URINARY SYSTEM
(1) Kidney :
- Paired and Mesodermal in origin
- Right kidney is little over than the left kidney.
- kidney Length = 10-12 cm
- Kidneys are retroperitoneal in arrangement [this means they get fuse with the body wall on dorsal side so peritoneum cover now present only on ventral side].
- Kidneys are located parallel to thoracic and lumbar vertebra.
- Weight of each kidney = 120-170 g
- Each kidney is protected by 3 covering:-
(i) Outermost is fibrous coat called renal fascia.
(ii) Middle is adipose tissue coat which function as cushion or shock absorber.
(iii) Inner is areolar tissue coat also called renal capsule.
Internal structure of kidney :-
- Each kidney has a depression called hilum, through which occurs entry of renal artery, exit of renal vein & ureter, both entry & exit of nerves.
- Internally kidney is divided into outer cortex & inner medulla.
- Medulla consists of 16-17 conical pyramids called medullary/renal pyramids.
- Each pyramid has a broad face facing towards cortex and narrow apex facing towards medulla. This apex called renal papilla.
- Medullary pyramids joint to form about 6-7 minor calyces, which further join to form 2-4 major calyces(join to form a single renal pelvis).
- Renal column of Bertini are the point where cortex seems to enter into medulla.
- The structural & functional unit of kidney is uriniferous tubule(nephron).
- Each kidney has about 1 million nephrons.
(2) Ureter :
- These are thin tubes which bring urine from kidney to the dorsal wall of urinary bladder.
- About 25-30 cm long and internally lined by thin transitional epithelium.
(3) Urinary bladder :
-It is sac like structure which help in temporary storage of urine.
- It receive two opening of ureter, and urethra leave out from here so together they form a triangular mark called trigon.
- Internally bladder is lined by well developed transitional epithelium.
- This epithelium has very high stretchability due to absence of basement membrane, this is the reason why bladder can store larger than normal volume of urine.
- Wall of bladder consists of detrusor muscle.
- Wall of bladder also consist of stretch receptors.
- The opening of bladder is regulated by two sphincter - (i) external sphincter (made up of voluntary muscle) (ii) internal sphincter (made up of involuntary muscle).
- The process of release of urine out from body is called micturition.
(4) Urethra :
- Internally lined by transitional epithelium.
- In human, female urethra is short(2-4cm) So, female are more prone to UTI (urinary tract infection).
- Female urethral opening brings only urine so called urinary opening.
- In human, male urethra is long (16-20cm) So, males are less prone to UTI.
- Male urethra bring urine+semen so it is a common urinogenital opening.
- Semen consists of prostate gland secretion which include natural antibiotic seminoplasmin.