Introduces the urinary system's role in producing, storing and eliminating urine, then describes the kidneys, ureters and bladder. Development is traced from intermediate mesoderm through the pronephros, mesonephros and metanephros, covering nephrotomes, the pronephric and mesonephric ducts, and the ureteric bud with the metanephric blastema that forms the collecting system and functional nephrons.
Topic 24 of 44 in the MU Sofia syllabus for Anatomy (Internal Organs+Glands) (Medicine, Years 1 and 2). The free AceMed note covers it in 3 sections, about 257 words (2 min of reading), with 10 flashcards.
In this note
URINARY SYSTEM
Organs :
Development :
URINARY SYSTEM
Also known as the renal system is responsible for producing, storing and eliminating urine from the body.
Organs :
1. Kidneys
the primary organs
filters waste products and excess substances from the blood to produce urine.
2. Ureters :
Narrow tubes carry urine from the kidneys to the bladder.
3. Bladder :
Hollow, muscular organ located in the pelvis that stores urine until its ready to be expelled from the body.
Development :
From intermediate mesoderm.
Begins at the 4th week.
There are 3 stages:
1. Pronephrons
The pronephrons emerges around the 4th week of development.
It begins in the cervical region of the embryo.
Segmented divisions of intermediate mesoderm form tubules called nephrotomes.
These nephrotomes join to create the pronephric duct, which extends from the cervical region to the cloaca (distal end) of the embryo.
2. Mesonephrons: “late in 4th week”
The mesonephrons develops inferiorly to the pronephrons.
They have mesonephric tubules, which are associated with capillaries.
So they can perform filteration.
The tubules drain into the mesonephric duct (Wolffian duct).
opens into the cloaca.
3. Metanephrons
The metanephros forms the definitive kidney.
It appears around the 5th week of development and becomes functional around the 12th week.
The ureteric bud from the mesonephric duct makes contact with a caudal region of intermediate mesoderm called the metanephric blastema.
Collectively, these blastema form the metanephric system, which has two components:
Collecting system: Derived from the ureteric bud, it includes the ureter, renal pelvis, major and minor calyces, and collecting tubules.
Functional nephrons: These nephrons are responsible for urine production and filtration.
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