Week 2 - Development Flashcards
From where do the kidneys receive their blood supply?
-Abdo aorta
Where is the intermediate mesoderm in the embryo?
-Between the paraxial and somatic/splanchnic mesoderm
Which part of the primitive gut tube contributes to renal deveopment?
-Primitive Hind gut tube
Which section of the trilaminar disk forms the kidneys?
-Intermediate mesoderm
Briefly, What happens to the intermediate mesoderm to form the kidneys?
- Organised sequentially into 3 systems, pronephros, mesonephros and metanephros
- When one system disappears the other emerges
Where does the pronephros first appear?
-Cervical region
Describe the pronephros stage
-Pronephros is a very simple structure which develops from intermediate mesoderm and develops a pronephrotic duct which runs from cervical to cloaca
Describe the mesonephros stage
- Mesonephros commandeers pronephrotic duct and develops caudally to run almost entirety of embryonic trunk
- Mesonephric tubules deveop caudally
- Mesonephric duct sprouts uteric buds after contact with cloaca
Is the pronephros functioning?
-No
What is the urogenital ridge?
-A prominent region of intermediate mesoderm which gives rise to both the embryonic kidney (mesonephros) and the gonad
Which system is the first embryonic kidney?
-Mesonephros (mesonephric tubules and duct makes embryonic kidney)
How does the ureteric bud drive development of the definitive kidney?
-Ureteric bud sprouts from mesonephric ducts and releases chemical mediators which are inductive to the surrounding area of undifferentiated mesoderm (known as metanephric blastema)
What is the metanephric blastema?
-Area of undifferentiated intermediate mesoderm which develops into the metanephros
Describe metanephros stage
- Ureteric bud makes contact with blastema
- Bud expands and branches into the undifferentiated tissue forming the major and minor calyx. Meanwhile definitive kidney developing due to chemical mediators being released from bud
Where is the collecting system of the definitive kidney derived from?
-Ureteric bud
Where is the excretory component of the definitive kidney derived from?
-Intermediate mesoderm (metanephric blastema)
Where does the metanephric kidney first appear?
-Pelvic region
What happens to the definitive kidney once formed in the pelvis?
-Ascends to its anatomical position by crossing the umbilical artery
What happens to the arterial supply to the kidney as it ascends?
-Polar arteries are induced and regressed from the abdo aorta multiple times
What is the result of ureteric bud failing to interact with intermediate mesoderm?
-Renal agenesis (absence of kidney)
What is wilm’s tumour?
-Congenital tumour of kindey
What are the common causes of a duplication defect?
- Splitting of the ureteric bud
- Additional ureteric buds sprout
Why can ectopic ureteral orifices result in incontinence?
-If the ureter joing the urethra after bladder sphincters or to the vagina
What is the most common cause of multicystic kidney disease?
-Atresia of ureter
What is polycystic kidney disease?
-Recessive genetic disorder resulting in multiple cysts in the kidneys
What is the cloaca?
-The point at which the GI, urinary and reproductive tracts end in early development
What shares the reproductive tract?
-The mesonephric duct
What is the primordia of primitive bladder?
-A region of the hind gut
What is the urorectal septum?
-A wedge of mesoderm which develops downwards at the cloaca and separates the three tracts, in addition to forming the urogenital sinus from the hind gut
What is the urogenital sinus continuous with?
-Urachus
What is the allantois?
- A region which filters liquid waste in exchange with mother
- Develops into urachus once metanephros and ureter is functioning
What is the urachus?
-Fibrous remnant of allantois
What does the urachus become?
-Median umbilical ligament as it regresses
Where is the median umbilical ligament?
-Between bladder and umbilicus
What is the result of a patent urachus?
-Urine leaks out of belly button (umbilicus)
What are the sections of the urogenital sinus?
- Largest upper part is future bladder
- Pelvic and phallic parts are parts of future urethra
Describe the development of the bladder, urethra and prostate in males
- Mesonephric ducts reach urogenital sinus
- ureteric buds sprout from mesonephric duct
- Smooth musculature begins to appear in wall of UGS causing expansion of UGS
- consumption of the junction of the ureteric bud and mesonephric ducts
- UBs and MDs make independant openings in UGS
- UBs engorged by primitive bladder from UGS to open into it
- mesonephric duct develops into duct system of male repro tract and prostate and prostatic urethra formed
Describe development of the bladder in females
- mesonephric ducts reach UGS
- uteric buds sprout from MD
- Smooth musculature appears in UGS and begins to expand
- Consumes ureteric buds and mesonephric duct begins to regress
- primitive bladder forms and engorges ureteric bud so they open into it. MD completely regresses
What causes mesonephric duct to regress in women?
-Absence of androgens
From where is the female urethra derived?
-Pelvic part of UGS
What are the 4 parts of male urethra?
- Preprostatic
- Prostatic
- Membranous
- Spongy (corpus spongiosum)
From where is the male urethra derived?
- Preprostatic, prostatic and membranous from pelvic part of UGS
- Spongy from phallic part of UGS
What are the basic components of the external genitalia?
- Genital tubercle
- Genital folds
- Genital swellings
What happens to the genital tubercle and folds in males regarding the urinary tract?
-GT Elongates and genital folds fuse to form spongy urethra
What happens to the genital folds in females regarding the urinary tract?
-No fusion of the genital folds and urethra opens into vestibule
Why can fistulae form during urinary tract development?
-Failure of separation of urinary tract from GI tract
What is exstrophy of the bladder?
-Bladder opens onto anterior abdominal wall
What is hypospadias?
- Defect in fusion of urethral folds due to lack of androgen secretion
- Urethra opens onto ventral surface rather than end of phallus
What is the functional unit of the kidney?
-Nephron (nephrotome)
