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 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 1o (primary) bronchi 2o (secondary) bronchi 3o (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

Simple squamous epithelium lines alveolar walls 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 O2 enters the blood (from alveoli) CO2 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 13.7a

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 13.7b

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 LUNGS TISSUE 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 oxygen-rich and carbon dioxide-poor

Gas Transport in the Blood Oxygen (O2) transport in the blood Inside red blood cells attached to hemoglobin (oxy-hemoglobin) A small amount is carried dissolved in the plasma Carbon dioxide (CO2) 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 LUNGS TISSUE 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