Download Mr. Ali H . Alhamdany Human Respiratory System

Lec.7
Human Respiratory System
The respiratory system is a biological system that is responsible for gas
exchange. It involves an interconnected group of organs and tissues that help
you breathe. The main parts of this system are the airways, the lungs and linked
blood vessels, and the muscles that enable breathing
 Airways
The primary job of the human respiratory system is gas exchange - to bring in
fresh oxygen and expel carbon dioxide. The airways are pipes that carry oxygenrich air to your lungs and carbon dioxide (a waste gas), out of your lungs.
The airways include your:





Nose and linked air passages called nasal cavities
Mouth
Larynx or voice box
Trachea or windpipe
Tubes called bronchial tubes or bronchi, and their branches
Air initially enters the respiratory system through the nasal and oral cavities.
Both of these passageways meet at the same place- the pharynx.
The pharynx then leads to the larynx,
and down to the trachea.
The trachea then branches in two
different paths, known as the left and
right primary bronchi.
These small tubes carry the fresh
oxygen deep into the lungs.
1
Mr. Ali H . Alhamdany
Msc . physiology
The respiratory tract It is divided into two sections:
Upper Respiratory Tract and the Lower Respiratory Tract. Included in the
upper respiratory tract are the Nostrils, Nasal Cavities, Pharynx, Epiglottis, and
the Larynx. The lower respiratory tract consists of the Trachea, Bronchi,
Bronchioles, and the Lungs.
 Functions
 Function of the respiratory system – supplies the body with oxygen and
disposes of carbon dioxide
 Respiration – a collective term for the following
processes:
o


o


o


o


Pulmonary ventilation
Movement of air into the lungs (inspiration)
Movement of air out of the lungs (expiration)
External respiration
Movement of oxygen from the lungs to the blood
Movement of carbon dioxide from the blood to the
lungs
Transport of respiratory gases
Transport of oxygen from the lungs to the tissues
Transport of carbon dioxide from the tissues to the
lungs
Internal respiration
Movement of oxygen from blood to the tissue cells
Movement of carbon dioxide from tissue cells to blood
In addition to these main processes, the respiratory system serves for:
 Regulation of Blood pH, which occurs in coordination with the kidneys,
and as a 'DEFENSE AGAINST MICROBES
 Control of body temperature due to loss of evaporate during expiration
2
Mr. Ali H . Alhamdany
Msc . physiology
 Upper Respiratory Tract
 Nose
 Functions





Provides and airway for respiration
Moistens and warms entering air
Filters and cleans inspired air
Resonating chamber for speech
Detects odors in the airstream
 Pharynx
 Three regions of the pharynx



Nasopharynx – air passage (pseudostratified columnar epithelium)
Oropharynx – passageway for air, food, and drink (stratified squamous
epithelium)
Laryngopharynx – passageway for air, food, and drink (stratified squamous
epithelium)
Air enters through the nostrils of the nose and is partially filtered by the nose
hairs, then flows into the nasal cavity. The nasal cavity is lined with epithelial
tissue, containing blood vessels, which help warm the air; and secrete mucous,
which further filters the air. The endothelial lining of the nasal cavity also
contains tiny hair like projections, called cilia.
The cilia serve to transport dust and other foreign particles, trapped in mucous,
to the back of the nasal cavity and to the pharynx. There the mucus is either
coughed out, or swallowed and digested by powerful stomach acids. After
passing through the nasal cavity, the air flows down the pharynx to the larynx.
 Larynx (voice box)
The larynx ,colloquially known as the voice box, is an organ in our neck
involved in protection of the trachea and sound production , The larynx contains
two important structures: the epiglottis and the vocal cords.
3
Mr. Ali H . Alhamdany
Msc . physiology
 Functions



Keeps food and drink out of the airway
Sound production
Acts as a sphincter during abdominal straining (ex. During defecation and heavy
lifting)
 Selected anatomical features








Nine c-rings of hyaline cartilage form the framework of the larynx
Muscular walls aid in voice production and the swallowing reflex
Glottis – the superior opening of the larynx
Epiglottis – prevents food and drink from entering airway when swallowing
False vocal cords – aid in closing the glottis when swallowing
True vocal cords – produce sound when air passes between them
The shorter and thinner these membranes are, the faster air moves over them –
produces high pitched sounds
The longer and thicker these membranes are, the slower air moves over them –
produces low pitched sounds
 Lower Respiratory Tract
Lower Respiratory Tract consists of the trachea, bronchioles and lungs
(including alveoli)
 Trachea
which is also known as the windpipe. The trachea divides into two main bronchi,
and one bronchi each enters one of the pair of lungs
 Functions


Air passageway
Cleans, warms, and moistens incoming air
 Selected anatomical features

Rings of hyaline cartilage – reinforce the trachea and keep it from collapsing
when you inhale
4
Mr. Ali H . Alhamdany
Msc . physiology
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 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.
 Bronchi
 Function

Solely an air passageway
 Selected anatomical features




Left and right primary bronchi branch off from trachea
Once the left and right primary bronchi enter the lungs they are subdivided into
smaller tubes:
Alveolar sacs are clusters of alveoli
Diagram of the lungs
Alveoli are the site of gas exchange
 Lungs

Right and left lung
Left



Divided into 2 lobes
Smaller than the right lung
Cardiac notch accommodates the
heart
Right





Divided into 3 lobes
Each lobe is separated by
connective tissue and has its own
arteries and veins
Allows for compartmentalization, esp. when portions of the lungs are diseased.
Serous membranes cover the entire surface of the lungs and produce pleural
fluid
Pleural fluid enables the lungs to expand and contract with minimal friction
5
Mr. Ali H . Alhamdany
Msc . physiology
 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.
 Peripheral control and Gas Transport

Oxygen – most bound to hemoglobin of red blood
cells; small amount dissolved in blood plasma

CO2 is converted to HCO3; most CO2 produced at the
tissue cells is carried to lungs in the form of HCO3
Homeostasis and Gas Exchange
Carbon dioxide Transported in three forms
o Carbonic acid – 90% of carbon dioxide reacts with water to form carbonic acid



CO2 & H2O form carbonic acid (H2CO3)
changes to H CO3 & H+ ions
result is H+ ions are buffered by plasma proteins
o Carboamino compounds – 5% binds to plasma proteins and hemoglobin
o Dissolved gas – 5% carried in the blood as dissolved gas
Breathing and Lung Mechanics
Two phases of pulmonary ventilation
 Inspiration, or inhalation
a very active process that requires input of energy , Air flows into the lungs
when the thoracic pressure falls below atmospheric pressure.
6
Mr. Ali H . Alhamdany
Msc . physiology




The diaphragm moves downward and flattens, when stimulated by phrenic
nerves.
External (inspiratory) intercostals muscles and thoracic muscles can be
stimulated to contract and expand the thoracic cavity
Only in the alveoli does actual gas exchange takes place. There are some 300
million alveoli in two adult lungs. These provide a surface area of some 160 m2
Upon inhalation, alveoli, the tiny sacs which are the basic functional component
of the lungs. The alveolar walls are extremely thin (approx. 0.2 micrometres).
These walls are composed of a single layer of epithelial cells (type I and type II
epithelial cells) close to the pulmonary capillaries which are composed of a
single layer of endothelial cells. The close proximity of these two cell types
allows permeability to gases and, hence
 Expiration, or exhalation

a passive process that takes
advantage of the recoil properties of
elastic fibers

Air is forced out of the lungs when
the thoracic pressure rises above
atmospheric pressure.

The diaphragm
muscles relax.

The elasticity of the lungs and the thoracic cage allows them to return to their
normal size and shape.
To exhale more than usual, internal (expiratory) intercostals muscles and other
muscles can be stimulated.

and
expiratory
 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 12-25
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.
7
Mr. Ali H . Alhamdany
Msc . physiology
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. De-oxygenated blood "blue blood" coming
from the pulmonary arteries, generally has an oxygen partial pressure (pp) of 40
mmHg and CO2 pp of 45 mmHg.
Oxygenated blood leaving the lungs via the pulmonary veins has a O2 pp of 100
mmHg and CO2 pp of 40 mmHg. It should be noted that alveolar O2 pp is 105
mmHg, and not 100 mmHg. The reason why pulmonary venous return blood has
a lower than expected O2 pp can be explained by "Ventilation Perfusion
Mismatch".
 Internal Respiration
Internal respiration is the exchanging of gases at the cellular level.
 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.
8
Mr. Ali H . Alhamdany
Msc . physiology