ANATOMY AND PHYSIOLOGY
OF RESPIRATORY SYSTEM
Ari Titin Mulyaningsih, 2010
(English in nursing-midwifery science and technology, Nursalam)
The respiratory system is situated in the thorax, and responsible for gaseous exchange between the circulatory system and the outside world. Air is taken in via the upper airways (the nasal cavity, pharynx, and larynx) througt the lower airways (trachea, primary bronchi, and bronchial tree) and into the small bronchioles and alveoli within tissues.
The lungs are divided into lobes. The left lung is composed of the upper lobe, the lower lobe, and the lingual (a small remnant next to the apex of the heart) the right lung is composed of upper, the middle and the lower lobes.
Bronchi :The two main air passage into the lungs.
Diaphragm :The main muscle used for breathing, separates the cest cavity from abdominal cavity.
Epiglottis : A flap of cartilage that prevents food from entering the trachea.
Esophagus: The tube through which food passes from the mouth down into the stomach.
Heart : The muscular organ that pumps blood throughout the body.
Itercostal muscles: Thin sheets of muscle between each rib that expand (when air is inhaled) and contract (when air is exhaled).
Larynx: Voice box
Lungs: The two organ that extract oxygen from inhaled air and expel carbon dioxide in exhaled air.
Muscles attached to the diaphragm : these muscles help move the diaphragm up and own for breathing.
Nasal Cavity : Interior area of the nose, lined with a sticky mucous membrane and contains tiny surface hairs called cilia.
Nose hairs : Located at the entrance of the nose, these hairs trap large particles that are inhaled.
Paranasal sinuses : Air spaces within the skull.
Pharynx : The throat
Pleural membrane : Covering the lung and lining the cest cavity, this membrane has 2 thin layers.
Pulmonary vessels : Pulmonary arteries carry deoxygenated blood from the heart and lungs, pulmonary veins carry oxygenated blood back to the heart.
Respiratory center : Area of brain that controls breathing.
Ribs : Bones attached to the spine and central portion of the breastbone, which support the cest wall and protect the heart, lungs, and other organs in the cest.
Trachea : Tube through which air passes from the nose to the lungs (also know as the windpipe).
MECHANICS OF BREATHING
To take a breath in, the external intercostal muscles contract, moving the ribcage up and out. The diaphragm moves down at the same time, creating negative pressure within the thorax. The lungs are held to the thoracic wall by the pleural membaranes, and so expand outwards as well. This creates negative pressure within the lungs, and so air rushes in through the upper and lower airways. Expiration in mainly due to the natural elasticity of the lungs, which tend to collapse if they are not held against the thoracic wall.
Respratory has two meanings in biology. At the cellular level, it refers to the O2 requiring chemical reactions that place in the mitochondria and are the chief source of energy in the eukaryotic cells. At the level of the whole organism, it designates the procces of taking in O2 from the environment and returning CO2 to it.
Oxygen consumption is directly related to energy expenditure. Energy requirenment are usually calculated by measuring O2 intake or CO2 release. Energy expenditure at rest is known as basal metabolism.
DIFFUSION AND AIR PRESSURE
In every organism, from amoeba to elephant, gas exchange the exchange of O2 and CO2 between cells and the surrounding environment takes place by diffusion. Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration as a result of their random movement.
In describing gases, scientists speak of the pressure of a gas rather than its concentration. At sea level, air exerts a pressure of one (1) atm (15lb/in2). This pressure is enough to support a column of mercury 760 mm high.
DALTON’S LAW OF PARTIAL PRESSURE
The total pressure of a mixture of gases is sum of the pressure of the separate gases in the mixture. The pressure of each gas is propotional to its concentration. Oxygen makes up 21% of the composition of dry air, therefore 21% of the total air pressure or 160 mm of Hg result from the pressure of O2 (partial pressure of O2) designated as pO2 (if H2O is present) then pO2 = 155 mmHg.
If a liquid containing no dissolved gases is exposed to air at atmospheric pressure, each of the gases in the air diffuses into the liquid until the partial pressure of each gas in the liquid is equal to the partial pressure of the gas in the air. Oxygen pressure (pO2) of blood means the pressure of dry gas which the dissolved O2 in the blood is in equilibrium.
For example, blood with a pO2 of 40 mmHg would be in equilibrium with air in which the partial pressure of O2 was 40 mmHg. If blood with a pO2 of 40 mmHg was exposed to the usual mixture of air, O2 will move from the air to the blood until the pO2 = 155 mmHg.
Conversely, if a liquid containing a dissolved gas is exposed to air in which the partial pressure of that gas is lower than the liquid, the gas will leave the liquid until the partial pressure of the air and the liquid are equal.