1. GAS EXCHANGE IN HUMANS

2. The Human Respiratory System
The human respiratory system is made up of lungs and a system of air tubes that carry air to and from the lungs.
LUNGS are the gas exchange organs in air-breathing vertebrates and in some other animals.
DIAPHRAGM is a muscle that forms the floor of the chest cavity
PLEURA each lung is covered with a two-layered membrane called pleura.

3. The Human Respiratory System
Air passes through;
The nose Pharynx Larynx Trachea
Bronchi
Bronchial tubes
Bronchioles
Alveoli

6. The Human Respiratory System
THE NOSE:
air enters through nostrils
the spaces in the nose are called nasal passages
hairs stop foreign substances from entering
the wall of the nasal passages are covered with;
Mucous membrane
Cells that have cilia
They both trap bacteria, dust, and particles
moistens air

7. The Human Respiratory System
THE PHARYNX:
from the nasal passages, air travels through the pharynx (throat)
it connects the nasal cavity and oral cavity to larynx
tonsils form a protective barrier at the junction of pharynx and oral cavity

8. The Human Respiratory System
THE LARYNX: (VOICEBOX)
it is mainly made up of cartilage
vocal cords are two pairs of membranes streched across the inside of the larynx
as air is breathed out, the vocal cords vibrate

9. The Human Respiratory System
Epiglottis:
To prevent chocking during swallowing food and liquids are blocked from entering the opening of the larynx by the epiglottis.

10. The Human Respiratory System
TRACHEA:
is made up of smooth muscle, cartilage and mucous membrane
it’s always open by cartilage rings
inside of it is lined with ciliated mucous membrane

11. The Human Respiratory System
BRONCHI:
in the middle of the chest cavity, trachea branches into two bronchi.
they are made up of cartilage and lined with ciliated cells.
when they enter the lungs, they form the bronchial tubes
BRONCHIOLES:
the bronchial tubes divide and subdivide, finally they become a group of tiny tubes called bronchioles

12. The Human Respiratory System
ALVEOLI:
each bronchiole ends in a tiny air chamber that looks like a cluster of grapes
each chamber contains several cup-shaped cavities called alveoli
the walls of the alveoli is only one cell-thick and they are the respiratory surface
they are moist and surrounded by large no. of capillaries
the exchange of O2 and CO2 between air and blood takes place through the capillaries.

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14. Gas Exchange in Humans
Gas exchange in humans can be divided into 4 stages;
*Breathing is the movement of air into and out of the lungs
*External respiration is the exchange of O2 and CO2 between the air and the blood in the lungs
*Internal respiration is the exchange of O2 and CO2 between the blood and the body cells
*O2 and CO2 transport is the movement of gases between the lungs and other body parts

15. DURING INHALATION (INSPIRATION) DURING EXHALATION (EXPIRATION)
The diaphragm muscles contract and pull it down
The diaphragm muscles relax, allowing the diaphragm to return to its domed shape (upward-arched)
The intercostal (rib) muscles contract and pull the rib cage up and out.
The intercostal (rib) muscles relax, allowing the ribs to move downwards under their own weight.
Chest (thoracic) cavity volume increases
Chest (thoracic) cavity volume decreases
Pressure in the cavity decreases as (compared to atmosphere)
Pressure in the cavity increases (as compared to atmosphere)
Air is sucked into the respiratory tract & lungs
Air is forced out through the system.
AN ACTIVE PROCESS
A PASSIVE PROCESS

16. The rate and depth of breathing is increased
Control of Breathing
Breathing is mostly involuntary and it’s controlled by respiratory center in the brain.
When [CO2 ] increases in blood
Chemoreceptors on aorta and some arteries detect changes
Respiratory center in the brain is stimulated
Nerves carry impulses to
The rate and depth of breathing is increased
[CO2 ] is lowered in the blood
Diaphragm and chest muscles

17. Control of Breathing
***CO2 and lactic acid that is formed during heavy exercise increases the acidity of blood and stimulates respiratory center to increase breathing.

18. Control of Breathing

19. External and Internal Breathing
External Respiration is the exchange of O2 and CO2 between the air and the blood in the lungs.
After inhalation, the amount of O2 in the alveoli is higher than in the blood
Then diffuses into blood that is the region where [O2] is lower
So O2 dissolves into moist lining of alveoli
As the blood is pumped from heart, O2 rich blood from lungs is carried to body tissues

20. External and Internal Breathing
Blood that is rich in CO2 from body tissues is returned to lungs
Then diffuses into blood that is the region where [O2]
In the lungs, the amount of CO2 in the blood is higher than the CO2 in the alveoli
CO2 diffuses out of the blood into the alveoli

21. External and Internal Breathing
Internal Respiration is the exchange of O2 and CO2 between the blood and the body cells.
In the capillaries of the body tissues, O2 diffuses from blood the body cells.
CO2 diffuses out of the cells into the blood.
***Each gas diffuses down a concentration gradient, that is each gas diffuses from a high concentration area to a low concentration area.

22. O2 and CO2 Transport Oxygen Transport
98% of oxygen is carried from lungs to body tissues by the hemoglobin in RBCs. (Hemoglobin holds O2 loosely)
Hb O HbO 2
(Hemoglobin) (Oxyhemoglobin)
2. 2% of oxygen is transported by blood plasma as dissolved O2

23. O2 and CO2 Transport
** The amount of oxygen in the surrounding tissues determines whether hemoglobin will combine with oxygen or will release oxygen.
Hemoglobin combines with O2 to form oxyhemoglobin
When blood reaches to body cells, amount of O2 in the surrounding is low
In the lungs there is large amount of O2
Oxyhemoglobin breaks down into oxygen and hemoglobin

24. O2 and CO2 Transport

25. O2 and CO2 Transport

26. O2 and CO2 Transport Carbondioxide Transport
70% of CO2 is transported in blood is carried in blood plasma.
CO H2O H2CO3
Carbonic anhydrase
H2CO3 quickly breaks down into H+ ions and HCO3
H2CO H HCO3-
(is held by (bicarbonate ions
hemoglobin) diffuses into plasma)
forms quickly by the enzyme found in RBCs

27. O2 and CO2 Transport
2. 20% of carbondioxide is transported by RBCs as carboxyhemoglobin.
CO Hb HbCO2 (carboxyhemoglobin)
3. 10% of carbondioxide that diffuses into blood is transported by blood plasma as dissolved CO2.

28. O2 and CO2 Transport @

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