SISTEM URINARIA

Sistem urin terdiri dari

1.       Ginjal

2.       Ureter

3.       Kantung kemih

4.       Uretra

Sistem Urinaria pada manusia

 

Ginjal

Ginjal adalah pasangan organ ekskresi yang terletak di dekat bagian lumbar di bagian  belakang di sisi kulumna vertebralis. Keduanya terletak di lekukan dalam otot punggung dibawah peritonium, di mana mereka menerima proteksi dari tulang rusuk bagian bawah. Masing-masing ginjal selalu “dipegang” di tempat oleh jaringan penghubung.Ginjal  merupakan  organ  berbentuk  kedelai,  berwarna  coklat  kemerahan.  Organ tersebut  dibungkus  kapsul  kuat  yang  terbentuk  dari  jaringan  penghubung  berserat, disebut  kapsul  ginjal.  Ginjal  memiliki  bagian  melekuk  ke  dalam,  disebut  hilum,  di  mana

arteri renalis masuk dan vena renalis keluar serta ureter keluar dari ginjal.

Ureter

Ureter berbentuk saluran kecil berotot yang memanjang dari ginjal ke kantung kemih,

dengan panjang kurang lebih 25 cm dan diameter 5 mm.  Dinding ureter memiliki tiga lapisan. Lapisan bagian dalam merupakan lapisan mukosa, lapisan  tengah  terdiri  dari  otot  polos,  dan  lapisan  luar  terdiri  dari  mantel  berserat  tersusun  atas  jaringan  konektif.  Kontraksi  peristaltik  menyebabkan  urin  masuk  ke kantungkemih, bahkan jika seseorang berbaring

Kantung kemih

Kantung kemih terletak di dalam rongga pelvis, di bawah peritonium parietal dan tepat di  posterior  simfisis  pubis.  Padalaki-laki,  bagian  ini  di  bagian  anterior  rektum.  Pada perempuan,  bagian  ini  di  bagian  anterior  vagina  dan  di  bagian  inferior  uterus.  Fungsi kantung  kemih  adalah  untuk  menyimpan  urin  hingga  dikeluarkan  dari  tubuh.  Kantung kemih memiliki tiga lubang, dua menuju ureter, dan satu lubangmenuju uretra. Dinding kantung kemih tersusun atas lapisan tengah yang merupakan serabut sirkular dan  dua  elapisan  otot  longitudinal  yang  dapat  melebar.  Permukaan  dalam  dilapisi  oleh epitel  transisional.  Dalam  keadaan  kosong,  permukaan  kantung  kemih  berlipat-lipat membentuk  rugae.  Setelah  urin  masuk  ke  dalam  dan  memenuhi  kantung  kemih  dan kantung ini menjadi besar, sel-sel epitel menjadi lebih pipih. Rugae mukosa hilang saat kantung  kemih  membesar  dan  lipatan-lipatan  kecil  mukosa  kantung  berfungsi  seperti katup untuk mencegah aliran balik urin. Di  sekitar  lubang  menuju  uretra  terdapat  sfingter.  Sfinkter  internal  dan  eksternal  tersusun atas otot rangka yang dapat dikontrol secara sadar.

Uretra

Uretra  merupakan  saluran  kecil  yangmemanjang  dari  kantung  kemih  ke  lubang  luar. Uretra  berbeda  panjangnya  antara  laki-laki  dan  perempuan.  Pada  perempuan,  panjang uretra  hanya  sekitar  4  cm.  Pendeknya  uretra  pada  perempuan  memudahkan  infeksi bakteri. Pada laki-laki, panjang uretra sekitar 20 cm.


TRY OUT

1.    Match the key terms to these definitions．

A.   ....................Drug used to counteract hypertension by causing the excretion of water.

B.    .....................Removal of metabolic wastes from the body.

C.    .....................Tubular structure that receives urine from the bladder and carries it to the outside of the body.

D.   .....................Hollow chamber in the kidney that lies inside the renal medulla and receives freshly prepared urine from the collecting ducts.

E.    .....................Filtered portion of blood contained within the glomerular capsule.

1.    Which of the following is a structural difference between the urinary systems of males and females?

a.    Males have a longer urethra than females.

b.    In males, the urethra passes through the prostate.

c.     ln males, the urethra serves both the urinary and reproductive systems.

d.    All of these are correct.

2. Which of these is found in the renal medulla?

a. loop of the nephron

b. collecting ducts

c. peritubular capillaries

d. All of these are correct.

3. Which of these functions of the kidneys are mismatched?

a. excretes metabolic wastes –- rids the body of urea

b. maintains the water-salt balance –- helps regulate blood pressure

c. maintains the acid-base balance – rids the body of uric acid

d. secretes hormones – secretes erythropoietin e. All of these are correct.

4. Which of the following is not correct?

a. Uric acid is produced from the breakdown of amino acids.

b. Creatinine is produced from breakdown reactions in the muscles.

c. Urea is the primary nitrogenous waste of humans.

d. Ammonia results from the deamination of amino acids.

5. Which part of a nephron is out of sequence first?

a. glomerular capsule

b. proximal convoluted tubule

c. distal convoluted tubule

d. loop of the nephron

e. collecting duct

6. Which portion of the nephron has cells with a brush border and many mitochondria?

a. glomerular capsule

b. proximal convoluted tubule

c. loop of the nephron

d. distal convoluted tubule

 e. collecting duct

7. When tracing the path of filtrate, the loop of the nephron follows which structure?

a. collecting duct

b. distal convoluted tubule

c. proximal convoluted tubule

d. glomerulus

e. renal pelvis

8. When tracing the path of blood, the blood vessel that follows the renal artery is the

a. peritubular capillary.

b. efferent arteriole.

c. afferent arteriole.

d. renal vein.

e. glomerulus.

9. The function of the descending limb of the loop of the nephron in the process of urine formation is

a. reabsorption of water.

b. production of filtrate.

c. reabsorption of solutes.

d. secretion of solutes.

10. Which of the following materials would not normally be filtered from the blood at the glomerulus?

a. water

b. urea

c. protein

d. glucose

e. sodium ions

11. Which of the following materials would not be maximally reabsorbed from the filtrate?

a. water

b. glucose

c. sodium ions

d. urea

e. amino acids

12. By what process are most molecules secreted from the blood into the tubule?

a. osmosis

b. diffusion

c. active transport

d. facilitated diffusion

13. Reabsorption of the glomerular filtrate occurs primarily at the

a. proximal convoluted tubule.

b. distal convoluted tubule.

c. loop of the nephron.

d. collecting duct.

14. A countercurrent mechanism draws water from the

a. proximal convoluted tubule.

b. descending limb of the loop of the nephron.

c. distal convoluted tubule.

d. collecting duct.

e. Both b and d are correct.

15. Sodium is actively extruded from which part of the nephron?

a. descending portion of the proximal convoluted tubule

b. ascending portion of the loop of the nephron

c. ascending portion of the distal convoluted tubule

d. descending portion of the collecting duct

16. Excretion of a hypertonic urine in humans is best associated with the

a. glomerular capsule and the tubules.

b. proximal convoluted tubule only.

c. loop of the nephron and collecting duct.

d. distal convoluted tubule and peritubular capillary.

17. Which of these hormones is most likely to directly cause a drop in blood pressure?

a. aldosterone

b. antidiuretichormone(ADH）

c. erythropoietin

d. atrial natriuretic hormone (ANH)

18. The presence of ADH (antidiuretic hormone) causes an individual to excrete

a. sugars.

b. less water.

c. more water.

d. Both a and c are correct.

19. To lower blood acidity,

a. hydrogen ions are excreted, and bicarbonate ions are reabsorbed.

b. hydrogen ions are reabsorbed, and bicarbonate ions are excreted.

c. hydrogen ions and bicarbonate ions are reabsorbed.

d. hydrogen ions and bicarbonate ions are excreted.

e. urea, uric acid, and ammonia are excreted.

20. The function of erythropoietin is

a. reabsorption of sodium ions.

b. excretion of potassium ions.

c. reabsorption of water.

d. to stimulate red blood cell production.

e. to increase blood pressure.

In questions 21-24, match the function of the urinary system to the human organ system in the key. Key:

a. muscular system

b. nervous system

c. endocrine system

d. cardiovascular system e. respiratory system

f. digestive system

g. reproductive system

21. Liver synthesizes urea.

22. Smooth muscular contraction assists voiding of urine.

23. ADH, aldosterone, and atrial natriuretic hormone regulate reabsorption of Na+ by kidneys.

24. Blood vessels deliver waste to be excreted.

25. Label this diagram of a nephron.