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Histology > E3: Urinary > Flashcards

E3: Urinary Flashcards

1
Q

What are the components of the Urinary system?

A

2 kidneys

2 ureters

Bladder

Urethra

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2
Q

What are the functions of the urinary system?

A

Functions:

  • Blood filtration: Removal of toxic waste
  • Protein metabolism (urea), some drugs
  • Water-electrolyte balance: Na+, K+, Ca2+
  • Acid-base balance (pH): H+ and HC03-
  • BP control: Renin-angiotensin system
  • RBC production during hypoxia
  • Vitamin D synthesis
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3
Q

Describe the basic anatomy of the Kidney

A

Renal Anatomy & Function:

Cortex: Initial Filtration

Medulla: Modification of Filtrate

Renal pelvis/Ureter: Drainage of Urine

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4
Q

What is the pathway of Urine flow?

What about blood flow?

A

Urine flow:

Cortex > Medulla > Papilla > Calyces > Pelvis > Ureter

Blood flow:

Renal artery > Cortex > Medulla > Renal vein

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5
Q

ID the tissue in the image.

What does it primarily consist of?

A

Renal Cortex

Primarily consists of PCT’s & DCT’s

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6
Q

What is the functional unit of the Kidney?

What is the composition?

A

Functional Unit: The Nephron

Components:

1. Renal corpuscle (filter)

  • Glomerulus + capsule

2. The renal tubules:

  • Tubules specialized for absorption/secretion
  • PCT, loop of Henle, DCT

3. Collecting ducts

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7
Q

The Renal Corpuscle is composed of what?

Describe it’s formation

A

Renal Corpuscle = Glomerulus & Capsule

Glomerulus Formation:

  1. Renal artery splits into numerous arterioles
  2. Each afferent arteriole splits into fenestrated capillaries, which form a knot (the glomerulus)
    * Blood leaves via the efferent arteriole

Capsule Formation:

  • Developing renal tubule wraps around the glomerulus, forming Bowman’s capsule
    • Visceral layer: Lines glomerular capillaries
      • Podocyte Layer
    • Parietal layer: Lines the capsule wall
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8
Q

What are the (3) layers of filtration?

A

(3) Layers of Filtration:

  1. Capillary Epithelium (fenestrated)
  2. Glomerular BM
  3. Podocyte Foot processes (epithelial cells of the capsule)
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9
Q

Describe what ultrafiltration is

What molecules can pass through?
Which can’t?

What factors influence permeability?

A

Ultrafiltration:

Glomerulus: a molecular sieve

  • Small molecules can pass
    • Glucose, Na+, K+, H+, Cl-, HC03-
  • Large molecules stay in plasma
    • RBCs, large proteins

Factors that influence permeability:

  1. Hydrostatic pressure of blood
    1. Opposed by osmotic pressure of albumin and other plasma proteins
  2. Size: very little protein can cross
  3. Charge: (BM is negative)
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10
Q

What are podocytes?

What role do they play in Ultrafiltration?

A

Podocytes

  • Pedicels (Foot processes) wrap around Endothelial cells
    • Filtration slits
    • Gap bridged by a slit-diaphragm
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11
Q

ID the tissue in this image

A

Renal Cortex

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12
Q

What are Mesangial cells?

What are their function?

A

Glomerular mesangial cells

  • Located between the capillaries
  • Analogous to Pericytes within vasculature

Function:

  • Support
  • Contractile
  • Similar to pericytes in vessels
  • Regulate glomerular flow
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13
Q

Where does the majority of reabsorption occur?

What are the methods of reabsorption?

A

Proximal Convoluted Tubules (PCT):

  • Cuboidal epithelium with brush border (microvilli)
  • Reabsorbs 80% of filtrate to tissue fluid
  • Diffuses into surrounding capillaries

Methods of reabsorption:

  • Active transport:
    • Glucose
    • Amino acids
    • Vitamins
    • Electrolytes
  • Osmosis: water

Some Urea is reabsorbed into the blood stream via diffusion @ PCT

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14
Q

Where does Vitamin D metabolism & conversion occur?

What is the signal pathway associated with it and what is the net effect?

A

Proximal Convoluted Tubule:

  • Brush border contains vitD receptors
  • Activation triggers hydroxylase synthesis
    • Converts dietary/dermal vit D to active form

VitD functions to Increase Ca2+ absorption from gut

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15
Q

How does the kidney regulate blood oxygen content?

A

Renal Cortex:

Hypoxia (Low O2 levels)

> Triggers peritubular fibroblasts in the cortex to synthesize erythropoietin (Epo)

> Epo acts on the BM to increase RBC production

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16
Q

What type of epithelium does the Distal Conv. Tubule have?

What special functions occur there?

A

Distal Convoluted Tubule:

  • Epithelium: Simple cuboidal (No brush border)

Homeostatic functions: (hormones involved)

  1. pH balance (H+/HC03-)
  2. salt balance (Na+, K+)
    1. Aldosterone regulated; Na+ & water retention
  3. Ca2+ homeostasis
    1. PTH regulated; promotes Ca2+ reabsorption
  4. BP control (JG apparatus)

Some diuretics inhibit Na & Cl reabsorption in DCT

17
Q

What is the Juxtaglomerular Apparatus?

What is it’s function?

A

Juxtaglomerular apparatus (JG):

  • Specialized structure at vascular pole of glomerulus
  • Includes JG cells & Macula Densa

JG cells: modified Smooth m. in the AA

  • Synthesizes & releases Renin in response to low NaCl levels in DCT (or baroreceptors in the AA)

Macula Densa (MD): modified epithelial cells in the DCT Function

  • Tightly packed cells
18
Q

How does the JG cells regulate stimulate water retention & thus secondarily regulate BP & NaCl balance?

A

Renin-angiotensin-aldosterone system (RAAS):

Decreased BP (reduced GFR):

  • Low NaCl in DCT > sensed by MD
  • MD stimulates JG cells to release Renin into plasma
  • Low bp detected by baroreceptors in the AA
    • Also stimulate JG cells to release renin

Renin

  • Converts plasma angiotensinogen to angiotensin I
  • Angiotensin I converted into angiotensin II by ACE
  • Angiotensin II raises bp by;
    • Directly stimulating vasoconstriction
    • Stimulating aldosterone & ADH release
      • Aldosterone: Stimulates Na+ absorption & K+ excretion @ DCT, which stimulates water retention
      • ADH increases DCT & CD permeability to H2O via aquaporins, stimulating Water retention
19
Q

What is the arrow pointing to?

A

Macula Densa

20
Q

What primarily occurs in the Renal medulla?

What is the primary portion of the tubules in the Medulla?

Describe them

A

Reabsorption of more salt & water from urine

Henle’s loop:

  • Makes interstitial fluid in the medulla hypertonic (‘salt bath’)

Descending limb:

  • Impermeable to ions
  • Water retention via Osmosis

Ascending limb:

  • Pumps Na+ and Cl- ions into surrounding tissue
  • Larger diameter due to energy needs for active transport
  • Water doesn’t follow because it’s impermeable to water
21
Q

Describe the Collecting Ducts

A

Collecting Ducts:

  • Epithelium: Simple cuboidal
  • Function:
    • Further concentrates urine
    • Water reabsorbed by aquaporins (ADH-regulated)

With a High salt meal;

  1. Plasma Na+ increases
  2. Detected by osmoreceptors in hypothalamus
    1. Triggers ADH release
  3. ADH induces;
    1. Increased water retention by CDs
    2. Increased plasma volume
  4. Resulting in Scant urine
22
Q

Describe the pathway of urine drainage from the renal pelvis

What kind of epithelium is found here?

Trend in Muscularis Propria?

A

Pathway: Renal pelvis > Ureter > Bladder

Epithelium: Transitional

  • St. cuboidal or st.sq (depending on distension)

Muscularis propria:

  • Increasing amounts of SM
23
Q

What is this image of?

A

Ureter

24
Q

Describe the Bladder histologically

Where are the sphincters located?

A

Bladder:

  • Transitional epithelium
  • Wall: bands of Smooth m.

Sphincters:

Internal urethral sphincter (IUS):

  • Provides involuntary control of urination

External urethral sphincter (EUS):

  • Provides voluntary control of urination
25
Q

ID the image

What muscle is present here?

A
26
Q

How do mouse & human bowman’s capsule differ?

A

Mouse: Parietal layer shows sexual dimorphism

  • Females: Squamous
  • Males: Cuboidal

*Proteinuria is normal in mice

27
Q

Where is the kidney Cortex?

Top or bottom half?

A

Bottom half

28
Q

What’s the most likely problem with this biopsy?

  • Psoriasis
  • Melanoma
  • Ringworm
  • Bullous Pemphigoid
A

Melanoma

29
Q

What part of the urinary system is this?

  • Glomerulus
  • Renal Corpuscle
  • Ureter
  • Collecting Duct
  • Loop of Henle
  • Minor Calyx
A

Ureter

Histology (11 decks)

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