Early embryonic development, with stages including implantation of the blastocyst and development of the supplying blood vasculature to the embryo. Day 7: arrival in the uterus and implantation. Day 7+: beginning trophoblast. Day 12: microvilli stage. Days 13 to 19: yolk sac stage and end of presomite stage. Days 23 to 28, embryo with head and tail apparent.

Medical illustration of a fetus in the womb.

Medical illustration of a fetus in the womb.

Medical illustration of the foot and ankle showing the network of tendons and ligaments.

Medical illustration of an ovum in the fallopian tube.

Medical illustration of the female reproductive system and the processes of ovulation, fertilization, implantation of the embryo in the uterine wall, and further fetal growth.

Medical illustration of the pituitary gland. The pituitary gland is part of the endocrine system and is attached to the infundibulum of the brain. It regulates many important and basic body functions via hormonal secretions.

Medical illustration of the human brain. The different lobes are shown in different colors (yellow = frontal lobe, green = parietal lobe, brownish-orange = temporal lobe, gray = occipital lobe).

Medical illustration of testicular descent. Normal testicular descent involves the movement of the testicles from the abdominal cavity to the scrotum, and usually occurs before birth.

Medical illustration of the human eyeball, shown with a partial cutaway section in order to view the interior of the eye.

Medical illustration of the human eyeball, along with the optic nerve and supporting musculature, as viewed from the side.

Medical illustration of the lens of the eye, shown with a partial cutaway section in order to view the interior.

Medical illustration of the lens of the eye, showing the regions of formation of nuclear cataracts in comparison to cortical cataracts. Nuclear cataracts form in the center of the lens, while cortical cataracts gradually extend from the outside of the lens to the center.

Medical illustration of the layers of retinal cells in the eye.

Medical illustration of a transparent glass woman, highlighting the organs of the digestive system. The palate, pharynx, esophagus, stomach, small intestine, large intestine, and rectum are shown.

Transparent glass man and woman, showing the organs involved in sexual attraction, especially those that secrete sex hormones. The testes in the male and the ovaries in the female are highlighted, and in both the male and the female, the brain is shown with the pituitary gland and the hypothalamus highlighted.

Medical illustration of a transparent glass man, highlighting the organs of the male urinary system. The kidneys, ureters, bladder, and urethra are shown.

Medical illustration of a transparent glass man, highlighting the organs of the male urinary system. The kidneys, ureters, bladder, and urethra are shown.

Medical illustration of a woman's body showing the lymphatic system. (c) Duval

Medical illustration of a woman's body showing the reproductive system. (c) Duval