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Flashcards in Session 2 - Embryology Deck (61)
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What tissue in the tri-laminar disc does the kidney develop from?

• Intermediate mesoderm


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

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


How is the intermediate mesoderm organised?

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


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

• The pronephros


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

• The mesonephros


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

• The metanephros


What four structure make up a nephrotome?

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


What is the pronephros?

• First kidney system in humans


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)


What is the urogenital ridge?

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


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


What makes up the embryonic kidney?

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


In what direction do the mesonephric tubules develop?

Caudal to pronephric


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

• Can produce urine, but cannot concentrate it


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

• Sprouts the ureteric bud


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

• Drives development of male reproductive system


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

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


What is the collecting system of the kidney derived from?

• The ureteric bud


What is the excretory component of the kidney derived from?

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


What is the ureteric bud the primordium of?

• The ureter
• Renal pelvis
• Calices
• Collecting tubules


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


Do the kidneys truly ascend?

• No, body undergoes cranial to caudal shift around them


What happens to blood supply of the kidney during ascendion?

• Kidneys receive blood from those arteries closest to them


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


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?



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.