O corpo humano. Versión en galego.
El cuerpo humano. Versión en castellano.

The human body.

In this section we will see the main muscles, bones and joints of the human body.

The skeletal system.

The skeleton.
The human skeleton has 206 bones, these bones and the joints, form a structure with many function like locomotion, protection and support. Another structures like ligaments, tendons, muscles and cartilages will help to the correct skeleton working.

The bones.


Types of bones:

1- Long bones like the bones of the upper and lower arms and legs.
2- Short bones like the bones of the wrist (carpal bones), or the vertebrae (sometimes you could find the vertebrae bones classified as irregular bones)
3- Flat bones like the scapula, pelvis and the bones of the cranium.

Here you have the main bones of human skeleton :


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The joints.

Joints are the union of two or more bones and where there is also a movement, but there are fixed or immoveable joints (ie the joints between the plates in the cranium).

Kinds of joints:

Depending on the grade of movement the joints are classified in:
1- Synarthrosis.
Also called fixed or immmoveable joints, a good exemple are the joints between the plates of the cranium
2- Amphiarthrosis..
Or slightly moveable joints like the joints between the vertebrae or the joints between the ribs and the sternum.
3- Diarthrosis.
Also called freely moveable joints. The bones can move quite freely. The hip joint is a good example.

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Movement at joints.
In this section we will see the types of movement possible at joints in human body. To classify the movements we have to know the body axis and the body planes. Every movement I make around an axis is made on a different plane.

Human body axis.

1- Transverse axis. This axis goes from our body one side to another. The movements produced are called FLEXION and EXTENSION and are made on a sagittal plane.
2- Vertical axis. This is an up-and-down axis and the movements around this axis are called ROTATION and are made on a transverse or horizontal plane also know as axial plane.
3- Sagittal axis. It goes from front to back, the movements here are called ABDUCTION and ADDUCTION and are made on a frontal or coronal plane.
4- There is another movement called circumduction. It is movement that includes multi-axis movements. Normaly those movements are flexion and extension + abduction and adduction + rotation, but sometimes there are only two movements, flexion and extension + rotation (knees and elbows).

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Joints and movements.

In this section we will study the types of movements possible in these joints:
1- Neck.
2- Shoulders.
3- Elbows.
4- Wrists.
5- Hip.
6- Knees.
7- Ankles.

1- The neck joint is the union of the cervical vertebrae with the cranium. In this joint we shall find all kind of movements:
- Flexion-extensionflex_ext_cuello.jpg
- Abduction-adduction also called lateral flexion:
- Rotation
- Circumduction.
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2- The shoulders. Here we have the union of three bones, clavicle, humerus and scapula. In this joint we will find all the types of movements like:
- Flexion-extensionFlex_ext_hombro.jpg
- Abduction- adduction
- Rotation
- Circumduction.

There are two more secondary but very important movements in this joint produced due to slipping of the scapula in the back. These movements are:
- Shoulders elevation and depression.Elevación_descenso_hombros.JPG

- Anterior Tipping and Posterior Tipping.
And of course a wide range of movements that arise from the combination of the above including the circumduction.
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3- Elbow. Is the union of the humerus with the ulna and the radius. In the elbow joint we can do the next movements:
- Flexion and extension, we only can do an extension in our elbow if we do a previus flexion. The maximun extension is about a few degrees more than 180º
- Rotation, is not a true rotation, in fact is called PRONATION and SUPINATION

- Circumduction. Around only two axis.
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4- The wrist is the joint that includes the union of the ulna and radius with the carpal bones. The movements possible at this joint are:
- Flexion and extension.flex_ext_muñecas.jpg
- Abduction e adduction, also called radial or cubital flexion.
- Circumduction, is the addition of the two above.
We shall not find rotation in the wrists, the movement that could seems to be is due to elbow pronation and supination.
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5- Hip joint. We shall study in this joint two points of union separately.

A) The union of the lumbar vertebrae and sacrum with the pelvis that generate movements of the torso with regard to the legs. The movements are:
- Flexion e extension.Flex_ext_tronco.JPG
- Abduction and Adduction. Also called lateral flexion
- Rotation.
- Circumduction.
B) The union of each femur with the pelvis. The resulting movements are the movements of the legs.
- Flexion e extension. flex_ext_cadera.jpg
- Abduction and Adduction.
- Rotation.
- Circumduction.
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6- Knees. The union of four bones: femur, tibia, fibula and patella. Movements:
- Flexión and extension flex_ext_rodilla.jpg
- Rotation, but the knee have to make flexion before. If you don´t make a flexion the anterior cruciate ligament (ACL) will stop the rotation.
- Circumduction.
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7- Ankles. The union of the tarsal bones (talus) with the fibula and femur.
- Flexion and extension. flex_ext_tobillo.jpg
- Abduction and adduction, also called eversion and inversion
- Circumduction.
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The muscular system.

We could not live without muscles. We could not walk, breathe or digest food witout muscles. All muscles work by shortening or contracting. Now we are going to study the three kinds of muscle and how each of them works.

Voluntary muscle. Also called skeletal or striped muscle.tipos_de_musculos_ing.jpg
This is attached to the bones and it works when you want it to. Supose that I want to walk, a signal races from my brain, along my nervous system to the muscles needed for this job. Some of these muscles are for example the cuadriceps, biceps, gluteus maximus and much more.

Involuntary muscle: Also called smooth muscle, because it have no stripes.
This is found in the walls of our internal organs like stomach, bladder, gut, blood vessels.......It works on its own, you don´t have to think about it.

Cardiac muscle: This is special involuntary muscle that forms the walls of our heart. It is striped, like skeletal muscle. It pumps blood out of our heart and around our body. Each contraction is a heartbeat.

Kinds of muscle.
(In relation to the movement)

Agonistic muscles. They have the primary responsibility when a movement is done. For example when we do a knee flexion, the HAMSTRINGS are the agonistic muscles.

Antagonistic muscles. A muscle that acts in opposition to the specific movement generated by the agonist. The antagonist must be relaxed to alow the agonist do the movement. In the example above the QUADRICEPS should be relaxed to alow the hamstrings make the knee flexion.

Synergistic muscles. They are groups of muscles that contract together to accomplish the same body movement. In the example above the GASTROCNEMIUS helps in the knee flexion.

Fixator muscles. A muscle that acts as a stabilizer of one part of the body. When you walk or run your LUMBARS AND ABDOMINALS contrat to fix the hip joint and alow you to run without fall down.


The muscle fibres.

Muscles are made up of cells called muscles fibres. Muscles contract because fibres do. But they don´t all contract together. The number contracting at any one time depends on how much forde is needed.

Kind of muscle fibres.
There are two types of muscle fibres depending on the contration speed.
1- Fast twitch fibres. They have a high contraction speed. They are also called anaerobic or white fibres, because of they low oxigen concentration. They tire very quickly.

2- Slow twitch fibres, also called aerobic or red fibres. They contract slowly and without much force but they don´t tire easily.

You are born with a mix of slow and fast twitch fibres. You cannot change one to the other even with trainning.

Every sport needs a different amount of fast or slow twitch fibres. Sprinters have a lot of fast twitch fibres but long distance runners have a lot of slow twitch fibres.

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Human body muscles

Here you have the main muscles of the human body.
musculos_nombre_ing_(600_x_499).jpgIf you want to learn more, click on the muscle name:
Latissimus dorsi.
Lumbar muscles.
Aducctor muscles.
CALF (Gastocnemius and soleus)

Sternocleidomastoid. It´s the main muscle of the neck. It function is a double function: If there is only a one side contraction there is a neck rotation (in the opposite direction), a lateral flexion and a slight neck extension. But if both muscles have a contraction there is a neck flexion. In emergency situations it helps to make the inspiration.

Trapezius. The main function of the trapezius to have under control all the movements of the scapula, elevation and depression and anterior and posterior tipping, and therefore also the shoulder movements. It is a esential muscle to have a upright posture. Here you have an example of a trapezius exercise.

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Deltoid. The deltoid is the muscle that covers and protects the shoulder joint. It basic funtions are the flexion and extension of the shoulder and also the abduction. One of the most used exercises to make a sholders workout is the "side lateral raise".

Pectorals. There are two pectoral muscles: pectoralis major and pectoralis minor. Their functions are similar, their make a flexion and an adduction of the shoulder when they contract. Two of the most popular exercises to work with the pectorals are the chest push ups and the chest bench press.


Latissimus dorsi. It makes the shoulders extension. It is an esential muscle in swimmers and climbers. If you want to work with your latissimus dorsi you could do wide grip pullups.

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Lumbars. When we talk about lumbars muscles we are talking about the muscles of the end of back that make the back extension. Specifically that muscle is called Quadratus lumborum and works helped by the iliocostalis muscles. We can work with lumbar muscles if we lay on the floor and make multiple hip hiperextensions. Also we can do it on a bench.

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Abdominal muscles. They are the muscles that cover the abdomen. Their functions are to protect the internal organs and to make the hip flexion and rotation.
There are three diferent abdominal muscles:

1- Rectus abdominis muscle. The main function of this muscle is to make a hip flexion, help in the abdominal breathing, protect the internal organs and help in the defecation. To improve the rectus abdominis strength we usually do sit ups. Make sure that your knees and hip are in flexion when you do sit ups in order to protect your back.

2- Transversus abdominis. It is the deepest muscle of the abdomen. Basically its function is to compress the abdomen. Helps in defecation and when you vomit or cough.

3- Obliquuos abdominis. We shall find the abdominal external oblique(obliquuos externus abdominis) and the internal oblique muscles. Both muscles have similar functions, they act over the hip, making a flexion (if right and left sides work together) or making a rotation if only one side works, (if I do a rotation to the left, the left internal and the right external are the muscles that work). Here you have an interesting video that explains how to work with obliquuos abdominis (It´s in spanish).


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Biceps. The biceps is the muscle of the front side of the upper arm. It is called as "biceps (biceps brachii)" because it has two heads, a long and a short one, both heads have only one point of union (insertion) in the radius, and each head attaches to (originates from) the scapula in two diferent points. The biceps has several functions, the most important being to rotate the forearm supination and to flex the elbow. Here you have an example of both works.


Triceps.The triceps brachii muscle (three-headed arm muscle) is the large muscle on the back of the upper arm. It is the muscle principally responsible for extension of the elbow joint. You can improve your triceps strength just like that.

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Quadriceps. It is the muscle of the anterior side of the thigh. It is subdivided into four separate portions or 'heads', which have received distinctive names: Rectus femoris and three portions called vastus: lateralis, medialis and intermedius.

The main function of the quadriceps is to make the knee extension. The tipical exercise to work with the quadriceps are the squats.


Hamstrings. The hamstrings are the three posterior thigh muscles. These three muscles are the semitendinosus, the semimembranosus , and the biceps femoris. The hamstrings cross and act upon two joints, the hip and the knee. Basically they act extending the hip and flexing the knee. We can do this exercise in a gym to work with the hamstrings.


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Gluteals. There are three muscles called gluteals: gluteus maximus, gluteus medius, and gluteus minimus. Their functions are basically to make a hip extension and abduction.

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Adductors. They are the inner thigh muscles, Adductor magnus, (sometimes the upper portion is called adductor minimus), adductor longus, and adductor brevis. These muscles arise from the pubis and are inserted in the femur. Their main funtion is to make a hip adduction.


Gastrocnemius. Yes it´s called CALF, but we can find two muscles, the gastrocnemius (lateral and medial heads) and the soleus. Their main funtion is to make the plantar flexion of the ankle, and only the gastrocnemius also acts making a knee flexion. Both muscles are inserted in the calcaneus bone by the achilles tendon. If you want to work with them you can do this exercise.

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