Exercise 26
Functional Anatomy of The Urinary System
Gross Anatomy of the Human Urinary System
Renal capsule
a tough fibrous layer
surrounding the
kidney and covered
in a thick layer of
adipose tissue. It
provides some
protection from
trauma and damage.
Organs of the Urinary System
• Kidneys
• Ureters
• Urinary
bladder
• Urethra
• Renal Artery
Figure 15.1a
Urinary System
Organs
Function
Kidneys
• Maintains water and electrolyte balance
of the blood
• Produces urine
Ureters
• Transports urine to urinary bladder
Urinary bladder
• Serves as a storage area for urine
Urethra
• Transports urine to the body’s exterior
• Is shorter in women than in men
Renal Artery
• Transports arterial blood to the kidney
Internal Anatomy of the Kidney
Renal cortex —outer region; contains most of
nephron structure
Renal medulla —inside the cortex; contains inner
collecting ducts
Renal pelvis – basin continuous with ureter
Renal columns —extensions of cortex-like material
inward that separate the pyramids
Calyces —cup-shaped structures, extensions of
pelvis that funnel urine
Renal or fibrous capsule -- a tough fibrous layer
surrounding the kidney
Internal Anatomy of the Kidney
Functional Microscopic Anatomy of the Kidney
m
k
l
n
o
b
a
c
Interlobular vein h
e
d
Interlobular artery g
f
i
j
n
g
h
f
e
d
c
a
k
b
Glomerulus= site of filtrate formation
Red arrows = Blood
Blue arrows = Filtrate
Glomerulus = a tiny ball-shaped structure composed of capillary blood
vessels actively involved in the filtration of the blood to form urine .
Bowman’s Capsule =Fluids from blood in the glomerulus are collected in
the Bowman's capsule (i.e., glomerular filtrate) and further processed
along the nephron to form urine.
Proximal convoluted tubule= primary site of tubular reabsorption
Glucose, Amino Acids, Na+, and Water are being reabsorbed by
the Proximal Convoluted Tubule
Collecting Ducts- collects the urine from the
nephron and send it to the ureter.
Peritubular capillaries – receives
substances from the tubular cells
Bowman’s Capsule: the inner membrane
forms part of the filtration mechanism
• There are two layers of cells that fluid (with its
contents) has to pass through during filtration.
The first layer is the
endothelium of the
glomerular capillary.
The second
layer is the
visceral layer
of the
Bowman’s
capsule,
formed by
podocytes
•
The renal corpuscle is where plasma is filtered from capillaries into the
renal tubules. At the center of renal corpuscle is the glomerulus, a
meshwork of capillaries. The glomerulus is surrounded by Bowman's
capsule
Glomerulus and Bowman’s Capsule
Visceral layer
Parietal layer
Podocytes make up the visceral layer of Bowman’s Capsule
Glomerulus is a high-pressure capillary bed
The afferent arteriole feeding the glomerulus is is larger than the efferent
arteriole which drains the arteriole
The high pressure forces out fluid and blood components smaller than
proteins from the glomerulus into the glomerular capsule
Proximal Convoluted Tubule
The cuboidal cells of the proximal
convoluted tubule have long
microvilli (brush border) on their
inside surface that dramatically
increase the surface area for
reabsorption from the filtrate.
Filtrate
What is the
purpose of this
brush border
epithelium?
Close up of brush
border (microvilli)
n
g
h
f
e
d
c
a
k
b
Nephron in Cortex
Renal Cortex = nephron
Medullary pyramid = collecting ducts
Calyces
Renal pelvis
Ureter
Glomerular capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
(Ureter)
Bladder
Urethra
Urinalysis: Characteristics of Urine
 In 24 hours, about 1.0 to 1.8 liters of urine are produced
Nitrogenous wastes normally found in urine:
Urea, uric acid, creatine
UREA
URIC ACID
CREATINE
Uric acid is derived from the breakdown of
DNA and RNA. This is taking place
continuously in the body as large numbers of
cells are produced and replaced, particularly
from the blood.
Purines are one type of nitrogenous base
found in nucleic acids. In DNA and RNA, which
are both nucleic acids, the major purines are
guanine and adenine. Purines are found in
many foods, including meat, shellfish, and
sweetbreads
Birds excrete most of their nitrogen in the form
of uric acid, an oxidized purine.
Kidney
This is a low power view of a cross section through the kidney.
Note the inner medullary tissue (green) surrounded by the outer
cortical tissue (blue)
Cortex
Identify a glomerulus,
which appears as a
ball of tightly packed
material containing
many small nuclei
Notice the vacant
appearing region
corresponding to the
glomerular capsule
that surrounds it.
The balance of the kidney tissue consists of renal tubules.
Loop of Henle
(D) Descending limbs of the loop of Henle look similar to the proximal tubule, with apical brush borders. (Blue)
(A) Ascending limbs are composed of cuboidal cells, but unlike the proximal convoluted tubule, they do not have apical
brush borders. (Green)
(C) Collecting ducts can also be seen on this slide. They can be easily distinguished by the presence of prominent lateral
borders between adjacent cells. (Orange)
Loop of Henle
•
•
•
Descending limb, with its brush border similar to that of the proximal tubule. (Blue)
Ascending limb lacks this brush border and its cells have a more squamous appearance.
(Red)
Collecting duct can be observed. (Purple)
Renal Pelvis
Urine in the
collecting ducts
eventually empties
into the renal pelvis.
Renal pelvis is the
initial dilated
portion of ureter.
Ureter
Urinary Bladder
The urinary bladder is lined by transitional
epithelium, underneath which are thick layers
of smooth muscle interwoven in various
directions.
Compare the transitional epithelium between
a relaxed bladder and a distended bladder.
Urethra