Microscopic Kidney

Question 1

Kidney Lobation for different species

Answer 1

-Unilobar: carnivores and horse
-Multilobar (multipyramidal; lacking renal pelvis): ox and pig

Question 2

Kidney Cortex

Answer 2

-outer layer
-cortical labyrinth containing convoluted tubules
-Medullary rays present containing straight tubules and collecting ducts

Question 3

Kidney Medulla

Answer 3

-inner layer
>outer zone: subdivided into outer and inner stripes
>inner zone: deepest region

Question 4

Kidney functions

Answer 4

-filtration
-secretion
-reabsorption
-excretion
-water balance
-acid-base balance
-hormones/blood pressure

Question 5

Nephrons

Answer 5

-structural and functional unit of kidney
- no new nephrons formed after renal maturity (which occurs several weeks after birth in carnivores and pigs)

Question 6

Nephrons in dog vs. cat

Answer 6

Dog: 400,000
Cat: 200,000

Question 7

Nephron classification

Answer 7

-based on location (superficial, mid-cortical, juxtamedullary
-based on length (long looped or short looped

Question 8

Renal tubule

Answer 8

-includes both the classical nephron and the collecting ducts

Question 9

Renal corpuscle

Answer 9

-includes both glomerulus and the Bowman’s capsule

Question 10

Parts of renal tubule

Answer 10

-PCT/PST
-thin ascending loop of Henle
-thin descending loop of Henle
-DCT/DST
-Collecting tubule
-Collecting duct

Question 11

Where is the renal corpuscle located?

Answer 11

-the cortical labyrinth

Question 12

Parts of glomerulus

Answer 12

-Capillary tuft
-Mesangium
-Glomerular Basement Membrane

Question 13

Capillary tuft

Answer 13

-several loops of branching and anastomosing capillaries
-porous capillaries with 50-150 nm fenestrations
-single afferent and single efferent arteriole

Question 14

How many capillaries are open at a time in the glomerulus?

Answer 14

-only 1/3rd at any given time

Question 15

Mesangium

Answer 15

-forms the core of the glomerulus
-made of mesangial cells and mesangial matrix

Question 16

Mesangium location

Answer 16

located between the glomerular basement membrane and endothelial cells

Question 17

Mesangial cells

Answer 17

-originate from pericytes or smooth muscle
-they are irregular cells with elongated processes. These processes contain microfilaments and connect each other by gap junctions

Question 18

Glomerular basement membrane

Answer 18

-Separates endothelial cells from the podocytes

Question 19

What is the glomerular basement membrane composed of?

Answer 19

-composed of lamina rara interna, lamina densa, and lamina rara externa

Question 20

Bowman’s capsule layers

Answer 20

-Parietal and visceral layers that are continuous at vascular poor

Question 21

Visceral layer of Bowman’s capsule

Answer 21

-formed by podocytes

Question 22

Podocytes

Answer 22

-octopus-like cells surrounding the capillaries
-they give off primary and secondary branches.
>smaller branches (foot processes or pedicels) interdigitate with another cell. The smalle spaces between the pedicels are called filtration slits, and these slits are closed by slit diaphragms

Question 23

Parietal layer of Bowman’s capsule

Answer 23

-formed by simple squamous epithelium

Question 24

Urinary space

Answer 24

-the space between the parietal and visceral layers. This space continues in the lumen of the proximal convoluted tubule at the urinary pole

Question 25

Proximal tubules

Answer 25

-convoluted and straight parts
-begins at urinary pole

Question 26

Proximal vs Distal convoluted tubules

Answer 26

> proximal is much longer than distal

Question 27

Cells of proximal convoluted tubules

Answer 27

-nucleus located in the central or basal part of the cell
-Brush border: long irregular microvilli present
-cells have endocytotic apparatus (vesicles and lysosomes)
-adjacent cells joined by leaky tight junctions
-basal folding present
-high numbers of mitochondria for ATP production

Question 28

Lipid droplets dogs vs. cats

Answer 28

Dogs: lipids found in cells of PST making medullary rays much lighter
Cats: lipids found in cells of PCT making kidneys appear yellowish

Question 29

Where does transition from proximal to thin descending loop of Henle occur?

Answer 29

-level of the outer and inner strip of outer medulla

Question 30

Thin tubule of loop of henle

Answer 30

-descends down in medulla to form a hair pin loop
-lined by simple squamous epithelium
-cell nuclei are round, and protrude in the lumen

Question 31

Distal straight tubule (DST)

Answer 31

-forms the ascending thick segment of loop of Henle and passes at vascular pole of its parent renal corpuscle to form macula densa

Question 32

Distal convoluted tubule (DCT)

Answer 32

-located in the cortical labyrinth
- shorter than PCT

Question 33

Distal tubule cells

Answer 33

-nucleus is located in apical part of cell
-cells lack well developed brush borders of microvilli
-basal folding and mitochondria arrangement similar to proximal tubules
-tight junctions are NOT leaky

Question 34

Arched collecting duct

Answer 34

-connects one to several distal convoluted tubules to the collecting duct in the medullary ray

Question 35

Collecting duct location

Answer 35

-extends throughout the medullary ray, outer medulla, and inner medulla

Question 36

Collecting duct

Answer 36

-opens as papillary duct at tip of the papilla/renal crest
-lined by simple cuboidal epithelium with principal cells and intercalated cells

Question 37

Principle cells

Answer 37

-pale cytoplasm
-straight and prominently stained lateral cell borders
-minimal basal foldings