Unit 3. The respiratory system

Unit 3: Nutrition. The respiratory system

Nutrition

- It’s exchange matter and energy with the surrounding - Four systems participate in nutrition: digestive, respiratory, excretory and circulatory

• Respiratory system enables:
• Oxygen to enter the body and pass into the bloodstrem; and it’s responsible for expelling carbon dioxide from the body
• Sense of smell
• Phonation

Anatomy of respiratory system

1. The respiratory system

It’s formed by:

• The respiratory tract
• Lungs

Nassal passages

Pharynx

Larynx

Trachea

Bronchi and bronchioles

1.1. The respiratory tract

• It consists of tubes which let entry and exit of air from outside to lungs, and viceversa.

Nasal passages: They are two cavities that communicate with outside through nostrils. In the superior nasal cavity, it has olfactory epithelium (sense of olfaction)

Functions:

• Allowing passage of air
• Moistening air
• Warming air
• Retaining microorganisms and dust

Pharynx

• It’s a common organ between digestive and respiratory systems

• Epiglottis is a cartilage located at the top of the larynx and its function is to seal off the windpipe during eating.

Larynx

It’s a short tube made of cartilage. In the larynx are vocal cords, that vibrate in response to the passage between them of air exhaled from the lungs. Function:

• Phonation
• Passage of air

Trachea

• It’s a short and flexible tube formed by C-shaped cartilage rings (not complete), that avoid block trachea.
• The trachea is lined with a moist mucous-membrane layer composed of cells containing small hairlike called cilia.
• Function:
• * The cilia trap particles.
• * Cells secrete mucous

Bronchi

Bronchi are two tubes that branch out from the trachea into each lung. They have similar structure of trachea, but when bronchi penetrate lungs, C-shaped cartilage rings are complete.

Bronchioles

Bronchioles are the ramification of bronchi inside lungs, forming bronchial tree. They have irregular C-shaped cartilage rings. Thet become smaller tubes with thin walls. They end in tiny, rounded sacs with very thin walls, called pulmonary alveoli.

Pulmonary alveoli

Alveoli are grouped in alveolar sacs that five the lungs their spongy appearance They are surrounded by capillary plexus which allow exchange gases.

Each person has 300 - 400 millions of pulmonary alveoli!!

2. Lungs

• They are spongy organs located in the thoracic cavity ( on top of diaphragm) on either side of the heart.

• They are protected by the ribs
• Left lung is the smaller of two and has two lobers
• Right lung is the larger of two and has three lobes

• Both lungs are surrounded by two membranes called the pleura.

• Function: it protect the surface of lungs and it let expansion of lungs inside the thoracic cavity

Unlike other arteries and veins, the pulmonary arterys carry deoxygenated blood to the lungs. And the pulmonary veins branching out from the lungs carry oxygenated blood

Physiology of respiratory system: RESPIRATION

Respiration: is the movement of oxygen from the outside environment to the cells within tissues, and the transport of carbon dioxide in the opposite direction.

Pulmonary ventilation

Respiration

Gas exchange

3. Pulmonary ventilation or breathing

• It’s the movement of air in and out of the lungs
• It consists of two involuntary movement

Exhalation

Inhalation

Inhalation

• It’s the process of intake of air into the lungs, so oxygen-rich air enters the lung through the respiratory tract
• The process does not need conscious control
• However, breathing can be consciously
• or interrupted (within limits).

Mechanism of inhalation

• The air pressure inside the lungs must be lower than that of the external atmosphere as air flows from areas of higher pressure to lower pressure.
• This is achieved by the contraction of the external intercostal muscles which acts to pull the ribcage upwards and outwards, hence, increasing the volume of the thoracic cavity. The diaphragm also contracts to extend the cavity further downwards

Exhalation

- It is the movement of air (carbon dioxide-rich air) from the lungs out of the airways - It’s a passive movement as a result of inhalation

Mechanism of exhalation

The diaphragm relaxes and moves up and the relaxation of the intercostal muscles moves the ribs in an down. This has the effect of decreasing the volume within the thoracic cavity and increasing the pressure within the lungs with respect to atmospheric pressure. As a result, aire moves out of the lungs down a pressure gradiente.

4. Gas exchange

• We need to get oxygen from the air into the blood, and we need to remove waste carbon dioxide from the blood into the air. Moving gases is called: Gas exchange, and takes place in the pulmonary alveoli.

Features of alveoli

They have a lot of tiny blood vessels called capillaries

They area that they provide for gas exchange is 150 -200 m2

They have moist and thin walls

Mechanism of gas exchange

1. Red blood cells (erythrocytes) carry a large amount of haemoglobin, a protein with an iron atom, that transports oxygen and carbon dioxide.

Mechanism of gas exchange

2. The concentration of CO2 in the blood capillaries is (4,5%) is higher than in the alveoli (0,03%). This is due to blood flowing through the capillaries has collected from tissue cells, so they transport haemoglobin rich in carbon dioxide

Mechanism of gas exchange

3. Capillaries discharges the carbon dioxide and obtain oxygen from breathing at the same time, carries to the same cells. Both gases pass through the membranes of the alveolar epithelial cells and the capillary endothelium by simple diffusion

Mechanism of gas exchange

4. The CO2 passes into the alveoli for expulsion from the body through the respiratory tract. And O2 is absorbed by haemoglobin (Hb) to every cell in the body

Diseases of the respiratory system

Asthma

It’s a narrowing of bronchial tubes due to:

• Contraction of bronchial wall
• Inflammation of mucosa
• Excess mucus
• The symptoms is breathing becomes difficult
• It could be triggered by smoke, pollution, allergies (pollen, house dust mites,…)

Allergic rhinitis

It’s an inflammation of nasal mucosa because of an allergy to:

• Pollen
• Dust mites
• Animal dander,…
• The symptoms are congestion, sneezing and itchy nose or throat

Pharyngitis and tonsillitis

Pharyngitis is an inflamation of the pharynx Tonsilllitis is an inflamation of the tonsils.

Pharyngitis and tonsillitis

The main symptoms of both are:

• Located pain
• Increased mucus
• Fever
• Coughing

Pneumonia

It’s an inflammation of lung tissue due to bacterial or virus infection The main symptoms are:

• Difficulty in breathing
• High fever

Colds and flu

Both are infections of the respiratory tract due to a virus (flu virus is called influenza)

Bronchitis

It’s an inflammation of bronchial mucosa due to bacteria, microorganisms, virus or irritants substances The main symptons are:

• Difficulty in breathing
• Wheezing cough with yellow-green phlegm
• Aches and pain

Lung cancer

It’s unusual cell growth in bronchial tubes and lung tissue The main symptoms are:

• Lungs stop functioning correctly
• Pain and possible death

Pulmonary emphysema

It’s the enlargement of the alveoli caused by weakened, and rupture walls The main symptoms are: - Breathing becomes progressively limited, almost permanently It’s caused by smoking or air pollution

Coughing and sneezing

Coughing is a defence mechanism because it clears your throat of mucus or foreign irritants Sneezing is the involuntary act of expelling irritants from your nose or throat

Irritant: substance that makes part your body sore or painful, like pollen, house dust mites,…

Healthy habits

Ventilate bedrooms every day at least 10 minutes

Keep rooms clean of dust and dust mites

Do regular aerobic exercises to improve your lung capacity and cardiovascular activity

Avoid places that are polluted, poorly ventilated or crowded

AND…

DON’T SMOKE!!

Don’t smoke

• Smoking is an addiction that directly causes many respiratory disease and makes the symptoms of many other diseases worse.
• Also, it has a negative effect on diseases of circulatory, digestive and nervous systems.
• Smoking kills almost six million people every year, and 10% of them are non-smokers.

Don’t smoke

Analysis of cigarette smoke reveals over 4000 chemical substances, like:

Nicotine

Tar

Carbon monoxide

This toxic substance makes smoking addictive. For this reason, nowadays tobacco is considered a drug

This very poisonous gas interes the the bloodstream and it links to haemoglobin, impeding the transport of oxygen. This is the reason why smokers become tired

A mixture of substances that is deposited on the cilia of the respiratory tract and it prevents them from cleaning the airways