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==Introduction==

|linktext =URINARY SYSTEM

|maplink = Urinary System (Content Map) - Anatomy & Physiology

|pagetype =Anatomy

==Common Anatomy==

==Common Anatomy==

 

* The kidney is the part of the urinary tract where urine is produced.  

* The kidney is the part of the urinary tract where blood is filtered and urine is produced.  

* The kidneys are paired and lie in a retroperitoneal position.   

* The kidneys are paired and lie in a retroperitoneal position.   

* They are positioned in the caudo-dorsal abdomen.

* They are positioned in the caudo-dorsal abdomen.

* They lie within a splitting of the sublumbar fascia.  This also often contains a large quantity of fat to cushion and protect the kidneys from the pressure of other organs   

* They lie within a splitting of the sublumbar fascia.  This also often contains a large quantity of fat to cushion and protect the kidneys from the pressure of other organs   

* The right kidney is most cranial in all species except the pig.

* The right kidney is most cranial in all species except the pig and grasscutter.

* In species where the right kidney is most cranial it lies in a small fossa of the caudate liver lobe.

* In species where the right kidney is most cranial it lies in a small fossa of the caudate liver lobe.

* However the left kidney is the most mobile.

* However the left kidney is the most mobile.

* During development all species begin with a multi-lobed structure but a varying degree of fusion occurs between the species giving rise to the various different characteristics seen.

* During development all species begin with a multi-lobed structure but a varying degree of fusion occurs between the species giving rise to the various different characteristics seen.

 

==The Basic Components of the Kidney==

===The Basic Components of the Kidney===

===Outer fibrous capsule===

===Outer fibrous capsule===

* External zone

* External zone

* Internal zone (juxtamedullar)

* Internal zone (juxtamedullar)

* Contains the following parts of the [[Kidney Nephron - Anatomy & Physiology | nephron]]

* Contains the following parts of the [[:Category:Nephron| nephron]]

** [[Glomerulus and Bowmans Capsule - Anatomy & Physiology | Renal corpuscles]]

** [[Nephron Microscopic Anatomy #The Renal Corpuscle| Renal corpuscle]]

** [[Proximal Tubule - Anatomy & Physiology | Proximal Convoluted Tubules]]

** [[Nephron Microscopic Anatomy #Proximal Tubule| Proximal convoluted tubule]]

** [[Distal Tubule - Anatomy & Physiology | Distal Convoluted Tubule]]

** [[Nephron Microscopic Anatomy #The Distal Tubule| Distal convoluted tubule]]

** [[Useful definitions - Renal Anatomy & Physiology | Medullary Rays]]

** [[WikiWords#Urinary Section| Medullary Rays]]

 

===Renal Medulla===

===Renal Medulla===

* Contains medullary pyramids

* Contains medullary pyramids

* The part nearest the cortex is the base of the pyramid which narrows to form the inner part - renal papilla

* The part nearest the cortex is the base of the pyramid which narrows to form the inner part - renal papilla

* The medulla can be split into two parts, the outer and the inner

* The medulla can be split into two parts, the outer and the inner

* Different parts of the [[Kidney Nephron - Anatomy & Physiology | nephron]] reside in these areas

* Different parts of the [[:Category:Nephron| nephron]] reside in these areas

* The outer medulla, which can be further divided into the outer and inner stripe, contains the following parts of the [[Kidney Nephron - Anatomy & Physiology | nephron]]:

** [[Proximal Tubule - Anatomy & Physiology | Proximal straight tubules]]

The outer medulla can be further divided into the outer and inner stripe

** [[Distal Tubule - Anatomy & Physiology | Distal straight tubule]]

 

** [[Loop Of Henle - Anatomy & Physiology | Loop of henle]]

** [[Collecting Duct - Anatomy & Physiology | Collecting ducts]]

This section located just inside the cortex contains the following parts of the [[:Category:Nephron| nephron]]:

** [[Vasa Recta - Anatomy & Physiology | Vasa recta]]

* [[Nephron Microscopic Anatomy #Proximal Tubule| Proximal straight tubules]]

* [[Nephron Microscopic Anatomy #The Distal Tubule| Distal straight tubules]]

* [[Nephron Microscopic Anatomy #The Loop of Henle| Thin descending and thick ascending limbs of the loop of henle]]

* [[Nephron Microscopic Anatomy #Collecting Duct| Outer medullary collecting ducts]]

* [[Nephron Microscopic Anatomy  #The Vasa Recta| Vasa recta]]

 

 

 

 

* The inner medulla however only contains the following parts:

* The inner medulla however only contains the following parts:

** [[Loop Of Henle - Anatomy & Physiology | Loop of henle]]

** [[Nephron Microscopic Anatomy #The Loop of Henle| Loop of henle]]

** [[Collecting Duct - Anatomy & Physiology | Collecting ducts]]

** [[Nephron Microscopic Anatomy #Collecting Duct| Collecting ducts]]

** [[Vasa Recta - Anatomy & Physiology | Vasa recta]]

** [[Nephron Microscopic Anatomy  #The Vasa Recta| Vasa recta]]

===Renal Pelvis===

===Renal Pelvis===

* The renal pelvis is located within the renal sinus

* The renal pelvis is located within the renal sinus

* All papillary ducts open here

* All papillary ducts open here

* Varies between species

* Varies between species

* Absent in cow

* Absent in cow

* Contains mucous glands in the horse

* Contains mucous glands in the horse

* The kidney is divided into [[Useful definitions - Renal Anatomy & Physiology | renal lobes]] from a structural point of view.

* The kidney is divided into [[WikiWords#Urinary Section| renal lobes]] from a structural point of view.

* These are then subdivided into [[Kidney Nephron - Anatomy & Physiology | nephrons]], [[Useful definitions - Renal Anatomy & Physiology | a medullary ray]] and [[Kidney Nephron - Anatomy & Physiology | a collecting duct]] to form a [[Useful definitions - Renal Anatomy & Physiology | renal lobule]]

* These can then be divided into a renal pyramid and the piece of cortex above it

**These structures are visible grossly and are the region of the medulla which appears triangular in cross section. They are actually cone shaped and the pointed part which faces towards the renal pelvis is termed the apex and the part against the cortex the base.

* They can also be subdivided into [[WikiWords#Urinary Section| renal lobules]] comprising of [[:Category:Nephron| nephrons]], [[WikiWords#Urinary Section| a medullary ray]] and [[Nephron Microscopic Anatomy #Collecting Duct| a collecting duct]].

* In some species the kidneys are described as '''multipyramidal''' this means they have multiple lobes and pyramids.  Others are described as '''unipyramidal''' meaning they only have one lobe and pyramid.

 

The renal blood supply is dealt with [[Kidney - Blood Supply | here.]]

===Innervation===

===Innervation===

* Sympathetic and parasympathetic fibres from solar plexus

* Sympathetic and parasympathetic fibres from solar plexus

* Travel with renal arteries

* Travel with renal arteries

* Sympathetic fibres synapse in coeliac ganglion and cranial mesenteric ganglion '''Links needed'''

* Sympathetic fibres synapse in coeliac ganglion and cranial mesenteric ganglion

 

===Lymphatic Drainage===

===Lymphatic Drainage===

Renal lymph nodes

Renal lymph nodes

==Anatomical Species Differences==

==Anatomical Species Differences==

 

The various species have major and rather striking differences in the structure of their kidneys.

The various species have major and rather striking differences in the structure of their kidneys.

These species all have similar renal anatomy. Their kidneys are relatively short and thick and they are the traditional kidney bean shape. They have a smooth outer surface and have a single renal papilla.  The renal pelvis is large and irregular with recesses which are finger like processes.

These species all have similar renal anatomy. Their kidneys are relatively short and thick and they are the traditional kidney bean shape. They have a smooth outer surface and have a single renal papilla.  The renal pelvis is large and irregular with recesses which are finger like processes.

The kidney of the feline is relatively bigger than the other species and is quite distinctive because the sub-capsular veins which run towards the hilum are visible.

The kidney of the feline is relatively bigger than the other species and is quite distinctive because the sub-capsular veins which run towards the hilum are visible. The size of the kidney can be estimated by palpation or via imaging. On a ventrodorsal radiograph, normal kidney size is usually between two to three times the length of second lumbar vertebra, 3 - 4.5 centimetres.

===Bovine===

===Bovine===

The right ureter leaves the kidney and passes along the roof of the abdomen to the pelvis in a fairly standard pattern.  The left ureter however moves across the dorsal surface of its kidney to return to the midline and follow a course as if the kidney was located on the left.  (both kidneys in the bovine are located on the right see[[Comparative Anatomy of Kidneys - Anatomy & Physiology#Ruminants| anatomical landmarks]])

 

The right ureter leaves the kidney and passes along the roof of the abdomen to the pelvis in a fairly standard pattern.  The left ureter however moves across the dorsal surface of its kidney to return to the midline and follow a course as if the kidney was located on the left.  (both kidneys in the bovine are located on the right see the anatomical landmarks section for further details)

===Porcine===

===Porcine===

The kidneys are dorsoventrally flattened.  The renal pelvis opens into quite a large space of two major calicyes from which bud about 10 minor calyces.  These attach to one renal papillae each.  The kidneys have a smooth surface.

 

The kidneys are dorsoventrally flattened.  The renal pelvis opens into quite a large space of two major calyces from which bud about 10 minor calyces.  These attach to one renal papilla each.  The kidneys have a smooth surface.

===Equine===

===Equine===

The equine kidneys not only have very different shapes compared to the rest of the domestic species but they also each have a different shape.  The right kidney is described as heart shaped whilst the left is described as being pyramidal.  Each organ weighs approximately 700g and both are dorsoventrally flattened.  The kidneys are basically unipyramidal and the only demarcation between what were the multiple pyramids of the foetus is the interlobar arteries.  This is not always the case in the foal where it is common to be able to identify lobes and the external surface is not always smooth.  The horse has a single renal papilla like the dog and its renal pelvis is large and irregular with 2 recesses (finger like processes). The cells of its pelvis secret mucin give the urine its cloudy appearance.

The equine kidneys not only have very different shapes compared to the rest of the domestic species but they also each have a different shape.  The right kidney is described as heart shaped whilst the left is described as being pyramidal.  Each organ weighs approximately 700g and both are dorsoventrally flattened.  The kidneys are basically unipyramidal and the only demarcation between what were the multiple pyramids of the foetus are the interlobar arteries.  This is not always the case in the foal where it is common to be able to identify lobes and the external surface is not always smooth.  The horse has a single renal papilla like the dog and its renal pelvis is large and irregular with 2 recesses (finger like processes). The cells of its pelvis secret mucin giving the urine its cloudy appearance.

==Anatomical Landmarks==

==Anatomical Landmarks==

Medially to the right kidney you will find the caudal vena cava and the right adrenal gland can be found dorsolateral to this structure but still medially to the kidney.  Ventrally can be found the Descending [[Duodenum - Anatomy & Physiology|duodenum]] with the right pancreatic limb more towards the ventromedial aspect.  In females the right ovary can be found caudoventrally.

Medially to the right kidney you will find the caudal vena cava and the right adrenal gland can be found dorsolateral to this structure but still medially to the kidney.  Ventrally can be found the Descending [[Duodenum - Anatomy & Physiology|duodenum]] with the right pancreatic limb more towards the ventromedial aspect.  In females the right ovary can be found caudoventrally.

The '''Cranial pole''' of the left kidney contacts the [[Stomach and Abomasum - Anatomy & Physiology | Greater curvature of stomach]] it also contacts the [[Spleen - Anatomy & Physiology|spleen]] on its dorsomedial aspect as well as potentially contacting the left limb of the pancreas.  The left adrenal gland can be found at the medial aspect of the cranial pole.  The '''Caudal pole''' of the left kidney contacts the [[Small Intestine - Anatomy & Physiology|Small intestine]] and the Descending [[Colon - Anatomy & Physiology|colon]].  At its caudoventral aspect in females is found the left Ovary.

The '''Cranial pole''' of the left kidney contacts the [[Monogastric Stomach - Anatomy & Physiology|greater curvature of stomach]] it also contacts the [[Spleen - Anatomy & Physiology|spleen]] on its dorsomedial aspect as well as potentially contacting the left limb of the pancreas.  The left adrenal gland can be found at the medial aspect of the cranial pole.  The '''Caudal pole''' of the left kidney contacts the [[Small Intestine Overview - Anatomy & Physiology|Small intestine]] and the Descending [[Colon - Anatomy & Physiology|colon]].  At its caudoventral aspect in females is found the left Ovary.

===Ruminants===

===Ruminants===

* Often divide into dorsal and ventral branches before entering kidney

* Often divide into dorsal and ventral branches before entering kidney

* Common to find double the normal number - dog

* Common to find double the normal number - dog

===Left Renal Vessels===

===Left Renal Vessels===

** Originates 2cm caudal to the right renal artery

** Originates 2cm caudal to the right renal artery

** ~3-4cm long - dog

** ~3-4cm long - dog

* Left renal vein

* Left renal vein

** Passes dorsal over the caudal vena cava

** Passes dorsal over the caudal vena cava

** ~4-5cm long - dog

** ~4-5cm long - dog

* Right Renal Vein

* Right Renal Vein

** ~4-5cm long - dog

** ~4-5cm long - dog

==Internal Vascularisation==

===Internal Vascularisation===

Once the renal artery enters the kidney is divides into the interlobar arteries.  These pass through the gaps between the renal pyramids as the reach the junctions between the cortex and medullar they branch into the arcuate arteries which move over the base of the pyramids.  From these come the interlobular arteries which supply the individual lobules of the cortex.  These arteries then branch many times to supply individual glomeruli.  The capillaries of the glomerulus then rejoin to form one vessel which then forms the [[Peritubular Capillaries - Anatomy & Physiology|peritubular capillaries]] of that nephron.  The interlobular arteries are examples of end arterioles and there are few anastomoses.  Obstruction of one of these arterioles causes ischaemic damage in the kidneys.  This is also potentially the case with the interlobar arteries.

Once the renal artery enters the kidney is divides into the interlobar arteries.  These pass through the gaps between the renal pyramids as the reach the junctions between the cortex and medullar they branch into the arcuate arteries which move over the base of the pyramids.  From these come the interlobular arteries which supply the individual lobules of the cortex.  These arteries then branch many times to supply individual glomeruli.  The capillaries of the glomerulus then rejoin to form one vessel which then forms the [[Glomerular Apparatus and Filtration - Anatomy & Physiology#Pressure in the Peritubular Capillaries|peritubular capillaries]] of that nephron.  The interlobular arteries are examples of end arterioles and there are few anastomoses.  Obstruction of one of these arterioles causes ischaemic damage in the kidneys.  This is also potentially the case with the interlobar arteries.

 

==Renal Pathology==

==Webinars==

The pathology of the kidney is beyond the scope of this section but can be found [[Urinary System - Pathology| here]]

[[Category:Kidney - Anatomy & Physiology]][[Category:Bullet Points]]