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Lecture 8

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Biological Sciences
Connie Potroff

1 Lecture 8 The Respiratory System (based on chapter 24) **Assigned readings: p.639 (tracheal blockage) + p.650 (respiratory changes at birth) An Overview of the Respiratory System The upper respiratory system consists of: nose, nasal cavity, sinuses, and pharynx The lower respiratory system consists of: larynx, trachea, bronchi, bronchioles, and alveoli Functions of the Respiratory System Provides an area for gas exchange between the air and the blood Protects the respiratory surfaces (for example: from dehydration) Provides protection against invading pathogens *Produces sound involved in verbal communication (larynx- voicebox) *Assists in the regulation of blood volume, blood pressure, and body fluid pH The Respiratory Epithelium Consists of: 1)Pseudostratified, ciliated, columnar cells (except for the pharynx, smaller bronchi, and alveoli) 2)Mucus-producing cells *Pharynx consists of 3)stratified squamous cells Function: Ciliated columnar cells move mucus in an upward manner (mucus escalator) so debris can be coughed out Mucous cells produce mucus so inhaled debris will get stuck and not enter the lungs Stratified squamous cells provide protection against abrasion Protection of the Respiratory System *Hairs in the nose called vibrissae block some of the inhaled debris Nasal cavity produces mucus to trap inhaled debris Sneezing will remove this debris Respiratory epithelium mucus will trap inhaled debris Coughing will remove this debris The Upper Respiratory System The following is the pathway of air: Air enters the external nares (nostrils) Passes by the nasal vestibule (area surrounded by the two pairs of alar cartilage) Enters the nasal cavity Air flows in and around the nasal conchae Inferior, middle, and superior conchae As air swirls around the conchae, debris gets stuck in the mucus As air swirls around the conchae, the air warms and gets humidified (moistened) a bit before entering the trachea Air enters the internal nares Air enters the nasopharynx area The Pharynx The pharynx (throat or gullet) is a funnel shaped passageway that connects the nose to the larynx of the respiratory system and the esophagus of the digestive system © 2012 Pearson Education, Inc. 2 • supporting walls of skeletal muscle and lined with mucous membrane • **within the pharynx are several paired lymphoid organs tonsils – large clusters of lymphatic cells and extracellular matrix that are not completely surrounded by a connective tissue capsule , they are designed to protect the pharynx from infection (first line of defence) with phagocytic cells that engulf bacteria, toxins, viruses, cancer cells, etc. Nasopharynx (uppermost portion of pharynx, behind nasal cavity and above soft palate) only a passageway for air because located above the point of food entry into the mouth pendulous uvula hangs from middle portion of soft palate, during swallowing, the soft palate and uvula are lifted to block the nasal cavity and prevent food from entering nasal cavity *contains pharyngeal tonsils (aka adenoids) in posterior region Oropharynx (central portion of pharynx) entry into the oral cavity and location of two more sets of tonsils (palatine on lateral walls and ligual on tongue) – first line of defence against ingested or inhaled foreign materials Laryngopharynx (lowermost portion of pharynx) at this point, the respiratory and digestive systems become distinct, inhaled air into larynx and swallowed food and liquid into esophagus The Lower Respiratory System The Larynx (voice box) A cylinder whose cartilaginous walls are stabilized by ligaments or skeletal muscles or both **Begins at the level of vertebrae C4or C 5nd ends at the level of vertebra C 7 Components (cartilages) of the Larynx Thyroid cartilage - contains the laryngeal prominence (Adam’s Apple) attached to hyoid bone by thyrohyoid membrane (a dense band of connective tissue) Cricoid cartilage – ring shaped hyaline cartilage attached larynx to trachea Epiglottis - spoon shaped elastic cartilage behind the tongue that is attached to the larynx and closes over the glottis (laryngeal opening) during swallowing of food *Paired laryngeal cartilages - some play a role in the opening and closing of the glottis Laryngeal Ligaments **A series of intrinsic laryngeal ligaments bind the laryngeal cartilages together to form larynx **Extrinsic laryngeal ligaments bind the thyroid cartilage to the hyoid bone and cricoid cartilage to the trachea Some of the ligaments become the vocal cords Sound Production by the Vocal Cords Air passing between the vocal cords creates sound, when we breath the vocal cords stay
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