Renal System: Anatomy/Embryo Review II

Question 1

What embryonic layer to the kidneys develop from?

Answer 1

Kidneys develop from the intermediate mesoderm of the urogenital ridge.

Question 2

When do the kidneys develop?

Answer 2

The human kidney develops in three successive stages during weeks four through six.

Question 3

What are the three stages of renal development?

Answer 3

• Pronephros
• Mesonephros
• Metanephros

Question 4

What happens in Pronephros?

Answer 4

The first kidney develops at the cranial end of the urogenital ridge and quickly regresses. It never
functions in humans.

Question 5

What happens in Mesonephros?

Answer 5

This is the second kidney that forms in the late fourth week. It serves a filtration function until the later part of the first trimester when the permanent kidney develops.

This kidney develops a mesonephric duct that drains into the cloaca of the hindgut.

When the mesonephros regresses, the mesonephric duct is retained in the male and contributes to the formation of the male genital tract. In the female, the duct regresses completely after short period.

Question 6

What happens in Metanephros?

Answer 6

The final kidney begins to develop while the mesonephros is still functional (around the fifth week) and becomes functional around the tenth week. This kidney develops from two mesodermal sources.

Question 7

What two mesodermal sources does the metanephros develop from?

Answer 7

The ureteric bud and the metanephric mass

Question 8

What is the ureteric bud?

Answer 8

The ureteric bud is an outgrowth from the mesonephric duct near the cloaca (caudal).

It will be the primordium of the ureter, renal pelvis, major and minor calyces, and the collecting tubules, all of which drain urine from the kidneys.

Question 9

What is the metanephric mass?

Answer 9

The metanephric mass (or blastema) is mesoderm that forms a cap over the ureteric bud. It forms the nephron (functional unit) of the kidney within the cortex and medulla.

Question 10

The final kidney is functional around week ____.

Answer 10

10. The ureteric bud grows into the blastema.

Development is dependent upon a cross induction mechanism. If either part is absent or fails to develop, the kidney will be absent on that side (renal agenesis).

Question 11

How does the kidney move once formed?

Answer 11

The final kidney is initially localized to the pelvic cavity and later shifts to a more cranial position on the posterior abdominal wall.

The ascent of the kidney is caused by diminution of the body curvature and by growth of the body in the lumbar and sacral regions.

During ascent, the kidney is vascularized by branches of the aorta at continuously higher levels and the lower vessels usually degenerate.

Question 12

What is a hypoplastic kidney?

Answer 12

Hypoplastic kidney decribes a kidney which is small, but appears architecturally normal with a normal density of nephrons.

fully functional

Question 13

What causes supernumerary kidney?

Answer 13

results from splitting of the metanephric blastema

Question 14

What is bilateral renal agencies associated with? Prognosis?

Answer 14

Bilateral renal agenesis is fatal and is associated with oligohydramnios (low volume of amniotic fluid in the cavity because the baby is swallowing too much and cant excrete it) and Potter sequence

Question 15

What is Potter Sequence?

Answer 15

• pulmonary hypoplasia due to lack of amniotic fluid pressure protection,
• limb defects (club hand) and
• facial deformities

Question 16

What causes a pelvic kidney?

Answer 16

When a kidney remains in the pelvic cavity, close to the common iliac artery, it is known as a pelvic kidney.

Question 17

What causes horseshoe kidney?

Answer 17

Sometimes the kidneys are pushed so close to one another during their passage through the arterial fork that the lower poles fuse, forming a horseshoe kidney.

The horseshoe kidney is usually at the level of the lower lumbar vertebrae, since its ascent is prevented by the origin of the inferior mesenteric artery around LV3.

Question 18

What causes double ureter?

Answer 18

occurs from early splitting of the ureteric bud. Splitting may be partial or complete and the metanephric tissue may also be divided into two parts, each with its own renal pelvis and ureter.

More frequently, the two parts have a number of lobes in common as a result of intermingling of collecting tubules

Question 19

What is ectopic ureter?

Answer 19

More rare.

When this occurs, one ureter opens into the bladder as it should, but the other is ectopic, entering the urethra, vagina or the vestibule. This results form the development of two ureteric buds. One of the buds usually has a normal position, whereas the abnormal bud moves down together with the mesonephric duct and opens abnormally in some ectopic location.