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HUMAN EXCRETORY
SYSTEM

Aroha Dahal {AD}

Don’t get confused with neuron
• Q
...


Brain

b
...


Liver

d
...

•Parts of nephron present in cortex and medulla?????
•medulla has multiple triangular renal pyramids
•apex of a renal pyramid is called a renal papilla
...

Each minor calyx is indented by a
renal papilla, the apex of the renal
pyramid, from which the urine is
excreted
...
epithelium
(=urothelium)
Q
...

•Smooth Muscle name:
………………
...
action)
•Sympathetic – detrusor relax causing bladder filling
•First urge to urinate occurs at 150 ml

•Reflex contraction of detrusor occurs at 300-400ml
urine

Sphincters
•Internal urethral sphincter
(@Involuntary)
•Sympathetic – contraction
•Parasympathetic – relaxation
(during urination)

External urethral sphincter
@Voluntary striated muscle) –
controlled according to our will

Urethra
•Transport urine from bladder to
external orifice
•Male : ……………cm
•Female : ………
...
bacteria)

Nephron 1million per kidney
• Structural and functional unit of
kidney
• there are two main types of
nephrons in the kidney; cortical
and juxtamedullary
...

• Parts: Malphigian corpuscle
(body) (which is bowmans capsule +
glomerulus) and tubules

Malphigian corpuscle
• Glomerulus – tuft of
capillaries
…………………
...
Ultrafiltration or Glomerular
filtration
2
...
Tubular secretion

Blood cells and plasma proteins are never filtrated
Filtrate = blood – (blood cells + plasma proteins)
Filtrate = plasma – plasma proteins

Net filtration pressure(10- 15
mmHg)

Glomerular filtration rate
•The amount of filtrate formed per minute
•125ml/min
•Or 180L/day
•Filtration fraction ??
•But urine formed is 1L per day (1- 1
...
Which of the following is not present in filtrate?
a
...
platelets
c
...
All

Tubular reabsorption
• PCT
• Simple cuboidal with microvilli
(brush border epithelium)
• Maximum absorption of solutes
and water (65%)
• 100% reabsorption of glucose,
amino acids and vitamins
• Lots of mitochondria
• Isotonic

Tubular
reabsorption
• LOH (loop of henle)
• Thin limb – simple squamous
• 25% of filtered NaCl and K + is
reabsorbed as well as Ca2+, HCO3 in thick ascending limb
• The ascending limb is impermeable
to water (diluting segment)
...
The descending thin limb
does not reabsorb NaCl
...

•Oliguria-????
•Anuria -???
•Polyuria -???

RAAS

•Ammonotelic : aquatic
•Uricotelic : insects, aves, reptiles
•Ureotelic : human, earthworm



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