Henle Loop Fenestrated Capillary

Kidney and Urinary System CTB Lab 9

General Kidney Features (macroscopic structure)

Kidney • • • •

Retroperitoneal Encapsulated w/ Dense Irregular CT Cortex  outermost region Cortex composed of – – – –

Renal corpuscles (little circles) Proximal/Distal Tubules Capillaries Medullary rays

Kidney (monkey): RC renal corpuscles V interlobular vein Cx cortex MR medullary ray AV arcuate vein AA arcuate artery

Zoom to ~150% to really see the arteries and veins  G glomerulus IA interlobular artery RP renal papilla C calyx P renal pelvis U ureter Ai interlobar artery T tubule

Renal Corpuscle 1. Glomerulus  tuft of fenestrated capillaries 2. Mesangial cells  modified sm muscle cells, support glomerulus, maybe maintain Glomerular bsmt membrane 3. Bowman’s Capsule  double walled epithelial layer surrounding glomerulus (Visceral + Parietal) Question 1: *Parietal Layer of Bowman’s Capsule is made up of Simple Squamous Epithelial cells Visceral layer of Bowman’s Capsule consists of Podocytes Q2: *Nuclei within Glomerulus belong to 3 types of cells: Capillary endothelial cells, Podocytes, Mesangial Cells

Renal Corpuscle Schematic

Renal Corpuscle

Renal corpuscle: A afferent arteriole C glomerular capillary E endothelial cell GBM glomerular basement membrane I interstitium M mesangium N mesangial cell nucleus PCT proximal convoluted tubule S squamous cell

Glomerular Filter – Schematic Glomerulus BC Bowman's capsule BM basement membrane BS Bowman's space (urinary space) C capillary loop E endothelial cell F fenestrations FS filtration slit M mesangial cell MM mesangial matrix P podocyte P1 podocyte primary process P2 podocyte secondary foot process

Q3: **The Clear Space between the Glomerulus and Parietal Layer of Bowman’s Capsule is called the Urinary Space (Bowman’s Space in Wheater’s diagrams) **The Urinary Space contains Plasma Ultrafiltrate – it passed from capillaries into it.

Q4: **3 Components of the Filtration barrier going from glomerular caps to urinary space: 1) Fenestrated capillary endothelial cells (ECs) 2) Fused basal laminae of cap ECs & podocytes 3) Diaphragm-covered filtration slits between podocyte foot processes

Ultrastructure of Podocytes & Endothelial Cells Glomerulus BC Bowman's capsule BM basement membrane BS Bowman's space C capillary loop E endothelial cell F fenestrations FS filtration slit M mesangial cell MM mesangial matrix P podocyte P1 podocyte primary process P2 podocyte secondary foot process

Slide 27 – Kidney PAS Note intense staining within glomerulus It indicates the Basal Lamina that contributes to the glomerular filtration barrier.

Back to slide 26 Afferent Arteriole  feeds glomerular caps Efferent Arteriole  drains glomerular caps Both enter/exit the renal corpuscle at the Vascular Pole Urinary Pole  opposite from Vascular pole; where plasma ultrafiltrate drains from corpuscle. Q5: **Plasma Ultrafiltrate drains from urinary space into proximal tubule.

1- Renal corpuscle Nephrons – functional units of the kidney, 2- Proximal tubule composed of four things: 3- Loop of Henle 4- Distal Tubule

Proximal and distal convoluted tubules

BB brush border BM basement membrane C peritubular capillaries DCT distal convoluted tubule PCT proximal convoluted tubul

How to Distinguish Renal Tubes Proximal Tubule

Distal Tubule

Collecting Duct

Type of Epithelium

High Cuboidal

Low Cuboidal

In other words, Large cells

In other words, shorter cells

Cuboidal  Columnar

Lumen Characteristics

Occluded Jagged outline

-Open -Wide -Smooth contour

-Open -Scalloped edge b/c cells bulge inward

Indistinct

Indistinct

(lateral borders highly interdigitate)

(lateral borders highly interdigitate)

Few – basally located

Many – centrally located

(because cells are so large)

(beccause cells are smaller)

Many – centrally located

Pale

Pale

Cell borders Nuclei in a given plane of section Cytoplasmic staining Extra info:

Eosinophilic & Granular (b/c abundant mitochondria, basal membrane infoldings) -Have a brush border (microvilli) -More Prox tubules than Distal; so will see more of these in X section

Distinct

-No brush border -Makes lumen appear wider/open

Q6:**Cells in the Proximal Tubule function to resorb lots: Active Reabsorption = Na/Cl Passive Reabsorption = water (follows NaCl) Facilitated Reabsorption = Glucose / AAs / Proteins

Q7: **Distal Tubule Cells only resorbe Na/Cl

B Bowman's space CP mesangial cell cytoplasmic processes MC mesangial cell MM mesangial matrix P1 podocyte primary process P2 podocyte secondary foot process; BM basement membrane BME basement membrane of endothelium Cap capillary E endothelium J junctional complex L lysosome M mitochondrion Mv microvilli P cell processes S supporting tissue V pinocytotic vesicle E endothelial cell

Structure of the Tubules with adjacent capillaries for reabsorption

More Comparison of Proximal vs Distal Tubules

Proximal Tubule (Microvilli and Mitochondria)

MACULA DENSA: Place where the Distal Tubule passes close by the Vascular Pole The Distal Tubule’s Columnar Cells are Tightly Packed here Function: monitors the sodium concentration and volume of ultrafiltrate in the tubule

MACULA DENSA Q7: ** Macula densa is part of a larger structure called the Juxtaglomerular Apparatus, which includes specialized cells in a portion of the afferent arteriole. Q8: ** The secretory product of the juxtaglomerular cells of the afferent arteriole is Renin.

See/Compare: -Glomerulus -Macula densa -Proximal tubule -Distal tubule

“A U-shaped tube connecting the proximal and distal tubules”

First section of Henle’s loop is a thick descending limb; goes from cortex  medulla via Medullary Rays

Loop of Henle (Intermediate Tubule)

Collecting tubules and ducts A thick ascending limb of loop of Henle T thin limb of loop of Henle CD collecting duct CT collecting tubule IC intercalated cell V vasa recta

Thin loops dip down into the medulla and go back up to the cortex.

To identify look for squamous cells, but they shouldn’t have bright RBCs within – those are capillaries.

Don’t forget that Henle’s Loop functions as a Countercurrent Multiplier.

*The nephron stops at the end of the distal tubule.. Doesn’t include the collecting duct. *Don’t fret about distinguishing collecting ducts vs collecting tubules.

Collecting tubules and ducts BM tubular basement membrane CD collecting duct IC intercalated cell S supporting tissue Collecting Ducts have: -Larger lumens -Distinct intercellular borders -Scalloped edges of lumens -Many central nuclei -Pale cytoplasm

*But you will need to be able to distinguish collecting tubules from distal/proximal tubules.

Note how the Thin loops have Squamous epithelium compared to the Cuboidal epithelial cells in the thick desc/ascending loops, and cuboidal/columnar in collecting ducts.

Kidney – Stroma (slide 28) As you can see the stromal component in the kidney is primarily Reticular fibers and not as predominant as in other organs.

Ureter in or your out… Ureter A adventitia C circular muscle layer of ureter L longitudinal muscle layer of ureter LP lamina propria V blood vessel

Slide 30 Q10: Transitional epithelium lines the lumen of the ureter. Q11: Within the muscularis the Inner layer = Longitudinal Outer layer = Circular Therefore the section on slide 30 was taken from the upper 2/3rds of ureter. Q12: This arrangement is opposite of that found in the tubular organs of the GI tract. Hmph.

One more look at the Transitional Epithelium lining the Ureter

Bladder IL inner longitudinal muscle layer of bladder OC outer circular muscle layer of bladder OL outer longitudinal muscle layer of bladder A adventitia Um umbrella cell LP lamina propria

The Bladder Mucosal layer is transitional epithelium – aka, Urothelium. Q13: Fibrous CT composed of Elastin underlies the mucosal layer. The fibers are refractile/pink staining. Q14: Because the bladder is saccular, it has 3 layers of smooth muscle in its walls. (See left)

Q15: When fixed, the bladder in slide 31 was in the relaxed state.

Q16: Approximately 95% of bladder cancers arise from Transitional cell carcinoma. Q17: A reliable reference listing most common causes of cancer in the US population is www.cancer.gov  The US NIH National Cancer Institute homepage.. Most Common Causes of Cancer: Bladder, Melonoma, Breast, Non-Hodgkins Lymphoma, Colon/Rectal, Pancreatic, Endometrial, Prostate, Kidney, Skin, Leukemia, Thyroid, and Lung. Incidence differs by factors including genetics, environmental exposures, etc.