Lecture 15: Urinary System

Question 1

Kidney structure

Answer 1

Several lobes w/ cortex + medulla. Each lobe = multiple lobules

Question 2

Hilum

Answer 2

Aka hilar region/hilus. Region where renal artery, vein, and ureter enter the kidney.

Question 3

Renal sinus

Answer 3

CT space between lobes continuous with the hilus. Contains first major vessel branches and distal ureter branches (aka major/minor calyces)

Question 4

Medullary pyramid

Answer 4

Structure shaped by epithelia-lined minor calyces. Separates renal sinus from medullae of lobes

Question 5

Collecting ducts

Answer 5

Series of tubes extending into medulla; extension of calyx lumen. Each drains several nephrons via short tangential collecting tubules.

Question 6

Ducts of Bellini

Answer 6

Area of collecting ducts opening up to minor calyx.

Question 7

Medullary ray

Answer 7

Collection of collecting ducts in medulla, defines center of corticle lobule

Question 8

Nephron

Answer 8

Basic functional unit of kidney. Contains 1 highly folded tubule and a capillary bed.

Question 9

Glomerulus

Answer 9

Encapsulated capillary bed at distal end of nephron. Located in cortex; tube descends and returns through the medulla.

Question 10

Juxtaglomerular apparatus (JGA)

Answer 10

Returning DCT comes in close approximation to the originating glomerulus. Set of structures for signaling filtration efficiency

Question 11

JGA structures

Answer 11

1. Macula densa
2. Extraglomerular mesangial cells (lacis cells)
3. Juxtaglomerular cells

Question 12

Macula densa (JGA)

Answer 12

Concentrated nuclei of JGA on side of glomerulus. Senses filtrate salt balance at apical surface. Communicates with other JGA cells via paracrine signals.

Question 13

Extraglomerular mesangial cells

Answer 13

Aka lacis cells. Nearby CT cells sitting between the other structures. Forms cap over glomerulus vascular pole.

Question 14

Juxtaglomerular cells

Answer 14

First and last sm. muscle cells in a/efferent arterioles to/from glomerular capillaries. Controls GFR by vessel diameter and renin secretion.

Question 15

Nephric tubule

Answer 15

From distal to prox (rel. to kidney): PCT -> prox. straight -> thick descend. -> thin descend./ascend. -> thick ascend. -> dist. straight -> DCT

Prox./dist. in terms is relative to glomerulus

Question 16

Nephric tubule morphologies

Answer 16

PCT + thick descend. = large cells w/ apical brush border + basal enfoldings (ion pumps/pore proteins)
Thin tubule = near-squamous
Thick ascend. + DCT = basal strations, smaller cells vs PCT
Collecting duct = (major.) principal cells + (minor.) intercalated cells (more mito.)

Question 17

Bowman’s capsule

Answer 17

Epithelial-lined space by which nephric tubule encapsulates its associated glomerulus. Has inner visceral and outer parietal epithelia.

Question 18

Inner visceral epithelium of Bowman’s capsule

Answer 18

Part of glomerulus; podocytes w/ interdigitating pedicels.

Question 19

Podocytes

Answer 19

Form filtration slits through interdigitating pedicels, spanned by filtration diaphragm

Question 20

Filtration diaphragm

Answer 20

Spans filtration slits between pedicels, made of transmembrane nephrin

Question 21

Outer parietal epithelium of Bowman’s capsule

Answer 21

Simple squamous cells

Question 22

Bowman’s space

Answer 22

Aka urinary space. Space between inner/outer visceral/parietal epithelia of Bowman’s capsule. Filtrate drains into here toward urinary pole.

Question 23

Intraglomerular mesangial cells

Answer 23

Major element of glomerulus CT space, between podocytes and endothelium. Similar to JGA lacis cells. Phagocytic, contractile, CT matrix production, growth factor release.

Question 24

Glomerulus

Answer 24

Highly convoluted capillary bed under visceral epithelium and basal CTs (minimal CT space). Forms arterial portal system between afferent/efferent arterioles.

Question 25

Minimum kidney filtration barrier

Answer 25

1. Fenestrated endothelium + basement 2. Podocyte basement + filtration slit Selects substances by size + charge.

Question 26

Renal corpuscle

Answer 26

Glomerulus + encapsulating nephric tubule (parietal Bowman's capsule layer)

Question 27

Vascular pole of renal corpuscle

Answer 27

Afferent/efferent arteriole regions

Question 28

Urinary pole of renal corpuscle

Answer 28

Origin of PCT

Question 29

Renal artery branching (afferent)

Answer 29

Enters at hilum -> 5 branches in renal sinus -> segmental -> interlobar -> arcuate (entering lobe, cortico-medullary) -> interlobular -> afferent arterioles

Question 30

Renal vein branching (efferent and out)

Answer 30

Efferent arterioles -> 2nd cap. bed of portal system (peritubular cap. plexus/vasa recta) -> interlobular veins -> arcuate -> interlobar -> renal vein All run parallel to homonymous arteries

Question 31

Peritubular capillary plexus

Answer 31

Capillary blood supply for cortical layers

Question 32

Vasa recta

Answer 32

Capillary blood supply for medullary layers

Question 33

Erythropoietin production

Answer 33

Produced by cortical interstitum, controls marrow RBC production. Secretion triggered by low kidney O2

Question 34

Prostaglandin production

Answer 34

Producing cells found in medullary interstitum

Question 35

Kidney functional compartments

Answer 35

1. Superficial renal cortex 2. Medulla

Question 36

Columns of Bertin

Answer 36

Cortical tissue separating renal pyramids (medullary tissue)

Question 37

Filtrate path

Answer 37

Cortex -> through pyramids -> renal papilla -> minor calyx -> major calyx -> renal pelvis -> ureter

Question 38

Blood path

Answer 38

Renal artery -> hilus -> renal pelvis, calyces, sinus -> cortical branching -> renal vein draining

Question 39

Nephron types

Answer 39

1. Cortical (shorter tubule, higher in cortex) 2. Juxtamedullary (much longer loop of Henle, important for urine concentration)

Question 40

Loop of Henle

Answer 40

Thick/thin descending/ascending tubules

Question 41

Relative tubule permeability

Answer 41

PCT: glucose, ions, H2O, AAs Thick/thin descend.: H2O Thick/thin ascend.: Na+, Cl- DCT: Ca++, Na+, Cl- Collecting duct: H2O, Ca++, Na+, Cl-

Question 42

Hormonal system control of tubules

Answer 42

Nephron/collect. duct system has different localized aquaporin channels. Hormones like ADH control aquaporin activation and H2O resorption

Question 43

Medullary osmolarity

Answer 43

Deeper into the medulla osmolarity increases, up to 1200 mOsm near the renal papilla. Allows more efficient H2O resorption.

Question 44

Nephric tubule functional roles

Answer 44

PCT: Active H2O/Na+ adjustment, large molecule/nutrient resorption Thin descend. loop of Henle: Passive H2O diffusion only Thick ascend./DCT: active ion transport, H2O impermeable Collecting duct: H2O, Na+ resorption; active HCO3-/H+ acid/base transport by intercalated A+B cells.

Question 45

Prostaglandins + angiotensin II

Answer 45

Both increase GFR. Prostaglandins increase afferent arteriole diameter, angiotensin increase efferent arteriole diameter

Question 46

RAAS activation by JGA

Answer 46

1. Macula densa cells sense low Na+ in DCT indicating low GFR 2. Macula densa signals JG cells to release renin 3. Renin increases angiotensin II which increases Na+ resorption

Question 47

COX-1/-2

Answer 47

Macula densa signals for prostaglandin increase via COX1/2