gestation period

period /pe·ri·od/ (pēr´e-od) an interval or division of time.

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ejection period  the second phase of ventricular systole, being the interval between the opening and closing of the semilunar valves, during which the blood is discharged into the aortic and pulmonary arteries; it is divided into a p. of rapid ejection followed by a p. of reduced ejection.

gestation period  the duration of pregnancy, in humans being about 266 days (38 weeks) from the time of fertilization until birth. In obstetrics, it is instead considered to begin on the first day of the woman's last normal menstrual period prior to fertilization, thus being about 280 days (40 weeks).

incubation period 

1. the interval of time required for development.

2. the interval between the receipt of infection and the onset of the consequent illness or the first symptoms of the illness.

3. the interval between the entrance into a vector of an infectious agent and the time at which the vector is capable of transmitting the infection.

latency period 

1. latent p.

2. see under stage.

latent period  a seemingly inactive period, as that between exposure to an infection and subsequent illness, or that between the instant of stimulation and the beginning of response.

menstrual period , monthly period the time of menstruation.

pacemaker refractory period  the period immediately following either pacemaker sensing or pacing, during which improper inhibition of the pacemaker by inappropriate signals is prevented by inactivation of pacemaker sensing.

refractory period  the period of depolarization and repolarization of the cell membrane after excitation; during the first portion (absolute refractory p.), the nerve or muscle fiber cannot respond to a second stimulus, whereas during the relative refractory period, it can respond only to a strong stimulus.

safe period  the period during the menstrual cycle when conception is considered least likely to occur; it is approximately the ten days after menstruation begins and the ten days preceding menstruation.

sphygmic period  ejection p.

Wenckebach period  the steadily lengthening P–R interval occurring in successive cardiac cycles in Wenckebach block.

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gestation period

Etymology: L, gestare, to bear; Gk, peri, near, hodos, way

the time span between conception and labor. In humans the period is approximately 38 weeks.

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gestation [jes-ta´shun]

the period of development of the young in viviparous animals, from the time of fertilization of the oocyte (ovum) to birth; see also pregnancy.

gestation period the duration of pregnancy; in the human female, the average length, calculated from the first day of the last normal menstrual period, is 280 days, or 6 lunar months. The normal limits of the human gestation period are from 37 weeks (259 days) to 42 weeks (293 days); days and weeks are counted as completed days and weeks. If one counts from the moment of conception, the length of time is 266 days (280−14 days).

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period [pēr´e-od]

an interval or division of time; the time for the regular recurrence of a phenomenon.

absolute refractory period the part of the refractory period from phase 0 to approximately −60 mV during phase 3; during this time it is impossible for the myocardium to respond with a propagated action potential, even with a strong stimulus. Called also effective refractory period.

blanking period a period of time during and after a pacemaker stimulus when the unstimulated chamber is insensitive to avoid sensing the electronic event in the stimulated chamber.

effective refractory period absolute refractory period.

ejection period the second phase of ventricular systole (0.21 to 0.30 sec), between the opening and closing of the semilunar valves, while the blood is discharged into the aorta and pulmonary artery. Called also sphygmic period.

gestation period see gestation period.

incubation period see incubation period.

isoelectric period the moment in muscular contraction when no deflection of the galvanometer is produced.

latency period

1. latent period.

2. latency stage.

latent period a seemingly inactive period, as that between exposure to an infection and the onset of illness (incubation period) or that between the instant of stimulation and the beginning of response (latency, def. 2).

refractory period the period of depolarization and repolarization of the cell membrane after excitation; during the first portion (absolute refractory period), the nerve or muscle fiber cannot respond to a second stimulus, whereas during the relative refractory period it can respond only to a strong stimulus.

relative refractory period the part of the refractory period from approximately −60 mV during phase 3 to the end of phase 3; during this time a depressed response to a strong stimulus is possible.

safe period the period during the menstrual cycle when conception is considered least likely to occur; it comprises approximately the ten days after menstruation begins and the ten days preceding menstruation. See the section on fertility awareness methods, under contraception.

sphygmic period ejection period.

supernormal period in electrocardiography, a period at the end of phase 3 of the action potential during which activation can be initiated with a milder stimulus than is required at maximal repolarization, because at this time the cell is excitable and closer to threshold than at maximal diastolic potential.

vulnerable period that time at the peak of the T wave during which serious arrhythmias are likely to result if a stimulus occurs.

Wenckebach's period a usually repetitive sequence seen in partial heart block, marked by progressive lengthening of the P–R interval; see also dropped beat.

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gestation

the period of development of the young in viviparous animals, from the time of fertilization of the ovum to birth. See also pregnancy.

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gestation period

the duration of pregnancy in the domestic animal species are: cow—273 to 292 days (Bos taurus), 271 to 310 days (Bos indicus); mare—333 to 346 days; ass—365 to 375 days; ewe—143 to 147 days (meat sheep), 147 to 155 days (merino); goat doe—146 to 155 days; sow—111 to 116 days; bitch—58 to 68 days; queen—61 to 70 days.

In laboratory and quasi-pet animals: guinea pig 59-72 days, gerbil 24-26 days, hamster 15.5-16 days, mouse 19-21 days, rat 21-23 days, rabbit 29-35 days.

perpetual gestation chart

a table based on the average gestation period of the particular species, e.g. 63 days for bitches, that plots the anticipated date of parturition against the breeding (conception) date. Designed to be independent of the year so it is valid indefinitely.

prolonged gestation

see prolonged gestation.