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
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.
