4. Respiratory System Flashcards
Functions of the Respiratory System
- Gas exchange: Oxygen (O2) & Carbon dioxide (CO2).
O2 is required for cell respiration.
CO2 is a waste product of cell respiration.
By breathing, we are able to inhale O2 and exhale CO2. - Warming or Cooling and Moistening of air.
- Removal of inhaled particles (immunity):
Removal of larger substances in nose.
Smaller substances by mucociliaryescalator.
Alveolar macrophages in alveoli. - Voice production and olfaction (smell).
Types of Respiration
- External respiration
- Internal respiration
- Cellular respiration
External Respiration
- Exchange of gases between the blood & lungs (air).‘Pulmonary capillaries’ carry blood around alveoli.
- Air is inhaled and exhaled -this is called‘ventilation’.
Internal Respiration
Exchange of gsaes between blood & cells
Cellular Respiration
Metabolic process whereby energy (ATP) is obtained by metabolising carbohydrates, fats & proteins.
Respiratory Tract Mucous Membrane
- The respiratory tract is lined with a mucous membrane. This is a ciliated epithelial membrane that contains mucous-secreting goblet cells.
- Mucus traps inhaled particlesand acts as a surfactant (lowers the surface tension of a liquid, allowing easier spreading). It also has antimicrobial properties.
- Cilia move the trapped particles towards the oesophagus where they can then be swallowed, thus protecting the lungs from inhaled pathogens. This mechanism is called the mucociliary escalator.
Nose & Nasal Cavity
- The nasal cavity is the first contact organ in the respiratory system and ‘conditions’ air.
- It is an irregular cavity, divided by a septum (cartilage). Bordered posteriorly by skull bones.
- The nasal cavity contains hairs that trap larger particles.
- Internally has 3 nasal concha (‘turbinates’) –shelves that increase surface area and trap water during exhalation’.
- Contains olfactory receptors (interpret smell).
- Internal nose lined by mucous membrane and capillaries
Nasal Cavity Functions
- Filtering air:
• Hairs (larger particles) & cilia/mucous (trap smaller particles, protect epithelium, cilia beat towards mouth).
• Nasal concha (turbinates) spin air within the nasal cavity, which filters air and encourages particles to become trapped in the mucous. - Warming air -strong vascularity of mucosa .
- Humidification-air travels over moist mucosa.
- Sneezing reflex –if case of mucosal irritation.
- Olfactory function -olfactory receptors.
Paranasal Sinuses
- The paranasal sinuses are air filled cavities within certain facial and cranial bones.
- They are lined with mucous membranes that are continuous with the nasal mucosa lining. Secretions drain into nasal cavity.
- Includes: frontal, ethmoid, sphenoid, maxillary.
Paranasal Sinuses - Functions
The sinuses perform the following functions:
- Resonance in speech.
- Lighten cranial mass.
- Nasolacrimal ducts drain tears from the eyes.
- Moisten/humidify the air.
Pharynx
- The pharynx is a straight muscular tube that connects the nose & throat.
- The pharynx is roughly 13cm long and sits anterior to the cervical spine, terminating at the larynx.
- Consists of the nasopharynx, oropharynx & laryngopharynx.
- The pharynx contains the ‘eustachian tubes’, which connect the nasopharynx to the middle ear and allow equalisation of pressure in the middle ear.
- Contains adenoids (‘nasopharyngealtonsils’).
Pharynx - Functions
- Passagewayfor air & food.
- Warmingand humidifying.
- Taste.
- Hearing.
- Equalisation of pressure in middle ear (eustachian tubes).
- Immune protection: tonsils.
- Speech: resonating chamber.
Larynx
- The larynx is also known as the voice box (Adam’s apple) and connects the laryngopharynx with the trachea.
- Consists of 9 pieces of cartilage (including the thyroid cartilage & epiglottis) and vocal cords.
- The vocal cords are composed of mucous membrane foldings stretched horizontally.
- Laryngeal muscles attach to the vocal cords and when contracted stretch them:
- Relaxed muscles = loose cords = low tone
- Contract muscles = tight cords = high tone (vibrate rapidly).
Larynx - Functions
- Production of sound (vocal cords) & speech (tongue, lips & cheeks).
- Protection–the ‘epiglottis’ closes off the trachea during swallowing and hence prevents food entering the lungs.
- Air passageway.
- Warming & humidifying.
Trachea
- The trachea (or “windpipe”)is roughly 12 cm long and is made of incomplete C-shaped rings of hyaline cartilage.
- The incomplete rings of cartilage are connected by smooth muscle, which is called “trachealis”.
- Sympathetic (‘fight or flight’) response tracheal dilation.
- Parasympathetic (‘rest & digest’) response tracheal constriction.
Trachea - Functions
- Air flow: rings keep trachea open and unobstructed.
- Mucociliary escalator: trapping inhaled particles and removing them from the respiratory tract.
- Cough Reflex.
- Warming, humidifying, filtering (it is usually warm and humid by this point).
Bronchi
- The trachea divides into left and right bronchi at the vertebral level of T5.
- The bronchi deliver air into the lungs.
- Bronchi contain cartilage rings that maintain an open airway. Bronchi are lined with ciliated epithelium.
- The right bronchi is more vertical, shorter and wider. Hence an aspirated object is more likely to enter the right lung.
- Where the trachea divide into the two bronchi, an internal ridge called the carina is formed (this is the most sensitive structure in the system and triggers cough reflex).
Bronchioles
• The bronchioles are continuations of bronchi.
• Bronchioles have no cartilage in their structure and instead contain more smooth muscle.
• The bronchioles lead directly into the alveoli, where gas exchange occurs.
Control of air-entry via:
• Sympatheticnervous system (SNS: “fight or flight”) = Bronchodilation.
• Parasympathetic nervous system(PSNS: “rest & digest”) = Bronchoconstriction.
Alveoli
• Alveoli are small hollow cavities that make up most of the lung volume.
• The bronchioles terminate into alveolar sacs.
• Alveoli are the sites of gas exchange in the lungs.
• Alveolar gas exchange is maximised by the following:
A large surface area (approximately 80m2) created by 250 million alveoli in each lung.
Alveolar walls are very thin (single-layered).
Surrounded by many blood capillaries.
Alveolar surfaces are moist(gases exchange more easily when in water).
Alveolar Cells
Type I alveolar cells:
• These are simple epithelial cells, covering 90% of the alveolar surface and are very thin to support gas exchange.
Type II alveolar cells:
• Secrete ‘alveolar fluid’ that contains ‘pulmonary surfactant’.
• Pulmonary surfactant reduces alveoli surface tension, preventing alveolar collapse.
• The fluid allows gases to diffuse through it.
Alveolar Macrophages:
• These are strategically located white blood cells (leukocytes) that engulf and destroy microbes entering the alveoli.
Pulmonary Surfactant
• Surfactant is a mixture of lipids and proteins
that forms a surface film in alveoli.
• The protein part is hydrophilic and resides in the alveolar fluid, whilst the lipid component is hydrophobic and faces the air.
• Through this structure, surfactant reduces the surface tension within the alveoli, preventing them from
collapsing and reducing the pressure required to re-inflate them.
• Surfactant is not produced until 34 weeks gestation, so consider lung development in a premature baby.
• Two thirds of the work of breathing is to overcome surface tension.
Lung Anatomy
• 2 cone shaped lungs, separated by the heart. Surfaces: • Apex (extends above clavicle!) • Base (over diaphragm). • Costal (rib) surface. • Medial surface.
Lobes:
• Right lung: 3 lobes.
• Left lung: 2 lobes (due to the heart).
Blood supply:
• From the pulmonary artery (left & right).
Pleura & Pleural Cavity
- The pleura is a serous membrane that surrounds the lungs.
- The pleura contains a visceral and parietal layer, with a ‘pleural cavity’ in between.
- The visceral & parietal pleura form a double layer separated by 5-10ml of serous fluid that prevents friction.
- The pleura adhere to the lungs so that the lungs are sucked to the pleura(‘passive dilation’) -helps expansion of the lungs.
- A pneumothorax occurs when the pleura is damaged and air enters the pleural cavity.
Muscles of Ventilation: Primary
Intercostal muscles(internal & external):
• Attached between ribs at right angles.
•Contraction pulls ribs upwards(inspiration) expanding outward & increasing size of rib cage.
Diaphragm:
• Attached to the lower ribs, sternum & lumbar spine.
•A domed muscle that separates the thoracic & abdominal cavity.
• Contraction moves the diaphragm into the abdomen and draws air into the lungs.