45 terms

Respiratory 4

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lobar bronchi names: L, R lungs
Each lobe of the right and left lungs receives its own secondary or lobar bronchus.
The lobar bronchi have the same names as the lobes;
superior, middle and inferior on the right,
and superior and inferior on the left.
lobal bronchi division
The secondary bronchi divide into 8-10 tertiary or segmental bronchi and
each segment of the lung that is supplied by a tertiary or segmental bronchus is called a bronchopulmonary segment.
bronchopulmonary segment
Each bronchopulmonary segment is surrounded by CT and receives its own branch of the pulmonary artery and pulmonary vein.
bronchopulmonary segment clinical
The bronchopulmonary segments have clinical significance.
Because each has its own blood supply and tertiary bronchus, and
is separated from the other segments by CT,
certain diseases (including lung cancer) may affect and be confined to a particular bronchopulmonary segment.
This means that it is possible to surgically remove a diseased bronchopulmonary segment without disrupting the rest of the lung.
bronchopulmonary segment
(including lung cancer
This means that it is possible to surgically remove a diseased bronchopulmonary segment without disrupting the rest of the lung.
lung lobule n its components
The lung lobules are the smallest division of the lungs that are visible to the naked eye.
Each lobule is served by a bronchiole and its branches.
Respiratory bronchioles
Alveolar ducts:
Alveolar sacs
Alveolar ducts:
- Lined with simple squamous.
Alveolar sacs
Comprised of several alveoli
black lines on lung
The black lines separating the lobules in the photograph are because the CT separating the lobules soaks up carbon dust (cigarette smoke, air pollution, etc.) and remains trapped.
Bronchi and Lung Lobules
The picture above shows the progressive subdivision of the respiratory passageways until they end in a lung lobule.
Notice the respiratory bronchioles bearing alveoli, the alveolar duct, alveolar sac and the individual alveoli.
alveolus surrounded
Each alveolus is surrounded by a dense capillary network, and has elastic fibers on the outside like rubber bands around a balloon.
The alveoli are surround by fine elastic fibers.
elatic fibers fn
These fibers are critically important for the lungs to function normally in respiration.
As we will see, inhaled air causes the alveolar wall to stretch just like blowing up a balloon.
The elastic fibers create the recoil of the alveoli when the diaphragm relaxes which results in passive exhalation.
When we exhale, it is the elastic recoil that causes the carbon dioxide-filled air to move out of the lungs—
like letting the air out of an inflated balloon.
alveoli elastic fibers: how damage, result
Smoking and certain fumes from chemicals can destroy the elastic fibers making expiration in particular difficult.
This will lead to difficulty in keeping the blood pH stable and will put a strain on the kidneys.
The lungs receive blood from: list
The lungs receive blood from two circulations:
the pulmonary, and
the bronchial.
the pulmonary
the bronchial.
Deoxygenated venous blood returning from the systemic circuit is pumped to the lungs via the pulmonary arteries.
The pulmonary arteries subdivide and branch and follow the bronchi.
Ultimately, pulmonary capillary networks are formed which surround each alveolus and contribute to the respiratory membrane to be discussed later.
After being oxygenated, the blood is returned to the left side of the heart via the pulmonary veins which follow the bronchial tree back to the hilum.
The large volume of blood in the pulmonary circuit is under extremely low pressure.
The small volume of arterial blood in the bronchial arteries is under higher pressure similar to the rest of the systemic circuit.
This blood supplies the pulmonary structures (except the aveoli) with the blood necessary to keep them alive and healthy, but plays no role in oxygenation.
structure of alveolus: list
type I alveolar cells
type Il alveolar cells
dust cells
type I alveolar cells : where
The walls of the alveoli are made up primarily of a simple squamous epithelium.
The cells that make up this thin sheet are mainly type I cells (also called type I alveolar cells or pneumocytes).
These cells are a component of the respiratory membrane along with the capillaries we discussed previously.
type I alveolar cells : fn
Their thin nature facilitates rapid exchange of blood gases between the alveolar lumen and the blood.
type II alveolar cells : where
A second type of cell called type II cells (A.K.A. type II alveolar cell or septal cell) are found scattered throughout the alveolar wall.
type II alveolar cells : appearance
These cells are large and frothy in appearance.
type II alveolar cells : fn
They synthesize and secrete a lipid fluid called surfactant which lowers surface tension with in the walls of the alveoli so they don't stick together.
dust cells
Also scattered about are the alveolar macrophages, appropriately called dust cells.
These cell don't make up the epithelium but they can wander throughout the alveolar walls and air spaces.
dust cells fn
Their job is to phagocytize any debris or pathogens that make it all the way to the alveoli.
They are responsible for keeping the respiratory surface clean and clear of gunk which would hinder diffusion of gases.
surfactant def
What is surfactant?
Surfactant is a fluid secretion by type II cells that is comprised predominately of phospholipids and lipoproteins.
surfactant fn
This substance lowers surface tension of the alveolar fluid which is mainly water.
cohesion
Surface tension increases at the air-water interface.
Water molecules want to stick together.
This is property is known as water cohesion and is
critical for living organisms from single cells to redwood trees.
alveoli w/o surfactant
However, the water-based alveolar fluid would cause the walls of the alveoli to stick together and collapse thereby preventing diffusion of gases.
alveoli w surfactant
Because surfactant is a lipid and oil and water don't mix,
this keeps the water molecules from sticking together and therefore
reduces the force that would collapse the alveoli.
pneumocyte type ll n surfactant
This is an electron micrograph of a type II cell.
The large, clear vacuoles (V) contain surfactant.
Numerous mitochondria (M) can be seen between the vacuoles (V).
The arrow is pointing to the secretory surface of the cell where surfactant is released.
why premature babies died
Prior to 1970s, many premature babies died because they could not breathe.
The lung tissue is glandular and the alveoli are collapsed.
Fetuses do undergo ventilation of amniotic fluid.
how was surfactant used
After the discovery of surfactant, the lives of many pre-term babies were saved.
Surfactant was injected into the amniotic fluid if a woman's premature labor could not be stopped.
physiology of good surfactant
The fetus would "inhale" the surfactant in the amniotic fluid.
When the fetus was delivered, it could successfully be ventilated because the surfactant allowed the alveoli to open.
adults n surfactant
In adults, every time we sigh, cough, sneeze, yawn or take a deep breath, surfactant is released from type II pneumocytes.
clinical surfactant general
Prior to 1970s, many premature babies died because they could not breathe.
The lung tissue is glandular and the alveoli are collapsed.
Fetuses do undergo ventilation of amniotic fluid.

After the discovery of surfactant, the lives of many pre-term babies were saved.
Surfactant was injected into the amniotic fluid if a woman's premature labor could not be stopped.

The fetus would "inhale" the surfactant in the amniotic fluid.
When the fetus was delivered, it could successfully be ventilated because the surfactant allowed the alveoli to open.

In adults, every time we sigh, cough, sneeze, yawn or take a deep breath, surfactant is released from type II pneumocytes.
parameter that influences efficiency of gaseous exchange: list
thickness of alveolar wall
alveolar surface area
wall of alveolus
Recall that the "wall" of an alveolus consists mainly of type I pneumocytes forming a simple squamous epithelium,
with a few type II cells which secrete surfactant.
repiratory membrane n diffusion
The respiratory membrane consists of the fused basement membranes of the alveolar cells and
the capillary endothelial cells making an extremely thin region to facilitate gaseous exchange via diffusion
between the alveolar air space and the blood.
respiratory membrane: normal thickness
In healthy lungs, the respiratory membrane is only between 0.5-1.0 micrometers thick making gas exchange very efficient.
pneumonia
In the case of pneumonia, fluid accumulates in the alveoli—
the lungs essentially become waterlogged or edematous.
Under these conditions, the respiratory membrane thickens and
diffusion of gases is reduced which means that
the body tissues begin to suffer from hypoxia (oxygen deprivation).
Alveolar surface area
Alveolar surface area is another .
The greater the surface area of the respiratory membrane,
the more gas can diffuse across it in a given period of time.
total gas exchange surface area of normal male
If the lungs of a normal healthy male were spread out flat,
the total gas exchange surface area is about 90 m2!
This is about 40X the surface area of the skin.
emphysema
However, in pulmonary diseases like emphysema,
the walls of adjacent alveoli break down and the alveoli coalesce forming large chambers.
This reduces surface area for gaseous exchange and people suffering from emphysema get "out of breath" easily due to oxygen deprivation.
alveolar wall and its components
Recall that all epithelia rest on a basement membrane.
The alveolar wall is comprised of two types of epithelia,
the alveolar epithelium with its basement membrane, and
the capillary endothelium (also simple squamous epithelium) and
its basement membrane.
alveoli wall
However, in alveoli the two adjacent basement membranes have fused to make an extremely thin (1/2 of a micron) surface separating air on one side and blood on the other.
.
alveoli wall fn
Gas exchange occurs easily and rapidly via simple diffusion across this thing respiratory membrane—oxygen passes from the alveolus into the blood, and carbon dioxide leaves the blood to enter the alveolus and is ultimately eliminated from the body when we exhale