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Exchange Surfaces And Breathing DONE > Mammalian Gaseous Exchange System > Flashcards

Mammalian Gaseous Exchange System Flashcards

1
Q

why do mammals require lots of oxygen for cellular respiration?

A
  • they are relatively big (they have a small SA:V ratio) and a large number of cells.
  • they have a high metabolic rate because they are active and maintain their body temperature independent of the environment.
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2
Q

what are the key structures of the mammalian gaseous exhange system?

A
  • nasal cavity
  • trachea
  • bronchus
  • bronchioles
  • alveoli
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3
Q

what are the key features of the nasal cavity?

A
  • a large surface area with a good blood supply, which warms the air to body temperature.
  • a hairy lining, which secretes mucus to trap dust and bacteria, protecting delicate lung tissue from irritation and infection.
  • moist surfaces, which increase the humidity of the incoming air, reducing evaporation from the exchange surfaces.
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4
Q

what is the trachea?

A

the main airway carrying clean, warm, moist air from the nose down into the chest. It is a wide tube supported by incomplete rings of strong, flexible cartilage.

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5
Q

what is the point of strong incomplete rings of cartilage?

A

they stop the trachea from collapsing. The rings are incomplete so that food can move easily down the oesophagus behind the trachea.

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6
Q

what is the trachea lined with?

A

ciliated epithelium, with goblet cells between and below the epithelial cells.

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7
Q

what is the role of goblet cells?

A

they secrete mucus onto the lining of the trachea, to trap dust and microorganisms that have escaped the nose lining.

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8
Q

how do goblet cells and cilia work together?

A

goblet cells secrete mucus onto the lining of the trachea, to trap dust and microorganisms that have escaped the nose lining. cilia beat and move the mucus, along with any trapped dirt and microoragisms, away from the lungs.

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9
Q

what effect does cigarette smoke have on cilia?

A

cigarette smoke stops the cilia from beating.

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10
Q

what are bronchioles?

A

the bronchi divide into smaller bronchioles. the smaller bronchioles do not contain rings of cartilage. the walls of the bronchioles contain smooth muscle.

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11
Q

how do bronchioles change the amount of air reaching the lungs?

A

the walls of the bronchioles contain smooth muscle. when the smooth muscle contracts, the bronchioles constrict (close up.) when it relaxes, the bronchioles dilate (open up). this changes the amount of air reaching the lungs.

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12
Q

are bronchioles lined with a thin layer of flattened epithelium?

A

yes - this makes some gas exchange possible.

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13
Q

what are the alveoli?

A

tiny sacs which are the main gas exchange surfaces of the body.

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14
Q

what are the main gas exchange surfaces of the body?

A

alveoli

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15
Q

do only mammals contain alveoli?

A

yes.

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16
Q

what is the diameter of alveoli?

A

200-300 um

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17
Q

which tissues are found within alveoli?

A

they consist of a layer of thin, flattened epithelial cells, along with some collagen and elastic fibres (composed of elastin).

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18
Q

whati is elastic recoil of the lungs?

A

elastin fibres in the alveoli allow the alveoli to stretch as air is drawn in. when they return to their resting size, they help squeenze air out.

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19
Q

what are the adaptations of alveoli that make gaseous exchange efficient?

A
  • large surface area
  • thin layers
  • good blood supply
  • good ventilation.
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20
Q

how is having thin layers good for efficient gas exchange?

A

thin layers provide a short diffusion distance.

21
Q

how is having good blood supply good for efficient gas exchange?

A

network of 280 million capillaries surround the alveoli. this provides a constant flow of blood to maintain a steep concentration gradient for both oxygen and carbon dioxide.

22
Q

how is having good ventilation good for efficient gas exchange?

A

breathing moves air into and out of the alveoli, maintaining steep diffusion gradients for oxygen and carbon dioxide between the blood and air in the lungs.

23
Q

what is the inner surface of alveoli covered in?

A

a thin solution of water, salts and lung surfactant.

24
Q

what is lung surfactant?

A

a mixture of lipids and protein made in the lungs.

25
Q

what is the function of lung surfactant?

A

reduces surface tension and makes it possible for the alveoli to stay inflated.

26
Q

what is ventilation?

A

the movement of air.

27
Q

what is the role of the rib cage during ventilation?

A

the rib cage provides a semi-rigid case within which pressure can be lowered with respect to the air outside it.

28
Q

what is the diaphragm?

A

the diaphragm is a broad, domed sheet of muscle, which forms the thorax.

29
Q

what is the thorax lined by?

A

pleural membranes, which surrounds the lungs.

30
Q

what is the pleural cavity usually filled with?

A

a thin layer of lubricating fluid so the membranes slide easily over each other as you breathe.

31
Q

what is inspiration?

A

taking air in.

32
Q

does inspiration use energy?

A

yes.

33
Q

what happens during inspiration?

A
  • diaphragm contracts, flattening and lowering.
  • external intercostal muscles contract, moving the ribs upwards and outwards.
  • volume of thorax increases
  • pressure in thorax decreases
  • pressure is now lower than the pressure of the atmospheric air, so air is drawn into the lungs.
34
Q

is expiration a passive or active process?

A

passive.

35
Q

what is expiration?

A

breathing out.

36
Q

what happens during expiration?

A
  • muscles of diaphragm relax so it moves up into its resting domed shape.
  • external intercostal muscles relax so the ribs move down and inwards under gravity.
  • elastic fibres in alveoli return to their normal length.
  • decrease in the volume of the thorax.
  • the pressure increases and is higher than the pressure of the atmospheric air.
  • air moves out of the lungs until the pressure inside and out is equal length.
37
Q

how might you exhale forcibly using energy?

A
  • intercostal muscles contract
  • pulling the ribs down hard and fast
  • abdominal muscles contract forcing the diaphragm up to increase the pressure in the lungs rapidly.
38
Q

how many people in the uk are being treated for athsma?

A

5.4 million

39
Q

what happens during an athsma attack?

A

the cells lining the bronchioles release histamines. histamines stimulate the goblet cells to make excess mucus, and the smooth muscle in the bronchiole walls to contract. as a result, airways narrow and fill with mucus, making it difficult to breathe.

40
Q

what are histamines?

A

chemicals that make the epithelial cells become inflamed and swollen.

41
Q

how are athsma medicines delivered?

A

straight into the breathing system using an inhaler.

42
Q

what are the two ways of treating athsma?

A
  • relievers
  • preventers
43
Q

what are relivers?

A

chemicals similar to the hormone adrenaline. they attach to active sites on the surface membranes of smooth muscle cells in the bronchioles, making them relax and dilating the airways.

44
Q

what are preventers?

A

they are often steroids, taken every day to reduce the sensitivity of the lining of the airways.

45
Q

how much greater is the force needed for the first breath of a baby than normal inhalation?

A

15-20 times.

46
Q

how much greater is the force needed for the first breath of a baby than normal inhalation?

A

15-20 times.

47
Q

what makes breathing easier for babies?

A

lung surfactant covering the alveoli

48
Q

why might premature babies die?

A

the cells of the alveoli do not produce enough lung surfactant for the lungs to work properly until around the 30th week of pregnancy.

49
Q

why are premature babies more likely to live now?

A

artificial lung surfactants have been produced; a tiny amount sprayed into lungs of premature baby coats the alveoli like the normal surfactant, making breathing easier.

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