L01 - Development of the Urinary System

Question 1

Common origin of urinary system and genital system

Answer 1

Both develops from the intermediate mesoderm (urigenital ridge)

Question 2

Somite level of intermediate mesoderm

Answer 2

7th to 28th somite level

Question 3

Location of intermediate mesoderm

Answer 3

Extends along the dorsal body wall of the embryo; between ectoderm and endoderm; connected to paraxial mesoderm (presomitic) medially and lateral mesoderm laterally

Question 4

Dissociation of somites and intermediate mesoderm

Answer 4

During folding of the embryo in the horizontal plane, intermediate mesoderm is carried ventrally and loses its connection with somites (paraxial mesoderm)

Question 5

Formation of urogenital ridge from intermediate mesoderm

Answer 5

The longitudinal elevation of mesoderm (dorsal side) forms a bulge into the coelom on each side of the dorsal aorta - the bulge is called urogenital ridge

Question 6

Answer 6

Question 7

Function of Urogenial Ridge

Answer 7

Form the urinary and genital structures

Question 8

Major embryonic origin of urinary system

Answer 8

Nephrogenic cord/ridge/mass

Question 9

Nephrongenic cord definition

Answer 9

Part of the urogenital ridge (and intermediate mesoderm) which will form much of the urinary system; goes through 3 spatial temporal phases of development - pronephros, mesonephros and metanephros

Question 10

Transverse section of embryo (end of 3rd week); 2, 7, 8, 9, 10

Answer 10

1.Paraxial mesoderm

2.Intermediate mesoderm

3. Lateral mesoderm
4. Notochord
5. Amnion
6. Intraembryonic coelom

7.Endoderm

8.Ectoderm

9.Somatopleural (mesoderm and ectoderm)

10. Splanchnopleural (mesoderm and endoderm)

11. Neural groove
12. Neural ridge

Question 11

Three sets of kidney system formed embryonically in temporal and spatial (cranial to caudal) sequence

Answer 11

Pronephros, Mesonephros, Metanephros

Question 12

Labelling

Answer 12

Question 13

Nephrotomes (definition)

Answer 13

Broken up segments of nephrogenic tissue (from urogenital ridge of intermediate mesoderm) from 7th - 14th somite levels; forms the pronephros

Question 14

Pronephros (Nature, Location, Time, Opening, Fate)

Answer 14

Nature: The pronephros is represented by 7-10 solid or tubular arranged cell clusters, in the cervical region (head kidney); simplest, most primitive and earliest kidney system

Location: Cervical region, 7th to 14th somite level

Time: Appear at the beginning of 4th week; regenerate by the end of 4th week

Opening: Pronephric ducts run caudally and open into the cloaca

Fate: Rudimentary pronephros soon degenrate by the end of 4th week; most pronephric ducts persist and are utilized by mesonephros

Question 15

Mesonephros (Nautre, Location, Time, Function, Composition and connection)

Answer 15

Nature: Large, elongated, intermediate excretory organs

Location: At the cervical-lumbar region, at 14th to 26th somite level; caudal to rudimentary pronephros

Time: Appear during regression of pronephros (late in 4th week); mesonephros degenerates towards the end of first trimester - tubules and ducts disappear in females (become remnant structures) by 16th week

Function: Well developed and will function as interim kidneys for about 4 weeks

Composition and connection: consists of glomeruli and mesonephric tubules - mesonephric tubules open into mesonephric ducts (aka Wolffian ducts), which opens into the cloaca

Question 16

General Fate of mesonephros

Answer 16

Degenerates towards the end of first trimester

In male a few caudal tubules and mesonephric ducts persist and participate in genital system formation, but disappear in females

[see other flashcards for detailed fate of mesonephric tubules and ducts]

Question 17

Fate of mesonephric tubules (male vs female)

Answer 17

Male: mesonephric tubules become the efferent ductules of the testes

Female: mesonephric tubules become the epoophoron and paroophoron

Question 18

Fate of mesonephric ducts (male vs female)

Answer 18

Male: paradidymis, appendix of epididymis, duct of epididymis, ductus deferens (vas deferens), ureter, pelvis, calices, collecting tubules, ejaculatory duct and seminal glands

Female: appendix vesiculosa, duct of epoophoron (homologue to epididymis in the male), duct of Gartner, ureter, pelvis, calices, and collecting tubules

Question 19

Mesonephros Labelling (9, 10, 11)

Answer 19

1. Neural tube
2. Notochord
3. Aorta dorsalis
4. Dorsal mesentery
5. Intestinal tube
6. Ectoderm
7. Somite
8. Inferior cardinal vein

9.Mesonephric duct (Wolffian duct)

10.Mesonephric tubule

11.Urogenital ridge

Question 20

Section through mesonephros (labelling)

Answer 20