F4 Biology teaching notes Ch 7: 2nd Term NE 1

7.1  The human breathing system (Book 1B, p. 7-3)

Ø  Cells carry out (1) respiration to release energy for cellular activities.

Ø  To ensure the supply of (2) oxygen to cells and the removal of (3) carbon dioxide

from cells, gas exchange (氣體交換) takes place continuously between the cells and the external environment.

Ø  Gas exchange in microorganisms can take place by (4) diffusion

Ø   Organisms with larger size like human need (5) breathing system (呼吸系統) to carry out gas exchange effectively

	(a)	(b)	(c)
Total surface area = height X width X no. of sides X no. of boxes	6	150	750
Total volume   = height X width X length X no. of boxes	1	125	125
Surface-to-volume-ratio  = Surface area / Volume	6	1.2	6

Conclusion: Volume ­ è Surface-to-volume-ratio ¯ è Efficiency of diffusion (6) increases / decreases

Ø  In organisms with larger size like humans,

n a (7) breathing system (呼吸系統) is developed for efficient gas exchange.

n   a (8) transport system (運送系統) is also developed to carry gases between the sites of gas exchange and other body cells.

Ø  The human breathing system consists of: CE-2008-I-A Q.3            

n the (9) respiratory tract (呼吸道) and

n structures that aid breathing.

Structure	Feature	Function
Nostril	With (17) hair	filter larger dust particles from the air
nasal cavity (鼻腔)	Lined with:           èFig 1: mucus-secreting cells and ciliated epithelial cells
	(18) mucus-secreting cells (黏膜分泌細胞)	n   trap dust particles and bacteria n   moisten the incoming air
	ciliated epithelial cells (纖毛上皮細胞)	have (19) cilia (纖毛) to sweep the mucus towards pharynx for being coughed out or swallowed
	capillaries	carry blood to warm up the incoming air
(20)larynx (咽)	Where the respiratory tract and the alimentary canal meet
(21) epiglottis (會咽軟骨)	Covers the opening of larynx during (22) swallowing to prevent choking
Larynx	n   Mainly made of (23) cartilage  èFig 2: Trachea & larynx n  Contains vocal cords (聲帶) which vibrate to produce sound
Trachea	(24) C-shaped cartilages	Support and prevent trachea from being collapsed
	Lined with mucus-secreting cells, ciliated epithelial cells and capillaries	as above
(25) bronchus (bronchi) (支氣管)	circular rings of cartilages	Support and prevent bronchus from being collapsed
	Lined with mucus-secreting cells, ciliated epithelial cells and capillaries	as above
(26) bronchiole (小支氣管)	n   No cartilages n           Larger ones lined with mucus-secreting cells and ciliated epithelial cells
Lung	Mainly composed of bronchioles and air sacs
(27) air sac (氣囊)	numerous	Provides a large respiratory surface (呼吸表面) for efficient gas exchange
	Surrounded by a network of (28) capillaries	To maintain a steep concentration gradient for diffusion of gases
(29) ribs	Makes up the (30) rib cage (肋骨籃) with sternum (胸骨) and vertebral column (脊柱)	Protect the lungs
(31) intercostal muscles	n  Located between each pair of ribs n  Alternate contraction and relaxation	Involved in breathing actions èFig 3: ribs, intercostal muscles & pleural membrane
(32) pleural membrane (胸膜)	n  Located between thoracic cavity and the lungs n  enclose the lungs	Secrete (33) pleural fluid (胸膜液)
(34) pleural cavity (胸膜腔)	n  enclosed by the pleural membranes	Contains pleural fluid which acts as a (35) lubricant to reduce friction during breathing movement
(36) diaphragm	n           A sheet of muscle (fibre?) lying at the bottom of the rib cage	Involved in breathing actions èFig 4: diaphragm

Ø   The path of air flowing through the respiratory tract into the lungs:

Nasal cavity à (37) pharynx à larynx à (39) trachea à bronchus

à bronchiole (in lungs) → (40) air sac (in lungs)