Resp Lecture 2 Flashcards
Why is wrong with the drawings in the book of an alveolus
the volume of the alveolar air space is greatly reduced, and the thickness of the squamous pneumocytes and the capillary endothelial cells is exaggerated.
Cartilage supports the large airways during inspiration, but does not continue beyond
the smallest bronchi. Mucous glands stop there too.
Thickness of the epithelium decreases as
airway diameter decreases.
The epithelium of the conducting airways contains secretory cells. Goblet cells secrete
mucus in the large airways, Club cells release a serous (watery) secretion in bronchioles.
Small airways have more smooth muscle (in spiral orientation) in relation to their size than
large
ones, but the muscle coat does not continue beyond the smallest bronchioles.
Subdivisions of the lung
• Primary bronchi (2) are
right and left main stem bronchi supplying each lung.
Secondary bronchi are
lobar bronchi supplying lobes (2 on the left, 3 on the right).
Tertiary bronchi are segmental bronchi supplying
segments of the lung (8 on the left, 10 on the
right). Each segment has its own air and blood supply.
Each segment has its own air and blood supply. Thus when a localised tumour occurs in
the lung, a surgeon who
knows the approximate boundaries can remove one or more segments
containing the tumour without excessive leakage of air or blood from neighbouring segments.
The lung is divided into
ten bronchopulmonary segments, each segment being supplied by a segmental (= tertiary) bronchus
Pleurae
• A smooth membrane (pleura) covers
each lung; and also lines the thoracic cavity in which
the lung sits. The two membranes (pleurae) are continuous at the root of the lung (hilum).
Although the fluid allows sliding movement between the pleurae, it also prevents them
from being separated. When the thoracic wall
moves inwards
inwards or outwards, the lungs must
follow. Similarly when the diaphragm moves
upwards or downwards, the lungs must follow.
Quiet breathing: • Movement of the ribcage is responsible for
about 25% of air movement into and out of the lungs.
Inspiration is active. It requires contraction of the external intercostal muscles which run
obliquely between ribs.
Expiration is
passive. The ribcage returns to its resting position without requiring muscular
action.
Breathing during exercise:
Both sets of intercostal muscles are now active; externals for inspiration, internals for expiration.
Ventilation: movement of the diaphragm floor and roof
The diaphragm is a dome-shaped platform which forms the loor of the thorax and the roof of the abdomen.
Ventilation: movement of the diaphragm
Its central part is a thin sheet of connective tissue, (technically an aponeurosis) called the central tendon. The lateral margins are muscular. The muscle is fast-acting skeletal muscle, innervated by the phrenic nerve.
Contraction of the diaphragmatic muscle
lattens the diaphragm, pulling its central
dome downwards. This
increases the volume
of the thorax and causes inspiration.
Passive relaxation of the muscle allows the
diaphragm to lift back towards
the thorax,
reducing thoracic volume, (expiration).
Movement of the diaphragm is responsible
for
75% of bulk low of air during quiet
breathing, a smaller proportion during
exercise.
Club cells secretions =
Water H2O with anti microbial enzymes
Asthma
Rapid bronchi constraint swollen tubs
Asthma treatment
Puffer brondilater =relaxation of smooth
Salbutamol - Ventolin
