Illustration of ambulatory devices to assist those with chronic gait disorders. A walker, cane, and pair of forearm crutches are shown, with insets of optional attachments for the walker and forearm crutches.

Illustration of streptococcus (Streptococcus pneumoniae) bacteria, schematically depicted in coccoidal chains and diplococci.

Illustration of a normal human bone, showing a section of a long bone cortex with normal cortical and trabecular thicknesses. The cortex is the outer layer of the bone, and the trabeculae are the intersecting osseous bars in the interior of the bone.

Illustration of osteoporosis of a human bone, showing a section of long bone cortex with a loss of bone tissue that has resulted in a fracture. The cortex and trabeculae are thinner than normal. The cortex is the outer layer of the bone, and the trabeculae are the intersecting osseous bars in the interior of the bone.

Illustration of elderly brain cell activity. Shown (foreground) is the activity at the synaptic connection between two brain cells (neurons), with neurotransmitter substances being released into the gap between the cells. An elderly person with the brain visible is also shown (background).

Illustration of a brain cell synapse. The neuron's axon is shown firing a neurotransmitter substance across the synaptic cleft to a knob on the recipient neuron.

Illustration of a brain cell synapse. The neuron's axon is shown firing a neurotransmitter substance across the synaptic cleft to a knob on the recipient neuron.

Illustration of a brain cell synapse. The neuron's axon is shown firing a neurotransmitter substance across the synaptic cleft to a knob on the recipient neuron.

Illustration of a sagittal section of a brain, brain stem, and spinal cord superimposed over a stylized silhouette of a male head.

Illustration of a sagittal section of a brain, brain stem, and spinal cord superimposed over a stylized silhouette of a male head.

Illustration of a sagittal section of a brain, brain stem, and spinal cord superimposed over a stylized silhouette of a male head.

Illustration of a sagittal section of a brain and brain stem superimposed over a silhouette of a male head.

Illustration of a brain showing epileptic seizure activity, front view. Electroencephalogram (EEG) tracings show abnormal waveforms emanating from the temporal lobe (blue-green) of the brain.

Illustration of a brain, showing a hemorrhagic stroke (left) and an ischemic stroke (right). An hemorrhagic stroke is due to bleeding caused by the bursting of a blood vessel. An ischemic stroke is due to the lack of blood to a region of the brain caused by a blood clot.

Illustration of cervical cancer. The cervix shows cancer cells (light pink) on its anterior lip. Also shown are a cutaway frontal view of the uterus, vagina, and cervix. For reference, a line drawing of an ovary and fallopian tube are included.

Illustration of cervical cancer. The cervix shows cancer cells (light pink) on its anterior lip. A cutaway frontal view of the uterus, vagina, and cervix is shown. For reference, a line drawing of an ovary and fallopian tube is included.

Illustration of cervical cancer. The cervix shows cancer cells (light pink) on its anterior lip. A cutaway frontal view of the uterus, vagina, and cervix is shown. For reference, a line drawing of an ovary and fallopian tube is included.

Illustration of a young child with a high fever (febrile). A thermometer is shown in the foreground.

Illustration of deep vein thrombosis (DVT) in the femoral vein of the thigh. Deep vein thrombosis, the formation of a thrombus (non-mobile blood clot) in a deep vein, may lead to an embolism, a sudden blockage of a blood vessel caused by an embolus (mobile clot) that has broken off from a thrombus. An embolus breaking off is shown in the enlarged inset.

Illustration of diagnostic protocols for jaundice, showing an ultrasound scan of the liver and a urine sample test.