The Respiratory System

Functions of the Respiratory System: Provides for gas exchange (called Respiration) Helps regulate blood pH Contains receptors for sense of smell Filters inspired air Produces sounds

Nose The visible external portion consists of bone and cartilage, covered by skin, and lined with mucous membrane Air enters via the nostrils Hairs lining the nostrils prevent entry of large particles carried in the air The internal portion is a large cavity in the skull and is connected to the pharynx and four paranasal sinuses.

Nose The cavity inside the external and internal portions of the nose is called the nasal cavity, which is divided by a partition called the nasal septum

Functions of the Nose Warming (by blood vessels) and moistening (by mucus) incoming air Receiving olfactory stimuli Provides resonating chamber for speech sounds

Pharynx (aka – throat) Muscular passageway for air passing between the nasal cavity and the larynx Its wall is composed of skeletal muscle and lined with mucous membrane Provides a resonating chamber for speech sounds

Larynx Conducts air in and out of the trachea and prevents foreign objects from entering the trachea. It also houses the vocal cords Composed of a framework of muscles and cartilage bound by elastic tissue. Largest of the cartilages are the thyroid (adam’s apple), cricoid, and epiglottic The epiglottis is a flap-like structure that closes during swallowing to prevent food from entering the trachea

Vocal Cords Part of the mucous membrane forms a pair of folds that form the “voice box” The slitlike passageway between folds is referred to as the glottis

Trachea Flexible ‘windpipe’ that is approx. 2.5cm in diameter and 12.5cm long Lined with mucous membrane that filters incoming air and cilia that moves entrapped particles upward to the pharynx Reinforced with about 20 C-shaped pieces of hyaline cartilage that prevent it from collapsing

Bronchi Once the trachea reaches the thoracic cavity, it splits into the right and left bronchi which plunge into the lungs

Lungs Soft, spongy, cone-shaped organ that consists of air passages, alveoli, blood vessels, connective tissues, lymphatic vessels, and nerves Occupies the entire thoracic cavity except for most of the central area (mediastinum). Each lung is divided into lobes; the left has two lobes and the right has three

Bronchial Tree After entering the lungs, the main bronchi subdivide into smaller (secondary bronchi) and smaller (tertiary bronchi) branches until finally ending with the smallest of the passageways, the bronchioles As the smaller and finer tubes appear, cartilage is replaced with a layer of smooth muscle Lined with mucous membrane

The Respiratory Zone The terminal bronchioles lead to the respiratory zone Includes the respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli Is the only site of gas exchange

Alveoli Millions of small microscopic air sacs clustered together (like bunches of grapes) Provide a large surface area of thin simple squamous epithelial cells where gas can be exchanged Covered with a cobweb of pulmonary capillaries

Effect of smoking Smoking inhibits ciliary activity as well as destroying cilia. Without cilia, coughing is the only means of preventing mucus from accumulating in the lungs Lack of cilia also increases frequency of pulmonary infections. Lung tissue is more susceptible to carcinogenic chemicals  Lung Cancer