Comparative Anatomy
Urogenital System
Kardong
Chapter 14
Part 14
Urogenital System

Ducts of excretory and reproductive
systems are intimately associated
with each other
Figure 14.1. Embryonic
origin of the kidneys (book
figure 14.4).
Figure 14.2. Evolutionary development of
kidneys in vertebrates.
Primitive Kidney

Archinephros- primitive excretory kidney
organ
 Holonephric concept - (3 kidneys are a
part of one organ)
 Filtration system
 Archinephric duct- drains to cloaca or
bladder
Figure 14.3. Hypothetical archinephros.
Primitive Kidney (cont.)



Pronephros
 1st tubules to appear
 Anteriorly located; head kidney
 Involutes to form lymphoidal mass
 Only functions temporarily
All tubules associated with pronephros
Pronephric (archinephric) duct drains pronephros
Figure 14.4. Three-part
kidney (book figure
14.5).
Figure 14.5. Pronephros –
anterior region of primitive
kidney.
Kidney Structure (cont.)
Figure 14.6. Fate of nephrogenic mesoderm (red).
Figure 14.7. Pronephric,
mesonephric, and metanephric
system relationships (see book
figure 14.6).
Kidney Structure (cont.)

Mesonephros (opisthonephros)- kidney
mass caudal to pronephric region
 Functional adult kidney of fish and
amphibians
 Opisthonephros - in most adult
amphibians and fishes.
 Drained by mesonephric
(archinephric) duct
Figure 14.8. Mesonephros of
urodeles (see book figure 14.8)
Figure 14.9. Mesonephric duct of
opossum embryo.
Urogenital Anatomy


Ductus efferens:
 Pronephric duct
 Mesonephric duct
 Archinephric duct (=
wolffian duct)
Anterior portion of
mesonephric tubules used in
male reproductive system
Figure 14.10. Urogenital system and adrenal
glands of male frog.
Urogenital Anatomy (cont.)
Figure 14.11. Mesonephric kidneys with mesonephric duct (black) carrying sperm
and/or urine (see book figure 14.24).
Urogenital Anatomy (cont.)

Accessory urinary ducts
 Tubules also in reproductive sys.
 Path for sperm to enter mesonephric duct (sperm duct)
Figure 14.12. Mesonephric kidneys with separate sperm duct (red) (see book figure 14.24).
Urogenital Anatomy (cont.)



Pronephros
 Lost
Mesonephros
 Mainly an embryonic kidney
 Involutes at birth
Metanephric kidney
 Takes over functions of mesonephros
 Ureter- new duct drains meta. kidney
Figure 14.13. Metanephric
kidney assuming superior
position to remainder of
urogenital system.
Urogenital Anatomy (cont.)


Mesonephric duct
 Sperm duct in males
 Ductus deferens in amphibians
 Vas deferens in mammals
Terminate at cloaca
 Most amniotes
 Not in higher vertebrates
Figure 14.14. Male teleost, caudal end of urogenital
system.
Summary of Embryonic Amniote
Urogenital Anatomy



Pronephros involutes
Mesonephros involutes
Metanephric kidney develops
 Vas deferens (sperm duct in
mammals)
Table 1. Terminology of
the urogenital system (book
Figure 14.21).
Urinary Bladder



Found in most vertebrates
Formation varies
 Fish- terminal segment of mesonephric duct
Large bladders- turtles and lizards
 Turtles- accessory bladder
Figure 14.15. Evolution of the urinary bladder (book figure 14.53).
Gonads


Elevated ridges medial to kidneys
Gonads enlarge, suspended by
mesenteries
 Mesorchium- males
 Mesovarium- females
Figure 14.16. Urogenital ridge
in developing embryo (book
figure 14.18).
Figure 14.17. Ovary of hagfish (book figure 14.23).
Gonads (cont.)




Bidder’s organ
 Rudimentary ovary of toads (genus
Anaxyrus—formerly Bufo)
 If testes removed, become
functional ovary
Ovotestes in fish
Both ovary and testis in lizards
Multi-lobed testis in some species of
salamanders (genus Desmognathus)
Figure 14.18. Left bidder’s organ
of male Anaxyrus.
Male Urogenital System (cont.)
Figure 14.19. Urogenital anatomy of male fishes (book figure 14.33).
Male Urogenital System (cont.)
Figure 14.20. Urogenital anatomy of tetrapod males (book figure 14.35).
Female Gonads (cont.)
Figure 14.21. Urogenital anatomy of female fishes (book figure 14.25).
Female Gonads (cont.)
Figure 14.22. Urogenital anatomy of tetrapod females (book figure 14.27).
Copulatory Organs



Claspers in cartilagenous fish
Gonopodium in teleost
Intromittent organ
 Hemipenes
 Single penis
Figure 14.23. Gonopodium of a male guppy.
Copulatory Organs (cont’d.)
Figure 14.24. Intromittent organs
in the chondrichthyans
(book figure 14.38).
Copulatory Organs (cont.)
Figure 14.25. Intromittent
organs in the turtles and
crocodylians (book figure 14.42).
Copulatory Organs (cont.)
Figure 14.26. Intromittent organs
in birds—domestic turkey (book
figure 14.44).
Copulatory Organs (cont.)



No copulatory organs
 Sperm pocketSpermatheca in most
salamanders
Rudimentary copulatory
organ
 Some amniotes
(tuatara)
Cloacal apposition
 Male and female
cloacae come together
Figure 14.27. Penis in the dog
(book figure 14.45).
Cloaca



Receives digestive, reproductive, and
urinary products and tracts
No cloaca
 Fish – may have three separate openings
 Lost in mammals above monotremes
Cloaca subdivisions:
 Coprodaeum
 Urodaeum
 Proctodaeum
Figure 14.28. Cloacal cavities and urogenital structures in a salamander.
Cloacal Subdivisions



Coprodeum
 Receives alimentary canal
 Simple columnar
Urodeum
 Receives urinary and
reproductive products
 Transitional epithelium
Proctodeum
 Associated with excretory
 Stratified squamous
Figure 14.29. Subdivisions of
cloaca shown in a lizard.
Urogenital Papilla
• Typically
found in
chondrichthyans and
squamates.
Sperm
Ureter
Ductus deferens
Figure 14.30. Urogenital papilla
in snakes.
Cloacal gland
Urogenital papilla
Cloacal cavity
Cloacal Region of a Bird
Figure 14.31. Bird cloacae (book figure 14.49).
Bird Cloaca (cont.)

Bursa of Fabricius

Lymphoid evagination off cloaca
Figure 14.32. Bursa of Fabricius
on young bird.
Figure 14.33. Histology of
Bursa of Fabricius and cloaca.
Urogenital System (cont.)
Figure 14.34. Urogenital systems
of female tetrapods (book figure
14.28).
Urogenital System (cont.)


Muellarian ducts
 In males, ducts are nonfunctional
 In females, ducts give rise to female
reproductive tract
Only left reproductive tract
 Birds and crocodiles
 Raptors have vestigial right
reproductive tract
Figure 14.35. Book
figures 14.25 and
14.27.
Reproductive Tracts of Mammals



Duplex uterus
 Monotremes and marsupials
 Separated female reproductive tracts
Bipartite uterus
 Rabbit
 Body of uterus seems unpaired, yet
has two lumens
Bicornuate uterus
 Cat
 Two uterine horns and single lumen
Figure 14.36. Morphology
of uteri (book figures 14.51-52).
Reproductive Tracts of Mammals


Bicornuate uterus
 Cat
 Two uterine horns and single
lumen
Simplex uterus
 Primates
 Large body and horns
(cont.)
Figures 14.37-38. Mammalian uteri; fused muellerian
ducts (blackened regions) and cloaca (red).
Reproduction



Most vertebrates require both sexes
Some vertebrates are asexual
 Reproduce parthenogenetically
 Some fish and lizards
Embryonic humans are asexual
 Until differentiation of sexual structures
Differentiation of Sexual Structures
Figures 14.39-40. Mesonephros contributions to male and female reproductive tracts.
Differentiation of Sexual Structures in
Mammals (cont.)



Genital tubercle
 Male - penis
 Female - clitoris
Genital folds
 Male - penis contribution
 Female - labia minora
Genital swellings
 Male - scrotum
 Female - labia majora
Figure 14.41. External genitalia of bisexual
stage of human embryo.
Differentiation of Sexual Structures in
Mammals (cont.)


Mesonephric duct
 Male - vas deferens
 Female - Gartner’s duct
Muellerian duct
 Male - portions are retained
 Female - reproductive tract
Figure 14.42. Changes in female,
mammalian urogenital system.
Differentiation of Sexual Structures in
Mammals (cont.)


Mesonephric tubule
 Male - vasa efferentia
 Female - epoophoran and paraophoran
Genital ridge
 Male - testes
 Female - ovaries
Homologous Urogenital Structures
Figure 14.43. Homologous urogenital structures in male and female mammals.
Mechanism for Elimination of
Nitrogenous Wastes
Figure 14.44. Nitrogenous
waste excretion (book figure
14.11).