Main bones, joints and muscles of the bodyFrom the moment you open your eyes in the morning until you go to bed, you move around. Even during sleep you may fret, twist, and turn. Every movement that you do, no matter how inconspicuous, consists of a complex series of events with an equally complex anatomy behind the scenes.
This flexible and movable scaffold is provided by the musculoskeletal system. It is composed of three major structures: bones, joints, and muscles. On this page we’ll learn about each of them individually, but also how they all work together as a system to help you accomplish your daily tasks.
Axial skeleton: bones of the skull, ribs, vertebral column, sternum, sacrum, coccyx, hyoid bone and auditory ossicles.
Appendicular skeleton: bones of the upper and lower limbs and the shoulder and pelvic girdles
|Main joints||Skull sutures, temporomandibular, shoulder, elbow, wrist, hip, knee, and ankle joints|
Head: Muscles of facial expression, muscles of mastication
Neck: Suprahyoid and infrahyoid muscles, scalenes, platysma
Trunk: Pectoral, intercostal, anterior abdominal, lateral abdominal, posterior trunk muscles
Upper limb: Shoulder, arm, forearm, and hand muscles
Lower limb: Gluteal, hip, thigh, leg, and foot muscles
Main bones of the skeletal system
We’ll begin by looking at the skeletal system. As the name implies, the structural and functional unit is bone–a highly specialized and hard connective tissue. Bones can be classified according to two major criteria, yielding different types of bones:
- Compact and spongy bone (according to strength)
- Long, short, flat, irregular, and sesamoid (according to shape)
Each type has unique features and functions, facilitating their differentiation. If you want to learn more about the various types of bones in the body, take a look below.
The basic structure of a bone consists of a thin, superficial layer of compact bone overlying the bone marrow cavity composed of spongy bone. Since bone is a living tissue, it requires a neurovasculature supply. Arterial blood is provided by the nutrient, periosteal, metaphyseal, and epiphyseal arteries. Innervation reaches bones via periosteal nerves–these are the culprits for the sensation of pain during bone fractures.
We’ve covered the structure of the functional and structural unit of the skeletal system. Let’s continue and look at the entire system as a whole. Skeletal system function is diverse, ranging from protection and support to mineral storage and production of new blood cells.
You already know that a large number of bones exists but how many bones are in the human body exactly? Generally speaking, there are 206 in an adult but the definite number is more nuanced and can vary from person to person. These bones are mainly divided into two parts, called axial and appendicular skeletons. Here’s a skeletal system diagram providing you with a broad overview of the two skeletons and the bones in the body:
The axial skeleton is essentially the midline, or central core region, and consists of the bones of the skull (cranium) together with the bones of the trunk. The skull can be further divided into the neurocranium (cranial bones) and viscerocranium (facial bones). In turn, the trunk is composed of several bones like the ribs, vertebral column, sternum, sacrum, coccyx, as well as the hyoid bone and auditory ossicles.
The appendicular skeleton includes the attached appendages or bones of the upper and lower limbs and the shoulder and pelvic girdles as well. It is essentially all bones that hang off of the axial skeleton.
|Shoulder girdle||Clavicle and scapula|
|Upper limb||Humerus, radius, ulna, carpals, metacarpals, and phalanges|
|Pelvic girdle||Pelvic bones (ilium, ischium, pubis)|
|Lower limb||Femur, patella, tibia, fibula, tarsals, metatarsals, and phalanges|
Everything can feel daunting when it comes to human anatomy, including bones. However, you can simplify your learning by watching the following overview video of the skeletal system. At the end, tackle our bones of the body quiz to cement your knowledge!
Main joints of the body
The second component of the musculoskeletal system are the joints. If bones provide the framework, the joints provide the flexibility by permitting movement. A joint, or articulation, is the junction between two or more bones. There are three main types: fibrous, cartilaginous, and synovial. The latter allows the greatest freedom of movement and are the most well known in anatomy. There are several types of synovial joints:
- Ball and socket
Joints are supplied by articular vessels and nerves. If you want to build an overall picture of the main joints of the human body, here are some resources.
There are many joints in the entire human body, usually named according to the bones forming them. However, there are several major joints that are more complex than the rest and are extremely important in anatomy. These are the skull sutures, temporomandibular, shoulder, elbow, wrist, hip, knee, and ankle joints. They are reinforced by ligaments for extra support.
Main muscles of the muscular system
Let’s move to the third and final part of the musculoskeletal system. Muscles are the contractile apparatus attached to bones that pull them in various directions, ultimately creating movement. In addition to this, the muscular system function includes heat generation as well. Like bones, muscles can be classified according to several criteria:
- Smooth, cardiac, or skeletal (according to location and histology)
- Pennate, fusiform, parallel, convergent, circular, or digastric (according to shape)
Skeletal muscle is mainly involved in moving bones and the type of muscle typically referred to in anatomy when referring to the musculoskeletal system. Muscles are attached to bones via tendons or aponeuroses and receive a rich nerve supply to allow precise movement control.
The structural unit of a muscle is the muscle fiber, while the functional unit is a motor unit. Skeletal muscles mostly act in antagonism, meaning that when one contracts to create the movement (agonist), the corresponding opposite one relaxes (antagonist). Muscles working as antagonistic pairs are responsible for creating a smooth movement.
There are hundreds of muscles in total, so it wouldn’t be logical to look at all of them in this page. Instead, learn the most important ones by grouping them according to anatomical region:
|Muscles of the head||Muscles of facial expression, muscles of mastication (temporal, masseter, pterygoids)|
|Muscles of the neck||Suprahyoid and infrahyoid muscles, scalenes, platysma|
|Muscles of the trunk||Pectoral, intercostal, anterior abdominal, lateral abdominal, and posterior trunk muscles|
|Muscles of the upper extremity||Shoulder, arm, forearm, and hand muscles|
|Muscles of the lower extremity||Gluteal, hip, thigh, leg, and foot muscles|
If you want to master the muscles of the body, check out the following study units, and watch the integrated overview videos about the muscles of each region and complete the associated quizzes! We also have a series of muscle anatomy charts that can help you drill the information into your brain once and for all.