The Muscular System

The muscular system makes up nearly half the weight of the human body, this is why when we train we sometimes put on weight instead of losing it. We put on muscle weight.

The muscles provide the forces that enable the body to move. Muscles stretch across joints to link one bone with another and work in groups to respond to nerve impulses.

Click here for 8 superb A4 size downloadable human body system pictures, including diagrams of the human body muscular system!

There are three types of muscle:

Skeletal muscle

• There are nearly 650 skeletal muscles in the human body!
  
• Skeletal muscles are attached to the skeleton
  
• They work in pairs: one muscle moves the bone in one direction and the other moves it back again
  
• Skeletal muscles are voluntary muscles - in other words we think about what movements we want to make (at least, usually!) and send messages via our nervous system to tell the appropriate muscle(s) to contract.
  
• Muscle contractions can be short, single contractions or longer ones.
  

Smooth muscle

• Smooth muscle is found in our internal organs: in our digestive system, our blood vessels, our bladder, our respiratory organs and, in a female, the uterus.
  
• Smooth muscle can stretch and maintain tension over extended periods
  
• Smooth muscles are involuntary muscles - in other words we do not have to think about contracting them because they are controlled automatically by the nervous system. It would be pretty inconvenient if we had to think about digesting our food, for example!
  

Cardiac muscle

As the name should tell you, cardiac muscle is found only in the heart.

It can stretch, just like smooth muscle, and contract like skeletal muscle.

It is a twitch muscle - it only does short single contractions

Like smooth muscle, cardiac muscle is involuntary. It'd be rather dangerous if it were voluntary - we could stop our heart beating any time we wanted!

Muscle Structure

Our muscle structure consists of densely packed groups of elongated cells known as muscle fibres.
• Skeletal muscle is composed of bundles of long striated fibres.


• Smooth muscle which is found in the walls of internal organs such as intestines is made of short spindle-shaped fibres packed together in layers.


• Cardiac muscle found only in the heart has short interconnecting fibres.

• These fibres are held together by fibrous connective tissue.
• Capillaries penetrate this tissue to keep the muscles supplied with oxygen and nutrients that are needed to fuel contraction.
• In a relaxed muscle the thick and thin threads within a muscle fibre overlap a little.
• When a muscle contracts, the thick filaments slide further in between the thin filaments like interlacing fingers. This action shortens the entire fibre.

Human Body Muscle Diagram

Click here for 8 FANTASTIC downloadable A4 human body system pictures, including more detailed diagrams of the human muscle system!

There are over 600 skeletal muscles in the human body attaching to a bone and connecting a joint to enable us to move our limbs.

The neck muscles and massive triangular muscles of the back stabilize the head and shoulders and permit a range of complex movements. The most powerful muscles in the body and those that run along the spine. They maintain posture and provide the strength for lifting and pushing.

The face muscles control a wide range of movements and are especially complex around the mouth and eyes.

The Digestive System

• The digestive system works to physically and chemically break down food.
• Food and fluids are processed by the digestive organs so that nutrients can be absorbed from the intestines and circulated around the body.
• The digestive process is mostly completed when food reaches the end of the small intestine.
• The digestive organs include the mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.
• These organs together form a food-processing pipe that is 30 foot long!
• Salivary glands, the pancreas, the liver and the gallbladder also play an important role in digestion.
• The appendix, a short, blind ended tube attached to the large intestine has no known function.
• Food is moved through the digestive tract by muscular contractions.

The Cardiovascular System

• The cardiovascular system is the body’s blood transporting network of arteries, veins and vessels.
  
  
• It is responsible for carrying oxygen and vital nutrients to all parts of the body and removes harmful waste products from tissues.
  
  
• The heart pumps blood through arteries and smaller vessels to all parts of the body.
  
  
• The blood returns to the heart through veins.
  
  
• The pulmonary arteries are the only arterial vessels that transport deoxygenated blood.
  
  
• Blood makes a full circuit of the body in about one minute.
• 
  

----------------------------