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Biology > 9. Gas exchange > Flashcards

9. Gas exchange Flashcards

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1
Q

Why are O2 and CO2 needed in the body?

A

O2 needed for aerobic respiration. CO2 unneeded, needs to be excreted.

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2
Q

Why does gas exchange need to be able to facilitate large volumes of gas?

A
  1. Humans are large multicellular organisms
  2. Homeostasis - humans need to maintain constant body temperatures, therefore have high metabolic and respiratory rates
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3
Q

Ventilation

A

– mechanism that moves air into (inspiration) and out of (expiration) the lungs

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4
Q

Respiration

A

chemical process that produces ATP to supply energy for cells
O2 + C6H12O6 -> H2O + CO2 + ATP

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5
Q

Gross structure

A

– describes the detail that you can see with the naked eye, without the help of magnifying lenses or microscopes

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6
Q

Gas exchange

A

the diffusion of O2 from air in the alveolus to blood in alveolar capillaries; and diffusion of CO2 in the opposite direction

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7
Q

What is the trachea?

A

A flexible airway supported by C-shaped incomplete rings of cartilage

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8
Q

Why are the C-shaped rings of cartilage in the trachea incomplete?

A

Because they allow the oesophagus to expand without obstruction during swallowing, allow for flexibility.

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9
Q

What is the structure of the trachea wall?

A

Smooth muscle between ends of C-shaped rings, smooth muscle

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10
Q

What is the structure of the trachea lining?

A

Made of ciliated epithelium (not layered)
Ciliated epithelium consist of:
1. Goblet cells
2. Ciliated epithelial cells (contain cilia, columnar shape, attached to a basement membrane)

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11
Q

What are alveoli?

A
  • Tiny hollow sacs
  • The site of gas exchange in mammals
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12
Q

How big are alveoli?

A
  • 100 um - 300 um in diameter
  • 0.1 um – 0.5 um thick
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13
Q

What is the structure of the alveolar wall?

A
  • Very thin, large, flattened squamous epithelium cells (increase SA)
  • Made of squamous epithelium connected to a basement membrane
  • Some connective tissue – contains elastic fibres
  • Some cells secrete surfactant (fluid that decreases surface tension during exhalation. Prevents walls from sticking to each other by cohesion)
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14
Q

What is each alveolus surrounded by?

A

A network of blood capillaries.

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15
Q

What is the structure of bronchi/bronchus?

A
  • Similar to trachea
  • Smaller diameter
  • Irregular plates cartilage (NOT C-shaped)
  • Wall of smooth muscle and elastic fibres
  • In cross-section lining seems folded or convoluted
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16
Q

What is the structure of the bronchioles?

A
  • Walls thinner than bronchi
  • Layer of ciliated epithelium lining seems more convoluted
17
Q

How do the bronchioles transition from bronchi?

A
  • No cartilage
  • Smooth muscle and elastic fibres present
18
Q

How do the bronchioles transition into the alveoli?

A
  • No goblet cells
  • Epithelial cells are now squamous, NOT ciliated
  • Epithelial cells more cuboidal than columnar

Note: Capillary made of endothelial cells. Alveoli made of epithelial cells.

19
Q
A
20
Q

Why is the diffusion of gases between the alveoli and blood so rapid?

A
  1. Short diffusion distance
    • Walls of alveoli (single layer of epithelial cells) and capillaries (single layer of endothelial cells) 1 cell thick
    • RBCs flattened against capillary
  2. Large SA:V ratio
    • Both alveoli and capillaries have very large surface areas
  3. Enough time for efficient diffusion
    • Due to RBCs slowing down through pulmonary capillaries (caused by narrow capillary lumen)
  4. Steep concentration gradient maintained
    Maintained through:
    • Breathing ventilating longs
    • Heart circulating blood around alveoli
21
Q

What layers will O2 molecules (in alveolar air) have to pass through to go from alveolar cavity to RBC?

A
  1. From alveolar cavity through thin squamous epithelial cell
  2. Through basement membrane of epithelial cell
  3. Through basement membrane of endothelial cell (capillary)
  4. Through endothelial cell into blood plasma
  5. Through cell surface membrane of RBC
  6. Binds to haemoglobin
    Note: CO2 diffuses in the opposite direction from blood to alveolus
22
Q

What are adaptations of squamous epithelium to suit function?

A

• Extremely flattened, thin (short diffusion distance)
• Small nucleus and lots of cytoplasm (little obstruction to diffusing molecules)
• Joined closely together and act as a barrier to defend against entry of pathogens into bloodstream

23
Q

How to identify cartilage in a photomicrograph?

A

• No blood vessels
• Different colour/shade of grey

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