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Histology Block 3 > Urinary Apparatus > Flashcards

Urinary Apparatus Flashcards

1
Q

Describe the Kidney structure from a longitudinal cut.

A
  • organization into Renal pyramids separated by renal columns (lobe organization)
  • Medullary region and cortical region.
  • medullary rays!
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2
Q

What are the surface features of the Kidney?

A
  • Hilus
  • Ureter
  • Pelvis
  • Papilla
  • Collecting Ducts perforating each papilla ducts
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3
Q

What are medullary rays?

A

Extensions of the medulla into the cortex (contains aggregation of straight tubules and collecting ducts).

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4
Q

What surrounds the medullary rays?

A

Cortical Labyrinths (contains renal corpuscles and associated proximal and distal convoluted tubules)

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5
Q

What are the components of a Nephron?

A

Renal Corpuscle
Proximal Convoluted Tubule (PCT)
Loop of Henle (Thin and Thick segments)
Distal convoluted Tubule (DCT)

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6
Q

Describe the Renal Corpuscle and the structures it contains.

A

Contains Bowman’s Capsule in parietal/visceral layers Capillaries invade the Capsule through its visceral layer.

(Balloon example from class)

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7
Q

What are the 3 types of Nephrons discussed?

A

Subcapsular/Cortical

  • renal corpuscle in outer cortex
  • short loops of Henle pass to outer medulla

Juxtamedullary

  • renal corpuscles near cortico-medullary junction
  • long loops pass to inner pyramid

Intermediate/Midcortical

  • renal corpuscles in mid-region of cortex
  • loops are intermediate length
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8
Q

Describe the polarity of the Renal Corpuscle.

A

There is a Vascular Pole, where the capillaries bring blood in/out and the Efferent/Afferent Arterioles communicate with the Capsule.

There is a Urinary Pole, where the ultrafiltrate that is the precursor to urine is ultimately drained into the PCT.

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9
Q

What is the space containing the ultrafiltrate called?

A

Bowman’s Space.

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10
Q

How do you differentiate between an Afferent Arteriole and an Efferent Arteriole in the Renal Corpuscle?

A

The diameter of the Afferent Arteriole is greater than that of the Efferent.

Note: This should clue you into the pressure gradient inherently present in the Capsule.

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11
Q

What cell types comprise the visceral layer of Bowman’s capsule?

A

Podocytes.

  • Major processes (extend from nuclear region)
  • Minor processes (extend from Major processes)
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12
Q

What special feature do the podocytes give the Capsule?

A

Due to their interdigitation, they offer another layer of filtration on top of the fenestrated epithelium and the basal lamina.

The structure in between each podocyte is called a filtration slit diaphragm.

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13
Q

What are the layers of filtration between the capillaries and Bowman’s space?

A

Fenestrated Epithelium
- restricts blood cells and other formed elements

Basal Membrane of capillaries
- restricts movement of particles larger than 70 kD like hemoglobin

Slit membrane in filtration slits
- physical barrier to free diffusion

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14
Q

What are the factors that cause ultrafiltration to occur?

A
  • Pressure gradient (afferent arteriole > efferent arteriole)
  • large surface area for filtration
  • barrier separating blood from Bowman’s Space is very thin
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15
Q

How do the filters stay ‘clean’?

A

Mesangial cells actively maintain the filters through phagocytosis, contraction, secretion of cytokines and growth factors, and structural support.

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16
Q

What are the functions of the Juxtaglomerular Apparatus? What are its two major components?

A

Regulation of blood pressure via renin-angiotensin-aldosterone system, acts as both baroreceptor and chemoreceptor.

AKA: Regulate BP and regulate salt levels!

Macula Densa and Juxtaglomerular Cells

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17
Q

Where is the Macula Densa? What is its specific function?

A

Region at the end of the distal straight tubule. It samples Na+ concentration of tubular fluid (ultrafiltrate)

18
Q

Where are the Juxtaglomerular Cells? What is their specific function?

A

They are smooth muscle cells in tunica media of the Afferent Arteriole. They synthesize/secrete/store Renin, the protease that cleaves angiotensin.

19
Q

What is the Proximal Tubule (PT), and what is its function? Describe some of its characteristics as well.

A

It is the tube that begins at the urinary pole of the Renal Corpuscle. It has a straight portion and a convoluted portion

It is the major site of resorption (proteins, amino acids, and glucose). It is lined with a single layer of cuboidal cells a brush border and folds to increase its surface area.

CONSTITUTES BULK OF RENAL CORTEX and ONLY runs in the cortex.

20
Q

What is actively transported in the PT?

A

NaCl (water will follow through aquaporin type 1)

21
Q

Is the Collecting Duct part of the Nephron?

A

NOPE.

22
Q

How does one differentiate the PCT from the Distal Convoluted Tubule (DCT) on a slide?

A

PCT will still contain matter in its lumen (process of resorbing), while DCT lumen will be clear.

23
Q

What is the Loop of Henle comprised by?

A
  • Straight part of the proximal tubule in descending limb
  • thin segment in descending and ascending limbs
  • straight part of the distal tubule in ascending limb.
24
Q

Is there active transport in the Loop of Henle?

A

No, it requires no ATP.

25
Q

Describe the permability of various regions of the Loop of Henle to water and NaCl.

A

Descending thin loop:

  • Permeable to water
  • Low permeability to NaCl

Ascending thin loop

  • Impermeable to water
  • High permeability to NaCl
26
Q

Describe the thick segment of the ascending portion of Loop of Henle.

A
  • Squamous cells -> Cuboidal cells
  • Macula Densa formed!
  • Basal infoldings with mitochondria (indicative of active transport)
  • NO BRUSH BORDER
  • Active transport of Na+ from urine to Interstitium (other ions resorbed as well: Cl-, K+, Ca2+, Mg2+)
27
Q

What is the Distal Convoluted Tubule (DCT)?

A

Begins at macula densa and empties into collecting tubule which empties into the collecting duct.

Resorbs Na+, which is followed by water. (Note: Aldosterone will increase Na+ resorption). K+ secreted into lumen to maintain ionic equilibrium.

Urine becomes acidic from H+ secretion and Bicarbonate resorption.

28
Q

What are Collecting Ducts? Describe their location and structure.

A

Collecting tubules from the Nephron will empty into Collecting Ducts: long ducts that descend in Medullary Rays into the Medulla, where several collecting ducts will join to form larger Papillary Ducts.

29
Q

Where do Papillary Ducts drain?

A

Into the apex of a Papilla, which opens into minor Calyx at the Area Cribrosa.

30
Q

How do you identify the different cells of the Collecting Duct’s epithelium?

A

Lighter cells contain Aquaporins

Darker cells secrete H+ or Bicarb as required.

31
Q

What is the Area Cribrosa?

A

The “tip” of a Renal Pyramid where all the capillaries/collecting ducts(?) empty into the Minor Calyx.

32
Q

Describe the Blood Supply of the Kidney.

A

Renal Artery -> Segmental Arteries -> Interlobar Arteries -> Arcuate Arteries -> Interlobular Arteries -> Afferent Arterioles -> NEPHRON -> Venules -> Interlobular Veins -> Arcuate veins -> Interlobar Veins -> REnal Veins.

33
Q

What happens to Efferent Arterioles?

A

They arise from the Glomeruli and give rise to a Peritubular Capillary Network in Cortical Nephrons, and Vasa Recta in Juxtamedullary Nephrons.

34
Q

What happens in the Countercurrent Exchange System for blood?

A

Arterial side of the Loop will lose water to/gain salt from the interstitium. Venous side of the Loop will lose salt to/gain water from the Interstitium.

This occurs WITHOUT energy expenditure.

35
Q

What fibers is the Renal Plexus mostly composed of?

A

Sympathetic division. They cause contraction of vascular smooth muscle and consequent vasoconstriction.

36
Q

What does constriction of the Afferent/Efferent Arterioles do to Urine production?

A

Afferent constriction = reduce (due to less blood flowing in)
Efferent constriction = increase (due to increased resistance of flow out)

37
Q

Describe the flow of urine.

A

Renal Papilla -> Minor Calyx -> Major Calyx -> Renal Pelvis -> Ureter -> Bladder -> Urethra

38
Q

All the excretory structures of urination have what three layers?

A

Mucosa (very thin lamina propria)
Muscularis
Adventitia

Note lack of Submucosa

39
Q

What is Transitional Epithelium?

A

Specialized epithelium that resists any kind of absorption of salts and water and allows for distensibility, especially in ureter and bladder.

2-3 cells thick at level of Calyces
4-5 cells thick in ureter and bladder.

Note: you can observe binucleation in some cells.

40
Q

Describe a cross-section of the Ureter.

A

Muscularis Externa is opposite of GI tract: Inner layer is Longitudinal, Outer Layer is Circular.

Lumen is stellate.

41
Q

Describe the Bladder walls.

A

There is a lot more smooth muscle in the walls of the Bladder (3 Layers), particularly a prominent middle layer. Fusiform Vesicles in the Bladder walls will ‘unfold’ into the epithelial layer when the Bladder needs to distend, giving more surface area to the wall.

42
Q

Compare the Male and Female Urethras.

A

Male: 20 cm long with 3 distinct segments

  • Prostatic: 4 cm
  • Membraneous: 1 cm
  • Penile: 15 cm

Note: Stratified/Psuedostratified Columnar in Membraneous and Penile Urethra

Female: 3-5 cm long
- epithelium goes from transitional to stratified squamous epithelium.

Histology Block 3 (10 decks)

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