Formation of Primary Urine : Layers Explained

In the human is nephron has a glomeru­lus which func­tions as a micro­scop­ic fil­ter that con­stant­ly fil­ters blood. Blood which is to be fil­tered and touched the glomeru­lus which con­sists of fen­es­trat­ed cap­il­lar­ies as they have open­ings or pores. These fen­es­tra­tions are hun­dred times more per­me­able than the con­tin­u­ous cap­il­lar­ies cap­il­lar­ies with­out fun­ny sta­tions that are found in oth­er parts of the body. 

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For­ma­tion of pri­ma­ry urine

The phys­i­cal char­ac­ter­is­tic of the glomeru­lar cap­il­lary bol deter­mine what is fil­tered and how much is fil­tered into the bow­man’s cap­sule. Work­ing from the inside towards out­side the cap­il­lary walls are made up of the three lay­ers. The three lay­ers of the cap­il­lary was make the fil­tra­tion membrane. 

The three mem­bers are as follows:-

Endothe­li­um layer

  1. It is the most inner­most layer. 
  2. It has a rel­a­tive­ly large pores 70–100 NM in diameter. 
  3. Solutes and flu­id can pass through the endothe­li­um but not plas­ma pro­teins and blood cells. 
  4. The pro­teins asso­ci­at­ed with the ports of the endothe­li­um are neg­a­tive­ly charged so they tend to repel neg­a­tiv­i­ty charged sub­stances and allow only pos­i­tive­ly charged sub­stance to pass more readily. 

Glomeru­lar base­ment membrane 

  1. It is the mid­dle layer. 
  2. It is made up of a com­plex Nache of intra­cel­lu­lar pro­teins and is fused to the endothe­lial Layer. 
  3. It’s job is to pre­vent plas­ma pro­teins from being fil­tered out of the bloodstream. 

Epithe­li­um layer 

  1. It is the most out­er­most layer. 
  2. It con­sists of spe­cialised cells called podocytes with extend­ing fin­ger like arms to cov­er the glomeru­lar capillaries. 
  3. They wrapped around the cap­il­lar­ies but leaves gaps let’s between the par­ti­cles known as fil­tra­tion slits. 

Attend diaphragm between the plates act as a final fil­tra­tion bar­ri­er before the flu­id con­tain­ing inor­gan­ic ions and small organ­ic mol­e­cules such as glu­cose urea and amino acid fast from the blood plas­ma into the lumen or the bow­mens cap­sule. The force required for fil­tra­tion is sup­plied by blood pres­sure. The glomeru­lus con­sists of two agrios effer­ent arte­ri­oles which deliv­er blood to the glomeru­lus and dif­fer­ent attrib­ut­es which car­ry it away. Con­stric­tions of effer­ent arte­ri­oles as blood exist the glomeru­lus pro­vide resis­tance to blood flow in the cap­il­lary pre­vent­ing a pres­sure drop. The two arte­r­i­al change in size to increase or decrease the blood pres­sure in the glomeru­lus. Affer­ent arte­ri­ole are small­er in diam­e­ter than affer­ent arteriole. 

As a result the pres­sur­ized blood enters the glomeru­lus through a rel­a­tive­ly wide tube but is forced to exit through a nar­row tube. 

Togeth­er these unique fea­tures plus the fact that the heart sup­plies the kid­ney with over a litre of blood per minute around 20% of its out­put helps main­tain a high glomeru­lar cap­il­lary pres­sure so that the fil­tra­tion func­tion of the kid­ney con­tin­u­ous regard­less of fluc­tu­a­tions in blood flow. It is inter­est­ing to note that dur­ing the for­ma­tion of this fil­trate up to 25% of water and solutes are removed from the blood. The renal cor­pus­cle of the human kid­ney are capa­ble of pro­duc­ing 180 litre of urine a day but we pro­duce only about 1 to 2 litre urine per day which means that about 98% of the flu­id vol­ume of the urine is reab­sorbed And re turned to the bloodstream. 

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