Continuing Respiratory System look over docs from exam 2 2 28 2020 1 The conducting zone a Trachea i Windpipe ii Extends from larynx to carina of trachea 1 Branching point into the 2 primary bronchi iii Composed of 3 layers 1 Mucosa 2 Submucosa 3 Adventitia b The flow of air i Branching Lobes of the lung a 3 on right b 2 on left 1 1 1 2 Trachea branches into left and right primary bronchi a Each lung served by only 1 primary bronchus 3 Left and right primary bronchi divide into secondary bronchi or lobar bronchi a Each lobe is supplied by only 1 secondary lobar bronchi ii Secondary lobar bronchi divide into tertiary bronchi These are further divided into smaller and smaller bronchi a 1 mm diameter bronchus iii Passages less than 1 mm in diameter called bronchioles Terminal bronchioles a Smallest of conducting zone b Diameter less than 5 mm c Still part of the conducting zone 2 The respiratory zone a Defined by the presence of air sacs b Terminal bronchioles branch into respiratory bronchioles c Respiratory bronchioles i ii Lead into alveolar ducts Have alveolar sacs 1 Contain alveoli a Gas exchange takes place 3 Muscle connective and epithelial tissue of the respiratory tract a Conducting zone trachea to terminal bronchioles b Respiratory zone respiratory bronchioles alveolar sacs alveoli c More cartilage in primary secondary and tertiary bronchi i Bronchioles and below lack cartilage d Smooth muscle i More found in bronchioles Terminal 1 2 Respiratory 3 Alveolar ducts ii Allows for constriction of airways e Alveoli where gas exchange takes place i ii Alveolar sac bunch of grapes Alveoli individual grades 4 Gas exchange in alveoli a 3 types of cells found in alveoli i Type 1 alveolar cells or type 1 pneumocytes Cover 90 of the alveoli 1 2 Site of gas exchange 3 Only single layer 4 Squamous epithelium 5 Extremely thin 100 nm good for diffusion ii Type 2 alveolar cells or type 2 pneumocytes 1 Scattered among type 1 cells 2 Produce surfactant a Oily secretion containing a mixture of lipids and proteins b Secreted over alveolar surfaces c d Reduces surface tension Forms a superficial coating over thin layer of water i ii Inward force Prevents alveoli from collapsing Alveolar macrophages Immune cells Eat microbes 1 2 b Respiratory membrane the blood air barrier 1 layer of squamous epithelial cells type 1 Capillary endothelium Fused basement membranes of alveolar capillary cells Only about 5mm thick Gas exchange occurs by simple diffusion 5 Pleurae the membrane of the lungs a Serosal membrane lines internal body cavities that are closed to the exterior Simple squamous epithelium overlying connective tissue b Each lung is covered by its own pleurae c Pleurae thin double layered serosal membranes Parietal pleura wall covers the thoracic wall and extends over diaphragm Visceral pleura organ covers outer surfaces of the lungs d Pleurae produces pleural fluid which fills pleural cavity Fluid is lubricating solution e Reduces friction between parietal and visceral surfaces during breathing f Fluid increases surface tension Through hydrogen bonds Prevents separation of the visceral and parietal pleura The two pleura stick together Lungs cling tightly to thoracic wall during breathing i ii iii iv 6 The mechanics of breathing a Negative pressure breathing when muscles contract lungs increase in volume alveoli decrease Vacuum action b Pulmonary ventilation consists of two phases Inspiration gases flow into lungs iii i ii iii iv v i i ii i i i ii Expiration gases exit lungs Contraction 1 2 Active 1 Relaxation 2 Passive c Mechanical process Depends on volume changes in thoracic cavity These changes in volume leads to pressure changes Pressure changes lead to flow of gases to equalize pressure d Muscles of respiration i ii iii i Diaphragm contracts to expand thoracic cavity 1 Sheet of skeletal muscle 2 Extends across bottom of thoracic cavity 3 Separates thoracic and abdominal cavities ii External intercostals contracts to elevate ribs Inhalation 1 Action pulls out chest cavity a Increases volume decreases pressure