Respiratory System

F: to supply the body with oxygen and rid it of carbon dioxide. This is done through respiration (4 processes; first 2 are part of resp. system).
1. Pulmonary Ventilation: air in/out of lungs so gases are continuously changed/refreshed; called breathing.
2. External Respiration: movement of oxygen in lungs to the blood, and carbon dioxide from the blood to the lungs.
3. Transport of respiratory gases: transport of oxygen in lungs to body tissue cells, and of carbon dioxide in tissue cells to the lungs (happens through the cardiovascular system; uses blood).
4. Internal respiration: movement of oxygen in the blood to the tissue cells, and of carbon dioxise in the cells to the blood.

The respiratory and circulatory systems
If one system fails, the body cells begin to die from oxygen starvation.
Respiratory system: moves air; associated w/senses of smell/speech.
Cellular respiration: use of oxygen and production of CO by tissue cells. Cornerstone of all energy-producing chem. rxns in the body.

There is an external portion (made up of the nasal & frontal bones superiorly, maxillary bones laterally, and hyaline cartilage inferiorly) as well as an interal nasal cavity (in and posterior to the external nose; divided by a midline nasal septum and lined with mucosa.
F: provides an airway for respiration; filters, moistens, and warms entering air; a resonating chamber for speech; and houses olfactory (smell) receptors in the roof of the nasal cavity.
Roof: formed by ethmoid and sphenoid bones of skull
Floor: formed by the hard (supported by bones) and soft (unsupported) palates; separates the nasal from the oral cavity.
Vestibule: lined with sweat and sebaceous glands, as well as hair follicles; just superior to the nostrils.
Vibrissae: hairs; filter coarse particles.
2 Types of Mucosa: 1) Olfactory epithelium mucosa: lines the slitlike superior region of the nasal cavity; contains smell receptors. 2) Respiratory mucosa: pseudostratified ciliated columnar epithelium; scattered goblet cells; mucuous and serous glands, secreting mucus and water fluid w/enzymes (about 1L a day, trapping dust, etc. while lysozyme destroys the bacteria chemically). All of the mucosa are rich in sensory nerve endings and contact w/particles triggers a sneeze, which expels the irritants.
Rich plexuses of capillaries/veins under the nasal epithelium: when cold air comes in, they are filled with blood to heat it. Inhaled air cools the conchae, exhaling makes these conchae precipitate moisture and extract heat from the humin air flowing over them (minimizes amount of moisture and heat lost from the body through breathing).

Surround the nasal cavity in a ring
Mucosa-lined, air-filled cavities in cranial bones surrounding the nasal cavity.
F: lighten the skull, and together w/the nasal cavity, tehy warm & moisten the air. Produce mucus which flows into the nasal cavity.
Nose blowing helps drain the paranasal sinuses.

Connects the nasal cavity to the larynx and oral cavity to the esophagus. Called the throat. Divided into 3 regions. Wall is composed of skeletal muscle.
F: passageway for air and food
Nasopharynx: only serves as a air passageway. When swallowing, the soft palate and uvula close off this pharynx, preventing food from entering the nasal cavity. Pseudostratified ciliated epithelium. Pharyngeal tonsil on its posterior wall to trap and destroy pathogens entering in air.
Oropharynx: both swallowed food and air pass through it; it's posterior to the oral cavity. More protective, stratified squamous epithelium. Palatine tonsils in the lateral wall mucosa, and lingual tonsil on posterior surface of tongue.
Laryngopharynx: passageway for food and air, lined with stratified squamous epithelium. Posterior to the epiglottis, and extends to the larynx where the respiratory and digestive pathways converge. Continuous with esophagus.

Voice box; attaches to hyoid bone superiorly, opening into the laryngopharynx; inferiorly it is continuous with the trachea.
F: Air passageway (provides an open airway and acts as a switching mechanism to route air and food into proper channels) and voice production.
9 cartilages connected by membrans (8 hyaline, and the elastic epiglottis). Laryngeal prominence: Adam's apple; more prominent in males than females bc of male sex hormone stimulation.
Epiglottis: guardian of the passageways; open when air is flowing into the larynx, and closes this space off when food is being swallowed. Anything other than air entering the larynx produces the cough reflex.
Vocal folds: lack b.v.'s, vibrate and produce sounds as air rushes up from the lungs. These and the air space between them=glottis.
Vestibular folds: no direct part in sound production, help to close the glottis when we swallow.
Speech: expired air and opening/closing of the glottis. Pitch of the sound varies as the length and tension of vocal folds change. Tenser=faster they vibrate=higher pitch. Boys voices become deeper as their vocal folds become thicker/longer (vibrate more slowly). Loudness=force of air across the folds. Good enunciation and resonance depend on superior structures: pharynx, oral, nasal, and sinus cavities.
Laryngitis: inflammation of the vocal folds; overuse of voice, dry air; change in tone, can't speak above whisper.

Windpipe; very flexible and mobile.
F: air passageway; cleans, warms, and moistens incoming air.
Descends from larynx, through neck, into mediastinum.
Divides into two main bronchi at midthorax.
Mucosa: goblet cells, pseudostratified epithelium. Propels mucus towards the pharynx.
Submucosa: CT layer deep to the mucosa, contains seromucus glands to produce mucus sheets in the trachea. Supported by 16-20 C-shaped rings of hyaline cartilage.
Adventitia: outermost CT layer.
Carina: point where trachea branch into 2. Highly sensitive mucosa
Heimlich maneuver: done when choking on food occurs from closage of the trachea.

Site where conducting zone structures give way to respiratory zone structures.
F: air passageways connecting trachea w/alveoli; cleans, warms, and moistens incoming air.
Conducting: left and right main bronchi from trachea. Each enter a lung on one side. Both branch into lobar (secondary) bronchi (3 on right, 2 on left). Each of the seconday bronchi supply a lung lobe. Tertiary bronchi then divide further and further. Bronchioles=passages smaller than 1 mm in diameter, smallest of the bronchi.
-As conducting tubes become smaller, structural changes occur: support structures change (cartilage is replaced, elastic found throughout), epithelium type changes (thins), and the amount of smooth muscle increases.
Respiratory: these are within the lung; begin as the terminal bronchioles enter the lungs; have the presence of thin-walled air sacs called alveoli (site of gas exchange).

F: gas exchange
Very thin walls; single layer of squamous epithelial called type 1 cells, with a flimsy basement membrane surrounding them. Also a cobweb of pulmonary capillaries on their external surfaces. All of this makes up the = respiratory membrane.
R.M. = air-blood barrier that has gas on one side and blood flowing past on the other. Gas exchange occurs through simple diffusion. O2 leaves alveolus to blood, CO2 enters the alveolus.
Also Type 2 cells which secrete a fluid containing detergent-like substance called surfactant, coating the gas-exposed alveolar surfaces (helps prevent lung collapse).
Surfaces are usually sterile, sweeping away macrophages easily.

Paired; surrounded by pleurae; connected to mediastinum by the root; differ slightly in shape/size, left smaller than right and contains a cardiac notch; left has two lobes (oblique fissure) and right has 3 (oblique and horizontal fissures).
Lobules: smallest subdivisions visible with eye; at lung surface as hexagons; each served by a large bronchiole and its branches.
Stroma: lung tissue; elastic CT; makes lungs soft, spongy, elastic organs, just over 1 kg, reducing the work of breathing.
Two circulations: pulmonary and bronchial. Pulmonary arteries: deliver systemic deoxygenated blood to the lungs
Pulmonary Veins: give oxygenated blood from the respiratory zones of lungs to the heart.
Bronchial Arteries: provide oxygenated systemic blood to the lung tissue (except alveoli).
All of body's blood passes through the lungs about once a minute.

Thin, double-layered serosa; parietal (covers thoracic wall & sup. face of diaphragm) and visceral (covers lung surface).
F: produces pleural fluid, filling the cavity between them, and allowing them to slide easily over thorax wall during breathing.
Lungs cling tightly to thorax wall, so as volume of thoracic cavity increases/decreases, the lungs are forced to expand/recoil.

P(atm): pressure exerted by the air (gases) surrounding the body.
Respiratory pressures are always described relative to it.
760 mm Hg at sea level. 760 mm Hg = 1 atm
Negative resp. pressure, is lower than the atm. pressure by that many units, posit. resp. pressure is higher, and zero resp. pressure is equal to atm. pressure.

P(pul): intra-alveolar; the pressure in the alveoli.
Rises and falls with the phases of breathing, but it always eventually equalizes with the atm. pressure.

P(ip): fluctuates with breathing phases, but is always about 4 mm Hg less than P(pul) (always negative compared to it).
Why does this happen?
-two forces act to pull the lungs (visceral pleura) away from the thorax wall (parietal pleura) and cause lung collapse: 1) lungs' have a natural tendency to recoil. They have elasticity, making them assume the smallest size possible. 2) the alveolar fluid produces surface tension, because the molecules of fluid attract each other and want to draw the alveoli to their smallest possible size.
-These lung-collapsing forces are opposed by the natural elasticity of the chest walls (pulling the thorax outward and enlarging the lungs).
Neither of these forces win in a healthy individual (because of the closeness of the pleura), but the net result of the dynamic interplay bt the forces is a neg. P(ip).
Amount of pleural fluid must remain minimum for the neg. P(ip) to be maintained (if it didnt move out, it would accumulate, creating a pos. P(ip)).

Difference between the intrapulmonary and intrapleural pressures
P(pul)-P(ip)
Keeps the lungs from collapsing; collapse occurs if these two pressures are equalized.
Greater the transp. pressure, the larger the lungs.