deck_1619247 Flashcards by Sare Bear

What tissue in the tri-laminar disc does the kidney develop from?

• Intermediate mesoderm

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What are the two areas post-gastrulation where there is no mesoderm between ecto and endoderm?

• The buccopharyngeal membrane (oral cavity) • Cloacal membrane (anus)

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How is the intermediate mesoderm organised?

• 3 systems develop sequentially • Disappearance of one system marks the onset of development of the next

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What is the first part of the renal system to develop?

• The pronephros

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What is the second part of the renal system to develop?

• The mesonephros

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What is the third part of the renal system to develop?

• The metanephros

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What four structure make up a nephrotome?

• Glomerulus • Bowman’s capsule • Proximal & distal convoluted tube • Collecting duct

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What is the pronephros?

• First kidney system in humans

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What is the function of the pronephros?

• No direct function • Provides pronephric duct which extends from the cervical region to the cloaca and drive the development of the mesonephros (becomes mesonephric duct)

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What is the urogenital ridge?

• Region of intermediate mesoderm giving rise to both the embryonic kidney and the gonad

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Is the mesonephros a functional kidney?

• Yes, but has no water conserving mechanism • Has a very important role in the development of the male reproductive tract

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What makes up the embryonic kidney?

• The mesonephros • Made up of mesonephric tubules and the mesonephric ducts

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In what direction do the mesonephric tubules develop?

Caudal to pronephric

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Why is the mesonephros only thought of as a partial kidney?

• Can produce urine, but cannot concentrate it

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How does the mesonephric duct drive the development of the definitive kidney?

• Sprouts the ureteric bud

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Aside from driving the development of the definitive kidney, give a role of the mesonephric duct

• Drives development of male reproductive system

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Where does the ureteric bud induce development of the definitive kidney?

• Within the intermediate mesoderm of the caudal region of the embryo

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What is the collecting system of the kidney derived from?

• The ureteric bud

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What is the excretory component of the kidney derived from?

• The metanephric tissue cap • Intermediate mesoderm under the influence of the ureteric bud

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What is the ureteric bud the primordium of?

• The ureter • Renal pelvis • Calices • Collecting tubules

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What is the “ascent” of the kidney?

• The metanephric kidney first appears in the pelvic region • Undergoes an apparent caudal to cranial shift, crossing the arterial fork formed by vessels returning blood from the fetus to the placenta

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Do the kidneys truly ascend?

• No, body undergoes cranial to caudal shift around them

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What happens to blood supply of the kidney during ascendion?

• Kidneys receive blood from those arteries closest to them

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Why is variation in renal blood supply so common?

• Due to the kidneys constantly changing blood supply during development • Additional renal arteries may be present, or superior or inferior pole vessels

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When would hydronephrosis occur?

• As a result of an inferior pole artery obstructing the ureter

What happens if the ureteric bud fails to interact with intermediate mesoderm?

• Renal agenesis will occur

What is one sided renal agenesis called?

Unilateral

Give five ways other ways things go awry in kidney development?

• Migration goes wrong • Wilm's tumour • Duplication defects • Ectopic ureter • Cystic disease

Outline a migration defect of the kidney

• If kidney fails to cross the arterial fork, it will end up lower than it should • If this happens to both kidneys, a horseshoe kidney may appear due to fusion

How can duplication errors occur (e.g. 2 ureters)?

• Splitting of the ureteric bud (partial or complete)

What problems occur if there is an extra ureter?

• Ectopic drainage can occur into vagina urethra • Main symptom will be incontinence

What is polycystic kidney disease?

• Recessive genetic disease which presents early and has a poor prognosis

What defect can occur in multicystic kidney disease?

• atresia of ureter

Give three facts about polycystic kidney disease?

• Recessive • Presents early • Poor prognosis

How do abnormal renal vessels appear?

• As kidneys ascend they required new arterial supply, and the previous supply disappears • If they remain, they become accessory or supernumerary arteries • If these arteries are present, renal artery will not branch and form collateral circulation

What is the cloaca?

• Part of the primitive gut tube shared by GI, urinary and reproductive tracts • Dilated, blind pouch

How is the cloaca separated from the outside?

• By the cloacal membrane

What is the urogenital sinus?

• Cloaca divided by urorectal septum • Continuous with umbilicus

What is the urogenital sinus responsible for the genesis of?

• Bladder, pelvic and phallic parts

Outline the development of the male urinary tract

• Mesonephric ducts reach urogenital sinus • Ureteric buds spout from MD • Smooth musculature begins to expand, urogenital sinus begins to appear • Ureteric bud and mesonephric ducts make independent openings in urogenital sinus • Prostate and prostatic urethera formed

Where is the bladder derived from?

• The hindgut

What is the function of the mesonephric duct in males?

• Forms part of reproductive tract

How is the cloaca divided?

• By the urorectal septum

What does division of the cloaca by the urorectal cloaca form?

• Urogenital sinus (future bladder and urethera) • Anorectal canal

What is the allantois?

• A superoventral diverticulum of the hind gut which extends to the umbilicus

What does the allantois become and how?

• Lumen of the allantois becomes obliterated to become the urachus • Urachus becomes the median umbilical ligament in adults

Outline the development of the male urinary tract

• Mesonephric ducts reach urogenital sinus • Ureteric buds spout from mesonephric duct ○ Ureteric bud will become ureter opening into bladder • Smooth musculature begins to expand, UGS begins to expand • Ureteric buds and mesonephric ducts make independent openings in UGS • Prostate and prostatic urethera formed. MD is maintained in the male, forming prostate and seminal vesicles.

What is the epithelium of the bladder derived from?

• The endoderm of the urogenital sinus • EXCEPT for trigone, which is derived from distal ends of mesonephric ducts

Give the four divisions of the male urethera

• Pre ‐ prostatic • Prostatic • Membranous • Spongy

Where are the first three parts of the male urethera formed from?

• Pelvic part of urogenital sinus

What is the spongy part of the urethera formed from?

• Phallic part of UGS

Give the three basic components of the external genitalia

• Genital tubercle • Genital folds • Genital swellings

What happens to the genital tubercle in the male?

• Elongates and genital folds to form the spongy urethera

How does formation of the female bladder differ from in the male?

• Without male hormones, the mesonephric duct regresses

What is hypospadias?

• Defect in fusion of uretheral folds • Urethra opens onto the ventral surface rather than at the end of the glans • Incidence increasing (WHY)

Give three ways in which bladder and urethera can go wrong?

• Fistulae • Exstrophy of the bladder • Ectopic urethral orifices

What is exstrophy of the bladder?

• Congenital anomaly in which part of urinary bladder is present outside of the body • Due to maldevelopment of lower abdominal wall

How may exstrophy of the bladder be due to a urachal fistula?

• A patent urachus, which normally becomes the median umbilical ligament • If it remains as a duct, it will connect the bladder to the umbilicus

Where do the metanephric kidneys initially lie?

• Close to each other in the pelvis, ventral to the septum

What does the ascent of the kidneys stem from?

• Growth of the embryo's body caudal to the kidneys

What happens to the hilum of the kidney as it develops?

• It initially faces ventrally (forward), but rotates medially almost 90 degrees.