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How Many Lumbar Vertebrae Does A Human Have

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The Evolution Of The Spine Fueled The Rise Of Mammals—and Human Back Problems

Vertebral column, in vertebrate animals, the flexible spine extending from the neck to the tail, composed of a series of bones, the vertebrae. The main function of the spine is to protect the spinal cord; it also provides stiffening of the body and fixation of the pectoral and pelvic girdles and many muscles. In humans, an additional function is to transmit body weight when walking and standing.

Each vertebra in higher vertebrates consists of a ventral body, or centrum, surmounted by a Y-shaped neural arch. The arch extends a spinous process (projection) downward and backward that can be felt as a series of protrusions on the back and two transverse processes, one on each side, which provide attachment for muscles and ligaments. Together, the centrum and neural arch surround an opening, the vertebral foramen, through which the spinal cord passes. The centers are separated by cartilaginous intervertebral discs, which help to cushion the shock during locomotion.

The vertebrae of lower vertebrates are more complex and the relationships between their parts and those of higher animals are often unclear. In primitive chordates (e.g., amphioxus, lampreys), a rod-like structure, the notochord, stiffens the body and helps protect the overlying spinal cord. The notochord appears in the embryos of all vertebrates in the space later occupied by the vertebral bodies – in some fish it remains throughout life, surrounded by spool-shaped centers; in other vertebrates, it is lost in the developed animal. In primitive chordates, the spinal cord is protected dorsally by segmented cartilages – these foreshadow the development of the neural arch of the true vertebrae.

Fish have vertebrae in the trunk and caudals (tail); In legged land vertebrates, the vertebral column is subdivided into regions in which the vertebrae have different shapes and functions. Crocodilians and lizards, birds and mammals have five regions: (1) cervical, in the neck, (2) thoracic, in the thorax, which articulates with the ribs, (3) lumbar, in the lower back, more robust than the others vertebrae, (4) sacral, often fused to form a sacrum, which articulates with the pelvic girdle, (5) caudal, in the tail. The atlas and the axial vertebrae, the two upper cervicals, form a freely movable joint with the skull.

Vertebral Column Lumbar Vertebrae Of Human Skeleton System Anatomy Stock Illustration

The number of vertebrae in each region and in total varies according to the species. Snakes have the largest number, all of a very similar type. In turtles, some vertebrae may be fused to the shell (carapace); In birds, all vertebrae except the cervical vertebrae are usually fused into a rigid structure, which provides support during flight. Most mammals have seven cervical vertebrae; Size, not number, explains variations in neck length in different species. Whales have several specializations – the cervical vertebrae can be greatly reduced or greatly increased in number and the sacrum is absent. Humans have 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 3 to 5 fused caudal vertebrae (joints called the coccyx).

The spine is characterized by a variable number of curves. In quadrupeds, the spine is curved in a single arc (the highest portion occurs in the middle of the back), which functions as an arch spring in locomotion. In humans, this primary curve is modified by three more: (1) a sacral curve, in which the sacrum curves backward and helps support the abdominal organs, (2) an anterior cervical curve, which develops soon after birth. , as the head is lifted, and (3) a lumbar curve, also anterior, which develops as the child sits and walks. The lumbar curve is a permanent feature only of humans and their bipedal ancestors, although a temporary lumbar curve appears in other primates in the sitting position. The cervical curve disappears in humans when the head is tilted forward, but appears in other animals when the head is raised.

In humans, the structure and function of the spine can be affected by certain diseases, disorders, or injuries. Examples include scoliosis, lordosis, and kyphosis, which are deviations from the normal curvature of the spine; degenerative diseases such as osteoarthritis and Baastrup disease (kissing spine syndrome); and tuberculosis of the spine (Pott’s disease), which is caused by infection of the spine by viruses. The main section of this article may be too short to adequately summarize the key points. Consider expanding the lead to provide an accessible overview of all important aspects of the article. (September 2019)

The vertebral column, also known as the backbone or backbone, is the central part of the axial skeleton in vertebrate animals. The vertebral column is the defining feature of the vertebrate skeleton, in which the notochord (a flexible glycoprotein rod encased in collagen) found in all chordates has been replaced by a segmented series of irregular mineralized bones (or sometimes, cartilage) called vertebrae. , separated by fibrocartilaginous fibers. intervertebral discs (whose character is a remnant of the notochord).

Vertebral Column Lumbar Vertebrae Of Human Skeleton System Anatomy Stock Photo

The dorsal portion of the spine houses the spinal canal, a cavity formed by the alignment of neural arches that closes and protects the spinal cord.

The human spine is one of the most studied examples, as the general structure of human vertebrae is quite typical (homologous) to that found in other mammals, reptiles and birds. The shape of the vertebral body, however, varies somewhat between different groups of living species.

Individual vertebrae are named according to the corresponding region of the body (neck, chest, abdomen, pelvis, or tail). In clinical medicine, features of the vertebrae (particularly the spinous process) can be used as surface reference points to guide medical procedures such as lumbar punctures and spinal anesthesia. There are also many different spinal diseases in humans that can affect both bony vertebrae and intervertebral discs, with kyphosis/scoliosis, ankylosing spondylitis, degenerative discs, and spina bifida being recognizable examples.

The number of vertebrae in a region may vary, but overall the number remains the same. In a human spine, there are normally 33 vertebrae.

Ligaments Of The Human Spine Lumbar Vertebral Column And Sacrum Labeled On White Background Stock Photo

The upper 24 presacral vertebrae are articulated and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or coccyx. Articulated vertebrae are named according to the region of the spine. There are 7 cervical vertebrae, 12 thoracic vertebrae and 5 lumbar vertebrae. The number of those in the cervical region, however, is rarely changed,

In about 10% of people, both the total number of presacral vertebrae and the number of vertebrae in individual parts of the spine can vary.

The most frequent deviations are: 11 (rarely 13) thoracic vertebrae, 4 or 6 lumbar vertebrae, 3 or 5 coccygeal vertebrae (rarely up to 7).

There are ligaments that run along the spine in front and back, and between the vertebrae that join the spinous processes, transverse processes, and vertebral laminae.

Spinal Cord And Cauda Equina Of The Lumbar Spine

The vertebrae of the human spine are divided into different regions, which correspond to the curves of the spine. Articulated vertebrae are named according to the region of the spine. The vertebrae in these regions are essentially similar, with minor variations. These regions are called the cervical spine, thoracic spine, lumbar spine, sacrum, and coccyx. There are seven cervical vertebrae, twelve thoracic vertebrae and five lumbar vertebrae.

The number of vertebrae in a region may vary, but overall the number remains the same. The number of those in the cervical region, however, is rarely changed.

The vertebrae of the cervical, thoracic and lumbar spine are independent bones and are generally quite similar. The vertebrae of the sacrum and coccyx are often fused and unable to move independently. Two special vertebrae are the atlas and the axis, on which the head rests.

A typical vertebra consists of two parts: the vertebral body and the vertebral arch. The vertebral arch is posterior, meaning it faces a person’s back. Together, they close the vertebral foramen, which contains the spinal cord. Because the spinal cord is located in the lumbar spine and the sacrum and coccyx are fused, they do not contain a central foramen. The vertebral arch is formed by a pair of pedicles and a pair of laminae, and supports several processes, four articular, two transverse and one spinous, the latter also known as the neural spine. Two transverse processes and a spinous process are posterior (behind) the vertebral body. The spinous process exits from the back, a transverse process exits from the left and another from the right. The spinous processes of the cervical and lumbar regions can be felt through the skin.

Muscles Of The Lumbar Spine Of The Trunk

Above and below each vertebra are joints called facet joints. They restrict the possible range of motion and are joined by a thin portion of the

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