Chapter 20: Respiratory System20.2: Introduction- Major processes of the respiratory systemo Ventilation: process of moving air from atmosphere into alveoli of lungs, and backo External Respiration: Exchange of O2 and CO2 between air in alveoli and the blood supplying the alveolio Transport of O2 and CO2 in bloodo Internal respiration: exchange of O2 and CO2 between blood and metabolically active cells of tissue20.3: Structures of the Respiratory System- Two functional divisions of respiratory systemo Conducting Division Provides passageway for air to move  warms, humidifies, and cleanses airo Respiratory Division Provides site of gas exchange between lungs and bloodSTRUCTURES OF CONDUCTING SYSTEM- The Moutho Acts in parallel with nose as a conduit for air entry/exito Mouth breathing  results from dryness in mouth when sleeping.  Associated with nasal obstruction  could require surgery- External Noseo Primary pathway for respirationo Apex: tip of noseo Nares: Opening to the nose  lines with hair for filtrationo Ala nasi: flap on lateral side of nostrilo Dorsum nasi: length of noseo Bridge: connects root to rest of noseo Root: located between the eyebrows- Internal Noseo Nares of nose open to nasal cavity Divided into right and left sides of nasal septumo Superior, middle, and inferior conchae C-shaped bones extending laterally from nasal septum Meatuses surround conchae and provide pathway for air to move along its surface Greatly increases surface area of nasal cavity- Nasal Sinuseso Nasal cavities are connected by small openings called ostia to four pairs of sinuseso 4 sinuses carry two of each of the following: Frontal, maxillary, sphenoid, and ethmoid They are air-filled spaces that serve to warm and humidify incoming air and resonate our voices Why we sound different when we hear ourselves talking- The Pharynxo Muscular tube with walls containing 2 layers of skeletal muscle and lined with mucous membraneo Two regions Nasopharynx- Continuous with nasal cavity  acts only as conduit for air- Adenoids (tonsils) lie in posterior wall and provide immune defense against inhaled pathogens- Auditory tubes connect it to middle ear  ear pain when flying Oropharynx- Connected to oral cavity  conduit by digestive and respiratory systems- Tonsils found at border  provide immune protection against inhaled and ingested bacteria- Inflammation of tonsils results in tonsillitis  need to remove tonsils Laryngopharynx- Shortest of three parts- Conduit for both air and food  structure of respiratory and digestive systems- Opens into larynx and esophagus - The Larynxo Directs air and food that enters pharynx into trachea and esophaguso Contains vocal cords  speech generationo Superior portion lined with squamous epitheliumo Inferior portion lined with mucous membrane that allows swallowing of trapped debriso Walls of larynx has 3 large cartilages and 3 small cartilages to prevent collapsing- The Glottis and Laryngeal Cartilageo Cartilage that prevents larynx from collapsingo 3 large: epiglottis, thyroid, and cricoido 3 small: arytenoid, corniculate, cuneiformo Glottis: vocal apparatus of the larynx Consists of vocal folds- The Tracheao Extends from larynx and divides into left and right primary bronchio Has hyaline cartilage that encloses, and provides protection to tracheal wall Composed of fibrous tissueo Contraction will narrow trachea, causing increase velocity of airflow  e.g. coughingo Carina is a ridge of cartilage that can sense entry of solid or liquid substances in the trachea and trigger violent coughing to expel themo Mucociliary escalator: system that traps particles and microorganisms and sweeps them to pharynx to be swallowed- Bronchi Through Terminal Bronchioleso Primary bronchi  secondary bronchi  tertiary bronchi  primary bronchiole  terminal bronchioleso Bronchi are supported by cartilage  internal lining composed of mucous membraneo Bronchioles: lack cartilaginous structures in their walls and instead have layer of smooth muscle  lack mucous, but still have ciliated cellsSTRUCTURES OF RESPIRATORY SYSTEM- Respiratory Bronchioles and Alveolar Sacso Formed by division of terminal bronchioles  have minimal smooth muscleo Alveolar ducts are short conduits composed of connective tissue  open into alveolar sacso Alveolar sacs: clusters of individual alveoli that opened from alveolar ductso Very elastic- Alveolio Structures across which gas exchange occurso Tin wall, large lumen  provide intimate contact between inhaled air and blood in pulmonary capillarieso Alveolar pores allow air to flow into neighboring alveoli to maintain equal pressures throughout- Alveolar cellso Type 1 Most common, forms majority of alveolar wall Connected by thin, elastic basement membrane that is shared on its other side by epithelial cells of the pulmonary capillary  respiratory membraneo Type 2 Cuboidal epithelial cells that secrete surfactant  a complex mixture of phospholipids and proteins that reduce surface tension of water molecules lining inner surface of alveolio Type 3 Immune cells that are resident in alveoli Phagocytic cells scavenge microorganisms and particles not captured in mucus- The Lungso Occupy most volume of thoracic cavity and enclosed by pleural membraneo Right lung has 3 lobes: superior, middle, and inferioro Left lung has 2 lobes: superior and inferior  contains cardiac notch which decreases volume of left lung comparativelyo Lobes are further divided into bronchopulmonary segments  these are divided into pulmonary lobules- Lung Pleurao Serous membrane that surrounds each lung  has 2 layers Visceral pleura  rightly covers each lung Parietal pleura  lines inner wall of thoracic cavityo Pleural cavity  small gap between layers that contains pleural fluid This fluid lubricates and provides barrier- Pulmonary Blood Flow- Zones of Blood Flowo Lungs are divided into zones based on pressure differences caused by gravityo Zone 1: Top of lungs  capillary < alveoli- Collapses capillaries and prevents flowo Zone 2: Middle of lungs  capillary > alveolar pressure- Allowing flow through capillaryo Zone 3: Base of lungs  capillary > alveolar pressure (ALWAYS)o Adequate gas exchange requires ventilation matching perfusion through the V/Q ratio V represents ventilation and Q represents blood