The Skeletal System

(The bone framework of the body)

Like other vertebrates, humans have an internal skeleton that supports different muscles in their bodies, but also vital organs. The order and articulation of the bones of the skeleton also define the kind of the body's movements

The adult human skeleton generally has 206 bones, but this number can vary slightly from one individual to another: some people have, for example, a couple of additional ribs. The bones of the human body are divided between the axial skeleton (the bones of the skull and face, the vertebrae, the ribs, the sternum) and the appendicular skeleton, consisting of upper and lower extremities, as well as bone belts (bones of the shoulder and hips) that join them to the axial skeleton

Functions of the Skeletal System

• The human skeleton is a living and dynamic structure, which acts as a support and protection structure for the body

• The skeleton plays an important role in the movement by suppling a strong, stable and mobile structure on which the muscles can act. Provides body shape and support

• Bones are living structures and the main storage centers for essential body minerals such as calcium and phosphorus. Bones are living structures and the body's main storage centers for essential minerals such as calcium and phosphorus (the red bone marrow produces millions of blood cells every day)

Types of Bones: (shapes determined by functions)

The approximately 200 bones that make up the human skeleton do not all have the same shape. There are generally four types of bones by appearance: long bones, flat bones, short bones and irregular bones. This classification shows the adequacy between the shape of a bone and its function (shape, internal organization of the tissue, bone signs "characteristics of the surface; signs")

• Flat bones: like the ribs and bones of the skull, rather thin and flattened, flat bones perform two essential functions. Some protect fragile organs, such as the parietal pair of bone, which is part of the skull. Others, such as the shoulder blade, facilitate the anchoring of tendons thanks to their extended surface

• Long bones: like the femur they are found in the arms and legs. The long bone axes are called the diaphysis. The ends are called epiphyses. Epiphyses (containing the red marrow, which makes all red blood cells) form joints with other bones. The enlarged ends, which are mainly made up of spongy bone tissue, give stability to the joints

• Irregular bones: like the vertebrae, they have a shape that does not fit into any of the other categories. The vertebrae are specifically intended to protect, provide both  the stability and mobility to the spinal cord

• Short bones: the more or less cubic shape and the small size of the short bones help on the flexibility of the joints. This is the case of the talus, which allows the ankle to rotate

The patella, which is inserted into a ligament, is a particular example of a short bone called sesamoid because of its similarity to a sesame seed

Structure of the Skeleton

The Axial Skeleton

Skull: (An assembly of flat bones and irregular bones)

Careful observation of a skull can detect fine and irregular lines. They are sutures, rigid joints at the edges of the different cranial bones. In fact, the skull is not made up of a single bone, but of eight different elements that gradually weld together during growth. More numerous, the bones of the face take on irregular shapes. They are drawing the cavities of the mouth, the nostrils, the orbits and the paranasal sinuses

The skull is made up of more than two dozen bones, most of which merge to form a single solid unit that surrounds the brain and special sense organs. The remaining bones of the skull form the structure for the structures of the face. The upper part of the face, between the eyes and the upper teeth consists of the two jaws, the zygomatic bone is lateral to the jaw and forms the upper part of the cheek, the coupled nasal bones form the "bridge" of the nose. between the eyes. The lower teeth, or mandibular teeth, are mounted in "holds" in the jaw. The jaw is one of the few moving bones in the skull. The final bone of the orbit, the lacrimal bone, is a small bone near the nose that has a hole for the tear duct. Inside the skull, the palatine bones join the jaw and form the back of the hard palate

The skull of a newborn

At birth, the bones of the skull are not fully welded. Connected by membranes, the fountains maintain a certain mobility, allowing the head to deform during birth and therefore the skull to adapt to brain growth during the first years of the baby's life

Spinal Column: (the central axis of the body)

The vertebral column, also called the vertebral column, is the central axis of the human body. It extends from the back of the skull to the pelvis and consists of a chain of small bones, the vertebrae, which house the spinal cord and act as attachment points to the ribs and muscles

The Vertebrates: 

The human being has 33 vertebrae, which anatomists have divided into five categories: cervical, thoracic (or dorsal), lumbar, sacral and coccygeal. Despite some differences in proportions, all vertebrae have a similar structure: they all have a body, which is joined by various bone growths, the apophysis. These elements are organized to surround a central hole, the vertebral hole, through which the spinal cord passes

• The 8 cervical vertebrae form the neck. The first vertebra, the atlas, and articulates with the occipital bone. The 7 cervical vertebrae They are the most mobile of the vertebral column, articulate with the occipital condyles of the skull

• More voluminous than the cervical vertebrae, the 12 thoracic (or dorsal) vertebrae also have longer processes, which are articulated with the ribs

• The 5 lumbar vertebrae have a massive body, capable of supporting the weight of the abdomen

• The 5 sacred vertebrae are welded at the end of adolescence to form a single bone, the sacrum, which articulates with the pelvic bones

• The coccyx is formed by the fusion, between 20 and 30 years, 4 atrophic coccyx vertebrae

The union of the vertebrae: 

With the exception of those that make up the sacrum and coccyx, all vertebrae are mobile. They articulate with each other through small growths, the processes of the lower and upper joints. The body of each vertebra also rests on an intervertebral disc, which is a gelatinous mass whose role is to cushion shocks. This particular arrangement makes the spine strong and very flexible

Thorax : (Ribcage)

The ribs and sternum form the chest wall or chest. The sternum, or sternum, is located in the front and covers the heart and main blood vessels and respiratory tract

The thorax, which refers to the upper part of the human trunk, contains the lungs and heart. These vital bodies are protected by the rib cage, a bone box made up of twelve pairs of ribs articulated with the thoracic vertebrae and the sternum. The first ten pairs of ribs are attached to the sternum by cartilages of intermediate ribs, the flexibility of which allows the rib cage to deform during breathing. The two lower pairs of ribs, which are not attached to the sternum, are known as floating ribs

The appendicular skeleton

Shoulder Girdle

The upper ends are attached to the trunk through the shoulder belt. This part of the appendicular skeleton is made up of the clavicle and the scapula. The clavicle, commonly known as the "clavicle", is attached medially to the top of the sternum and laterally to the scapula in the front of the shoulder. the back of the shoulder and can feel like "the wing" in the upper back

Arms and hands:

• Bones of the arm: the arm is made up of several bones. The humerus is the bone closest to the arm and attaches to the scapula in the glenoid fossa. In the bone are two bones. The ray runs laterally along the lower part of the arm and the ulna runs medially next to it

• Bones of the hand: the palm of the hand is made up of the five metacarpal bones. Each of them extends through the phalanges, which are the bones of the fingers. Each finger has three successive phalanges (proximal phalanx, medial phalanx and distal phalanx), except the thumb, which has only two (proximal phalanx and distal phalanx). The complex assembly of the eight carpal bones makes up the wrist. Two of them, scaphoid bone and lunar bone, articulate with the radius

Pelvic Girdle

The pelvic belt forms the support frame for the lower limbs. Three bones merged on both sides of the pelvis to form a coxa os. The pelvic girdle is made up of 2 hip bones, which connect to the pubic symphysis. Each hip bone is made up of 3 sections: Illium, Ischium, Pubis. The ileum is a large bone, take fan-shaped that forms the upper of the pelvis. The upper surface is called the iliac crest. When he "puts his hands on his hips", he places them on the iliac crest. The pubic bone, or pubis, forms the upper part of the anterior part of the pelvis. The ischium is located towards the rear of the lower pelvis. These bones form the part of the pelvis where you sit

Legs and Feet

• Leg bones: the lower extremities are composed like to the upper extremities. The femur is located in the thigh region. This is the largest bone in the body. As with the arm, the lower leg consist of two bones. The largest medial bone is the tibia. This bone articulates with the femur and most of the weight is directed on this bone in the lower leg. The lateral fibula is much junior and acts to stabilize the leg

• Bones of the foot: the skeleton of the foot adopts a structure similar to that of the hand. A group of seven bones forms the tarsus, which forms the ankle and articulates with the tibia and fibula. Five metatarsal bones follow, which form the foot itself, then the phalanges. Like the toes, each toe is made up of three phalanges (proximal, medial and distal), except for the big toe, which has only two

Joints: (Joints between Bones) 

Joints or joints are designed for movement. The areas of contact between the bones are of utmost importance for the mobility and strength of the skeleton. The nature of the tissue that forms the joint between two or more bones largely determines the associated range of motion. The fibrous and cartilaginous joints have very reduced mobility, while the synovial joints allow for a wide variety of movements. However, the movements also rely largely on the form of the bones

Fibrous and cartilaginous joints

Some bones, such as those of the skull, are connected by very dense fibrous tissue. These fibrous joints, also called sutures, ensure protective immobility to the bones

When two bones are joined by cartilage tissue, their articulation allows very limited movements. This is the condition of the joint of the first rib with the sternum, known as  synchondrosis, or that of the pubic bones, symphysis

Synovial joints

The vast majority of the joints are mobile, that is, they allow the bones to move with each other, sometimes with great amplitude. These joints are defined by a fibrous capsule, which is a resistant fibrous tissue that has two layers, with the fibrous capsule lying outside the synovial membrane, the fibrous capsule permits strengthen the joint, while the synovial membrane lines the joint and produces the synovial fluid. firmly attached to the periosteum. The membrane that lines the inside of the capsule produces a fluid, the synovium, which fills the synovial cavity. Lubricates the joint and nourishes the cartilage that lines the ends of the bones

Ligaments

The bones are generally interconnected by ligaments, fibrous tissues intended to stabilize and strengthen the synovial joints. The knee joint has several types of ligaments

On both sides of the leg, the lateral ligaments connect the femur with the tibia and fibula and prevent lateral movements of the knee. At the front, the patellar ligament solidifies the joint. Finally, the cruciate ligaments restrict forward-backward knee movements

Types of synovial joints

• Ball and socket: shoulder and hip (the round head moves inside a cup) - This type of joint has maximum freedom of movement

• Hinge: articulation of the humerus to the ulna (canal and cylinder): it is very similar to the movement of a door, to the rotation from one side to the other

• Pivot: in a pivoting joint, a bone projection allows rotation. Example: the joint between the vertebrae of the neck that allows the head to rotate, the movement is limited to one plane. This joint allows rotation only around its longitudinal axis

• Condyloid: wrist, the movement can be in two planes. This joint allows for the second widest range of motion

• Gliding: carpal bones (flat surfaces slide from each other): the slipping of these bones is limited by the band of connective tissue that surrounds them

Disorders and problems of the skeletal system

Disorders of the skeletal system and bone injuries can be the result of many factors. These include: poor nutrition, infections, sports risk and recreational mishaps, accidents and poor posture

The skeletal system is also affected by degenerative disorders such as osteoporosis (osteoporosis is a "thinning" of the bones that is generally observed in the elderly. It can cause multiple types of fractures)

• Arthritis

• Osteoporosis

• Distortion

• Displacement

• Fracture