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Kidney and its
Functional unit
M. FARAN YOUSAF
2018-DVMN-038
KBCMA College of Veterinary and Animal Sciences,
Narowal

Outline:
• Introduction.
• Shape of kidney.
• Physiology of Kidney.
• Histological features of kidney.
• Its Structure(calyx, sinus, pelvis, hilus)
• Nephron
• References.

Introduction:
• Kidneys are paired structures forming urine.
• Mostly bean shaped in all species.
• Maintain the composition of the body fluids.
• Removes the end products of the metabolism and excrete
substances from the blood.
• Reddish Brown in colour.
• Present retroperitoneally on either side of vertebral column.

Shape:
• Varies among species.
• Mostly bean shaped.
• Right kidney in Equines is VALENTINE heart shaped.
• Bovines has fissured (lobulated) outer surface and is oval shaped.

Shape:
• Kidney ,mainly, is of 3 types regarding papillae or lobes:
a) Unilobular
b) Multilobular
c) Multilobular with smooth surface

• Goat,Cat,Sheep,Dog,Horse has unilobular kidney.
• Multilobular kidney with lobulated outer surface is present in large
ruminants.
• Multi-papillar kidney with outer smooth surface is present in
humans, pigs.

Kidney of Dog
Kidney of Pig
Kidney of Ox

Physiology of Kidney:
• Formation of urine through the process of Filtration, Reabsorption
and secretion.
• Secretion of Hormones.
• Maintenance of body fluids.
• Homeostasis.
• Production of Erythropoietin.
• Maintenance of Blood Pressure.

Histology of Kidney:
• It is covered with thick C.T covering called capsule.
• It has 2 portions:
a) Cortex
b) Medulla
• Cortex has PCT and DCT while collecting ducts and Loop of Henle
are part of Medulla.
• Renal corpuscles are the part of renal cortex.
• Cortex has cortical labyrinth and medullary rays.

Surface Topography:
The kidney has:
• 2 Surfaces(Dorsal and Ventral)
• 2 Borders(Medial and Lateral)
• 2 Extremities(Cranial and Caudal)

Structural points:
• Renal hilus:Identation in Med. Border forms through which nerves,
vessels and ureter pass. At the hilus, the renal artery is dorsal, the vein
in the middle, and the ureter ventral.
• Renal Pelvis: The renal pelvis is the dilated part of the ureter in
the kidney. The renal pelvis functions as a funnel for urine flowing to the
ureter.
• Renal Calyces: The renal calyces are chambers of the kidney through
which urine passes. These are cup shaped structures surrounding the
apex of pyramids. The minor calyces surround the apex of
the renal pyramids. Minor calyces open into major calyces which opens
then into ureter.

• Renal Crest: It is present in unilobular kidney.Pelvis is elongated to
form crest.
• Renal Column: The renal column is a medullary extension of
the renal cortex in between the renal pyramids.It allows the
cortex to be better anchored. Each column consists of lines of
blood vessels and fibrous material.
• Renal Sinuses: The renal sinus is a cavity within the kidney which
is occupied by the renal pelvis, renal calyces, blood vessels,
nerves and fat.

Renal Racess:
• Only present in Equines.
• Functions in collecting urine from the sides.
• Extensions of Pelvis.

Nephron:
• Functional unit of kidney.
• Has 2 main portions:
Renal corpuscle:
i. Glomerulus
ii. Bowman’s capsule
Renal tubule:
i. Proximal convoluted tubule
ii. Loop of Henle
iii. Distal convoluted tubule

• 0.4 million nephrons in kidney of dog.
• 0.5 million nephrons in cat.
• 1 million in pig
• 2.7 million in horse
• 4 million in ox

Types of Nephrons:
• Cortical
• Juxtamedullary
May also be called :
• Short looped
• Long looped

References:
• Veterinary anatomy of domestic mammals by KONIG and LIEBICH.
• Sisson’s Anatomy.
• Google.

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