The respiratory system

What is the structure of the nose like?

• The external part of the nose is the portion visible on the face and consists of bone and cartelidge covered by skin and lined with mucous membrane. It has two openings called the nostrils.
• The internal nose connects to the throat through two openings called internal nares. Four oaranasal sinuses and the nasolacrimal ducts also connect to the internal nose. The nasal cavity lies below the cranium and above the mouth. The nasal septum divides the nasal cavity into right and left sides. 

What three functions is the nose specilaised for?

• Filtering, warming and moisturising incoming air.
• Detecting olfacotry stimuli (smell).
• Modifying the vibrations of speech sounds. 

What is the structure of the pharynx like?

It is a funnel shaped tube that starts at the internal nares and extends partway down the throat. It is composed of skeletal muscle and lined with mucous membrane.

What are the main functions of the pharynx?

• Functions as a passageway for air and food.
• Provides a resonating chamber for speech sounds.
• Houses the tonsils.

What is the structure of the larynx like?

A short tube of cartilage lined by mucous membrane which connects he pahrynx to the trachea. The larynx consists of three different types of cartilage including thyroid cartilage, the epigollitis and cricoid cartilage.

What is the function of the larynx?

The laynx is also known as the voice box and its function is therefore to produce voice sounds 

How do the two bronchus work?

The trachea divides into the right and the left main bronchus, the right main bronchus tends to go straight down but the left main bronchus goes off at an angle.All the air into the left lung goes through the left main bronchus, and all of the air going into the right lung goes through the right main bronchus. The two main bronchus contain C shaped rings of cartilage to keep them patent.

How does the right bronchus work?

The right main bronchus divides into three bronchioles these are known as the three right loba bronchi. These then breakdown to form the segmental bronchi.  These then break down into bronchiole passages. These parts take air to all parts of the lungs. They divide in a fractile pattern meaning airflow is equal to all parts of the bronchiole tree.

How does the left bronchus work?

The left bronchus divides into two bronchioles, still quite large with C shaped rings of cartilage- these are known as the loba bronchi because they are both going to each one of the left lungs lobes. These then breakdown to form the segmental bronchi. These then break down into bronchiole passages. These parts take air to all parts of the lungs. They divide in a fractile pattern meaning airflow is equal to all parts of the bronchiole tree.

What is the basic structure of the right and left lungs?

The right and left bronchus with the bronchioles then form the lungs. The left lung is in two lobes called the upper and lower lobe. The right lung is divided into three lobes. The fractile pattern of the bronchus means it can carry air equally to all parts of the lungs. The intercostal muscles form the thoracic wall (chest wall).The lungs are sspongy, cone-shpaed organs n the thoracic cavity.

How do the ribs protect the lungs?

The ribs surround the lungs, in-between the ribs there are muscles known as intercostal muscles. There are two main sets of intercostal muscles the external intercostal muscles and the internal intercostal muscles.  The ribs are connected to the sternum by the costal cartilages.

How does air get into the lungs?

The ribs surround the lungs, in-between the ribs there are muscles known as intercostal muscles. There are two main sets of intercostal muscles the external intercostal muscles and the internal intercostal muscles.  The ribs are connected to the sternum by the costal cartilages.

How does the body facilitate inspiration?

To facilitate inspiration the chest wall moves up and out and the diaphragm moves down. For the ribs to move up and out the external intercostal muscles contract. The stomach goes out because the diaphragm goes down pressing on the abdominal muscles. When the diaphragm is domed up it is relaxed but contracts and moves down to facilitate inspiration- 75% of respiratory effort is done by the diaphragm. To be able to breathe freely you need both the chest wall and abdominal muscles to be free. When inspiration occurs the volume in the lungs will increase and the pressure will decrease. The pressure inside the lungs will be less than the pressure in the external air, air will then move down this pressure gradient to equalise the pressure. Therefore, the external air is sucked into the lungs.

How does the body facilitate expiration?

To facilitate expiration the external intercostal muscles relax allowing the chest wall to fall down and in.  The diaphragm relaxes and therefore goes up into the domed upward position. This reduces the volume in the thoracic cavity and increases the pressure. The pressure of the air inside the lungs is therefore greater than the air in the external environment, therefore air is blown out.

What are the functions of the two pleural membranes?

The external pleural membrane goes around the inside of the thoracic cavity- this is known as the parietal pleural membrane, this also lines the surface of the diaphragm. Each lung is surrounded by its own pleural membrane. The parietal pleural membrane is fixed. There is also a visceral pleural membrane which is fixed to the surface of the lung. The parietal pleural membrane moves out when the chest wall does as the parietal pleural membrane is attached to the chest wall. The parietal pleural membrane and visceral pleural membrane are stuck together, there is a negative pressure in-between the two. There is fluid between the two membranes which cause them to stick together. This means that the lung automatically moves with the chest wall and the diaphragm. The parietal pleural membrane has lots of pain receptors on it which means it is very pain sensitive. However, there are no tissues in between the two membranes and if air gets in between the two a potential space will be converted into an actual space and the two membranes will be torn apart. Air in the pleural space is known as a pneumothorax. Infection in the pleural membranes causes inflammation which is very painful.

What are the main functions of the respiratory system?

• Provides gas exchange.
• Helps to regulate blood PH.
• Contains receptors for sense of smell.
• Filters inspired air.
• Produces sounds.
• Excretes small amounts of water and heat.

What is the basic structure of the alveoli?

Bronchioles have alveoli in their walls. The alveoli increase the surface area of the bronchioles. A terminal bronchiole turns into a respiratory bronchiole, as this is the first time that the walls have been thin enough to allow gaseous exchange. The respiratory bronchiole ends in clusters of alveoli forming air sacs, these alveoli allow a large internal surface area. The alveoli are elastic and therefore take effort to inflate but no effort at all to deflate. The air then goes out of the alveoli in the process of expiration, meaning air goes in and out of the alveoli constantly meaning there is always a fresh supply of air into the air sacs. Approaching an alveoli is a branch of the pulmonary artery and this branch carries deoxygenated blood which is pumped from the right ventricle of the heart to the pulmonary arteriole to the alveoli.The blood approaching is low in oxygen but high in carbon dioxide.

Why does oxygen and carbon dioxide diffuse down the concentration gradient?

There is a higher concentration of oxygen in the alveoli air than in the blood meaning oxygen moves down the diffusion gradient and into the blood where the oxygen becomes associated with haemoglobin. This means the blood leaving in the pulmonary vein will be high in oxygen. The concentration of carbon dioxide is higher in the blood than in the alveoli therefore the carbon dioxide diffuses down its concentration gradient from the blood where concentration is high into the alveoli where its lower.

What is the basic rhythm of respiration controlled by?

Groups of neurons in the brain stem. The nerve area from which nerve impulses are sent to respiratory muscles is called the respiratory centre and consists of neurons in the medulla onlongata and the pons.