Skeletal System
The skeletal system is your body's central framework. It consists of bones and connective tissue, including cartilage, tendons, and ligaments. It's also called the musculoskeletal system.
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| Skeletal System |
What is Skeletal System?
It is the body system composed of bones, cartilages, ligaments and other tissues that accomplish essential functions for the human body.
Bone is a specialized type of connective tissue.
The skeletal system (bones)
The axial skeleton, comprising the spine, chest and head, contains 80 bones. The appendicular skeleton, comprising the arms and legs, including the shoulder and pelvic girdles, contains 126 bones, bringing the total for the entire skeleton to 206 bones.
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| The skeletal system (bones) |
Skull:
There are 22 bones in the skull. Including the bones of the middle ear, the head contains 28 bones.
1. Cranial bones (8)
- Occipital bone
- Parietal bones (2)
- Frontal bone
- Temporal bones (2)
- Sphenoid bone (sometimes counted as facial)
- Ethmoid bone (sometimes counted as facial)
2. Facial bones (14)
- Nasal bones (2)
- Maxillae (upper jaw) (2)
- Lacrimal bone (2)
- Zygomatic bone (cheek bones) (2)
- Palatine bone (2)
- Inferior nasal concha (2)
- Vomer (1)
- Mandible (1)
3. Middle ears (6 bones in total, 3 on each side)
- Malleus (2)
- Incus (2)
- Stapes (2)
Spine (vertebral column):
A fully grown adult features 26 bones in the spine, whereas a child can have 34.
- Cervical vertebrae (7 bones)
- Thoracic vertebrae (12 bones)
- Lumbar vertebrae (5 bones)
- Sacrum (5 bones at birth, fused into one after adolescence)
- Coccygeal vertebrae/Cordal (1 bone)
Set of 4 bones at birth; some or all fuse together, but there seems to be a disagreement between researchers as to what the most common number should be. Some say the most common is 1, others say 2 or 3, with 4 being the least likely. It is counted as 1 in this article.
Chest (thorax):
Various bones of the human skeletal system.
There are usually 26 bones in the chest but sometimes there can be additional cervical ribs in humans. Cervical ribs occur naturally in other animals such as reptiles.
- Hyoid bone (1)
- Sternum (1 or 3)
- Ribs (24, in 12 pairs)
Cervical ribs are extra ribs that occur in some humans.
Arm: There are a total of 64 bones in the arms.
Upper arm bones (6 bones in total; 3 on each side)
- Humerus (2)
Pectoral girdle (shoulder)
- Scapula (2)
- Clavicles (2)
- Ulna (2)
- Radius (2)
Hand (54 bones in total; 27 in each hand)
Carpals (16 bones)
- Scaphoid bone (2)
- Lunate bone (2)
- Triquetral bone (2)
- Pisiform bone (2)
- Trapezium (2)
- Trapezoid bone (2)
- Capitate bone (2)
- Hamate bone (2)
Metacarpals (10 bones in total; 5 on each side) Phalanges of the hand (28 bones)
- Proximal phalanges (10 bones in total; 5 on each side)
- Intermediate phalanges (8 bones in total; 4 on each side)
- Distal phalanges (10 bones in total; 5 on each side)
Pelvis (pelvic girdle):
The pelvis (or hip bone) is made up of three regions that have fused to form two coxal bones. They are: ilium, ischium, and pubis
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| Pelvis (pelvic girdle) |
The sacrum and the coccyx attach to the two hip bones to form the pelvis, but are more important to the spinal column, where they are counted.
Leg:
There are a total of 60 bones in the legs.
- Femur (2 bones)
- Patella or kneecap (2 bones)
- Tibia (2 bones)
- Fibula (2 bones)
- Foot (52 bones in total, 26 per foot)
Tarsus/Tarsals (14 bones)
- Calcaneus or heel bone (2 bones)
- Talus (2 bones)
- Navicular bone (2 bones)
- Medial cuneiform bone (2 bones)
- Intermediate cuneiform bone (2 bones)
- Lateral cuneiform bone (2 bones)
- Cuboid bone (2 bones)
Metatarsals (10 bones)
Phalanges of the foot (28 bones)
- Proximal phalanges (10 bones)
- Intermediate phalanges ( 8 bones)
- Distal phalanges ( 10 bones)
What is Skeletal System?
It is the body system composed of bones, cartilages, ligaments and other tissues that accomplish essential functions for the human body.
Bone is a specialized type of connective tissue.
The skeletal system works as a support structure for your body. It gives the body its shape, allows movement, makes blood cells, provides protection for organs and stores minerals.
The system made up the organs and tissues that are responsible for structural shaping and movements of the body. Components of musculoskeletal system-
- Bones
- Cartilages
- Joints
- Muscles
- Associated other connective tissues
Skeletal system is described according to subdivisions of the body. The subdivision are-
- Thorax
- Abdomen and pelvis
- Upper limb
- Lower limb
- Head & neck
- Back
Hematopoiesis – the formation of blood cells from hematopoietic stem cells found in the bone marrow.
Hematopoiesis is the production of all of the cellular components of blood and blood plasma.
It occurs within the hematopoietic system, which includes organs and tissues such as the bone marrow, liver, and spleen.
The main functions of the skeletal system. The skeleton has six main functions:
- Support – the skeleton keeps the body upright and provides a framework for muscle and tissue attachment.
- Posture – the skeleton gives the correct shape to our body.
- Protection – the bones of the skeleton protect the internal organs and reduce the risk of injury on impact. For example, the cranium protects the brain, the ribs offer protection to the heart and lungs, the vertebrae protect the spinal cord and the pelvis offers protection to the sensitive reproductive organs.
- Movement – the skeleton allows movement of the body as a whole and its individual parts. The bones form joints and act as levers, allowing muscles to pull on them to produce movement. The bones of the skeleton provide surfaces for the attachment of muscles.
- Blood cell production – certain bones in the skeleton contain bone marrow which produces red blood cells, white blood cells and platelets. Examples of bones that contain marrow are the pelvis, sternum, humerus and femur.
- Storage of minerals - the bones store minerals such as calcium, iron, potassium and phosphorous and release them into the blood when the body needs to use them.
Bone:
Bone is a special type of highly vascular, mineralized and constantly changing rigid connective tissue which forms the framework of body.
Composition of bone: bone is composed of:
Cell:-
- Osteocyte
- Osteoblast
- Osteoclast
Intercellular matrix:-
-Water
-Organic
- Collagen fibers
- Glycosaminoglycan-(1). Chondroitin sulphate, (2). Keratan sulphate
-Inorganic
- Calcium phosphate
- Calcium carbonate
- Magnesium phosphate
- Others-Na, K, I, Fe, CI
Function of bones:-
- Give shape to the body
- Give support to the body
- Provide surface for the attachment of muscles, tendons & ligaments.
- Produce blood cells.
- Mechanical protection of vital organs such as brain, heart, lung.
- Storage of body calcium & phosphorus.
Classification of bone:
Microscopically
- Compact or dense-e.g. shaft of long bone.
- Spongy or cancellous bone-ends of long bone.
According to position
- Axial: bone forming the axis of the body. e.g. skull rib etc
- Appendicular: bone forming the skeletal of limbs. e.g. radius, femur etc.
Periosteum:-
Periosteum is a fibrous connective tissue membrane which covers external surface of long bone except articular surface.
Function:
- Provide medium of attachment
- Responsible for regeneration of bone
- It forms vascular bed to provide supply to underlying bone.
- Protects the bone
- prevent over growth
Bone marrow:-
Bone marrow is a soft connective tissue which occupies in the medullary cavity of the long bones.
Types:
- Red bone marrow-in structure it consist of reticular cells associate with reticular fibers and blood forming cells.
- Yellow bone marrow-it consist mainly adipose cells with an ad mixture of macrophages and reticular cell.
Functions:
- Produce blood cell
- Storage of iron
- Perform immunological function
- Produce bone forming cell
Bone, rigid body tissue consisting of cells embedded in an abundant hard intercellular material.
The two principal components are collagen and calcium phosphate.
Bone tissue makes up the individual bones of the human skeletal system and the skeletons of other vertebrates.
Almost 70% of bone is made up of bone mineral called hydroxyapatite.
Endochondral - formation of bone onto a temporary cartilage model or scaffold
Intramembranous - formation of bone directly onto fibrous connective tissue. There is no intermediate cartilage stage. This type of ossification occurs in a few specialised places such as the flat bones of skull (i.e. parietal bone), mandible, maxilla and clavicles. Mesenchyme cells differentiate into osteoprogenitor cells, then into osteoblasts, which secrete the bone matrix. Once the osteoblasts are embedded in the bone matrix, they are known as osteocytes.
Mature bone has 2 types:
- Compact - which is found in the shafts of long bones (in the diaphyses). This makes up 80% of all bone.
- Spongy (cancellous) bone - which is found at the ends of long bones (in the epiphysis). This makes up 20% of all bone. This type of bone contains red bone marrow and a network of bony trabeculae.
A 'periosteum' is found on the outside of bone. This is a dense fibrous layer, where muscles insert. It contains bone forming cells.
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