Rod Brouhard is one emergency clinical technician paramedic (EMT-P), journalist, educator, and also advocate for emergency medical business providers and also patients." data-inline-tooltip="true">Rod Brouhard, EMT-P

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lengthy Bones

The skeleton that the arms and legs are consisted of of mostly long bones. Long bones room so-called since they are much longer than they space wide. Lengthy bones in the arm incorporate the humerus, radius, ulna, metacarpals, and phalanges. Lengthy bones the the leg encompass the femur, tibia, fibula, metatarsals, and phalanges. The clavicles (collar bones) are likewise long bones.

You are watching: In newborn infants, the medullary cavity and all areas of spongy bone contain yellow bone marrow.

Long bones administer the leverage we need for moving our bodies and also for manipulating our environment. All lengthy bones have two key parts: diaphysis and also epiphysis.


The diaphysis is the shaft of the lengthy bone, the main body. The diaphysis is a tube through a hollow facility called the medullary cavity (or marrow cavity). The wall of the diaphysis is comprised of compact bone, which is thick and really hard. For most of the life the a long bone, the facility of the diaphysis is filled v yellow bone marrow. Yellow bone marrow is basically fat, additionally known as adipose tissue.


Each finish of a long bone is called an epiphysis. Each epiphysis is shame to fit its connecting bone at a junction the is called a joint and the shape of the epiphysis is based on the task of the joint. The proximal (closer come the body) epiphysis of the humerus and the proximal epiphysis of the femur space shaped in a rounded manner, referred to as the head, and also look a little like half of a ball. This shape permits those two lengthy bones to rotate in lot of directions. The head the the femur fits into a socket in the pelvis. The head the the humerus fits into a socket in the shoulder. That type of joint is referred to as a ball-and-socket joint. Joints that only enable movement along one axis are referred to as hinge joints.

The wall surface of the epiphysis is make of compact bone choose the diaphysis and the facility contains spongy bone. Spongy bone is make of many tiny cavities (also called medullary cavities) filled v red bone marrow. Red bone marrow manufactures red blood cells and also is really well associated to the circulatory system. Over there is so lot blood flow through the spongy bone, the needles put into the spongy bone of the humerus, of the femur, or that the sternum (not a long bone together you'll see below) deserve to be offered to administer fluid or medications similar to an intravenous line.

Epiphyseal plate

There is a line that have the right to be seen on pictures of the epiphysis and also is dubbed the epiphyseal plate. The is where brand-new bone is added to boost the length of the lengthy bone during breakthrough (called ossification). It is typically known together the development plate. Fractures (breaks and cracks in the bone) that incorporate the epiphyseal plate have the right to interrupt proper bone development in kids.

quick Bones

Short skeleton are referred to as that since they about as wide as they space long. There is no diaphysis on a short bone. The is made up of spongy bone surrounding by compact bone just like the epiphysis. Brief bones also contain red bone marrow.

There are 32 brief bones in the person skeleton. Typically, brief bones facilitate movement and also strength in the facility joints the the wrist and ankles by sliding and shifting against each other.

The carpals (wrist bones), tarsals (ankle and heel bones), and the patella (kneecap) room all short bones. Part experts think about the patella a sesamoid bone (discussed below) due to the fact that it primarily provides an anchor suggest for tendons and ligaments. However, the patella is typical to everyone while sesamoid bones construct differently in between individual people.

level Bones

Flat bones room the armor the the body. Level bones carry out structure, such as the shape of the head and torso, and the foundation of the shoulder and hip. Level bones deserve to also carry out protection the soft organization underneath. Like quick bones, level bones have walls that space made that compact bone and also a center of spongy bone (with red bone marrow) that creates something like a sandwich.

The cranial bones, scapula (shoulder blade), sternum (breast bone), ribs, and also iliac bone (hip) are all flat bones. The these, the scapula, sternum, ribs, and iliac bone all provide strong insertion points for tendons and muscles.


The skeletal of the cranium room the component of the skull the encapsulates the brain. The skeletal of the cranium are connected together v joints referred to as sutures, which look favor they space stitched. Sometimes, additional little bones have the right to develop between sutured bones of the cranium follow me the suture lines. These small bones are dubbed sutural bones. They construct randomly and are not called bones.

Irregular skeletal

Bones that room neither long, short, nor level are considered irregular bones. The forms of this bones carry out very particular functions. The face bones and the bones of the spinal column, the vertebrae, are all irregular bones. These bones have facility shapes that are distinct to your function. Most of the irregular bones appear only as soon as in the body follow me the midline, such together each that the vertebrae. Some of the skeleton of the face appear in mirror image, such together the zygomatic skeleton (cheekbones).

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Irregular bones regularly have facility shapes the are provided as insertion points because that muscles, tendons, and ligaments. The most common shape is referred to as a process that looks prefer a protrusion. The vertebrae each have actually three processes: the spinous procedure along the posterior (back) in the center (midline), and transverse processes on either side of the spinous process.