Repro 3 Flashcards
List the vet definitions of puberty and what this means for male and female
Puberty = the acquisition of reproductive competence
MALE:
1. Age when ejaculate contains sufficient spermatozoa to fertilise
FEMALE:
1. Age where female can support a pregnancy without deleterious effects (successful preg and own growth not inhibited)
How does lactation affect cycling?
- L inhibits GnRH pulse generator
- Plasma FSH sufficient to allow follicle development BUT GnRH pulsatility is too low to allow ovulation
- Suckling frequency increases inhibition
Is a dairy or beef more likely to come into oestrus sooner and why?
- Dairy
2. Milked on average 2X a day vs beef milked at higher frequency
How does seasonality affect cycling?
- seasonality is controlled by GnRH pulse generator
- in spring = decreased melatonin which has a different affect on different species: sheep = suppresses pulsitility. Horses = increases
Normal physiological reasons when GnRH pulsatility is suppressed and ovarian cycles stop:
- Lactation
- Photoperiod - (day length) seasonality
- Pregnancy
once animal starts = continues forever
Pathological inputs (physical or mental) to the GnRH pulse generator in animal. Especially what type of animal and why?
Type = newly calved dairy heifer as is a Metabolic athlete and:
- Stress, being bullied (introduced to herd),
- Weight loss (lactating),
- Lactating,
- Growing
Why can’t you throw hormones at a newly calved dairy heifer that isn’t coming into oestrus?
- not respond to drugs
2. cause of hypothalamus not firing
List the physiological and pathological reasons for decrease in GnRH pulse frequency
Physiological: 1. Lactation 2. Pregnancy 3. Day length (photoperiod) Pathological reasons 1. Starvation 2. Stress 3. Disease
Why can’t you throw hormones at a newly calved dairy heifer that isn’t coming into oestrus? What do you have to do instead?
- not respond to drugs
- cause of hypothalamus not firing
- have to sort the underlying problem: think “why not coming into oestrus?” bullied = stress? starving? disease?
Outline structure of mammary gland
- it is a modified sweat gland. Ectoderm epithelial cells
2. Species specific as to how it develops
How does mammary gland develop
- Modified sweat gland
- starts as mammary ridge: ectoderm cells
- starts to bud: species specific = diff number of glands, location and structure of teat
- Arise from lateral lines on ventral abdomen
- diff number of glands
Outline structure of mammary gland
- Highly organised and vascularised structure external to body cavity
- parenchyma = secretary tissue
- Milk duct connects to many alveoli which grow into lobules at lactation
- alveoli = like bunch of grapes
How does mammary gland develop
- Modified sweat gland
- starts as mammary ridge: ectoderm cells
- starts to bud: species specific = diff number of glands, location and structure of teat
- Arise from lateral lines on ventral abdomen
- Primary buds, then secondary.
- Buds then canalised (tube in them)
- most development after puberty
Comparative microanatomy of diff species
- Ruminants = 1 canal
- Horse and pig = 2-3 ducts to canal
- dogs and cats = multiple canals
What specialises the mammary epithelial cells of alveoli?
- Highly metabolically active cells on a basement membrane surrounded by collagenous extracellular matrix
- loads of rough ER, golgi, smooth ER
- milk synthesides across apical surface
What is the major composition of milk
- protein, fat, lactose
2. differs between sepcies
What is the ion composition of milk
Na+, K+, Cl-, Ca2+
Colostrum
- prepartum milk secretion
- Immunoglobulins produced by plasma cells in gland = passive immunity
3, short window for absorption - high in fats, proteins, Vit A, low in lactose
What is lactogenesis and galactopoesis
- L = onset of milk secretion
2. GP = continuation of lactation
What are the 2 stages of lactogenesis?
Stage 1: acquisition of secretory capability PRE PARTURITION
Stage 2: onset of copious secretion at/ around parturition
What ensures the synchrony between stage 2 and partuition?
HORMONES
- inc cortisol (stress) (adrenal gland)
- inc prolactin (anterior pituitary)
- Inc oestrogen
- progesterone plummits = signal of end of gestation
What happens when progesterone decreases at teh end of pregnancy?
- P affects receptors on milk producing cells to prolactin
- Prolactin binds
- allows synthesis of milk
How is milk secretion maintained and what is its name?
- Galactopoesis
- requires hormones:
a) prolactin = maintain alveolar cell metabolism
b) oxytocin = remove milk
c) GH, insulin, thyroid and cortisol all required indirectly
How is milk secretion maintained and what is its name?
Galactopoesis
- requires hormones:
a) prolactin = maintain alveolar cell metabolism
b) oxytocin = remove milk from mammory gland + stimulate myoepithelial cells = muscle cells that sit around alveoli
c) GH, insulin, thyroid and cortisol all required indirectly - REQUIRED removal of milk: feedback inhibitor builds up if not removed
