Body Systems

The Skeletal System:

Babies start with 270 bones, which fuse down to 206 as an adult.

Functions of the skeletal system:

1. To protect vital organs and provide shape to the body: Bones give the correct shape to the body and protect organs from damage. eg, Cranium protects the brain.

2. To enable movement: Muscles pull on the bones to enable movement

3. To produce blood cells: It produces red and white blood cells in the bone marrow. White blood cells fight infection, and red blood cells carry oxygen to the muscles. Red blood cells are red in colour due to a protein containing iron called haemoglobin. The production is very high during growth years and decreases with age.

4. To store minerals and nutrients: The nutrients will be released when the body needs them

Bones to Remember:

The Cervical has 7 bones, the Thoracic has 12, the Lumbar has 5, the Sacrum has 5, and the Coccyx has 4.

The Muscular System:

There are 600 muscles in the human body.

Muscles to know:

• Trapizius: Neck and upper back

• Deltoid: Shoulder

• Pectoralis Major: Chest

• Wrist Flexors: Forearms

• Hamstrings: Back of the thighs

• Gastrocnemius: Calves

• Soleus:

• Tibialis Anterior: Shins

• Quadriceps:

• Biceps: The front of the arm

• Triceps: Back of the arm

• Latissimus Dorsi: Back, between the Trapezius and Erector Spinae

• Gluteus Maximus: The butt

• Obliques: The sides of the abs

• Adductors/Abductors: Hips and Inner Thighs

• Rectus Abdominis: Abs

• Erector Spinae: Lower back

Functions of the muscular system:

1. Create movement: By pulling on bones

2. Posture: Skeletal muscles provide the force needed to stabilise the body. Their flexibility and strength are key to maintaining proper posture.

3. Heat Production: The contraction of muscles generates heat. The heat that is produced is vital for a stable body temperature. Eg. When you shiver, it is your muscles moving that generate heat, warming you up.

The Musculoskeletal System:

It refers to bones, muscles and more specifically ligaments and tendons. It involves the collaboration between the skeletal and muscular systems that provides movement.

Ligaments: A fibrous tissue that connects bone to bone. They provide stability at the joint where the movement occurs

Tendons: Tough bands that connect muscle to bone. As muscles contract/relax, they pull on bones, creating movement.

Reciprocal Inhibition:

When muscles work in pairs to enable movement (flexion and extension).

—Flexion is a movement that decreases the angle formed by the joint, and extension is a movement that increases the angle formed by the joint.

In reciprocal inhibition, one muscle contracts (shortens); this is known as the agonist, and the paired muscle relaxes (lengthens); the muscle is known as the antagonist.

The Cardiovascular System (The Circulatory System):

It consists of the heart and blood vessels. They work together to transport gases and nutrients around the body.

Functions:

• Circulates blood around the body

• Transports oxygen and other nutrients to cells

• Transports waste (carbon dioxide) away from the cells

• Maintains a stable body temperature.The

There are three types of blood vessels:

Arteries: They carry blood away from the heart and to the body and its cells. They generally carry oxygenated blood (every artery except the Pulmonary artery). They have thick, elastic walls, allowing them to expand and accommodate more volume since they receive blood directly pumped from the heart. They rely on the heart for blood flow.

Veins: They carry blood to the heart and away from the body and its cells. They generally carry deoxygenated blood (every vein except the Pulmonary vein). They have thick, elastic walls, allowing them to expand and accommodate more volume since they receive blood directly pumped from the heart. Veins rely on skeletal muscles contracting for blood flow. Veins also have one-way valves that prevent blood from flowing in the wrong direction.

Capillaries: They are the smallest and thinnest type of blood vessel. This is the site where nutrients and waste are exchanged (very fast) between the blood and cells. The capillaries connect the arteries and veins.

Heart: It is a pump that is designed to push blood throughout the cardiovascular system. It is located slightly to the left of the chest, between the two lungs. It is protected by the rib cage, and it is about the size of a large fist (an adult one).

Heart rate is the number of times your heart beats in a given time, measured by taking your pulse in beats per minute (bpm). At rest, the average heart rate is 72 bpm. Heartbeat is the sound when listening to your pulse.

When looking at heart diagrams, it is important to note that the left and right sides are opposite.

The heart has 4 chambers, the right and left atria, the chambers that receive blood and the right and left ventricles, the chambers that pump blood. The left side has oxygenated blood FOR the body, and the right has deoxygenated blood that travels TO the lungs so the carbon dioxide can be expelled from the body. It is important to note that the left side of the heart is more muscular than the right side. This is because the left side must pump blood to the whole body while the right side only pumps blood to the lungs.

The pathway of blood:

Key points:

1. The right atrium receives deoxygenated blood from the superior and inferior vena cava. The superior vena cava collects blood from the upper regions of the body, while the inferior vena cava collects blood from the lower regions of the body.

2. The blood travels through the valve (which closes after the blood has entered so that the blood doesn’t flow in the wrong direction) and enters the right ventricle. From there, the blood is pumped into the pulmonary artery (the only artery that carries deoxygenated blood), which carries the blood to the lungs.

3. Inside the lungs, gaseous exchange occurs (not required for the test), and the carbon dioxide and oxygen are exchanged. The newly oxygenated blood travels back to the heart through the pulmonary vein (the only vein that carries oxygenated blood).

4. The left atrium receives the oxygenated blood from the pulmonary vein.

5. The blood travels through the valve into the left ventricle. The left ventricle pumps blood into the aorta (the largest artery in the body) which distributes the blood to the rest of the body.

6. The oxygenated blood is transported around the body and it delivers the oxygen and nutrients through the capillaries. The waste that is transferred to the veins and the process is repeated again.

Respiratory System:

It includes the mouth, nose, throat, voicebox, windpipe and lungs. It is specialised for gas exchange.

Major organs:

The lungs: They are a major organ of the respiratory system and they are located in the chest cavity behind the ribs. The lungs allow oxygen to be taken into the body and carbon dioxide to leave the body.

The Alveoli: They are tiny air sacs within the lungs. It is in the Alveoli where the lungs and blood exchange oxygen and carbon dioxide during breathing.

The Diaphragm: It is a major muscle of the respiratory system that helps inhale and exhale.

Functions:

1. Brings air from the atmosphere into the lungs

2. Transfers oxygen from the air into the blood

3. Removes carbon dioxide from the blood

4. Expels heat from the air when exhaled

5. Allows the vocal cords to create speech as air is exhaled

Breathing is the process of taking air into and expelling it from the lungs. The process of breathing relies on the idea that air particles naturally move from places with high pressure(more concentrated) to places with low pressure (less concentrated). It is broken down into two main phases:

Inspiration (inhale): It is the process where the air is drawn INTO the lungs. During inspiration, the diaphragm contracts (gets smaller) and moves downwards. The muscles between the ribs (intercostal muscles) also contract, increasing the size of the chest cavity, causing the air pressure to decrease. Air is drawn into the lungs because of the variation in air pressure.

Expiration (exhale): It is the process where the air is expelled FROM the lungs. During expiration, the diaphragm relaxes (gets bigger) and moves upwards. The muscles between the ribs (intercostal muscles) also relax, decreasing the size of the chest cavity, causing the air pressure to increase again. Air is forced from the lungs because of the variation in air pressure.

*Not required for test:

Gaseous Exchange:

• The process where gases move across a surface without the use of energy. 

• Between the alveoli and the capillaries in the lungs

- Allows deoxygenated blood to become oxygenated

- Carbon dioxide moves from the capillaries to the alveoli. 

- Oxygen moves from the alveoli to the capillaries. 

• Between the capillaries around the skeletal muscles and the muscle cells

- Oxygenated blood becomes deoxygenated.

- Carbon dioxide moves from the muscle cells to the capillaries. 

- Oxygen moves from the capillaries into the cells.