Skeletal System

Hey, guys! Welcome to this Mometrix video about the skeletal system.

Every one of the systems in the body plays a critical role in our ability to function, but the skeletal system is particularly important. Without a skeletal system we wouldn’t be able to walk, and we would have no way to protect our vital organs like our heart
and brain. That’s why the skeletal system and its network of 206 bones are so important to us.

Skeletal System Functions

So let’s talk about the skeletal system’s main functions. There are six of them, and they’re all important.

Support

The skeletal system supports our bodies and the organs and tissues within it. Our skeleton gives us shape and holds us up, so without a skeletal system, we couldn’t stand.

Movement

The skeletal system gives us the ability to move. The bones allow movement by acting like a kind of pulley. When muscles contract, they pull the skeletal bones, which cause movement. Joints also play a critical part in movement because they determine flexibility. So, while you can bend your knee up to a 135-degree angle, your back—the thoracic spine—only bends about 60 degrees, at most. The bottom line is this—you need muscles, bones, and joints to move and bend and stretch.

Protection

Our skeletons protect our organs. Our skull protects our brain. Our rib cage holds up and protects our lungs and heart. The spinal cord, well, that’s protected by the vertebrae.

Production of Blood Cells

And while those are some of the obvious ways our skeleton works for us, there are some less obvious ones. We need our skeletal system to produce blood cells. There’s a process called hematopoiesis that takes place in the skeletal system. That’s blood cell development, both red blood cells, which transport oxygen, and white blood cells, which fight infection. In other words, this is the process by which the body replenishes its blood system.

Mineral Storage

Not only that, the skeleton acts as a storage system for the minerals calcium and phosphorous, and we need both for our nerves, muscles, and body organs to function. This results in an interesting tug of war within our own body. You see, the skeleton needs calcium and phosphorous to stay strong while at the same time distributing these minerals to other parts of the body that need them as well. So, if the skeleton shares too much of its mineral base it can become weak and lead to bone problems.

Endocrine Regulation

Lastly, the skeletal system is the main cog in the endocrine regulation which means it plays a big role in regulating energy metabolism. This is a relatively recent finding since the research study wasn’t published until 2007. The study showed bones release osteocalcin, a protein hormone, that regulates insulin productivity and sensitivity.

Now that we know the skeletal system’s six main functions, let’s look at the two parts of the skeletal system.

Axial Skeleton

The axial skeleton has 80 bones made up of the skull, inner ear ossicles, hyoid bone, vertebral column, and the ribs and sternum, which is called the bony thorax. Taken together, this means that the axial skeleton protects our central nervous system. Let’s take a look at the axial skeleton in more detail.

The skull has 28 bones that protect our head and face and contains the cranial and facial bones. Each bone has its own function. Let’s start with the cranial bones.

Cranial Bones

The cranial bones include the parietal, the temporal, frontal, occipital, sphenoid, and ethmoid bones. The two parietal bones are the flat bones on each side of your head, located behind the frontal bone The temporal bones are located under the parietal bones. These two irregular shaped bones are at the base and sides of the skull and house the ear structures.

Then there’s the frontal bone. That’s your forehead, and it also contains the eye sockets. The occipital bone is located at the back of the skull and it has an opening at the bottom. It’s from that opening that the spinal cord connects to the brain. The sphenoid bone forms a large part of the base of your skull. The ethmoid bone, located in front of the sphenoid bone, forms a part of the nasal cavity.

Facial Bones

Now let’s look at the facial bones, which have their own unique functions. The facial bones include the maxilla, zygomatic, mandible, nasal, palatine, concha, lacrimal, and vomer bones.

The maxilla bone holds the upper teeth in place and forms the upper jaw. The zygomatic bone, despite the name, is an easy one to remember because it’s commonly referred to as the cheekbone. The bone also forms the outer side of the eye socket. The lower jaw bone, called the mandible bone, lets us open and close our mouth and chew since the bone houses our lower teeth.

The nasal bone is an easy one. It’s those two bones in the middle of our face that make up the bridge of our nose. The palatine bone, that’s an L-shaped bone that forms the nasal and oral cavities. The inferior nasal concha is a thin, spongy and bony plate that forms the lower part of the nasal cavity’s lateral wall. The lacrimal bone is a small and thin bone—actually, it’s the smallest and thinnest in the skull—and it forms part of the eye socket. And the vomer bone separates the left and right nasal cavity.

Vertibral Column

Let’s move on to the bones in our back. The vertebral column has 33 bones and we’ll describe them here.

The cervical vertebrae are the neck vertebrae that run right below the skull. The cervical spine contains seven vertebrae each designated C1 through C7. The first two vertebrae have more specialized functions, and each have their own name. The C1 vertebrae, called the atlas, connects to the occipital bone and supports the base of the skull. The C2 vertebrae, called the axis, allows the head to rotate. The C3, C4, C5, and C6 vertebrae all have the same characteristics, with a vertebral body, arch, and facet joints. The C7, at the bottom of the spine, connects with the top of the Thoracic spine.

Speaking of which, the thoracic spine has 12 vertebrae. Located in the upper back, the ribs connect to the thoracic spine and protect many of our vital organs and our spinal cord. The thoracic cage itself contains the ribs and the sternum.

The lumbar spine has 5 vertebrae (L1 to L5), located in the lower back, where the spine curves in towards the abdomen. The lumbar vertebrae support the weight of the entire torso and are most prone to injury.

The sacrum is a large bone made up of 5 fused vertebrae at the base of the spine and is part of the pelvic cavity, while the coccyx is made up of 4 small fused bones that can really, really hurt if you fall on it. Most people know it as the tailbone.

So that’s the axial skeleton.

Appendicular Skeleton

The appendicular skeleton has 126 bones that cover our arms, legs, hands, feet, our pelvic girdle, and our shoulder girdle. That means the appendicular skeleton governs movement. The appendicular skeleton can be subdivided into four areas.

Pectoral Girdle

The pectoral girdle covers the clavicle and scapula, which connect the upper extremities to the trunk. The clavicle is commonly known as the collarbone, and the scapula as the shoulder blade.

Upper Extremeties

The upper extremities (your arm) includes the humerus, radius, ulna, carpals, metacarpals, and phalanges.

Pelvic Girdle

The pelvic girdle, your hip bone, serves as the attachment mechanism for the lower limbs.

Lower Extremeties

The lower extremity, or your legs, cover the femur, tibia, fibula, patella, tarsals, metatarsals, and phalanges.

So as we can see, the skeletal system controls movement and protects our vital organs. Not only that, relatively new research shows how the skeletal system plays a role in regulating energy metabolism.

Now, let’s take a look at the bones that play such an important part in the skeletal system.

Bone Characteristics

We know that the skeletal system is made up of bones. But what exactly are bones, and what other functions do they have?

Bones are connective tissue, and some bones are more rigid than others. That’s why bones have two classifications.

Compact Bones

There are compact bones, which are dense and rigid and make up much of the skeleton’s hard structure. Compact bones are stronger. They support the body, protect vital organs, and are the engine that power movement. Compact bones also release calcium and phosphorus into the body when it needs it. The body’s long bones, like the tibia, femur, and fibula, are examples of compact bones.

Cancellous Bones

Cancellous bones are located within the compact bones. They’re softer and spongier, which is why these bones are often called spongy bone. What do they do? They control the production of red blood cells, and you’ll also find nerves and bone marrow in this spongy bone.

Both compact and spongy bone is found in most bones. Compact bone is the outer shell around spongy bone.

Bone Shapes

Bone also comes in different shapes, and each with its own purpose. The flat bones, like the sternum and cranium, protect organs. The long bones, like the femur and tibia, support weight. The cube-shaped short bones, like the carpals in your hand and tarsals in your ankle, provide stability. The irregular bones, like the ones of the vertebrae and pelvis, protect organs. Lastly, the sesamoid bones are small round bones embedded in tendons, such as the kneecap, which protect tendons from stress and wear.

Different Bone shapes

So that’s our overview of the skeletal system, the bones that help us walk, protect our internal organs, produce blood cells, and help with insulin productivity and sensitivity.

 

Return to Biology Videos

256447

 

by Mometrix Test Preparation | This Page Last Updated: February 21, 2022