Urinary System

Question 1

The urogenital system develops from what type of tissue?

During lateral folding, what ridges appear?

Answer 1

• intermediate mesenchyme (dorsal body wall of embryo)
• urogenital ridge (each side of dorsal aorta)

Question 2

The nephrogenic cord will give rise to the …?

The gonadal ridge will give rise to the …?

Answer 2

nephrogenic cord = urinary system

gonadal ridge= genital system

Question 3

What are the 3 sets of kidneys?

Which sets are functional and which are permenent?

Answer 3

pronephroi (never functional; appear@ week 4)

mesonephroi (appear@ week 4; functions briefly for 4 weeks)

metanephroi (begin developing@week 5; permanent kidney @ week 10);S1-S2

Question 4

What persists after the pronephri degenerates?

What does this become?

Answer 4

pronepheric ducts persist

• becomes the **Wolffian duct **(mesonephric duct)

Question 5

The mesonephric ducts open into what structure?

The mesonephroi degenerate at the end of the first trimester, their tubules become what adult structure?

Answer 5

• the cloaca (trigone of urinary bladder)

Question 6

The primordia of permanent kidneys starts developing at what week?

They are functional by what week?

Answer 6

• week 5

- week 8 (mesonephroi)

* urine is secreted into amniotic cavity

* fatus swallows 100s mL of amniotic fluid/day

*fetal waste eliminated by maternal kidneys

Question 7

By what week are the kidneys in their final abdominal position?

• what rotational change in position takes place?

Answer 7

week 9 (become fixed to suprarenal glands)

• 90 degrees medially; hilum faces medially

(kidneys eventually become retroperitoneal)

Question 8

How does the blood supply change in the ascending kidney?

How many different positions does it have?

Answer 8

renal arteries:

1st: branches of common iliac arteries
2nd: distal end of the aorta
3rd: new branches from aorta

(3 positions in total)

Question 9

Accessory Renal Arteries

(Supernumerary renal arteries)

Answer 9

• about 25% of adult kidneys have two to four renal arteries
• usually arise from the aorta
• accessory renal artery to inferior pole of kidney may cross anterior to

ureter + obstruct it = hydronephrosis (distension of renal pelvis + calices with urine)

• if accessory artery is damaged/ligated kidney part supplied = ischemic

Question 10

Unilateral Renal Agenesis

Answer 10

• left kidney is usually absent
• usually asymptomatic (other kidney = compensatory hypertrophy)

Question 11

Bilateral Renal Agenesis

Answer 11

failure in development of the metanephric diverticula

- oligohydramnios (b/c little/no urine excreted into amniotic cavity)

• incompatible with postnatal life b/c associated pulmonary hypoplasia**
• ** new developments = potential survival with dialysis & early kidney transplant*

Characteristic facial appearance:

• eyes widely separated
• epicanthic folds (wrinkly skin)
• ears are low-set
• broad nose and flat
• limb defects (lack of space to develop)

Question 12

Ectopic Kidney

Answer 12

One or both kidneys in abnormal position

failure to alter position during embryo growth

• in pelvis (pelvic kidney) or inferior part of the abdomen (lumbar kidney)

most common = pelvic

Question 13

Horseshoe Kidney

Answer 13

poles of kidneys are fused; (usually inferior poles)

• lies in the hypogastrium, anterior to the inferior lumbar vertebrae
• usually asymptomatic
• normal ascent is prevented b/c they are caught by the root of inferior mesenteric artery

Question 14

Ureteropelvic Junction Obstruction (UPJ)

Answer 14

obstruction to urine flow from the renal pelvis to the proximal ureter

_**most common congenital obstruction of the urinary tract**_

• severe uteropelvic atresia => multicystic dysplastic kidney with severely dilated calyces
• kidney consists of grapelike, smooth-walled cysts of variable size; b/t cysts are dysplastic glomeruli + atrophic tubules

Question 15

Childhood polycystic kidney disease (PCKD)

Answer 15

• kidneys are huge + spongy and contain cysts caused by dilatation of collecting ducts + tubules that compromise kidney function
• autosomal recessive disease (short arm of chromosome 6 (p6))
• associated clinically w cysts of the liver, pancreas, + lungs
• treatment: dialysis + kidney transplant

Question 16

Wilms’ Tumor (WT)

Answer 16

_**most common renal malignancy of childhood**_

• large, solitary, well-circumscribed mass; (on cut) soft, homogeneous, + tan-gray
• recapitulates different stages of embryologic formation of kidney:

= 3 histologic areas: stromal, blastemal (tightly packed embryonic cells), tubular

Question 17

Duplications of the Urinary Tract

Answer 17

Cause: division of the metanephric diverticulum

• degree of duplication depends on how extent the division was
• Complete division = double kidney with bifid ureter or separate ureters

* supranumeracy kidneys*

Question 18

Ectopic Ureter

Answer 18

males: open into neck of bladder or into prostatic part of urethra

• above external urethral sphincter = incontinence NOT common

females: open into bladder neck, urethra, vagina or vestibule of the vagina

• below external urethral sphincter = incontinence IS common

Question 19

Ureterocele

(Simple vs. Ectopic)

Answer 19

simple ureterocele:

- distal end of ureter has cystlike protrusion into the submucosal layer of the urinary bladder

ectopic ureterocele:

• cystlike protrusion into the submucosal layer of the urinary bladder associated with ectopic ureter + duplication
• -* ureterocele is at the end of ureter from upper renal segment & is located inferior to other ureter opening

Question 20

What divides the cloaca into the urogenital sinus and rectal sinus?

How is the urogenital sinus further divided?

Answer 20

urorectal septum

urogenital sinus:

• cranial vesicle = bladder
• middle pelvic part = prostatic urethra (M)/ entire urethra (F)
• caudal phallic part = primordium of penis or clitoris

Question 21

What are the tissue origins of the bladders layers?

What are the tissue origins of the Male & Female urethras?

Answer 21

BLADDER:

(M/F) epithelium = endoderm (vesicle part of urogenital sinus)

(M/F) other layers of its walls = splanchnic mesenchyme

URETHRA:

(most of M/ all of F) epithelium = endoderm (vesicle part of urogenital sinus)

(M/F) connective tissue + smooth m. = splanchnic mesenchyme

Question 22

How does the allentois contribute to the development of the bladder?

Answer 22

• originally allentois is continuous with bladder
• allentois constricts = urachus
• urachas extendes from umbilicus –> apex of bladder
• in adult, urachus = median umbilical ligament
• (failure of urachus to constrict = urachal cyst or fistula)*

Question 23

Urachal cysts

Answer 23

• originate from remnants of the epithelial lining of the urachus
• NO connection b/t bladder & umbilicus

Question 24

Urachal Sinus

Answer 24

persistent inferior end of the urachus that dilates and opens into the bladder

Question 25

Urachal fistula

Answer 25

entire urachus remains patent , **allowing urine to escape** from its umbilical orifice

Question 26

Congenital Megacystis

Answer 26

- large urinary bladder, may result from **congenital disorder of the metanephric diverticulum**; may associate w *dilation of the renal pelvis* **= absolute renal failure** + **pulmonary hypoplasia; **_lethal_ unless intrauterine treatment is performed

Question 27

Exstrophy of Bladder

Answer 27

**- exposure + protrusion of mucosal posterior wall of bladder** **-** due to abdominal wall + anterior bladder wall failure - trigone of bladder + ureteric orifices are exposed - some cases = penis is divided in two parts

Question 28

Development of the Female Urethra:

Answer 28

- lower portion of the urogenital sinus (endoderm) - develops *endodermal outgrowths* into *surrounding mesoderm* = **urethral glands** + **paraurethral glands of Skene** (homologous to prostate gland) - _vestibule of vagina_ develops *endodermal outgrowths* = l**esser and greater vestibular glands of Bartholin**

Question 29

Development of the Male Urethra:

Answer 29

- **prostatic urethra**, **membranous urethra**, **bulbous urethra** + **proximal part of penile urethra** = from lower portion of urogenital sinus (endoderm) - **distal part of urethra** (in glans of penis) = solid cord of **ectodermal cells** growing inward from tip of glans; joins rest of spongy urethra

Question 30

Development of the Suprarenal Glands:

Answer 30

**cortex =** mesenchyme; **medulla** = neural crest cells *- neural crest cells differentiate into chromaffin cells (stain yellow-brown)* **- Week 6:** cortex begins as aggregation of mesenchymal cells on each side of the embryo b/t root of dorsal mesentery + gonad - Cortex = very large during fetal period + at birth; grows smaller after birth - Cortex produces **steroid precursors** used by placenta for **synthesis of estrogen** **- At Birth =** cortex + medulla (**zona fasciculata** + **zona glomerulosa)** **- End of year 3 = zona reticularis** is visable

Question 31

Neuroblastoma (NB)

Answer 31

- **_common_** **extracranial neoplasm** containing primitive neuroblasts (neural crest origin) - presents in children; found in **extra-adrenal (60%)** or **within the adrenal medulla (40%)** - metastasizes to *bone marrow*, *bone*, + *lymph nodes.* * -* common lab finding = increased urine vanillylmandelic acid (VMA) + metanephrine levels

Question 32

Pheochromocytoma (PH)

Answer 32

- **_rare_ neoplasm;** contains both epinephrine + norepinephrine - present in adults 40-60 years old; generally found in region of adrenal gland; may be found in extrasuprarenal sites - associated w **persistent or paroxysmal hypertension**, **anxiety**, **tremor**, **profuse sweating, pallor, chest pain,** and **abdominal pain** **-** lab findings = increased urine vanillylmandelic acid (VMA) + metanephrine levels, *inability to suppress catecholamines with clonidine*, + *hyperglycemia* - Treatment: surgery or phenoxybenzamine (an a-adrenergic antagonist)

Question 33

Congenital Adrenal Hyperplasia (CAH) | (Female pseudointersexuality)

Answer 33

- most common cause = *mutations in genes* for enzymes involved in **adrenocortical steroid biosynthesis** - **excessive androgen production** by suprarenal cortex = masculinization in females - **Female pseudointersexuality** = mild clitoral enlargement, complete labioscrotal fusion w a phalloid organ, or macrogenitosomia (in the male fetus) - cannot synthesized aldosterone = **hyponatremia ("salt-wasting")**, **dehydration** + **hyperkalemia** (hgh K+ levels) - Treatment = infusion of intravenous saline + long-term steroid hormone replacement (cortisol + mineral-corticoids)