffuses into interstitium
•Impermeable to water
Describe the function of the thick ascending loop of henle (aka distal straight tubule).
Simple cuboidal epithelium with microvilli but no visible brush border
•Cortical and medullary (latter in the medullary ray)
- Na, K, and Cl- diffuse out of filtrate into interstitium
- No movement of water
- Nucleus in apical section, cells bulge into the lumen
Describe the function of the distal convoluted tubule.
- Simple cuboidal epithelium without brush border (smoother lumen)
- Shorter than PCT cells = relatively larger lumen
- Reabsorb: •Na+ and HCO3-
- Secrete:•K+ and NH4+
•DCT exchanges Na for K under aldosterone (which is released under stimulation from angiotensin II) regulation
Describe the Collecting tubules/ducts and the two distinct cell types found here.
– simple squamous to cuboidal epithelium
•Medullary collecting ducts – simple cuboidal to columnar epithelium
- Light cells (principal cells):
- single cilium
- Target of ADH-regulated AQP2 channels
- Dark cells (intercalated cells):
- alpha-intercalated – secrete H+
- β-intercalated – secrete HCO3-
- CD primary function is water reabsorption via aldosterone regulation
- CD will eventually join to form larger papillary ducts that drain into a minor calyx
