Osteology
Osteology is the scientific study of bones, knowing characteristics of bones help us to understand musculoskeletal system better. The shape and classification of bones, the structure of bones, the chemical and physical properties of bones are the main subjects covered in this chapter.
functions of bone and the skeletal system
Support: besides your muscles you need bones to strengthen the musculoskeletal systems. The skeleton serves as the structural framework for the body by supporting soft tissues and providing attachment points for the tendons of most skeletal muscles.
Protection: There are many important organs beneath the ribs of thorax, imagine you had no ribs that support your muscles and tissues, what would happen?! in your thoracic cavity there are few important organs including heart and lungs which need protection from environmental traumas which might happen every seconds. skeleton protects the most important internal organs from injury. For example, cranial bones protect the brain, vertebrae (backbones) protect the spinal cord, and the rib cage protects the heart and lungs.
movement: with the help of skeletons you can easily move your limbs and in general your entire body, most skeletal muscles attach to bones; when they contract, they pull on bones to produce movement.
storage and release minerals: Bone tissue stores a number of minerals, mainly calcium and phosphorus, which contribute to bone strength. Bone tissue stores about 99% of the body’s calcium. When necessary, bone marrow permit release of minerals into the blood to maintain critical balance (homeostasis) and to distribute minerals to other parts of the body.
Blood cell production: In some bones, connective tissue called red bone marrow produces red blood cells, white blood cells, and platelets, a process called hemopoiesis. The red bone marrow contains growing blood cells, adipocytes, fibroblasts, and macrophages within a network of direct fibers. It is found in the development of fetal bones and other adult bones, such as the pelvic bones, ribs, sternum (chest bone), vertebrae (backbones), skull, and humerus bone (arm bone). and femur (thigh bone). In the newborn, the entire bone marrow is red and is involved in hemopoiesis. As the newborn grows, the bone marrow changes color to red.
Triglyceride storage: The yellow bone marrow contains mainly adipose cells, which store triglycerides. Stored triglycerides act as storehouse of chemical energy.
The shape and classification of bones
There are four types of bones in the skeleton: flat, long, short, irregular.
Long bone
A long bone is one that has greater length than width.
the typical long bone has following characteristics: one body (shaft), two ends (extremities)(epiphyses), medullary cavity, bone marrow, articular cartilage, periosteum.
long bones including: bones in the lower limbs (the tibia, fibula, femur, metatarsals, and phalanges) and bones in the upper limbs (the humerus, radius, ulna, metacarpals, and phalanges).
figure 1. long bone (humerus bone)
Short bones
cuboid, composed of spongy substance with a thin layer of compact substance. Such as carpal bones (scaphoid, lunate, triquetral, hamate, pisiform, capitate, trapezoid, and trapezium), bones of the wrist and ankle (calcaneus, talus, navicular, cuboid, lateral cuneiform, intermediate cuneiform, and medial cuneiform).
figure 2. short bones (carpal bones)
flat bones
The function of flat bones is to protect internal organs such as the brain, heart, and pelvic organs. examples are skull (occipital, parietal, frontal, nasal, lacrimal, and vomer), the thoracic cage (sternum and ribs), and the pelvis (ilium, ischium, and pubis).
figure 3. flat bone (frontal bone)
Irregular bone
some types of bones do not fit into any other classifications, these bones are called irregular bones which have complex, irregular shapes. example of irregular bones are vertebrae, hip bones, and several skull bones.
figure 4. irregular bone (T6 vertebra)
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