Skeletal system

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Skeletal System Concept:

The skeletal system is made up of bones and cartilage.

Bones Concept:

Bones are whitish, very hard organs that unite with others through joints or joints constitute the Skeleton. It is a specialized form of connective tissue whose main feature is the mineralization (calcium) of its bone matrix (collagen and proteoglycan fibers).

Bone is a living, complex and dynamic tissue. A solid, highly specialized form of connective tissue that forms the bulk of the skeleton and is the body's primary supporting tissue. Bone tissue participates in a continuous process of dynamic remodeling, producing new bone and degrading old bone.

Bone is made up of several different tissues: bone, cartilaginous, dense connective, epithelial, adipose, nervous, and various blood-forming tissues.

As for bone irrigation, we have the Volkman channels and the Havers channels. Bone tissue has no lymphatic vessels, only periosteum tissue has lymphatic drainage.  

Havers Channels are a series of tubes around narrow channels formed by concentric coverslips of collagen fibers. This region is called compact bone or diaphysis. Blood vessels and nerve cells throughout the bone communicate by osteocytes (which emit cytoplasmic expansions that contact one osteocyte with another) in gaps (spaces within the dense bone matrix that contain bone cells). This original arrangement is conducive to the deposit of mineral salt, which gives resistance to bone tissue. It should also be noted that these channels run along the bone longitudinally leading within their light, blood vessels and nerves that are responsible for the nutrition of bone tissue. It causes blood vessels to pass through bone tissue.  

Volkmann channels are microscopic channels found inthe compact bone, are perpendicular to the Havers Channels, and are one of the components of the Haversian system. Volkmann's channels can also carry small arteries throughout the bone. Volkmann's channels do not have concentric lamellae.
Inside the bone matrix there are spaces called gaps that contain bone cells called osteocytes. Each osteocyte has extensions called canaliculi, which extend from the gaps and join the canaliculi of the surrounding gaps, thus forming a network of canaliculi and gaps throughout the mineralized tissue mass.

Cartilage Concept:

It is an elastic form of semi-rigid connective tissue & #8211; forms parts of the skeleton in which movement occurs. Cartilage does not have its own blood supply; consequently, their cells obtain long-range diffusion oxygen and nutrients.

Articular Cartilage

Articular Cartilage



Skeletal System Functions:

& #8211; Body Support (Body Support)

& #8211; Protection of vital structures (heart, lungs, brain)

& #8211; Mechanical base for movement

& #8211; Salt storage (eg calcium)

& #8211; Hematopoietic (continuous supply of new blood cells)

Number of Human Body Bones:

It's classic to admit the number of 206 bones.

Head = 22


Skull = 08

Face = 14


Neck = 8

7 vertebrae


Chest = 37

24 ribs

12 vertebrae

1 sternum


Abdomen = 7

5 lumbar vertebrae

1 sacrum

1 coccyx

Superior Member = 32


Scapular Waist = 2

Arm = 1

Forearm = 2

Hand = 27


Lower member = 31

Pelvic Waist = 1

Thigh = 1

Knee = 1

Leg = 2

Foot = 26


Middle Ear Ossicles = 3

Skeleton Division:

Axial skeleton & #8211; Composed of the bones of the head, neck and trunk.

Appendicular Skeleton & #8211; Consisting of upper and lower limbs.

The union of the axial skeleton with the appendicular is done through the shoulder and pelvic girdles.

Division of Skeleton into Armpit Skeleton and Appendicular Skeleton


Bones Classification:

Bones are classified according to their shape into:

Long Bones:
It has a length greater than a width and consists of a body and two ends. They are slightly curved, which guarantees them greater strength. Slightly curved bone absorbs the mechanical stress of body weight at various points, so that it is better distributed. The long bones have their diaphyses formed by compact bone tissue and present large amount of cancellous bone tissue in their epiphyses.  Example: Femur.Long Bones Femur Example

Short Bones: They look like a cube, having their lengths almost equal to their widths. They are composed of cancellous bone except on the surface where there is a thin layer of compact bone tissue.  Example: Carpal bones.

Short Bones Example Carpal Bones

Laminate Bones (Plans): They are thin bones and consist of two parallel blades of compact bone tissue with a cancellous bone layer between them. Flat bones provide considerable protection and generate large areas for muscle insertion. Examples: Frontal and Parietal.

Flat Bones Example Parietal Bone

In addition to these three well-defined basic groups, there are other intermediates, which can be distributed into 5 groups:

Elongated Bones:
They are long bones, but flat and have no central canal. Example: Ribs.

Elongated Bones Rib Example

Pneumatic bones
: They are hollow bone, with cavities full of air and lined with mucosa (breasts), presenting small weight in relation to its volume. Example: Sphenoid.

Pneumatic Bones Sphenoid Example

Irregular Bones: They have complex shapes and cannot be grouped into any of the previous categories. They have varying amounts of cancellous bone and compact bone.  Example: Vertebrae.

Irregular Bones Vertebra Example


Sesamoids: Are present in the
inside some tendons where there is considerable friction, tension and physical stress such as the palms and plants. They may vary in size and number, from person to person, they are not always completely ossified, usually measuring just a few millimeters in diameter. Notable exceptions are the two patellae, which are large sesamoid bones, present in almost every human being.

Sesamoides Bones Patella Example
Sutural Bones:
They are small bones located inside joints, called sutures, between some bones of the skull. Their numbers vary greatly from person to person.

Sutural bones bones located between the skull sutures


Long Bone Structure:

The arrangement of compact and spongy bone tissues in a long bone is responsible for its strength. Long bones contain growth and remodeling sites, and joint-associated structures. The parts of a long bone are as follows:

Diaphysis: is the long stem of the bone. It consists mainly of compact bone tissue, providing considerable resistance to long bone.

Epiphysis: the widened extremities of a long bone. The epiphysis of a bone joins, or joins, to a second bone, in a joint. Each epiphysis consists of a thin layer of compact bone lining the cancellous bone and covered with cartilage.

Metaphysis: dilated part of the diaphysis closest to the epiphysis.

Long Bone Structure Epiphysis and Diaphysis


External Bone Configuration:

Articular Non articular
 & #8211; Head


& #8211; Condyle

& #8211; Facet

 & #8211; Processes


& #8211; Tubers

& #8211; Exchanger

& #8211; Spine

& #8211; Eminence

& #8211; Blades

& #8211; Ridges

   Femoral Head Bone Overhangs Bone Protrusions Vertebrae Processes
Femur Head Transverse and Spiny Processes (Vertebrae)
Articular Non articular
& #8211; Cavities


& #8211; Acetabular

& #8211; Fovea

 & #8211; Pits


& #8211; Furrows

& #8211; Foramen

& #8211; Meatos

& #8211; Breasts

& #8211; Fissures

& #8211; Channels

 Joint Depression Scapular Glenoid Cavity  Non-Articular Salience Olecranian Femoral Fossa
Glenoid Cavity (Scapula) Olecranian Fossa (Humerus)

Internal Bone Configuration:

The differences between the two types of bone, compact and spongy or reticular, depend on the relative amount of solid substances and the amount and size of the spaces they contain. All bones have a thin superficial blade of compact bone around a central mass of cancellous bone, except where the latter is replaced by a medullary cavity.

The compact bone of the body, or diaphysis, surrounding the medullary cavity is the cortical substance. The architecture of the cancellous and compact bone varies by function. Compact bone provides strength to support weight.

In long bones designed for stiffness and insertion of muscles and ligaments, the amount of compact bone is maximum near the middle of the body where it is subject to bend. The bones have some elasticity (flexibility) and great rigidity.

Periosteum and Endosteum:

THE Periosteum It is a dense, very fibrous connective tissue membrane that lines the outer surface of the diaphysis, securely attaching to the entire outer surface of the bone except the articular cartilage. Protects the bone and serves as the attachment point for the muscles and contains the blood vessels that nourish the underlying bone.

 THE Endosteo It is found within the medullary cavity of the bone, lined with connective tissue.

Internal Bone Configuration Compact Tissue and Sponge Tissue

Compact Bone Tissue Spongy Bone Tissue
Contains few spaces in its rigid components. Gives protection and support and resists the forces produced by weight and movement. Usually found in diaphyses. It makes up most of the fabric
Bone of short, flat and irregular bones. Most are found in the epiphyses.




  After studying the General Skeletal System, we invite you to study the bones divided by region:




Superior Member

Lower member

Are you ready to test your knowledge? Then click below to answer the Skeletal System quiz