Urogenital System
The Urinary System
Components: Kidneys and Associated Tubules
Function: Waste elimination
Feces deals with Digestive system
Kidney main organ for excretion/waste excretion
Mammalian Kidney (picture) Not all kidneys like these, more primitive kidneys
Outermost layer is the renal capsule – protects the kidney
Cortex
Medulla – inside, composed of renal pyramids microscoping components
Minor Calyx
Major Calyx
Out through the Ureter as urine for mammals
Structure of the Kidney
Uriniferous tubule one of the most basic units of the kidney
Starts off as a blood vessel supplied by renal artery
Blood vessel ends in Glomerulus – for filtration
Renal capsule - receive the filtered material into
Nephron – Proximal, Intermediate, Distal
Collecting Tubule to Calyx
Path of blood
(Outside) Renal artery – into branchings of blood vessels and enters glomerulus
(for filtration) – forced into renal capsule – proximal, intermediate, distal tubules
(reabsorption of salt and water) – collecting tubules – out – to the ureter and out of the
body
Embryonic Origins of the Kidney
Origin: Expansion of intermediate mesoderm develops from Nephric ridge
After Nephric ridge develops, Nephrotome like myotomes (mostly stem cellular
in origin) will develop
Within Medial end of Nephrotome, develop into glomerulus found in both
sides paired
Distal end develop common nephric duct serve as pathway for urine or
excretory material
Plan: Coelom and Nephric duct both sides will develop uriniferous tubule
Development of kidney is Tripartite (three parts in higher vertebrates)
In other there will only be one or two parts
Pronephros – develop first, usually found in fish
Mesonephros – middle, middle cartilagenous fish, amphibians
Metanephros – usually kidney found in mammals
Develop sequentially pronephros developing first
Pronephros
anterior, tubules, pronephric duct
Glomeruli extends from roof of coelom and filters into them
Usually transient found in fish
Glomerulus extend towards coelom and filter whatever substances
there , after secretion waste products outward through
ducts
Usually found in fishes, pronephros can still develop in other parts of the
kidney or fused with other components
Mesonephros
middle, Taps into pronephric tubules
In a way branching out of pronephros
Embryonically functional, in lower vertebrates or middle vertebrates they
can persist into adulthood
Opisthonephros – sometimes if they have posterior tubules developing
into pronephros, adult form of kidney in sharks
Have pronephric orgins
Metanephros
posterior, arises from mesonephros
Adult kidney we have
Grows into posterior region of the nephric ridge
Phylogeny of the Kidney
More primitive vertebrates have pronephros (agnathans, some fish)
Pronephric duct – connected to the pronephros drain out the primitive
kidney they have
Glomus – cluster of glomeruli for filtration, after filtration pronephric duct and
out of the body
Mesonephros – pronephros will degenerate, sharks teleosts and amphibians,
develop into further tubules, branches out, from inside the body, filtration
out through mesonephric duct, earlier called pronephric duct
since branchings of pronephros that develop into mesonephros more
appropriately named mesonephric duct
Kidney Phylogeny: Tetrapods
Metanephros – mesonephros degenerate and development of new tubules
Connected tubules connected to adult kidneys connected to Cloaca and out of the
body
Cloaca not present in all organisms
A lot have misconception that higher vertebrates such as mammals will not have
pronephros or mesonephros they will have embryonically but
degenerate and branch out to metanephros
Function: Excretion
Removal of byproducts of metabolism
Carbon dioxide, water
Nitrogenous waste (ammonia)
Three main types of excretory materials in vertebrates classified as:
Ammonotelism – organisms that secrete ammonia, ammonia diffuses out
through epithelium (gills) and usually washed away from
water
Ammonia highly toxic, excreted by fish
Ammonia comes from nitrogen metabolism
Body have to excrete toxic products so as not to interfere with
normal metabolic functions
Uricotelism – secrete uric acid, usually found in birds and reptiles
How is it significant in terms of habitat? sludgelike – mostly solid,
organisms are usually terrestrial, Not much water
Significant in terms of water conservation
Sludge is filtered in kidney, goes into cloaca with other elements
and compounds
Ureotelism – different compound is secreted. Urea is secreted Uric acid
and urea are not toxic forms
Ammonia is converted to Urea and Uric acid
Organisms don’t live in water so have to convert it to non toxic
form for metabolic functions not to suffer
Urea excreted in the form of urine with a lot of other compounds
Excreted in the form of urine
Function: Osmoregulation
Regulation of body salt and water levels, problematic for animals that live in the water
Kidney (absorption of salt and water)
Cloaca seen in birds (Ureotelic organisms)
Large intestine (reabsorption of water so as not to allow organisms to dessicate)
Urinary bladder (water absorption)
Osmoregulation: Elimination and conservation
Filtration kidneys: usually found in invertebrates, secretion kidneys, dependent on
body secretions, glomerular filtrate, secretions along tubules, reabsorption of
substances by the tubules
Depending on habitat and need for osmoregulation they will have diff. features
Glomerulus size, presence of glomerulus
Tubule length - how much salts or water reabsorbed
Loop of Henle – found in mammals, loop within tubules of intermediate
Vasa recta – assoc. to loop of henle for more reabsorption of water
Osmoregulation: Elimination and conservation
Elimination
Freshwater fish – large glomeruli for filtering solutes in its blood to keep salt
level homeostatic to keep it roughly equal, long distal tubule for more salt
reabsorption, filter a lot of salt whatever filtrate left, salts will be
reabsorbed
Water moves in too much water it will bloat and eventually burst
Has to have salts for high metabolic function
Conservation
Marine fish – no glomerulus, no distal tubules for extra salt
reabsorption,secretion-dependent, tissues will have lower
concentration of salt, in order for fish to not lose
solute it will have no glomerulus, no distal tubules
Terrestrial – loop of henle modification, mostly in dessicating and drying
environments,extra effort in reabsorption of water in loop
of henle
Reproductive System
Contain Gonads, secretions, hormones, gametes and associated ducts
For Females (image)
Tunica albuginea - outermost
Cortex
Medulla – innermost, like in kidneys
Ova – primary oocytes, secondary oocytes
Follicle Cells – in between them
Eggs are stored in the ovaries
Eggs go to the fallopian tube then uterus
When the egg is fertilized, it is in uterus it will stay there
When not fertilized, flushed by blood by menstruation
For males semen is usually formed in the testes
Seminiferous tubules move to rete testis then stored in the epididymis
Mature sperm cells outside or progenitor cells, earlier stages of development
when get to lumen stored in the middle
Lumen
Epithelial layers
Embryonic Origin
Forms in the genital ridge
Undifferentiated gonads – there is no distinction bet. males and females
Extraembryonic: germ cells come from this
In Females: migrate into cortex
In Males: migrate into medulla
Organs: salvaging from urinary tract in order to form their own tubules
Embryonic Origin: Gonads
Wolfian duct develop into several ducts
Mullerian duct regenerate
These ducts connected to the testes sometimes can be the ureter
If no male hormoness mulfian
Duct Fates
Pronephric duct initially connected to 1. Kidney (E) – eventually connected to 2.
Adult Testes (Vas deferens)
Wolfian duct initially be the 1. Mesonephros (E) – eventually be the 2.
Adult Kidney (Ureter)
Mullerian duct – Parallel; Wolffian – Female Reproductive System
Oogenesis
Start of with primary oocyte undergoes Meiosis
4 products 1st product is the Mature Ovum which can be fertilized and polar
bodies that can regenerate – for nutrition, contribute cytoplasmic material to
ovum, nutrients organelles for future organisms or babies
Cross section of cat ovary
Tunica
Cortex and medulla
As eggs mature they migrate inwards
Spermatogenesis for males (image up)
There will be no polar bodies
One parent cell give rise to Spermatids – adult sperm cell
In many organisms there will be two ovaries (paired)
In other vertebrates only one ovary will be functional
Specifically in lamphreys one gonad will fail to develop
Sometimes it degenerates sometimes it fuses
Essentially it will produce just one
Comparative Urogenital Anatomy – Females
Agnathans (lamphreys)
Ovary will not be connected to any duct
Eggs directly deposited to the coelom
Eggs can exit through pores of the body
Ophisthonephros – derivative of the mesonephros with addition of posterior
tubules
Will still have posterior tubules leading to the mesonephric duct
Osteichthyes
Ovary separate outpocketings leading out of the body, for excretion
Sharks
Smaller ophistonephros
Tetrapods
Metanephros
In Amphibians
Kidneys – connected to pronephric duct, Ovary lead to ovisac and lead to
cloacal opening, cloaca for wastes, secretions and other reproductive functions
Comparative Urogenital Anatomy – Males
Area for ejaculation and waste excretion the same
Agnathans
Testis separate
Opisthonephros for excretion of waste
Gar Sturgeon
Share the same, opisthonephros
Sharks
Testis found anteriorly, opisthonephros posterior,share the tubules
Amphibians
separate, will still share same cloacal opening for removal wastes
Amniotes
have the testis leading out to wolfian duct then metanephros then lead out to
ureter
Copulatory Organs
Ussually found in males
Intromittent organs for delivering sperm
Chondricthyes – claspers, one clasper to cloaca and other ridges for delivering
sperm into the cloacal opening of another organism
Teleosts – pelvic and anal fins modified
Gonopodium modification for direct delivery of sperm
Anurans – amplexus, mating ritual males have larger, stimulate them to release
their sex cells, male frog will be on top of the female frog
Urodeles – spermatophore packets of sperm and spermatecha found in females
for storing of sperm
Male release spermatophore like a capsule and female bites of the cap bag
of sperm
Apodans – cloacal eversion, amphibians, caecilians limbless salamanders look
like snakes, when they mate they will have cloaca diversion, where sperm
will be deposited
Caudata and urodela, Salamanders Anura and caecillians
Squamates
snakes and lizards, hemipenis – retract in side body
Crocodylians, rhynchocephalians, Testudines, some birds and mammals – true
penis, big mass of areas where blood can be deposited
Some birds – rub cloacas for cloacal transfer