In anatomy, several standard anatomical positions are used as references for describing the position and orientation of different body parts. These positions help provide a common frame of reference when discussing anatomical structures. The anatomical position is the standard reference point for describing the body's position and orientation. In this position:

The body is upright, facing forward, and standing erect.

The feet are parallel and flat on the floor.

The arms are hanging by the sides, with the palms facing forward.

The head and eyes are directed forward.

The most common reclining positions are the supine (face-up) and prone (face-down) positions. They get modified to several positions depending on the organs or side of the body under examination.

Supine position

The supine position is one of the most natural, stable, and safest positions on the surgical table. It allows anatomical structures to remain in natural neutral alignment, providing access to the anterior of the body. Patients in supine position can maintain adequate respiratory functions.

Under shock, hypotension, or pelvic surgery, the Trendelenburg position, a modification of the supine position that holds the person's back inclined fifteen to forty degrees with feet above the head, enables greater access to lower organs for a shorter duration. During childbirth, vaginal examinations, and pelvic surgeries, the supine position is modified to the lithotomy position with legs flexed and elevated using stirrups.

Prone position

In the prone position, the individual lies flat on their abdomen with their face and palms facing downward. Prone positioning has many benefits, as unlike the supine position, lung compression is minimal, resulting in higher oxygen levels. Additionally, the prone position redistributes blood and airflow more evenly, improving heart pumping when there is an imbalance between blood and airflow in conditions such as acute respiratory distress syndrome or ARDS. That means one requires less ventilator support, and constriction of the blood vessels of the lung decreases.

This text is adapted from Openstax, Anatomy and Physiology 2e, Section 1.6: Anatomical terminology.