Renal System

Question 1

Functions of Kidney.

Answer 1

• Excretion of metabolic waste products and foreign
chemicals
• Regulation of water and electrolyte balances
• Regulation of body fluid osmolality and electrolyte
concentrations
• Regulation of arterial pressure
• Regulation of acid-base balance
• Regulation of erythrocyte production
• Secretion, metabolism, and excretion of hormones
• Gluconeogenesis

Question 2

Renal blood supply

Answer 2

•22% of cardiac output or 1100ml/min.
•renal-interlobar-arcuate-interlobular- afferent-glomerular-efferent-peritubular
• glomerular capillary -60mmHg
peritubular capillary- 13mmHg
•interlobular-arcuate-interlobar-renal

Question 3

Micturition

Answer 3

•Process by which urinary bladder becomes empty when it gets filled.
•First the bladder fills progressively until the tension in bladder arises above threshold level.
• Second is nervous reflex called micturition reflex which empties the bladder or create a desire to urinate.

Question 4

Composition of Urinary bladder

Answer 4

Composed of body in which urine collects and neck which opens into posterior urethra through which urine passes out.
Smooth muscle of bladder is called detrusor muscle whose cells are fused so action potential travels easily without resistance and it’s contraction can increase the pressure in bladder by 40 to 60 mm of Hg.
Posterior wall of bladder has trigome whose lower most apex opens into posterior urethra and the two uppermost angles of which gives opening to ureters.
Trigome has smooth mucosa whereas rest of wall of bladder has folds called rugae.
Posterior urethra has elastic tissue with muscles called internal sphincter which further continue into urogenital diaphragm which contains external sphincter which is made of skeletal muscle.

Question 5

Innervation of bladder by nerves.

Answer 5

Sympathetic fibers (L2) innervate the body of bladder with trigome .
Parasympathetic innervate bladder and posterior urethra and pudendal nerve innervates external sphincter both S2toS4.

Question 6

Facilitation or Inhibition of Micturition by the Brain

Answer 6

Micturition reflex is autonomic spinal cord reflex but can be controlled by centres present in pons and cerebral cortex.
These higher centres control micturition as follows.
1) Keep micturition reflex partially inhibited except when desired to micturate.
2) The higher centers can prevent micturition, even if the micturition reflex occurs, by tonic contraction of the external bladder sphincter until a convenient time presents itself.
3) When it is time to urinate, the cortical centers can facilitate the sacral micturition centers to help initiate a micturition reflex and at the same time inhibit the external urinary sphincter so that urination can occur.

Voluntary urination is usually initiated in the following way: First, a person voluntarily contracts his or her
abdominal muscles, which increases the pressure in the bladder and allows extra urine to enter the bladder neck
and posterior urethra under pressure, thus stretching their walls. This action stimulates the stretch receptors,
which excites the micturition reflex and simultaneously inhibits the external urethral sphincter. Ordinarily, all the urine will be emptied, with rarely more than 5 to 10 milliliters left in the bladder.

Question 7

Abnormalities in micturition

Answer 7

1) Atonic Bladder caused by Destruction of Sensory Nerve Fibers.

2) Automatic Bladder Caused by Spinal cord damage above the Sacral Region.

3) Uninhibited Neurogenic Bladder Caused by Lack of Inhibitory Signals from the Brain