Illustration of the laparoscopic instruments used in a cholecystectomy (gallbladder removal) procedure, shown in a female abdomen, anterior view.

Illustration of a tracheostomy tube placed in a child with subglottic stenosis, a narrowing of the subglottic airway.

Illustration of an injury to the common bile duct occurring during a cholecystectomy (gallbladder removal) procedure.

Illustration showing the rule of nines for body surface area by region. These regions are used by medical professionals to determine the percentage of body surface involvement for widespread defects or trauma, especially burns.

The anatomy of the knee in relation to the saphenous nerve. The anterior skeletal view (left) shows the knee bones (femur, patella, tibia, and fibula) and the saphenous nerve with its infrapatellar and medial crural branches. The superior view of the tibial plateau and surrounding soft tissues (right), shows the parallel saphenous nerve and vein positions.

Illustration of a birth injury: classic shoulder dystocia, or brachial plexus injury, during vaginal delivery. The baby's left shoulder is partially trapped beneath the mother's pubic symphysis (pubic bone). As the deliverer exerts more pressure to extract the baby, the brachial plexus nerves are stretched and injured.

Illustration of a birth injury: shoulder dystocia, or brachial plexus injury, during vaginal delivery with a vaccuum extractor (ventouse). The baby's left shoulder is partially trapped beneath the mother's pubic symphysis (pubic bone). As more force is applied to extract the baby from the birth canal, the brachial plexus nerves are stretched and injured.

Illustration of a birth injury: shoulder dystocia, or brachial plexus injury, during vaginal delivery with a vaccuum extractor (ventouse). The baby's right shoulder is partially trapped beneath the mother's pubic symphysis (pubic bone). As more force is applied to extract the baby from the birth canal, the brachial plexus nerves are stretched and injured.

Illustration of the cervical, thoracic, lumbar, and sacral dermatomes, anterior and posterior views. A dermatome is an area of skin supplied by a single, specific spinal nerve root.

Illustration of a closed head injury, showing a front-to-back whiplash motion: A) normal position of the head and neck; B) hyperextension with the frontal region impacting the inner surface of the skull; C) hyperflexion with the occipital region impacting the skull; D) resulting brain damage to the frontal and occipital regions.

Illustration of a closed head injury, showing a side-to-side whiplash motion: A) normal position of the head and neck; B) left frontotemporal region impacting the inner surface of the skull; C) right frontotemporal region impacting the skull; D) brain damage to the frontotemporal regions.

Inner ear anatomy and equilibrium, with a labeled labyrinth (bottom left). Dynamic equilibrium is detailed in an enlarged view of one of three ampula (top right), showing the flow of endolymph over the crista. Static equilibrium is detailed in an enlarged view of the macula of the utricle and saccule (bottom right) showing hair cell stimulation by otoliths.

Illustration of intubation: correct placement of an endotracheal tube into the trachea, past the vocal cords to the level of the carina, or bifurcation of the airway, into the left and right bronchi (left), and incorrect esophageal intubation, which occurs when the tube is threaded into the esophagus and down to the stomach (right).

Illustration showing proper laryngoscopic endotracheal intubation of a patient.

Illustration of a blocked coronary artery: obstruction of the left anterior descending (LAD) coronary artery, the so-called artery of sudden death, with the resulting myocardial infarction (heart attack).

Illustration of an epidural nerve block injection being administered to a patient.

Illustration of balloon angioplasty (left to right): 1) orientation of the left interventricular branch of the left coronary artery, anterior view; 2) a deflated balloon catheter in the artery, sagittal view; 3) an inflated balloon compressing plaque against the arterial walls, sagittal view.

Illustration of myocardial ischemia (heart muscle death) following an acute myocardial infarction (heart attack), with a detail of the blocked distal left anterior descending (LAD) coronary artery. Dead, discolored, ischemic, and damaged heart muscle tissue is seen below the blocked artery.

Illustration of coronary artery disease: 1) orientation of the heart and coronary arteries, anterior view; 2) detail of a coronary artery showing plaque within the lumen of the vessel, cutaway view.

Illustration of coronary artery disease (left to right): 1) orientation of the heart and coronary arteries, anterior view; detail of normal blood flow through the left anterior descending (LAD) coronary artery, cutaway view; 3) detail of the LAD coronary artery with a blood clot and plaque blocking bloodflow through the vessel, cutaway view.