Puberty Defining - Anatomy & Physiology

()Map REPRODUCTIVE SYSTEM (Map) PUBERTY

Introduction

Generally, puberty can be defined in both sexes as the ability to accomplish reproduction. The fundamental requirement for the onset of puberty is the secretion of GnRH at the appropriate frequency and quantity to stimulate gonatotrophin release by the anterior pituitary gland. Gonadotrophins promote:

• Gametogenesis
• Steroidogenesis
• Development of reproductive organs

The degree of function of neurons in the hypothalamus that secrete GnRH increases as puberty begins. The function of these neurons may be influenced by:

• Plane of nutrition
• Exposure to certain environmental or social cues
• Genetics

Male

Age when Behavioural Traits are Expressed

• Generally acquire reproductive behavioural traits such as mounting and erection a long time before they acquire the ability to ejaculate and produce spermatozoa.
• Behavioural traits are easy to determine, as mouting behaviour and erection can be easily observed.

Age at First Ejaculation

• Ejaculation is a complex process,requiring coordinated development of nerves, specific muscles and secretion of seminal fluids from the accessory sex glands.
• When development of all of these components occurs, ejaculation can take place.
• Generally the ability to ejaculate preceeds the ability to produce sufficient spermatozoa to achieve fertilization.

Age when Spermatozoa First Appear in the Ejaculate

• Males acquire the ability to produce seminal fluid and ejaculate before spermatozoa are available to be ejaculated.
• To determine when spermatozoa first appear, the ejaculate must be collected at least once per week.
  • Easy to collect using an artificial vagina from the the boar, bull, dog, ram or stallion.
• After behavioural characteristics have developed and the male is willing to mount a receptive female/surrogate, frequent seminal collection is possible.
  • Enables determination of the age at which spermatozoa first appear in the ejaculate.

Age when Spermatozoa First Appear in the Urine

• Most spermatozoa produced are lost in the urine during periods of sexual abstinence.
• The presence of sperm in the urine indicates that spermatogenesis is occuring.
• Frequent urine collection is difficult in large domestic species and requires special equipment, so this method of determining pubertal onset has limitations.