Unit 1 - Parturition & Reproductive technologies Flashcards
What does Partuition require?
- Signal from foetus
- Cervical Softening
- Co-ordinated myometrial contractions
What occurs in stage one of Parturition? How long does this last?
(2-6 hours)
- regular uterine contractions
- cervical shortening and dilation occurs
What is a latent phase of cervical dilation? How is this different from active phase?
latent- slow dilation
active- rapid dilation
What occurs in stage two of Parturition? How long does this stage last?
(30-120 mins)
complete delivery of foetus, rupture of membranes and abdominal contractions
What occurs in stage three of Parturition? How long does this stage last?
(5-8 hours)
Delivery of placenta
What is hypertrophy in relation to Parturition?
oestrogen stimulates the muscle cell size to increase
How does the myometrium contract? (4 steps)
- spontaneous depolarizing pacemaker potential occurs
- when the magnitude of these potentials is higher than the critical threshold a burst of action potentials occur
- intracellular calcium increases in the extracellular fluid and endoplasmic reticulum
- the calcium binds to regulatory sites on actin & myosin, allowing expression of ATPase & causing contractions
What is Brachystasis?
Which cells undergo this process?
when contractions retract the lower uterine segment at the cervix to create a birth canal.
Myometrial cells
What is the junction between the upper and lower segments of a uterus called?
Retraction Ring
What is the role of hormones in Contractions?
Oxytocin lowers excitation threshold of muscle cells
Prostaglandins stimulate liberation of Calcium from intracellular stores
How is Oxytocin regulated?
What does it lead to?
- synthesised in the hypothalamus and transported axonally to the posterior pituitary.
- Released in response to the stimulation of the cervix by the foetus
Leads to..
Myometrial contraction (+ve feedback loop)
Prostaglandin release
What is the Fergusson reflex?
contraction initiated by pressure at the cervix or vaginal walls
What is Primary Uterine Inertia? What is is caused by?
failure to initiate contractions at start of parturition
caused by lack of oxytocin
What is secondary uterine inertia?
When is this most common?
uterine contractions at start, uterus then becomes fatigued and therefore contractions stop.
Common in large litters
Cervical softening involves what three things?
- reduction of collagen fibres
- increase in proteoglycan matrix fibres
- endocrine control