Appendicular Skeleton. Joints and Ligaments. Skeletal System Pathologies. When you select "Subscribe" you will start receiving our email newsletter. Use the links at the bottom of any email to manage the type of emails you receive or to unsubscribe.
See our privacy policy for additional details. Learn Site. So, what are the different types of bones? How are they categorized? There are five types of bones in the skeleton: flat, long, short, irregular, and sesamoid. Flat Bones Protect Internal Organs There are flat bones in the skull occipital, parietal, frontal, nasal, lacrimal, and vomer , the thoracic cage sternum and ribs , and the pelvis ilium, ischium, and pubis.
Flat bones serve as points of attachment for muscles and often protect internal organs. An irregular bone is one that does not have any easily characterized shape and therefore does not fit any other classification. These bones tend to have more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces. Many facial bones, particularly the ones containing sinuses, are classified as irregular bones.
A sesamoid bone is a small, round bone that, as the name suggests, is shaped like a sesame seed. These bones form in tendons the sheaths of tissue that connect bones to muscles where a great deal of pressure is generated in a joint. The sesamoid bones protect tendons by helping them overcome compressive forces.
Sesamoid bones vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees.
Table 6. Bone tissue osseous tissue differs greatly from other tissues in the body. Bone is hard and many of its functions depend on that characteristic hardness. Later discussions in this chapter will show that bone is also dynamic in that its shape adjusts to accommodate stresses. This section will examine the gross anatomy of bone first and then move on to its histology. The structure of a long bone allows for the best visualization of all of the parts of a bone Figure 6.
A long bone has two parts: the diaphysis and the epiphysis. The diaphysis is the tubular shaft that runs between the proximal and distal ends of the bone. The hollow region in the diaphysis is called the medullary cavity , which is filled with yellow marrow.
The walls of the diaphysis are composed of dense and hard compact bone. Red marrow fills the spaces in the spongy bone. Each epiphysis meets the diaphysis at the metaphysis, the narrow area that contains the epiphyseal plate growth plate , a layer of hyaline transparent cartilage in a growing bone.
Long bones, such as the femur, are longer than they are wide. Short bones, such as the carpals, are approximately equal in length, width, and thickness. Flat bones are thin, but are often curved, such as the ribs. Irregular bones such as those of the face have no characteristic shape. Sesamoid bones, such as the patellae, are small and round, and are located in tendons. What are the structural and functional differences between a tarsal and a metatarsal? Structurally, a tarsal is a short bone, meaning its length, width, and thickness are about equal, while a metatarsal is a long bone whose length is greater than its width.
Functionally, the tarsal provides limited motion, while the metatarsal acts as a lever. What are the structural and functional differences between the femur and the patella? Structurally, the femur is a long bone, meaning its length is greater than its width, while the patella, a sesamoid bone, is small and round.
Functionally, the femur acts as a lever, while the patella protects the patellar tendon from compressive forces. With the exception of the thumb, each digit contains a proximal, intermediate, and distal phalange; the thumb lacks an intermediate phalange.
The length of the phalanges decreases distally. Human hand bones : Fingers are made up of proximal, intermediate, and distal phalanges. The thumb lacks an intermediate phalange. Learning Objectives Describe the types of bones in the hand.
Key Points There are eight carpal bones in each wrist. There are five metacarpal bones in each hand. There are proximal, intermediate, and distal phalanges in each digit except for the thumb, which lacks an intermediate phalange. Key Terms metacarpal : Any of the bones of the palm.
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