THE RESPIRATORY SYSTEM Flashcards
The respiratory system main purpose
Is to exchange gases with the environment by the taking of oxygen
and disposal of carbo dioxide. The respiratory system main functions are:
* Inhalation – taking air into the lungs and supply blood with oxygen.
* Exhalation – taking air out of the lungs and disposing carbo dioxide out of the blood.
Structure of the respiratory system
The respiratory system is divide in two categories:
1. Upper respiratory tract – located above the thoracic cavity (neck and head) and involved with the
process of respiration.
2. Lower thoracic cavity – located inside the thoracic cavity (inside and protected by the ribs) and
involved with gases exchange.
Structure of U.R.T( upper respiratory tract)
- Oral cavity – sometimes called stoma. The inside of the mouth where air enters.
- Nasal cavity – hallow area in the nose where air is warmed and filtered.
- Pharynx – located in the back of the mouth and the nose, both air and food pass through it.
- Larynx – contains the vocal cords, and is essential for speech. Air vibrates the cords and produces sound.
- Epiglottis – flap of tissue that covers the larynx while swallowing, preventing entrance of food to
the respiratory tract. - Trachea – hallow tube that has rings of cartilage in its walls continuing down into the thoracic cavity.
Structure of L.R.T(lower respiratory tract)
- Lower part of trachea.
- Bronchi
- Bronchioles
- Alveoli
- Diaphragm
- Pleura
Bronchi
A continuation of the trachea after it is divided into two tubes (left and right).
Bronchioles
Further segmentation of bronchi into smaller and smaller tubes.
Alveoli
air from bronchioles finally arrives into those epithelial sacks. This is the main site of gas exchange and therefore, alveoli are surrounded by a capillary bed. The lungs themselves are composed of many alveoli. Alveoli are composed of simple squamous epithelium. On the other hand, the walls of the trachea are composed of pseudostratified epithelium with cilia, smooth muscles, cartilage rings and connective tissue. As we progress down the tract, we gradually lose
all of these tissues.
Diaphragm
A strong muscle that separates the thoracic cavity from the abdominal cavity. It is shaped like a parachute and when it contracts it becomes flatter.
Pleura
A membranous sack that raps the lungs and is composed of two continues layers:
- Visceral pleura – firmly attached to the lungs.
- Parietal pleura – firmly attached to the walls of the thoracic cavity.
Inside the pleural space there is a small amount of fluid that prevents friction during lungs movement and holds them together.
Important to remember about the lungs
- Breathing rate is about 12-14 breaths per minute.
- The right lung is composed of three lobes, while the left lung is composed of two lobes.
- The lungs contain surfactant – a liquid containing phospholipids that is found inside the alveoli and reduces surface tension.
Functions
As said before, the primary function of the respiratory system is exchanges of gases – absorption of oxygen from alveolus into capillaries and disposal of 𝐶𝑂2 from the capillaries into the alveolus. This happens in passive diffusion. Gas exchange accurse mostly in the alveoli. The rest of the respiratory tract is considered
anatomical dead space.
Mechanism of Breathing
Inhalation – an active process in which the diaphragm contracts and flattens, and the external intercostal
muscles contract. This process increases the volume of the thoracic cavity resulting in a flow of air inwards.
Exhalation – divided into two types:
* Passive exhalation – does not require energy and is driven by elastic forces.
* Forced exhalation – an active process in which the internal intercostal muscles and abdominal
muscles contract, decreasing thoracic volume and pushing air out.
** Before inspiration, the intrathoracic pressure is negative to the atmospheric pressure. During
inspiration its equal (air not going in or out), and after it its positive.
Breathing Regulation
Breathing can be voluntary and also involuntary. Breathing reflex is generated by neurons in the brainstem. This reflex is mostly 𝐶𝑂2 sensitive.
- Voluntary – independent respiration of 𝐶𝑂2 controlled by Cerebral Cortex.
- Hyperventilation – rapid loss of 𝐶𝑂2 which increases blood 𝑝𝐻 and can lead to alkalosis.
- Hypoventilation – accumulation of 𝐶𝑂2 which decreasing blood 𝑝𝐻 and can lead to acidosis.
- Involuntary – dependent respiration controlled by the Brain Stern and is regulated by 𝐶𝑂2 level in the blood.
Lung Capacities
- Total Lung Capacity (𝑇𝐿𝐶) – the maximum amount of air that can be held by the lungs.
*Residual Volume (𝑅𝑉) - the amount of air left in the lungs after forced expiration. - Vital Capacity – the total amount of air that can be add into the lungs after forced exhalation (𝑇𝐿𝐶 −𝑅𝑉).
- Expiratory Reserve Volume (𝐸𝑅𝑉) – the amount of air that can be pushed out of the lungs after
passive exhalation. - Inspiratory Reserve Volume (𝐼𝑅𝑉) – the amount of air that can be inhaled in the end of a passive
exhalation. - Tidal Volume (𝑇𝑉) – the volume of a regular inhalation/exhalation 500 𝑚𝑙/𝑐𝑐.
- Functional Residual (𝐹𝑅) – the amount of air after passive exhalation.
- Inspiratory Capacity (𝐼𝐶) – the amount of air that can be added after regular inhalation.
Pathology
Asthma – a chronic lung disease that inflames and narrows the airways characterised by periods of
wheezing chest tightness, shortness of breath and coughing – affects people of all ages, but most often
starts during childhood.
Infant respiratory distress syndrome (𝐼𝑅𝐷𝑆) – syndrome in premature infant, due to a lack of surfactant production making it difficult to breath.
Acute respiratory distress syndrome (𝐴𝑅𝐷𝑆) – widespread inflammation of the lung, due to a disease of the alveoli which leads to decrease exchange of oxygen and carbo dioxide.
Inflammations:
- Pneumonia – inflammation of the lungs.
- Bronchitis – inflammation of the bronchial tree.
- Laryngitis – inflammation of the larynx.
- Stomatitis – inflammation of the stoma (oral cavity).
- Tracheitis - – inflammation of the trachea.
