RESPIRATORY SYSTEM

Lecture Notes:

I. Primary functions

A. Gas exchange (oxygen follows gradient in and carbon dioxide follows gradient out)

B. Regulate pH of blood (by removing carbon dioxide then carbonic acid production is reduced)

C. Vocalization

D. Olfaction

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II. Histology of respiratory system

A.Hyaline cartilage (and bone). Cartilage found in nose, larynx, trachea and bronchi. Bone found surrounding nasal cavities and pharynx. Both serve to maintain open airway.
B. Ciliated pseudostratified columnar epithelium with goblet cells. Respiratory epithelium lines nasal cavity, sinuses, pharynx, larynx, trachea and bronchus. Produces mucus and moves mucus with cilia to warm, moisten and removs debris and pathogens from air.
C. Cuboidal epithelium and smooth muscle. Lines the bronchioles. Smooth muscle allows bronchodilation and bronchoconstriction to regulate airflow.
D. Simple squamous epithelium. Forms alveoli (air sacs). Allows gas exchange.

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Describe how each tissue is used in the respiratory system-Draw and diagram each tissue.

III Organs of respiratory system

A. Air conduction organ1. Nasal passages/sinuses a. Lined with ciliated columnar epithelium with goblet cells

b. Functions

1) Moisten and warm air

2) Sticky mucosal epithelium (ciliated columnar epithelium with goblet cell ) removes foreign objects from air

3) Pass air by olfactory epithelium for smell

4) Provided hollows for vocalization
 
 

2. Pharynx
common tube for respiratory and digestive systems allowing food and air flow to the larynx.

3. Larynx

a. Structure
mostly hyaline cartilage box with elastic cartilage covering (epiglottis). Also has folds of elastic connective tissue (vocal cords).

b. Function

1) epiglottis prevents movement of water and food into trachea

2) Voice production by vibrating vocal folds

4. Trachea a. Structure
tube of ciliated columnar epithelium with goblet cell supported by C-shaped cartilages which keep
trachea from collapsing

b. Function

1) air conduction

2) remove debris/microbes by moving mucus

5. Bronchii a. Structure 1) Large hyaline cartilage supported extensions of trachea

2) Branch into two R & L bronchii for R & L lobes of lung

b. Function
air conduction/treatment

Labeled endoscopy video of respriatory conduction organs

B. Regulatory organ

1. Bronchioles a. Structure 1) No cartilage but more smooth muscle

2) Cuboidal epithelium lines lumen

b. Function 1) Alter air flow (bronchiodilation & bronchoconstriction via smooth muscle tissue). Increased short term stress (Sympathetic stimulation) increases Norepinephrine that causes bronchodilation so more oxygen into blood.

C. Respiratory (gas exchange) organ

1.  alveolusa. Structure
simple squamous epithelial cells (Type I alveolar cells) provides very
thin barrier between respiratory and cardiovascular systems

b. Function= gas exchange

2. Lobule (cluster of alveoli) a. Capillaries (CV and lymphatic) around alveoli

b. Septal cells (Type II alveolar cells) produce surfactant--a fluid that acts as lubricant coating alveolar walls allowing them to expand/contract while not sticking to each other

c. Resident macrophages to resist infection

d. Elastic CT packaging alveolar sacs, allows elastic rebound of alveoli.

List the organs through which air passes, including alveoli. Describe the histological and anatomical characters. Give functions for each organ.
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IV. Ventilation A. Organs 1. Lungs a. Paired organs in thoracic cavity surrounded by 2-layered serous membrane (pleura)
one layer on thoracic cavity wall and other on outside of lung with space between (pleural cavity) filled with lubricating serous fluid for easier breathing due to decreased friction

b. Heavy pulmonary cardiovascular supply

2. Inspiratory muscles-increase thoracic cavity volume
Diaphragm -cone-shaped muscle when relaxed but flattens and pulls down when contracted
Intercostal muscles-elevates ribs

B. Physiology 1. Pressures in thoracic cavity a. Intrapulmonary (inside alveoli) - ambient

b. intrapleural pressure (inside pleural cavity) always less than ambient ( negative pressure) so lungs stick to thorax wall and diaphragm

c. Increase thoracic volume (contract inspiratory muscles ) thereby pulling lungs out and expanding alveoli

d. If pleural cavity has hole (no negative pressure) and lungs collapse (= pneumothorax)
 
 

2. Forces that drive normal ventilation
Inhalation due to active contraction of respiratory muscles
exhalation passive due to elastic rebound of lung tissues
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3. Ventilation
a. rate (number of breaths per minute) ...about 12
b. Tidal Volume = ventilations/minute x volume/ventilation (=vol/min) ...about 500 ml

4. . Pulmonary volume

a. at rest , 12 x 500 ml = 6 L/min

b. During exercise, rate goes up, volume goes up=200 L/min


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C. Regulation of Respiration

1.. Basic tidal rhythm (neural neural feedback loop)
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respiratory centers in medulla oblongata and pons control basic tidal rhythm based on information from chemoreceptors in aorta and carotid arteries. Respiratory muscles, such as diaphragm, are effectors.

2. Modifying respiration rate

a. Conscious control (changes in ventilation due to speaking, singing, etc)

b. Emotional state at hypothalamus (increased sympathetic norepinephrine acting on diaphragm)

c. Proprioreceptors (exercise)

d. Chemical (nervous negative feedback loops)
impulses from chemoreceptors for O2, CO2 and pH in carotid arteries stimulate medullary control centers which send motor signals to respiratory muscles.

stimulus and response to nervous feedback loops:
if increase CO2 and H+ (low pH) or decreased O2 then increased ventilation rate
if decreased CO2 and H+ (high pH) or increased O2 then decreased ventilation rate

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Describe the mechanisms of inhalation and exhalation. Desribe how different factors effect the basic tidal rhythm.IV. Physiology of Respiration A. Measurement of gases 1. Gases in atmosphere 78% N2, 21% O2, 0.04% CO2

2. Pressure developed by gas is % x total pressure (760mm Hg)
(i.e., partial pressure)
78% x 760 = 600 mm Hg = PN2
21% x 760 = 160 mm Hg = PO2
0.04% x 760 = .3mm Hg = PCO2
pressures in alveoli and blood different
partial pressures are independent so gases can diffuse in opposite directions

B. Driving force of respiratory functions is cell respiration
O2 + Glucose = ATP + CO2 + H2O
This Reaction states " Oxidation of glucose (in the mitochondron, remember) is used to produce ATP with the side products of carbon dioxide and water".
As such, O2 needed by body cells, CO2 produced by body cells in tissues.
Cell respiration sets up the concentration gradients of these two gases, determining direction of exchange.

C. Exchange of gases at alveolus (external respiration)

Deoxygenated blood-low PO2, High PCO2
Atmosphere in alveoli-High PO2, Low PCO2
therefore net diffusion down gradients--O2 into blood, CO2 into alveoli
D. Exchange of gases at tissue (internal respiration)

oxygenated blood in capillaries (high PO2, low CO2)
extracellular fluids near tissue cells (low PO2, high CO2)
therefore diffusion of O2 into tissue fluids and CO2 into blood

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 Starting with the driving force of respiration describe the pressure gradients of both oxygen and carbon dioxide.

V. Transport of gases A. Oxygen 1. Almost all O2 carried by binding to iron atoms in heme groups of oxyhemoglobin molecule (HbO2)
Hb-H + O2= HbO2 + H+
Hb has affinity to O2 that varies by environment
 

2. Factors that control O2 unloading/loading with Hb

a. PO2 increases : affinity increases oxygen loaded onto hemoglobin
PO2 increases so more HbO2
highest PO2 in alveoli
therfore HbO2 formed at alveoli (O2 loaded)

lowest  PO2 in tissues
so oxygen unloaded

b. Temperature increases : affinity decreases
warm tempterature (at tissues) release O2 from HbO2

c. Blood pH decreases  : affinity decreases (BOHR EFFECT)
high PCO2
so HbO2 holds O2 less tightly so releases O2

d pH (higher pCO2 more acid)
so tissues with high PCO2 (more acid) Hb O2 breaks and
O2 is released (BOHR effect)
so at alveoli with low PCO2 (less acid) Hb O2 binds and O2 is loaded to form HbO2 (oxyhemoglobin)

e. 2,3 BPG increases : affinity decreases
2, 3 BPG result of anaerobic response of RBC (RBCs have no mitochondria & nucleus)

f. Other respiratory proteins

1) Myoglobin - variety of hemoglobin found in muscles
holds O2 much more strongly, i.e., higher affinity for O2

2) Fetal hemoglobin
Describe the conditions in which oxyhemoglobin is loaded and unloaded, identifying the locations that determine these conditions.

B. Carbon Dioxide
1. CO2 transport modes a. Little CO2 transported as dissolved in plasma (10%) but due to higher solubility, more than O2

b. Some (20%) transported as bound to globin of hemoblogin as carbaminohemoglobin (HbCO2)

c. Large amount (70%) is in bicarbonate ion form -HCO3  in plasma
 

2. HbCO2 binding/unbinding factors a. PCO2 increases so more HbCO2 formed (tissues)
so CO2 is removed from blood
PCO2 decreases so less HbCO2 formed (alveoli)
so CO2 is released into blood

b. PO2 increases so less HbCO2 (Haldane effect - reverse of Bohr effect)
Haldane reflects buffering ability of Hb to release [H+] which
combines with HCO3 to make H2CO3 to make H2O + CO2

3. Bicarbonate system a. Release of CO2 at tissues forms H2CO3 (carbonic acid) in RBC with help of carbonic anhydrase enzyme. Carbonic acid then breaks down to bicarb ions that diffuse into plasma (Cl-ions diffuse into RBC to equalized electrical gradient.

H20+ C02 =>H2C03 => H+ + HC03-

b. Bicarbonate ions bind with H ions to form CO2, which is expired at the alveoli.

H20+ C02<=H2C03 <= H+ + HC03-
Compare and contrast the various methods of carbon dioxide transport.Describe the conditions in which Carbaminohemoglobin is loaded and unloaded, identifying the locations that determine these conditions. Describe the conditions in which bicarbonate/carbonic acid are formed, identifying the locations in which each chemical is formed. H20+ C02<=H2C03 <= H+ + HC03-
Reaction states that "Increased carbon dioxide in water is converted to carbonic acid, which is broken to hydrogen ions and bicarbonate ions".The increased hydrogen ions acidify the fluid and bicarbonate ions are the primary form of carbon dioxide transport.

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VI. Role of respiratory system in blood pH regulation.
Nomal blood pH ranges from 7.35 to 7.45. Blood pH is monitored by chemoreceptors in carotid artery and aorta (vagus and glossopharangeal cranial nerves).

A. if low pH (excessive pC02) the increased ventilation-thereby reducing blood acidity.

B. if low pH (excessive pC02) the increased ventilation-thereby reducing blood acidity.Low levels (more alkaline blood pH) can be accumullated by reduced ventilation rate -thereby increasing blood acidigy.

Describe how the respiratory system regulates blood pH.

 
Professor Thomas M. Lancraft

Human Anatomy and Physiology Courses 
at St. Petersburg College
St. Petersburg/Gibbs Campus

5/2008