BIO10004 WK9

• Primary functions of the respiratory system

  • Provide a large area for gas exchange
  • Move air to and from lungs
  • Protect respiratory surfaces
  • Produce sounds: speaking, singing and communication
  • Detection of odors in superior section
• Upper respiratory tract


  Nose, nasal cavity, sinuses and pharynx
• Lower respiratory tract


  Larynx, trachea, bronchus, lung, bronchioles and alveoli's
• Epithelial surface cells


  • Form from dense layer of cilia
  • Helps with movement and defense
• Respiratory mucosa


  • Contains superficial epithelia tissue with cilia and mucous cells
  • Deeper areolar tissue for support
• Throughout much of the nasal cavity, the lamina propria contains an abundance of arteries, veins, and capillaries that bring nutrients and water to the secretory cells
• The lamina propria of the nasal conchae also contains an extensive network of highly expandable veins. This vascularization warms and humidifies the incoming air
• As cool, dry air passes inward over the exposed surfaces of the nasal cavity, the warm epithelium radiates heat, and water in the mucus evaporates. In this way, air moving from your nasal cavity to your lungs is heated almost to body temperature to avoid damaging alveoli
• Nose and nasal cavity


  • The epithelium of the vestibule contains coarse hairs that extend across the nostrils
  • The olfactory region is the superior portion of the nasal cavity and includes the areas lined by olfactory epithelium
• Air flow in nasal cavity


  1. Passes between adjacent conchae, through the superior, middle, and inferior nasal meatuses

  2. Turbulence allows airborne particles to contact mucus coating of nasal cavity and bring olfactory stimuli to olfactory receptors
• Hard palate


  • Made up of portions of the paired maxillae and palatine bones
  • Forms the floor of the nasal cavity and separates it from the oral cavity
• Soft palate


  Extends posterior to the hard palate, marking the boundary between the superior nasopharynx and the rest of the pharynx
• Pharynx


  • Chamber shared by digestive and respiratory system
  • Extends between the choanae and entrance to the larynx and esophagus
  • The curving superior and posterior walls are closely bound to the axial skeleton, but the lateral walls are flexible and muscular
  • Divided into three parts: the nasopharynx, the oropharynx, and the laryngopharynx
• Larynx


  • A cartilaginous tube that surrounds and protects the glottis
  • Begins at the level of vertebra C4 or C5 and ends at the level of vertebra C6
  • Essentially a cylinder, with incomplete cartilages that are stabilized by ligaments and laryngeal muscles
  • The vocal folds are highly elastic, because the vocal ligaments consist of elastic tissue
• Sound production


  1. Air passing through your open glottis vibrates its vocal folds and produces sound waves

  2. The pitch of the sound depends on the diameter, length, and tension in your vocal folds

  3. You control the tension by contracting voluntary muscles that reposition the arytenoid cartilages relative to the thyroid cartilage
• Vocal folds


  Involved with the production of sound
• Laryngitis


  Infection or inflammation of the larynx, can affect vibrational qualities of the vocal folds (hence hoarseness of voice when sick)
• Acute epiglottitis


  Infection of the epiglottis, can develop rapidly after a bacterial infection of the throat (and is quite dangerous)
• Trachea


  • A tough, flexible tube with a diameter of about 2.5 cm (1 in.) and a length of about 11 cm (4.33 in.)
  • Begins anterior to vertebra C6 in a ligamentous attachment to the cricoid cartilage
  • Ends in the mediastinum, at the level of vertebra T5, where it branches to form the right and left main bronchi
  • Epithelium is continuous with the larynx
  • Mucosa is the same as the nasal cavity and nasopharynx
  • Submucosa is a thick layer of connective tissue that surrounds the mucosa and contains tracheal glands that secrete mucous
  • Contains 15–20 tracheal cartilages that stiffen the tracheal walls and prevent it from collapsing or overexpanding
• Bronchi


  • As the amount of cartilage decreases, the amount of smooth muscle increases
  • With less cartilaginous support, the degree of tension in those smooth muscles exerts a proportionally greater effect on bronchial diameter and the resistance to airflow
• Bronchitis


  Respiratory infection where the bronchi and bronchioles become inflamed and constricted, increasing resistance and causing difficulty breathing
• Bronchioles


  • Each segmental bronchus branches several times within a bronchopulmonary segment, forming many bronchioles
  • Terminal bronchioles are the finest conducting branches, with a diameter of 0.3–0.5 mm
  • Walls lack cartilage and are dominated by smooth muscle tissue
  • Changes in the diameter control the resistance to airflow and the distribution of air in the lungs
• Autonomic nervous system


  • Controls the luminal diameter of the bronchioles by regulating the smooth muscle layer
  • Sympathetic activation leads to bronchodilation, parasympathetic stimulation leads to bronchoconstriction
• Excessive stimulation, as in asthma, can almost completely prevent airflow along the terminal bronchioles
• Bronchoconstriction also takes place during allergic reactions such as anaphylaxis, in response to histamine released by activated mast cells and Basophils
• Lungs


  • Right lung has three lobes, left lung has two lobes
  • Right lung is broader than the left, left lung is longer than the right
• Pulmonary lobule


  • Connective tissues of the root of each lung extend into the lung's parenchyma, forming fibrous partitions or trabeculae
  • The finest partitions, or interlobular septa, divide the lung into pulmonary lobules
  • Each lobule receives branches of the pulmonary arteries, pulmonary veins, and respiratory passageways
• Respiratory bronchioles


  • Connected to individual alveoli and to multiple alveoli along regions called alveolar ducts
  • Alveolar ducts end at alveolar sacs
• Each lung contains about 150 million alveoli
• Alveoli


  • Associated with an extensive network of capillaries
  • Surrounded by a network of elastic fibers that help maintain their relative positions and reduce the size during exhalation
  • Alveolar cell layer consists mainly of simple squamous epithelium
• Pneumocytes type I


  Unusually thin squamous epithelial cells that are the sites of gas diffusion
• Pneumocytes type II


  Large cells scattered among the squamous cells that produce surfactant, an oily secretion that reduces surface tension and prevents alveolar collapse
• Alveolar macrophages


  Roaming cells that patrol the epithelial surface and engulf any particles that have eluded other defenses
• If pneumocytes type II produce inadequate amounts of surfactant due to injury or genetic abnormalities, the alveoli collapse after each exhalation
• Cuboidal epithelium


  Lines the terminal bronchioles and respiratory bronchioles, with only scattered cilia and no mucous cells or underlying mucous glands
• Extrapulmonary air conduits


  Located outside of the lungs, beginning with the nose, pharynx and larynx
• Intrapulmonary air conduits


  Located within the lung, extending from the interlobar bronchi to the terminal bronchioles
• Pulmonary circuit


  Supplies the respiratory portion of the lungs with deoxygenated blood from the pulmonary arteries, which branch with the bronchi and form a capillary network around the alveoli
• Oxygen-rich blood from the alveolar capillaries passes through the pulmonary venules and then enters the pulmonary veins, which deliver the blood to the left atrium
• Respiratory system


  • Provides large area for gas exchange
  • Moves air to and from lungs
  • Protects respiratory surfaces
  • Produces sounds: speaking, singing, communication
  • Detects odours in superior section