Flashcards in deck_1619247 Deck (61):
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