Chapter 13 - Urinary System

Question 1

When does the metanephros become
functional?

(A) At week 3 of development
(B) At week 4 of development
(C) At week 10 of development
(D) Just before birth
(E) Just after birth

Answer 1

C. At week 10 of development

The metanephros begins to form at week 5 and starts to function in the fetus at about
week 10. The pronephros is not functional in humans. The mesonephros is the interim
kidney, which functions until the metanephros is ready.

Question 2

A urachal cyst is a remnant of the

(A) urogenital sinus
(B) urogenital ridge
(C) cloaca
(D) allantois
(E) mesonephric duct

Answer 2

D. Allantois

The upper end of the urogenital sinus is in patent communication with the allantois,
which lies in the umbilical cord. The allantois normally regresses and forms a fibrous cord.
If a remnant persists, it forms a urachal cyst or sinus.

Question 3

During surgery for a benign cyst on the
kidney, the surgeon notes that the patient’s
right kidney has two ureters and two renal
pelves. This malformation is

(A) an abnormal division of the pronephros
(B) an abnormal division of the
mesonephros
(C) formation of an extra mass of intermediate
mesoderm
(D) a premature division of the metanephric
blastema
(E) a premature division of the ureteric bud

Answer 3

E. A premature division of the ureteric bud

The ureteric bud seems to be preprogrammed to undergo repeated divisions. These
divisions normally begin on contact with the metanephric blastema. If the ureteric bud
undergoes division prematurely, duplication of the ureter and renal pelvis occurs. In some
circumstances, two separate kidneys may form.

Question 4

The transitional epithelium lining the urinary
bladder is derived from

(A) ectoderm
(B) endoderm
(C) mesoderm
(D) endoderm and mesoderm
(E) neural crest cells

Answer 4

B. Endoderm

The transitional epithelium lining the urinary bladder is derived from endoderm
because the urinary bladder develops from the upper end of the urogenital sinus. The origin
of the urogenital sinus can be traced back to the gut tube, which is lined by endoderm.

Question 5

The transitional epithelium lining the
ureter is derived from

(A) ectoderm
(B) endoderm
(C) mesoderm
(D) endoderm and mesoderm
(E) neural crest cells

Answer 5

C. Mesoderm

The transitional epithelium lining the ureter is derived from mesoderm because the
ureter develops from the ureteric bud. The ureteric bud is a diverticulum from the
mesonephric duct whose origin can be traced back to the intermediate mesoderm.

Question 6

The podocytes of Bowman’s capsule are
derived from

(A) ectoderm
(B) endoderm
(C) mesoderm
(D) endoderm and mesoderm
(E) neural crest cells

Answer 6

C. Mesoderm

The podocytes of Bowman’s capsule develop from the metanephric vesicles, which are
of mesodermal origin.

Question 7

The proximal convoluted tubules of the
definitive adult kidney are derived from the

(A) ureteric bud
(B) metanephric vesicle
(C) mesonephric duct
(D) mesonephric tubules
(E) pronephric tubules

Answer 7

B. Metanephric Vesicle

The distal convoluted tubule, loop of Henle, proximal convoluted tubule, and
Bowman’s capsule are all derived from the metanephric vesicle.

Question 8

The trigone on the posterior wall of the
urinary bladder is formed by the

(A) incorporation of the lower end of the
mesonephric ducts
(B) incorporation of the lower end of the
pronephric ducts
(C) incorporation of the metanephric
blastema
(D) incorporation of the mesonephric tubules
(E) incorporation of the pronephric tubules

Answer 8

A. incorporation of the lower end of the mesonephric ducts

The lower ends of the mesonephric ducts are incorporated into the posterior wall of
the urinary bladder. The mesonephric ducts contribute to the connective tissue
component of the posterior wall at the trigone. It is generally believed that the transitional
epithelium lining the entire bladder (even the trigone) is of endodermal origin.

Question 9

A 6-year-old girl presents with a large
abdominal mass just superior to the pubic
symphysis. The mass is tender when palpated
and fixed in location. During surgery, a fluidfilled
mass is noted connected to the umbilicus
superiorly and to the urinary bladder
inferiorly. What is the diagnosis?

(A) Pelvic kidney
(B) Horseshoe kidney
(C) Polycystic disease of the kidney
(D) Urachal cyst
(E) Exstrophy of the bladder

Answer 9

D. Urachal Cyst

A urachal cyst or sinus forms from a remnant of the allantois and is found along the
midline on a path from the umbilicus to the apex of the urinary bladder. The epithelium
lining the cyst produces secretions that gradually fill the remnant with fluid. Very rarely,
the entire allantois persists, forming a fistula that is patent from the urinary bladder to the
exterior at the umbilicus.

Question 10

Immediately after birth of a boy, a moist,
red protrusion of tissue is noted just superior
to his pubic symphysis. After observation,
urine drainage is noted from the upper lateral
corners of this tissue mass. What is the
diagnosis?

(A) Pelvic kidney
(B) Horseshoe kidney
(C) Polycystic disease of the kidney
(D) Urachal cyst
(E) Exstrophy of the bladder

Answer 10

E. Exstrophy of the bladder

The moist, red tissue mass that is exposed to the exterior is actually the posterior wall
of the urinary bladder. This is called exstrophy of the bladder and is caused when the
anterior abdominal wall and anterior wall of the bladder fail to form. The ureters open
onto the posterior wall; therefore, urine drainage is apparent.