anatomy of kidney

2. The urinary system is one of the
excretory systems of the body.
It consists of the following
structures:
1- 2 Kidneys which secrete urine.
2- 2 ureters which convey the
urine from the kidneys to the
urinary bladder.
3- Urinary bladder where urine
collects and is temporarily
stored.
4- Urethra through which the
urine is discharged from the
urinary bladder to the exterior.

4. Location: The kidneys lies on the
posterior abdominal wall, one on
each side of the vertebral
column, behind the peritoneum
and below the Diaphragm and
largely under cover of the costal
margin.
Shape: Kidneys are bean-shaped
organs.
Size: about 12 cm. long, 6 cm.
wide and 3 cm. thick (4 X 2 X l
inches)
Weight: about 130 g.

5. Extension: They extend from the level of
the 12th thoracic vertebra to the 3rd
lumbar vertebra.
Axis: Each kidney lies obliquely, with its
long axis parallel with the lateral border
of psoas major muscle.
- Each kidney moves in a vertical range
of 2 cm (about 1 inches) during full
respiratory movement of the
diaphragm.
- The right kidney is usually slightly
lower (1l2 inch) than the left, probably
because of the considerable space
occupied by the liver.

6. External feature
Each kidney have:
1- Two poles (superior and inferior).
2- Two surfaces (anterior and posterior) are
usually smooth.
3- Two borders (medial and lateral).
4- A hilum

7. 1. POLES
The superior (upper) pole:
Thick and round.
Lies nearer to the median plane than
the inferior pole.
Related to the suprarenal gland.
The inferior (lower) pole:
Thin and pointed.
Lies 2.5 cm above the iliac crest.
2. SURFACES
The anterior surface: convex and faces anterolaterally.
The posterior surface: flat and faces posteromedially.
3. BORDERS
The lateral border: convex
The medial border:
Convex above and below near the poles and concave in
the middle.
presents a vertical fissure in its middle part called hilum

8. 4- The Hilum
Definition: a deep vertical slit on the medial border (central part) of the kidney give
passage to the structure inter or leave the kidney.
Site: the hilum of the right kidney lies just below, and of the left just above the
transpyloric plane and 5 cm (2 inches) from the midline.
The structure in the hilum:
a. Renal vein : anterior
b. Renal artery: intermediate.
c. Renal pelvis: is the funnel-shaped commencement of the ureter, and is normally
the most posterior of the three main structures in the hilum.
d. Subsidiary branch of renal artery.

9. RELATIONS
1. Posterior relations: similar of both kidneys and comprising mostly.
a. Diaphragm: related to posterior surface of upper pole, which separate both
kidneys from last rib & the Lt from last space & 11th rib.
b. Quadratus lumborum muscles: related to the intermediate part of posterior
surface below Diaphragmatic area.
c. Psoas major muscle: related to medial part of posterior surface below
Diaphragmatic area.
d. Transversus abdominis: related to lateral part of posterior surface below
Diaphragmatic area.

10. 2. Anterior relation of right kidney: The peritoneum lies in contact with
certain areas of the kidney.
a. RT suprarenal glands: pyramidal in shape, related to the upper pole of the right
kidney, behind the inferior vena cava and the bare area of the liver.
b. The second part of the duodenum: close to the hilum.
c. Rt lobe of the liver: related to large area back to the second part of the
duodenum.
d. Hepatic flexures of the colon: related to lateral & lower part
e. Coils of jejunum: related to the medial part of the lower pole. In addition, this
part related to the ascending branch of the right colic artery.

11. 3. Anterior relation of lift kidney : The peritoneum lies in contact with certain
areas of the kidney.
a. The suprarenal glands: crescent in shape and it is applied to upper part of the medial
border of the left kidney.
b. Spleen: applied to upper part of the lateral border of the left kidney.
c. Pancreas: middle part of ant surface.
d. Stomach: area between spleen, pancreas& suprarenal gland.
e. Descending colon: related to lateral & lower part.
f. Coils of jejunum: related to the medial part of the lower pole. In addition, this part
related to the ascending branch of the superior LT colic artery.

12. Capsules (coverings) of kidney:
From within outwards:
1. Fibrous capsule (true capsule).
A thin membrane which closely invests the kidney.
Formed by condensation of fibrous connective tissue in peripheral part of the organ.
2. Perirenal (perinephric) fat.
A layer of adipose tissue, surrounding the fibrous capsule of the kidney.
It fills the space inside the loosely fitting sheath of the renal fascia enclosing the kidney
and suprarenal gland.

13. 3. Renal fascia (false capsule).
A fibroareolar sheath, which surrounds the kidney and
perirenal fat.
It consists of the following two layers:
i. An ill-defined anterior layer (fascia of Toldt).
ii. A well-defined posterior layer (fascia of Zuckerkandl).

14. Extensions
Superiorly: enclose the suprarenal gland and become continuous
with the diaphragmatic fascia.
Inferiorly: the two layers remain separate and enclose the ureter.
The anterior layer is gradually lost in the extraperitoneal tissue of
iliac fossa while the posterior layer blends with the fascia iliaca.
Laterally: the two layers unite firmly and become continuous
with the fascia transversalis.
Medially: the anterior layer passes in front of the kidney and
renal vessels and merges with the connective tissue surrounding
the aorta and inferior vena cava (IVC). The posterior layer passes
behind the kidney and is attached to fascia covering the quadratus
lumborum and psoas major

15. 4. Pararenal (paranephric) fat.
-A layer of fat lying outside the renal fascia.
-Consist s of considerable quantity of fat
being more abundant posteriorly and
toward the lower pole of the kidney.
-Fills the paravertebral gutter and forms a
cushion for the kidney.

16. Internal Structure of the kidneys:
i. Macroscopic Structure
The kidney proper presents an outer
cortex and an inner medulla.
The cortex is located just below the
renal capsule and extends between the
renal pyramids as renal columns (columns
of Bertini).
The cortex appears pale yellow with
granular texture.
The medulla is composed of 5-11 dark
conical masses called renal pyramids
(pyramids of Malpighi).
The apices of renal pyramids form
nipple like projections—the renal
papillae which invaginate the minor
calyces.

17. Renal Sinus
It is a cavity of considerable size
present within the kidney.
It takes up a large part of the
interior of the kidney and opens at
the medial border of the kidney as
hilus.
It contains:
1- Greater part of the renal pelvis,
major and minor calyces.
2- Renal vessels, lymphatics, and
nerves.
3- Fat.

18. ii. Microscopic Structure
Histologically, each kidney consists of 1 to 3 millions of uriniferous
tubules.
Each uriniferous tubule consists of two components:
A. The nephron:
It is the structural and functional unit of kidney.
The number of nephrons in each
kidney is about 1-3 million.
Each nephron consists of:
The glomerulus is a tuft of
capillaries surrounded by Bowman's capsule.
The tubular system consists of:
a. The proximal convoluted tubule.
b. The Loop of Henle.
c. The distal convoluted tubule.
B. The Collecting tubule: Begins as a
junctional (connecting) tubule from
the distal convoluted tubule. Many
collecting tubules unite together to form collecting duct (duct of Bellini)
which opens on the apex of renal papilla.The collecting tubules radiate
from the renal pyramid into the cortical region to form radial striations
called medullary rays.

19. Blood supply:
1. Renal artery: from the abdominal
aorta at right angles at level of L 2.
2. Accessory renal artery: In 30% of
cases, arise from aorta above or below
renal artery. Usually inter the upper or
lower pole of the kidney.
3. Renal veins: Veins from the renal
segments communicate with one
another profusely (unlike the arteries)
and eventually form five or six vessels
that unite at the hilum to form the
single renal vein that drains into I V C.

20. Factors fixed Kidney in
position:
1. The renal fascia.
2. The perinephric fat.
3. Neighboring viscera.

21. Surface anatomy of the kidney
(anterior )
• The hilum of the right kidney lies
just below, and of the left just above
the transpyloric plane 5 cm (2
inches) from the midline.
• The upper pole: at point 2.5 cm (1
inche) from median plane midway
between transpyloric plane and
xiphi sternum.
• The lower pole: at point on
subcostal plane opposite to 7.5 cm
(3 inches) from median plane & 2
inches below the hilum.

22. Posterior (Morris parallelogram)
• Represented by rectangular
space between:
• 1. Upper & lower horizontal
lines: at 11th thoracic & 3rd
lumber spine respectively.
• 2. Medial & lateral vertical lines:
at 1 & 3 inches from median
plane respectively.