Comparative Anatomy
Urogenital System
Note Set 11
Chapter 15
Urogenital System

Ducts of excretory and
reproductive systems are
intimately associated
Figure 14.1: Embryonic and evolutionary
development of kidneys in vertebrates (handout).
Primitive Kidney

Archinephros- primitive excretory
kidney organ



Holonephros
Filtration system
Archinephric duct- drains to cloaca or
bladder
Figure 14.2: Hypothetical
archinephros (book figure 15.7).
Primitive Kidney (con’t)

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 14.3: Pronephros region
of primitive kidney.
Primitive Kidney (con’t)
Figure 14.4: Fate of nephrogenic mesoderm (red)
(book figure 15.8).
Figure 14.5: Pronephric,
mesonephric, and metanephric
system relationships.
Primitive Kidney (con’t)

Mesonephros
(opisthonephros)- kidney mass
caudal to pronephric region



Figure 14.6: Mesonephros of Urodele
(book figure 15.8)
Functional adult kidney of fish
and amphibians
Opisthonephros in sharks
Drained by mesonephric
(archinephric) duct
Figure 14.7: Mesonephric duct of opossum
embryo (book figure 15.19).
Primitive Kidney (con’t)

Ductus efferens:




Pronephric duct
Mesonephric duct
Archinephric duct
Anterior portion of
mesonephric tubules used
in male reproductive
system
Figure 14.8: Urogenital system and adrenal glands of
male frog.
Primitive Kidney (con’t)
Figure 14.9: Mesonephric kidneys with
mesonephric duct (black) carrying sperm and/or
urine (book figure 15.25).
Primitive Kidney (con’t)

Accessory urinary ducts
Tubules also in reproductive sys.
 Path for sperm to enter mesonephric duct (sperm duct)

Figure 14.10: Mesonephric kidneys with
separate sperm duct (red) (book figure 15.25).
Amniote Kidney

Pronephros


Mesonephros



Lost
Mainly an embryonic kidney
Involutes at birth
Figure 14.11: Metanephric kidney assuming
superior position to remainder of urogenital
system.
Metanephric kidney


Takes over functions of mesonephros
Ureter- new duct drains met. kidney
Amniote Kidney (con’t)

Mesonephric duct




Sperm duct in males
Ductus deferens in amphibians
Vas deferens in mammals
Terminate at cloaca


Most amniotes
Not higher vertebrates
Figure 14.12: Male teleost, caudal end of
urogenital system (book figure 15.18).
Embryonic Amniotes



Pronephros involutes
Mesonephros involutes
Metanephric kidney develops

Vas deferens
Urinary Bladder


Most vertebrates
Formation varies


Fish- terminal segment of mesonephric duct
Large bladders- turtles and lizards

Turtles- accessory bladder
Gonads


Elevated ridges medial to
kidneys
Gonads enlarge, suspended
by mesenteries
Mesorchium- males
 Mesovarium- females
Figure 14.13: Urogenital ridge in
developing embryo.

Figure 14.14: Ovary of hagfish.
Gonads (con’t)

Bidder’s organ
Rudimentary ovary of toads
(Bufo)
 If testes removed, become
functional ovary




Ovotestes in fish
Both ovary and testis in lizards
Multi-lobed testis in some
species
Figure 14.15: Left bidder’s organ of
male Bufo (book figure 15.23).
Copulatory Organs



Claspers in cartilagenous fish
Gonopodium in teleost
Intromittent organ
Hemipenes
 Single penis

Figure 14.16: Gonopodium on male guppy.
Copulatory Organs (con’t)

No copulatory organs


Rudimentary copulatory
organ


Sperm pocket- some
salamanders
Some amniotes (tuatara)
Cloacal apposition

Male and female cloacas
come together
Figure 14.17: Urogenital system of
female sphenodon.
Copulatory Organs (con’t)

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
reprod. tract
Figure 14.18: Mullerian ducts and
gonads of male amphibians.

Figure 14.19:
Rudimentary
oviduct of pigeon.
Copulatory Organs (con’t)

Duplex uterus



Bipartite uterus



Monotremes and marsupials
Separated female reprod.
tracts
Rabbit
Body of uterus seems
unpaired yet has two lumens
Bicornuate uterus


Cat
Two uterine horns and single
lumen
Abnormal human bicornuate uterus
Copulatory Organs (con’t)

Bicornuate uterus



Cat
Two uterine horns and
single lumen
Simplex uterus


Primates
Large body and horns
Figure 14.21: Mammalian uteri; muellerian ducts
(blackened regions) and cloaca (red) (book figure 15.47).
Cloaca


Receives digestive, reproductive,
and urinary products and tracts
No cloaca



Fish- three separate openings
Mammals above monotremes
Cloaca subdivisions:



Coprodaeum
Urodaeum
Proctodaeum
Figure 14.22: Cloacal cavities and urogenital
structures in salamanders.
Cloaca Subdivisions

Coprodeum



Urodeum



Receives alimentary canal
Simple columnar
Receives urinary and
reproductive products
Transitional epithelium
Proctodeum


Associated with excretory
Stratified squamous
Figure 14.23: Subdivisions of
cloaca shown in bird.
Cloaca (con’t)

Bursa of Fabricius

Lymphoid evagination off cloaca
Figure 14.24: Bursa of Fabricius
on young bird.
Figure 14.25: Histology of
Bursa of Fabricius and cloaca.
Reproduction


Some vertebrates require both sexes
Some verts. are asexual
Reproduce parthenogenetically
 Some fish and lizards


Embryonic humans are asexual

Until differentiation of sexual structures
Differentiation of Sexual Structures
Figure 14.26: Mesonephros contributions
to male and female reproductive tracts.
Differentiation of
Sexual Structures (con’t)

Genital Tubercle
Male- penis
 Female- clitoris


Genital Folds
Male- penis contribution
 Female- labia minora


Genital Swellings
Male- scrotum
 Female- labia majora

Figure 14.27: external genitalia of
bisexual stage of human embryo
(book figure 15.48).
Differentiation of
Sexual Structures (con’t)

Mesonephric Duct
Male- vas defferens
 Female- gartner’s duct


Muellerian Duct
Male- portions are retained
 Female- reproductive tract

Figure 14.28: Changes in female,
mammalian urogenital system
(book figure 15.13).
Differentiation of
Sexual Structures (con’t)

Mesonephric Tubule
Male- vasa efferentia
 Female- epoophoran and paraophoran


Genital Ridge
Male- testes
 Female- ovaries

Homologous Urogenital Structures
Figure 14.29: Homologous urogenital structures in male and female mammals
(book tbl 15.3).
Literature Cited
Figure 14.1- Trauth, Stan. Handout.
Figure 14.2, 14.4, 14.6, 14.7, 14.9, 14.10, 14.12, 14.15, 14.21, 14.27, 14.28, 14.29- Kent, George C. and
Robert K. Carr. Comparative Anatomy of the Vertebrates. 9th ed. McGraw-Hill, 2001.
Figure 14.3- http://people.eku.edu/ritchisong/342notes10.html
Figure 14.5- http://connection.lww.com/Products/sadler/imagebank.asp
Figure 14.8- http://www2.vscc.cc.tn.us/MSD/BIO/1020/Lab7ChordateII.htm
Figure 14.11- http://www.med.unc.edu/embryo_images/unit-genital/genital_htms/genital018.htm
Figure 14.13, 14.14, 14.17, 14.18, 14.19- Kardong, Kenneth V. Vertebrates: Comparative Anatomy,
Function, Evolution. 4th ed. McGraw-Hill, 2006.
Figure 14.16- http://www.th.physik.uni-frankfurt.de/~brandste/aqua/fauna/zucht.html
Figure 14.20- http://137.222.110.150/calnet/vetrep7/page2.htm
Figure 14.22- Sever, David. Reproductive Biology and Phylogeny of Urodela. Vol 1. Science
Publishers, Inc, 2003. pg 334
Figure 14.23- http://member.rivernet.com.au/balehirs/Bishyp6nroBirdNests.htm
Figure 14.24- http://www.uic.edu/classes/dh/dh110/Immunology_files/
Figure 14.25- http://www.upei.ca/histology/html/bursa_fabricus.html
Figure 14.26- http://www.mun.ca/biology/desmid/brian/BIOL3530/DB_Ch12/DBNGerm.html