Chapter 9: Gas Exchange and smoking Flashcards
Where are the lungs located?
In the thoracic(chest) cavity
What is the name of the tube leading from the throat to the lungs?
Trachea
What is at the base of the trachea?
Two bronchi which subdivide and branch extensively to form smaller bronchioles. This forms a bronchial tree.
Describe the cartilage present in the trachea, bronchi and bronchioles
Trachea- Has regular C-shaped rings of cartilage
Bronchi- Has irregular blocks of cartilage
Bronchioles- Does not have cartilage
What is the function of smooth muscle in bronchioles?
The smooth muscle can contract or relax to adjust the diameter of these tiny airways. During exercise, the muscles relax to allow a greater flow of air to the alveoli.
What is mucus and how does it help?
Mucus is a slimy solution of mucin, which is composed of glycoproteins with many carbohydrate chains that make them sticky and able to trap inhaled particles.
What is mucus produced by in the trachea and bronchi?
The mucus is produced by the goblet cells of the ciliated epithelium. The upper part of the goblet cell is swollen with mucin droplets which have been secreted by the cell.
Mucus is also made by the mucous glands beneath the epithelium.
How does cilia help and where is it found?
Cilia is found in the trachea, bronchi and bronchioles. In the trachea and bronchi, ciliated cells can be found between goblet cells. The continual beating of the cilia carries the mucus upwards towards the larynx at a rate of about 1 cm/min When mucus reaches the top of the trachea it is usually swallowed so the pathogens are destroyed by the acid in the stomach.
What protects the surfaces of the nasal airways, trachea, bronchi, bronchioles?
- The hairs inside the nose help to trap particles
- The mucus helps to prevent unwanted particles from going further. It can also react with sulfur dioxide and nitrogen dioxide to form an acidic solution which can irritate the lining of airways.
- Phagocytic WBCs known as macrophages patrol the airways scavenging unwanted particles.
What do the elastic fibres in alveoli help with?
Elastic fibres allow the alveoli to stretch during inhalation and recoil during expiration. During maximum expansion through inhalation, surface area for diffusion increases and the air is expelled efficiently during recoil.
How does the wall of alveoli relate to its function?
Oxygen and carbon dioxide can diffuse quickly due to the close proximity of the capillaries as well as due to the thin walls, each consisting of a single layer of squamous epithelial cells no more than 0.5um thick.
What are the main components of cigarette smoke that pose a threat to human health and what system do they affect?
Tar which contains carcinogens affects the gas exchange system
Carbon monoxide and nicotine damage the cardiovascular system.
How is chronic bronchitis caused? ref. Infection
Tar in the cigarette smoke stimulates the goblet cells and mucous glands to secrete more mucus. Tar also inhibits the sweeping action of the cilia and destroys many of them. As a result, mucus accumulates in the bronchioles, of which some of the smallest may become obstructed. As mucus is not removed, dirt, bacteria and viruses collect and block the bronchioles. This stimulates ‘smoker’s cough’, which is an attempt to move the mucus upwards. Over time, the damaged epithelia are replaced by scar tissue and the smooth muscle surrounding the bronchioles and bronchi become thicker. This thickening of the airways causes them to narrow and makes it difficult to breathe.
Infections can develop in the accumulated mucus. When there is an infection, the linings become inflamed and this further narrows the airways. This damage and obstruction is called chronic bronchitis. Symptoms include having a severe cough, producing large quantities of phlegm(mucus, bacteria and WBCs).
What are some examples of COPD and what is COPD?
COPD is chronic obstructive pulmonary disease and some examples include asthma, chronic bronchitis and emphysema.
How is emphysema caused?
The inflammation of the infected lungs causes the phagocytes to leave the blood from the capillaries and line the airways. However, in order to do that, phagocytes release the protein digesting enzyme elastase. The enzyme destroys the elastin in the walls of alveoli which help with the recoil of the alveoli during expiration. With much smaller quantities of elastin in the walls of the alveoli, they do not recoil or stretch when breathing in or out. As a result the bronchioles collapse during expiration, trapping the air in the alveoli which often burst. Large spaces appear where the alveoli burst and this reduces the surface area for gas exchange. As the disease progresses, the blood vessels in the lungs will become more resistant to the flow of blood. To compensate for this increased resistance, the blood pressure in the pulmonary artery increases and the right side of the heart enlarges. This is known as emphysema
