Pulm/Renal - Histology - Urinary System Flashcards by Jason Worley

What are some of the general functions of the kidneys?

Waste excretion;

BP regulation;

blood acid-base regulation;

hormone production;

vitamin D production

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Name the relevant changes in artery from the renal artery to the glomerulus and subsequent capillary beds.

Renal a. –>*
segmental a. –>*
interlobar a. –>*
arcuate a. –>*
interlobular a. –>*
afferent arteriole –>*

glomerulus –>

efferent arteriole –>

peritubular capillaries (cortex)

vasa recta (juxtamedullary)

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Describe what vessel changes occur after blood passes through the peritubular capillaries (cortical) and/or vasa recta (juxtamedullary).

Either:

Peritubular capillaries (cortical)

Or:

vasa recta (juxtamedullary)

–>*
interlobular v. –>*
arcuate v. –>*
interlobar v. –>*
renal v.*

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What section of tissue is shown here?

The renal cortex, medullary rays, and medulla

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What is a renal corpuscle?

A histological section containing the glomerulus and Bowman’s capsule

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What is the order of a nephron?

(See attached image for more detailed description)

Bowman’s capsule –>

PCT –>

Loop of Henle (descending and ascending) –>

DCT –>

Collecting duct

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What cells form the visceral layer of the glomerular capsule?

What contractile cells are also found in this region?

Podocytes;

mesangial cells

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What is the glomerulus in terms of type of blood vessel?

A bed of fenestrated capillaries

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What is the parietal section of the glomerular capsule?

Bowman’s capsule

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What is unique about the fenestrated capillaries of the glomerulus?

The lack of a fenestration diaphragm;

presence of a nephrin-containing glomerular slit diaphragm instead

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What space can exists between podocyte foot processes (pedicles)?

Filtration slits

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What are some major proteins and compounds found in the glomerulus basement membrane?

Collagen IV;

fibronectin;

laminin;

heparin sulfate (charge barrier)

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True/False.

Albumin can easily pass through the fenestrations / fenestration slits of the glomerulus.

False.

Although albumin can fit through the slits, it is difficult, and the charge barrier helps prevent it from occurring.

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How large is albumin in Daltons?

68 kDa

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What size proteins can pass through the glomerular filtration slits?

Albumin (68 kDa) or smaller

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What protein is essential to the glomerular filtration slit diaphragm?

Nephrin

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A mutation in nephrin leads to what condition?

A mutation in collagen IV leads to what condition?

Congenital nephrotic syndrome;

Alport’s syndrome

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In order, what structures must a substrate in a glomerulus pass to reach the lumen of the Bowman’s capsule?

The endothelial fenestrations;

the basement membrane;

the podocyte filtration slit;

the podocyte filtration diaphragm

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Which limb of the loop of Henle (ascending or descending) has a thick portion?

Ascending

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Describe the epithelial histology of the proximal convoluted tubule and any distinctive characteristics.

Where are they found?

Simple cuboidal layer with brush border,

luminal debris,

indistinct cellular outlines,

very eosinophilic;

the renal cortex and medullary rays

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What type of renal tissue is this?

Proximal convoluted tubules

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What effect does chronic renal disease (e.g. advanced polycystic kidney disease) have on the blood?

Decreased erythropoeitin release –> normocytic anemia

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Where, specifically, is erythropoeitin produced?

By what type of cell?

The interstitium surounding the PCT and peritubular capillaries;

interstitial fibroblasts

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Which portion of the nephron is involved in vitamin D activation?

Via what enzyme?

The PCT;

1-α hydroxylase

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What enzyme is unique to the PCT? What does it do?

1-α hydroxylase; turns 25-hydroxy vitamin D₃ into 1,25-hydroxy vitamin D₃

**1-α hydroxylase** turns \_\_\_(OH) vitamin D₃ into \_\_\_(OH) vitamin D₃ in the ________________ of the kidney.

25-, 1,25-; proximal convoluted tubule

Activation of 25-(OH) vitamin D₃ into 1,25-(OH) vitamin D₃ occurs in what organelle(s) of the PCT epithelium? Via what enzyme?

The mitochondria; 1-α hydroxylase

What process occurs uniquely in the mitochondria of the renal PCT? Via what enzyme?

Vitamin D activation (25-(OH) vitamin D₃ to 1,25-(OH) vitamin D₃); 1-α hydroxylase

**True/False.** The conversion of vitamin D from 1,25-(OH) vitamin D to 25-(OH) vitamin D occurs in the PCT via the enzyme 1-α hydroxylase.

**False**. The conversion of vitamin D from *25-(OH) vitamin D to 1,25-(OH) vitamin D* occurs in the PCT via the enzyme 1-α hydroxylase.

What type of epithelium is found in the loop of Henle?

Simple squamous cells

What type of epithelium lines the PCT? What type of epithelium lines the loop of Henle? What type of epithelium lines the DCT?

Simple cuboidal, brush border; simple squamous; simple cuboidal, no brush border

For what function are the pumps in the thick ascending loop of Henle responsible?

Pumping sodium out of the tubule

Describe the appearance of the loops of Henle vs. collecting ducts on H&E light microscopy.

After passing the loop of Henle, what mechanism is responsible for all further water and ion regulation in the DCT and collecting duct?

Hormonal action | (e.g. aldosterone, ADH)

How is the DCT different on H&E light microscopy when compared to the PCT?

Slightly smaller cuboidal cells; no brush border; little debris in lumen; (still very eosinophilic, still indistinct cellular outlines, still simple cuboidal)

Identify an example of each of the following in this image: Glomerulus PCT DCT

Glomerulus **(Purple)** PCT **(Blue)** DCT **(Green)**

The macula densa is on the _____ convoluted tubule and communicates with the ________ arteriole.

Distal; afferent

The _________ arteriole interacts with the _______ \_\_\_\_\_\_\_ of the distal convoluted tubule.

Afferent; macula densa

Why is it important that the macula densa (of the juxtaglomerular apparatus) interact with the **afferent** arteriole?

Filtrate flow is regulated according to the speed / concentration of Na⁺in the DCT

What are the three portions of the juxtaglomerular apparatus?

**The macula densa** (DCT); **juxtaglomerular smooth muscle cells** (afferent arteriole); **extraglomerular mesangial cells** (outside the renal corpuscle)

Identify the macula densa and extraglomerular mesangial cells in this image. ## Footnote *(Note: both are part of the juxtaglomerular apparatus.)*

**Scenario**: the macula densa senses a high concentration of NaCl in the DCT. What does this indicate, and how does the juxtaglomerular apparatus respond?

The flow of filtrate is too rapid; the afferent arteriole constricts, reducing bloodflow into the glomerulus

**Scenario**: the macula densa senses a low concentration of NaCl in the DCT. What does this indicate, and how does the juxtaglomerular apparatus respond?

The flow of filtrate is too slow; the afferent arteriole relaxes, increasing bloodflow into the glomerulus

What can juxtaglomerular cells (modified smooth muscle) release in response to low blood pressure?

Renin

What organ releases angiotensinogen? What organ releases renin? What organ releases angiotensin-converting enzyme? What organ releases aldosterone?

Liver; kidney; lung; adrenal zona glomerulosa

Describe the portions of the renin-angiotensin system released by each of the following: ## Footnote **Kidney** **Lung** **Adrenal zona glomerulosa** **Liver**

Renin ACE Aldosterone Angiotensinogen

What main hormone-releasing functions does angiotensin II perform? What main vascular and ionic functions does angiotensin II perform?

**Stimulates aldosterone synthase** in the zona glomerulosa of the adrenal gland; **stimulates ADH release**; **stimulates** **AT1R** receptors to cause **arteriolar vasoconstriction**; **stimulates NaCl reabsorption** in the PCT

What main hormone-releasing functions does angiotensin II perform?

**Stimulates aldosterone synthase** in the zona glomerulosa of the adrenal gland; **stimulates ADH release**;

What main vascular and ionic functions does angiotensin II perform?

**Stimulates** **AT1R** receptors to cause **arteriolar vasoconstriction**; **stimulates NaCl reabsorption** in the PCT

What location(s) of the nephron is(are) targets for aldosterone?

The ascending limb of the loop of Henle; the DCT; the collecting duct

What three stimuli activate the tubuloglomerular feedback system (juxtaglomerular apparatus)?

1. Hypovolemia 2. Hypotension 3. Decreased Na⁺ in the DCT

What process is the main regulator for the GFR?

Na⁺ reaching the macula densa

What location(s) of the nephron is(are) targets for ADH?

The collecting tubule (late DCT) and collecting duct

What are the two main cell types of the collecting ducts? What general function does each perform?

**Principal cells (light-staining) (more)** - water reabsorption via aquaporin₂ (ADH-regulated) **Intercalated cells (dark-staining) (fewer)** - secrete H⁺ and absorb HCO₃^-

Describe the histology of the collecting ducts.

Simple cuboidal cells, becoming taller towards the papilla; clear borders between cells (as opposed to PCT or DCT) principal cells (light-staining); intercalated cells (dark-staining)

Identify the renal structures in the image.

1 - Collecting ducts 2 - Loop of Henle 3 - Vasa recta

What is the name of the capillary bed feeding the nephron? What is the name of the capillary bed surrounding the collecting duct? What is the name of the capillary bed surrounding the PCT and DCT?

Glomerulus; vasa recta; peritubular capillaries

Describe the urothelium histology.

Transitional epithelium + 2-3 layers of smooth muscle + connective tissue

What is the term used to describe the luminal layer of transitional epithelium in the ureters/bladder/urethra?

Umbrella cells

What three structures are characterized by urothelium *(transitional epithelium + 2-3 layers smooth muscle + connective tissue)*?

The ureters, bladder, and urethra

How long is the average female urethra? How long is the average male urethra?

5 cm 20 cm

What structure is this most likely to be?

A ureter

**True/false.** Both male and female urethras transition from urothelium to non-keratinized stratified squamous epithelium. Female urethras are mostly stratified squamous epithelium.

True.

Identify structures A - D and the structure outlined by arrows in this micrograph.

**A** - Macula densa **B** - Glomerular capillary **C** - Urinary space **D** - PCT **Arrows** - Bowman's (parietal glomerular) capsule

Identify the structures in the micrograph.

**A** - Medullary ray **B** - Cortical labyrinth **C (and arrows)** - Renal corpuscle **D** - Proximal convoluted tubule

Identify tissue layers A and B.

**A** - Lamina propria (smooth muscle + connective tissue) **B** - Transitional epithelium

Identify structures A - D in the micrograph.

**A** - Collecting duct **B** - Thick limb of the loop of Henle **C** - Vasa recta **D** - Thin loop of Henle

Identify structures A - E in the micrograph.

**A** - Urinary pole **B** - Urinary space **C** - Proximal convoluted tubule **D** - Distal convoluted tubule **E** - Glomerulus covered by visceral layer of glomerular capsule

Identify the structures in this transmission electron micrograph of a portion of the kidney.

**A** - Podocyte **B** - Lumen of capillary **Arrows** - Pedicels of podocytes **Astericks** - Glomerular basement membrane

Identify the structures in this transmission electron micrograph of a portion of the kidney.

**A** - Podocyte **B** - Urinary space **C** - Capillary with RBCs

Identify the marked structures in this micrograph of the kidney.

**A** - Medullary ray **B** - Collecting duct **C** - Thick descending limb of the loop of Henle **D** - Thick ascending limb of the loop of Henle

Identify the renal structures in this transmission electron micrograph.

**A** - Process of podocyte **Arrows** - Pedicels **Astericks** - Glomerular basement membrane

Identify the structures in this micrograph.

(Renal corpsucle) **A** - Urinary pole **B** - Vascular pole **Arrowheads** - Macula densa **Arrows** - Parietal layer of glomerular capsule

Identify the organ in this micrograph.

A ureter

What are some examples of endocrine hormones produced by the kidney?

EPO, renin, prostaglandins

What are the two ends of the renal corpuscle?

The **vascular** **pole** (arterioles of the glomerulus) and **urinary** **pole** (Bowman's capsule leading into the PCT)

Where is the glomerular slit diaphragm?

Between podocyte foot processes ## Footnote *(NOT at the capillary fenestrations like you would expect)*

Proteinuria is seen in \_\_% of both types of diabetes mellitus, usually within 12 - 22 years following diagnosis. Of what is this predictive as a prognosticator?

50; chronic renal failure or ESRD within 4 -5 years

Describe some of the features of diabetic glomerulosclerosis.

- Thickened capillary basement membranes - Diffuse glomerulosclerosis - Nodular glomerulosclerosis (Kimmelstiel-Wilson lesions)

What kidney pathology is shown in this micrograph? As a result of what? What is another name for the hyaline nodule?

Diabetic glomerulosclerosis (diffuse and nodular); type I or II diabetes mellitus; a Kimmelstiel-Wilson lesion

What is the most common cause of most primary glomerulopathies?

Immune mechanisms

The following are examples of _____________ glomerulopathies. - Acute diffuse proliferative glomerulonephritis (poststreptococcal) - Rapidly progressive (crescentric) glomerulonephritis (RPGN) - Focal segmental glomerulosclerosis (FSGS) - Membranoproliferative glomerulonephritis (MPGN) - IgA Nephropathy

Primary | (often immune mechanisms)

The following are examples of causes of __________ glomerulopathies. ## Footnote - Systemic Lupus Erythematous - Diabetes Mellitus - Amyloidosis - Goodpasture’s Syndrome - Bacterial Endocarditis - Fabry’s disease (X-linked inheritance, buildup of globotriaosylceramide)

Secondary (often systemic vascular or metabolic conditions)

Is the PCT brush border ever visible on light microscopy?

Yes.

What is acute tubular necrosis? What effect does it have on renal function?

A rapid destruction of proximal tubular epithelial cells due to a variety of causes - may be fully reversible if the basement membrane is intact; rapid suppression (\< 24 hours)

What are two examples of polycystic kidney disease? When does each manifest?

ADPKD (between 30 and 40 years of age); ARPKD (less common; shortly after birth)

Name two types of benign renal tumor.

**Oncocytoma** (incidental in the elderly); **angiomyolipoma** (often in patients with tuberous sclerosis)

What is the most common form of renal malignancy? In which gender is it more common?

Renal cell carcinoma (clear cell being the most common subtype); males (3:1)

Renal cell carcinomas may extend into what nearby hematogenous structure(s)?

The renal v. and vena cava

What renal disorder is shown in this micrograph?

Renal clear cell carcinoma ## Footnote *(clear cytoplasm and are arranged in nests with intervening blood vessels)*

**True/False.** Urothelial (transitional cell) carcinomas are the 8th most common malignancy in men and the 4th most common malignancy in women.

**False**. Urothelial (transitional cell) carcinomas are the _4th_ most common malignancy in men and the _8th_ most common malignancy in women.

In what age group are urothelial (transitional cell) carcinomas most common? What are the typical presenting S/Sy?

≥ 60; **painless** **hematuria**; also infection or obstruction

Urothelial (transitional cell) carcinomas can occur in what organs?

The renal pelvis, ureters, bladder, urethra

# Define renal lobe.

Pyramid + associated cortical tissue

Define renal lobule.

Medullary ray + associated cortical tissue

**True/False**. The parietal layer of Bowman's capsule is a simple squamous epithelial layer.

True.