Session 2: embryology Flashcards
What is the functional unit of the kidney?
Nephron
What is the definitive kidney called in the foetus?
Metanephros
How is the metanephros formed?
Pronephros to the Mesonephros to the Metanephros
Can the metanephros conserve water?
Yes. It can produce urine and conserve water.
What is the pronephros?
- It is a duct.
- Extends from the cervical region to the cloaca
- Drives the development of the next developmental stage
What is the urogental ridge?
Region of intermediate mesoderm giving rise to both the embryonic kidney and the gonad
The mesonephric duct is capable of water conservation. True/False
False
Where do the mesonephric tubules develop?
Closer to the tail (caudal) than to the pronephros region
What is the embryonic kidney?
The mesonephric tubules and the mesonephric duct
What is the role of the mesonephric duct in regards to development?
- Important role in development of the reproductive system in the male
- Sprouts ureteric bud which induces development of the definitive kidney
What is the importance of the ureteric bud?
Induces the development of the true kidney (metanephros)
How does the true kidney develop?
- Ureteric bud communicates with the metanephric blastema
- Bud expand and branches
- Formation of the collecting system from the ureteric bud
- The excretory component is derived from the intermediate mesoderm under the influence of the ureteric bud
Where does the metanephric kidney first appear?
Pelvic region
How does the kidney ascend from the pelvis?
- Undergoes an apparent caudal to cranial shift, crossing the arterial fork formed by vessels returning blood from the foetus to placenta
- The blood supply shifts upward by formation of new vessels and the old vessels are obliterated
What happens if the old blood vessels aren’t obliterated as the kidney ascends?
They becomes accessory arteries which are end arteries.
How can renal agenesis occur?
Ureteric bud fails to interact with intermediate mesoderm.
What can go wrong with the development of the kidneys?
- Ureteric bud can fail to interact with intermediate mesoderm
- Migration can go awry
- Duplication defects
- Ectopic ureter
- Cystic disease
What are structural anomalies associated with the kidney?
- Pelvic kidney
- Horseshoes kidney
How is urogenital sinus created?
The cloaca becomes divided by urorectal septum into the urogenital sinus (and anorectalcanal)
What does the urogenital sinus differentiate into?
- Superior part connect to the umbilicus
- Majority differentiates to form the urinary bladder
- Inferior part develops into the urethra
How is the female urethra formed?
By the pelvic part of the urogenital sinus
How is the male urethra divided?
- Pre-prostatic
- Prostatic
- Membranous
- Spongy
How is the male urethra formed?
In a male, the genital tubercles elongates and genital folds fuse to form the spongy urethra.
What is hypospadias?
- Defect in fusion of urethral folds
- Urethra opens onto the ventral surface rather than at the end of the glans where it normally is
What is the overview of the development of the kidney?
- Pronephros
- Mesonephros appears and the pronephros disappears. Made of the wolfian duct or mesonephric duct.
- Urethral bud is formed from mesonephric duct. Urethral bud is only for the major calyx, minor calyx, renal pelvis and collecting duct
- Metanephros is formed from urethral bud.
- 1/3 of the bottom nephrogenic cord becomes the metanephric blastema. This circles around the urethral bud. The mesonephros which is the rest becomes the genital components
What is the bladder formed from?
The bladder is a hindgut derivative
-Derived from the caudal portion of the primitive gut tube.
Explain the process of development from the allantois?
- Allantois is involved in the development of the bladder
- It is a superoventral diverticulum of the handout and extends into the umbilical cord
- Lumen of the allantois becomes obliterated to become the urachus
- The urachus becomes median umbilical ligament in adults
What is the significance of the accessory renal arteries being terminal or end arteries?
-If the accessory arteries are occluded then the part of the kidneys that they supply will be damaged due to the lack of the blood supply.
Why would patients with ectopic urethral orifices complain of urinary incontinence?
- Urethra opens straight into the penis and leaks out
- The urine bypasses the urethral sphincter so therefore no control on urination
What does abnormally amniotic fluid show?
The kidney function in the foetus is low so less excretion of urine
What is pelvic kidney?
One of the kidney fails to ascend
How does a horseshoe kidney form?
As the kidney ascend the bases touch and fusion starts to occur
