Human Fetus at 21 Weeks in the Womb (Caucasian Skin)

Description

At roughly 21 weeks of gestation the fetus is shown suspended in amniotic fluid within a translucent amniotic sac, flexed in the characteristic fetal attitude with the spine curved, hips and knees drawn up and both upper limbs raised toward the face. Surface features are well differentiated: a large domed cranium with a still-prominent forehead, closed fused eyelids, formed external ears, an open mouth, and slender limbs ending in separated fingers and toes. The umbilical cord leaves the anterior abdominal wall at the umbilicus and spirals toward the placental disc seen at right, where the coiled umbilical artery and vein are visible through the cord surface before branching into the chorionic vessels. The maternal side of the field is formed by the vascular endometrium and myometrium of the uterine wall, framing the gestational compartment. The second half of the mid-trimester is the interval in which detailed anatomical ultrasound is normally performed, making this stage the reference point for biometry such as biparietal diameter, head and abdominal circumference and femur length, and for survey of the fetal face, limbs and abdominal wall insertion of the cord. The image also illustrates the anatomy underlying cord-related assessment, including vessel number, cord coiling and placental site, and the amniotic fluid volume that supports lung development and limb movement. Fetal position, placental implantation and sac integrity are the same relationships that guide amniocentesis planning and counselling about periviability. Suited to obstetric and midwifery teaching, embryology and developmental anatomy lectures, prenatal-care patient education, pregnancy-tracking applications and antenatal clinic displays, and as a stage figure in atlases or textbook series charting week-by-week gestation. Editorial and publishing users can pair it with the earlier weeks in the same set for continuous developmental sequences. Anatomical accuracy verified by SciePro's Medical Advisory Board.