Page 205 - 84 human physiolofy part-1

The Respiratory System

the larynx is also pulled upwards to assist this process. Stimulation of the larynx by ingested matter
produces a strong cough reflex to protect the lungs. Note: choking occurs when the esophagus fails to
cover the trachea, and food becomes lodged in our windpipe.

The vocal cords consist of two folds of connective tissue that stretch and vibrate when air passes
through them, causing vocalization. The length the vocal cords are stretched determines what pitch the
sound will have. The strength of expiration from the lungs also contributes to the loudness of the
sound. Our ability to have some voluntary control over the respiratory system enables us to sing and to
speak. In order for the larynx to function and produce sound, we need air. That is why we can't talk
when we're swallowing.

Homeostasis and Gas Exchange

Homeostasis is maintained by the respiratory system in two ways: gas exchange and regulation of
blood pH. Gas exchange is performed by the lungs by eliminating carbon dioxide, a waste product
given off by cellular respiration. As carbon dioxide exits the body, oxygen needed for cellular
respiration enters the body through the lungs. ATP, produced by cellular respiration, provides the
energy for the body to perform many functions, including nerve conduction and muscle contraction.
Lack of oxygen affects brain function, sense of judgment, and a host of other problems.

Gas Exchange

Gas exchange in the lungs is between the alveolar air and the blood in the pulmonary capillaries.
This exchange is a result of increased concentration of oxygen, and a decrease of C02.

External Respiration

External respiration is the exchange of gas between the air in the alveoli and the blood within the
pulmonary capillaries. A normal rate of respiration is 10-20 breaths per minute. In external respiration,
gases diffuse in either direction across the walls of the alveoli. Oxygen diffuses from the air into the
blood and carbon dioxide diffuses out of the blood into the air. Most of the carbon dioxide is carried to
the lungs in plasma as bicarbonate ions (HCO3-). When blood enters the pulmonary capillaries, the
bicarbonate ions and hydrogen ions are converted to carbonic acid (H2CO3) and then back into carbon
dioxide (CO2) and water. This chemical reaction also uses up hydrogen ions. The removal of these ions
gives the blood a more neutral pH, allowing hemoglobin to bind up more oxygen.

Internal Respiration

Internal respiration is the exchanging of gases at the cellular level.

The Passage Way From the Trachea to the Bronchioles

There is a point at the inferior portion of the trachea where it branches into two directions that
form the right and left primary bronchus. This point is called the Carina which is the keel-like cartilage

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