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Topic : Plant Structure & Reproduction

Taibah University
‫جامعة طيبة‬
The kingdom of Saudi Arabia
‫المملكة العربية السعودية‬
1443 – 2021
2021 – 1443
Gas Exchange and Circulation
Student: Farah Hussain Eissa
Section: C1B
ID: 4157327
Supervised by: Dr. May waedo
Page number
Mechanisms of Gas Exchange
The human Respiratory System
Transport of Gases in the human body
Circulatory System
The human Cardiovascular System and heart
Structure and Function of blood
Animals and Human are complex multicellular organisms that Require a
mechanism for transporting nutrients throughout their Bodies and removing wastes.
The human circulatory system has a complex network of blood Vessels that reach
all parts of the body.
This extensive network supplies the cells, tissues, and organs with Oxygen and
nutrients, and remove carbon dioxide and waste Compound.
The medium for transport of gases and other molecules is the Blood, which
continually circulates Through the system.
Pressure differences within the system cause the movement of the Blood and
created by the pumping of the heart.
Gas exchange between tissues and the blood is an essential Function of the
circulatory system, in humans, other mammals, And birds, blood absorbs oxygen
and releases carbon dioxide in The lungs.
Thus, the circulatory and respiratory system, whose function is to Obtain oxygen
and discharge carbon dioxide, work in tandem.
I wrote this research for gaining more information about “Gas Exchange and
Circulation”, to confirm my understanding of the Information, and to improve
research writing skills.
o Mechanisms of Gas Exchange
• Gas exchange in human involves breathing transport of gases, And exchange
with body cells
There are three phases of gas exchange in human and other animals with lungs:
1- Breathing: Oxygen 𝑂2 diffuses across the cells lining the lungs and into surrounding blood
Vessels. At the same time, carbon dioxide 𝐶𝑂2 diffuses from the blood into the lungs. As
You exhale, 𝐶𝑂2 leaves your body.
2- Transporting of gases and circulatory system: the 𝑂2 that diffused into the blood attaches to
Hemoglobin in red blood cells, the vessels transporting 𝑂2 – rich blood from lungs to the
Capillaries in the body’s tissues. 𝐶𝑂2 is also transported in blood, from the tissues to back
To the lungs, carried in the blue vessels shown here.
3- Exchanges of gases with body cells: the cells take up the 𝑂2 from the blood release 𝐶𝑂2 to
The blood. 𝑂2 function in cellular respiration in the mitochondria as the final electron
Acceptor in the stepwise breakdown of fuel molecules. 𝐻2 𝑂 and 𝐶𝑂2 are waste products,
And ATP is produced that will power cellular work.
•Animals exchange 𝑂2 and
𝐶𝑂2 across moist body
The respiratory surfaces are the part of an animal’s body where gas exchange with environment
Occurs, the respiratory surfaces are made up of living cells, thus plasma membranes must be wet
To function properly. thus, respiratory surfaces are always moist.
Gas exchange takes place by diffusion. The surface area of the respiratory surface must be
Large enough to take up sufficient 𝑂2 for every cell in the body. Usually, a single layer allows 𝑂2 to
Diffuse rapidly into the circulatory system or directly into body tissues and allows 𝐶𝑂2 to Diffuse
The four types of respiratory organs, are:
1- Skin: The earthworms exchange the 𝐶𝑂2 and 𝑂2 across moist body surfaces.
2- Gills: is a respiratory organ, found in many aquatic organisms that extracts dissolved oxygen
From water and excretes carbon dioxide. Gills increase surfaces area for gas exchange.
The outer body surfaces
3- Tracheal system: tracheal system uses tiny branching tubes. In which the air is piped to cells.
4- Lungs: the inner surfaces of the lungs are extensively subdivided, forming a large respiratory
Surface, gases are carried between the lungs and the body cells by the circulatory system.
Tetrapods are dividing into three main sections:
– Amphibians uses small lungs and their body surfaces.
– Non – bird reptiles have simpler lungs.
– Birds and mammals have more complex lungs.
o The human respiratory system
• In mammals, branching tubes convey air to lungs located in the chest Cavity
In mammals, the lungs are in the chest, or thoracic cavity, and protected by the supportive the
Cage. The thoracic cavity is separated from the abdominal cavity by a sheet of muscle called the
Air enters your respiratory system through the nostrils. It’s filtered by hairs and warmed,
Humidified, and sampled for odors as it flows through a maze of space in the nasal cavity. Also, air
Can enters through the mouth, but mouth breathing doesn’t allow the air to processed by the nasal
From the nasal cavity or mouth, air pass to the pharynx, where the paths and for air and food
The rest of the time, the air passage in the pharynx is open for breathing.
The larynx is often called the voice box. When you exhale the outgoing air rushes by pair of vocal
Cords in the larynx, that you can produce sound by voluntarily tensing muscles that stretch the
Cords, so they vibrate.
From the larynx, air passes into the trachea. Rings of cartilage reinforce the walls of the larynx and
Trachea, keeping this part of airway open. The trachea forks into two bronchi, the bronchus
Branches repeatedly into finer and finer tubes called bronchioles.
Finally, to the alveoli where gas exchange occurs. When air reaches the alveoli after inhalation.
Some of the 𝑂2 dissolves in the film covering the epithelium of the alveoli. From here it diffuses
Into the blood in a nearby capillary. It enters a red blood cell and combines with the hemoglobin
Therein. At the same time, some of the 𝑂2 diffuses blood into the alveoli from which it can be
• Negative pressure breathing ventilates your lungs
Breathing is ventilation of the lungs through alternating inhalation and exhalation. The continual
Movement of air as you inhale, and exhale maintains high 𝑂2 and low 𝐶𝑂2 concentration at the
Respiratory surface. In human and other mammals, ventilation occurs by negative pressure
Breathing, a system in which air is pulled into the lungs.
– How inhalation work?
1- The chest expands.
2- The diaphragm moves downward.
3- The pressure around lungs decreases.
4- Air is drawn into the respiratory tract.
– How exhalation work?
1- The chest contracts.
2- The diaphragm moves upward.
3- The pressure around the lungs increases.
4- Air is forced out of the respiratory tract.
o Transport of gases in human body
• Blood transports respiratory gases
How does the oxygen get out from your lungs to all the other tissues in your body? How does
Carbon dioxide travel from the tissues to your lungs?
It’s start with heart. One side of the heart (The right side) handles oxygen – poor blood, the other
Side (Left side) handles oxygen rich – blood. Oxygen – poor blood return to the heart from
Capillaries in body tissues. The heart pumps this blood to the alveolar capillaries in the lungs.
Gases are exchanged between air in the alveoli and blood in the capillaries. Blood that has lost
𝐶𝑂2 and gained 𝑂2 returns to the heart and is then pumped out to body tissues.
• Hemoglobin carries 𝑂2 , helps transport 𝐶𝑂2 , and buffers blood
1- Hemoglobin in red blood cells carries 𝑂2 (up to 4 𝑂2 molecules) and helps transport 𝐶𝑂2,
and buffer the blood.
2- Hemoglobin loading and unloading of 𝑂2.
3- Hemoglobin carries 𝑂2, helps transport 𝐶𝑂2, and buffers blood.
– Most 𝐶𝑂2 in the blood is transported as bicarbonate ions.
o Circulatory system
• Circulatory system facilitate exchange with all body tissues
Gastrovascular cavities function in both digestion and transport. In open circulatory system, a
Heart pumps fluid through open-ended vessels to bathe tissue cells directly. In closed circulatory
System, a heart pumps blood, which travels through arteries to capillaries to veins and back to the
o The human cardiovascular system and heart
• The human cardiovascular system illustrates the double circulation of mammals
– The right side:
The right ventricle pumps oxygen – poor blood to the lung via the pulmonary arteries. As blood
Flows through Capillaries in the lungs, it takes up 𝑂2 and unload 𝐶𝑂2. Oxygen – rich blood back
Through the pulmonary veins to the left atrium. Next, the oxygen – rich blood flows from the left
Atrium into the left ventricle.
– The left side:
The left side ventricle pumps oxygen – rich blood into the aorta. The first branches from the aorta
Are the coronary arteries, which supply blood to the heart muscle itself. Next there are large
Branches leading to the head, chest, and arms, and the abdominal regions and legs.
The capillaries rejoin as venules, which lead to the veins. Oxygen – poor blood from the upper part
Of the body is channeled into a large vein called the superior vena cava, and from the lower part
The body it flows through the inferior vena cave. The two flows from the right atrium into the right
Remember that the path of any single blood cell is always heart to lung capillaries to heart to body
Tissue capillaries and back to heart. In one systemic circuit, a blood cell may travel to the brain; in
The next, it may travel to the to the legs. A red blood cell never travels from the brain to legs
Without first returning to the heart and being pumped to the lungs to recharged with oxygen.
The heart contracts and relax rhythmically
During diastole of the cardiac cycle, blood flows from the veins into the heart chambers; during
Systole, contractions of the atria push blood into the ventricles, and then stronger contraction of
The ventricles propel blood into the large arteries. Cardiac output is the amount of blood per
Minute pumped by a ventricle. Heart valves prevent the backflow of blood.
o Structure and function of blood

The liquid component of blood can be isolated by spinning a tube of whole blood at high speeds in
A centrifuge. The denser cells and platelets move to the bottom of the tube, forming red and white
Layers, while the plasma remains at the top, forming a yellow layer.
â–ª The plasma is about 90% water, with the remining 10% made up of ions, proteins, nutrients,
Wastes, and dissolved gases. The ions, proteins, and other molecules found in plasma are
Important for maintaining blood PH and osmotic balance, with albumen (the main protein in
Human plasma) playing a particularly important role.
– Red Blood cells, white blood cells, and platelets
Cell type
Erythrocytes (Red blood cells)
5 – 6 million
Transport of oxygen and carbon
Leukocytes (White blood cells).
5000 – 10000
Defense and immunity
â–ª Basophile
â–ª Eosinophil
â–ª Neutrophil
â–ª Monocyte
â–ª Lymphocyte
250,000 – 400,000
Blood clotting
Gas exchange, the interchange of 𝑂2 and 𝐶𝑂2 between an organism and its environment,
provides 𝑂2for cellular respiration and removes its waste product 𝐶𝑂2 .
Respiratory surfaces must be thin and moist for diffusion of 𝑂2 and 𝐶𝑂2 to occur. Some
Animals use their entire skin as gas exchange organ. In most animals, gills, a tracheal
System, or lungs provide large respiratory surfaces for gas exchange.
Inhaled air passes through the pharynx and larynx into the trachea, bronchi, and
Bronchioles to the alveoli. Mucus and cilia in the respiratory passage protect the lungs.
The heart pumps oxygen – poor blood to the lungs, where it picks up 𝑂2 and drops off 𝐶𝑂2.
Oxygen – rich blood returns to the heart and pumped to body cells, where it drops off 𝑂2and
Picks up 𝐶𝑂2 .
The mammalian heart has two thin – walled atria and two thick – walled ventricles. The right
Side of the heart receives and pumped oxygen – poor blood; the left side of the heart
Receives oxygen – rich blood from the lungs and pumps it to all other organs.
During diastole of the cardiac cycle, blood flows from veins into the heart chambers; during
Systole contraction of the atria push blood into the ventricles, and then stronger contraction
Of the ventricles propel blood into the large arteries. Cardiac output is the amount of blood
Per minute pumped by ventricles. Heart valves prevent the back flow of blood.
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