Organs of the Respiratory system Nose Pharynx Larynx

Organs of the Respiratory system § Nose § Pharynx § Larynx § Trachea § Bronchi § Lungs – alveoli Figure 13. 1

Function of the Respiratory System § Purify, warm, and humidify incoming air § Gas exchange – alveoli § Air enters through external nares (nostrils) § The interior of the nose consists of a nasal cavity divided by a nasal septum

Upper Respiratory Tract Figure 13. 2

Anatomy of the Nasal Cavity § Olfactory receptors on the superior surface § Cavity is lined with respiratory mucosa § Moistens/humidifies air § Traps incoming foreign particles § Lateral walls have conchae § Increase surface area & air turbulence § The nasal cavity is separated from the oral cavity by the hard (ant. ) and soft (post. ) palate

Paranasal Sinuses

Paranasal Sinuses § Cavities within bones surrounding the nasal cavity § Lighten skull § Resonance chambers for speech § Produce mucus - drains into the nasal cavity § Neti pot video

Larynx § Routes air and food into proper channels § Plays a role in speech § Made of eight rigid hyaline cartilages and a flap of elastic cartilage (epiglottis)

Structures of the Larynx § Thyroid cartilage § Protrudes anteriorly (Adam’s apple) § Vocal cords (vocal folds) § Vibrate with expelled air to create sound § Vid 1 Vid 2

Trachea (Windpipe) § Connects larynx with bronchi § Lined with ciliated cells § Beat continuously in the opposite direction of incoming air § Expel mucus loaded with dust and other debris away from lungs § Walls are reinforced with C-shaped hyaline cartilage

Trachea (Windpipe)

Primary Bronchi § Bronchi subdivide into smaller and smaller branches § 1 o (primary) bronchi § 2 o (secondary) bronchi § 3 o (tertiary) bronchi § Bronchioles § Terminal bronchioles

Respiratory Tree Divisions

Bronchioles § Smallest branches § Terminal bronchioles end in alveoli § Structure of alveoli § Alveolar sac § Alveolar duct § Alveolus § Gas exchange takes place within the alveolus

Alveoli § Simple squamous epithelium lines alveolar walls § Pulmonary capillaries cover external surfaces of alveoli

Respiratory Membrane (Air-Blood Barrier) Figure 13. 6

Gas Exchange § Gas diffuses across the respiratory membrane § O 2 enters the blood (from alveoli) § CO 2 enters the alveoli (from blood) § Macrophages in alveoli provide protection

Mechanics of Breathing § Completely mechanical process § Depends on volume changes in the thoracic cavity § Volume changes lead to pressure changes, which lead to the flow of gases to equalize pressure § Two phases § Inspiration – flow of air into lung § Expiration – air leaving lung

Inspiration § Diaphragm and intercostal muscles contract § The size of the thoracic cavity increases § External air is pulled into the lungs due to an increase in intrapulmonary volume (negative pressure)

Inspiration Figure 13. 7 a

Expiration § Largely a passive process § Depends on natural lung elasticity § As muscles relax, air is pushed out of the lungs § Forced expiration can occur mostly by contracting internal intercostal muscles to depress the rib cage (positive pressure)

Expiration Figure 13. 7 b

Respiratory Volumes and Capacities § Tidal volume (TV): Normal breathing moves about 500 ml of air with each breath § Factors that affect respiratory capacity § A person’s size, sex & age § Physical condition § Residual volume (RV): after exhalation, about 1200 ml of air remains in the lungs

Respiratory Capacities Figure 13. 9

Respiratory Volumes and Capacities § Inspiratory reserve volume (IRV) § Amount of air that can be taken in forcibly over the tidal volume § Usually between 2100 and 3200 ml § Expiratory reserve volume (ERV) § Amount of air that can be forcibly exhaled § Approximately 1200 ml

Respiratory Capacities Figure 13. 9

Respiratory Volumes and Capacities § Residual volume § Air remaining in lung after expiration § About 1200 ml

Respiratory Capacities Figure 13. 9

Respiratory Volumes and Capacities § Vital capacity § The total amount of exchangeable air § Vital capacity = TV + IRV + ERV § Dead space volume (Residual) § Air that remains in conducting zone and never reaches alveoli

Respiratory Volumes and Capacities § Functional volume § Air that actually reaches the respiratory zone § Respiratory capacities are measured with a spirometer

Respiratory Capacities Figure 13. 9

External and Internal Respiration External Respiration Internal Respiration TISSUE LUNGS Bloodstream (capillaries) Figure 13. 11

External Respiration (betw. lungs & blood) § Oxygen movement into the blood § The alveoli always has more oxygen than the blood § Oxygen moves by diffusion towards the area of lower concentration of oxygen § Pulmonary (lung) capillary blood gains oxygen

External Respiration (betw. lungs & blood) § Carbon dioxide movement out of the blood § Blood returning from tissues has higher concentrations of carbon dioxide than air in the alveoli § Pulmonary capillary blood gives up carbon dioxide (diffusion) § Blood leaving the lungs is oxygenrich and carbon dioxide-poor

Gas Transport in the Blood § Oxygen (O 2) transport in the blood § Inside red blood cells attached to hemoglobin (oxy-hemoglobin) § A small amount is carried dissolved in the plasma § Carbon dioxide (CO 2) transport in the blood § Most is transported in the plasma § A small amount is carried inside red blood cells on hemoglobin (but at different binding sites than those of oxygen)

Internal Respiration (betw. blood & tissue) § Exchange of gases between blood and body cells § The opposite of what occurs in the lungs § Carbon dioxide diffuses out of tissue to blood § Oxygen diffuses from blood into tissue

External and Internal Respiration External Respiration Internal Respiration TISSUE LUNGS Bloodstream (capillaries) Figure 13. 11

Neural Regulation of Respiration § respiratory muscles § phrenic nerve diaphragm § intercostal nerves intercostal muscles § Control center -- rate & depth – in medulla § Normal rate is 12– 15 breaths/min.

Factors Influencing Respiratory Rate and Depth § Physical factors § Increased body temperature § Exercise, Talking, Coughing § Volition (conscious control) § Emotional factors § Carbon dioxide levels § Oxygen levels