Urogenital

• Urogenital System


  From the Greek word ouro which means "urine" and Latin word genitalis which pertains to "genitalia"

  
• Components of the Urogenital System

  • Urinary System
  • Reproductive System

  
• Urinary System


  • Primarily responsible in the removal of wastes from your blood in the form of urine

  
• Reproductive System


  • Responsible in producing, maintaining, and transporting the sperm and egg cells
• Functions of the Urogenital System

  • Excretion
  • Maintains water balance
  • Assist in maintaining electrolyte / salt balance
  • Assist in maintaining acid base / pH balance of blood
  • Secretion of hormones
  • Reproductive activity
• Kidney


  A pair of bean-shaped organs which filter blood and produce urine

  
• External Anatomy of the Kidney

  • Located on either side of the spine in the retroperitoneal space
  • Roughly the size of your fist, with the male kidney typically a bit larger than the female kidney
  • Left kidney located at about the T12 to L3 vertebrae, right kidney lower due to displacement by the liver
  • Covered by a fibrous capsule and shock-absorbing layer of adipose tissue

  
• Internal Anatomy of the Kidney

  • Renal Cortex: Granular due to presence of nephrons
  • Renal Medulla: Contains multiple pyramidal tissue masses called renal pyramids, with spaces called renal columns for blood vessels
  • Renal Pelvis: Leads to the ureter, branches into major and minor calyces
  • Renal Hilum: Entry and exit site for vessels, nerves, lymphatics, and ureters

  
• Renal Circulation


  1. Blood flows to kidneys via renal arteries from aorta

  2. Blood enters renal capillaries where filtration occurs

  3. Filtered blood leaves kidney via renal veins to inferior vena cava

  
• Basic Patterns of Vertebrate Kidney

  • Glomerulus: Tufts of microscopic capillary-like arterial loops that act as a simple filter
  • Renal Tubules: Collect glomerular filtrate and return nutrients, fluids, and other substances to blood
  • Longitudinal Excretory Ducts: Develop from anterior to posterior, transporting urine to cloaca or urogenital sinus

  
• Evolutionary Development of Kidney

  1. Hypothetical Ancestral Kidney

  2. Archinephros

  3. Pronephros

  4. Mesonephros

  5. Metanephros

  
• The Amniote Kidney


  • Cortex: Outer kidney substance containing renal corpuscles
  • Medulla: Inner substance containing loops of Henle and collecting tubules
  • Renal Papilla: Blunt tip of each renal pyramid projecting into renal pelvis
  • Capsule: Connective tissue surrounding the kidney

  
• Extrarenal Salt Excretion in Vertebrates

  • Fishes: Chloride secreting glands on gills, rectal glands in elasmobranchs
  • Amphibians, Reptiles, Birds: Salt glands
  • Mammals: Sweat glands, skin
• Ureter


  • Tube that transfers urine from kidneys to bladder, with 3 layers: mucosa, muscularis, adventitia

  
• Urinary Bladder


  • Flexible storage for urine until released through urethra, embryonic origin from ventral cloacal wall and allantois

  
• Urethra


  • Duct that transmits urine from bladder to exterior, with walls of epithelial, smooth muscle, and connective tissue, and external/internal sphincters

  
• Gonads


  Produce gametes and synthesize steroidal hormones, essential for morphogenesis and maintenance of sex organs and characters, and reproductive behavior
• Gonadal Primordia


  1. Arise from genital ridge in splanchnic mesoderm, with primordial germ cells migrating to colonize early gonad rudiments

  2. In males, germ cells establish in seminiferous tubules in medulla

  3. In females, cortex expands forming ovarian follicles

  
• Embryonic Gonads


  The paired gonads arise from the genital ridge, initially a thickening in the splanchnic mesoderm to which adjacent mesenchyme cells contribute

  
• Urogenital Ridge


  • Posterior part: paired urogenital ridges arise within the roof of the coelom
  • Medial ridges: are the genital ridges and give rise to the gonads
  • Lateral nephric ridges: give rise to the kidney and its ducts

  
• Primordial germ cells


  Develop into eggs or sperm, arise outside the gonads, migrate to them, and colonize the early gonad rudiments

  
• Seminiferous Tubules


  In males, arriving germ cells establish residence in the medulla, which develops into the seminiferous tubule

  
• Ovarian Follicles


  In females, the cortex expands, forming secondary sex cords that house the follicles
• Embryonic Formation of the Gonad

  1. Thickening of the genital ridge and inward movement of adjacent mesenchymal cells give rise to a swelling, the genital ridge, from the roof of the coelom

  2. Primordial germ cells arriving from distant locations outside the embryo usually take up residence in the indifferent gonad

  3. In males, the medulla enlarges to become the testis cords that will form the seminiferous tubules

  4. In females, the cortex expands, forming secondary sex cords that house the follicles

  
• Testes


  • Mature testes are generally smaller than ovaries because sperm are exceedingly tiny (three and one-half billion per cc in a rooster)
  • The testes of placental mammals, however, are larger than ovaries because the eggs are microlecithal, and only a few are present at a time
• Male Genital Ducts


  • Wolffian Duct (Mesonephric Duct) gives us the internal genital structures
  • Epididymis: narrow, tightly-coiled tube that is attached to each of the testicles (the male sex glands that produce sperm)
  • Vas deferens: a coiled tube that carries the sperm out of the testes
  • Seminal vesicle: two small glands that store and produce the majority of the fluid that makes up semen

  
• Intromittent Organs


  • Elasmobranchs: grooved fingerlike claspers, which are modified pelvic fins
  • Teleosts: a modified anal fin, or gonopodium, serves for sperm transfer
  • Frog Ascaphus: a permanent tubular, tailike extension of the cloaca
  • Male snakes and lizards: have hemipenes, a pair of protrusible saclike diverticula stored in an inverted position in pockets under the skin at the entrance to the cloaca
  • Male turtles, crocodilians, a few birds (ostriches, ducks, others) and monotremes: exhibit an unpaired erectile penis
  • Placental mammals: the penis develops from an embryonic genital tubercle and a pair of genital folds that border the urogenital sinus in the embryos of both sexes
• Ovaries


  • The primary female reproductive organs responsible for producing eggs (ova)
  • It plays a crucial role in the reproductive process by facilitating ovulation, the release of mature eggs from the ovaries
  • The structure and function of ovaries can vary among different groups of vertebrates, reflecting adaptations to their specific reproductive strategies and environments
• Ovaries


  • Teleosts: ovaries have a central cavity where eggs are discharged; continuous with oviduct or partially surrounded by an oviducal funnel of peritoneal folds that form a tube
  • Anurans and Urodeles: folded, thin-walled sacs
  • Nonavian reptiles, birds, monotremes: show numerous internal, irregular, fluid-like lacunae
  • Fishes other than teleosts, turtles, crocodiles, therian mammals: ovaries are compact
• Ovaries


  • Germinal epithelium - the epithelial layer lining the ovary's surface
  • Graafian follicles - fluid-filled antra within the egg follicles in placental mammals
  • Corpus Luteum - temporary endocrine structure involved in hormone production to support pregnancy

  
• Translocation of Mammalian Gonads

  1. Initial Position: The embryonic gonads (testes in males, ovaries in females) start developing near the kidneys

  2. Connection to Genital Swellings: Ligaments connect the embryonic gonads to coelomic floor to one of the genital swellings, which are shallow evaginations of the embryonic coelom

  3. Elongation and Displacement: As the fetus grows, these ligaments elongate. So, the gonads are pulled downward towards the genital swellings

  4. Final Position: Testes displaced farther caudad than ovaries, entering scrotal sacs

  
• Scrotal sacs


  • Lined by coelomic peritoneum located in the internal spermatic fascia
  • Testes housing: In scrotal sacs (e.g., ungulates, carnivores, some marsupials, and higher primates), Lowered and retracted at will in others (e.g., rabbits, bats, a few rodents, some lower primates)
  • Inguinal canal - passageway between abdominal and scrotal cavity
  • Inguinal ring - entrance to the canal
  • Spermatic cord - structure composed of the spermatic duct and the spermatic arteries, veins, lymphatics, and nerves, all wrapped in the internal spermatic fascia and all of which are dragged into the scrotal cavity along with the testis

  
• Female Genital Tracts below Placental Mammals

  • Paired muscular and glandular oviducts
  • Ostium: opens into coelom
  • Oviducal funnel (infundibulum): a structure at the entrance of the oviduct that collects eggs from the coelom
  • Differences in regional specializations support species-specific functions such as: collecting eggs from coelom, coating with protective or nutrient substances, temporary housing for eggs or embryos, receive male intromittent organ, store viable sperms
• Female Genital Tracts below Placental Mammals


  • Female duct differentiate from a pair of Müllerian ducts which develop in both sexes but do not persist in males
  • Spermathecae: are dorsal diverticula of the cloaca or tubular crypts found in the oviducal lining, present in many female urodeles, lizards, snakes, and domestic fowl, store sperm received during mating for future ovulation

  
• Vertebrate Group/ Class


  • Sharks: Muellerian ducts give rise to oviduct with shell gland and uterus
  • Teleosts: Not homologous with other vertebrates, arise from coelomic peritoneum folds created by genital ridges, continuously open to ovarian cavity
  • Amphibians: Richly supplied with glands for protective jelly envelopes, caudal portions become voluminous thin-walled ovisacs
  • Reptiles, birds and monotremes: Female tracts closely conform to basic pattern, differentiation of muellerian ducts may vary, albumen glands (magnum in birds) and shell glands (uterus in birds) present
• Female Tracts of Placental Mammals


  • Paired muellerian ducts giving rise to female genital tract
  • Unite at caudal ends to form unpaired terminal passageways
  • Terminates in unpaired vagina
  • Oviducts: Tubular structures that transport eggs from the ovary to the uterus
  • Uteri: Structures where embryos develop, often fused to varying degrees
  • Vagina: The passage connecting the uterus to the exterior, facilitating mating and birth of offspring
• Oviducts


  • In mammals are also called as Fallopian tubes, and are relatively short, small in diameter (accommodating microlecithal eggs), more or less convoluted, and lined with cilia
  • Ovarian bursa: a membranous fold of peritoneum envelops the ovary and the oviducal funnel, entrapping them and a small portion of the coelom in a cul-de-sac, increases the probability that ovulated eggs will enter the oviduct rather than be lost in coelomic fluid, perhaps to implant somewhere in the coelomic cavity

  
• Type of Uterus


  • Duplex uterus: two completely separated uteri (Monotremes and marsupials)
  • Bipartite uterus: body of uterus seems unpaired yet has two lumens (Rabbit)
  • Bicornuate uterus: Two uterine horns and single lumen (Cat)
  • Simplex uterus: Large body and no horns (Primates)

  
• Uteri


  • Cervix: narrow neck of the uterus that protrudes into the vagina (as the lips of the cervix)
  • Os Uteri: opening of the uterus into the vagina
  • Endometrium: uterine lining, becomes highly vascular under the stimulus of hormones before implantation of blastocysts
  • Myometrium: uterine wall, assists in ejection of the young at birth, provided it, too, has been hormonally prepared

  
• Vagina


  • Terminal portion of muellerian ducts
  • Varies in opening: to urogenital sinus or directly to exterior
  • Lined with cornified epithelium for penis reception
  • Urogenital sinus: A derivative of the cloaca in rodents, where both waste from the urinary tract and reproductive materials from the genital tract can pass through