Back Anatomy

The back is the area opposite the chest, located at the back of the human body, between the shoulders and the waist. This area has a very important anatomical and biomechanical function, which we will discuss below. But this is not the only thing you will read about, we will also show you the different ligaments and joints of this part of the body.

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Parts and anatomy of the back

Bones and spine

• Thoracic vertebrae: A set of 12 vertebrae called T1 to T12 inclusive. It arises from the seventh cervical vertebra in the neck to the first lumbar vertebra L1 in the lower back.
• Lumbar vertebrae: These bony tissues start from the thoracic vertebra T12 to the sacrum.
• Sacrum: This can be considered as part of the hip or as an integral bone of the lower back. It connects from the last lumbar vertebra at the top to the coccyx.
• Coccyx: The last bone forming the human spine. The spine is made up of the vertebrae, the sacrum and this bony tissue.
• Ribs: These are thin bones that extend from each of the thoracic vertebrae to the front of the body. Their purpose is to protect the vital organs.
• Scapula: Also known as the scapula. It is a flat, wide bone whose mission is to maintain balance while walking.

Muscles

• Trapezius: Its origin and insertion are multiple. It originates in the occipital protuberance of the nape of the neck in the posterior cervical ligament and in the apophysis from the seventh cervical to the tenth and all its supraspinous ligaments. It inserts on the posterior border of the clavicle, on the acromion and on the spine of the scapula. Its action is to keep the scapula balanced and to limit movement in the spine.
• Epispinous or spinous: Tissues located along the spine whose function is to join spinous processes between distant vertebrae. It is part of the "erector spinae" group of muscles and tendons.
• Latissimus dorsi: The lumbar vertebrae T7 to T12, the iliac crest, ribs 10 to 12 and the thoracolumbar fascia are the sites of origin of this back muscle. It inserts into the lesser tubercle of the humerus to allow dorsal flexion and arm movements.
• Iliocostalis: This muscle can be divided into three sections (lumbar, dorsal and cervical) due to the different sites of origin. The transverse processes of the lumbar and thoracic vertebrae, the sacrum and the iliac crest up to the ribs is the route of this tissue. Its action allows the extension of the back.
• Lesser rhomboid: The seventh cervical and first thoracic vertebrae to the medial border of the scapula is the path taken by this muscle to fix the scapula and rotate the glenoid cavity of the shoulder.
• Greater rhomboid: This muscle allows the scapula to be held medially and compressed at the ribs. It does this because of its position in the back, from the second to the fifth thoracic vertebra to the edge of the scapula.
• Splenius: The ligament of the nape of the neck gives rise to the birth of this broad muscle, while the 7 cervical vertebrae and the first 4 thoracic vertebrae see the insertion of this tissue. This allows for the tilt and rotation of the skull.
• Levator scapulae: This is a muscle is also known as the angular muscle of the scapula. It runs from the process of cervical vertebrae 1 to 4 to the medial border of the scapula. It gives rise to rotation of the scapula in the glenoid cavity and elevation of the scapula in other movements.
• Serratus anterior: Its three origins occur in the first 10 ribs and insert into different parts of the scapula. Their actions allow them to fix the scapula to the thorax and to elevate the ribs in the breathing process.
• Serratus posterioris: It runs from the 11th thoracic vertebra and from the second lumbar vertebra to ribs IX to XII. The work of this muscle is to lower the lower area of the aforementioned ribs for the exhalation movement.
• Roundus major: Connects in the groove of the tubercle of the humerus with the inferior angle of the scapula to achieve extension and rotation of the arm.
• Intertransverse: A system of muscles and ligaments that allow the spine to be held upright. This group includes the rotators, the semispinatus and the multifidus.
• Infraspinatus: It originates in the infraspinous fossa and inserts into the greater tubercle of the humerus bone. This allows different movements of the arm.
• External Oblique: The ribs V to XII in their external part give origin to this muscle tissue, it is inserted from the midline of the abdomen to the navel (linea alba) up to the inguinal ligament.
• Deltoid: This muscle can be considered as part of the shoulder or back because it originates from the crest of the spine of the scapula, the acromion and the clavicle and inserts into the humerus. It allows different movements of the arm.

Ligaments

• Yellow, flavo or flavum: This is a ligament that connects the first segment of the sacrum to the axis of the arches of the vertebrae.
• Anterior longitudinal: This tape is responsible for joining the anterior surfaces of the vertebrae to the posterior area of the sacrum.
• Posterior longitudinal: This has a similar course to the anterior ligament, but differs from it in that it runs along the inside of the vertebral canal.
• Alars: This group of ligaments is responsible for connecting and controlling the rotation of the skull by connecting the tubercles of the occipital condyle to the second cervical vertebra.
• Apical odontoid: This is the name given to the cord connecting the foramen magnum to the odontoid process.
• Intra-articular of the head of the ribs: It divides the joint into two parts because it runs from the head of the rib to the intervertebral cartilage.
• Sacrospinous: this is the ligament responsible for joining the ischium to the sacrum and coccyx.
• Costotransverse: this ligament joins the neck of the rib to the transverse process. It can be divided into two parts, lateral and superior.
• Supraspinatus: This is a set of ligaments which are responsible for holding tight the spinous process of the cervical vertebra (7C) to the sacrum.
• Cruciform of the atlas: The atlas is the first cervical vertebra that joins the spine to the neck. This tissue is responsible for this work.
• Lumbar-costal: It connects the processes of the first and second lumbar vertebrae to the 12th rib.
• Nuchal: This connective tissue is in charge of holding together the external protuberance of the nuchal line up to the process of the 7C vertebra.
• Spread from the rib head: This band connects each of the rib heads to the intervertebral cartilage and the bodies of the two corresponding vertebrae.
• Deep posterior sacrococcygeus: connects the lower sacral canal with the posterior area of the coccyx.
• Sacrotuberous: connects the transverse tubercles of the sacrum to the lower part of the ilium and coccyx.
• Transversus atlas: this fibrous band is responsible for holding together the odontoid process with the atlas ring.
• Superficial posterior acrococcygeus: this band is responsible for connecting the lower opening of the sacrum with the posterior area of the coccyx bone.
• Lateral acrococcygeus: Like the anterior ligament, this band connects the coccyx to the sacrum, but from the lower lateral corner of the sacrum.
• Interspinous ligaments: These are responsible for connecting the root to the apex of each adjacent spinous process.
• Intertransverse: The name refers to the function of these ligaments, which are responsible for joining the vertebrae on their external transverse sides.
• Anterior iliac sacral: The preauricular groove and the auricular surface of the ilium are connected to the sacrum by this ligament.
• Posterior iliac sacral: The sacrum and the ilium are connected by these posteriorly located fascicles.
• Sacro iliac interosseous: The tuberosities of the sacrum and ilium are connected by these ligaments.

Biomechanics of the spine

• Flexion: This biomechanical muscular movement consists of tilting the lumbar spine towards the front of the body while keeping the pelvis fixed. In this way, an amplitude of 60 to 90° can be produced.
• Extension: By keeping the hip fixed, it is possible to tilt the spine backwards. This causes an opening of 25 to 35°.
• Axial rotation: It is possible to rotate, keeping the legs and hips fixed, the torso on its own axis with an amplitude of 35° to 40°. This movement is also known as spinal rotation.
• Lateral flexion: This consists of leaning the body to one side of the body by up to 40°, with the spine as the axis.