Unit 5 Energy Metabolism

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Unit 5
Outcome 2 – Energy Metabolism Booklet

The Respiratory System
The respiratory system consists of the nose, mouth, pharynx, larynx, trachea, bronchi and lungs. These provide a passageway to allow air in and out of the body. Every cell in the body requires oxygen to survive.

The primary function of the respiratory system is the exchange of gases. The respiratory system allows oxygen and carbon dioxide exchange, this is necessary to sustain life. During the process of breathing air is inhaled and carbon dioxide is exhaled, this change of gases occurs in the alveoli. The inhaled oxygen passes into the alveoli and then diffuses into arterial blood. The waste rich blood from the veins releases carbon dioxide into the alveoli which is released through exhaling. Air enters through nostrils which contain coarse hairs. The pharynx is shared between the digestive and respiratory system and extends between the nostrils and the larynx. The larynx joins the pharynx to the trachea; it consists of cartilages and is also known as the voice box. The trachea divides to form the primary bronchi, the left and right bronchi which the bronchi are two tubes that carry air into the lungs and they .break down into smaller branches which are called bronchioles. At the end of these are air sacs called alveoli which absorb oxygen from the air. The diaphragm is a muscle which is directly below the lungs, during inhalation the diaphragm contracts to allow the chest cavity to expand as the lungs fill with air.  

Respiration Process
* Oxygen is taken in through the mouth and the nose and then passes through the trachea and bronchial tubes and onto the alveoli in the lungs, where it diffuses.

* The oxygen in the alveoli then diffuses into the blood capillaries where it binds to haemoglobin and is transported to every cell in the body.

* Carbon dioxide is transported in the opposite direction by the blood away from the cells in the body and to the capillaries which are attached to the alveoli.

* The carbon dioxide then diffuses from the blood and into the air in the alveoli and it is then exhaled through the nose and the mouth.

Pathway of air
Air goes through the nasal cavities or oral cavity through the pharynx, trachea, primary bronchi, secondary bronchi, tertiary bronchi into the bronchioles and the alveoli where gaseous exchange occurs. The exchange of oxygen and carbon dioxide between the alveoli and the blood occurs during diffusion. Oxygen diffuses from the alveoli into the blood where it is transported to every cell in the body. 98.5% of oxygen is carried in the blood by being bound to hemoglobin and 1.5% is carried by dissolving in the plasma. The pressure of the oxygen in the alveoli must be kept higher than blood pressure to maintain a concentration gradient. Breathing insures there is continuous fresh air brought into the lungs and alveoli. Alveoli have very thin walls and are abundant which means they are efficient in exchanging gases.

Mechanisms of Breathing
Breathing occurs of the changes of pressure within the thorax. When we inhale the intercostal muscles and diaphragm contract and expand the chest cavity. The diaphragm flattens and moves down and the rib cage is moved upwards and out by the intercostal muscles this increase the size of the lungs and draws air in. When we exhale the diaphragm and intercostal muscles relax and return to their original position. This reduces the size of the thoracic cavity and forces air out of the lungs.

The Digestive System
The digestive system allows food to be broken down and made soluble so it can be absorbed by the body. Once the food is absorbed by the body it is changed into energy to fuel the body.

The main function of the digestive system is to break down the food and fluid so that they are simple chemicals that can easily be absorbed into the bloodstream so they can be transported around the body. The mouth is where...
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