28 - lower respiratory system Flashcards
(29 cards)
what are the structures of the lower respiratory system?
The lower respiratory system consists of the trachea, bronchi, bronchioles and lungs.
where is the trachea located?
The trachea extends from the larynx to the upper border of the T05 vertebra, where it branches into the bronchi.
what is the trachea supported by?
a series of C-shaped cartilaginous rings, which enable the smooth muscle of the trachea to change shape and accommodate masses of food passing though the oesophagus.
what four layers does the trachea wall consist of?
- the inner mucosa
- submucosa
- hyaline cartilage
- outer adventitia
why does each layer of the trachea have a connective tissue component, rich with elastic fibres?
Each layer has a connective tissue component, rich with elastic fibres that allow the lumen of the trachea to expand and recoil during inhalation and exhalation.
what prevents tracheal collapse?
Stacks of C-shaped hyaline cartilage rings, located between the submucosa and adventitia, prevent tracheal collapse.
The posterior openings of the cartilage rings are connected by transvers smooth muscle fibres, which form the trachealis muscle.
what is crania?
A ridge of cartilage, called the crania, marks where the trachea divides into two primary bronchi that enter the lungs.
what does the inner mucosa layer of the trachea wall consist of?
The inner mucosa consists of pseudostratified ciliated columnar epithelium and the underlying elastic lamina propria.
what do goblet cells in the epithelium do?
Goblet cells in the epithelium secrete mucus that traps inhaled particles, the cilia move the mucus with trapped particles toward the pharynx for removal.
what does the submucosa layer consist of?
The submucosa consists of areolar connective tissue with seromucous glands
Deep to the submucosa are C-shaped hyaline cartilage rings that are connected by transverse smooth muscle fibres and connective tissue.
what is the outer layer of the trachea wall?
The outer layer of the trachea wall is the adventitia, which consists of areolar connective tissue.
what does the trachea do?
The trachea conveys air between upper and lower respiratory structures. This flexible tube extends from the larynx to the upper chest, where it divides into the bronchi.
what do the C-shaped rings do?
Between 15 and 20 cartilaginous C-shaped rings keep the trachea from collapsing or over expanding. The shape of these cartilaginous rings allow the trachea to change shape to accommodate masses of food passing through the esophogus
what can the smooth muscle of the trachea do?
The smooth muscle of the trachea can contract to decrease its diameter.
This allows air to be expelled out of the lungs more forcefully during coughing.
what does the trachea divide into?
The trachea divides into the bronchi and bronchioles in the lungs
what does relaxation of smooth muscle in the bronchioles during exercise do?
Relaxation of smooth muscle in the bronchioles during exercise caused them to dilate - this bronchodilation allows greater ventilation.
what do allergic reactions and histamines cause?
Allergic reactions and histamines cause the opposite effect, of bronchodilation, known as bronchoconstriction.
where are the lungs located?
- The lungs are located inside the thoracic cage.
- The left lung is slightly smaller than the right lung because it curves inward to accommodate the heart (this curve is called the cardiac notch).
- The right lung is slightly shorter than the left because the diaphragm rises below it to cover the liver.
what are the three lobes of the right lung?
- superior lobe
- middle lobe
- inferior lobe
what are the two lobes of the left lung?
- superior lobe
- inferior lobe
why does lung tissue have a lacy appearance?
lung tissue has a lacy appearance because its many air sacs are lined with simple squamous epithelium, supported by a thin elastic basement membrane. This this epithelial layer facilitates the diffusion of oxygen from the alveoli into the surrounding capillaries and carbon dioxide from the capillaries into the alveoli. Compare this to thick stratified squamous epithelium in the skin, which forms a protective barrier against pathogens and cushions underlying structures from abrasion.
how do the pulmonary vessels and bronchi enter each lung?
through the hilum.
what is the bronchial tree?
The airways branching from the trachea form the bronchial tree. Primary bronchi divide into the secondary and tertiary bronchi in the lungs, which divide further into small bronchioles and culminate in alveoli where gas exchange occurs.
what happens as the bronchial tree branched get smaller?
As the bronchial tree branches get smaller, several structural changes occur. The mucosal epithelium gets thinner - the bronchi have pseudostratified ciliated columnar epithelium and as the bronchioles get smaller, they go from ciliated simple cuboidal epithelium.
Additionally, the amount of cartilage around the tube decreases, going from incomplete rings to irregular plates to no cartilage in the bronchioles. As the amount of cartilage decreases, the amount of smooth muscle tissue increases to support the bronchioles.
