THE MUSCULAR SYSTEM

THE MUSCULAR SYSTEM

-       composed of muscle cell and tissues held tightly together

-       there are more than 650 muscles in the body and more than 50 muscles in the face

PROPERTIES OF MUSCLE CELLS

1. Contractility – the ability of the muscle to become shorter and thicker
2. Extensibility – allows the muscles to stretch
3. Elasticity – enables them to return to their original form
4. Irritability -  contraction of muscles stimulated by several stimuli like heat, light, chemical pressure and electricity

HOW DO MUSCLES WORK?

Muscles work by tightening and loosening. Tightening is called contraction. Loosening is called relaxing. Your nerves tell muscles when to contract.

Suppose you see a cookie on a table. You want to pick up that cookie and eat it. Your brain sends out a signal. Nerves carry the signal from your brain to your arm and hand muscles. The signal tells muscles in your arm to contract. Your arm reaches out for the cookie. Then the signal tells muscles in your hand to contract and grab the cookie. Muscles in your arm contract to bring the cookie to your mouth. Your hand pops the cookie into your mouth. Your jaw muscles contract and relax so you can chew the cookie. 

• Muscles in the body work in pairs as flexors (biceps) and extensors (triceps). One bends or lifts the other straightens and extends
• Biceps (flexors) – it pulls up or lifts the lower arm
• Triceps (extensor) – it extends the arm

WHAT ARE MUSCLES MADE OF?

Muscles are bundles of thin strands called fibers. The muscle fibers are made of substances called proteins.

There are two types of muscle fibers. The two types are slow twitch and fast twitch. Your fast-twitch muscle fibers contract rapidly. These fibers give you bursts of power. When you suddenly jump or run fast while playing tag, your fast-twitch muscle fibers are hard at work.

Slow-twitch muscle fibers allow you to keep doing exercises. They give you endurance. When you run a long way, your slow-twitch muscle fibers are doing most of the work. Some kinds of muscle have both fast-twitch and slow-twitch fibers.

 

Functions of the Muscular System

1. muscle hold the skeletons together, they are joined to the bones
2. muscles cover and protect the bones of internal organs
3. skeletal muscles enable us to move
4. smooth muscles push the food through our digestive tract
5. cardiac muscles make our heart beat

KINDS OF MUSCLES

1. Skeletal muscles – attached to the bones and cause them to move

- also called striated muscles because they have stripes or striations

- also called voluntary muscles

- These muscles contract and relax to make your bones move. These are the kind of muscles you use to run or swim or reach for cookies

- This type of muscle is composed of long fibers surrounded by a membranous sheath, the sarcolemma. The fibers are elongated, sausage-shaped cells containing many nuclei and clearly display longitudinal and cross striations

- Most skeletal muscle is attached to portions of the skeleton by connective-tissue attachments called tendons.

- Contractions of skeletal muscle serve to move the various bones and cartilages of the skeleton. Skeletal muscle forms most of the underlying flesh of vertebrates.

2. Cardiac muscle – are much shorter and do not tire easily and do not have striations

- This muscle tissue composes most of the vertebrate heart. The cells, which show both longitudinal and imperfect cross striations, differ from skeletal muscle primarily in having centrally placed nuclei and in the branching and interconnecting of fibers.

- Cardiac muscle is not under voluntary control. It is supplied with nerves from the autonomic nervous system, but autonomic impulses merely speed or slow its action and are not responsible for the continuous rhythmic contraction characteristic of living cardiac muscle.

3. Smooth muscles – are composed of cells with single nucleus

- perform involuntary motions

- Visceral, or involuntary, muscle is composed of spindle-shaped cells, each having a central nucleus. The cells have no cross striations, although they do exhibit faint longitudinal striations.

- found in the skin, internal organs, reproductive system, major blood vessels, and excretory system.

Type	Description	Function	Examples
Skeletal	-       voluntary -       striated muscle	- moves bones	- arms and legs
Smooth	-       involuntary -       non-striated muscle -	-       forms part of the wall of the digestive, respiratory and circulatory system	- stomach and lungs
Cardiac	-       involuntary -       striated muscle	-       causes the heart to alternately contract and relax	- heart

THE SKELETAL SYSTEM

The Skeletal System

The Skeletal System serves many important functions; it provides the shape and form for our bodies in addition to supporting, protecting, allowing bodily movement, producing blood for the body, and storing minerals.

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.

Kinds of Skeleton 

 

1. Endoskeleton – the skeleton found inside the body of vertebrates
2. Exoskeleton – a hard external covering of some invertebrates that provides protection and support

Functions of the Skeletal System

1. provides the framework of the body (for support)
2. it determines our shape and size
3. protects the internal organs
4. provides body movement
5. the bone cells store and release important minerals. They are the body’s chief storage place for calcium

Composition of the Bone

The inside of the bone is made of three primal tissue layers: periosteum, compact bone, and spongy bone.

 

Periosteum

The periosteum is a glistening double layerd tissue which covers the hard bone are called the compaact bone. The periosteum can not be seen by the naked eye. The periosteum is exceedingly important since it's lower layer houses bone forming cells called osteoblast. Also, the double layer serves as a place where tendons and ligaments can insert and anchor into the bone.

Compact Bone

Compact bone seems very hard when seen by the normal eye, but at a microscopic level, the compact bone is very hollow. Canals called canaliculi, which are filled with blood vessels, channel through the bone and all join to many major canals called Haversian canals. These canals make the bone hollow. The compact bone is also rich with nerves. The hardness of the bone is made by spider like ostecytes, mature bone cells, which surround the caniculli and Heversian canals.

Spongy Bone

Spongy bone is not exactly spongy. Towards the center of the bone, the bone gets more hollow. This is why it is called spongy. Located within the spongy bone is red bone marrow nad yellow bone marrow. Red bone marrow is what makes red blood cells. The majority of the red boone marrow for an adult is located in the head of the femeur and hemerus. Yellow bone marrow is stored fat. This marrow can sometimes turn in to red bone marrow when a person is very anemic.
 

Types of Bones

       Long Bones – are those bones found on the legs and arms

     - they are hollow, yet strong and lightweight

     - are ideally shaped for supporting weight and are used for movement

       Flat Bones – protect and support body organs

    - flat bones are the ribs, pelvis, bones of the skull, and shoulder bones (scapula)

      Short Bones – are those in the hands and feet

    - support weight and allow for many small movements

      Irregular Bones – are irregularly shaped bones

Divisions of the Skeleton

A.   Axial Skeleton

The axial skeleton, making up 80 of the 206 bones, encompasses all the upper body bones. It is subdivided into three groups: the skull, the vertebral column, and the bony thorax. It's main purposes are to protect the vital organs, such as the brain, heart, and lungs, and to provide an efficient structure to preform a variety of work.

The Skull

The skull, or cranium, could be thought of as the most important structure in your skeleton, especially considering that it houses the brain. The skull provides the framework for most of the sensory organs, such as eyes, ears, tongue, nose, and some skin.

 It is made up of 22 cranial or facial bones, plus the three in each ear. As a baby you have more. Most are fixed joints (all but the mandible) separated by cartilage as a baby, but fuse together a later as you grow. Once fused, they are locked together, forming an immovable joints, called a suture

The Backbone

The backbone, or vertebral or spinal column is  a flexible structure made of 26 bones. As a baby, you have 33 vertebrae, or back bones, but the lower four fuse to form the coccyx, and the next lower five fuse to become the sacrum. The backbone provides structure from which all other upper body structures branch, and it protects the spinal nerve, which is the "highway" that all the information your brain sends to your body travels.
The backbone is approximately 28 inches, or 70 cm, long, and is separated into five regions. The last two, the coccyx and sacrum, are separated by the fused vertebrae. The remaining three are distinguished mostly by concavity with respect to your front. The remaining regions are: the cervical curvature made of 7 vertebrae and concave; the thoracic region made of 12 vertebrae and convex, and the lumbar curvature made of 5 vertebrae and concave.

The Bony Thorax

The bony thorax is basically your chest, comprising the breast bone and ribs. The breast bone, or sternum, is around 6 inches (15 cm) tall, spanning about half the length of the ribs.
You have twelve ribs, forming the structure for your chest. One primary purpose of the ribs is to protect the lungs and heart. Except for the floating ribs, each rib connects to the sternum by cartilage on the tips.

 

 

Divisions of Sternum

1. 1-7 True Ribs – are directly attached to the sternum and vertebral column
2. 8-10 False Ribs – are not attached to the sternum but attached to the 7^th rib
3. 11-12 Floating Ribs – are not attached to any bones but attached to the vertebral column

B.   The Appendicular Skeleton

The Appendicular Skeleton consists of 126 unfused bones and includes the free Appendages (Arms and Legs)

The appendicular skeleton refers to the arms and legs. They are called appendicular because they are attached by girdles, which bridge each with the main body, as if they had been appended after the main body was formed. These girdles give these appendages a remarkable range of movement unique from anywhere else in the body. Obviously the arms are the same allowing symmetry, and the legs are too. But ignoring size and shape, and instead focusing on joints and relative placement, your arms and legs are the same too.

The pectoral, or shoulder, girdle connects the arm to the axial body. The scapula, or shoulder blade, and the clavicle, or collarbone, make up the girdle.



The Upper Appendages


In our body, the Upper Appendicular Skeleton in the upper limb body region includes the bones of the pectoral girdles and the bones of upper limbs.  

The bones of the Pectoral Girdles include clavicle (collar bones) and scapula bones (shoulder blades).  

The bones of the Upper Extremity include the bones of the Arm and Forearm, and the Hands. 

In the upper arm is the humerus which connects to the girdle as a ball-and-socket joint. It connects to the forearm with a hinge joint. The forearm is really two bones, the radius and the ulna. The ulna is the bone that joins with the humerus in the elbow joint. Having two bones instead of one allows for a wide range of twisting of the wrists.

The Hand
The carpals, or wrist of the hand, is made of eight small bones in two irregular rows connect with gliding joints. These eight bones give your wrist the flexibility it has.

Five metacarpals extend from the carpus, covered with skin, form the palm. Looking at just the skeleton, they look like the base of really long fingers. The first metacarpal, the thumb base, is jointed differently that the rest of the metacarpals. They lay in a single plane, while the thumb metacarpal is connected with a saddle joint, giving it a range of movement. This is what makes grasping things as easy as it is.

The rest of the hand comprises the phalanges, what we see as the fingers. Each finger has three phalanges, except for the thumb, which has two.

  Bones of the  Upper appendages

2 clavicle                   - collarbone

2 scapula                   - shoulder blade

2 humerus                 - upper arm bone

2 radius                     - bigger bone of the lower arm

2 ulna                        - smaller bone of the lower arm

16 carpals                 - wrist bone

10 metacarpals         - palm bones

28 phalanges            - finger bones

The Lower Appendages

The Lower Appendicular Skeleton in the Lower Limb Body Region includes the bones of the Pelvic Girdle and the bones of Lower Limbs.  

In our body, the bones of the Pelvic Girdle include the two bones of the basin-shaped ring of Bones connecting the vertebral column to the femurs. 

The bones of the Lower Extremity include the eight bones of the thigh and leg, and the 56 bones in the feet.

The pelvic, or hip, girdle does the same thing as the upper body girdles. One major difference is that the two girdle in the upper body are replaced by one for the lower body.
The femur is the lower appendage equivalent of the humerus. It's the longest, largest and strongest bone of the body, must be so because of the incredible forces placed upon it.
The tibia and fibula are the equivalents of the ulna and radius. In the leg, however, the range of movement has been restricted to almost none. The tarsals are like the carpals, the metatarsus like the metacarpals, and the phalanges have the same name.

  Bones of the Lower appendages

2 pelvic girdle           - hip bone

                                 - the biggest bone in the human body

2 femur                     - long upper bone of leg

                                 - longest and strongest bone

2 patella                   - knee bone (knee cap)

2 tibia                       - lower leg (shin bone)

2 fibula

14 tarsal                   - feet (ankles)

10 metatarsals         - sole or instep

28 phalanges           - toe