Lecture 40 Development and clinical embryology of the urinary system Flashcards

1
Q

The urinary system develops from

A

intermediate mesoderm and urogenital sinus

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2
Q

what is the location of the intermediate mesoderm of the urinary system?

A

between paraxial and lateral mesoderm and extends along dorsal body wall of the embryo

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3
Q

what are the two parts of the urogenital ridge ( urinary system)?

A

1- nephrogenic cord; this gives rise to the urinary system

2- gonadal ridge, gives rise to genital system

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4
Q

what are the three parts of the nephrogenic cord?

A

1- pronephros- no function, stimulates formation of mesonepheros
2- mesonephros- found in thoracic region; function briefly during early fetal period, mesonephric duct connect to cloaca and allantous and connected to yolk stalk and outside.
3- metanephros- found in lumbar region; will form permanent kidney

they give rise to each other

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5
Q

what do somites come from?

A

paraxial mesoderm

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6
Q

What are the characteristics of the pronephros?

A
  • beginning at week 4 and ends at end of week 4.
  • 7-10 cell groups in the cervical region.
  • Forms vestigial excretory units= nephromites
  • regresses before formation of mesonephros
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7
Q

what are characteristics of the mesonephros?

A
  • starts at week 4 and ends at 1st trimester
  • Excretory ( mesonephric tubules appear)
    Gradually lengthen to form an S shaped loop
    Acquires a tuft of blood to form the primitive glomerulus
    The tubules elongate laterally and join with the longitudinal collecting duct (mesonephric duct)
    mesonephric duct opens into the cloaca
  • Mesonephros degenerates by the end of 1st trimester, but their excretory tubules and duct becomes the ductus deferent, duct of epididymis and efferent ductules.
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8
Q

what do the mesonephros excretory tubules and duct become?

A

ductus deferens/vas deferens, ducts of epididymis and efferent ductules

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9
Q

What does the metanephros turn into?

A

the actual kidney

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10
Q

describe the characteristics of the metanephros

A

-appears in the 5th week
-excretory ducts develop from the metanephric mesoderm in the same manner as did the mesonephros
- ureteric bud an outgrowth from the mesonephric duct close to its attachment to the cloaca
- the bud penetrates the metanephric tissue which is molded over by a cap from the surrounding mesoderm
(metanephric blastema)

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11
Q

How does the development of the permanent kidneys work?

A

ureteric bud starts dividing and that division becomes minor calyx, major calyx and pelvis.

  • The bud dilates to form the primitive renal pelvis and splits into caudal stalk ( ureter) and cranial portion ( collecting tubules).
  • The metanephtic diverticulum ( ureteric bud) in its cranial part undergoes successive branching
  • first divides into two to form the major calyces and continues to divide to form the minor calyces and collecting tubules. ( repeat)
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12
Q

The end of each collecting tubule divides and becomes arched. the collecting tubules induce clusters of mesenchymal cells from the metanephric blastema to form small ___________.
These vesicles elongate to form S-shaped _________.
The proximal ends of the renal tubules are invaginated by ________ (tufts of capillaries.
The tubules differentiate into structures forming the ________.

A
  • metanephric vesicles
  • metanephric ( renal) tubules
  • glomeruli
  • nephron

* excretion is done by nephrons, formed by metanephric vesicles formed by metanephric blastema**

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13
Q

When is nephron formation complete?

A

at birth

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14
Q

What makes up part of the excretory part of the nephron? embryological origin?

A

Bowman’s capsule, proximal convoluted tubule, loop of henle and distal convoluted tubule, develop from mesenchyme of metanephric blastema

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15
Q

what makes up the conducting part of the kidney?

A

collecting tubules, minor calyces, major calyces, pelvis and ureter- these develop from the ureteric bud.

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16
Q

the nephron + collecting tubule=

what invaginated into the tubules?

A

urineferous tubules.

glomeruli

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17
Q

The kidneys are initially located in the _____. Growth of the ____ and _____ allows the kidneys to ascend.
Initially the hilum faces ______ and receives branches from the _______.

As the caudal parts of the embryo grow away from the kidneys they come to lie higher and higher in the abdomen.

The kidneys rotate _____ almost _____ degrees and lie lateral to the _____ during upward migration.

A

Pelvis
abdomen, and pelvis

ventrally, common iliac arteries

medially, 90 degrees, aorta ( normal)

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18
Q

At week _____ the kidneys are in contact with the ____ glands and reach their adult position.

A

9

suprarenal glands.

  • at this adult stage normally the primordial caudal branches disappear and only the final renal arteries persist.
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19
Q

If there is failure to rotate of the kidney- the hilum faces ______

A

anteriorly

fetal kidney remains in its embryonic position

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20
Q

If there is excessive rotation- the hilum faces ______ ( rotation went too far)

A

posteriorly

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21
Q

If there is lateral rotation ( reverse rotation) , the hilum faces ______

A

laterally

  • instead of medially
22
Q

Malrotation of the kidney is associated with _____ kidneys

A

ectopic

23
Q

What is an ectopic kidney?
look at pic

pics

A
  • failure of ascent of one or both kidneys
  • most located in the pelvis
  • pelvic kidneys are close to eachother and usually form a discoid kidney ( fused kidneys)
  • they also receive blood supply from vessels near them like internal or external iliac
24
Q

what is crossed renal ectopic?

pics

A
  • kidney crosses to the other side

- 90% are fused

25
Q

what characterizes hydronephrosis?

A

accessory arteries enter the lower pole and cross anterior to the ureter, they can cause an obstruction and compress the ureter. you cannot pee, the kidney doesn’t let the urine get to the bladder.
(distention of the renal pelvis and calices)

26
Q

injury or ligation of an accessory artery can lead to

A

ischemia of the inferior pole of kidney segment of the kidney supplied ( renal segmental arteries are end arteries)

27
Q

accessory renal arteries are found where and what are the chances of having them?

A

about 25% of adult kidneys have 2-4 renal arteries

  • they usually supply the end pole/caudal pole.
  • arise from the aorta above and below the main renal artery
28
Q

What is renal genesis?

A

early degneration or failure of formation of the ureteric bud

29
Q

Unilateral renal agenesis is more common in what sex? what kidney is usually affected?

A
  • boys
  • left kidney usually the one absent
  • asymptomatic if other kidney is normal ( compensatory hypertrophy)
30
Q

Bilateral renal agenesis results in what?

A
  • oligohydroamnios
  • pulmonary hypoplasia ( lungs will not develop well because lacking amniotic fluid)
  • POTTER sequence
  • Incompatible with post-natal life
  • incompatible with life
31
Q

what is a bifid ureter?

A

early incomplete division of the ureteric bud

” retrograde ureterogram”

32
Q

what is a double kidney?

A

early complete division of the ureteric bud inducing the formation of two kidneys. It has one capsule and one arterial supply around it.

33
Q

What is supernumerary kidneys?

A

extra kidneys, this is rare.
- two separate ureteric buds developed on that side resulting in 2 separate kidneys

3rd kidney has its own capsule and its own bud supply. separate capsule

34
Q

When there are separate ureters one may have what ?

A

fistulous openings into urethra, vagina, or vestibule

35
Q

what is a horseshoe kidney?

A
  • fusion of lower poles while still in pelvis

- Ascent interrupted by inferior mesenteric artery.

36
Q

Polycystic kidney: two kinds

describe them

A
  1. autosomal dominant ( more common)
    - cysts form from all segments of the nephron
    - renal failure is usually after adulthood
  2. Autosomal recessive
    - cysts progressively form from the collecting ducts
    - kidneys become large and renal failure occurs in infancy or childhood.
37
Q

Where is the suprarenal gland located?

A

supero-medial pole of each kidney surrounded by renal fascia

adrenal glands

38
Q

what are the parts of the suprarenal gland?

A

Medulla and cortex…

39
Q

The suprarenal gland is made up of medulla and cortex. what is the medulla made up of?

A

comes from neural crest cells

neural crest cells migrate towards the coeliac cavity wall and form the adrenal medulla. they are called chromatin cells due to their yellow staining with chromium salts.

40
Q

The suprarenal gland is made up of medulla and cortex. what is the cortex made up of?

A

mesenchymal cells

week 4 coelomic (mesothelium) cells proliferate initially forming small buds that separate from the epithelium.
Week 6 these now mesenchymal cells first form the fetal adrenal cortex which replaces the adult cortex.

41
Q

In week 4-7 there is introduction of the urorectal septum. the urorectal septum divides the cloaca into what?

A
  • ventral primitive urogenital sinus

- dorsal primitive rectum

42
Q

the urorectal sinus divides the cloaca into what?

A

rectum

bladder and allantois

43
Q

The urogenital sinus has three parts. what are they?

A

Vesicle part, pelvic part, phallic part

44
Q

The cloaca divides the urogenital sinus ______and the anal canal ______ by the urorectal septum .

A

anteriorly, posteriorly

45
Q

The urogenital sinus has three portions what are they?

A
  1. upper portion- (vescial part) largest part forms the bladder.
    - continuous with the allantois which becomes the ligamentous urachus which persists in the adult as the median umbilical ligament.
  2. middle portion- ( pelvic part) which will give rise to the urethra at the neck of bladder, prostatic, and membranous portions of the male urethra and entire female urethra
  3. final portion: (phallic part): forms most of the penile urethra in males
46
Q

During development the caudal portion of the mesonephric ducts are absorbed into the urinary bladder and form the _______.

A

trigone ( two ureters and one urethra)

this comes from the mesonephric duct

47
Q

During fetal life what does the urachus connect?

A

it connects the bladder to the umbilical cord. it is located anterior to the peritoneum.

48
Q

by birth, the urachus is obliterated and converts to the structure known as the _________.

A

median umbilical ligament

49
Q

In the absence of completely obliteration of the urachus, the urachus persists and can lead to what?

A

urachal cyst, sinuses, or fistula

50
Q

Describe a Urachal cyst:

see pic

A

it forms when both the umbilical and bladder ends of the urachal lumen close, while a portion remains patent and fluid filled.

51
Q

An umbilical urachal sinus represents what?

see pic

A

non-communicating dilatation of the urachus at the umbilical end.

52
Q

A urachal fistula forms when…

A

there is an open channel between the bladder and the umbilicus. usually in fetus, can close it.