Group 1 - 4/4 Birth to Puberty and CC - COMPLETE *** Flashcards
Testis Descent: When does it normally generally occur?
- For a bull
- For a stallion
- For a dog
between the middle and end of foetal development
4 months of gestation
late pregnancy or a few days after birth
up to 8 days after birth
Testis Descent: Describe the events occurring in the Transabdominal Phase of testicular descent 2
the testis is pushed towards the inguinal ring as the foetus grows
the testis makes contact with the inguinal ring
Testis Descent: State the names of the 2 phases of testicular descent
transabdominal phase
inguinal-scrotal phase
Testis Descent: Describe the events occurring in the first part of the Inguinal scrotal Phase 5
the gubernaculum has passed through the inguinal ring
it has become encased in peritoneal cells
it undergoes rapid expansion
this pulls the testis down through the inguinal canal
as the testis passes through the inguinal canal it becomes encased in peritoneal cells
Define Puberty
a developmental process in which endocrine and morphologic changes transform the animal into an individual capable of reproducing
Testis Descent: Describe the events occurring in the second half of the Inguinal Scrotal Phase 3
once the testis has passed through the inguinal canal the gubernaculum starts to regress
this pulls the testis down further into the scrotum
the gubernaculum forms a small knot at the base of the scrotum when fully regressed
Females: What 2 centres do they have in their hypothalamus?
- What does the presence of a surge centre enable?
a surge centre and a tonic centre
a pre-ovulatory surge in LH post puberty
State the requirement for puberty
secretion of GnRH at the appropriate frequency and quantity to stimulate gonadotrophin release by the anterior pituitary
Males: What centres do they have in their hypothalamus?
- How is this different to females?
- What does this mean?
a tonic centre
they do not have a surge centre
post puberty LH will be secreted in a relatively consistent episodic pattern
Which hormone is responsible for de-feminising the brain?
oestradiol
Describe what happens in the FEMALE foetal brain to enable the formation of a surge centre 4
the ovary produces oestradiol
oestradiol binds to a glycoprotein called alphaFP
this complex is too large to cross the blood brain barrier
this enables the surge centre to form
Describe what happens in the MALE foetal brain that prevents the formation of a surge centre 5
the foetal testis produces testosterone
this does not bind to anything
so is small enough to diffuse across the blood brain barrier
it is converted into oestradiol by an enzyme called aromatase
the oestradiol prevents the development of a surge centre
Pre-puberty: Describe what is happening hormonally in both males and females
low frequency and low amplitude irregular GnRH secretion
For females, what limited puberty onset?
- How does this prevent a surge in LH 4
GnRH levels are too low to stimulate FSH/LH release
the frequency of GNRH impulses are low
so LH and FSH are not released at high levels
oestradiol secreted by ovarian follicles is low
and is below the minimum threshold needed to stimulate GNRH neurones in the surge centre
In females, what happens at puberty that enables this first LH surge? 4
the inhibitory effect of low oestradiol on the tonic centre is reduced
leading to more GnRH production
and more LH and FSH production
which stimulates follicles to produce more eoestradiol
After Puberty: For Females, describe what happens hormonally after puberty 3
the amplitude and frequency of GnRH secretions from the tonic centre have increased
there is enough GnRH to stimulate the surge centre to create a pre-ovulatory surge in GnRH
which stimulates the anterior pituitary to release a surge of LH
Describe what happens at the onset of puberty for males 3
the inhibitory effect of low levels of oestradiol and testosterone on neurones in the tonic centre is reduced
so more GnRH is secreted
so more FSH and LH is secreted
Give 4 indices of male puberty onset
behavioural
age at first ejaculation
age when sperm appear in ejaculate
age when ejaculate contains a threshold number of sperm
How is body size linked to puberty in females? 2
GnRH neurones are sensitive to metabolic status
glucose, fatty acid and leptin sensitive neurones are thought to promote activity in kisspeptin neurones
How are kisspeptin neurones involved in female puberty onset?
kisspeptin neurones express oestrogen receptors
State external and social factors affecting female puberty 4
season in which animal is born
the photoperiod that animal experiences at puberty
the presence or absence of the opposite sex just prior to puberty
density of same sex groups
Give and explain some strategies that can be used to advance or delay puberty 3
nutrition - a high plane of nutrition results in early puberty while a low plane of nutrition results in delayed puberty
photoperiod
GnRH induction of early puberty gilts
State the average age of puberty in the following FEMALE animals
- dog
- cat
- sheep
- cow
- horse
1 year
8 months
7 months
11 months
18 months
State the average age for puberty in the following Male Animals -
-dog
- cat
- sheep
- cow
- horse
9 months
9 months
7 months
11 months
14 months
Hormone production in Testis:
- What receptor do Leydig cells have?
- What do they secrete?
- What receptor do Sertoli cells have?
- What do they secrete?
LH receptor
testosterone
FSH receptor
inhibin
