Urogenital System and Kidneys

Urinary System

• The urinary system consists of organs such as kidneys, ureters, urinary bladder, and urethra.

Kidneys

• Kidneys are bean-shaped in carnivores and small ruminants, flatten-elongated in pigs, heart-shaped in horses, and completely different in large ruminants with a surface having deep fissures due to lobes.
• The cranial extremity of the right kidney fits into the renal impression of the liver.
• The right kidney is higher than the left kidney.
• Surfaces:
  • Dorsal surface: contacts with sublumbar muscles.
  • Ventral surface: contacts with parietal peritoneum.
• Borders:
  • Lateral border is convex.
  • Medial border is concave, containing a hilus.
• Renal hilus: the area where the artery, vein, ureters, and lymphatic ducts pass through.
• Renal parenchyma:
  • Cortex:
    • Reddish-brown.
    • Peripheral zone.
    • Juxtamedullar zone.
  • Medulla:
    • Dark in color.
    • Has internal and external zones.
• Renal lobes:
  • Uni-lobar:
    • Cats, dogs, horses, and small ruminants.
    • Multimedullary.
    • Cortex is fused together.
  • Multi-lobar:
    • Medulla and cortex are divided into pyramidal-shaped lobes.
    • Form a multilobular shape of the kidney.
    • Apex of each lobe is directed towards the renal sinus and forms a papilla.

Renal Pelvis

• Located within the renal sinus, it's the expanded part of the ureter within the kidney.
• In horses:
  • Very narrow.
  • Ends with two cavities known as recessus terminals.
• In carnivores and small ruminants:
  • Similar.
  • Arch-like in ruminants but T-shaped in carnivores.
• In bovines:
  • Not present.
  • Papillae of each medullary lobe drain into a calyx formed by the terminal branch of the ureters.

Ureters

• Thin bilateral tubes (3-4 mm) that connect kidneys to the urinary bladder.
• Transport urine from the renal pelvis to the urinary bladder.
• Course caudally in the sublumbar muscles.
• Open into the dorsal part of the neck of the urinary bladder.
• In horses: glandulae uretericae is located on the wall of the ureters.

Urinary Bladder (Vesica Urinaria)

• Composed of:
  • Vertex vesica.
  • Corpus vesica.
  • Cervix vesica.
• Extends into the abdominal cavity in carnivores.
• Stays within the pelvic cavity in the rest of the species.

Ligaments of the Urinary Bladder

• Ligamentum vesicae medianum:
  • Median ligament.
  • Contains urachus in the fetal period.
• Ligamentum vesicae laterale:
  • Lateral ligament.
  • Contains umbilical arteries in the fetal period.
• Round ligament:
  • Originates from the umbilical artery in the fetal period.
• Trigonum vesicae:
  • Triangular area.
  • At the base of the bladder.
  • Defined by two ureteral and urethral orifices.

Urethra

• Tubes that carry urine from the bladder to the orifices.
• Composed of:
  • Pelvic part:
    • Prostatic part.
    • Membranous part.
  • Penile part:
    • Bulbar part.
    • Terminal part.
    • Internal urethral part.
    • External urethral part.
    • Suburethral diverticulum in cows.
    • Urethralis m. Sphincter urethrae.

Female Reproductive Organs

• Composed of:
  • Ovarium.
  • Tuba uterine.
  • Uterus.
  • Vagina.
  • Vestibule.
  • Vulva.

Ovarium

• Location:
  • In dogs and cats: dorsal part of the abdomen and caudal to the kidney.
  • In ruminants: close to the ventral side of the abdomen wall, cranial to the pelvic inlet.
  • In horses: located 8-10 cm ventral to the dorsal wall of the abdomen.
  • In pigs: middle of the abdomen.
• Size:
  • Bitch: 1-1.5 cm.
  • Cat: 1 cm.
  • Cow: 4-6 cm.
  • Sheep and goat: 1.5-2 cm.
  • Mare: 8-12 cm.
• Shape:
  • Ellipsoidal in all species but bean-shaped in mares.

Uterine Tubes

• Also known as oviduct or fallopian tube.
• Receive the egg and transfer it to the uterus, where the egg gets fertilized in the oviduct.

Oviducts Parts

• Fimbriae:
  • Finger-like structure closest to the ovaries.
  • Catch the egg.
• Infundibulum:
  • Funnel-shaped structure.
  • Receive the egg after being caught by the fimbriae.
• Ampulla:
  • Middle part of the oviduct.
  • Location of fertilization and early cleavage.
• Isthmus:
  • Serve as a sperm reservoir.
  • Adhere to the epithelium and get released in time of ovulation.

Uterus

• Located between the urinary bladder anteriorly and the rectum posteriorly.
• Uterine wall structure:
  • Perimetrium (serosal).
  • Myometrium (muscular).
  • Endometrium (mucosal).
• Suspended by the broad ligament also known as mesometrium.

Uterus Compartments

• Horn.
• Body.
• Cervix.
• Cornu uteri and corpus uteri are located within the abdominal cavity dorsal to the intestines.
• The corpus is generally small, largest in the mare (horses).

Shape of the Uterus

• Straight like a V in dogs.
• Straight like a T in horses.
• Coiled ventrally on itself in ruminants.

Cervix

• Located within the pelvis.
• Located between the rectum and bladder.
• It's the structure that divides the external genital tract from the internal reproductive tract.

Compartment

• Ostium uteri internun:
  • Internal uterine ostium.
  • Has a sphincter function.
  • Allows access to the uterus.
• Canalis cervicis:
  • Consist of mucosal folds.
  • Longitudinally arranged in mares, dogs, and cats.
  • Blocked by the plicae circulares (circular folds).
  • In pigs, the mucosal fold forms the pulvini cervicales.

Vagina

• Composed of two parts: cranial and caudal.
• Median position in the pelvis.
• Contains:
  • Suburethral orifices:
    • All animals.
  • Glandulae vestibulars minors:
    • In mares, pigs, sheep, and cows.
  • Glandulae vestibulares majors:
    • In cows, sheep, and cats.

Male Reproductive Organs

• Organs:
  • Testis.
  • Epididymis.
  • Ductus deferens.
  • Urethra.
  • Penis.

Position of Testicle in Scrotum

• Ruminant:
  • Caudal part of the abdomen.
  • Vertically.
• Feline and pig:
  • Perineal region.
  • Tilted toward the anus.
• Horses and dogs:
  • Intermediate position.
  • Horizontal.

Testicles

• Two extremity:
  • Extremitas capitate.
  • Extremitas caudate.
• Two borders:
  • Free border.
  • Epididymal border.
• Two surfaces:
  • Medial and lateral.
• Two lobes:
  • Right and left lobe.

Structure of the Testes

• Tunica albuginea:
  • Fibrous capsule.
  • Contains collagen fibers, testicular artery, and testicular vein.
• Septula testis (septa):
  • Originate from the capsule fibers.
  • Lobuli testis (pyramid-shaped).
  • Originate from converging septa.
  • Located in extremitis capitis of parenchyma in horses and middle part of the parenchyma in other animals.
• Mediastinum testis:
  • Originate from converging lobuli testis.
  • Converge.
  • Located in extremitis capitis of parenchyma in horses and middle part of the parenchyma in other animals.
• Tubules of the testis:
  • Seminiferous tubules.
  • Straight tubules.
  • Rete