Muscles of respiration-The course is designed for the basic understanding of anatomical structures and physiological functions of human body, musculoskeletal system, digestive system, respiratory system; cardiovascular system; urinary system, endocrine system, reproductive system, nervous system, hematologic system, sensory organs, integumentary system, and immune system.The aim of the course is to acquire knowledge and skills regarding anatomy and physiology.
Muscles of respiration
Muscles of respiration:-
- Muscles of inspiration (inflate the chest/rib cage):
A) In quite inspiration-
- The Diaphragm. (Accounts for 75% of quite inspiration)
- External intercostals
B) In forceful inspiration-
- The sternocleidomastoid muscle
- The scaleni
- The anterior serrati.
- Scalenus posterior.
- Latissimus dorsi
Muscles of expiration (deflate the chest cage):
A) In quite expiration: Does not involve any muscle
B) In forceful expiration:
- The abdominal recti. (the rectus abdominus, internal and external obliques, and transversus ubdomumus)
- The internal intercostals.
(Ref: Guyton & Hall 11/471+ Stuart Ira Fox, 12th edition, p-534)
Lung Volumes and Capacities
While at rest, a healthy adult breathes about average 12 times a minute, with each inhalation and exhalation moving about 500 ml. of air into and out of the lungs. breath is called the tidal volume The volume of one
The Pulmonary ventilation /The minute ventilation (MV) the total volume of air inhaled and exhaled each minute is equal to breathing rate multiplied by tidal volume
MV =12 breaths/min X 500 ml/breath
= 6000 ml/min or 6 liters/min
Vital capacity:
The maximum amount of air that a person can be expired forcefully after the forceful inspiration is called vital capacity
Vital capacity = Inspiratory reserve volume + tidal volume + expiratory reserve volume
Normal amount: About 4600ml
Measurement: it is measured by spirometer.
A. The pulmonary “volumes” are:
1) Tidal volume About 500ml.
2) Inspiratory reserve volume: About 3000 mi
3) Expiratory reserve volume About 1100 ml
4) Residual volume: About 1200 ml.
The pulmonary “capacities” are:
1) Inspiratory capacity: About 3500
(eg:- Inspiratory capacity TV+ IRV500+3000 = 3500 ml)
2) Functional residual capacity: About 2300 ml.
(eg: Functional residual capacity = ERV+RV=1100+1200-2300 ml)
3) Vital capacity: About 4600 ml
(eg: Vital capacity IRV TVERV 3000+500+1100=4600 ml).
4) Total lung capacity: About 5800 ml.
(eg:- Total lung capacity VCRV-4600+1200-5800 ml)
(N.B: All pulmonary “volumes” and “capacities” are about 20-25% less in female than in male)
(Ref– K. Indu, 1 ed P-230+ Guyton & Hall, 12, P-475)
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