respiratory

Question 1

Structurally
❑ Upper respiratory system
◼ Nose, pharynx and associated structures
❑ Lower respiratory system
◼ Larynx, trachea, bronchi and lungs
Functionally
❑ Conducting zone – conducts air to lungs
◼ Nose, pharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles
❑ Respiratory zone – main site of gas exchange
◼ Respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli

Answer 1

Respiratory System Anatomy

Question 2

External nose – portion visible on face
❑ Internal nose – large cavity beyond nasal vestibule
❑ Internal nares or choanae
❑ Ducts from paranasal sinuses and nasolacrimal ducts open into internal nose

Answer 2

Nose

◼ Nasal cavity divided by nasal septum
◼ Nasal conchae subdivide cavity into meatuses
❑ Increase surface are and prevents dehydration
◼ Olfactory receptors in olfactory epithelium

Question 3

❑ Starts at internal nares and extends to cricoid cartilage of
larynx
❑ Contraction of skeletal muscles assists in deglutition

❑ Functions
◼ Passageway for air and food
◼ Resonating chamber
◼ Houses tonsils

Answer 3

Pharynx

❑ 3 anatomical regions
◼ Nasopharynx
◼ Oropharynx
◼ Laryngopharynx

Question 4

Short passageway connecting laryngopharynx with trachea
❑ Composed of 9 pieces of cartilage

◼ Thyroid cartilage or Adam’s apple
◼ Cricoid cartilage hallmark for tracheotomy
❑ Epiglottis closes off glottis during swallowing
❑ Glottis – pair of folds of mucous membranes, vocal folds(true vocal cords, and rima glottidis (space)
❑ Cilia in upper respiratory tract move mucous and trapped
particles down toward pharynx
❑ Cilia in lower respiratory tract move them up toward
pharynx

Answer 4

Larynx

Question 5

❑ Function in holding breath against pressure in thoracic

cavity

Answer 5

Ventricular folds (false vocal cords) – superior pair

Question 6

Muscle contraction pulls elastic ligaments which stretch
vocal folds out into airway
❑ Vibrate and produce sound with air
❑ Folds can move apart or together, elongate or shorten,
tighter or looser

Answer 6

Vocal folds (true vocal cords) – inferior pair

Androgens make folds thicker and longer – slower
vibration and lower pitch

Question 7

Extends from larynx to superior border of T5
◼ Divides into right and left primary bronchi
❑ 4 layers
◼ Mucosa
◼ Submucosa
◼ Hyaline cartilage
◼ Adventitia
❑ 16-20 C-shaped rings of hyaline cartilage
◼ Open part faces esophagus

Answer 7

Trachea

Question 8

❑ Right and left primary bronchus goes to right lung
❑ Carina – internal ridge
◼ Most sensitive area for triggering cough reflex
❑ Divide to form bronchial tree
◼ Secondary lobar bronchi (one for each lobe), tertiary
(segmental) bronchi, bronchioles, terminal bronchioles

Answer 8

Bronchi

❑ Structural changes with branching
◼ Mucous membrane changes
◼ Incomplete rings become plates and then disappear
◼ As cartilage decreases, smooth muscle increases

❑ Sympathetic ANS – relaxation/ dilation
❑ Parasympathetic ANS – contraction/ constriction

Question 9

Separated from each other by the heart and other
structures in the mediastinum
❑ Each lung enclosed by double-layered pleural membrane
◼ Parietal pleura – lines wall of thoracic cavity
◼ Visceral pleura – covers lungs themselves
❑ Pleural cavity is space between layers
◼ Pleural fluid reduces friction, produces surface tension (stick
together)
◼ Cardiac notch – heart makes left lung 10% smaller
than right

Answer 9

Lungs

Question 10

Lobes – each lung divides by 1 or 2 fissures
❑ Each lobe receives it own secondary (lobar) bronchus that branch into tertiary (segmental) bronchi
◼ Lobules wrapped in elastic connective tissue and contains a lymphatic vessel, arteriole, venule and
branch from terminal bronchiole

◼ Terminal bronchioles branch into respiratory
bronchioles which divide into alveolar ducts
◼ About 25 orders of branching

Answer 10

Anatomy of Lungs

Question 11

Cup-shaped outpouching
❑ Alveolar sac – 2 or more alveoli sharing a
common opening

Answer 11

Alveoli

Question 12

❑ 2 types of alveolar epithelial cells

Answer 12

◼ Type I alveolar cells – form nearly continuous lining,
more numerous than type II, main site of gas exchange

◼ Type II alveolar cells (septal cells) – free surfaces
contain microvilli, secrete alveolar fluid (surfactant
reduces tendency to collapse)

Question 13

❑ Alveolar wall – type I and type II alveolar cells
❑ Epithelial basement membrane
❑ Capillary basement membrane
❑ Capillary endothelium
❑ Very thin – only 0.5 µm thick to allow rapid diffusion of gases

Answer 13

Respiratory membrane

Question 14

Lungs receive blood from

Answer 14

❑ Pulmonary artery - deoxygenated blood
❑ Bronchial arteries – oxygenated blood to perfuse muscular
walls of bronchi and bronchioles

Question 15

◼ Respiration (gas exchange) steps

Answer 15

1. Pulmonary ventilation/ breathing
   ◼ Inhalation and exhalation
   ◼ Exchange of air between atmosphere and alveoli
2. External (pulmonary) respiration
   ◼ Exchange of gases between alveoli and blood
3. Internal (tissue) respiration
   ◼ Exchange of gases between systemic capillaries and
   tissue cells
   ◼ Supplies cellular respiration (makes ATP)

Question 16

Pressure inside alveoli lust become lower than
atmospheric pressure for air to flow into lungs
◼ 760 millimeters of mercury (mmHg) or 1
atmosphere (1 atm)
❑ Achieved by increasing size of lungs
◼ Boyle’s Law – pressure of a gas in a closed
container is inversely proportional to the volume of
the container
❑ Inhalation – lungs must expand, increasing lung
volume, decreasing pressure below atmospheric
pressure

Answer 16

Inhalation/ inspiration

Question 17

Inhalation is active Contraction of
❑ Diaphragm – most important muscle of inhalation
◼ Flattens, lowering dome when contracted
◼ Responsible for 75% of air entering lungs during normal quiet breathing

❑ External intercostals
◼ Contraction elevates ribs
◼ 25% of air entering lungs during normal quiet breathing
❑ Accessory muscles for deep, forceful inhalation

Answer 17

Inhalation
◼ When thorax expands,
parietal and visceral pleurae adhere tightly due to subatmospheric pressure and surface tension –pulled along with expanding thorax
◼ As lung volume increases, alveolar (intrapulmonic) pressure drops

Question 18

Pressure in lungs greater than atmospheric pressure
❑ Normally passive – muscle relax instead of contract
◼ Based on elastic recoil of chest wall and lungs from elastic
fibers and surface tension of alveolar fluid
◼ Diaphragm relaxes and become dome shaped
◼ External intercostals relax and ribs drop down
❑ Exhalation only active during forceful breathing

Answer 18

Exhalation/ expiration

Question 19

◼ Air pressure differences drive airflow

◼ 3 other factors affect rate of airflow and ease of
pulmonary ventilation
1. Surface tension of alveolar fluid
-Causes alveoli to assume smallest possible diameter
- Accounts for 2/3 of lung elastic recoil
-Prevents collapse of alveoli at exhalation
2. Lung compliance
◼ High compliance means lungs and chest wall expand easily
◼ Related to elasticity and surface tension
3. Airway resistance
◼ Larger diameter airway has less resistance
◼ Regulated by diameter of bronchioles & smooth muscle tone

Answer 19

Airflow

Question 20

Lung volumes and capacities

Answer 20

Minute ventilation (MV) = total volume of air
inhaled and exhaled each minute
◼ Normal healthy adult averages 12 breaths
per minute
◼ moving about 500 ml of air in and out of lungs
(tidal volume)
◼ MV = 12 breaths/min x 500 ml/ breath
= 6 liters/ min

Question 21

Lung Volumes

Total lung capacity = vital capacity + residual
volume

Answer 21

Only about 70% of tidal volume reaches respiratory
zone
◼ Other 30% remains in conducting zone
◼ Anatomic (respiratory) dead space – conducting
airways with air that does not undergo respiratory
gas exchange
◼ Alveolar ventilation rate – volume of air per minute
that actually reaches respiratory zone
◼ Inspiratory reserve volume – taking a very deep
breath

Question 22

inhale normally

and exhale forcefully

Answer 22

◼ Expiratory reserve volume

Question 23

air remaining after

expiratory reserve volume exhaled

Answer 23

Residual volume

Question 24

inspiratory reserve volume +

tidal volume + expiratory reserve volume

Answer 24

Vital capacity

Question 25

❑ Each gas in a mixture of gases exerts its own pressure as if no other gases were present ❑ Pressure of a specific gas is partial pressure Px ❑ Total pressure is the sum of all the partial pressures ❑ Atmospheric pressure (760 mmHg) = PN2 + PO2 + PH2O + PCO2 + Pother gases ❑ Each gas diffuses across a permeable membrane from the are where its partial pressure is greater to the area where its partial pressure is less ❑ The greater the difference, the faster the rate of diffusion

Answer 25

Dalton’s Law | Exchange of Oxygen and Carbon Dioxide

Question 26

❑ Quantity of a gas that will dissolve in a liquid is proportional to the partial pressures of the gas and its solubility ❑ Higher partial pressure of a gas over a liquid and higher solubility, more of the gas will stay in solution ❑ Much more CO2 is dissolved in blood than O2 because CO2 is 24 times more soluble ❑ Even though the air we breathe is mostly N2 , very little dissolves in blood due to low solubility ◼ Decompression sickness (bends)

Answer 26

Henry’s law

Question 27

External Respiration in Lungs

Answer 27

❑ Oxygen diffuses from alveolar air (PO2 105 mmHg) into blood of pulmonary capillaries (PO2 40 mmHg) ❑ Diffusion continues until PO2 of pulmonary capillary blood matches PO2 of alveolar air ❑ Small amount of mixing with blood from conducting portion of respiratory system drops PO2 of blood in pulmonary veins to 100mmHg ◼ Carbon dioxide ❑ Carbon dioxide diffuses from deoxygenated blood in pulmonary capillaries (PCO2 45 mmHg) into alveolar air (PCO2 40 mmHg) ❑ Continues until of PCO2 blood reaches 40 mmHg

Question 28

Internal Respiration

Answer 28

Internal respiration – in tissues throughout body ◼ Oxygen ❑ Oxygen diffuses from systemic capillary blood (PO2 100 mmHg) into tissue cells (PO2 40 mmHg) – cells constantly use oxygen to make ATP ❑ Blood drops to 40 mmHg by the time blood exits the systemic capillaries ◼ Carbon dioxide ❑ Carbon dioxide diffuses from tissue cells (PCO2 45 mmHg) into systemic capillaries (PCO2 40 mmHg) – cells constantly make carbon dioxide ❑ PCO2 blood reaches 45 mmHg ◼ At rest, only about 25% of the available oxygen is used ❑ Deoxygenated blood would retain 75% of its oxygen capacity

Question 29

Rate of Pulmonary and Systemic Gas Exchange

Answer 29

◼ Depends on ❑ Partial pressures of gases ◼ Alveolar PO2 must be higher than blood PO2 for diffusion to occur – problem with increasing altitude ❑ Surface area available for gas exchange ❑ Diffusion distance ❑ Molecular weight and solubility of gases ◼ O2 has a lower molecular weight and should diffuse faster than CO2 except for its low solubility - when diffusion is slow, hypoxia occurs before hypercapnia

Question 30

❑ Only about 1.5% dissolved in plasma ❑ 98.5% bound to hemoglobin in red blood cells ◼ Heme portion of hemoglobin contains 4 iron atoms –each can bind one O2 molecule ◼ Oxyhemoglobin ◼ Only dissolved portion can diffuse out of blood into cells ◼ Oxygen must be able to bind and dissociate from heme

Answer 30

Oxygen transport

Question 31

Relationship between Hemoglobin and | Oxygen Partial Pressure

Answer 31

Higher the PO2, More O2 combines with Hb ❑ Fully saturated – completely converted to oxyhemoglobin ❑ Percent saturation expresses average saturation of hemoglobin with oxygen ❑ Oxygen-hemoglobin dissociation curve ◼ In pulmonary capillaries, O2 loads onto Hb ◼ In tissues, O2 is not held and unloaded ❑ 75% may still remain in deoxygenated blood (reserve)

Question 32

Other factors affecting affinity of Hemoglobin | for oxygen

Answer 32

``` ◼ Each makes sense if you keep in mind that metabolically active tissues need O2 and produce acids, CO2 and heat as wastes ❑ Acidity ❑ PCO2 ❑ Temperature ```

Question 33

Bohr Effect

Answer 33

``` ❑ As acidity increases (pH decreases), affinity of Hb for O2 decreases ❑ Increasing acidity enhances unloading ❑ Shifts curve to right ◼ PCO2 ❑ Also shifts curve to right ❑ As PCO2 rises, Hb unloads oxygen more easily ❑ Low blood pH can result from high PCO2 ```

Question 34

Temperature Changes

Answer 34

``` ❑ Within limits, as temperature increases, more oxygen is released from Hb ❑ During hypothermia, more oxygen remains bound ◼ 2,3-bisphosphoglycerate ❑ BPG formed by red blood cells during glycolysis ❑ Helps unload oxygen by binding with Hb ```

Question 35

Fetal and Maternal Hemoglobin

Answer 35

◼ Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin ◼ Hb-F can carry up to 30% more oxygen ◼ Maternal blood’s oxygen readily transferred to fetal blood

Question 36

Carbon Dioxide Transport

Answer 36

❑ Dissolved CO2 ◼ Smallest amount, about 7% ❑ Carbamino compounds ◼ About 23% combines with amino acids including those in Hb ◼ Carbaminohemoglobin ❑ Bicarbonate ions ◼ 70% transported in plasma as HCO3- ◼ Enzyme carbonic anhydrase forms carbonic acid (H2CO3) which dissociates into H+ and HCO3

Question 37

❑ HCO3 - accumulates inside RBCs as they pick up carbon dioxide ❑ Some diffuses out into plasma ❑ To balance the loss of negative ions, chloride (Cl-) moves into RBCs from plasma ❑ Reverse happens in lungs – Cl- moves out as moves back into RBCs

Answer 37

◼ Chloride shift | CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3