Puberty D

Question 1

Defining puberty attainment in males:

Answer 1

Defining puberty attainment in males:
Age at first sexual behaviour -mounting, erection, female interest (typically before ejaculation/spermatogenesis)
Age at first ejaculation - usually won’t contain sperm
Age when sperm appear in ejaculate - indicates active s’genesis
Age when ejaculate contains threshold sperm numbers - enough sperm to cause pregnancy in a female

Question 2

Describe how the surge center is defeminised.

Answer 2

During late prenatal development, T crosses the BBB in males and is converted to E2. The presence of E2 in the hypothalamus is what causes the defeminising of the hypothalamic surge center. E2 is the hormone that defeminises the surge center.

Question 3

Describe why puberty isn’t reached before birth despite T production in male fetuses.

Answer 3

Male puberty establishes a tonic (consistent pulsatile) secretion of GnRH in males and T is produced even as a fetus. GnRh must reach a threshold in order to drive puberty.

Prior to puberty, GnRH neuron are very sensitive to negative feedback = low GnRH secretion. During puberty, GnRh neuron sensitivity to negative feedback decreases and results in higher GnRh secretion and thus LH and FSH gonadotropins -> High T/DHT ->sperm production, 2 sex characteristics

Question 4

Answer 4

Question 5

Describe the triphasic HPG axis activity:

Answer 5

HPG activity increases 3 times during development:
Gonad differentiation (prenatal) - promotes testis dev
Immediately post birth - promotes sexual behaviour
During puberty - leads to 2 sex char and s’genesis

Question 6

Puberty timing across species:
Ram
Pig
Horse
Cat
Dog
Bull

Answer 6

Boar and Ram = 7months
Dog and tom = 9 months
Bull = 11 months
Stallion = 14 months

Question 6

Factors that affect puberty in males (4)

Answer 6

Season of birth- if staggered with breeding season - reach puberty sooner
Breed/genetics - dairy bulls reach faster than beef
Nutrition= too much- increased fat around scrotum and decreases sperm production
Chronic dx = delays puberty onset

Question 7

Describe the testis changes during puberty including the cells found in the testis:

Answer 7

Testis size and cellular composition change before and after puberty

Fetal
Gonocytes, immature sertoli cells, fetal leydig cells

Neonatal
gonocytes differentiate to spermatogonia, mitosis resumes

Pubertal
Meiosis begins - germ cell dev, sertoli cells mature, adult leydig cells

Question 8

Describe testicular descent:

Answer 8

During fetal development, the testes are in the abdomen and attached to the gubernaculum ligament. This ligament is attached to the scrotum and pulls the testes down into the inguinal canal as the lig grows. The gubernaculum then shrinks, pulling the testes into the scrotum.

Testicular descent happens well before puberty - during fetal dev - except for companion animals who undergo it post-natally ~2 months after.

Cryptorchid = retain abdominal testis/testes

Question 9

How are the vaginal tunics created during fetal development?

Answer 9

During the process of testicular descent (gubernaculum moves the testes from the abdomen, through the inguinal canal, and into the scrotum), the gubernaculum fuses with the peritoneum and this creates two layers with a cavity. Outer PVG and Inner VVT with a vaginal cavity in the middle. The vaginal cavity is continuous with the peritoneal cavity.