Renal

Question 1

How can the urinary system be split up?

Answer 1

• Upper UT – kidney and ureters

* Lower UT – bladder and urethra

Question 2

List the 6 kidney functions.

Answer 2

• Maintain homeostasis
• Get rid of waste from the blood
• Selectively reabsorb substances
• Conserve water
• Regulate blood pressure
• Stimulate erythrocyte production

Question 3

Describe the position of the kidney.

Answer 3

• Retroperitoneal – in between layer of peritoneum and the dorsal body wall
• In most species, except from the pig, the right kidney is more cranial (left pig kidney is more cranial)
• Hilus transmits vessels, nerves and ureter
• Fibrous capsule – means they cannot swell, which can cause pressure build ups to cause damage o kidney tissue
• Cortex and medulla which are differentiated by colour
• Associated closely with adrenal glands

Question 4

Describe the internal structure of the kidney.

Answer 4

• Outermost edge is the cortex. Granular appearance, where renal corpuscles are found: glomeruli, Bowman’s capsules, proximal and distal convoluted tubules.
• Medulla is more purplish. Has a stratified appearance. Has loops of Henle and collecting ducts.
• These travel down to the parenchyma to renal crest, where urine is collected and exits out through the ureter
• Renal pyramids in the medulla
• Corticomedullary junction is the dark purple junction. It important on ultrasound scans
• Arcuate arteries running through the medulla
• Renal pelvis contains the ureter, which travels through the renal sinus

Question 5

What does it mean when the corticomedullary junction is less defined?

Answer 5

Indicative a disease in the parenchyma or something that is causing tissue damage.

Question 6

Distinguish the lobe and lobular of the kidney.

Answer 6

Lobe of a kidney = the pyramid and its associated cortex. Apex/papilla points towards calyx, which collect urine at the end of the renal pyramid.

Lobule = have renal rays

Question 7

Name the 3 types of kidney. Which species have these kidneys?

Answer 7

Multipyramidal - ox, dolphin, otter, bear
Unipyramidal - canine, feline, equine, sheep
Multipapillate - pig, human

Question 8

Describe the structure of multipyramidal kidneys.

Answer 8

• Clear lobation pattern – no fusion, cortex or medulla. Lobes separated by fissures and there are indentations between the lobes. Each lobe has cortex and medulla.
• Multiple calices
• No renal pelvis, so urine from calices go straight to ureters
• Often covered by a lot of fat, which provides protection from trauma and the other abdominal organs and the pressures they exert.
• In cows, rumen takes up most of the left flank, so the left kidney is pushed over to the midline.

Question 9

Describe multipapillate kidneys.

Answer 9

• Fusion cortex
• No fusion medulla
• Multiple calices with each pyramid with its own calyx
• Minor calices form major calices
• Renal pelvis
• Kidneys are more symmetrical and cranial in position and flattened dorsoventrally in pigs

Question 10

Describe unipyramidal kidneys.

Answer 10

• Fused cortex
• Fused medulla
• Papillae joined in a common crest, the renal crest
• Renal pelvis
• Arcuate and interlobar arteries indicate former lobe/pyramid boundaries

Question 11

Describe canine kidneys.

Answer 11

• Kidneys are bean shaped
• Right kidney is more cranial than the left
• Left in theory is palpable in the live animal but it is hard to do so

Question 12

Describe feline kidneys.

Answer 12

• Smaller than canine
• Stellate/capsular veins over the surface of the kidney
• Can palpate both kidneys
• Less retroperitoneal

Question 13

Describe equine kidneys.

Answer 13

• Hilus more dispersed

- Left is bean shaped, right is more heart shaped

Question 14

Describe ovine kidneys.

Answer 14

• Similar structure to the dog
• Although a different type of kidney to the cow, sheep kidney is still a ruminant kidney with a lot of fat to protect them from the large rumen

Question 15

Describe blood supply to the kidney.

Answer 15

• Renal artery directly off the aorta and enters the hilus of the kidney
• Branches into interlobar arteries
• Arcuate arteries at the corticomedullary junction
• Interlobular arteries come off the arcuate arteries to supply the lobules, forming glomeruli filtration
• Veins follow the arteries
• Unique stellate vein arrangement in cats

Question 16

Describe innervation of the kidney.

Answer 16

• Sympathetic via coeliacomesenteric ganglion

- Parasympathetic via the vagus nerve (CN X)

Question 17

Describe the lower urinary tract.

Answer 17

• Renal pelvis can be thought of as a dilation of the ureter.
• The ureter is a smooth muscle tube under involuntary control
• Urine moved from the kidney to the bladder in peristalsis
• So is an active process
• This is because pressure builds in the bladder as it fills, which would prevent a passive movement of urine down the ureters
• Ureter, bladder and urethra are all made up of transitional epithelium

Question 18

What is the danger of the close association of the uterine horns and ureters?

Answer 18

The uterine horns being dorsal to the ureters. So there is danger of crossover and tying off the ureters in a bitch spay.

Urine cannot drain from the kidney > fluid backlog > kidneys cannot expand with fluid > additional fluid pressure would damage the parenchyma > kidney failure. If this occurs bilaterally, the animal cannot survive.

Question 19

What is the function of the uterovesical junctions?

Answer 19

• Ureter enters the bladder obliquely at dorsal body wall
• As bladder fills, pressure builds and closes off the ureter at the wall
• Long intramural course
• Prevents urine flowing back up the ureter
• Ureters have muscular wall for peristalsis to pump urine due to increased pressure
• This also slows filling of bladder when bladder is full

Question 20

Describe the position of the bladder.

Answer 20

• Very distensible
• Extends inti the abdomen cranially and ventrally when full
• Can be intra-pelvic, which is abnormal

Question 21

What is the function of the detrusor muscle?

Answer 21

Wall of the bladder is made up of detrusor muscle, which is smooth muscle so under involuntary control. Upon urination, the detrusor muscles will contract and it will push the urine out. Increases pressure in the bladder and puts pressure of the walls, which prevents urine being pushed back up to eth ureters during urination.

Question 22

What are the 2 muscular sphincters of the bladder?

Answer 22

External and internal urethral sphincters.

• These sphincters need to relax to allow urine to pass out through the urethra.
• Internal US is a continuation of the detrusor muscle so innervation will cause part of this same muscle to contract and the other to relax.
• External US is under voluntary control and is striated muscle, so it can be consciously contracted to hold in urine. External US is part of the urethralis muscle.

Question 23

What are the cells lining the bladder?

Answer 23

Mucosal lining of the bladder itself is made up of transitional epithelium, sometimes called urothelium, that allows stretch depending how full it is.

Question 24

What is the bladder trigone?

Answer 24

The triangular region between the ureterovesical openings, where the ureters enter and the internal urethral meatus, the channel around the internal urethral sphincter.
This is where most of the bladder associated stretch receptors are found:

• Bladder fills with fluid
• Stretch receptors are stretched as the transitional epithelium expands to contain the increased fluid volume
• This sends signals bac to the CNS to trigger urination