Respiratory system

Anatomic divisions of respiratory system

• Upper respiratory tract — nasal cavity to pharynx

• Lower respiratory tracts — larynx to alveoli

Functional divisions of respiratory system

• Conducting portion

  • Runs from the nasal cavity to the terminal bronchioles

• Respiratory portion 

  • Runs from the respiratory bronchioles to the alveoli

Respiratory mucosa definition

The mucous membrane lining that lines the conducting portion of the respiratory system

Layers of the respiratory mucosa  

• Epithelial layer — outermost layer of pseudostratified columnar epithelium

• Lamina propria — areolar CT and mucous glands below epithelial layer

Parts of respiratory defensive system

• Filtration in nasal cavity with hair lining and twisted passageway (prevent entrances of harmful substances)

• Mucous layer that is secreted by mucous glands in lamina propria (traps harmful substances)

• Cilia — beat in coordinated rhythm to move mucous with trapped substance toward pharynx to be swallowed or coughed up

• Alveolar macrophages — present in alveoli and clear harmful substance from alveolar lumen

Air flow through upper respiratory tract (until nasopharynx)

• External nares (nostrils)

• Nasal vestibule 

  • Anterior region of nasal cavity containing hair

• Nasal chonchae

  • Produce air turbulence (disturbs smooth air flow and cause it to swirl) to trap inhaled particles in mucus 

• Internal nares

• Nasopharynx

  • Superior portion of pharynx

Pharynx overview

• Throat

• Shared with digestive system 

• Runs from internal nares to the larynx and esophagus

• Divided into three parts

  • Nasopharynx

  • Oropharynx

  • Laryngopharynx

Functions of cartilage of larynx

• Support and protect — the glottis (vocal folds + rims glottidis)

• Swallowing — when the larynx is elevated and the epiglottis folds over the glottis

Unpaired cartilage of larynx

• Thyroid cartilage

  • Hyaline cartilage

• Cricoid cartilage 

  • Hyaline cartilage

  • Articulates with the arytenoid cartilage

• Epiglottis 

  • Elastic cartilage

Paired cartilage of larynx

• Arytenoid cartilage 

• Corniculate cartilage

• Cuneiform cartilage

Ligaments of larynx

• Vocal ligaments 

  • Covered by vocal folds (mucous membrane)

    • Rima glottidis — opening between vocal folds. Vocal sounds produced by air passing through here.

• Vestibular ligaments 

  • Form the vestibular folds with its mucous membrane lining

 

Phonation

Refers to the production of sound at the larynx

• Voluntary muscles in larynx contract to abduct (pull apart) the vocal folds

• Other voluntary muscles in the larynx contract to adduct (bring together) the vocal folds

Articulation

The modification of vocal sound by anatomical structures

Vocal range

• The span of notes a person can sing

• Determined by length and thickness of vocal cords

Pitch

• The frequency of sounds waves

• Determined by tension on the vocal folds

Loudness

• Volume of vocal sounds

• Depends on force of air pushed through rima glottidis 

Trachea overview

• Tubular organ that extends through mediastinum from inferior larynx.

• Supported by tracheal cartilages

• Submucosa — layer of CT below respiratory mucosa, uses mucosal glands to produce mucous secreted through the respiratory mucosa

• Divides into left and right main bronchi at carina

  • Extend laterally and inferiorly into the lungs at the hilum of each lung

  • Right main bronchus is larger and enters lung more vertically — more likely that aspirated objects get lodged there

Lungs overview

• Primary organs of respiration

• Found in left and right sides of thoracic cavity

• Divided into lobes by deep fissures

Lobes + fissures of right lung

Right lung is separated by the horizontal and oblique fissures into:

• Superior lobe

• Middle lobe

• Inferior lobe

Lobes + fissures of left lung

Left lung is separated by the horizontal fissure into:

• Superior lobe

• Inferior lobe

Branching of bronchi

• Primary bronchi branch into lobar bronchi (secondary bronchi)

  • Enter the lobes of lungs

• Lobar bronchi branch into segmental bronchi 

  • Enter bronchopulmonary segment

Bronchitis definition 

Inflammation of the bronchial walls

Airways from segmental bronchi to alveoli

• Segmental bronchi

• Bronchioles 

• Terminal bronchioles

• Respiratory bronchioles

• Alveolar ducts

• Alveolar sacs (alveoli)

Bronchodilation overview

• Dilation of bronchioles due to relaxation of smooth muscle

• Controlled by sympathetic ANS

Bronchoconstriction overview

• Constriction of the bronchioles from smooth muscle contraction

• Controlled by parasympathetic ANS

• Occurs with histamine release

Asthma results from

Excessive bronchoconstriction

Lung trabeculae overview

• Consists of fibrous connective tissue

• Divide the lungs into functional units — pulmonary lobules.

• Pulmonary lobules divided by interlobular septa formed by lung trabeculae.

Pneumonia definition

Inflammation of the pulmonary lobules which causes fluid to leak into the alveoli.

Cells of alveolar wall

• Type I pneumocytes — predominant cell type

  • Simple squamous epithelial cell — promotes rapid gas diffusion

• Type II pneumocytes — secrete pulmonary surfactant

  • Consists of lipids and proteins

  • Reduce surface tension

  • Respiratory distress syndrome — alveolar collapse due to damage to type II pneumocytes

Pleura overview 

• Serous membrane that lines the outer lung surface and inner thoracic wall. Consists of

  • Parietal pleura

  • Visceral pleura

  • Pleural cavity (containing pleural fluid)

Inhalation vs exhalation (active/passive processes)

• Inhalation is always an active process (requires contraction of the diaphragm and intercostal muscles)

• Exhalation can be active or passive

Muscles involved in inhalation

Pull upward and outward:

• Sternocleidomastoid

• Scalenes

• Serratus posterior superior

• Pectoralis minor

• Erector (muscle that pulls a body part upward ) spinae

Muscles involved in exhalation

Pneumothorax

The condition in which air leaks into the pleural cavity. Leads to pressure being placed onto the lung — lung cannot be fully expanded 

Atelectasis

Lung collapse as a result of pneumothorax

Nervous control of breathing

• Medullary respiratory center — site in the brain stem, contains two main nuclei that control breathing 

  • Ventral respiratory group (VRG) — controls inhalation and exhalation by periodically sending signals for contraction of diaphragm and intercostal muscles

    • Phrenic nerve — innervates the diaphragm 

    • Intercostal nerves — innervate the intercostal muscles

  • Dorsal respiratory group (DRG) — receives sensory information from receptors. Monitor lung stretching and CO2 concentration to adjust VRG output

• Pontine respiratory center — modifies the activity of the medullary nuclei to provide a smooth transition between inhalation and exhalation

Hypercapnia

• Increased CO2 partial pressure in arteries

• Increased depth and rate of respiration 

Sudden infant death syndrome (SIDS)

Condition in which an infant suddenly stops breathing. Results from disruption in the normal respiratory reflex pattern