7.1 Specialised exchange surfaces Flashcards

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1
Q

Why do amoeba not require any specialised exchange surface?

A

all oxygen needed and waste CO2 produced can be exchanged with external environment by diffusion through cell surface
- distances substances have to travel are very very small

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2
Q

2 main reasons why diffusion alone is enough to supply the needs of single celled organisms

A
  1. metabolic activity of a single-celled organism is usually low, so O2 demands and CO2 production of cell are relatively low
  2. SA:V ratio of organism is large
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3
Q

Why is Surface area to volume ratio important?

A

As organisms get larger, they can be made up of millions/ billions of cells, forming tissues, organs and organ systems
–> metabolic activity is much higher ( more oxygen required and more CO2 produced)
–> distance between cells where oxygen is needed is too far for effective diffusion to occur
–> larger organism= smaller SA:V ratio (gases cannot be exchanged fast enough or in large enough amounts for organisms to survive

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4
Q

What makes an efficient exchange surface?

A
  1. Increased surface area - provides area needed for exchange * overcomes limitations of SA:V ratio e.g. root hair cells & villi
  2. Thin layers - diffusion distance is short, meaning it is fast and efficient
  3. Good blood supply - the steeper the conc grad, the faster diffusion occurs so good blood supply ensures substances are constantly delivered and removed. This maintains conc gradient.
  4. Ventilation to maintain diffusion gradient - gases: a ventilation system helps maintain concentration gradient and makes the process more efficient
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5
Q

Human Gaseous exchange system

A

mammals have a small SA:V ratio & very large volume of cells & high metabolic rate

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6
Q

Respiratory system features: Nasal cavity

A
  • large surface area with a good blood supply (warms air to body temp)
  • hairy lining, which secretes mucus to trap dust and bacteria (protecting delicate lung tissue from irritation and infection)
  • moist surfaces, which increases the humidity of incoming air, reducing evaporation from exchange surfaces
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7
Q

Respiratory system features: Trachea

A

main airway, a wide tube supported by incomplete rings of strong flexible cartilage (stops trachea from collapsing)
–> Rings are incomplete to allow it to bend when food is swallowed down oesophagus behind the trachea

Lined with ciliated epithelium & goblet cells
–> prevents dust and bacteria from entering the lungs

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8
Q

Respiratory system features: Bronchus

A

Extensions of the trachea that split into two for the left and right lung
–> very similar structure to trachea but smaller

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9
Q

Respiratory system features: Bronchioles

A

divisions of bronchus and have no cartilage, only smooth muscle (allows contractions for constriction/ relax and dilate)
–> lined with a thin layer of flattened epithelium facilitating some gas exchange

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10
Q

Respiratory system features: Alveoli

A

tiny air sacs (main gas exchange surface)
–> diameter of 200-300 micrometers and are made up of a thin layer of flattened epithelial cells, along with some collagen and elastic fibres
–> The elastic tissue allows alveoli to stretch as air is drawn in (as they return, this helps squeeze air out, elastic recoil)

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11
Q

Respiratory system features: Alveoli adaptions

A
  1. Large surface area (300-500 million alveoli per adult lung)
  2. Thin layers - both alveoli and capillaries are only a single epithelial cell thick so diffusion distance is very short
  3. Good blood supply- 280 million capillaries maintain steep concentration gradient
  4. Good ventilation - breathing moves air in and out, helps maintain steep diffusion gradient
  5. Inner surface of alveoli is covered in a thin solution of water, salts and lung surfactant - allows alveoli to remain inflated & reduces water loss
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12
Q

Ventilation

A

pressure changes in thoracic cavity brought about ventilation. The rib cage provides a semi-rigid cage in which pressure changes to facilitate

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13
Q

Parts of the chest

A

diaphragm: broad domed sheet of muscle which forms the floor of the thorax
External intercostal muscles & internal intercostal muscles are found between ribs
Thorax is lined by pleural membranes
Pleural cavity (space between pleural membranes) are filled with a thin layer of lubricating fluid so membranes slide easily over each other

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14
Q

Inspiration (taking air in/ inhalation)

A

Process takes up energy
- Diaphragm contracts, moving down
- intercostal muscles move up and outwards
- thoracic volume increases
- thoracic pressure decreases
- air flows into the lungs to equalise the pressure difference

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15
Q

Expiration (breathing out/ exhalation)

A

passive process
- diaphragm relaxes and move up
- intercostal muscles relax, moving down and in
- thoracic volume decreases
- thoracic pressure increases
- airflow out of lungs

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