27. Development of urinary tract Flashcards
what is the functional unit of the kidney?
nephron
What are the 3 kidney systems in the embryo?
pronephros, mesonephros, metanephros
Does the pronephros function in humans?
No.
How do the 3 kidney systems develop in relation to eachother?
- 3 systems develop sequentially
* Disappearance of one system marks the onset of development of the next developmental stage
Where does the pronephros appear?
in the cervical region
Why is the pronephric duct important?
It extends from the cervical regions to the cloaca and drives the development of the next developmental stage
How does the pronephric duct drive further development?
Induces nearby intermediate mesoderm in the thoracolumbar region to form mesonephric tubules.
What is the mesonephric duct a continuation of?
Pronephric duct.
what is the urogenital ridge?
Region of intermediate mesoderm giving rise to both the embryonic kidney and the gonad
Where do mesonephric tubules develop?
caudal to the pronephric region
What contributes to the embryonic kidney?`
Mesonephric duct and mesonephric tubules
What is a functional limit of the mesonephros that doesn’t allow it to be useful after birth?
Has no water conserving capabilities.
How does mesonephros initiate development of definitive kidney?
Mesonephric duct sprouts ureteric bud.
What is the function of the ureteric bud?
Induces development of the true kidney (metanephros) from the undifferentiated intermediate mesoderm found caudal to the mesonephros
What is the tissue that the true kidney develops from called?
Metanephros blastema
What is the other function of mesonephric duct?
role in the development of the reproductive system in the male
What is the collecting system of kidney developed from?
Ureteric bud.
What does the collecting system of kidney consist of?
minor calcyx, major calyx, renal pelvis, ureter
What does the excretory component of kidney consist of ?
cortex, renal pyramid
What is the excretory system developed from?
Metanephric blastema (under influence of ureteric bud)
What is the metanephric blastema?
Undifferentiated intermediate mesoderm
Describe Development of the renal functional unit
- ureteric bud contacts metanephric blastema
- bud expands & branches forming the collecting system
- metanephric blastema becomes the excretory component
Where do the kidneys develop and where doe they move to?
- The metanephric kidney first appears in the pelvic region
* Undergoes an apparent caudal to cranial shift
What do the kidneys cross during their ascent?
Arterial fork formed by vessels returning blood from the fetus to the placenta
How do the renal vessels follow the kidney during its ascent?
New vessels form from the aorta as the kidneys move up. Old ones are obliterated.
What are renal accessory vessels and what percent of the population are they present in?
Renal vessels that do not get obliterated during ascent of the kindeys. 25%
What is renal agenesis?
absence of one or both kidneys
How does renal agenesis occur?
Failure of ureteric bud to interact with intermediate mesoderm
What could go wrong with development of ureters or kidneys?
- renal agenesis
- Migration goes awry
- Duplication defects
- Ectopic ureter
- Cystic disease
what are the structural abnomalies related to mifgration problems of the kidney?
pelvic kidney
horseshoe kidney
What is a horseshoe kidney?
inferior poles of both kidneys fuse; during the ascent from the pelvis in development, the horseshoe kidney gets trapped under the inferior mesenteric artery
Describe how Duplication defects & ectopic ureteral orifices occur?
Splitting of the ureteric bud
• Partial or complete
• Symptomatic consequence is ectopic ureteral opening
What is the common caudal opening that , the reproductive tract, urinary tract and GI tract share?
cloaca
What closes the cloaca to the outside?
- Closed to the outside by the cloacal membrane
* no mesoderm
What structure connects the urogenital sinus with the umbilicus?
Urachus
What is the function of the urachus?
Canal that drains the urinary bladder of the fetus that joins and runs within the umbilical cord
What does the urachus become when it closes?
Median umbilical ligament
What creates the urogenital sinus?
Urorecal septum which separates the cloaca into the urogenital sinus and the anal canal
What does the urogenital sinus differentiate to form
Majority forms the bladder. Inferior part develops into the urethra
How is the trigone of the bladder formed?
As the bladder develops from the urogenital sinus, it absorbs the caudal parts of the mesonephric ducts, becoming the trigone of the bladder. The ureters, which have formed as outgrowths of the mesonephric ducts, enter the bladder at the base of the trigone
What does the female urethra develop from?
Pelvic part of urogential sinus
What does the male urethra develop from?
Pelvic part of urigenital sinus forms the pre-prostatic, prostatic and membranous urethra. Spongy urethra develops from fusion of genital folds.
Describe what happens to urogenital sinus in females?
- mesonephric ducts (MD) reach urogenital sinus (UGS)
- ureteric bud (UB) sprouts from MD, MD begin to regress;
- MD regression continues, ureteric bud opens into UGS
Describe what happens to urogenital sinus in males?
- mesonephric ducts (MD) reach urogenital sinus(UGS)
- ureteric bud (UB) sprouts from MD
- smooth musculature begins to appear; UBs & MDs make independent openings in UGS
- prostate & prostatic urethra formed
What is hypospadia?
- Defect in fusion of urethral folds
* Urethra opens onto the ventral surface rather than at the end of the glans
What are the 4 parts that the male urethra is divided into?
Pre-prostatic
• Prostatic
• Membranous
• Spongy