Biology 101 - Respiratory System and Tissues Part 2

vital capacity Vital capacity is the largest volume that can possibly be inhaled or exhaled.

Residual volume Since the residual volume never leaves the lungs, it cannot be directly measured, but must be calculated using the other lung volumes.

Total lung capacity (TLC) includes the entire volume of air that can be held in the lungs. Vital capacity (VC) only includes the volume that can be inhaled or exhaled. TLC is equal to the sum of vital capacity and residual volume.

Total lung capacity and expiratory reserve volume. ERV, IRV, and tidal volume can be added to find vital capacity. From there, residual volume can be found by subtracting vital capacity from total lung capacity.

mucus In the respiratory tract, mucus functions as part of the innate immune system. Mucous membranes also exist in the stomach.

Cilia, small hairlike organelles that line much of the respiratory tract, are composed of microtubules. Cilia function to protect the lungs by moving mucus and particles toward the throat.

Macrophages While macrophages exist throughout the body, specialized cells known as alveolar macrophages are present only in the lungs. If exposed to a pathogen, these cells can perform phagocytosis and release factors that activate other immune cells.

The bicarbonate buffer functions according to this equation and is the main homeostatic method of maintaining constant pH in the blood.

The equation for the bicarbonate buffer is reversible, meaning that it can progress in either direction to reach an equilibrium.

carbonic acid

| (H2CO3)

Carbonic acid is often confused with bicarbonate (HCO3-), since the "bi" prefix can be misunderstood to mean "two" protons. It's important to remember that bicarbonate is actually the conjugate base of carbonic acid.

Low pH, or acidity, in the blood results in an increased respiratory rate.

Consider the equilibria involved in the blood buffer:

H2O + CO2 ⇔ H2CO3 ⇔ H+ + HCO3-

Acidic blood has a high proton concentration, which will shift the reaction to the left to regain equilibrium. This will result in the production of water and carbon dioxide. To excrete this additional CO2, breathing rate must increase.

High blood pH, or alkalosis

More than any other factor, blood pH level depends on CO2 concentration. If respiratory rate is increased above normal levels, more CO2 will be exhaled than usual, and the bicarbonate buffer equilibrium will shift away from the production of hydrogen ions. With fewer protons, blood will become basic or alkaline.

Plasma pH would be unaffected.

While blood pH depends directly on CO2 concentration, its relationship to O2 levels is much more indirect. Oxygen is not part of the bicarbonate buffer system, so if all else remained the same, it would have no immediate effect on pH.

• aortic bodies

• carotid bodies

They function as chemoreceptors and signal the brain when O2 levels are low.

As part of the peripheral nervous system, the aortic body must first send an impulse to the brain, which can then increase respiratory rate.

Specifically, both the aortic and carotid bodies signal the medulla oblongata, which controls involuntary actions such as breathing.

Plasma CO2 levels (which determine plasma pH)

The brain contains its own chemoreceptors, but they monitor only blood pH and CO2 levels. These central receptors stimulate a stronger response than the peripheral bodies.

Epithelial tissue forms the external and internal linings of the body. Its main functions include protection and the facilitation of movement of materials between organs.

Specifically, epithelium can be specialized for absorption (as in the small intestine), secretion (as in the kidney) or diffusion (as in the alveoli), or it can serve multiple roles.

squamous, cuboidal, columnar Squamous epithelial cells are flat and thin, while cuboidal cells, as their name implies, appear cubelike. Columnar cells are significantly taller and rectangular.

• simple

• stratified

Simple epithelium consists of a layer that is a single cell thick, which is ideal for diffusion and absorption. Stratified epithelium consists of multiple tightly-packed layers and often serves protective purposes.