Urinary

System
HABACON, GABRIELLE ANNE
LAXAMANA, ANDREE
 Urinary System
CONSISTS OF TWO KIDNEYS, TWO URETERS, THE URINARY BLADDER AND THE URETHRA

A LARGE VOLUME OF BLOOD FLOWS THROUGH THE KIDNEYS, WHICH REMOVE

SUBSTANCES FROM THE BLOOD TO FORM URINE.
Urine contains excess water and ions, metabolic wastes (such as urea), and
toxic substances.
FUNCTIONS OF THE URINARY SYSTEM
KIDNEYS REGULATE BLOOD VOLUME AND COMPOSITION, HELP REGULATE
1 BLOOD PRESSURE, Ph, AND GLUCOSE LEVELS

2 URETERS TRANSPORT URINE FROM KIDNEYS TO URINARY BLADDER

3 URINARY BLADDER STORES URINE AND EXPELS IT TO THE URETHRA

4 URETHRA DISCHARGES URINE FROM THE BODY

Organs of the
urinary system
• LEFT KIDNEY
• RIGHT KIDNEY
• LEFT URETER
• RIGHT URETER
• URINARY BLADDER
• URETHRA
 FUNCTION OF KIDNEYS
REGULATION OF BLOOD IONIC MAINTENANCE OF BLOOD
COMPOSITION OSMOLARITY

REGULATION OF BLOOD PH PRODUCTION OF HORMONES

REGULATION OF BLOOD REGULATION OF BLOOD

VOLUME GLUCOSE LEVEL

REGULATION OF BLOOD
EXCRETION OF WASTES AND
PRESSURE
FOREIGN SUBSTANCES
 Anatomy and Histology of Kidney
• Reddish, Bean-shaped organs
• Located above the waist between the
peritoneum and the posterior wall of the
abdomen
• RETROPERITONEAL (Retro = behind)
• Located between the levels of the last
thoracis and the third lumbar vertebrae.
• Partially protected by ribs 11 and 12
• Right kidney is slightly lower than the left
kidney.
 External Anatomy of Kidney
• 10-12 cm long, 5-7 cm wide, 3 cm thick
• Mass of 135-150 grams.
• The concave medial border of each kidney 3 layers of tissue
faces the vertebral column. surround each kidney
• Renal hilum – indentation near the center of
the concave border, through which the 1. Renal Capsule (Deep)
ureter emerges. 2. Adipose capsule (Middle)
3. Renal Fascia (Superficial)
 Internal Anatomy of Kidney
A frontal section through the
kidney reveals two distinct
regions:
• A superficial, light red
region called the renal
cortex
• a deep, darker reddish-
brown inner region called
the renal medulla
Renal medulla Renal cortex
consists of: • the smooth-textured area extending
• several cone-shaped renal from the renal capsule to the bases
pyramids of the renal pyramids and into the
• The base (wider end) of each spaces between them.
• It is divided into an outer cortical
pyramid faces the renal cortex
zone and an inner juxtamedullary
• and its apex (narrower end), zone.
called a renal papilla, • Those portions of the renal cortex
points toward the renal hilum. that extend between renal pyramids
are called renal columns
 Internal Anatomy of Kidney
parenchyma
• Together, the renal cortex and papillary ducts
renal pyramids of the renal • Filtrate formed by the nephrons drains into
medulla constitute the this which extend through the renal
parenchyma papillae of the pyramids.
• The functional portion of the
kidney.
• There are about 1 million MINOR AND MAJOR CALYCES
microscopic structures called • Cuplike structures papillary ducts drain
NEPHRONS inside the onto.
parenchyma • Each kidney has 8 to 18 Minor calyces and 2
or 3 Major calyces.
 Internal Anatomy of Kidney

renal sinus
renal pelvis • The hilum expands into a cavity within
• Single large cavity where the the kidney called Renal Sinus.
major calyces drains urine • which contains part of the renal pelvis,
onto. the calyces, and branches of the renal
• (Pelv = basin) blood vessels and nerves. Adipose tissue
helps stabilize the position of these
structures in the renal sinus.
Blood and Nerve Supply of the Kidneys
• The kidneys constitute
less than 0.5% of total
body mass, they receive SEGMENTAL ARTERIES
20–25% of the resting • which supply different segments
cardiac output via the (areas) of the kidney.
right and left renal • Each segmental artery gives off
several branches that enter the
arteries parenchyma and pass through the
• In adults, RENAL BLOOD renal columns between the renal
FLOW, the blood flow lobes as the INTERLOBAR ARTERIES
through both kidneys, is
about 1200 mL per
minute.
Blood and Nerve
Supply of the
ARCUATE ARTERIES

Kidneys
• At the bases of the renal pyramids,
the interlobar arteries arch between
the renal medulla and cortex is called
as ARCUATE ARTERIES
• (Arcuate = shaped like a bow)
• Divisions of the arcuate arteries
RENAL LOBE produce a series of CORTICAL
• Consists of a renal pyramid, some RADIATE ARTERIES, these arteries
of the renal column on either side radiate outward and enter the renal
of the renal pyramid, and the cortex.
renal cortex at the base of the • Here, they give off branches called
renal pyramid AFFERENT ARTERIOLES
 Glomerulus Peritubular
Capillaries

EFFERENT ARTERIOLE
AFFERENT ARTERIOLE
• Tangled, ball-shaped capillary
network • This surround tubular parts
• The glomerularcapillaries then of the nephron in the renal
reunite to form an EFFERENT cortex.
ARTERIOLE that carries blood out • Extending from some
of the glomerulus. efferent arterioles are long,
• Glomerular capillaries are unique loop-shaped capillaries
among capillaries in the body called VASA RECTA that
because theyare positioned supply tubular portions of
between two arterioles, rather the nephron in the renal
than between an arteriole and a medulla
venule.
 Functional units of the kidneys
▪ Renal corpuscle
o Glomerulus
o Glomerular capsule (Bowman’s capsule)
▪ Renal tubule
o Proximal convoluted tubule (PCT)
o Nephron loop
• Descending limb of the nephron loop
• Ascending limb of the nephron loop
o Distal convoluted tubule (DCT)
CORTICAL NEPHRON JUXTA-MEDULLARY NEPHRON

80-85% OF NEPHRON 15-20% OF NEPHRON

RENAL CORPUSCLES - OUTER RENAL CORPUSCLES - CLOSE TO

PORTION OF RENAL CORTEX THE MEDULLA

SHORT NEPHRON LOOPS LONG NEPHRON LOOPS

o thin ascending limb
o thick ascending limb
EFFERENT ARTERIOLES BRANCH
EFFERENT ARTERIOLES BRANCH
INTO PERITUBULAR CAPILLARIES
INTO VASA RECTA AROUND LONG
AROUND PCT & DCT
NEPHRON LOOP
 GLOMERULAR
CAPSULE
 Visceral layer =
PODOCYTES
 Parietal layer
 Capsular space
RENAL
TUBULE

AND

COLLECTING
DUCTS
➢ GLOMERULAR FILTRATION
▪ In the glomerulus, blood plasma and dissolved substances
get filtered into the glomerular capsule
➢ TUBULAR REABSORPTION
▪ All along the renal tubule and collecting duct, water,
ions, and other substances get reabsorbed from the renal
tubule lumen into the peritubular capillaries and
ultimately into the blood
➢ TUBULAR SECRETIONO
▪ All along the renal tubule and collecting duct, substances
such as wastes, drugs, and excess ions get secreted from
peritubular capillaries into the renal tubule. These
substances ultimately make their way into the urine.
Glomerular Filtration
• GLOMERULAR FILTRATE – The fluid that enters the capsular space.
• FILTRATION FRACTION
– The fraction of blood plasma in the afferent arterioles of the
kidneys that becomes glomerular filtrate.
- Although a filtration fraction of 0.16–0.20 (16–20%) is typical,
the value varies considerably in both health and disease.

180 liters 150 liters

Only 1–2 liters of glomerular filtrate is excreted as urine.

Filtration membrane
3 FILTRATION
BARRIERS:
NET Filtration PRESSURE
Glomerular filtration depends on three main pressures. One pressure
PROMOTES filtration and two pressures OPPOSE filtration

1
2
3
Net filtration pressure (NFP), the total pressure that promotes filtration, is
determined as follows:
Net filtration pressure (NFP) = GBHP - CHP - BCOP
NFP = 55 mmHg - 15 mmHg - 30 mmHg
= 10 mmHg
Glomerular Filtration RATE
• The amount of filtrate formed in all renal corpuscles of both kidneys
each minute.

125 mL/min 105 mL/min

• If the GFR is too HIGH, needed substance may pass so quickly through
the renal tubules that some are not reabsorbed and are lost in the urine.
• If the GFR is too LOW, nearly all the filtrate may be reabsorbed and
certain waste products may not be adequately excreted
• GFR is directly related to the pressures that determine net filtration
pressure; any change in net filtration pressure will affect GFR.
The mechanisms that regulate glomerular filtration rate
operate in two main ways:

Three mechanisms control GFR:

•
•
•
RENAL AUTOREGULATION
The kidneys themselves help maintain a
constant renal blood flow and GFR
despite normal, everyday changes in Hormonal REGULATION
blood pressure, like those that occur
during exercise • Two hormones contribute to regulation of
GFR.
2 MECHANISMS: • Angiotensin II reduces GFR
• Myogenic Mechanism • Atrial natriuretic peptide (ANP) increases
• Tubuloglomerular Feedback. GFR.

Neural REGULATION
• Blood vessels of the kidneys are • This lowering of renal blood flow has
supplied by sympathetic ANS fibers that two consequences:
release norepinephrine.
• Norepinephrine causes (1) It reduces urine output, which helps
vasoconstriction through the activation conserve blood volume.
of alpha 1 receptors, which are
particularly plentiful in the smooth (2) It permits greater blood flow to other
muscle fibers of afferent arterioles. body tissues
Tubular Reabsorption and Tubular Secretion
• REABSORPTION is the return
of most filtered water and Tubular secretion has 2 important
many of the filtered solutes to
the bloodstream outcomes:
• Normally, about 99% of the 1. The secretion of H+ helps control
filtered water is reabsorbed. blood pH.
• TUBULAR SECRETION is the 2. The secretion of other substances
transfer of materials from the helps eliminate them from the body in
blood and tubule cells into urine.
glomerular filtrate.
 Reabsorption Routes
A substance being reabsorbed from the
fluid in the tubule lumen can take one of
two routes before entering a peritubular
capillary:

• It can move between adjacent tubule

cells
• It can move through an individual
tubule cell
 Transport mechanisms
• TIGHT JUNCTIONS form a barrier that Symporters
• prevents mixing of proteins in the Membrane proteins that move two or more
apical and basolateral membrane substances in the SAME direction across a
compartments. membrane.
• In SECONDARY ACTIVE TRANSPORT,
the energy stored in an ion’s Antiporters
electrochemical gradient drives Membrane proteins that move two or more
another substance across a substances in OPPOSITE directions across a

transport maximum (Tm)

membrane. membrane.
• Transport couples movement of an ion
down its electrochemical gradient to
the “uphill” movement of a second
substance against its electrochemical
Each type of transporter has an upper limit on
gradient. how fast it can work, just as an escalator has a
limit on how many people it can carry from one
level to another in a given period
 Obligatory water Facultative water
reabsorption reabsorption
• water is “obliged” to follow the solutes • The word facultative means “capable of
when they are reabsorbed. adapting to a need.”
• This type of water reabsorption occurs in • Facultative water reabsorption is regulated
the proximal convoluted tubule and the by antidiuretic hormone and occurs mainly
descending limb of the nephron loop because in the collecting ducts.
these segments of the nephron are always • Reabsorption of the final 10% of the water,
permeable to water a total of 10–20 liters per day
Reabsorption and Secretion in the Proximal Convoluted Tubule
The largest amount of solute and water
reabsorption from filtered fluid occurs
in the proximal convoluted tubules
 Reabsorption and
Secretion
in the Proximal
Convoluted Tubule

Most solute reabsorption in the proximal

convoluted tubule (PCT) involves Na+. Na+
transport occurs via symport and antiport
mechanisms in the proximal convoluted tubule.

NA+ SYMPORTERS
NA+(-H+) ANTIPORTERS
(A) Na+ Glucose Symporter
(B) Na+ -H+ Antiporter
 Reabsorption and Secretion in the Nephron Loop
The chemical composition of the tubular fluid now
is quite different from that of glomerular filtrate
because glucose, amino acids, and other nutrients
are no longer present.

Na+ -K+ -2CL- Symporters

 Reabsorption and
Secretion in the Early
Distal Convoluted
Tubule Sodium–potassium pumps and Cl-
leakage channels in the
Fluid enters the distal convoluted tubules basolateral membranes then
at a rate of about 25 mL/min because 80% of permit reabsorption of Na and Cl-
the filtered water has now been reabsorbed. into the peritubular capillaries.

Na+ -Cl- Symporters

 Reabsorption and
Secretion in the Late
By the time fluid reaches the end of the

Distal Convoluted
distal convoluted tubule, 90–95% of the
filtered solutes and water have returned to

Tubule and Collecting

the bloodstream.

Duct
Principal cells
• Reabsorb Na+
• Secrete K+
Intercalated cells
• Reabsorb K+ and HCO3-
• Secrete H+
 WASTE MANAGEMENT IN OTHER BODY SYSTEMS
These waste management systems include the following:

• Body buffers • Lungs

• Blood • Sweat Glands

• Liver • Gastrointestinal tract

Development of the urinary system