The T4 vertebra is the fourth thoracic vertebra that makes up the middle segment of spinal column of the human body. The thoracic spinal vertebrae consist of 12 total vertebrae and are located between the cervical vertebrae (which begin at the base of the skull) and the lumbar spinal vertebrae.

The spinal column supports the top of the human body. It extends from the pelvis up the length of the back, connecting to the skull. The spinal column is a structure that provides housing and protection for the spinal cord. The cord is the center of the neural network that connects the brain to the rest of the body, and carries out the function of sending signals to control breathing, heartbeat, and muscular contraction.

The vertebrae that make up the spinal column have a specific shape that is made to protect the spinal cord from injury. The T4 vertebra is located about midway up the spine. The portion of the spinal cord that the thoracic vertebrae protect is referred to as the thoracic cord. This part of the cord sends and receives signals from the area of the abdomen just above the waist. Injury to these vertebrae may cause several further problems, including the loss of feeling from the abdomen down to the lower extremities, permanent damage to the nerves, and even paralysis.