Study Sheet A

 

The Skeletal System

 

          The skeleton makes up the general framework of the body.  It is composed of 206 named bones of various shapes and sizes.  Strong bands of connective tissue called ligaments hold the bones together.  Between many of the bones there are pads of firm, smooth, slightly elastic connective tissue called cartilage.  The cartilage works to cushion the ends of the bones where they bump together at a joint.

          Bones are alive and continue to grow until about age 25.  They are hard due to the high concentration of certain minerals such as calcium and phosphorus.  All of the minerals, which the body needs for bone growth or repair, are found in food. 

          Why does the human body have a skeleton?  Here are the five important reasons: 

 

1.     To support the soft parts of the body.  Without your skeleton, your body would fall to the ground.

2.     To help muscles move your body by providing places for muscles to attach, while acting as levers themselves.

3.     To provide protection for many of the vital organs of the body such as the brain, heart, and lungs.

4.     To provide essential minerals, especially calcium, to the body when necessary – such as during pregnancy.

5.     To supply the body with certain blood cells.  All red blood cells and some white blood cells are formed in the bone marrow.

 Questions

1.     How many bones does a skeleton contain?

2.     Name three vital organs protected by a skeleton (a.b.c. on your answer sheet)

3.     What is the connective tissue called that holds bones together?

4.     At approximately what age do bones stop growing?

5.     What material cushions the ends of the bones, usually at a joint?

 

Study Sheet B

 

The Skeletal System – The Skull

      

The human skull can be divided into two regions:  the cranium, which contains the brain, and the bones of the face that protect the eyes, nose, ears, and mouth.
          The cranium consists of eight broad thin bones forming a dome-shaped structure.  The soft brain lies beneath this structure.  The eight bones include: a single frontal bone which forms the forehead, the occipital bone which forms the back of the skull, two parietal bones on the top of the skull, two temporal bones located in the temple area above the ears, and two sphenoid bones behind the eyes.

The wavy lines in the cranium are called sutures.  They mark the areas where bones are joined in the skull.  The bones of the cranium are not fused together in newborn babies, thus allowing for the skull and brain to grow.  In an adult, however, they form immovable joints.

There are fourteen bones that make up the face of the skull.  We can feel and see the outline of only a few of these bones.  These bones include the zygomatic, or cheekbones, the nasal bones of the bridge of the nose, the maxilla or upper jaw, and the lower jaw called the mandible.


Questions

1.     What is the top region of the skull called?

2.     What is the name of the lower jaw?

3.     How many bones does your entire skull contain?

4.     What does your cranium protect?

5.     What is the name given to the joints between two bones in the cranium?

 

Study Sheet C


The Skeletal System – The Spinal Column

 

          The spinal column or backbone is the central support of the body.  It consists of a flexible column of bones or vertebrae, which are stacked on top of each other like blocks.  The first seven (7) vertebrae for the next region are called cervical vertebrae.  The next twelve (12) vertebrae each have a pair of ribs attached to them and are called thoracic vertebrae.  The next five (5) vertebrae form the lower back and are called lumbar vertebrae.  The next five (5) vertebrae are fused into one bone called the sacrum.  The hipbones, or pelvis, attach to the sacrum.  The last four (4) vertebrae are also fused into one bone called the coccyx, or tailbone.  There are thirty-three vertebrae in all.  Only twenty-four of these, however, are true or moveable vertebrae.  The remaining nine are fused into the two fixed (nonmoving) bones at the base of the spinal column.

          Between the individual vertebrae are small discs of cartilage, which serve as shock absorbers.  In the center of each vertebrae is a vertical hole.  These holes all line up to form a long canal.  Located in the canal is the spinal cord, which conveys nerve messages up and down the body.

 

Questions

1.     How many individual bones do you find in your spinal column?

2.     What is a single backbone called?

3.     What are the shock absorber pads found between the vertebrae made of?

4.     To what region of the vertebral column do the hips attach?

5.     What type of vertebrae have ribs attached to them?

 

Study Sheet D


The Skeletal System – The Chest or Rib Cage

 

          The chest is formed by twelve pairs of ribs attached to the spinal column at the back and to the sternum, or breastbone, in the front.  The sternum is a single, dagger-shaped bone divided into three general regions.  The lower tip of the sternum is known as the xyphoid process.  The sternum supports the chest wall and serves as an attachment for numerous muscles.

          The connection of the ribs to the sternum is made by cartilage.  The cartilage gives the rib cage the flexibility it needs to expand during inhalation (breathing).  The top seven pairs of ribs are called true ribs since they connect directly to the sternum.  The bottom five pairs of ribs are called false ribs since they do not connect directly to the sternum.  The bottom two pairs of ribs, called floating ribs, do not attach in the front.

          The arms are attached to the skeleton at the shoulder girdle or pectoral girdle.  It is called a girdle because the bones make a sort of ring around the body.  The ring or girdle consists of the two clavicles, or collarbones, in the front and the two shoulder blades, called scapulas, in the back.  The legs attach to the skeleton at the pelvic girdle formed by the two pelvic bones.

 

Questions

1.     How many pairs of ribs does a human normally have?

2.     How many pairs of ribs are called “true” ribs?

3.     What are the bottom two pairs of ribs called?

4.     What is the proper name of the breastbone?

5.     The shoulder girdle is also called the ___________ girdle.

 

Study Sheet E


The Skeletal System – The Arms and Legs

 

          The arm is divided into three general regions.  The first region is the upper arm. It consists of a single bone called the humerus.  The second region is the lower arm.  It consists of two bones, the radius and the ulna.  The radius is nearest the thumb and rotates around the ulna making a small circle whenever the hand is turned over.  The ulna does not rotate.  The third region, called the hand, is divided into the wrist, palm, and fingers.  The wrist is composed of eight small bones called carpals, roughly arranged in two rows.  The palm is made of five long bones called metacarpals.  The fingers are called phalanges.  Each finger consists of three phalanges except the thumb, which only has two phalanges.

          The leg compares very closely with the arm.  The upper leg has one bone.  It is called the femur.  The femur is the longest and strongest bone in the skeleton and attaches to the hip or pelvic bone.  There are two bones in the lower leg, a large shinbone called the tibia, and a smaller bone called the fibula.  The foot is divided into the ankle, sole, and toes.  The ankle contains only seven bones instead of eight as in the wrist.  They are called the tarsals.  The sole of the foot consists of five long bones, the metatarsals.  The toes are the same as fingers, called phalanges.  One bone is found in the leg that does not have a counterpart in the arm.  It is the kneecap or patella.

 

Questions

1.     What bone is found in the leg without a counterpart in the arm?

2.     How many bones are located in the wrist?

3.     What is the longest bone in the skeleton?

4.     Which lower arm bone is capable of rotation?

5.     What is the name for fingers and toes?

 

Study Sheet F


The Skeletal System – Joints

 

          The joint is the place where two bones meet.  There are two types of joints:  movable joints and immovable joints.  Immovable joints do not permit any movement of the bones.  The suture joints of the skull and the fused bones of the sacrum and coccyx are examples of this type of joint.

          There are several types of movable joints based on the type of movement the joint permits.  Hinge joints, such as those found in knee and elbow, permit back and forth motion in only one direction.  The hip and shoulder joints are classified as ball-and-socket joints.  They permit nearly a full range of motion.  The joint at the base of the skull is called a pivot joint.  It allows movement of the head in a circular motion.  The joints of the wrist and ankle are classified as gliding joints.  The many small bones found in the wrist and ankle move slightly over one another permitting movement to occur.

 

Questions

1.     The place where two bones meet is called a _________________.

2.     What are the two types of joints (a. and b.)?

3.     What type of movable joint is most like the movement of a door?

4.     What type of joint is at the base of the skull?

5.     What type of movable joint permits the greatest variety of motion?