Urinary System  Kidney = Nephrons dorsal to coelom.  Nephron = Tubular structure that reabsorbs substances from a coelomic fluid-derived or plasma-derived filtrate.

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Urinary System
 Kidney = Nephrons dorsal to coelom.
 Nephron = Tubular structure that
reabsorbs substances from a coelomic
fluid-derived or plasma-derived filtrate
Nephron Structure
 Coelomic funnel = cilliated opening of
nephron to coelom – where coelomic
fluid enters the nephron
 Bowman’s capsule = end of nephron
that surrounds a mass of capillaries
(Glomerulus) – where plasma enters
the nephron
 Concentrated fluid waste (urine) is
formed that usually is rich in
nitrogenous (e.g. urea, uric acid)
waste.
Human Kidney Development
Nephron Development
 Intermediate mesoderm forms nephric
tubules in nephric ridges.
 Some remain contiguous with the
coelom of the lateral plate mesoderm.
dorsal
aorta
int. mesoderm
coelom
Nephron Function
Vertebrate Embryo (section)
neural
crest
cells
sclerotome
dermatome
myotome
splanchnic
mesoderm
somatic
mesoderm
gut
intermediate
mesoderm
lateral
plate mesoderm
Vertebrate Embryo (section)
neural
crest
cells
sclerotome
dermatome
myotome
splanchnic
mesoderm
somatic
mesoderm
gut
intermediate
mesoderm
lateral
plate mesoderm
Vertebrate Embryo (section)
sclerotome
dermatome
myotome
dorsal &
ventral
mesenteries
(splanchnic mesoderm)
gut
intermediate
mesoderm
coelom
lateral
plate mesoderm
Vertebrate Embryo (section)
vertebra
horizontal
septum
dermatome
myotome
dorsal &
ventral
mesenteries
(splanchnic mesoderm)
gut
intermediate
mesoderm
coelom
lateral
plate mesoderm
Vertebrate Embryo (section)
vertebra
horizontal
septum
dermatome
myotome
dorsal
mesentery
(splanchnic
mesoderm)
gut
intermediate
mesoderm
coelom
lateral
plate mesoderm
Nephron Development
Kidney Regions
 Nephric ridges
 Pronephros = Segmental; develops 1st;
coelomic funnel (Lost in adults, except Myxini).
 Mesonephros = Segmental; posterior to
pronephros; coelomic funnel &
Bowman’s capsule (Lost in adult amniotes).
 Metanephros = Develop segmentally
but obscured by nephron proliferation (but
segmental in hagfishes); posterior to
mesonephros; Bowman’s capsule.
Vertebrate Mesoderm
Somitomeres
Somites
Lateral Plate Mesoderm
Intermediate
Mesoderm
Kidney Development
 Archinephric duct = Pronephros
initiates formation; drains pro-, meso-, &
sometimes meta-nephros.
 Accessory duct = Develops
longitudinally from the archinephric duct
(in some elasmobrachs and salamanders);
drains the meso- and meta-nephros.
 Metanephric Duct (ureter) = Develops
as bud from base of the archinephric
duct; drains metanephros (Only in amniotes).
Hagfish Kidney
pronephros
mesonephros
metanephros
archinephric
duct
Opisthonephric Kidney
pronephros
mesonephros
metanephros
accessory
duct
archinephric
duct
Metanephric Kidney
pronephros
mesonephros
metanephros
archinephric
duct
Adult Kidney Types
 Holonephric Kidney = pro-, meso-,
and segmental meta-nephric tubules
 Opisthonephric Kidney =
mesonephric and metanephric tubules
drained by archinephric and possibly
accessory ducts.
 Metanephric Kidney = composed only
of non-segmental metanephric tubules;
drained by metanephric duct (ureter).
Human Kidney Development
Human Urinary
Adult Kidney
Group
Myxini
Petromyzontida
Chondrichthys
Actinopterygii
Dipnoi
Lissamphibia
Mammalia
Reptilia
Type
holonephric
opisthonephric
opisthonephric
opisthonephric
opisthonephric
opisthonephric
metanephric
metanephric
Tubules
pro-, meso-, & meta-
meso- & metameso- & metameso- & metameso- & metameso- & metametameta-
Subphylum Vertebrata
metanephric
kidney;
ureters
opisthonephric kidney
function of pronephric tubules reduced
Nitrogenous Waste
 Ammonia = NH4+, toxic, excreted in large
amounts by many aquatic organisms (not all).
hagfishes, lampreys, Actinopterygii, lungfishes,
coelacanths, amphib., crocodylians, aquatic turtles.
 Urea = CO(NH2 ), less toxic,
gnathostomes (Actinopterygiians use it less,
Chondrichthyians and Mammals most).
 Uric Acid = C4O3N4H3, less toxic, slightly
soluble in water, precipitates in cloaca.
Requires least amount of water to excrete.
Only reptiles produce in large amounts.
Subphylum Vertebrata
uric
acid
urea
ancestrally
ammonia
function of pronephric tubules reduced
Reproductive System
 Gonad = Organ that produces gametes
and hormones.
 Testis = Male gonad
 Seminiferous tubules = site of sperm
formation in testis.
 Ovary = Female gonad
 Follicle = Specialized cells that surround
a developing ovum in the ovary.
 Gamete = 1n sex cell (sperm/ ovum).
Gonadal Histology
Gonad Development
 Indifferent gonad (Genital ridges) = the early
gonad; neither testis nor ovary.
 Germ cells = will form gametes.
Migrate from endoderm via dorsal mesentery.
 Primary Sex Cords = coelomic mesothelium
of ridge grows into mesenchyme of ridge.
♂ primary sex cords  seminiferous tubules
♀ primary sex cords  form and disappear
 Secondary Sex Cords = mesothelium again
grows into mesenchyme of genital ridge.
♀ secondary sex cords  ovarian follicles
Vertebrate Embryo (section)
vertebra
horizontal
septum
dermatome
myotome
genital ridge
dorsal
mesentery
(splanchnic
mesoderm)
gut
intermediate
mesoderm
coelom
lateral
plate mesoderm
Gonad Development
Gonad Development
Male Urogenital Ducts
 ALL Non-amniotes = archinephric ducts drain
kidneys.
 Amniotes = metanephric ducts drain kidneys.
 Hagfishes & Lampreys = no testis ducts.
 Gnathostomes = archinephric ducts drain the
testes (also drain the kidneys in all nonamniote ganthostomes).
EXCEPTION - Teleosts & Amia = new
gonoduct drains testes (not the archinephric
duct)
Hagfish and Lamprey Male Ducts
kidney
testis
abdominal
pore
archinephric
duct
Male Genital Ducts (Non-amniote)
kidney
testes
abdominal
pore
archinephric
duct
Male Genital Ducts (Non-amniote)
kidney
testes
abdominal
pore
archinephric
duct
Male Genital Ducts (Amniote)
metanephric
ducts
kidney
testes
archinephric
duct
Male Genital Ducts (Teleost or Amia)
kidney
testes
gonoduct
archinephric
duct
Female Urogenital Ducts
 ALL Non-amniotes = archinephric ducts drain
kidneys.
 Amniotes = metanephric ducts drain kidneys.
 Hagfishes & lampreys = no ovary ducts.
 Gnathostomes = Müllerian ducts open to the
coelom capture ova. (archinephric ducts lost
in female amniotes)
In birds the right Müllerian duct is reduced
and the right ovary is usually absent
EXCEPTION - Teleosts & Amia = new
gonoduct not open to coelom captures ova
(not the Müllerian duct)
Hagfish and Lamprey Female Ducts
kidney
ovary
abdominal
pore
archinephric
duct
Female Genital Ducts (Non-amniote)
ovaries
kidney
Müllerian
duct
archinephric
duct
abdominal
pore
Female Genital Ducts (Amniote)
ovaries
metanephric
ducts
kidney
Müllerian
duct
Female Genital Ducts (Teleost or Amia)
kidney
ovaries
gonoduct
archinephric
duct
Female Genital Ducts
Teleosts
Male Genital Ducts
Male Urogenital Ducts
Group
Petromyzontida
from Kidney
archinephric
archinephric
Chondrichthys
accessory & arch.
Myxini
Polypter-, Ascipenser-,
& Lepisosteiformes
archinephric
Teleostei & Amia
archinephric
archinephric
Dipnoi
Lissamphibia
Mammalia
Reptilia
accessory & arch.
metanephric
metanephric
from Testis
none
none
archinephric
archinephric
male gonoduct
archinephric
archinephric
archinephric
archinephric
Female Urogenital Ducts
Group
Myxini
Petromyzontida
Chondrichthys
Polypter-, Ascipenser-,
& Lepisosteiformes
Teleostei & Amia
Dipnoi
Lissamphibia
Mammalia
Reptilia
from Kidney
archinephric
archinephric
archinephric
archinephric
from Ovary
none
none
Müllerian duct
Müllerian duct
archinephric
archinephric
archinephric
metanephric
metanephric
female gonoduct
Müllerian duct
Müllerian duct
Müllerian duct
Müllerian duct
Subphylum Vertebrata
archinephric
duct lost in
females; metanephric serves
archinephric duct
kidneys
serves testes in males;
Müllerian duct in females
Class Actinopterygii
Müllerian duct
lost; new
gonoducts
for ovary
and testis
Amniota
right ovary
and oviduct
(Müllerian)
reduced or
lost
Human Genitalia
 The human genitalia are sexually
homologous developing from the
“same” developmental precursors.
Human Genital Development
urinary
Early
Male
reproductive tubercle glans
penis
folds
scrotum
Female
glans
clitoris
labia
Human Genitalia Development
Human Genital Intersexuality
Human Female Reproductive
Human Male Reproductive
Gonadal Descent
 In both male and female humans the
gonads move inferiorly, in males
dramatically so into the scrotum.
Cryptorchidism
Comparative Vertebrate Genitalia
 Genitalia = external or extruded
reproductive structures
 Intromittent organ = structure for
transfer of sperm to facilitate internal
fertilization (but not necessary for it);
Intromittent organs evolved repeatedly.
 Internal fertilization:
Chondrichthyans, Amniotes, &
Miscellaneous others
Cloaca
 Cloaca = (sewer in Latin) ectodermal,
posterior chamber; intestine, urinary
system, and reproductive system
“empty” here.
 Cloaca lost in Therian mammals,
Actinopterygiians, and chimaeras.
Separate, external anal and urogenital
openings.
Chondrichthyan Male Genitalia
 Claspers = paired pelvic fin derived
structures; grooved for sperm
transfer.
Amniote Genitalia
 Amniotes ancestrally develop a genital
tubercle.
Homologous to glans penis and
glans clitoris in mammals.
 Genital tubercle often regresses in
female non-mammalian amniotes.
 Lepidosaurs and most birds have
secondarily lost the genital tubercle.
Amniote Genital Development
urinary
Early
Male
reproductive tubercle glans
penis
folds
scrotum
Female
glans
clitoris
labia
Male Genitalia
 Median penis = in amniotes; derived
from genital tubercle; erectile tissue and
a sulcus spermaticus (groove).
Secondarily lost in lepidosaurs and
most birds (ratites, ducks & geese retain)
Mammals = closed sulcus spermaticus
that in therians also extends the urethra
Many mammals have a baculum (bone
in the penis)
Testudinean Male Genitalia
Crocodylian Genitalia
Rhea Male Genitalia
Monotreme Male Genitalia
 Slightly forked penis (four-headed).
 Testes remain abdominal (no scrotum).
echidna penis
Therian Testes
 Scrotum sac containing the testes
outside of the male’s body.
 Adult testes usually are in a scrotum or
to under the skin’s surface.
Marsupial Genitalia
 Forked penis in most male marsupials.
(scrotum anterior to penis)
 Paired vaginas in all female marsupials.
sugar glider penis
Kangaroo Male Genitalia
Eutherian Genitalia
 Simple penis in most male euterians.
(scrotum posterior to penis)
 Single vagina in all female eutherians.
Hyaena Genitalia
two female
hyaenas
Lepidosaur Male Genitalia
 Hemipenes = paired cloacal
structures; grooved for sperm
transfer.
cloaca lost
claspers
Subphylum Vertebrata
cloaca
genital
tubercle;
median
penis &
clitoris
forked
penis &
paired
vaginas
sulcus
spermaticus
closed
(tubular)
vagina(s);
scrotum;
cloaca lost
(or reduced)
hemipenes;
gen. tubercle
lost
Amniota
genital
tubercle
lost in
most
genital tubercle - median
penis & clitoris

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