respiratory system

primary function of the respiratory system

to deliver O2 to cardiovascular system and remove CO2 from the body (gas exchange)

other functions of the respiratory system

produce sound; provide olfactory sensation; regulate blood pH; protect respiratory surfaces from dehydration, temp changes and invasion of pathogens

structural divisions

upper respiratory system and lower respiratory system

functional divisions

conducting zone (series of interconnected cavities and tubes) and respiratory zone (main sites of gas exchange between air and blood)

respiratory epithelium

pseudostratified ciliated columnar epithelium with goblet cells; mucus glands and serous glands present

role of goblet cells

produce mucus to trap dust and inhaled particles

role of ciliated cells

move mucus towards the pharynx

function of stratified epithelium

protects against abrasion (oropharynx and laryngopharynx)

simple squamous epithelium

single cell layer to facilitate diffusion for gas exchange (alveoli)

what does the upper respiratory tract consist of

nasal cavity, paranasal sinuses, pharynx, and larynx

nasal cavity structure

nares > choanae (opening to the pharynx), shape is defined by bones, divided into two sides by nasal septum with cartilage at the front and bone at the back

what lines the the nasal cavity

respiratory epithelium which is rich in blood vessels

nasal cavity function

warms, humidifies & filters air; olfaction; contributes to voice sound

rhinitis

infection of nasal mucosa - can be caused by viruses or bacteria, allergy, or chemical irritants

paranasal sinuses structure

open into nasal cavity; lined with mucous membrane; named by which bone they are located in

paranasal sinuses functions

reduce skull weight; enlarge volume of nasal cavity; modify resonance of voice

sinusitis

inflammation of the paranasal sinuses, often accompanies rhinits - mucus blocks passageway for sinuses to drain into nasal cavity

pharynx

common opening for digestive and respiratory systems; three sections - nasopharynx, oropharynx, laryngopharynx

nasopharynx

posterior to nasal cavities, superior to soft palate; air passes through it

oropharynx

from soft palate to epiglottis; air, food and liquids pass through it

laryngopharynx

from epiglottis to oesophagus; air passes through it

pharynx structure

walls made of skeletal muscle - circular and longitudinal muscle layers - relaxed muscle helps to keep it patent and contraction assists swallowing; lined by mucous membrane

what is the epithelium of the nasopharynx

respiratory epithelium

what is the epithelium of the oropharynx and laryngopharynx

stratified squamous epithelium

pharynx functions

airflow; swallowing; immune system (pharyngeal tonsil); contributes to sound/speech; auditory tube opens into nasopharynx

pharyngitis

inflammation of the throat - typically a viral or bacterial infection

larynx structure

larynx structure

anterior part of throat; connected to hyoid bone by membranes & muscles; outer casings of 9 cartilages connected by muscle/ligaments; lined by mucous membrane; above vocal folds lined by stratified squamous epithelium; below lined by respiratory epithelium

larynx: cartilages

6 paired and 3 unpaired cartilages; unpaired = thyroid, cricoid & epiglottis; paired = arytenoid, corniculate & cuneiform; all hyaline cartilage except epiglottis which is elastic cartilage; arytenoids anchor vocal cords

larynx functions

gateway to lower respiratory tract; controls flow of air but prevents entry of solids/liquids; speech via vocal cords

what does the tracheobronchial tree consist of

trachea, bronchi and bronchioles

role of cartilage and smooth muscle on the tracheobronchial tree

cartilage keeps it open and smooth muscle regulates the diameter of the airways to control airflow

trachea structure

approx 10-12cm; attached to larynx; dense connective tissue & smooth muscle; reinforced with C-shaped cartilages; begins below cricoid cartilage; ends by bifurcating at carina; oesophagus lies directly posterior

role of CT and smooth muscle on the trachea

protects trachea, maintains open airway

structure of bronchi

Lower end of the trachea bifurcates (divides) into two primary bronchi, one on the right and one on the left; branches into secondary bronchi in the lungs, then into tertiary bronchi, finally ending in bronchioles

primary bronchi

asymmetric - right bronchi is steeper, wider and shorter than left; foreign bodies are more likely to go into and obstruct right bronchus; has cartilage rings to keep airway patent (open)

secondary (lobar) bronchi

2 on the left, 3 on the right; each one supplies a specific lobe; supported by plates of hyaline cartilage

tertiary (segmental) bronchi

each bronchus serves a distinct bronchopulmonary segment; cartilage decreases and smooth muscle increases to allow for more flexibility in smaller airways

bronchioles

walls lack cartilage and are dominated by smooth muscle; branch into terminal bronchioles

terminal bronchioles

end of conducting zone, lined by a single layer of simple ciliated cuboidal epithelium, branch into respiratory bronchioles

respiratory bronchioles

start of respiratory zone, smooth muscles replaces cartilage in keeping airway patent

lining of tracheobronchial tree

ciliated pseudostratified columnar epithelium - mucus and cilia sweep airways to protect lungs from dirt and infections

alveoli

air-filled chambers for gas exchange located at the ends of bronchioles

alveoli structure

thin walls composed of 2 cell types: type 1 - squamous epithelial cells (gas exchange), makes up around 90%; type 2 - cuboidal secretory epithelial cells (produce surfactant to keep alveoli open

gas exchange

exchange of O2 and CO2 between alveolar walls and pulmonary capillaries

what is efficient gas exchange facilitated by

thin alveolar epithelium, thin basement membrane, thin capillary endothelium, thin layer of surfactant lining alveolus - allows oxygen to dissolve , dense network of pulmonary capillaries, large surface area of alveoli

structure of lungs

right lung larger than left; conical shape; located in thorax, in upper ribcage; separated by mediastinum (heart, great blood vessels, esophagus); base rests on diaphragm, apex (top of lungs) extends 2.5cm above clavicle; surrounded by pleural cavity formed by pleural serous membranes

pleura

thin layer of tissue that covers the lungs and lines interior wall of chest cavity; protects and cushions lungs

visceral pleura

lines surface of lungs

parietal pleura

covers inner surfaces

pleural fluid

fills cavities; acts as lubricant to reduce friction; holds parietal and visceral membranes together; holds lungs to thoracic wall

hilium of the lung

root of lung; contains main bronchi, pulmonary arteries & veins, lymph nodes & lymph vessels; gateway to lungs for air and blood; anchors lungs to mediastinum

lobes of lungs

fissures subdivide lungs into lobes, right has three and left has 2 due to cardiac notch, supplied by lobar bronchi

subdivision of lobes

subdivided into broncho-pulmonary segments; segments are supplied by segmental bronchi

inspiration

2 phases - movement of ribs (costal breathing) and movement of diaphragm (diaphragmatic breathing)

costal breathing

shallow breathing, external intercostal muscles contract and lift ribs, total volume of ribcage increases

diaphragmatic breathing

downward movement of central part, chest volume increases, lungs extend to fill available space

tidal volume

amount of air that moves in and out of lungs with each normal breath, resting tidal volume is around 0.5L

vital capacity

total volume of air that can be exhaled after maximal inhalation, around 3-5.5L (differences between biological sexes and trained vs untrained individuals

muscles of inspiration

ribs are elevated so thoracic volume increases, diaphragm flattens and descends, pressure in lungs falls so air is drawn in

muscles of expiration

ribs move down and inward so thoracic volume decreases, diaphragm relaxes and moves upwards into dome shape, pressure in lungs increases above atmospheric pressure so air is pushed out