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Respiratory system
Oct. 19 2018 Lecture 6
Structures of the Pulmonary System
The primary function of the pulmonary system is to exchange gases between the external environment and the blood.
There are three steps in this process
- 1 Ventilation: movement of air into and out of the lungs
- 1 Diffusion: movement of gases between air spaces in the lungs and the bloodstream
- 2 Perfusion: movement of blood into and out of the capillary beds if the lings to body organs and tissues.
Respiration can be divided into four areas
- Breathing the movement of air into and out of the lungs
- External Respiration the exchange of O2 and CO2 between AIR and BLOOD
- Internal Respiration the exchange of O2 and CO2 between BLOOD and TISSUE FLUID
- Cellular Respiration the process which produces ATP in mitochondria --> requires O2 and releases CO
(^1) Carried out by the pulmonary system
(^2) Carried out by the cardiovascular system
Basic Anatomy
The pulmonary system includes:
Two lungs (divided into lobes- three in the right, two in the left)
The upper and lower airways
Blood vessels
The diaphragm
Thoracic cage
Mediastinum: Space between the lungs, contains the heart great vessels and esophagus.
Conducting airways called bronchi delivers air to each section of the lung, and is supported by the surrounding lung tissue to prevent collapse or change in conformation when air moves in and out during ventilation.
Diaphragm:Dome-shaped muscle that separates the thoracic and abdominal cavities and is involved with ventilation.
A variety of defense mechanisms protect the lungs from external contaminants, they are generally very effective so in a healthy individual, contamination of the lung tissue is rare.
Pulmonary defense mechanisms
Upper respiratory tract mucosa: Maintains temperature and humidification of gas entering the lungs; traps and removes foreign particles, certain bacteria and noxious gas in inspired air.
Nasal hairs and turbinates: Trap and remove foreign particles, certain bacteria and noxious gases in air.
Mucous blanket: Protects the trachea and bronchi from injury, traps most foreign particles and bacteria that reach the lower respiratory tract.
Cilia: Projects mucous blanket and trapped particles toward oropharynx, to be swallowed or expelled.
Irritant receptors in nares (nostrils): Trigger sneeze reflex when stimulated by chemical or mechanical irritants, removal of irritants from nasal passages.
Irritant receptors in trachea and large airways: Trigger cough reflex when stimulated by chemical or mechanical irritants, removes irritants from lower airways.
Alveolar macrophages: Ingest and remove bacteria and other foreign material from alveoli by phagocytosis.
Conducting Airways
- As the bronchioles continue to branch out, their walls get thinner and diameter smaller.
- Ending in sacs called Alveoli, which fill up much of the lungs.
Bronchial walls:
- Three layers
- Epithelial lining: contains single-celled exocrine glands, the mucous- secreting goblet cells (produces mucous blanket, protects the airway epithelium and the ciliated epithelial cells “rhythmically beat” the mucous toward the trachea and pharynx where it can be swallowed or expelled. and ciliated cells.
- Smooth muscle layer
- Connective tissue layer
Gas-Exchange Airways
The conducting airways terminate in the respiratory bronchioles, alveolar ducts and alveoli (sing. Alveolus). Together these thin-walled structures are called the 1 acinus , all of which participate in gas exchange.
Alveoli:
- Primary gas-exchange units of the lung, O 2 enters the blood and Carbon dioxide is removed
- Each alveolar sac is enclosed by a single layer of simple squamous epithelial tissue, which is surrounded by capillaries carrying deoxygenated blood.
- Gas exchange occurs between blood and air in alveoli.
- The ending of a tiny airway in the lung, where the alveoli (air sacs) are located (Medicine net)
- Lined with lipoprotein (surfactant) film to prevent them from collapsing when air leaves them.
- Pores of Kohn allow some air to pass through the septa from alveolus to alveolus, promotes 2 collateral ventilation and even distribution of air among the alveoli. ( The lungs contain approximately 25 million alveoli at birth and 300 million by adulthood)
- Small blood vessel or nerve that grows out of the main part (Cambridge dictionary)
Lung Epithelial Cells:
- Provide a protective interface with the environment- essential for adequate gas exchange, preventing foreign entry, regulation of ion and water transport, and maintaining mechanical stability of the alveoli.
- Type I alveolar cells provide structure
- Type II alveolar cells secrete surfactant , a lipoprotein that coats the inner surface of the alveolus and lowers alveolar surface tension at end-expiration thereby preventing lung collapse.
- Mononuclear macrophages ( alveolar macrophages) are responsible for ingesting foreign material and prepare it for removal via the lymphatic system.
COPD Vicious Cycle
Pulmonary Vascular Diseases- Hypertension
Pulmonary Artery Hypertension (PAH)
Cor Pulmonale
Respiratory Tract Infections
Bacterial Pneumonia
Viral Pneumonia
Tuberculosis
Extra
Cystic Fibrosis
Pulmonary Embolism
Pediatric Pneumonia
Sudden Infant Death Syndrome (SIDS)
