Minggu, 27 Desember 2009

PEMBENTUKAN URINE(SKEMATIK)


The kidneys /Ren in mammals are bean-shaped organs that lie in the abdominal cavity attached to the dorsal wall on either side of the spine An artery from the dorsal aorta called the renal artery supplies blood to them and the renal vein drains them.
Anatomy and physiology of animals Urinary system.jpg
The urinary system
To the naked eye kidneys seem simple enough organs. They are covered by a fibrous coat or capsule and if cut in half lengthways (longitudinally) two distinct regions can be seen - an inner region or medulla and the outer cortex. A cavity within the kidney called the pelvis collects the urine and carries it to the ureter, which connects with the bladder where the urine is stored temporarily. Rings of muscle (sphincters) control the release of urine from the bladder and the urine leaves the body through the urethra
Anatomy and physiology of animals Dissected kidney.jpg
The dissected kidney

Kidney Tubules Or Nephrons

It is only when you examine kidneys under the microscope that you find that their structure is not simple at all. The cortex and medulla are seen to be composed of masses of tiny tubes. These are called kidney tubules or nephrons . A human kidney consists of over a million of them.
Anatomy and physiology of animals Several kidney tubules oa nephrons.jpg
Several kidney tubules or nephrons
Anatomy and physiology of animals Kidney tubule or nephron.jpg
A kidney tubule or nephron
At one end of each nephron, in the cortex of the kidney, is a cup shaped structure called the (Bowman’s or renal) capsule. It surrounds a tuft of capillaries called the glomerulus that carries high-pressure blood. Together the glomerulus and capsule act as a blood-filtering device . The holes in the filter allow most of the contents of the blood through except the red and white cells and large protein molecules. The fluid flowing from the capsule into the rest of the kidney tubule is therefore very similar to blood plasma and contains many useful substances like water, glucose, salt and amino acids. It also contains waste products like urea.

Processes Occurring In The Nephron

After entering the glomerulus the filtered fluid flows along a coiled part of the tubule (the proximal convoluted tubule) to a looped portion (the Loop of Henle) and then to the collecting tube via a second length of coiled tube (the distal convoluted tubule) (see summary. From the collecting ducts the urine flows into the renal pelvis and enters the ureter.
Note that the glomerulus, capsule and both coiled parts of the tubule are all situated in the cortex of the kidney while the loops of Henle and collecting ducts make up the medulla (see diagram filtration).
As the fluid flows along the proximal convoluted tubule useful substances like glucose, water, salts, potassium ions, calcium ions and amino acids are reabsorbed into the blood capillaries that form a network around the tubules. Many of these substances are transported by active transport and energy is required.
Anatomy and physiology of animals Filtration in the glomerulus capsule.jpg
Filtration in the glomerulus and capsule
In a separate process, some substances, particularly potassium, ammonium and hydrogen ions, and drugs like penicillin, are actively secreted into the distal convoluted tubule.
By the time the fluid has reached the collecting ducts these processes of absorption and secretion have changed the fluid originally filtered into the Bowman’s capsule into urine. The main function of the collecting ducts is then to remove more water from the urine if necessary.
Normal urine consists of water, in which waste products such as urea and salts such as sodium chloride are dissolved. Pigments from the breakdown of red blood cells give urine its yellow colour.

The Production Of Concentrated Urine

Because of the high pressure of the blood in the glomerulus and the large size of the pores in the glomerulus/capsule-filtering device, an enormous volume of fluid passes into the kidney tubules. If this fluid were left as it is, the animal’s body would be drained dry in 30 minutes. In fact, as the fluid flows down the tubule, over 90% of the water in it is reabsorbed. The main part of this reabsorption takes place in the collecting tubes.
The amount of water removed from the collecting ducts is controlled by a hormone called antidiuretic hormone (ADH) produced by the pituitary gland, situated at the base of the brain. When the blood becomes more concentrated, as happens when an animal is deprived of water, ADH is secreted and causes more water to be absorbed from the collecting ducts so that concentrated urine is produced. When the animal has drunk plenty of water and the blood is dilute, no ADH is secreted and no or little water is absorbed from the collecting ducts, so dilute urine is produced. In this way the concentration of the blood is controlled precisely.
Anatomy and physiology of animals Summary of the processes involved in the formation of urine.jpg
Summary of the processes involved in the formation of urine
Ini dibaca untuk Selingan dikala kesulitan menterjemahkan hehehehe

Proses dalam ginjal


Serangkaian proses yang terjadi pada ginjal kurang lebih......


Di dalam ginjal terjadi rangkaian proses FRA (Filtrasi - Reabsorbsi- Augmentasi) .
1. Penyaringan (filtrasi)

  • Zat-zat yang difilltrasi ginjal dibagi dalam 3 bagian yaitu :
  1. non elektrolit
  2. elektrolit
  3. air.
  • Oleh karena itu, 99% filtrat glomerulus akan direabsorbsi secara aktif pada tubulus kontortus proksimal



  • Pembentukan kemih dimulai dengan filtrasi plasma pada glomerulus
  • Seperti kapiler tubuh lainnya, kapiler glumerulus secara relatif bersifat impermiabel terhadap protein plasma yang besar dan cukup permabel terhadap air dan larutan yang lebih kecil seperti elektrolit, asam amino, glukosa, dan sisa nitrogen.
  • Aliran darah ginjal (RBF = Renal Blood Flow) adalah sekitar 25% dari curah jantung atau sekitar 1200 ml/menit.
  • Sekitar seperlima dari plasma atau sekitar 125 ml/menit dialirkan melalui glomerulus ke kapsula bowman.
  • Ini dikenal dengan laju filtrasi glomerulus (GFR = Glomerular Filtration Rate).
  • Gerakan masuk ke kapsula bowman’s disebut filtrat.
  • Tekanan filtrasi berasal dari perbedaan tekanan yang terdapat antara kapiler glomerulus dan kapsula bowman’s,
  • Tekanan hidrostatik darah dalam kapiler glomerulus mempermudah filtrasi dan kekuatan ini dilawan oleh tekanan hidrostatik filtrat dalam kapsula bowman’s serta tekanan osmotik koloid darah.
  • Filtrasi glomerulus tidak hanya dipengaruhi oleh tekanan-tekanan koloid diatas namun juga oleh permeabilitas dinding kapiler.
  • Jadi filtrasi terjadi pada kapiler glomerulus pada kapsul Bowman.
  • Di Glomerulus terdapat sel-sel endotelium kapiler yang berpori (podosit) sehingga mempermudah proses penyaringan.
  • Beberapa faktor yang mempermudah proses penyaringan adalah tekanan hidrolik dan permeabilitias yang tinggi pada glomerulus.
  • Selain penyaringan, di glomelurus terjadi pula pengikatan kembali sel-sel darah, keping darah, dan sebagian besar protein plasma.
  • Bahan-bahan kecil terlarut dalam plasma, seperti glukosa, asam amino, natrium, kalium, klorida, bikarbonat, garam lain, dan urea melewati saringan dan menjadi bagian dari endapan.
  • Hasil penyaringan di glomerulus berupa filtrat glomerulus atau disebut pula urine primer
  • yang komposisinya serupa dengan darah tetapi tidak mengandung protein bahan makanan .
  • Pada filtrat glomerulus masih dapat ditemukan asam amino darah misal globulin , fibrinogen , glukosa, natrium, kalium, dan garam-garam lainnya yamng terlarut.
2. Penyerapan kembali (Reabsorbsi)


  • Volume urin manusia hanya 1% dari filtrat glomerulus.
  • Setelah filtrasi langkah kedua adalah reabsorpsi selektif zat-zat tersebut kembali lagi zat-zat yang sudah difiltrasi.
  • dan terjadi penambahan zat-zat sisa serta urea pada tubulus kontortus distal.
  • Substansi yang masih berguna seperti glukosa dan asam amino dikembalikan ke darah.
  • Sisa sampah kelebihan garam, dan bahan lain pada filtrat dikeluarkan dalam urin.
  • Tiap hari tabung ginjal mereabsorbsi lebih dari 178 liter air, 1200 g garam, dan 150 g glukosa.
  • Sebagian besar dari zat-zat ini direabsorbsi beberapa kali.

  • Setelah terjadi reabsorbsi maka tubulus akan menghasilkan filtrat tubulus atau sering disebut dengan urin sekunder yang komposisinya sangat berbeda dengan urin primer.
  • Pada urin sekunder, zat-zat yang masih diperlukan tidak akan ditemukan lagi.
  • Sebaliknya, konsentrasi zat-zat sisa metabolisme yang bersifat racun bertambah, misalnya ureum dari 0,03 % dalam urin primer naik pesat menjadi 2% dalam urin sekunder.
  • Meresapnya zat pada tubulus ini melalui dua cara. Gula dan asam mino meresap melalui peristiwa difusi
  • sedangkan air melalui peristiwa osmosis.
  • Reabsorbsi air terjadi pada tubulus proksimal dan tubulus distal. OK

3. Augmentasi

  • Augmentasi adalah proses penambahan zat sisa dan urea yang mulai terjadi di tubulus kontortus distal membentuk urine benar .
  • Urine ini kemudian dialirkan ke Tubulus Kolektivus .
  • Komposisi urin ini yang dikeluarkan lewat ureter adalah 96% air, 1,5% garam, 2,5% urea, dan sisa substansi lain, misalnya pigmen empedu yang berfungsi memberi warna dan bau pada urin. Klik ini
  • Urine itu kita kenal dengan sebutan Urine Benar karena memang benar benar urine atau Urine sesungguhnya.


3 komentar:

nyzza mengatakan...

makasih banyak.saya bisa ngerjakan tugas saya dengan baik.

nyzza mengatakan...

makasih,,,ini bisa saya buat bahan presentasi saya.artikel ini sangat membantu. :-)

Anonim mengatakan...

makasih buat informasinya