Block 4: Histology 10/18, 10/19 - Urinary System

Front 1

What is the primary function of the kidneys? Other functions?

Back 1

Primary function: Maintain Whole-body Homeostasis

Other functions:
Acid-base balance
[Electrolyte] regulation
BV control
BP control

Front 2

What is the basic structural and functional unit of the kidney?

Back 2

The nephron

Front 3

What is the epithelial lining of the nephron?

Back 3

Simple squamous

Front 4

Nephrons occupy wedges in the kidney. Which way do the apices of these wedges face?

Back 4

Wedges face the hilum (toward the center)

Front 5

Is Bowman's capsule found in the cortex or medulla of the kidney? What structure does Bowman's capsule embrace?

Back 5

Cortex

Bowman's capsule embraces glomerular capillaries

Front 6

What cells line the outer, parietal side of Bowman's capsule? The inner, visceral side?

Back 6

Out, parietal = Simple Squamous
Inner, visceral = podocytes with foot processes

Front 7

What is the function of the Proximal Convoluted Tubule?

What is its epithelial lining?

Back 7

PCT: Reabsorbs most minerals and nutrients from tubular fluid and passes them into peritubular capillaries

Epithelial lining: Simple cuboidal with BRUSH BORDER of microvilli

Front 8

Where in the kidney is the Loop of Henle located? What is its function?

Back 8

In Medulla

Fn: Aids in concentration of urine by creating a HYPERTONIC saline environment in medulla

Front 9

Describe the changes in epithelial composition and girth in the Loop of Henle.

Back 9

Descending limb: Initial short, thick segment that is structurally similar to PCT
Followed by long thin segment lined with SIMPLE SQUAMOUS epithelium

Ascending limb:
Thin portion with simple squamous
Followed by thick segment with cuboidal epithelium

Front 10

Would you expect to see glomerular capillaries when looking at a slide of the Loop of Henle?

Back 10

No, because Loop is in Medulla. Glomeruli are in Cortex.

Front 11

What is the function of the Distal Convoluted Tubule? How would you distinguish it from the PCT histologically?

Back 11

Function: Continues return of useful materials from filtrate to blood in peritubular capillaries

Lined with simple cuboidal epithelium (as is PCT), but the DCT LACKS a brush border

Front 12

What is the function of the Collecting Duct? In what area of the kidney are they located?

Back 12

Collecting Duct "collects" urine from DCT

Located in Medulla

Front 13

How would you identify a Collecting Duct histologically?

Back 13

Lined by simple cuboidal epithelium and have distinct cell borders.

If on a slide, would only be able to compare with Loop of Henle (CT and Loop of Henle go really deep into medulla)

Loop of Henle is simple squamous at that point (thin).
CD is simple cuboidal and a lot wider.

Front 14

Describe the flow of urine from Collecting Ducts to Ureters.

Back 14

CD-->Papillary Ducts-->Renal Pelvis-->Ureters

Front 15

Describe the portal system employed by the kidney.

Back 15

First capillary bed: Glomerulus
Second capillary bed: VASA RECTA or PERI-TUBULAR CAPILLARY PLEXUS (PCTP) via efferent artery

Vasa Recta (straight arteries) are important in maintaining osmotic gradient in the medulla.

Front 16

What glomerular features allow for ultrafiltration?

Back 16

-Glomerulus is extensively convoluted and contains fenestrated capillaries WITHOUT diaphragms

-Visceral layer of Bowman's Capsule has podocytes with foot processes that encircle basement membrane

Front 17

What comprises the basement membrane of the Glomerular Capillary - Bowman's Capsule interface?

Back 17

-Basement membrane = basal laminae of podocytes plus basal lamina of glomerulular epithelium

Front 18

What about podocytes contributes to filtration?

Back 18

Each podocyte has pedicels (foot processes) which rest on filtration membrane. Between adjacent pedicles are gaps called FILTRATION SLITS which permit free passage of fluid filtrate into Bowman's space.

Front 19

Where does reabsorption of nutrients occur?

Back 19

PCT

Front 20

Where does most reabsorption of water occur?

Back 20

PCT

Front 21

Where does Na+/K+ regulation occur?

Back 21

DCT

Front 22

What cells does ADH mediate its effect on? What is the effect of ADH?

Back 22

ADH = Anti-Diuretic Hormone; increases permeability of DCT duct cells to water, which makes urine more concentrated.

Front 23

What are Juxtaglomerular cells?

Back 23

JG-Cells are specialized SMOOTH MUSCLE cells that are located within walls of afferent arterioles near point where they enter glomeruli.

They secrete RENIN.

Front 24

What comprises the Juxtaglomerular apparatus?

Back 24

JG Cells and MACULA DENSA

Front 25

What is the macula densa? Function?

Back 25

Area of closely packed cells lining DCT at point of return of nephron to vascular pole of parent glomerulus.

Fn: Detect ionic content and H2O volume of fluid in DCT, can promote renin secretion by JG cells.

Front 26

Describe how the Renin-angiotensin-aldosterone system regulates blood pressure?

Back 26

Angiotensin is made by the liver
Angiotensin-->Ag I via RENIN (JG cells)
Ag I --> Ag II via ACE enzyme from lung
Ag II promotes ALDOSTERONE secretion by adrenal cortex

Aldosterone promotes Na+ reabsorption by DCT, leading to water retention and maintaining BP

Front 27

What is the epithelial lining of the ureters? What ducts give rise to the ureters?

Back 27

Transitional

Papillary Ducts join to give rise to ureter

Front 28

What shape are transitional cells in when they're relaxed?

Back 28

Dome-shaped!