The document discusses the urinary system. It defines the urinary system and lists its main organs as the kidneys, ureters, bladder, and urethra. It then provides details on the location, size and weight of the kidneys. It describes the structures and functions of nephrons, and explains how nephrons filter blood and form urine through processes like filtration, reabsorption and secretion. Finally, it briefly discusses the roles of other urinary organs like the ureters, bladder and urethra, as well as the micturition process.

1. FACULTY : MAAM IMTAIZ ABRO
GROUP LEADER : BILQUEES KATTO
GROUP MEMBERS : POOJA KUMARI,
IQRA FAIZ AND RAVEENA

2.  Define urinary system.
 List the organs of urinary system.
 Discuss the location size and weight of the kidney.
 Types of nephron.
 Discuss kidney in terms of external anatomy, gross
structure & microscopic structure.
 Describe the role of each component of nephron in
terms of filtration, selective reabsorption &
secretion involved in the formation of urine.
 Briefly discuss the role of kidney in maintaining
water & electrolytes balance.
 Discuss the structure & function of ureters, urinary
bladder & urethra.
 Briefly explain the process of micturition.

3.  The urinary system also known as renal system
or urinary tract, consist on the kidneys, ureters,
bladder & the urethra the purpose of urinary
system is to eliminate waste from the body
regulate blood volume & blood pressure control
levels of electrolytes & metabolites.
List the organs of urinary system
 Kidney
 Renal pelvis
 Ureters
 Bladder
 urethra

4.  The positioning of the kidney is just below the
rib cage, with one on each side of the spine. The
right kidney is generally slightly lower than the
left kidney to make space for the liver.
 Each kidney is approximately 3 cm thick, 6 cm
wide, & 12 cm long.
 In males, the average weight of the kidneys is
roughly 129 g for the right kidney &137 g for the
left
 In females, the average weight of these organs is
108g for the right kidney & 116g for the left
kidney.

6.  The structure of human kidney can be seen as
two reddish bean shaped organs that as located
below the rib cage on each side of the spine.
 Kidney are the main organs in the human
excretory system, which takes part in the
filtration of the blood before the urine is formed.
 Each kidney is enclosed by a thin, membranous
covering called peritonium.
 Adrenal gland is present in each kidney.
 It has a convex and concave border.
 Towards the inner concave side, a notch called
the hilum is present through which the renal
artery enters the kidney & the renal vein &
ureters leave.

7.  A longitudinal section of kidney shows that it
consists of two distinct regions; an outer darker
region the cortex & an inner lighter region, the
medulla.
 The medulla consist of many cone shaped
structures called pyramids.
 Urine is dropped continuously from the tips of
the pyramids into funnel shaped spaces called
pelvis of the ureter.
 The renal pelvis has projections called calyces.

9.  A nephron is the basic structural & functional
unit of the kidney. They are the microscopic
structure composed of a renal corpuscle & a
renal tubule. The word nephron is derived from
the Greek word nephros, meaning kidney.
 There are about millions of nephrons in each
human kidney.
 Each nephron begins with a spherical structures
called malpighian body it lies in the cortex of
kidney. Malpighian body is composed of cup-like
Bowman’s capsule. Inside this cup lies a dense
network of capillaries known as Glomerulus.
 The bowman’s capsule gives out a coiled tubules
known as proximal convoluted tubule (PCT).

10.  It lies in the cortex region. A network of capillaries is
also attaches with proximal convoluted tubules. The
PCT narrows & descends down into the medulla
makes a U-turn & comes back in the cortex. This
narrow U-shape part of tubule is known as Loop of
Henle. The ascending limb of the loop of Henle
becomes larger in diameter in the cortex & forms a
coil called Distal Convoluted Tubule (DCT).The DCT
finally opens into a common Collecting Duct.
 Blood supply to the Glomerulus of a nephron begins
as an Afferent Arteriole. Which arises from renal
arteriole. From the Glomerulus, blood is carried by
the Efferent Arteriole into two capillary networks.
One of the network called peritubuler capillaries is
associated with PCT & DCT while the other one
called Vasa Recta runs straight parallel beside the
limbs of the loop of Henle.

12.  The mechanism of urine formation involves the
following steps:
Ultra Formation
In the first stage non-selective, ultra filtration
(filtration at molecular level) of blood occurs while
passing through the Glomerulus of the malpighian
body. Two factors are responsible for this ultra
filtration. Both the capillary walls of glomerulus &
the walls of bowman's capsule are sieve-like in
nature, which permit all the molecules except
plasma protein & blood cells to pass through them.
Blood pressure in glomerulus is high because the
diameter of efferent arteriole is much less than
that of afferent arteriole. Thus a hydrostatic
pressure is generated which forces the smaller
molecules of blood from glomerulus into the
bowman’s capsule.

13.  Active reabsorption of the glomerular filtrate occurs
in the PCT, so large amount of filtrate is reabsorbed
& returned to circulation. Here glucose , amino acid
, water , salts , are reabsorbed.
Tubular secretion
At the level of both proximal as well as DCT some
poisonous substance are well as nitrogenous
substances such as ammonia , urea , uric acid ,
creatinine are secreted from the blood directly
into the filtrate by active transport. Nitrogenous
wastes added in this way are actually those
molecules which escaped the filtration in
glomeruli. Hydrogen & ammonium ions secretions

14.  From the interstitial fluid into the DCT plays
important role in the maintence of acid-base balance
in the blood.
Counter-current exchange
There are two counter current system operating
in the medulla which bare involved in the
exchange of solutes & water.
o one of the counter current is termed as counter
current multiplier in the loop of henle. This
counter current multiplier is involved in
developing concentration of ions across the
medulla.
o The other counter current system is composed of
Vasa recta, the blood vessels that run parallel to
the loop of henle, only about 1% of the blood
that flows through the kidney passes through

15.  The Vasa recta at a very slower speed. The blood
supply to Vasa recta provides sufficient
nourishment & oxygen to the cells of medulla.
 Composition of urine
components Composition(conc/100cm3)
Water 95.00
Protein 00.00
Glucose 00.00
Urea 02.00
Creatinine 0.3-0.70
Ammonia 0.3-0.70
Uric acid 0.30
Sodium 0.30
Chloride 0.60
(Ca, Mg, K, PO, SO) 0.47
PH 5.00

17.  Kidney play a major role in controlling all types
of balance in fluid & electrolytes.
 Kidney carry out reabsorption as the second step
of urine formation. Reabsorption checks the
water & ions loss & maintain their balance in the
body.
 Antidiauretic hormone or ADH is a hormone
secreted by the posterior lobe of the pituitary
gland. ADH controls the reabsorption of water by
kidney tubules or nephrons. It plays an important
role in maintaining water balance in the body.
 If the body is well hydrated the blood is diluted.
The osmoreceptors in the hypothalamic region of
the brain transmit a signal to the pituitary &

18.  Inhibit ADH secretion. This causes the nephrons of the
kidney to reabsorb less water & this result in the
excretion of dilute urine.
 When the body is dehydrated, the blood gets
concentrated secretion of ADH is facilitated, which
signals the nephrons to reabsorb more water to
maintain water balance in the body. This leads to the
formation of concentrated urine.
Structure of ureter
The ureter is made up of 3 layers; innermost
mucosa, muscularis, & the outer adventitia. The
mucosa is lined with circular transitional
epithelium. The keratin in this layer is responsible
for the waterproof properties. It is simple tubular
organ its lumen has a characteristics star shape. In
a human adult the ureter are usually 20-30cm long
& around 3-4mm in diameter.

19.  It transporting urine from the renal pelvis into
the bladder.
Structure & function of urinary bladder
Urinary bladder is triangle shaped hollow
organ is located in the lower abdomen. It is
held in places by ligaments that are attached
to other organs & the pelvic bones.

20.  The bladder’s walls relax & expand to store
urine, & contract & flatten to empty urine
through the urethra. When empty the bladder
is about the size & shape of a pear.
Structure & function of urethra
The urethra is passage way located in your
body’s pelvic region. The walls of the tube
are thin & made up of epithelial tissue,
smooth muscle cells & connective tissue.
The urethra has two different types of
sphincters, or muscles that act as valves
that open or close. It allow urine to pass
outside the body.

21.  Micturition is the process of discharging urine
from the urinary bladder.
 On average a normal adult excrete 1 to 1.5 L of
urine per day.
 Micturition process consist of two phases:
 Storage phase: the storage phase is
characterized by the storage of urine by the
urinary bladder. The movement is controlled
by the circular sphincter muscles.
 Voiding phase: the voiding phase is said to
occur when the brains sends signals to begin
urinating until the bladder becomes empty.

23. Kidney stone
Kidney stone or calculi are mainly (about 70%)
composed of calcium oxalate or phosphate.
Oxalate is an end product of body metabolism &
is present naturally in the urine. The salt it
forms with calcium has a low solubility. An
abnormally high level of oxalate in urine
promotes stone formation & may be related to a
diet containing food or drinks with a high
content of oxalic acid, for instances tomato,
spainch, leafyvegtables etc.
about 20% of calculi are termed as infective
stones. Such calculi consist of combination of
calcium, magnesium & ammonium phosphate.
Some stones (about 5%) are formed by uric acid.

24.  Lithotripsy is a recent method for removing kidney
for removing kidney & ureteral stones. In this
procedure shock waves or ultrasonic waves are
used to break up calculi for removal. Ultrasonic
lithotripsy involves the use of an ultrasonic probe
through a telescopic tube to help break up the
stones. Shock wave lithotripsy is more advance
method in which shock waves are being focused on
stones from outside the body. After being broken,
the smaller fragments are passed in urine.

26.  It is a condition in which there is a reduction in
the ability of the kidneys to filter waste products
from the blood & excrete them in urine, for
osmoregulation & to regulate the blood pressure.
As a consequence the nitrogenous waste start
accumulating in the blood which leads to the
symptoms such as nausea, vomiting, loss of
appetite, weakness, breathlessness etc. In severe
cases, it leads to coma & death. Associated
complications may include pneumonia, bleeding in
the stomach, high blood pressure etc.

27.  It is a technique used to remove waste products
from the blood & excess fluids from the body as a
treatment for renal failure. There are two methods
of a dialysis i.e. haemodialysis & peritoneal
dialysis.
Haemodialysis
Haemodialysis makes use of kidney machine or an
artificial kidney containing a fluid of carefully
adjusted composition (the dialysate). During
haemodialysis, the blood from the body is pimped
repeatedly through a tube of partially permeable
membrane bathed in dialysate. While passing through
the dialysis machine, the nitrogenous wastes &
excess salts are diffused out from the blood into the
dialysate through the dialysis membrane. There after
the blood is returned to the circulation. It goes on for
6-10 hours & three times a week under strict
regulation of diet & proper fluid intake.

29.  Peritonal dialysis requires an abdominal incision
which is done in the hospital. Through the incision
a catheter is inserted into the peritoneal cavity
dialysate from a bag attached to the catheter
passes into the cavity where it is left for several
hours. As a consequence waste from the blood
vessels lining the peritonal cavity seep through
the peritonal membrane into the cavity & mixes
with dialysate. The fluid is then allowed to drain
out through the catheter & into the empty
dialysate bag. The process takes about an hour &
is repeated during the day or overnight.

31.  From the book Sindh book board of biology.
 From byju’s
 From Google.
 From YouTube.
 https://www.hopkinsmedicine.org
 https://www.sciencedirect.com