1. Respiratory System Chapter 15

2. The main function of the respiratory system is to supply oxygen to, & eliminate carbon dioxide from the body
In order to accomplish this task, the respiratory system must work in conjunction with the cardiovascular system

3. “Respiration” refers to the overall exchange of gases between the atmosphere, blood & cells
Respiration involves 3 processes
Pulmonary ventilation
Gas exchange (gas diffusion)
External respiration
Internal respiration
Gas transport

4. Anatomy Overview The respiratory tract includes:
Nose (nasal cavity) Pharynx (nasopharynx, oropharynx, laryngopharynx) Larynx Trachea Bronchi (primary, secondary (lobar), tertiary (segmental) Bronchioles
Terminal bronchioles  Alveolar ducts Alveoli
Nasal cavity
Pharynx
Larynx
Trachea
Bronchi
Bronchioles
Respiratory bronchioles
Right
Lung
Left Lung
Alveolar duct
Alveoli

5. Histology
Respiratory Epithelium = Pseudostratified Ciliated Columnar (PSCC)

6. Nose (nasal cavity)
Air normally enters through external nares through nasal vestibule into nasal cavity.
Functions of nasal cavity include: warming, moistening & filtering air; olfaction

7. Pharynx
Air passes from nasal cavity into nasopharynx, past oropharynx & through laryngopharynx to larynx
Nasopharynx lined with PSCC epithelium, but oro & laryngopharynx lined with stratified squamous epithelium

8. Larynx
Air passageway made of 9 pieces of cartilage – (1) Thyroid cartilage, (1) Epiglottis, (1) Cricoid cartilage, (2) Arytenoid, (2) Corniculate, (2) Cuneiform
A.K.A your “voicebox” because it contains the vocal cords

9. Thyroid cartilage – protects anterior & lateral walls of airway
Epiglottis – leaf-shaped cartilage that protects opening (“glottis”) of airway when swallowing
Cricoid cartilage – complete ring of cartilage; protects posterior wall of airway; attaches to trachea

10. Arytenoid, corniculate & cuneiform cartilages – attach to upper (false) vocal folds & lower (true) vocal cords

11. Trachea
Tough but flexible “windpipe”, anterior to esophagus
attached to cricoid cartilage (at about C6 vertebral level) & ends within mediastinum by branching into left & right primary bronchi (at T5 vertebral level)
End of trachea known as Carina
Carina

12. Trachea Lined with respiratory epithelium
“C”-shaped pieces of hyaline cartilage protecting airway while allowing for swallowing
Trachealis muscle (smooth muscle) runs across posterior wall of trachea connecting ends of tracheal cartilage

13. Bronchi
Trachea splits into a left & right primary bronchus which enters into the hilus (hilum) of each lung
Within the lung, the primary bronchi branch into secondary (lobar) bronchi (3 in right lung/2 in left lung)
Secondary bronchi then branch into 10 tertiary (segmental) bronchi
Tertiary bronchi then continue to branch into smaller & smaller bronchi & then into very narrow bronchioles
Carina
This branching patterns creates the “bronchial tree”

14. Changes In Airway
As you go further down into the bronchial tree of each lung, changes in the airway occur:
increased number of airways (1 primary; 2 or 3 secondary; 10 tertiary bronchi; 6000 terminal bronchioles; millions of alveolar ducts)
decreased diameter of each airway
decreased amount of cartilage in the airways (no cartilage at all by terminal bronchioles)
increased amount of smooth muscle (relative to diameter)
lining epithelium changes from PSCC  simple squamous epithelium (in alveoli)

15. Lungs
Located within the thoracic cavity, surrounded by the double-layered pleural membrane –
parietal pleura – lines cavity wall
visceral pleura – covers the lungs

16. Lungs- Anatomical Features
Apex – extends 1” above clavicle
Base – rests on diaphragm
Hilum – at medial surface; where primary bronchus, pulmonary artery & veins enter/exit lung
Superior lobe
Inferior lobe
Oblique fissure
Superior lobe
Middle lobe
Inferior lobe
Right lung
Horizontal fissure
Oblique fissure
Left lung
Cardiac notch

17. Airways within Lungs
Each lung has a primary bronchus entering at the hilum
Each lobe of a lung has a secondary (a.k.a. lobar) bronchus
Lobes are functionally divided into bronchopulmonary segments & each segment has a tertiary (segmental) bronchus
Segments are functionally divided by elastic CT partitions into many lobules & each lobule receives a terminal bronchiole

18. Relationship of Airways & Pulmonary Vessels
As airways branch within lungs, they are accompanied by branches of the pulmonary artery (carrying de-oxygenated blood into the lungs), & branches of the pulmonary veins (carrying oxygenated blood out of the lungs)
As the alveolar ducts expand to form alveoli, pulmonary arterioles will branch to form a network of pulmonary capillaries, surrounding the alveoli

19. Alveoli
Alveoli are expanded chambers of epithelial tissue that are the exchange surfaces of the lungs
There are about 150 million alveoli in each lung
Multiple alveoli usually share a common alveolar duct, creating “alveolar sacs”

20. Alveoli There are three types of cells found within alveoli:
Alveolar Squamous epithelial (aka “type I”) cells – primary cells making up the wall of the alveoli
Septal (aka “type II”) cells – sectrete “surfactant” to reduce surface tension which prevents alveoli from sticking together & allows for easier gas exchange
Alveolar macrophages (aka “dust cells”) – phagocytic cells that remove dust, debris & pathogens

21. Gas “exchange” (external respiration) occurs across the Respiratory membrane – the fused membranes of the alveolar epithelium & the pulmonary capillary endothelium

22. Physiology of Respiration
“Respiration” refers to the overall exchange of gases between the atmosphere, blood & cells
Respiration involves 3 processes
Pulmonary ventilation
Gas exchange
External respiration
Internal respiration
Gas transport

23. Physiology of Respiration
Pulmonary Ventilation – “exchange” (movement) of gases between the atmosphere & lungs; movement of gases occurs because of pressure differences between the atmosphere (atmospheric pressure (Po)) & lungs (intrapulmonic pressure (Pi))
Two phases of ventilation:
Inspiration
active process involving contraction of diaphragm & external intercostal muscles
Expiration
normally passive due to relaxation of above muscles
can be made active (forced expiration) due to contraction of abdominals & internal intercostal muscles

24. Pulmonary Ventilation

25. Lung Volumes & Capacities
Respiratory frequency (f) – number of ventilations (inspiration+expiration) per minute
Tidal volume (TV) - amount of air moved in or out of the lungs during a normal breath
Minute ventilation (VE=TV x f)- amount of air inhaled or exhaled in one minute

26. Lung Volumes & Capacities (cont.)
Inspiratory reserve volume (IRV) – amount of air that can be inhaled after a normal inspiration (above the resting TV)
Inspiratory capacity (IC = TV+IRV) – amount of air inhaled after a normal expiration
Expiratory reserve volume (ERV) – amount of air that can be exhaled after a normal expiration
Residual volume (RV) – amount of air remaining in lungs even after maximal expiration

27. Lung Volumes & Capacities (cont.)
Vital capacity (VC=TV+IRV+ERV) – maximum amount of air you can exhale, following a maximal inhalation
Total lung capacity (TLC=TV+IRV+ERV+RV) – maximum amount of air in your lungs, following a maximal inhalation

28. Gas Exchange (gas diffusion)
External respiration - the diffusion of O2 & CO2 between the alveoli & blood across the respiratory membrane
occurs because of pressure differences of each gas within alveolar air & pulmonary (deoxygenated) blood
results in creation of oxygenated blood

29. Gas Exchange
Internal respiration – the diffusion of O2 & CO2 between the blood & interstitial fluid across the endothelium of systemic capillaries
occurs because of pressure differences of each gas between systemic (oxygenated) blood & interstitial fluid
results in creation of deoxygenated blood

30. Gas Transport - O2
During external respiration O2 diffuses across respiratory membrane into blood plasma
The majority of O2 (98.5%) then immediately diffuses into RBCs & binds (loosely) to the iron (Fe+3) in hemoglobin for transport
only 1.5% is transported freely dissolved within plasma

31. Gas Transport – CO2
During internal respiration CO2 diffuses from interstitial fluid into plasma
Only 7% of CO2 remains in plasma for transport, the rest diffuses into RBCs
Within RBCs 23% binds to the globin proteins of hemoglobin (Hb) (“carbaminohemoglobin”)
Most (70%) of CO2 gets converted within RBCs to bicarbonate ions (HCO3-) – CO2 + H2O H2CO3 (carbonic acid) HCO3- + H+
HCO3- diffuses out to plasma (as Cl- diffuses in); the H+ attach to Hb to maintain normal plasma pH (so plasma does not become too acidic)

32. Control of Respiration
Unconscious control of breathing occurs through the activity of the respiratory centers of the brain
Medulla oblongata – “Rhythmicity center” controls basic pattern of breathing; inhale 2 seconds, exhale 3 seconds
Pons – has 2 centers (apneustic & pneumotaxic centers) that can unconsciously modify the rate & depth of respiration
Respiratory centers can be influenced by mechanoreceptors (i.e. stretch receptors in lungs) & chemoreceptors (sensitive to CO2 levels, arterial pH, & O2 levels) in the body, as well as by higher brain centers