HUMB1001 Lecture Notes - Lecture 7: External Intercostal Muscles, Breathing, Pulmonary Pleurae

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12 Jun 2018

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Pulmonary Ventilation

How do we move air in and out of our lungs?

How do we breathe?

• Puloar etilatio is ahieed through appliatio of Boles La; hih

describes the relationship of pressure & volume:

    

To move air into the lungs (inhale):

• Decrease pressure in the lungs by contracting the muscles of inspiration

• This increases the volume of the lungs

• Sets up a pressure gradient and air flows into lungs to equilibrate

To move air out from the lungs (exhale):

• Increase pressure in the lungs by contracting the muscles of expiration

• This decreases the volume of the lungs

• Sets up a pressure gradient and air flows out of lungs

• Partial pressures of oxygen in atmospheric air at sea level; in the lungs; in the

pulmonary veins and in the pulmonary arteries

Pulmonary Ventilation

• The lungs are located inside the thoracic cavity and held

open by the expanding ribcage

• They rely on the muscles of the chest wall: intercostal

and diaphragm to expand and contract

• The lungs are held fast against the chest wall b their

covering membranes, the pleura

How is chest wall expansion transmitted to the lungs?

• Parietal pleura lines the interior of the thoracic cavity

• Visceral pleura lines the exterior of the lungs

• Potential space between the pleural contains pleural fluid

• It provides frictionless environment with cohesive forces

sticking the two together

• Any expansion of the parietal pleura is seamlessly

transmitted to the visceral pleura, and therefore the lungs

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Normal (quiet) Inspiration

• Diaphragm contracts & ribs are lifted by the external intercostal muscles

• Intrapulmonary pressure falls and 0.5litres of air

Dimensions of the Chest Cavity

• Inhalation requires muscular activity & chest size

changes

• Contraction of the diaphragm flattens the dome

and increases the vertical dimensions of the chest

• External intercostal muscles move the ribs

upwards & outwards

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Normal (quiet) Expiration

• Passive process with no muscle action

• Lungs return to their original size

• Caused by elastic recoil & surface tension forces in alveoli

• Alveolar pressure increases & air is pushed out

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Document Summary

How do we breathe: pul(cid:373)o(cid:374)ar(cid:455) (cid:448)e(cid:374)tilatio(cid:374) is a(cid:272)hie(cid:448)ed through appli(cid:272)atio(cid:374) of bo(cid:455)les(cid:859) la(cid:449); (cid:449)hi(cid:272)h describes the relationship of pressure & volume: To move air into the lungs (inhale): decrease pressure in the lungs by contracting the muscles of inspiration, this increases the volume of the lungs, sets up a pressure gradient and air flows into lungs to equilibrate. To move air out from the lungs (exhale): How is chest wall expansion transmitted to the lungs: parietal pleura lines the interior of the thoracic cavity, visceral pleura lines the exterior of the lungs, potential space between the pleural contains pleural fluid. It provides frictionless environment with cohesive forces sticking the two together: any expansion of the parietal pleura is seamlessly transmitted to the visceral pleura, and therefore the lungs. Inhalation requires muscular activity & chest size changes: contraction of the diaphragm flattens the dome and increases the vertical dimensions of the chest, external intercostal muscles move the ribs upwards & outwards.

Related Questions

Background

Almost all animal and plant cells require oxygen and give off carbon dioxide. This is called gas exchange and it occurs by passive diffusion. Some animals do all or most of their gas exchange across their skin (for example amphibians) but they have very low metabolisms and use very little oxygen and get rid of very little carbon dioxide.

On the other hand humans (and other mammals) have very high metabolic requirements and we canât rely on gas exchange over the limited 1.5 to 2.0 square meters of our skin to get enough oxygen in and carbon dioxide out fast enough. Our gas exchange takes place across a very thin membrane in the Alveoli of the lung and the gas exchange surface in humans is estimated to be between 50 and 100 square meters, or between 25 and 67 times our skin surface area.

Our lungs provide a huge surface for gas exchange but they are a dead-end system. Once the oxygen in the lungs is used up it needs to be replenished and carbon dioxide builds up in the air spaces in the lungs and needs to get out. This is where the diaphragm and a few of the skeletal muscles become important. In its relaxed state the diaphragm is at its longest and the space in the thoracic cavity (and the lungs) is small. When the diaphragm contracts it shortens, which increases the volume of the thoracic cavity (and the lungs). The increase in size means the pressure is lower in the lungs than outside so air comes into the lungs (inhalation). As the diaphragm relaxes, the lungs decrease in size enough that the pressure inside the lungs is higher than the external air pressure so air comes out (exhalation).

Introduction

In this lab you will be building a model of a lung and experimenting with different ways to breath.

Supplies:

In the Lab Kit

One round 9" balloon (one lung, we donât need two for this)
medium-sized plastic bag large enough to fit over bottom end of bottle (diaphragm)
medium-size, thin rubber band

You supply

plastic 2-liter soda bottle with bottom cut off (thoracic cavity)

Tape (optional)

Directions:

1. Insert the balloon through the open bottom of a modified 2-liter soda bottle and up over the neck of the bottle. Pull the end of the balloon over the edges of the neck of the bottle. The balloon is held open by the neck of the bottle.

2. Place the plastic bag over the bottom (open) end of the 2-liter bottle and use the rubber band to hold it in place. This will serve as the diaphragm. To inflate the lung, blow into the balloon just before you fasten the rubber band. You can also wrap tape over the edges of the plastic bag to minimize air leaks

3. Grasp the bottom of the plastic bag and pull it down and push it up. Watch as the "lungs" (the balloon) expand and contract as you do this. The balloon has to change size because the air space between the balloon and bottle must remain constant. (Well, it would if the seal around the plastic bag and bottle were perfect).

You may block the "trachea" (the neck of the bottle) so that the air supply is cut off and watch as nothing happens when the "diaphragm" is pushed in and out.

This model isnât perfect. None of the joints are air tight as they would be in a real thoracic cavity. Pull the âdiaphragm down and watch the lungs expand . If you hold it in place, the lungs will collapse again over time. This is because of leaks and is not how real lungs work. Pushing the diaphragm in and pulling it out over and over does give you an idea of how lungs work. As the diaphragm tightens, contracts (pull down on the plastic bag) the lungs fill with air. As the diaphragm relaxes (push up on the plastic bag) air is expelled from the lungs .

There are several different ways we breath, i.e. expand our thoracic cavity so that our lungs can expand. You have just made a demonstration model of the diaphragm at work. You can also use your rib cage to expand and contract so that you can inhale and exhale. There are muscles between and around your ribcage which you can use to change the size of your thoracic cavity.

This is approximately what your model of a lung will look like.

Answer the questions on the Report Page

Report Page Name

1. Put a hand on your lower ribcage and try moving your ribs out and in. Does air also move in and out?

2. Someone with an upper back or neck injury may not have the options of using diaphragm or ribs to breath. They can learn to use the clavicle and the muscles attached to expand their thoracic cavity a small amount and breathe independently for short periods of time. Put your hand on you clavicle and try to raise and lower just that bone without using your diaphragm or your ribs. It isnât easy but you should be able to get a little air into and out of your lungs this way. How effective do you think this way of breathing is?

3. When you take a really deep breath you use all these muscle groups to help. Take a really deep breath and notice that your ribs expand, your lower abdomen comes out (a sign that the diaphragm has contracted) and your shoulders lift a little (the upper chest and clavicle are working). Now take a relaxed breath. Only your abdomen should go in and out. The movement of your abdomen is a result of the contracting diaphragm pushing on the contents of your âgutâ which forces your abdomen to push out.

Do you breath in or out when your diaphragm contracts?\

4. If a hole were poked in your thoracic wall (the wall of the pop bottle â the hole should be at least the diameter of a pencil)

a. what would happen when you tried to breath? (This is a pneumothorax).

b. Is the space between the balloon and plastic bottle still required to remain constant?

5. Would it be possible to live with a paralyzed diaphragm? Explain your answer.

fuchsiamuskrat152

QUESTION 1

Cellular respiration uses________to produce energy and releases ________as a waste product.

		O₂; CO₂
		CO₂; O₂
		ATP; G3P
		G3P; ATP

5 points

QUESTION 2

Select all of the following that compose the conducting pathways in the respiratory system.

		nasal cavity
		Pharynx
		Larynx
		Trachea
		Bronchi
		Alveoli

5 points

QUESTION 3

Match each structure with its' function.

- A. B. C. D. E. F. G.	Nasal Cavity
- A. B. C. D. E. F. G.	Alveoli
- A. B. C. D. E. F. G.	Larynx
- A. B. C. D. E. F. G.	Trachea
- A. B. C. D. E. F. G.	Bronchi
- A. B. C. D. E. F. G.	Bronchioles
- A. B. C. D. E. F. G.	Pharynx

A.	Throat
B.	Very small branches of bronchi within the lungs.
C.	Larger branching passages for air within the lungs.
D.	Location of gas exchange with the blood.
E.	Carries air from larynx and branches into bronchi.
F.	Location of the voice box, earliest location where only air passes.
G.	Carry air into the pharynx, earliest location of cleaning, warming, and humidifying the air.

8 points

QUESTION 4

Mammals are able to inhale because increasing the volume of the thoracic cavity will decrease the pressure within the lungs. This is called_____

		pump-controlled breathing
		forced inflation breathing
		negative-pressure breathing
		stretch breathing

6 points

QUESTION 5

Indentify which muscles are primarily responsible for quiet (normal, relaxed) inspiration?

		diaphragm
		internal intercostals
		sclaenes
		abdominal muscles

coffeepig115

fill the blanks with the terms given

Terms: 0.21, 21, 78, 760, altitude, blood, Boyle's, Dalton's,decimal, decreased, diaphragm, directly, external intercostal,Henry's, into, inverse, lowers, out of, oxygen, parasternal,partial, percent concentration, pressure, solubility, temperature,total, volume

_________ law states that there is a/an ________ relationshipbetween [listed alphabetically] the _________ of a gas and the___________ of the gas. That is, an increase in one of the factorsis associated with a decrease in the other factor and vice versa.Thoracic cavity size determines the volume of the air in the lungs.Thus, this law is fundamental to explaining why an increase in thethoracic cavity size due to expansion of the rib cage in thehorizontal [front-to-back and side-to-side] directions viacontraction of the ___________ and _________ muscles, (listedalphabetically) and vertical [up-and-down] direction viacontraction of the ___________ causes a resultant decrease inintrapulmonary pressure, creating a pressure gradient that drivesair _____________ the lungs. Conversely, it explains why when thesize of the thoracic cavity is _________ by relaxing the musclesused during inspiration, the pressure of the gas in the lungsincreases, exceeding atmospheric pressure, creating a pressuregradient that then forces air _________ the lungs ________ lawstates that the _______ pressure of a mixed gas is equal to the sumof the ___________ pressures exerted by each of the individualgasses in the mix, which are exerted independent of one another.This law is important to pulmonary physiology because theatmospheric air we breath is a mixed gas that contains roughly__________% nitrogen and _______% oxygen. Moreover, according toHenry's law, it is the partial pressure of the oxygen in the air webreath that is the main determinant of how much of the air's oxygenwe can drive into our blood and make available to the body. A gas'spartial pressure can be calculated by multiplying the totalpressure of the mixed gas by the gas's ____________ in the mixedgas. Thus, the partial pressure of oxygen, at sea level isdetermined by multiplying total atmospheric pressure at sea level -which equals ___________ millimeters of mercury (denoted mm Hg) by________ - oxygen's percent concentration in atmospheric air,expressed as a ____________. ________ law actually states that theamount of gas we can drive into solution is _________ dependentupon 3 factors. These 3 factors are 1) the solubility of theparticular liquid for the particular gas you are considering, 2)the temperature (more gas can be driven into liquids at lowertemperatures than at higher temperatures) and 3) the partialpressure of the gas under consideration. In the body, theparticular gas we are interested in driving into a fluid is__________ and the particular fluid we are interested in drivingthe gas into is our ___________. Because blood has a particularsolubility for oxygen - and this is constant, and because thehomeostatic mechanisms in the body keep body temperature relativelyconstant, this means the single most important factor thatdetermines how much oxygen can be driven in to our blood is thepartial pressure of the oxygen in the air we breath. At sea level -the partial pressure of oxygen in atmospheric air = 760 x 0.21 =159 mm Hg. However, if one climbs to the peak of Mt. Everest, wherethe air is still a mixed gas that contains only ~21% oxygen, butthe air there is 'thinner' i.e. there is just less of it up there,the total pressure of the gas drops to about 250 mm Hg, whichsignificantly __________ the the partial pressure of oxygen and theamount of air that can be forced into the blood at that altitude.Thus this gas law explains why many individuals initiallyexperience ____________ sickness when they vacation in the Rockiesor the Swiss Alps but normally live at much lower elevations.

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HUMB1001 Lecture Notes - Lecture 7: External Intercostal Muscles, Breathing, Pulmonary Pleurae

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