Page 206 - 84 human physiolofy part-1

Chapter 11

plate at the division point. We are now at the Bronchial Tree. It is named so because it has a series of
respiratory tubes that branch off into smaller and smaller tubes as they run throughout the lungs.

Right and Left Lungs

The Right Primary Bronchus is the first portion we come to, it then branches off into the Lobar
(secondary) Bronchi, Segmental (tertiary) Bronchi, then to the Bronchioles which have little
cartilage and are lined by simple cuboidal epithelium (See fig. 1). The bronchi are lined by
pseudostratified columnar epithelium. Objects will likely lodge here at the junction of the Carina and
the Right Primary Bronchus because of the vertical structure. Items have a tendency to fall in it, where
as the Left Primary Bronchus has more of a curve to it which would make it hard to have things lodge
there.

The Left Primary Bronchus has the same setup as the right with the lobar, semental bronchi and
the bronchioles.

The lungs are attached to the heart and trachea through structures that are called the roots of the
lungs. The roots of the lungs are the bronchi, pulmonary vessels, bronchial vessels, lymphatic vessels,
and nerves. These structures enter and leave at the hilus of the lung which is "the depression in the
medial surface of a lung that forms the opening through which the bronchus, blood vessels, and nerves
pass" (medlineplus.gov).

There are a number of terminal bronchioles connected to respiratory bronchioles which then
advance into the alveolar ducts that then become alveolar sacs. Each bronchiole terminates in an
elongated space enclosed by many air sacs called alveoli which are surrounded by blood capillaries.
Present there as well, are Alveolar Macrophages, they ingest any microbes that reach the alveoli. The
Pulmonary Alveoli are microscopic, which means they can only be seen through a microscope,
membranous air sacs within the lungs. They are units of respiration and the site of gas exchange
between the respiratory and circulatory systems.

Cellular Respiration

First the oxygen must diffuse from the alveolus into the capillaries. It is able to do this because the
capillaries are permeable to oxygen. After it is in the capillary, about 5% will be dissolved in the blood
plasma. The other oxygen will bind to red blood cells. The red blood cells contain hemoglobin that
carries oxygen. Blood with hemoglobin is able to transport 26 times more oxygen than plasma without
hemoglobin. Our bodies would have to work much harder pumping more blood to supply our cells with
oxygen without the help of hemoglobin. Once it diffuses by osmosis it combines with the hemoglobin
to form oxyhemoglobin.

Now the blood carrying oxygen is pumped through the heart to the rest of the body. Oxygen will
travel in the blood into arteries, arterioles, and eventually capillaries where it will be very close to body
cells. Now with different conditions in temperature and pH (warmer and more acidic than in the lungs),
and with pressure being exerted on the cells, the hemoglobin will give up the oxygen where it will
diffuse to the cells to be used for cellular respiration, also called aerobic respiration. Cellular
respiration is the process of moving energy from one chemical form (glucose) into another (ATP),
since all cells use ATP for all metabolic reactions.

206 | Human Physiology