unit 3 LECTURE - respiratory and digestive

what are the four processes of respiration?

1. Pulmonary ventilation

2. external respiration

3. transport

4. internal respiration

Which processes is gas exchange at the lungs? describe them

• Pulmonary ventilation: movement of air into/out lungs

• External respiration: exchange of O2/CO2 between lungs and blood

what processes of gas exchange happen in the blood?

• transport: O2 & CO2 → blood

• internal respiration: exchange of O2/CO2 between systemic blood vessels (capillary’s) and tissues

bronchial tree

23 orders of branching that air passes through

surfactant

produced by type 2 alveolar cells. reduces surface tension of alveolar fluid which prevents alveolar collapse.

conducting zone

up until the terminal/respiratory bronchioles. supported with cartilage to keep airways open.

respiratory zone

include terminal/respiratory bronchioles and alveoli.

where is the site of actual gas exchange?

at the respiratory zone. At the respiratory membrane

respiratory membrane

the wall of alveoli and capillary fused by basement membrane that allows for simple diffusion, since its very thin (0.5-1. μm /Micro)

what are the cells on the respiratory membrane?

• Type 1 alveolar cells : simple squamous epithelium. Where diffusion of gas occurs.

• Type 2 alveolar cells: secrete surfactant

• Macrophages: protective immune cells that help keep the alveolar surface sterile.

name the different types of pressures in thoracic cavity

• Atmospheric pressure (P_atm)

• Intrapulmonary pressure (P_pul)

• Intrapleural pressure (P_ip)

Atmospheric Pressure

outside pressure. ~760 mm Hg at sea level.

• negative respiratory pressure: ___ < 760 P_atm

• Positive respiratory pressure: ___ > 760 P_atm

• zero respiratory pressure: __= 760 P_atm

intrapulmonary pressure

pressure in alveoli. Flactuates with breathing. Eventually equalizes with Patm

Intrapleural pressure

pressure in the pleural cavity. Fluctuates with breathing but it is ALWAYS NEGATIVE to keep lungs inflated (prevent collapsing)

Atelectasis (pneumothorax)

lung collapse; air in the pleural cavity (therefore P_ip is no longer negative) because of a punctured parietal pleura or a ruptured visceral pleura (knife wound)

Boyle’s law

Volume and pressure are inversely related.

increase in volume= decrease in pressure // decrease in volume = a increase in pressure.

air/gas moves to equalize pressure.

When the diaphragm contracts….

the lungs increase in volume (breathing in)

what is the most important muscle for respiration?

the diaphragm

paralysis of the diaphragm results in …

death

When the diaphragm in relaxed

the lungs decrease in volume (breathing out)

pressure always goes from:

high to low or low to high ?

high to low

inspiration

is an active process because it involves inspiratory muscles contraction (external intercostal and diaphragm)

expiration

passive process. inspiratory muscles relax, lung volume decreases and recoil.
P_pul > P_atm so air flows out of lungs to equalize.

what are the physical factors that influence pulmonary ventilation?

• airway resistance

• alveolar surface tension

• lung compliance

airway resistance

diameter of airways (conducting zone has cartilage therefore stays constant.)

pathology of air way resistance and treatment

acute asthma attacks. treated with bronchiodilators (epinephrine).

alveolar surface tension

surfactant reduces surface tension of alveolar fluid (thin water layer on walls) which prevents alveolar collapse.

Infant respiratory distress syndrome (IRDS)

not enough surfactant in premature babies so alveolar collapse.

treatment: synthetic surfactant

lung compliance

measure of lung elasticity/stretch

higher compliance = easier expansion

normally high because of distensibility of lung tissues and surfactant

fibrosis

nonelastic scar tissue replacement (usually because of chronic smokers)

tidal volume (TV)

amount of air moving into/out of lungs with each breath (at rest)

~500 ml

FEV1: FVC ratio

80%

total volume exhaled with max effort

obstructive disease

limit of airflow during expiration.

LOWER than 80% ratio

restrictive disease

deformity or loss of elasticity (lower compliance)=lower total lung capacity. resulting in HIGHER than 80% ratio

external respiration

diffusion of gases between BLOOD and LUNGS

internal respiration

diffusion of gases between BLOOD and TISSUES

what is external respiration influenced by

1. partial pressure gradients (concentration difference) and gas solubility

2. thickness and surface area of the respiratory membrane

3. ventilation-perfusion coupling

CO2 is more/less soluble than O2?

20X more soluble

partial pressure gradient and gas solubility

steep partial pressure for O2

venous= 40 mm Hg Alveolar= 104 mm Hg

higher pressure in alveoli drives oxygen into lower pressure in venous/blood.

less steep for CO2 but still diffuses in equal amounts with O2 because its more soluble.

venous= 45 mm Hg alveolar= 40 mm Hg

higher pressure to lower pressure + solubility = equal diffusion.

thickness and surface area of respiratory membrane

respiratory membrane is very thin (0.5-1 micrometers)

Large total surface area of alveoli (40X more than skin)

Emphysema

reduction of alveolar surface area by wall breakdown and chamber enlargement

pneumonia / pulmonary edema

increased thickness of the respiratory membrane because of added layer of water.

ventilation perfusion coupling

increased blood flow to alveoli is matched by increased gas flow to alveoli,LOCAL AUTOREGULATORY mechanism

high O2= arterioles dilate

internal respiration

gas exchange at the tissues

how is oxygen transported in blood?

by hemoglobin

what factors affect hemoglobin saturation?

• P_o2

• temperature

• blood pH

• P_co2

• concentration of BPG

all DIRECTLY related.

Increases when ACTIVE and shifts the O2-hemoglobin dissociation curve to the RIGHT. meaning unloading of O2

Decrease shifts to the left.

hypoxia

inadequate O2 delivery to tissues.

anemic hypoxia

little amount of RBC’s meaning not enough hemoglobin (Hb found in RBC’s)

ischemic hypoxia

impaired/blocked circulation

histotoxic hypoxia

cells are unable to use O2 (low o2 in atmosphere)

carbon monoxide poisoning

deadly.

carbon monoxide has a 200X greater affinity with hemoglobin than with oxygen (competing)

how is carbon dioxide transported in blood?

as bicarbonate ions in plasma