LungsLungsBy the end of the chapter you should be

able to: Label the internal structures of the lungs State the features of the alveoli which

allow efficient gas exchange Explain the role of diffusion in gas

exchange State the features of the capillary

network that allow efficient gas exchange

Gaseous exchange

How are the structure and functions of the cardiovascular system and gaseous exchange linked?

How are they affected by physical activity and our overall level of health?

gaseous exchange system

- links the circulatory system with the atmosphere

clean warmed air enters during breathing

surface area is maximized for the diffusion of O2 and CO2 between the blood and the atmosphere

gaseous exchange system

minimize the distance for diffusion maintain adequate gradients for this

diffusion

Breathing

footprints breathing

The lungs

organs that allow gas exchange

oxygen in / CO2 out

trachea- has rings of cartilagebronchi (bronchus)bronchiolesalveoli (alveolus)

computer animation

Lungs

- site of gaseous exchange between air and blood

huge surface area in/out in the thoracic (chest) cavity surrounded by an airtight space

between the pleural membranes

Lungs

small quantity of liquid in this area allows friction-free movement

pleurisy – inflammation of the pleural membranes

ventilated by the movement of the diaphragm and ribs

Trachea, bronchi, bronchioles

lungs ventilated when air passes through a branching system of airways

trachea – leads from the throat to the lungs

bronchi (two) – at base of the trachea

Trachea, bronchi, bronchioles

bronchus – subdivide and branch extensively forming bronchial tree

cartilage – in the trachea and bronchi keep the airways open, air resistance low, and keeps them from collapsing or bursting as the air pressure changes during breathing

Trachea, bronchi, bronchioles

trachea - C-shaped rings of cartilage bronchi – irregular blocks of cartilage small bronchioles lack cartilage –

surrounded by smooth muscle which can contract or relax to adjust the diameter of the bronchioles allowing greater air flow to the alveoli during exercise

Warming and cleaning the air

air warmed (to body temperature) and moistened (from evaporation from the lining) as it travels through the nose and trachea

warming and moistening the air protects the inside of the lungs from desiccation (drying out)

Warming and cleaning the air

hairs and mucus lining the nasal passages – remove particles larger than 5-10 μm (dust, pollen, bacteria, fungal spores, sand, and viruses)

goblet cells – cells of the ciliated epithelium that produce mucus

Warming and cleaning the air

upper part of each goblet cell is swollen with mucin droplets

mucin – slimy solution of glycoproteins with many carbohydrates chains (makes it sticky and able to trap inhaled particles)

rest of cell contains the nucleus and is quite slender like the stem of a goblet

Warming and cleaning the air

mucus – also made by glands beneath the epithelium

some pollutants – sulphur dioxide and nitrogen dioxide can dissolve in mucus to form acid and irritate the lining of the airways

ciliated cells – between goblet cells

Warming and cleaning the air

continual beating carries the carpet of mucus upwards towards the larynx at a speed of 1 cm/min

mucus usually then swallowed and the pathogens are destroyed by stomach acids

Warming and cleaning the air

macrophages – phagocytic white blood cells patrol the surfaces of the airways scavenging small particles such as bacteria and fine dust particles

during infections - macrophages are joined by other phagocytic cells which leave the capillaries

Alveoli

alveoli – at the end of the pathway bewteen the atmosphere and bloodstream

very thin epithelial lining surrounded by many blood capillaries carrying deoxygenated blood

short distance – allows efficient diffusion

Alveoli

elastic fibers - in alveolar walls stretch during breathing and recoil during expiration to help force air out

fully expanded during exercise – surface area for diffusion increases

Alveoli (air sacs)

provide large surface area for gas exchange

one lung equivalent to a tennis court of surface area using alveoli

footprints alveoli

air sac in lungs deoxygenated blood

oxygenated blood

body cells

air in

air out

skool gas exchange

hyaline cartilage,mucousglands

ciliated epithelium,goblet cells

ciliated, stratified appearance.

cartilage ring-like•in appearance.

more smooth musclesas progress into

bronchiole.-less mucus glands & cartilage

terminal respiratory bronchioles

alveoli

macrophage in alveoli

monkey lung

Features of Alveoli for Features of Alveoli for efficient gas exchange - efficient gas exchange -

summarysummary

large surface area to absorb oxygen.

moist surface to allow oxygen to dissolve.

Surfactant – reduces surface tension, keeps alveoli from recoiling and sticking together

thin lining to allow easy diffusion of gases..skool adaptation of alveoli

Features of capillaries for Features of capillaries for efficient gas exchangeefficient gas exchange

dense network to carry CO2 and O2

Large surface area to transport gases

Lining is one cell thick so gases can pass through quickly and easily.

Airway Number

Approx.diamet

er

Cartilage Goblet

cells

Smooth

muscle

Cilia

Site of gas

exchange

trachea 1 1.8 cm yes yes yes yes no

bronchus 2 1.2 cm yes yes yes yes no

terminal bronchiole 48 000 1.0 mm no no yes yes no

respiratory bronchiole

300 000

0.5 mm no no no yes no

alveolar duct 9X106 400 μm no no no no yes

alveoli 3X109 250 μm no no no no yes

Breathing rate and heart rate

as body activity varies the rate cells need oxygen also varies

rate of supply of oxygen to the cells is determined by the rate and depth of 1) breathing and 2) rate at which the heart pumps blood

around the body

breathing refreshes the air in the alveoli

Breathing rate and depth

changing the depth and rate of breathing - maintains a constant concentration of O2 and CO2 no matter the level of activity

at rest – ventilate about 6.0 dm3 of air per minute

Breathing rate and depth about 0.35 dm3 of new air enters the

alveoli with each breath, only 1/7th of the total volume of air in the alveoli

means large changes in the composition of alveolar air never occur

impossible to empty the lungs completely even during forced exhalation

Breathing rate and depth

residual volume - about 1.0 dm3 of air remains in the alveoli and airways

about 2.5 dm3 of air remains in the lungs after breathing out normally

breathing deeply – lungs can increase volume by as much as 3 dm3

exercise increases the depth of breathing and breathing rate

Breathing rate and depth

Tidal volume – volume in a single normal breath

Vital capacity - volume breathed in after maximum expiration

ventilation rate – total volume of air moved into lungs in one minute

ventilation rate = tidal volume x breathing rate

expressed as dm3min-1

Breathing rate and depth

well trained athlete – achieve adequate ventilation by increasing the tidal volume with only a small increase in the breathing rate, training improves efficiency of the muscles involved with breathing

Pulse rate

ventricles contract – a surge of blood flows into the aorta and the pulmonary arteries under pressure

stroke volume – volume of blood pumped out from each ventricle

cardiac output – total volume pumped out per minute

Pulse rate pulse – a blood surge distends the arteries

(which contain elastic tissue) which stretch and subsequently recoil of aorta and arteries travels as a wave along all the arteries

pulse rate – identical to the heart rate pulse measured – at wrist where the

radial artery passes over bone or at the carotid artery in the neck

resting pulse – an indication of fitness

Pulse rate at rest – cardiac output is about 5

dm3 of blood every minute cardiac output – achieved by large

stroke volume with a low pulse rate or small stroke volume with a high pulse

more efficient – to pump slowly as the heart uses less energy than when pumping at a high rate

Pulse rate

physically fit – resting pulse low, stroke volume high, only a small increase in pulse is necessary to achieve the required blood supply – pulse rates return to resting level quickly after exercise

Pulse rate

normal range – adult resting pulse rates 60-100 bpm

average fit young adult – 70 bpm, falls with age

pulse rate higher during/after exercise, after easting or smoking

pulse rate lowest when sleeping

Blood pressure

systole – both ventricles contract left ventricle force oxygenated blood

out of the heart to supply the body maximum arterial pressure –

systolic pressure during active stroke, when blood leaves the heart through the aorta

Blood pressure heart relaxes – left ventricular

pressure falls, high pressure in the aorta closes the semilunar valve

head of pressure – elastic recoil of the aorta and the main arteries provides a steady flow of blood in the arteries towards the capillaries

diastolic pressure – minimum pressure in the arteries

Blood pressure

reflect resistance – of the small arteries and capillaries to blood flow and therefore the load against which the heart must work

resistance high, so is the diastolic pressure – results from arteries not stretching well because they may have hardened

Blood pressure

sphygmomanometer – measures blood pressure

systolic – 120 mm Hg (15 kPa) diastolic – 80 mm Hg (10.5 kPa) 120/80 – typical blood pressure

Blood pressure

BP – rise and fall during the day young adult – 110/75 60 years – 130/90 exercise – systolic 200 mm Hg, while

diastolic rarely changes

Hypertension

hypertension - high systolic and diastolic blood pressures at rest

no sharp distinction between ‘normal’ and ‘high’ blood pressure

risk of stroke and coronary heart disease increases considerably with blood pressures in excess of 140/90 (hypertensive)

Hypertension causes generally unknown short term hypertension - because

of the contraction of smooth muscle in the walls of small arteries and arterioles

may be as a result of increase in the concentration of the hormone noradrenaline which stimulates the arterioles to contract

Hypertension contraction increases the resistance

of the blood vessels and the heart works harder to force blood through the circulatory system

long term hypertension – imposes a strain on the cardiovascular system

can lead to heart failure when heart muscles weaken and are unable to pump properly

Category Blood pressure (mmHg)

systolic diastolic

optimal < 120 < 80

normal < 130 < 85

high normal 130-140 85-90

hypertension > 140 > 90

Hypertension

‘silent killer’ – no prior symptoms to give a warning of impending heart failure

90% of cases the exact cause of hypertension is unknown but linked to: excessive alcohol intake, smoking, obesity, too much salt in the diet, and genetic factors

LungsLungs

Can you? Label the internal structures of the lungs State the features of the alveoli which

allow efficient gas exchange Explain the role of diffusion in gas

exchange State the features of the capillary

network that allow efficient gas exchange

[PA] Using Figure 9.3 as your microscope view, make a labeled drawing of each slide; a, b, & c and provide a description of the structure of the walls of the trachea, bronchioles, and alveoli with their associated blood vessels. Why is there a folded membrane in c? [9]