Friday, June 29, 2012

Biological Science 11 (Respiratory System)

Biological Science 11 (Respiratory System)

Day 20:

A. Respiratory System
The respiratory system works with the cardiovascular system, to supply the oxygen needed for cellular respiration, which creates the energy necessarily for human life (ATP).

1. General Structure and Function
The respiratory system takes air from the environment, warming it in the nose or mouth (nasal or oral cavities), moistening it and filtering pathogens out of it in the pharynx (throat), the air travels into the larynx (voice box), the trachea (wind pipe), the bronchi of the lung (left or right), down smaller and smaller tubes, into the aveoli where the oxygen in the air is passed into the capillaries in return for waste carbon dioxide (which begins the reverse path to the outside environment).

The Respiratory System

A. Gas Exchange, Thermoregulation
The oxygen is exchanged for carbon dioxide, between the alveolar sacs and capillaries. Thermoregulation by the respiratory system occurs due to heat loss (due to exhaling warm air).

The diffusion of oxygen follows Henry's law, that states an equilibrium constant of the dissolved amount of oxygen is proportional to the partial pressure of the oxygen just above the surface of the solution.

B. Protection Against Disease, Particulate Matter
The nose hair grabs large particles and sweeps them out of the respiratory track along with mucus. Thin cilia help move particles out of the respiratory track. Healthy alveoli have white blood cells (macrophages) to kill invaders.

2. Breathing Mechanisms
The act of breathing out is effortless, since the atmosphere has less pressure then our full lungs, air rushes out. Breathing in requires contraction of the diaphragm. The concept is called negative pressure breathing.

A. Diaphragm, Rib Cage, Differential Pressure
The diaphragm is a dome shaped muscle that helps the lungs expand. The rib cage has muscles (the external and internal intercostals) that also help with breathing. The rib cage usually keeps the lungs from collapsing. Our lungs always have a pressure that keeps them from collapsing. Airflow follows lower pressure.

B. Resiliency and Surface Tension Effects
Healthy lungs are elastic, springing back after each breath. Too much surface tension would collapse the lung's air sacks (alveoli), surfacant (soap) produced by the lung, keeps this from happening. In emphysema the surfacant is missing and many air sacks collapse making breathing very strenuous (like checking out at a big store with only one cashier left).

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