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.
