The Skeletal System
Its 206 bones form a rigid framework to which the softer tissues and organs of the body are attached.
Vital organs are protected by the skeletal system. The brain is protected by the surrounding skull as the heart and lungs are encased by the sternum and rib cage.
Bodily movement is carried out by the interaction of the muscular and skeletal systems. For this reason, they are often grouped together as the musculo-skeletal system. Muscles are connected to bones by tendons. Bones are connected to each other by ligaments. Where bones meet one another is typically called a . Muscles which cause movement of a joint are connected to two different bones and contract to pull them together. An example would be the contraction of the biceps and a relaxation of the triceps. This produces a bend at the elbow. The contraction of the triceps and relaxation of the biceps produces the effect of straightening the arm.
Blood cells are produced by the marrow located in some bones. An average of 2.6 million red blood cells are produced each second by the bone marrow to replace those worn out and destroyed by the liver.
Bones serve as a storage area for minerals such as calcium and phosphorus. When an excess is present in the blood, buildup will occur within the bones. When the supply of these minerals within the blood is low, it will be withdrawn from the bones to replenish the supply.
This Skeletal system is located throughout the entire body. This system has many roles, one of the main ones being support of our structure. The Skeleton helps us maintain our shape and stand up straight. Without our skeleton we would be a big pile of nothing but skin organs and blood. The skeletal system also helps us breathe because when we take in a breath the ribs expand allowing us to take in the oxygen we need. When we exhale the ribs contract causing the air to be “pushed” out and the process continues over and over again. Our skeletal system is also there to help protect some organs. The rib cage protects the heart and lungs from injuries and shock that might damage them. The ribs also protect the stomach, spleen, kidneys, and give the chest its familiar shape. There are three different types of ribs, the true, false and floating all of which are connected to the spine. The ribs consist of 24 bones arranged in 12 pairs. The main purpose of the skull is protection of the brain. Skull is composed of 8 cranial and fourteen facial bones. The cranial bones make up the protective frame of bone around the brain. The facial bones make up the upper and lower jaw and facial structures.

The Skull

external image right1.gif

  • The **frontal** forms part of the cranial cavity as well as the forehead, the brow ridges and the nasal cavity.
  • The left and right **parietal** forms much of the superior and lateral portions of the cranium.
  • The left and right **temporal** form the lateral walls of the cranium as well as housing the external ear.
  • The **occipital** forms the posterior and inferior portions of the cranium. Many neck muscles attach here as this is the point of articulation with the neck.
  • The **sphenoid** forms part of the eye orbit and helps to form the floor of the cranium.
  • The **ethmoid** forms the medial portions of the orbits and the roof of the nasal cavity.
The joints between bones of the skull are immovable and called sutures. The parietal bones are joined by the sagittal suture. Where the parietal bones meet the frontal is referred to as the coronal suture. The parietals and the occipital meet at the lambdoidal suture. The suture between the parietals and the temporal bone is referred to as the squamous suture. These sites are the common location of fontanelles or "soft spots" on a baby’s head.
  • The **mandible** is the lower jawbone. It articulates with the temporal bones at the temporomandibular joints. This forms the only freely moveable joint in the head. It provides the chewing motion.
  • The left and right **maxilla** are the upper jaw bones. They form part of the nose, orbits, and roof of the mouth.
  • The left and right **palatine** form a portion of the nasal cavity and the posterior portion of the roof of the mouth.
  • The left and right **zygomatic** are the cheek bones. They form portions of the orbits as well.
  • The left and right **nasal** form the superior portion of the bridge of the nose.
  • The left and right **lacrimal** help to form the orbits.
  • The **vomer** forms part of the nasal septum (the divider between the nostrils).

+The upper extremity consists of three parts: the arm, the forearm, and the hand.
The Upper Extremities
The Upper Extremities
The arm, or
brachium, is technically only the region between the shoulder and elbow. It consists of a single long bone called the humerus. The humerus is the longest bone in the upper extremity. The top, or head, is large, smooth, and rounded and fits into the scapula in the shoulder. On the bottom of the humerus, are two depressions where the humerus connects to the ulna and radius of the forearm. The radius is connected on the side away from the body (lateral side) and the ulna is connected on the side towards the body (medial side) when standing in the anatomical position. Together, the humerus and the ulna make up the elbow. The bottom of the humerus protects the ulnar nerve and is commonly known as the "funny bone" because striking the elbow on a hard surface stimulates the ulnar nerve and produces a tingling sensation.
The forearm is the region between the elbow and the wrist. It is formed by the radius on the lateral side and the ulna on the medial side when the forearm is viewed in the anatomical position. The ulna is longer than the radius and connected more firmly to the humerus. The radius, however, contributes more to the movement of the wrist and hand than the ulna. When the hand is turned over so that the palm is facing downwards, the radius crosses over the ulna. The top of each bone connects to the humerus of the arm and the bottom of each connects to the bones of the hand.
The hand consists of three parts (the wrist, palm, and five fingers) and 27 bones.
The wrist, or carpus, consists of 8 small bones called the carpal bones that are tightly bound by ligaments. These bone are arranged in two rows of four bones each. The top row (the row closest to the forearm) from the lateral (thumb) side to the medial side contains the scaphoid, lunate, triquetral, and pisiform bones. The second row from lateral to medial contains the trapezium, trapezoid, capitate, and hamate. The scaphoid and lunate connect to the bottom of the radius.
The palm or metacarpus consists of five metacarpal bones, one aligned with each of the fingers. The metacarpal bones are not named but are numbered I to V starting with the thumb. The bases of the metacarpal bones are connected to the wrist bones and the heads are connected to the bones of the fingers. The heads of the metacarpals form the knuckles of a clenched fist.
The fingers are made up of 14 bones called phalanges. A single finger bone is called a phalanx. The phalanges are arranged in three rows. The first row (the closest to the metacarpals) is called the proximal row, the second row is the middle row, and the farthest row is called the distal row. Each finger has a proximal phalanx, a middle phalanx, and a distal phalanx, except the thumb (also called the pollex) which does not have a middle phalanx. The digits are also numbered I to V starting from the thumb.

sternum is a flat, dagger shaped bone located in the middle of the chest. Along with the **ribs**, the sternum forms the rib cage that protects the heart, lungs, and major blood vessels from damage.
The sternum is composed of three parts:

**manubrim**, also called the "handle", is located at the top of the sternum and moves slightly. It is connected to the first two ribs.
**body**, also called the "blade" or the "gladiolus", is located in the middle of the sternum and connects the third to seventh ribs directly and the eighth through tenth ribs indirectly.
**xiphoid process**, also called the "tip", is located on the bottom of the sternum. It is often cartilaginous (cartilage), but does become bony in later years.
These three segments of bone are usually fused in adults.
The sternum serves an important function in the body. The ribs are connected to it by the costal cartilage. Without the sternum, there would be a hole in the bone structure in the middle of your chest, right above your heart and lungs. The sternum protects this vital area and completes the circle of the rib cage.

+The vertebral column (also called the backbone, spine, or spinal column) consists of a series of 33 irregularly shaped bones, called vertebrae. These 33 bones are divided into five categories depending on where they are located in the backbone.
Vertebral column
Vertebral column
The first seven vertebrae are called the
**cervical vertebrae**. Located at the top of the spinal column, these bones form a flexible framework for the neck and support the head. The first cervical vertebrae is called the atlas and the second is called the axis. The atlas' shape allows the head to nod "yes" and the axis' shape allows the head to shake "no".
The next twelve vertebrae are called the
**thoracic vertebrae**. These bones move with the ribs to form the rear anchor of the **rib cage**. Thoracic vertebrae are larger than cervical vertebrae and increase in size from top to bottom.
After the thoracic vertebrae, come the
**lumbar vertebrae**. These five bones are the largest vertebrae in the spinal column. These vertebrae support most of the body's weight and are attached to many of the back muscles.
**sacrum**is a triangular bone located just below the lumbar vertebrae. It consists of four or five sacral vertebrae in a child, which become fused into a single bone after age 26. The sacrum forms the back wall of the pelvic girdle and moves with it.
The bottom of the spinal column is called the
**coccyx** or tailbone. It consists of 3-5 bones that are fused together in an adult. Many muscles connect to the coccyx.
These bones compose the vertebral column, resulting in a total of 26 movable parts in an adult. In between the vertebrae are intervertebral discs made of fibrous cartilage that act as shock absorbers and allow the back to move. As a person ages, these discs compress and shrink, resulting in a distinct loss of height (generally between 0.5 and 2.0cm) between the ages of 50 and 55.
When looked at from the side, the spine forms four
**curves**. These curves are called the cervical, thoracic, lumbar, and pelvic curves. The cervical curve is located at the top of the spine and is composed of cervical vertebrae. Next come the thoracic and lumbar curves composed of thoracic and lumbar vertebrae respectively. The final curve called the pelvic or sacral curve is formed by the sacrum and coccyx. These curves allow human beings to stand upright and help to maintain the balance of the upper body. The cervical and lumbar curves are not present in an infant. The cervical curves forms around the age of 3 months when an infant begins to hold its head up and the lumbar curve develops when a child begins to walk.
In addition to allowing humans to stand upright and maintain their balance, the vertebral column serves several other important functions. It helps to support the head and arms, while permitting freedom of movement. It also provides attachment for many muscles, the ribs, and some of the organs and protects the spinal cord, which controls most bodily functions.

-The lower extremity is composed of the bones of the thigh, leg, foot, and the patella (commonly known as the kneecap).
Lower Extremity
Lower Extremity
**The Thigh**
The thigh is the region between the hip and the knee and is composed of a single bone called the femur or thighbone. The femur is the longest, largest, and strongest bone in the body.
**The Leg**
The leg is technically only the region from the knee to the ankle. It is formed by the fibula on side away from the body (lateral side) and the tibia, also called the shin bone, on the side nearest the body (medial side). The tibia connects to the femur to form the knee joint and with the talus, a foot bone, to allow the ankle to flex and extend. The tibia is larger than the fibula because it bears most of the weight, while the fibula serves as an area for muscle attachment.
**The Foot**
The foot, or pes, contains the 26 bones of the ankle, instep, and the five toes. The ankle, or tarsus, is composed of the 7 tarsal bones which correspond to the carpals in the wrist. The largest tarsal bone is called the calcaneus or heel bone. The talus rests on top of the calcaneus and is connected to the tibia. Directly in front of the talus is the navicular bone. The remaining bones from medial to lateral are the medial, intermediate, the lateral cuneiform bones, and the cuboid bone.
The metatarsal and phalanges bones of the foot are similar in number and position to the metacarpal and phalanges bones of the hand. The five metatarsal bones are numbered I to V starting on the medial side with the big toe. The first metatarsal bone is larger than the others because it plays a major role in supporting the body's weight. The 14 phalanges of the foot, as with the hand, are arranged in a proximal row, a middle row, and a distal row, with the big toe, or hallux, having only a proximal and distal phalanx.
The foot's two arches are formed by the structure and arrangement of the bones and are maintained by tendons and ligaments. The arches give when weight is placed on the foot and spring back when the weight is lifted off of the foot. The arches may fall due to a weakening of the ligaments and tendons in the foot.

**The Patella**
The patella or kneecap is a large, triangular sesamoid bone between the femur and the tibia. It is formed in response to the strain in the tendon that forms the knee. The patella protects the knee joint and strengthens the tendon that forms the knee.
The bones of the lower extremities are the heaviest, largest, and strongest bones in the body because they must bear the entire weight of the body when a person is standing in the upright position.

+The Shoulder Girdle, also called the Pectoral Girdle, is composed of four bones: two clavicles and two scapulae .
Shoulder Girdle
Shoulder Girdle
**clavicle**, commonly called the collarbone, is a slender S-shaped bone that connects the upper arm to the trunk of the body and holds the shoulder joint away from the body to allow for greater freedom of movement. One end of the clavicle is connected to the sternum and one end is connected to the scapula.
**scapula**is a large, triangular, flat bone on the back side of the rib cage commonly called the shoulder blade. It overlays the second through seventh rib and serves as an attachment for several muscles. It has a shallow depression called the glenoid cavity that the head of the humerus (upper arm bone) fits into.
Usually, a "girdle" refers to something that encircles or is a complete ring. However, the shoulder girdle is an incomplete ring. In the front, the clavicles are separated by the
**sternum**. In the back, there is a gap between the two scapulae.
The primary function of the pectoral girdle is to provide an attachment point for the numerous muscles that allow the shoulder and elbow joints to move. It also provides the connection between the upper extremities (the arms) and the axial skeleton.

-The Pelvic Girdle, also called the hip girdle, is composed to two coxal (hip) bones. The coxal bones are also called the ossa coxae or innominate bones. During childhood, each coxal bone consists of three separate parts: the ilium (denoted in purple above), the ischium (denoted in red above), and the pubis (denoted in blue above). In an adult, these three bones are firmly fused into a single bone. In the picture above, the coxal bone on the left side has been divided into its component pieces while the right side has been preserved.
Pelvic Girdle
Pelvic Girdle
In the back, these two bones meet on either side of the
**sacrum**. In the front, they are connected by a muscle called the pubic symphysis (denoted in green above).
The pelvic girdle serves several important functions in the body. It supports the weight of the body from the
**vertebral column**. It also protects and supports the lower organs, including the urinary bladder, the reproductive organs, and the developing fetus in a pregnant woman.
The pelvic girdle differs between men and woman. In a man, the pelvis is more massive and the iliac crests are closer together. In a woman, the pelvis is more delicate and the iliac crests are farther apart. These differences reflect the woman's role in pregnancy and delivery of children. When a child is born, it must pass through its mother's pelvis. If the opening is too small, a cesarean section may be necessary.


Types of Bone

The bones of the body fall into four general categories: long bones, short bones, flat bones, and irregular bones. Long bones are longer than they are wide and work as levers. The bones of the upper and lower extremities (ex. humerus, tibia, femur, ulna, metacarpals, etc.) are of this type. Short bones are short, cube-shaped, and found in the wrists and ankles. Flat bones have broad surfaces for protection of organs and attachment of muscles (ex. ribs, cranial bones, bones of shoulder girdle). Irregular bones are all others that do not fall into the previous categories. They have varied shapes, sizes, and surfaces features and include the bones of the vertebrae and a few in the skull.
Bone Composition
Bones are composed of tissue that may take one of two forms. Compact or dense bone, and spongy, or cancellous, bone. Most bones contain both types. Compact bone is dense, hard, and forms the protective exterior portion of all bones. Spongy bone is inside the compact bone and is very porous (full of tiny holes). Spongy bone occurs in most bones. The bone tissue is composed of several types of
**bone cells**embedded in a web of inorganic salts (mostly calcium and phosphorus) to give the bone strength, and collagenous fibers and ground substance to give the bone flexibility
Types of Joints
A joint, or articulation, is the place where two bones come together. There are three types of joints classified by the amount of movement they allow: immovable, slightly movable, and freely movable.
Immovable joints are synarthroses. In this type of joint, the bones are in very close contact and are separated only by a thin layer of fibrous connective tissue. An example of a synarthrosis is the suture in the skull between skull bones.
Slightly movable joints are called amphiarthroses. This type of joint is characterized by bones that are connected by hyaline cartilage (fibro cartilage). The ribs that connect to the sternum are an example of an amphiarthrosis joint.
Most of the joints in the adult human body are freely movable joints. This type of joint is called a diarthrosis joint. There are six types of diarthroses joints. These are:
Ball-and-Socket: The ball-shaped end of one bone fits into a cup shaped socket on the other bone allowing the widest range of motion including rotation. Examples include the shoulder and hip.
Condyloid: Oval shaped condyle fits into elliptical cavity of another allowing angular motion but not rotation. This occurs between the metacarpals (bones in the palm of the hand) and phalanges (fingers) and between the metatarsals (foot bones excluding heel) and phalanges (toes).
Saddle: This type of joint occurs when the touching surfaces of two bones have both concave and convex regions with the shapes of the two bones complementing one other and allowing a wide range of movement. The only saddle joint in the body is in the thumb.
Pivot: Rounded or conical surfaces of one bone fit into a ring of one or tendon allowing rotation. An example is the joint between the axis and atlas in the neck.
Hinge: A convex projection on one bone fits into a concave depression in another permitting only flexion and extension as in the elbow joints.
Gliding: Flat or slightly flat surfaces move against each other allowing sliding or twisting without any circular movement. This happens in the carpals in the wrist and the tarsals in the ankle.
How can people make sure their body system remains healthy?
1. Eat a lot of foods high in calcium:1000 to 1200 mg a day. Bones depend on calcium for strength. Dairy products such as milk and cheese are an excellent source, as are leafy vegetables such as broccoli. Certain foods such as orange juice and breakfast cereals may be fortified with calcium as well; they are labeled as such on the container. If you're lactose intolerant or don't include calcium-rich foods in your diet, consider taking calcium supplements.
2. Step 2
Look for foods high in Vitamin D. It helps the bones absorb calcium more readily, which improves their strength. Most types of milk sold today contain Vitamin D, as does tuna fish, salmon, egg yolks and cod liver oil.

3. Step 3
Exercise. Physical activity promotes strong bones, especially weight-bearing
exercises which help strengthen bones against the effects of gravity. Besides weightlifting and weight training, weight-bearing exercises include more moderate physical activities like running, hiking, jumping rope, and playing in organized sports like soccer, basketball and tennis. Doctors suggest at least 30 minutes of exercise per day, 5 days a week.
4. Step 4
Wear helmets and other protective gear when you exercise. Broken bones never heal back quite as strong as they used to be. Help cut down on the risk with pads, helmets and mouth guards. This is especially important if you play a contact sport like football or rugby.

5. Step 5
Brush and floss your teeth twice a day. Your teeth are among the most important parts of your skeletal system; if they aren't properly cared for, they will develop cavities and similar problems. Brush regularly after meals and see your dentist twice each year for a cleaning.

Problems With Skeletal System
Osteoporosis can make your bones weak and more likely to break.
Osteogenesis Imperfecta makes your bones brittle which would be easier to break.
Paget’s Disease of bone makes your bones weak.

Bone Cancer- Cancer that starts in a bone is rare. Cancer that has spread to the bone from another part of the body is more common.
There are three types of bone cancer:

  • Osteosarcoma - develops in growing bones, usually between ages 10 and 25
  • Chondrosarcoma - starts in cartilage, usually after age 50
  • Ewing's sarcoma - begins in nerve tissue in bone marrow of young people, often after treatment of another condition with radiation or chemotherapy
The most common symptom of bone cancer is pain. Other symptoms may vary depending on the location and size of the cancer. Surgery is often the main treatment for bone cancer. Other treatments may include amputation, chemotherapy and radiation.
Many other bone diseases can be cause by poor nutrition, genetic factors, or with the rate of bone growth or rebuilding.
What would happen to an individual if something went wrong with this system?
Depending on what goes wrong there are various outcomes. If a person gets paget’s disease then their bones become weak and are easier to break. If a person has weak bones, which is all the less protection they have against certain organs such as the heart. If the ribcage becomes weak and a person gets into some type of accident and the bones break easier then the organs have a higher risk of being damaged.

Most definitely a person would not be able to survive without the skeletal system. If we had no bones for our support, we would just be a blob of skin organs and blood on the ground, unable to move. There is pretty much no way that we would be able to function because human beings have to be able to move around in order to get food or water. Without bones there would be no muscles so we would be very weak and unable to do pretty much anything. It would most likely be harder for us to breathe as well because the ribcage wouldn’t be there to help push out air and expand to take in oxygen.
Works Cited=