Human Skeletal System – Human Skeleton Bones – and Functions of Skeletal System
Small Bones Will Fuse Together As We Grow Older
A fully grown up person, 25 years and above, has 206 bones and a newly born baby has no less than 270 bones. This happens because as we grow older a number of small bones will fuse together forming larger and stronger bones. The pelvis and the cranium (skull) bones are examples of bones that are fused. The skeleton of adult humans is therefore a structure made of fused bones and individual bones. The bones that make up the human skeletal system are joined up and supported by ligaments, tendons, cartilages and muscles.
1. Ligament also known as articular ligament is a tough, flexible, fibrous tissue that connects two bones to form a joint.
2. Tendon is a flexible (but inelastic) fibrous tissue that connects a muscle to a bone.
3. Cartilage is a gel-like tissue found at the ends of bones and acts as a cushion to prevent shock and friction between bones in a moving joint. Articular cartilage acts as the bones in embryo and converts to bone as humans grow.
4. Muscle is a fibrous tissue in a human body that can contract to produce and maintain movement of body parts. Muscles are able to contract and relax because their cells contain contractile filaments that move past each thus changing the sizes of the cells.
5. Joint also known as articulation is where two bones come together. There are three types of joints namely: immovable, slightly movable and freely movable.
Layers of Bone:
A bone is made up of three layers, namely:
1) Outside Skin of the Bone also known as periosteum
2) The Hard Compact Bone. This layersupports the weight of the body.
3) Bone Marrow, also known as spongy bone. Bone marrow in femur, sternum, and humerus bones produces red blood cells, white blood cells and platelets. There is also yellow marrow that is for storing fats.
Components of Bone
A bone has cells embedded in it. A bone is made up of organic ingredients like collagen and inorganic minerals ingredients. The inorganic mineral ingredients are calcium, phosphorus, magnesium, potassium, and sodium. Calcium and phosphorus provides hardness, strength, and rigidity to the bones whilst collagens are fibers that provide flexibility. The minerals magnesium, potassium and sodium acts as binders for calcium and phosphorous. Osteoclasts are bone-making and bone-destroying cells that maintain a balance between calcium in the bones and calcium in the blood. If you do not have sufficient calcium in your blood, osteoclasts cells will remove calcium from your bone and into blood and the result will be weak bones.
Functions of Skeletal System
The functions of the human skeletal system are as follows:
- Provides movement. Bones and joints powered by muscles and coordinated by nervous system provides movement of the body.
- Provides support. The skeleton is a structure which supports the body and maintains its shape.
- Provides protection to the body organs. For example: the skull protects the brain, the vertebrae protects the spinal cord, the rib cage protects the lungs and heart, the ilium protects the digestive system, etc.
- Provides storage. Bones stores calcium, bone marrow stores iron, and yellow marrow stores fats
- Produces blood cells. Bone marrow in femur, sternum, and humerus produces red blood cells, white blood cells, and platelets.
- Participates in regulation of blood sugar (glucose). In endocrine regulation, bone cells produces osteocalcin, and osteocalcin produces insulin which regulates blood sugar.
Classification of bones
Bones are classified in four principal types as follows:
- Long Bones. These are bones that are longer than they are wide. Examples include tibia bone, fibula bone, clavicle bone, humerus bone, radius bone, metatarsals bone, ulna bone, femur bones, etc
- Short Bones. These are bones whose vertical length and horizontal length are almost equal. Examples include the carpals and tarsals.
- Flat Bones. These are bones that are flat, thin, and usually curved. Example includes ribs and scapula.
- Irregular Bones: These are bones of irregular shapes and can not fit as long bones, short bones or flat bones. Examples include the skull, vertebrae and pelvis.
We have said that a fully grown up adult has 206 bones. The axial axis of a human skeleton has 80 bones and its called axial skeleton. The appendicular skeleton has 126 bones. Appendicular is to do with arms and legs.
Axial axis has the skull, ossicles, hyoid, rib cage, sternum and vertebral column, and these have the following bones:
1. The Skull, Ossicles and Hyoid
a) The Cranial Bones are: 2 parietal bones, 1 ethmoid bone, 2 temporal bones, 1 frontal bone, 1 occipital bone, and 1 sphenoid bone. Total for the cranial bones equals 8 bones.
b) The Facial Bones are: 2 maxilla bones, 2 zygomatic bones, 2 inferior nasal concha bones, 2 lacrimal bones, 1 mandible bone, 2 nasal bones, 2 platine bones, and 1 vomer bone. Total for facial bones equals 14 bones.
c) Auditory Ossicles bones are: 2 incus bones, 2 malleus bone, and 2 stapes bones. Total for Auditory Ossicles equals 6 bones.
d) Hyoid bone: 1 hyoid bone. The hyoid bone is the only bone of the throat. Hyoid bone anchors the tongue. Total for hyoid bone equals 1 bone.
Total bones for skull, ossicles and hyoid are equals to 29 bones.
2. The Vertebral Column:
a) The Vertebral Column bones are: 7 cervical vertebrae bones, 12 thoracic vertebrae bones, 5 lumbar vertebrae bones, 1 sacrum bone, and 1 coccyx bone
Total bones for the vertebral column are equals to 26 bones
3. The Rib Cage and Sternum:
a) The thoracic cage bones are: 24 ribs and 1 sternum bone.
Total bones for the thoracic cage equals 25 bones
Total bones for the Axial skeleton are equals to 29+26+25 equals 80 bones
The appendicular skeleton has the pectoral girdles, the upper limbs, the pelvic girdle and the lower limbs.
1. The Pectoral girdles
a) Pectoral girdles bones are: 2 clavicle bones and 2 scapula bones. Total bones for pectoral girdles equals 4 bones.
2. The Upper Limbs
a) Upper limbs bones are: 2 humerus, 16 Carpals, 10 metacarpals, 2 radius, 2 ulna, 28 phalanges. Total bones for the upper limbs equals 60 bones
3. The Pelvic girdle
a) Pelvic girdle bones are: 1 coxal and 1 innominate bone. These are the two hip bones. Total bones for the pelvic girdle equals 2 bones
4. The Lower limbs
a) Lower limbs bones are: 2 femur, 2 patella, 14 tarsals, 2 tibia, 2 fibula, 10 metatarsals, and 28 phalanges. Total bones for the Lower limbs equals 60 bones
Total bones for the appendicular skeleton are equals to 4+60+2+60 equals 126 bones
Total bones for the human skeletal system are equals to 80+126 equals 206 bones
Diagrams of Human Skeletal System
Below are the diagrams of human skeletal system.
Diagram of Human Skeletal System - Front View
Diagram of Human Skeletal System - Back View
Above are the diagrams of human skeletal system. Study them, and I hope the content of this article will provide its readers with a useful study in understanding the basics of human skeletal system.
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