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BIOLOGY SUMMARY

EXCHANGE AND TRANSPORT

MODULE 3

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MODULE 3Exchange & Transport

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TOPIC 1Specialised Exchange Surfaces • Surfaces adapted for easy transport

○ Oxygen, glucose, minerals, proteins, fats, water • Surface area:volume ratio

○ If high = rapid metabolic rate and heat loss ○ If low = slow metabolic rate and heat loss

• Efficient exchange surface ○ Large surface area ○ Thin barrier ○ Maintains steep concentration gradient

• Components of mammalian gas exchange system ○ Airways ○ Lungs ○ Trachea and bronchi ○ Bronchioles

• Tissues of mammalian gas exchange system ○ Cartilage

– Structural support – Prevents collapse

○ Cilia – Waft mucus up airway to back of throat

○ Goblet cells – Produce mucus – Traps particles/pathogens in airways

○ Smooth muscle – Involuntary contraction/relaxation of airways

○ Elastic fibres – Allows repeated contraction/relaxation of

airways without damage • Ventilation in mammals:

Inspiration Expiration

Ext. intercostals Contract Relax

Diaphragm mm.

Contract Relax

Diaphragm Flatten Arches

Ribs Up + outwards Down + inwards

Volume Increase Decrease

• Tidal Volume ○ Approx 500cm3

○ Volume moving in/out of lungs each breath ○ At rest

• Vital Capacity ○ Max. air volume displaced in one breath ○ Approx 5dm3

• Breathing Rate ○ Breaths per minute

• Oxygen Uptake ○ Oxygen volume inhaled per unit time ○ Measured using spirometer ○ Spirometer ○ Chamber with oxygen floating on water ○ Inhalation = chamber sinks ○ Exhalation = chamber rises ○ Carbon dioxide exhaled absorbed by soda lime ○ CO2 exhaled = O2 inhaled

• Bony fish ○ Gas exchange

– Gills absorb oxygen/ release carbon dioxide – Gills are covered by operculum – Gill filaments folded into lamellae

○ Ventilation – Buccal cavities generate waves – Maintains conc. grad. over gills

• Insect ○ Gas exchange

– Open circulation: no blood – Trachea branch out as spiracles – Gas exchange with air by diffusion

○ Ventilation – Large insects do so with body movements

TOPIC 2Transport in Animals • 3 factors affect need for transport system:

○ Size ○ Level of activity ○ SA to volume ratio

• Single circulatory system

○ E.g. in fish ○ Single circuit ○ Blood flow: heart>gills>body>heart

• Double circulatory system ○ In mammals ○ Blood travels twice through heart per circuit ○ Heart > lungs > heart > body > heart ○ Blood pressure raised after being oxygenated ○ Blood flows quickly to tissues ○ Overall higher blood pressure

• Open circulatory system ○ E.g. in insects ○ Blood not enclosed within vessels ○ Moves freely in body ○ Gas exchange through spiracles

• Closed circulatory system ○ In mammals ○ Blood pumped by heart through vessels ○ Blood not normally present in body cavities

• Arteries ○ Carry blood away from heart ○ Thick walls = no diffusion ○ Small lumen = high blood pressure ○ Elastic fibres = withstand high pressure

• Veins ○ Return blood to the heart ○ Carry deoxygenated blood ○ No pulsing and no smooth muscle ○ Walls thinner than in arteries

• Capillaries ○ Link arterioles and venules ○ Only place of diffusion in/out of blood ○ Thin walls to allow diffusion ○ Small lumen ○ Oxygen/nutrients diffuse out ○ White blood cells leak out during infection

• Formation of tissue fluid from plasma ○ Arteriolar end has high hydrostatic pressure (= high water potential)

○ Arteriolar end also has lots of dissolved ions, glucose, amino acids

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