Abstract
The fusion of the cytoplasm and pronuclei of the male and female gametes along with the intermingling of the chromosomes of maternal and paternal origin to form a diploid zygote is known as fertilisation.
The fusion of male and female pronuclei is achieved through a series of events like gamete transportation, the interaction of male and female gametes through receptor-ligand interactions and zygotic genome activation. The egg cortical reaction facilitates the block of polyspermy. The zygote undergoes a series of mitotic cell divisions (cleavage) to form 2-cell, 4-cell, 8-cell, 16-cell, morula and blastocyst. Morula proceeds towards the uterus and gradually transforms into blastocyst after developing a cavity called blastocoele. The blastocyst then attaches to the endometrial surface through a process called implantation.The intrauterine period of embryonic and foetal development in viviparous mammals is called the gestation or pregnancy period. The physiological exchange between mother and foetus is mediated through a transient structure called the placenta. The structure and type of placenta are species specific. After completing intrauterine life, the foetuses and foetal membranes are expelled from the uterus to the external environment through a biological process called parturition. Mother regains its reproductive cycles after a considerable period from the parturition termed the postpartum interval. The uterus is transformed into a virgin state by uterine involution. All these processes are regulated by a synchronised endocrine orchestra together with biochemical and molecular mechanisms. Any disturbance in the process above may lead to fertility-related anomalies.
P. K. Das (X) ∙ J. Mukherjee ∙ D. Banerjee
Department of Veterinary Physiology, West Bengal University of
Animal & Fishery Sciences, Kolkata, West Bengal, India
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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P. K. Das et al. (eds.), Textbook of Veterinary Physiology, https://doi.org/10.1007/978-981-19-9410-4_23
Graphical Abstract
Description of the graphic: Fertilisation occurs through a series of biochemical and biophysical alterations in the spermatozoa, viz. capacitation (1) and hyperactivation (2) and the ovum (3). Fusing male and female gametes develops a single-cell zygote that undergoes cell divisions, differentiation and gastrulation (4). It consequently anchors with the endometrium through implantation (5). The maternal and foetal tissues coalesce from the placenta (6) to support the growth and development of the foetus(es). The foetus(es) expel out through a complex physiological phenomenon (7) called parturition
Keywords
Fertilisation ∙ Implantation and gestation ∙ Placenta ∙ Parturition ∙ Fertility-associated anomalies
Learning Objectives
• The mechanisms of transportation of sperm and ovum to the site of fertilisation.
• The species-specific biochemical and molecular
mechanisms occur in sperm and ovum before and after fertilisation.
• Process of implantation and formation of the placenta.
• Gestation and postpartum physiology.
• Role of different factors in controlling gestation.
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