Thoracic vertebrae

In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical and lumbar vertebrae; they increase in size going towards the lumbar vertebrae, with the lower ones being a lot larger than the upper. They are distinguished by the presence of facets on the sides of the bodies for articulation with the heads of the ribs, and facets on the transverse processes of all, except the eleventh and twelfth, for articulation with the tubercles of the ribs. By convention, the human thoracic vertebrae are numbered T1-T12, with the first one (T1) located closest to the skull and the others going down the spine towards the lumbar region.

General characteristics

These are the general characteristics of the second through eighth thoracic vertebrae. The first and ninth through twelfth vertebrae contain certain peculiarities, and are detailed below.

Human body

The human body is the entire structure of a human being and comprises a head, neck, trunk (which includes the thorax and abdomen), arms and hands, legs and feet. Every part of the body is composed of various types of cells, the fundamental unit of life.

At maturity, the estimated average number of cells in the body is given as 37.2 trillion. This number is stated to be of partial data and to be used as a starting point for further calculations. The number given is arrived at by totalling the cell numbers of all the organs of the body and cell types. The composition of the human body is made up of a number of certain elements including carbon, calcium and phosphorus.

The study of the human body involves anatomy and physiology. The human body can show anatomical non-pathological anomalies known as variations which need to be able to be recognised. Physiology focuses on the systems and their organs of the human body and their functions. Many systems and mechanisms interact in order to maintain homeostasis.

Anatomy

Anatomy is the branch of biology concerned with the study of the structure of organisms and their parts. In some of its facets, anatomy is related to embryology and comparative anatomy, which itself is closely related to evolutionary biology and phylogeny.Human anatomy is one of the basic essential sciences of medicine.

The discipline of anatomy is divided into macroscopic and microscopic anatomy. Macroscopic anatomy, or gross anatomy, is the examination of an animal's body parts using unaided eyesight. Gross anatomy also includes the branch of superficial anatomy. Microscopic anatomy involves the use of optical instruments in the study of the tissues of various structures, known as histology, and also in the study of cells.

The history of anatomy is characterized by a progressive understanding of the functions of the organs and structures of the human body. Methods have also improved dramatically, advancing from the examination of animals by dissection of carcasses and cadavers (corpses) to 20th century medical imaging techniques including X-ray, ultrasound, and magnetic resonance imaging.