Illustration showing the nerves of the female pelvis.

Illustration of birth complications, showing intrauterine (uterine) infection during pregnancy, cutaway view. The infection is depicted in green.

Illustration of an embryo at four weeks in utero, cutaway view of the uterus and chorion to show the amniotic sac. The embryo measures 4.0 mm CR (crown-rump) length. The upper limb buds are flipper-like and the lower limb buds have begun to form. Also shown are the lens placodes (primitive eyes), heart prominence, and four pairs of gill arches. (1 of 9)

Illustration of a fetus at nine weeks in utero, cutaway view of the uterus and chorion to show the amniotic sac and fetal development. The lumbar spine, pelvic bones, and pubic symphysis are also shown within the figure. (2 of 9)

Illustration of a fetus at twelve weeks (third month) in utero, cutaway view. The lumbar spine, pelvic bones, and pubic symphysis are also shown within the figure. (3 of 9)

Illustration of a fetus at sixteen weeks (forth month) in utero, cutaway view. The lumbar spine, pelvic bones, and pubic symphysis are also shown within the figure. (4 of 9)

Illustration of a fetus at twenty weeks (fifth month) in utero, cutaway view. At this stage the mother is aware of fetal movement. The legs reach their final relative proportions and the overall rapid growth rate slows down. Myelination of the spinal cord has begun. The eyelids and eyebrows are well developed. The CR (crown-rump) length is 185 mm. (5 of 9)

Illustration of a fetus at twenty-four weeks (sixth month) in utero, cutaway view. The lumbar spine, pelvic bones, and pubic symphysis are also shown within the figure. (6 of 9)

Illustration of a fetus at twenty-eight weeks (seventh month) in utero, cutaway view. The lumbar spine, pelvic bones, and pubic symphysis are also shown within the figure. (7 of 9)

Illustration of a fetus at full term, 36-38 weeks (ninth month) in utero, cutaway view. The lumbar spine, pelvic bones, and pubic symphysis are also shown within the figure. (9 of 9)

Illustration of the normal human jaw, showing the mandible, maxilla, and occlusion (alignment of the teeth); anterior view (top) and lateral view (bottom).

Illustration of the abdominal organs of the digestive system, anterior cutaway view. Labeled structures include the liver, stomach, transverse colon, jejunum, ileum, appendix, ascending colon, ileocecal valve, cecum, descending colon, and rectum.

Illustration of the stages of birth presentation for a full-term fetus. The fetus is shown in an occiput posterior (head down, facing outward) presentation at the +2 station. Labeled anatomical structures include the uterus, placenta, pubic symphysis and sacrum. Also labeled are the various stages of presentation (-3, -2, -1, 0, +1, +2, +3).

Illustration of the digestive organs within the female abdomen, including the liver, stomach, cystic duct, gallbladder, pancreas, pancreatic duct, sphincter of Oddi, and small intestine.

Illustration showing the anatomy of a vertebral (intervertebral) disc in the lumbar spine.

Illustration showing the anatomy of the hand from a palmar view, including the musculature, bones, nerves, and arteries.

Illustration showing the bones of the hand and forearm.

Illustration of the male pelvic organs, midsagittal section, showing the penis, testicle, urethra, pubis, urinary bladder, prostate gland, rectum, and anus.

Illustration showing anatomy of the larynx, with the upper respiratory tract and throat, sagittal view.

Illustration of the thoracic (chest) organs, showing the heart and lungs. Also depicted are the ribs, aorta, vena cava, pulmonary artery, liver, stomach, and intestines.