Physical Adaption in pregnancy

The changes during the pregnancy may cause some problem for mother and child.Physical adaption to pregnancy is dramatic and often underestimated.The timing and intensity of the changes very between systems but all are designed to enable the woman to nurture the fetus and prepare her body for labor and lactation.Recent advances an reproductive technology gave led to changed perceptions of the effects of specific hormones and less certainity relating role of conventional endocrine glands.Genetic factors are nw considered likely to underpin most of the physiological changes of pregnancy.The focus on genetic influences will doubtless intensify in subsequent editions of this book.
After conception,the uterus develops to provide a nutritive and environment in which the fetus will develop and grow.After embedding of the blastocyst their is thickening and increased vascularity of the lining of the uterus or decidua.Decidualisation,influenced by progestones and oestradiol,is most marked in the fundus and upper body of the uterus.The decidua is now believed to maintain functional quiesance of the uterus during pregnancy,spontaneous labour is thought to result from the activation of the decidua with resultant prostaglandin release following withdrawal of placenta hormones.The decidua and trophoblast also produce relaxin,which appears to promote myometrial relaxation and may have a role to play in cervical ripening and rupture of fetal membranes.
In early pregnancy uterine growth is due to hyperplasia and hypertropy of moyometrical cells under the influences.As gestination increases,hperplasia is less important and hypertrophy accounts for most of the growth of the uterus.In the later half of the pregnancy the uterus expands mechanically owing to distension of muscle cells by the growing fetus and placenta.The diemension of the uterus vary considerably,however depending on the age and parity of the woman.During the first few months of pregnancy the uterine walls becomes substantially thicker and less firm,growing from 1cm to 2.5cm by 4 months.Then as gestation advances they gradually becomes thinner.By term the uterus has become a muscular sac with soft,readily indentable walls of 0.5-1 cm or less in thickness,making palpation of the fetus relatively easy.Hyperplasia and hypertrophy of the mymoetrical cells lead to the three layers of myometrium becoming more clearly defined.The outer longitudinal layer of muscular fibres is thin.It consists of a network of bundles of smooth muscles.These pass longitudinal from the front of the isthmus anteriorly over the fundus and into the vault of the vagina posteriorly,and extend into the round and transverse ligaments.
The thicker middle layer comprises interlocked spiral myometrical fibers that are perforated in all directions by blood vessels.Each cell in this layer has a double curve so that the interlacing of any two gives the approximate form of a figure of eight.Due to this arrangement,contraction of these cells after delivery causes constrictions of thet blood vessels.The inner circular layer is arranged concentrically around the longitudinal axis of the uterus and bundle formation id diffuse.It forms sphincters around the openings of the uterine tubes and around the internal cervical os.The mymometrium is both contracile and elastic to accommodate the growing of fetus and allow involution following the birth.Thin sheets of connective tissues composed of collagen,elastic fibres,fibroblasts and mast cells seperate the inter-connecting bundles of 10-15 partially overlapping smooth muscla cells.The collagenous connective tissues supports the muscle fibres and provides a transmission network for the tension developed by contraction of the smooth muscle elements.
The perimetrium is a thin layer of peritoneum that protects the uterus.It provides a relatively inelastic base upon which thw mymometrium develops tension to increase intrauterine pressure.It does not totally cover the uterus,being deflected over the bladder anteroirly to form the uterovesical pouch of Douglas.The double folds of perimtrium,hanging from the uterine tubes and extending to the lateral walls of the pelvis,become longer and wider with increasing tension exerted on them as the uterus enlarges and rises out of the pelvis.The anteroir and posteroir folds open out so that they are no longer in apposition and can therfore accomadate the greatly enlarged uterune and ovarian arteries and veins.The round ligaments provide some anteroir support for the enlarging uterus and undergoing considerably hypertropny and stretching during pregnancy,which mau cause discomfort or strain.
As a result of the increased cardic output,the uterine blood flow progressively increases almost tenfold,from approximately 50 ml/min at 10 weeks's gestation and reaching a maximum of 450-700 ml/min at term.Eighty per cent per fuses the placenta and 20% per fuses the myometrium.The uterine arteries course along the lateral walls of the uterine giving of off 9-14 branches,each of which penetrates the outer third of the myometrium.At this the levels uterine arteries anastomes with the ovariam arteries.

Physical Adaption in pregnancy

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