Respiratory System

• Respiratory system

  • Cells obtain energy primarily through aerobic metabolism
  • Requires oxygen and produces carbon dioxide
  • Oxygen is obtained from air by diffusion across exchange surfaces in lungs
  • Blood carries oxygen from lungs to peripheral tissues
  • And carries carbon dioxide from peripheral tissues to lungs
• Functions of respiratory system

  • Provide extensive surface area for gas exchange between air and circulating blood
  • Move air to and from exchange surfaces of lungs
  • Protect respiratory surfaces from dehydration, temperature changes, and pathogens
  • Produce sounds
  • Detect odors with olfactory receptors in nasal cavity
• Organization of respiratory system

  • Upper respiratory system
  • Nose, nasal cavity, paranasal sinuses, and pharynx
  • Lower respiratory system
  • Larynx, trachea, bronchi, bronchioles, and alveoli
• Respiratory tract

  • Conducting portion
  • From nasal cavity to larger bronchioles
  • Respiratory portion
  • Smallest respiratory bronchioles and alveoli
  • Alveoli
  • Air-filled pockets within lungs
  • Where all gas exchange takes place
• Respiratory mucosa

  • Lines conducting portion of respiratory system
  • Consists of
  • An epithelium
  • Areolar tissue layer (lamina propria)
  • Functions in the respiratory defense system
  • A series of filtration mechanisms
  • Removes particles and pathogens from inhaled air
• Lamina propria

  • In upper respiratory system, trachea, and bronchi
  • Contains mucous glands that discharge secretions onto epithelial surface
  • In conducting portion of lower respiratory system
  • Contains smooth muscle cells that encircle lumen of bronchioles
• Respiratory Epithelium of the Nasal Cavity and Conducting Portion of the Respiratory Tract

  • The cilia (hair like projection) of the epithelial cells form a dense layer that resembles a shag carpet
  • like a mucous escalator, traps particles and comes up to top where we can blow or cough it out
• Structure of respiratory epithelium

  • Nasal cavity and superior portion of pharynx
  • Pseudostratified ciliated columnar epithelium with numerous mucous cells
  • Inferior portions of pharynx
  • Stratified squamous epithelium
  • Superior portion of lower respiratory system
  • Pseudostratified ciliated columnar epithelium
  • Smaller bronchioles
  • Cuboidal epithelium with scattered cilia
• Alveolar epithelium

  • Lines exchange surfaces of alveoli
  • Very delicate, simple squamous epithelium
  • Contains scattered, specialized cells
• Respiratory defense system

  • Filtration in nasal cavity removes large particles
  • Mucous cells and mucous glands
  • Produce mucus that bathes exposed surfaces
  • Cilia
  • Sweep mucus and trapped debris and microorganisms toward pharynx to be swallowed
  • Alveolar macrophages
  • Engulf small particles that reach lungs
• Nose

  • Primary passageway for air entering respiratory system
  • Air enters through nostrils (nares)
  • Passes into nasal vestibule (space contained within flexible tissues of nose)
  • Nasal hairs
  • In epithelium of vestibule 
  • Trap large particles in air
• Nasal cavity

  • Nasal septum
  • Divides nasal cavity into left and right sides
  • Anterior portion (hyaline cartilage) supports dorsum of nose and apex of nose
  • Superior portion of nasal cavity is olfactory region (cranial nerve I)
  • Provides sense of smell
  • Mucus produced in paranasal sinuses and tears
  • Clean and moisten nasal cavity
• Air flows

  • From vestibule to choanae (openings of nasal cavity)
  • Through superior, middle, and inferior nasal meatuses
  • Meatuses are narrow passageways that produce air turbulence to
  • Trap particles in mucus
  • Warm and humidify incoming air
  • Bring olfactory stimuli to olfactory receptors
• Palates

  • Hard palate
  • Forms floor of nasal cavity
  • Separates nasal and oral cavities
  • Soft palate
  • Extends posterior to hard palate
  • Divides superior nasopharynx from rest of pharynx
• Upper Respiratory System

  • Nasal cavity opens into nasopharynx at choanae
  • Nasal mucosa
  • Warms and humidifies inhaled air for arrival at lower respiratory system
  • Breathing through mouth bypasses this important step
  • Nosebleed
  • Fairly common due to extensive vascularization of nasal cavity
• Pharynx

  • A chamber shared by digestive and respiratory systems
  • Extends between choanae and entrances to larynx and esophagus
  • Divided into 3 parts
  • Nasopharynx
  • Oropharynx
  • Laryngopharynx
  • begins at epiglottis, a little flap closes trachae when we swallow because food and water and air come down pharynx, but food and water will go into esophagus to go into stomach and air will enter trachae, covers so we do not get food and water into lungs
• Nasopharynx

  • Superior portion of pharynx
  • Contains pharyngeal tonsil and pharyngeal openings of auditory tubes

  Oropharynx

  • Connects directly to oral cavity

  Laryngopharynx

  • Inferior portion of pharynx
  • Between hyoid bone and entrance to larynx and esophagus
• Lower Respiratory System

  • Air flows from pharynx to larynx
  • Through glottis
  • Slit-like opening between vocal cords
  • Three large, unpaired cartilages form the larynx
  • Thyroid cartilage
  • Cricoid cartilage
  • Epiglottis
• Thyroid cartilage

  • Hyaline cartilage
  • Forms most of anterior and lateral walls of larynx
  • Anterior surface is called laryngeal prominence, or Adam’s apple
  • Ligaments attach to hyoid bone, epiglottis, and smaller laryngeal cartilages
• Cricoid cartilage

  • Hyaline cartilage
  • Forms posterior portion of larynx
  • Ligaments attach to first tracheal cartilage
  • Articulates with arytenoid cartilages

  Epiglottis (can become inflamed when children develop epiglottitis)

  • Elastic cartilage
  • Covers glottis when swallowing
  • Ligaments attach to thyroid cartilage and hyoid bone
• Lower Respiratory System

  • Thyroid and cricoid cartilages support and protect
  • Glottis
  • Entrance to trachea
  • During swallowing
  • Larynx is elevated
  • Epiglottis folds back over glottis
  • Prevents food and liquids from entering respiratory tract
• Three pairs of smaller hyaline cartilages in larynx

  • Arytenoid cartilage
  • Corniculate cartilage
  • Cuneiform cartilage
  • Corniculate and arytenoid cartilages function in
  • Opening and closing of glottis
  • Production of sound
• Ligaments of larynx

  • Vestibular ligaments and vocal ligaments
  • Extend between thyroid cartilage and arytenoid cartilages
  • Covered by folds of laryngeal epithelium
  • Vestibular ligaments lie within vestibular folds
  • Protect delicate vocal folds of glottis
  • Vocal folds are involved with production of sound,so are also known as vocal cords
• Sound production

  • Air passing through glottis vibrates vocal folds
  • Producing sound waves
  • Voluntary muscles reposition arytenoid cartilages
  • Control tension of vocal folds
  • Altering pitch of sound
  • Speech is produced by
  • Phonation — sound production at larynx
  • Articulation — sound modification with lips, tongue, and teeth
• Larynx is associated with two sets of muscles 

  • Muscles of neck and pharynx
  • Position and stabilize larynx 
  • Smaller intrinsic muscles
  • Control tension in vocal folds 
  • Open and close glottis
• Trachea (windpipe)

  • Tough, flexible tube
  • (if swallowing large food, back wall can go into lumen of trachae to allow food to pass)
  • Extends from cricoid cartilage to mediastinum (middle area in chest behind sternum)
  • Branches into right and left main bronchi
  • Submucosa
  • Thick layer of connective tissue
  • Surrounds mucosa
  • Contains tracheal glands that produce mucous secretions
• Trachea

  • Contains 15–20 C-shaped tracheal cartilages
  • Stiffen tracheal walls and protect airway
  • Discontinuous where trachea contacts esophagus, allowing distortion of tracheal wall when swallowing
  • Ends of each tracheal cartilage are connected by
  • Elastic anular ligament 
  • Trachealis muscle
• Bronchial tree

  • Right main bronchus and left main bronchus
  • Each divides to form lobar bronchi that supply lobes of lungs (right lung has 3 lobes and left lung has 2 )
  • Lobar bronchi branch to form segmental bronchi
  • Each segmental bronchus
  • Supplies air to one bronchopulmonary segment
  • Right lung has 10
  • Left lung has 8 or 9
• Carina of trachea

  • Ridge that separates openings of right and left main bronchi
  • At their junction with trachea
  • important X rays
• Bronchial structure

  • Walls of main, lobar, and segmental bronchi
  • Contain progressively less cartilage and more smooth muscle
  • Degree of smooth muscle tension affects bronchial diameter and resistance to airflow
  • Bronchitis
  • Inflammation and constriction of bronchi and bronchioles due to infection
  • Causes breathing difficulty
• Bronchioles

  • Each segmental bronchus branches into multiple bronchioles
  • Bronchioles branch into terminal bronchioles
  • Each segmental bronchus forms about 6500 terminal bronchioles
  • Bronchioles have no cartilage
  • Dominated by smooth muscle
• Autonomic nervous system

  • Controls luminal diameter of bronchioles by regulating smooth muscle
  • Controls airflow in lungs
• Bronchodilation

  – Caused by sympathetic activation

  – Enlarges luminal diameter of airway 

  – Reduces resistance to airflow

  Bronchoconstriction

  – Reduces luminal diameter of airway 

  – Caused by

  • Parasympathetic activation

  • Histamine release (allergic reactions)
• Asthma

  • Excessive stimulation of smooth muscles
  • Causing severe bronchoconstriction
  • Restricts airflow
• Each terminal bronchiole branches to form several respiratory bronchioles

  • Respiratory bronchioles are connected to alveoli along alveolar ducts
  • Alveolar ducts end at alveolar sacs
  • Common chambers connected to many individual alveoli
  • Each alveolus has an extensive network of capillaries
  • Surrounded by elastic fibers
• Alveolar cell layer

  • Consists mainly of simple squamous epithelium
  • Formed by thin, delicate pneumocytes type I 
  • Site of gas exchange
  • Patrolled by alveolar macrophages
  • Contains large, scattered pneumocytes type II that produce surfactant
• Surfactant

  – Oily secretion

  – Contains phospholipids and proteins

  – Coats alveolar surface and reduces surface tension

  § Respiratory distress syndrome

  – Alveoli collapse after each exhalation

  – Caused by inadequate amounts of surfactant due to injury or genetic abnormalities
• Gas exchange occurs across blood air barrier of alveoli 

  - Consists of three layers

  • Alveolar cell layer

  • Capillary endothelial layer

  • Fused basement membrane between them
• Gas exchange across blood air barrier is quick and efficient

  – Because distance for diffusion is short

  – And O2 and CO2 are small and lipid soluble

  § Pneumonia

  – Inflammation of lung tissue

  – Causes fluid to leak into alveoli

  – Compromises function of blood air barrier
• The Lungs

  • Left and right lungs
  • In left and right pleural cavities
  • Inferior portion (base) rests on diaphragm
  • Lobes of lungs are separated by deep fissures
  • Right lung has three lobes: has more space
  • Superior, middle, and inferior
  • Separated by horizontal and oblique fissures
  • Left lung has two lobes; displaced by heart
  • Superior and inferior
  • Separated by oblique fissure