Parturition Stage of parturition Mechanism Of Initiation of



























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Parturition: Stage of parturition, Mechanism Of Initiation of Parturition, Hormonal Profile Associated with Parturition UNIT-1 & UNIT-2 Dr Ankesh Kumar

Parturition and their control

Parturition • It is the physiologic process by which the pregnant uterus delivers the fully grown fetus and placenta from the maternal organism on the completion of the normal pregnancy period.

Stages of parturition • 1 st- dilation of birth canal • 2 nd- expulsion of fetus • 3 rd- expulsion of membranes

Typical signs in approaching parturition Approaching calving- Approaching foaling- Sacro-sciatic ligaments relaxed Udder becomes distended (2 D) Sinking of the croup ligaments and muscles Raising of the tail head. (Ourny et al. , 1991) Oozing of colostrum from teats, called waxing ( Renton, 1984). Approaching whelping. There is drop of 1°C body temperature 24 hours before whelping. (Concannon et al. , 1989).

Table-1. Duration of three stages in different spp. species 1 st stages 2 nd stages 3 rd stages Cow/Buffalo 2 to 6 hrs 0. 5 to 1. 0 hrs 6 to 12 hrs Ewes 2 to 6 hrs 0. 5 to 2. 0 hrs 0. 5 to 8 hrs Mare 1 to 4 hrs 0. 2 to 0. 5 hrs 1. 0 hrs Sow 2 to 12 hrs 2. 5 to 3. 0 hrs 1 to 4 hrs Bitch/Cat 2 to 12 hrs 3 to 6 hrs -

Stages Table-2. Stages and their Characteristic feature 1 st- dilation of birth canal Slow regular uterine contraction, Cervical dilation Rapture of allantochorion Mare & Bitch - rotation of fetus 2 nd- expulsion of fetus Strong uterine and abdominal contraction Maternal recumbency Appear & rupturing of amnion Expulsion of fetus 3 rd- expulsion of membranes Uterine contraction decrease Loosening of chorionic villi Inversion of chorioallantois Expulsion of fetal membrane

Normal presentation , position and posture of fetus

Initiation of Parturition • The fetus control over the length of gestation whereas, the mother can influence the time of birth. (Noakes, 1999) • 1. 2. 3. The primary precursor for initiation of parturition Prostaglandin in the pig, Fetal cortisol in sheep Prostaglandins and fetal cortisol in the cow. (Jainudeen and Hafez, 2000) • In the mare oxytocin appears to be the primary parturition stimulation molecule. (Liggins and Thorburn, 1994)

Table – 3: Possible factors responsible for initiation of parturition Physical factors Biochemical factors Probable factors Effect Increase in fetal size Increase in uterine irritability Uterine distension Reversal of progesterone block Reflex to reduce size by fetal expulsion Fatty degeneration of placenta & presence of infarcts Leads to interference in fetal nutrition & separation process of fetus from uterus Increase in CO 2 tension in maternal blood due to increased fetal activity Increase uterine contractility Release of fetal antigens serotonin Release of collagenase and stoppage of blood supply to cotyledons

Neuroendocrine factors FETAL Increase in cortisol in adrenals Convert P 4 to E 2 & release of PG Increase in ACTH by pituitary Stimulate cortisol release Increase in corticotrophin releasing hormone (CRH) in hypothalamus Stimulate ACTH Increase in endogenous opiods Stimulate ACTH secretion MATERNAL Reversal of progesterone block Myometrial contractility Release of Relaxin Dilation of birth canal Dilation of pubic symphysis and sacro-sciatic ligaments Placental estrogens rise Release of PG in contractility Proinflamatory cytokines Softening of cervix Release of PG Stimulate smooth muscle

The mechanism of parturition • Successful parturition depends on two mechanical processes; 1. the ability of the uterus to contract 2. the capacity of the cervix to dilate • Parturition involves a lot of changes in the maternal system and the fetus

Maternal changes Myometrium: Infrequently Slow contractions which generate little hydrostatic pressure. (Nathanielsz, 1985) Cervix: Dilation of the cervix is induced by maternal steroids , prostaglandins relaxin and proinflamatory cytokines (Van Engelen et al. , 2009) The cervical softening (ripening) involves edema and softening because of enzymes. (Ourny et al. , 1991) Mammary gland A large rise in blood flow and changes in the overall volume and composition of secretion (Mellor, 1988)

Fetal changes 1. Fetal organs undergo maturational changes by the fetal cortisol (Liggins, 1994). 2. Secretion of surfactants (Silver, 1990). 3. Development of glycogen reserves in fetal liver 4. Increased output of T 3 and catecholamines (Shelley, 1961). (Klein et al. , 1978). 5. Closure of the ductus arteriosus. 6. Closure of the foramen ovale within a few hours of birth in foal.

Fetal hypothalamus ↓ Fetal Pituitary ↓ ACTH ↓ Fetal adrenal ↓ Adrenal corticosteroids ↓ Convert progesterone to estrogen ← Feto placental estrogens Proinflamatory cytokines Release of PGF 2α → Relaxin Cervical softening Oxytocin receptor Luteolysis pelvic reflex serum progesterone Myometrial contractions Myometrial excitability Posterior Pituitary Abdominal contraction Fetal Expulsion Oxytocin

Mechanism of steroidogenesis mother Corpus leutium cholesterol pregnenolone progesterone foetus 17 a- hydroxypregnenolone placenta estradiol Aromatising enzyme dihydroandrosterone cortisol

Hormones related to parturition • Estrogen 1. ↑ the synthesis of contraction associated proteins in myometrial cells, 2. ↑ electrical coupling by activation of connexin-43 3. ↑ the expression of PG & oxytocin receptors. (Jenkin and Young, 2004). 4. ↑ the release of prostaglandin. (Thorburn et al. , 1977). • Relaxin: Causes widening of pelvis by relaxing sacro-sciatic ligament & the pubic symphysis of the pelvic girdles. (Sherwood, 1982) • Prostaglandins Favors increased contractions during labor in all species (Thorburn et al. , 1977). • Oxytocin: Causes powerful contractions of myometrium (Silver, 1990). Changes in the estrogen; progesterone ratio ↑ PG production to elicit oxytocin receptor formation. (Soloff et al. , 1985) • Glucocorticoides cortisol enhances amnionic cyclooxygenase and inhibits chorionic prostaglandin dehydrogenase activity ( Jenkin & young , 2004)

Artificial Induction of Labor (Induced Parturition) • In domestic animals may be required for some physiologic and pathologic reasons. • Any parturition induction regime must fulfill some prerequisites (i) The neonate must be viable and the dam must lactate normally. (ii) The method must be reliable and delivery must be predictable (iii) It must be safe with no adverse effects on either the dam or her young.

Compound used for induced parturition Name of the compound Exogenous glucocorticoid Name of the species cattle buffalo sheep goat mare Sow Limited efficiency Prostaglandins Prostaglandin F analogues (cloprostenol-in Oxytocin Dog/cat Limited efficienc y Exogenous estrogens 3βhydroxysteroid dehydrogenase inhibitor / Epostane camel Less satisfactor y


Summary • For normal parturition PPP Should be proper • Fetus length of gestation • Mother Influence the time of birth • The initial mechanism for the timing of birth is encoded in the fetal genome • Initiation of parturition done by fetus itself in all spp. • No. of hormones work together in a harmonic manner in the process of parturition. • For induced the parturition by application of various exogenous compound which are species specific.






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