Page 114 - 86 human physiology part-2

Pregnancy and Birth

Uterus is the size of a hen's egg; Embryo is curved, head is large, limb buds are
5 weeks
mother may need to urinate frequently showing division, nose, ears and eyes are noticeable
Fingers and toes are present and skeleton is
6 weeks Uterus is the size of an orange
cartilaginous
Fetus begins to look human; limbs are developing
Uterus can be felt above the pubic
8 weeks and major organs forming; facial features are
bone
becoming refined
Fetal Development
Head grows faster than the rest of the body; facial
12 Uterus is the size of a grapefruit features are apparent, but there is no layer of fat yet
weeks and the skin is translucent; gender can be
distinguished via ultrasound; fingernails appear
16 Fetal movement can be felt Fine hair (lanugo) grows over the body; fetus
weeks resembles a tiny human being; skeleton is visible
20-22 Uterus reaches up to the level of Vernix caseosa, the protective fatty coating, begins to
weeks umbilicus and pregnancy is obvious be deposited; heartbeat can be heard
Doctor can tell where baby's head, Fully formed but still thin; much larger and very
24 back and limbs are; breasts have active, all major organs are working, the lungs and
weeks enlarged and nipples and areola are digestive system need more time to develop; body is
darker, colostrum is produced covered in fine hair called lanugo
Most babies are in a head down position in the
32 Uterus reaches halfway between womb; head is more in proportion to the body; eyes
weeks umbilicus and rib cage are open; babies born at this stage have a good chance
of living
Weight gain is averaging about a
pound a week; standing ans walking
36
weeks are becoming very difficult because Body hair begins to disappear, fat is being deposited
the center of gravity is thrown
forward
Uterus is up to the rib cage, causing Not much room to move in the womb; fully mature,
40
weeks shortness of breath and heartburn; baby moves less, and the surrounding fluid reduces
sleeping is very difficult and the womb expands its limits

Embryonic Development at Specific Stages

First trimester

An embryo this tiny shows very distinct anatomic features, including tail, limb buds, heart (which
actually protrudes from the chest), eye cups, cornea/lens, brain, and prominent segmentation into
somites. The gestational sac is surrounded by a myriad of chorionic villi resembling elongate party
balloons. This embryo is about five weeks old (or seven weeks in the biologically misleading but
eminently practical dating system used in obstetrics).

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