Physiology 13

Respiratory System

responsible for taking up oxygen from the environment and delivering it to the blood, as well as eliminating carbon dioxide from the blood

Steps of respiration

1. Pulmonary Ventilation

2. Exchange of O₂/CO₂ between alveolar air and blood in the lungs

3. Transport of gases through pulmonary and systemic circulation

4. Exchange O₂/CO₂ between the blood in tissue capillaries and cells of tissues

Functions of the respiratory system

• provides oxygen

• gets rid of CO₂ (waste product)

• regulates blood’s hydrogen

• helps in phonics (speech)

• helps to defend against microbes

• involved in arterial concentrations of proteins and 2nd messengers

• helps get rid of blood clots

What parts of the respiratory system has cartilage rings?

trachea and bronchi

Structures that comprise the airway

nose, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli

What are the two zones that the airway can be divided into beyond the larynx?

-Respiratory zone: extends from the respiratory bronchioles down and is the region where alveoli exchange gases with the blood

-Conducting zone: from the top of the trachea to the end of the terminal bronchioles, which contains no alveoli and does not exchange gases with the blood

• moistens/warms the air

• involved in phonics

• provides low resistance airway for air flow to the respiratory zone **

• defense/immunology

Ciliary mucus escalator

epithelial surfaces of the airways contain cilia that constantly beat upward toward the pharynx

also contain glands and individual epithelial cells that secrete mucus and macrophages that can phagocytize inhaled pathogens

keeps lungs clear of particulate matter and the many bacteria that enter the body on dust particles

What can kill the cilia?

noxious agents such as tobacco smoke

-this is why smokers often cough up mucus that the cilia would normally have cleared

Cystic Fibrosis

characterized by excess mucus in the lungs

-CFTR gene mutation that encodes for a chloride transporter so when this is mutated, water and chloride are not exiting the cells → thicker mucus

-patients are susceptible to pathogens because they cannot clear the mucus/get it out

-affects GI tract (malnutrition due to less absorption of nutrients)

-affects pancreas

-70% of cases have a deletion of phenylalanine

Alveoli

tiny, hollow sacs whose open ends are continuous with the lumina of the airways and serve as the site of gas exchange

-type 1 alveolar cells: form continuous layer (one cell thick) of flat epithelial cells

-type 2 alveolar cells: produce surfactant

Surfactant

produced by type 2 alveolar cells

decreases surface tension which is important for efficient gas exchange

Inspiration and Expiration are determined by pressure differences in what?

pressure differences between the pleura and fluid

Visceral vs. Parietal Pleura

visceral pleura: pleural surface coating the lung that is firmly attached to the lung by connective tissue

parietal pleura: outer layer of the pleural surface coating that is attached to and lines the interior thoracic wall and diaphragm

Intrapleural pressure

hydrostatic pressure of the intrapleural fluid

-changes in this pressure causes the lungs and thoracic wall to move in and out together during normal breathing

Ventilation

the exchange of air between the atmosphere and alveoli

-pressure differences between the atmosphere and alveoli determine flow

• if alveoli pressure < atmospheric pressure → air comes in (inspiration)

• if alveoli pressure > atmospheric pressure → air goes from lungs to outside the body (expiration)

Boyle’s Law

P1V1=P2V2

-relationship between pressure and volume is inversely proportional

• an increase in volume=more space=less pressure (expand lungs during inspiration)

• a decrease in volume=less space=more pressure (exhale lungs)

Transpulmonary pressure

the differences in pressure between the inside and outside of the lung; transmural (across a wall) pressure that governs the static properties of the lungs

P_tp=P_alv-P_ip

What happens when P_ip=P_alv?

pneumothorax: lungs collapse

Events during inspiration

-diaphragm and intercostal muscles contract

-thorax expands

-P_ip becomes more sub atmospheric

-increase in trans pulmonary pressure

-lungs expand

-P_alv because sub atmospheric

-air flows into the alveoli

Events during expiration

-diaphragm and intercostal muscles stop contracting

-chest wall recoils inward

-P_ip moves back toward pre inspiration value

-transpulmonary pressure move back toward pre inspiration value

-lungs recoil

-air in alveoli becomes compressed

-P_alv>P_atm

-air flows out of the lungs

Lung Compliance (C_L)

the magnitude of the change in lung volume produced by a given change in the trans pulmonary pressure

-greater the lung compliance the easier it is to expand the lungs at any given change in trans pulmonary pressure

-2 major determinants:

• stretchability of lung tissue

• surface tension at the air-water interfaces in alveoli

How does training affect compliance?

more training=more compliance=more expansion

Where does oxygen bind in RBCs?

heme group on iron (has 4 binding sites)

Carbon monoxide poisoning

carbon monoxide (CO) has an extremely high affinity for the oxygen binding sites in hemoglobin so more CO is binding than oxygen

-this decreases the unloading of oxygen from hemoglobin in the tissues

What structure in the brain is associated with controlling respiratory rate?

medulla oblongata

What drugs suppress medullary inspiratory neurons and what does this cause?

morphine, barbiturates, fentanyl, and heroin

death via overdose from these drugs can be due to cessation of breathing