ANSC 3040 - Midterm

• Sex is determined at fertilization by the chromosomal makeup of the fertilizing sperm cell, which delivers either an X (female) or Y (male) chromosome
• Sexual dimorphism occurs later in development
• Organs of the HPG axis

  • Hypothalamus
  • Pituitary
  • Gonads
  • Ovary
  • Testis
• Testis = spermatogonial stem cells; Ovary = oogonia
• Every cell contains the same genome. The difference lies in their 'Epigenetics'
• Cell differentiation after fertilization

  Results in the formation of the zygote, with differentiation markers being erased
• Early embryogenesis

  Occurs with highly specialized cells, totipotent cells, inner cell mass (ICM), trophectoderm (TE), pluripotent cells capable of differentiating into any type of embryonic or extra-embryonic cells
• Testes Descent

  Development and regression of the gubernaculum depends on secretion of insulin like-3 (INSL3) and testosterone by Leydig cells
• Primordial Germ Cells (PGCs)

  Founder cells for the germline, migrate to the gonadal ridge, interact with gonadal somatic cells for sex-specific commitment
• Sex is determined at fertilization

  by the chromosomal makeup of the fertilizing sperm cell, which delivers either an X (female) or Y (male) chromosome
• Spermatic cord suspends testis in scrotum via inguinal canal
• Cell differentiation stages

  • Totipotent status
  • Pluripotent status
  • Multipotent status
  • Terminally differentiated cells in the embryo/fetus
  • Terminally differentiated cells in the placenta
• Testicular descent abnormalities: Cryptorchidism
• Freemartin Formation in Cattle: Heifer is sterile (95%), Bull is normal & fertile
• Cryptorchidism: Failure of testis to descend
• Formation of the pituitary is similar between females and males fetuses and sex differentiation seems to occur postnatally only
• Freemartin Formation in Cattle: Heifer is exposed to testosterone & AMH from the bull fetus, resulting in specific reproductive tract abnormalities
• Sex Differentiation of the Hypothalamus affects the pattern of GnRH secretion and gonadotropins secretion by the pituitary
• Freemartin Formation in Cattle: Chorions of the two placentas fuse, fetuses share cotyledons and fetal blood supply
• Inguinal herniation: Intestine pass through inguinal canal
• Cryptorchidism: Unilateral - fertile with testosterone, Bilateral - sterile with testosterone
• Development and regression of the gubernaculum

  Depends on secretion of insulin like-3 (INSL3) and testosterone by Leydig cells
• Gross Function of the Male Reproductive Tract


  • Manufacture and delivery of sperm
  • Synthesis and secretion of androgens
• Ductus Deferens Function

  Sperm transport (part of the excurrent duct system)
• Blood Flow in the Spermatic Cord

  1. Pulse pressure is reduced considerably when the testicular artery enters in the spermatic cord

  2. The pampiniform plexus allows countercurrent exchange of heat and testosterone between arterial and venous blood
• Scrotum Functions

  Temperature sensor, temperature regulation, protection, support
• Cremaster Muscle Function

  Support of testes, aid of blood flow, enhance venous blood return to body, aid on heat exchange and temperature regulation of testes
• Spermatic Cord Functions

  1. Suspends testes in scrotum via inguinal canal

  2. Constitute a pathway for blood and lymph vessels, nerves, and ductus deferens

  3. Contributes for regulation of temperature and concentration of testosterone in the testes

  4. Temperature: Testes < Body

  5. [Testosterone]: Testes > Body
• Spermatic Cord Anatomy


  Testicular artery, testicular vein, pampiniform plexus, countercurrent heat exchanger, countercurrent transfer of testosterone
• Basic components of the male reproductive tract

  • Scrotum
  • Testes
  • Spermatic cord
  • Excurrent duct system
  • Accessory sex glands
  • Penis and associated muscles for protrusion, erection, and ejaculation
  • Prepuce
• Testes temperature is 4 to 6°C cooler than the body due to scrotal cooling and countercurrent heat exchange in the pampiniform plexus
• Scrotum functions as a temperature sensor, regulator, protector, and supporter
• Testes are the primary reproductive organs in males responsible for producing spermatozoa, hormones, proteins (especially testosterone), and tubular fluid for sperm transport
• Tunica dartos

  1. Capable of maintaining sustained contractions

  2. Changes scrotal location relative to body based on temperature

  3. Changes scrotal surface area based on contraction or relaxation
• Testicular capsule consists of visceral vaginal tunic, tunica albuginea, septal projections forming lobules, and contractions aiding in spermatozoa movement
• Scrotum has a two-lobed sac anatomy with four layers: skin, tunica dartos, scrotal fascia, and parietal vaginal tunic
• Common basic structure of testes

  • Testicular capsule
  • Parenchyma
  • Mediastinum
  • Rete tubules
• Scrotal fascia provides support and parietal vaginal tunic prevents adhesions for free-floating testes
• Layers of the scrotum

  • Skin
  • Tunica dartos
  • Scrotal fascia
  • Parietal vaginal tunic
• Internal abdominal oblique muscle

  1. Striated muscle - intermittent contractions

  2. Pumping action on the pampiniform plexus

  3. Enhance venous blood return to body

  4. Aids in heat exchange and temperature regulation of testes