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CHAPTER 11: GAS EXCHANGE IN HUMAN (Important structures for human…
CHAPTER 11: GAS EXCHANGE IN HUMAN
Respiration
Vital for all living organisms
A way to convert chemical (nutrients) into energy for cellular activities.
excretion of waste products
muscle contraction (enable locomotion)
cell division (for growth and development)
transmission of nerve impulses
absorption of nutrients (from digested food) - active transport
maintenance of body temperature (in warm-blooded animals)
synthesis of lipids, hormones, proteins and enzymes
Factors affecting gaseous exchange surface in human
Large alveolar surface area
smaller alveoli = larger surface area
surface area: rounded ends > pointed ends
Thin alveolar walls
maximizing the oxygen and carbon dioxide diffusion across the alveolar walls (surface) - short diffusion distance
Extensive blood supply
efficient journey of:
ensuring oxygen rich blood - away from the lungs
carbon dioxide rich blood - taken to the lungs.
Ventilation with air
enable large diffusion gradient
oxygen concentration: alveoli > capillaries
oxygen moves from alveoli :arrow_right: capillaries
carbon dioxide: capillaries > alveoli
carbon dioxide moves from capillaries :arrow_right: alveoli
Important structures for human respiration
Nostrils
: point of entry
Pharynx
: passageway of air, food and liquid
Trachea
: main airways
having cartilage: supporting while still allowing the elasticity of trachea structure to move and flex during breathing
Bronchi
: branching airways (connecting from trachea)
Lungs
: organ of respiration
Alveolus
: site of gaseous exchange
Diaphragm
: skeletal muscle of respiration
Inhalation:
diaphragm
contracts
diaphragm lowers and flattens
Exhalation:
diaphragm
relaxes
diaphragm curves upwards (normal position)
Intercostal muscle
: moves ribs during respiration
Inhalation:
external intercostal muscle
contracts
internal intercostal muscle
relaxes
Exhalation:
external intercostal muscle
relaxes
internal intercostal muscle
contracts
Pleural membranes & Pleural fluid
: lines lungs and chest cavity
Human Breathing Mechanism
Inhalation
External intercostal muscles
contract
,
internal intercostal muscles
relax
:arrow_right:
rib cage
moves
upwards and outwards
Diaphragm muscles
contracts
:arrow_right:
diaphragm
lowers and flattens
2 actions above :arrow_right:
volume of thoracic cavity
increases
:arrow_right:
pressure of thoracic cavity
decreases
Higher
atmosphere pressure
+
lower
thoracic cavity pressure
= air forces
into
the lungs
Exhalation
External intercostal muscles
relaxes
,
internal intercostal muscles
contracts
:arrow_right:
rib cage
moves
downwards and inwards
Diaphragm muscles
relaxes
:arrow_right:
diaphragm
curves upwards
(return to normal position)
2 actions above :arrow_right:
volume of thoracic cavity
decreases
:arrow_right:
pressure of thoracic cavity
increases
Lower
atmosphere pressure
+
higher
thoracic cavity pressure
= air forces
out of
the lungs
Inspired air VS Expired air
Inspired air:
oxygen - 21%
carbon dioxide - 0.04%
nitrogen - 78%
water vapour - very variable
Expired air:
oxygen - 16%
carbon dioxide - 4%
nitrogen - 78%
water vapour - always high
Keeping Clean & Healthy
Goblet cells
: makes mucus (read mucus)
Mucus
: trap dust particles and pathogens
contain lysosomes to destroy pathogen from invading body defense system (read Chap. 10 Disease and Immunity).
Ciliated cells
: microscopic hairs
sweeps mucus (with trapped pollutants) into throat
White Blood Cells
: patrolling on the surface walls of alveoli
take in and digest pathogen or foreign materials
Physical Exercises Affecting Breathing Rate: How?
Faster muscle cells respire = more carbon dioxide generated
Carbon dioxide dissolves in blood plasma :arrow_right: forming carbonic acid (weak acid) :arrow_right: lowers blood pH
Brain detects pH change :arrow_right: impulses along nerves to lungs :arrow_right: faster breathing (muscles contract faster and harder)
Faster breathing rate = faster oxygen delivery + faster carbon dioxide excretion