Oestrous cycle Flashcards
Lactation
Production of milk by mammary glands
Position of mammary glands
Lie externally on the ventral wall of the abdomen and thorax on either side of midline
How many pairs of mammary glands does a) queen b) bitch have
A) 4 pairs
B) 5 pairs
What are mammary glands made of
Consists of glandular tissue embedded in connective tissue and lined by secretory epithelium.
Milk drains through network of sinuses that eventually narrow to form tear canals.
Opening of a teat
Teat orifice
3 hormones influencing production of milk
- glands enlarge in response to progesterone secreted by corpus lute under in ovary.occurs during pregnancy and may be seen during non- preg lutes phase of the bitch
- milk produced by gland in response to prolactin secreted by anterior pituitary gland
- milk released by glands in response to sucking by neonate only occur if hormone oxytocin secreted by posterior pituitary gland is circulating in blood. Oxytocin is released a few hours before parturition.
Average composition of milk
Water -70-90% Fat -0-30% Protein -1-15% Carbohydrates -3-7% Minerals -0.5-1% (calcium, phosphate, sodium, magnesium, chloride) deficient in iron and copper Vitamins -A,B2,B5,E,K Low in -Vit C and Vit D
How long do maternal antibodies protect the neonate
10-12 weeks, after this is capable of producing antibodies and being vaccinated
Oestrous cycle
Rhythmic phenomenon seen in all post-pubertal non-preg female mammals involving regular but limited periods of sexual receptivity known as oestrus
Functions of oestrous cycle:
- produce ova from the ovary ready to be fertilised by spermatozoa from male
- prepare repro tract of female to receive fertilised ova
- initiate behavioural patterns in female that indicate to male she is ready to mate
- stimulate the female to stand still and allow mating
Events related to oestrous cycle that occur
1) behavioural- female ‘advertises ‘ she is receptive to male . Patterns of behaviour differ in the bitch and queen
2) ovary - development of follicles, realise from ova and the development of ruptured follicles into corpora lutea.
3) uterine horn and uterine body prepare to receive the fertilised ova
4) endocrine system - follicle stimulating hormone (FSH) are secreted by anterior pituitary gland. Oestrogen and progesterone are secreted from ovary.
Order of oestrous cycle
Pro-oestrous Oestrous Metoestrus Dioestrus Interoestrus Anoestrus
Pro-oestrous
Prep for oestrous during which time follicles are developing in the ovary. Repro tract is dominated by the hormone oestrogen
Oestrus
Period during which female will allow mating
Metoestrus
Initial development of the corpora lutea
Dioestrus
Mature phase of corpora lutea
Interoestrus
In the queen that has not ovulated this is the phase between two episodes of oestrous
Anoestrus
Period between oestrous cycle during which there is very little activity in ovary
During pro-oestrus which hormone dominates repro tract
Oestrogen
During metoestrus and dioestrus which hormone dominated repro tract
Progesterone
What phase is pro-oestrous and oestrous in
Follicular phase
What phase is metoestrus and dioestrus in
Luteal phase
Monestrous
During each period of ovarian activity there is only one period of oestrous
What type of ovulator is the bitch
Spontaneous ovulator
What does spontaneous ovulator mean
Ovulates during her cycle regardless to weather or not she’s mated
When does bitch reach sexual maturity
6-12 months
How is puberty marked
Onset of first oestrus cycle
Bitches phases of oestrous
Pro-oestrus
Oestrus
Metoestrus/ dioestrus
Anoestrus
Pro-oestrus in the bitch
- lasts approx 9 days
-starts with vulva bleeding - ends with mating
- repro tract dominated by oestrogen
-vulva swollen, increased urination, flirty behaviour
-
Oestrous in the bitch
- approx lasts 9 days ( range if 1-20days)
- vulva continue to swell, becomes distinctly softened
- flirty excitable behaviour
- will allow mating
Ovulation
The release of the ova from the ovaries
When does ovulation occur
Approx 12 days after onset of pro-oestrous following rapid surge of luteinsing hormone.
Metoestrus in the bitch
- lasts approx 70 days
- luteal phase
- domainted by progesterone
- discharge drys up,swollen vulva returns to normal size, bitch returns to normal
- corpus luteal formed in ovary
- from day 25 prolactin produced
- enlarged mammary glands, no discharge, vulva normal size, normal behaviour
Prolactin is luteotropic meaning
Supports progesterone production from corpus luteum
Anoestrus in bitch
-lasts 3-9 months
- period of inactivity in ovary
- behaviour and external apprentice bicth is normal
- towards the end follicles begin to develop in ovary
When levels of oestrogen have increased enough they will initiate behavioural signs of pro-estrius
What type of oestrous does the queen have
Seasonally polyoestrous
What does seasonally polyoestrous mean
Several oestrous cycles during breeding season
When is cat breeding season
January to September
When is the queen in anoestrus
Winter months
What is thought to be onset of cat breeding season
Increase hours of daylight and rise in temp ( early srping)
What is meant by induced ovulator
The ova will be released from the follicles in the ovaries only in response to the stimulus of mating
What causes the release of repro hormones in the queen
The male withdraws his permission and causes the queen to loud howl and therefore invites nerve impulses stimulating hormone release
When does the queen become sexually mature
6 months of age
Phases of the queen oestrus cycle
Oestrus
Interoestrus
Dioestrus
Anoestrus
Oestrus in the queen
- 4 to 7 days
- allow mating
- increase in affectionate behaviour, lordosis, calling
Interoestrus in the queen
- 14 days
- behaviour is normal and follicle begin to develop and oestrus starts again
What happens if mating doesn’t occur in interoestrus in queen
Ovulation won’t occur as the formation of the corpus luteum or progesterone secretion. Ovary inactive
Dioestrus in the queen
- 40 days
- if mated the corpora luteum form and secrete progesterone -
- if not preg the corpora lutea have a secretory lifespan of approximately 40 days
- mammary enlargement
Anoestrus in the queen
- 4 months long
- ovary remains inactive during winter months
- follicles start to develop in late December to response of increasing hours of daylight and gradual inc enviro temps.
What does puberty do to primordial follicles
Develop them into Graafian follicles
Where do primordial follicles come from
Animal is born with all germ cokes in her ovaries she will ever use in lifetime, act as reservoir from which the primordial follicles will develop
Multiparous
Litter bearing
When does development of follicles begin
End of anoestrus and contained through to pro-oestrus
3 parts of developing follicles
1) outer double layer of follicular cells
2) cavity containing follicular fluid
3) ovum (nucleus consign haploid numbers of choromsones and result in meiosis)
Hormone secreted by Graafian follicles
Oestrogen
When does the follicle reach full size and rupture and what does this cause
End of pro-oestrus and begging of oestrus and relies of the ovum starting ovulation
What stages Does the ovary go through after ovulation
1) little bleeding into the ruptured follicle, produces a transient stage known as the corpus haemorrhagicum ( bloody body)
2) blood resorted and the follicular tissue organises to form the corpus luteum ( yellow body)
What hormone does corpus luteum secretes
Progesterone
What is corpus luteum referred to when remains in ovary
Corpus luteum of cycle or corpus luteum of pregnancy
What happens to corpus luteum of cycle during pregnancy in a dog
Remains in ovary for long as pregnancy meaning levels of progesterone remain high and some bitches develop symptoms of false preg/ pseudocyesis.
What stage is entered at end of luteal phase
Anoestrus
What happens to CL of preg of mated
Develops and fertilisation occurs.
Remains for almost all of gestation period
What happens to corpus luteum in the queen
The CL of final cycle of the season regressed there is a variable period of variance inactivity known as anoestrus.
Stimulants of next breeding cycle
- day length
- enviro temp
- presence of same species
- presence of male
Changes to uterus during oestrus
The walls of the uterus become thickened and more glandular and may produced a mucous discharge
What hormone causes change to uterus in oestrus cycle
Influence of Oestrogen secretedby the developing follicles
Progesterone furthers this effect
Changes to Mammary glands
Progesterone may cause slight enlargement of mammary glands
Effect on the vagina
Epithelial lining of vagina changes under influence of different hormones
Changes seen to vagina anoestrus
Anoestrus - lining fairly dry, epithelial cells non-cornfied, few leukocytes
Changes seen to vagina pro-oestrus
Pro-oestrus- many red blood cells present, epithelial cells cornified and non-cornified, few leukocytes, abundant debris
Changes to vagina oestrus
Oestrus - vagina very mosi, no. Of red blood cells reduced, straw coloured discharge
Changes to vag at end of oestrus
Leukocytes reappear, very few red blood cells
Changes to vag at early luteal phase
No. Of leukocytes inc., decrease in cornfield cells and increase in non-cornified
When is mating recommended
Around time the red blood cells and leukocytes decrease and cornfield cells inc.
Servers hormones involved in a complex of interactions during oestrus
Gonadotropin releasing hormone (GnRH) follicle stimulating hormone ( FSH) Lutiensing hormone (LH) Oestrogen Progesterone
Gonadotropin releasing hormone (GnRH)
Produced by hypothalamus at base of forebrain in response to external factors
Stimulates the release of gondotrophins
Follicle stimulating hormone (FSH)
A gondrotrophin secreted by the anterior pituitary gland at base of forebrain.
Acts on developing follicles of ovary
Lutenising hormone (LH)
Gonadotropin secreted by anterior pituitary gland
Acts on mature follicles in ovary
Oestrogen
Steroid hormone, secreted by developing follicles in ovary
Progesterone
Steroid hormone secreted by mature follicles and corpus lutea in ovary
What starts oestrous cycle
The hypothalamus secreted gonadotropin releasing hormone (GrRH)
How and where is GnRH carried to
In the blood to the anterior pituitary gland lying ventral to the hypothalamus at the base of the forebrain
What does the anterior pituitary gland secrete
FSH which stimulates the primordial follicle in the ovary and they develop into ripe Graafian follicles
Follicular tissue around each ovum begins to secrete oestrogen
Oestrogen secretions inhibits…
Further production of FSH And stimulates production of LH from anterior pituitary gland
What does LH act on
Graafian follicles. Some more mature ones lutenise and secrete hormone progesterone. The progesterone is produced in quite high amounts before ovulation in the bitch but not other species.
Eventually Graafian ruptures and ovum released
When do progesterone levels in the bitch peak
Day 20 of cycle and remain high till day 60 regardless of preg or not
What can cause pseudopreg
High Levels of progesterone combined with prolactin
Progesterone produced what effects
Walls of iputerus thickened and become more glandular to prepare for pregs
Mammary glands enlarged
Secretion of progesterone on GRH
Inhabits production of GRH from hypothalamus and prevents development of more follicles and helps to maintain prey state
