The Respiratory System Cells continually use O2 & release CO2 Respiratory system designed for gas exchange Cardiovascular system transports gases in blood Failure of either system – rapid cell death from O2 starvation

23-2 Human Lungs

Respiratory System Anatomy Nose Pharynx = throat Larynx = voicebox Trachea = windpipe Bronchi = airways Lungs Locations of infections –upper respiratory tract is above vocal cords –lower respiratory tract is below vocal cords

External Nasal Structures Skin, nasal bones, & cartilage lined with mucous membrane Openings called external nares or nostrils

Nose -- Internal Structures Large chamber within the skull Roof is made up of ethmoid and floor is hard palate Internal nares are openings to pharynx Nasal septum is composed of bone & cartilage Bony swelling or conchae on lateral walls

Functions of the Nasal Structures Olfactory epithelium for sense of smell Pseudostratified ciliated columnar with goblet cells lines nasal cavity –warms air due to high vascularity –mucous moistens air & traps dust –cilia move mucous towards pharynx Paranasal sinuses open into nasal cavity –found in ethmoid, sphenoid, frontal & maxillary –lighten skull & resonate voice

Pharynx Muscular tube (5 inch long) hanging from skull –skeletal muscle & mucous membrane Extends from internal nares to cricoid cartilage Functions –passageway for food and air –resonating chamber for speech production –tonsil (lymphatic tissue) in the walls protects entryway into body Distinct regions -- nasopharynx, oropharynx and laryngopharynx

Regions of Pharynx Nasopharynx: passageway for air only Oropharynx and Laryngopharnx: passageway for food & air

Cartilages of the Larynx Thyroid cartilage forms Adam’s apple Epiglottis---leaf-shaped piece of elastic cartilage –during swallowing, larynx moves upward –epiglottis bends to cover glottis Cricoid cartilage---ring of cartilage attached to top of trachea Pair of arytenoid cartilages sit upon cricoid –many muscles responsible for their movement –partially buried in vocal folds (true vocal cords)

Larynx Cartilage & connective tissue tube Anterior to C4 to C6 Constructed of 3 single & 3 paired cartilages Anterior Posterior

Vocal Cords False vocal cords (ventricular folds) found above vocal folds (true vocal cords) True vocal cords attach to arytenoid cartilages

Trachea Size is 5 in long & 1in diameter Extends from larynx to T5 anterior to the esophagus and then splits into bronchi Layers –mucosa = pseudostratified columnar with cilia & goblet –submucosa = loose connective tissue & seromucous glands –hyaline cartilage = 16 to 20 incomplete rings open side facing esophagus contains trachealis m. (smooth) internal ridge on last ring called carina (cough reflex) –adventitia binds it to other organs

23-13 Histology of the Trachea Ciliated pseudostratified columnar epithelium Hyaline cartilage as C-shaped structure closed by trachealis muscle

Trachea and Bronchial Tree

Airway Epithelium Ciliated pseudostratified columnar epithelium with goblet cells produce a moving mass of mucus.

Bronchi and Bronchioles Primary bronchi supply each lung Secondary bronchi supply each lobe of the lungs (3 right + 2 left) Tertiary bronchi supply each bronchopulmonary segment Repeated branchings called bronchioles form a bronchial tree

Histology of Bronchial Tree Epithelium changes from pseudostratified ciliated columnar to nonciliated simple cuboidal, and finally to simple squamous as pass deeper into lungs Incomplete rings of cartilage replaced by rings of smooth muscle & then connective tissue –sympathetic NS & adrenal gland release epinephrine that relaxes smooth muscle & dilates airways –asthma attack or allergic reactions constrict distal bronchiole smooth muscle

Pleural Membranes & Pleural Cavity Visceral pleura covers lungs --- parietal pleura lines ribcage & covers upper surface of diaphragm Pleural cavity is potential space between ribs & lungs

Gross Anatomy of Lungs Base, apex, cardiac notch Oblique & horizontal fissure in right lung results in 3 lobes Oblique fissure only in left lung produces 2 lobes

Mediastinal Surface of Lungs Blood vessels & airways enter lungs at hilus Covered with pleura (parietal becomes visceral)

23-21 Lobules

Structures within a Lobule of Lung Branchings of single arteriole, venule & bronchiole are wrapped by elastic CT Respiratory bronchiole –simple squamous Alveolar ducts surrounded by alveolar sacs & alveoli –sac is 2 or more alveoli sharing a common opening

Photomicrograph of lung tissue showing bronchioles, alveoli and alveolar ducts. Histology of Lung Tissue

Cells Types of the Alveoli Type I alveolar cells –simple squamous cells where gas exchange occurs Type II alveolar cells –free surface has microvilli –secrete alveolar fluid containing surfactant Alveolar dust cells –wandering macrophages remove debris

Alveolar-Capillary Membrane Respiratory membrane = 1/2 micron thick Exchange of gas from alveoli to blood 4 Layers of membrane to cross –alveolar epithelial wall of type I cells –alveolar epithelial basement membrane –capillary basement membrane –endothelial cells of capillary Vast surface area = handball court

Details of Respiratory Membrane