Respiratory System & Gas Exchange

Gas Exchange and Homeostasis

• The respiratory system aids in homeostasis by enabling the swap of oxygen and carbon dioxide between atmospheric air, blood, and tissue cells.
• It also helps regulate the pH of body fluids.

Gas Exchange in Humans

• Gas exchange is essential for harvesting energy from food molecules.
• The three key phases are breathing, gas transport, and gas exchange.
• Inhalation brings air into lungs, facilitating oxygen and carbon dioxide diffusion between blood and lungs. Exhalation removes carbon dioxide.
• Oxygen molecules attach to hemoglobin in red blood cells for transport through the blood. Carbon dioxide is also transported in blood in various forms.
• In cells, oxygen from the blood supports cellular respiration within mitochondria. This process generates carbon dioxide, which is expelled into the blood as waste.

Gas Exchange Surfaces

• The respiratory surface is the site for gas exchange, composed of a single layer of moist cells.
• Moisture is vital for gas exchange.
• Diffusion is key.
• The respiratory surface area must be large enough to accommodate the body's oxygen demands.
• Ventilation is the flow of air across the respiratory surface.
• Lungs feature subdivisions for maximum surface area.

Mammalian Respiratory System

• Lungs are located in the thoracic cavity, safeguarded by the rib cage.
• The diaphragm separates the thoracic and abdominal cavities.
• The main components are the nose, pharynx, larynx, trachea, bronchi, and lungs.
• The larynx, or voice box, connects the pharynx to the trachea.
• Vocal folds in the larynx stretch by laryngeal muscles to control sound production.
• Air exhaled causes the vocal cords to vibrate.
• The pitch depends on the tension of the vocal folds.
• The pharynx, mouth, and nasal cavity work together to create recognizable speech.
• Rings of cartilage keep the trachea, larynx, and bronchi open.
• The trachea branches into two bronchi.
• Each bronchus branches into smaller tubes called bronchioles.
• Branches possess epithelium with mucus and cilia for cleaning. More extensive branching leads to reduced cartilage and non-ciliated cells.
• Bronchitis is a condition in which the small tubes become inflamed and constricted, making breathing difficult.

Alveoli

• Alveoli are grapelike air sacs grouped at the end of bronchioles.
• Alveolar structure supports effective gas exchange.
• Alveoli provide a substantial surface area for gas exchange.
• A thin layer of epithelial cells lines each alveolus.
• Alveolar cells secrete a moist fluid.
• A dense network of blood capillaries surrounds alveoli.

Negative Pressure Breathing

• Respiratory distress syndrome (RDS) can occur in premature newborns from a lack of surfactant.
• Emphysema results from contaminants such as cigarette smoke, which causes continual inflammation in the lungs.
• The continual inflammation destroys the walls of alveoli and decreases the effectiveness of gas exchange.
• Chronic bronchitis is the long-term inflammation of the the small airways stemming from exposure contaminants such as cigarette smoke.
• Pulmonary ventilation, or breathing, involves air flowing in and out of the lungs, that occurs thanks to inhalation and exhalation.
• The constant flow of air upholds specific concentrations of O2 and CO2 at the respiratory surface.
• Negative pressure breathing occurs as a system in which air is pulled, not pushed, into the lungs.
• Air tends to move from regions of higher pressure to regions of lower pressure, going down a pressure gradient.
• The lung volume influences intra-alveolar pressure, matching Boyle's law.
• Air moves into the lungs when the internal pressure is less than atmospheric pressure, and air moves when it is greater.
• Ventilation relies on the diaphragm, intercostal muscless, and pleura.
• The pleural membrane connects the lungs to the thoracic cavity and binds to the lung via the visceral pleura.
• Pressure in the lungs always stays negative, regardless of if it's inhalation or exhalation.
• During inhalation, contraction of the diaphragm and additional contraction of the external intercostals results in the expansion of the thoracic cavity, and therefore, the lungs.
• During exhalation, relaxation of the diaphragm and external intercostals results in the elastic recoil of the chest wall and lungs.
• Different amounts of air can be classified into lung volumens and used with a spirometer.
• A combination of multiple lung volumes is called lung capacity
• Volume of aid inhaled or exhaled with each breath is called the tidal volume.

Breathing Control

• Breathing constantly occurs in a continuous pattern to sustain life.
• Breathing happens using the diaphragm and intercostal musclels
• It's important to contract and relax the inspiratory muscles so that the lungs can be filled and emptied with air.
• Most often, breathing happens involuntarily, but you retain the capability to consciously control breathing for tasks such as exercising and swimming.
• Breathing involves blood circulation and metabolic demand.
• Breathing rhythm comes from the breathing control center, located in the medulla.
• The medulla controls all nerve activity and sends pulses to the intercostal and diaphragm.
• Automatic breathing activity centers around chemicals stimulation.
• The most common stimulus involves the increasing arterial partial pressure of CO2.
• The pressure increase can cause hydrogen levels to also increase, which affects the medulla oblongata.
• The body has peripheral that respond to changes in arterial P CO2, [H+] and P
• These are located in the aortic and cartoid bodies within blood vessels.
• These bodies have very luttle effect on breathing rate, which can become life threatening if it falls below 60mm Hg.
• Ventilation rate and depth adjusts via the negative feedback mechanism.
• the regulation of CO2 within the body affects how much CO2 is in the spinal fluid, which is then sensed by the brain
• The sensors will then either release or absorb CO2.

Blood Transportation of Gasses

• Circulation plays an important role in respiratory gasses
• oxygen increases with the rise in the lungs, while CO2 is transferred out
• Blood returns to the heart after the process, and returns those compounds through the body
• The exchanges of gasses occurs due to the diffusion of gasses within pressure gradients.
• Dalton's law demonstrates how gasses work through pressure. Daltons law : each gas in the mixing chamber exerts a pressure that is equivalent to its concentration.
• Henry's law describes its partial pressure, as well as the total gas amount that may dissolve in liquid.
• Gasses that exert partial pressure on the blood refer to the gas molecule quantity available.
• Partial pressure is lower relative to the areas if exertion.

Hemoglobin

• The hemoglobin makes it possible to help bind with reversible molecules of O2.
• With more O2, hemoglobin is able to bind further
• At a certain point, 98% saturated with O2 is reached, which occurs inside the lungs
• 70% saturation occurs during rest as a result of the O2 being unloaded via diffusion to tissue cells.
• Oxygen that isn't bound and instead passes to the blood is dissolved directly.
• Most Of the oxygen combines with the hemoglobin and exists within the RBCs. -Hemoglobin is able to binds with molecules, which creates a saturated result.
• The hemoglobin affinity may change depending on certain factors
• When at rest, this bond can break and disperse to cell tissues that can also become saturated.
• There are three forms in which CO2 moves
• the first being when the compound is dissolved straight into the blood (8%)
• the second being the instance of RBCs absorbing CO2 (20%)
• the third involves the RBCs causing a reaction that creates a number of compounds (72%)
• the majority links themselves to the hemoglobin which controls and minizmies PH levels in the blood.

Fetus Blood Exchanges

• There are certain instances in where compounds have a need to transfer from mother to fetus
• This occurs within certain arteries via an area known as intervillous space.
• Also passes into the umbilical cord
• If fetus is deoxygenated, transfers can occur via fetal capillaries

Fetal Hemoglobin

• has a greater affinity for O2 than adult hemoglobin
• allows 80-90 % saturation of the fetal hemoglobin even when under low pressure.
• This is a result of its ability to take in the most O2 possible under a low environment
• Avoid smoking during pregnancy, since exposure can affect not only the lungs, and the reduction of O2 transfer.
• Also reduces O2 supply to placenta
• Can result in organ damage, premature, and low birth weight.
  • Births can also prompt:
• An adaptation to the respiratory system, after the child no longer has a need to remove CO2
• As result;
• The muscles being to contract, leading to its first breath