Chapter 16

Respiratory Physiology

Ventilation

mechanical process that moves air into and out of the lungs

External respiration

ventilation and gas exchange in lungs

Internal respiration

Oxygen utilization and gas exchange in tissues

Alveoli

Air sacs in the lungs where gas exchange occurs

How many alveoli are there in humans?

300 million

What do alveoli provide?

large surface area to increase diffusion rate

Surface area provided by alveoli?

760 square feet

What form clusters at the ends of respiratory bronchioles?

alveoli

Pathway of air?

Nasal cavity, pharynx, larynx, trachea, primary bronchi, secondary bronchi, tertiary bronchi, terminal bronchioles, respiratory zone, terminal alveolar sacs

Parts in central mediastinum

heart, trachea, esophagus, thymus

Thoracic Cavity components

lungs and central mediastinum

Parietal pleura

lines thoracic wall

visceral pleura

covers lungs

intrapleural space

space between parietal and visceral pleura

Diaphragm

dome-shaped skeletal muscle of respiration that separates abdominal and thoracic cavities

Atmospheric pressure

pressure of air outside the body

Intrapulmonary (intra-alveolar) pressure

pressure in the lungs

Intrapleural pressure

pressure within intrapleural space that contains a thin layer of fluid for lubricant

Inspiration (Inhalation) pressure differences

intrapleural and intrapulmonary pressure lower than atmospheric

Subatmospheric (negative) pressure

pressure below atmospheric pressure

Intrapulmonary pressure difference in inspiration

-1cmH2O

Expiration (exhalation) pressure differences

intrapulmonary pressure is greater than atmospheric pressure and intrapleural pressure

intrapulmonary pressure difference in expiration

+1cmH2O

Transpulmonary (transmural) pressure

difference between intrapulmonary and intrapleural pressure

transpulmonary pressure is ___ during inspiration and expiration

positive

Transmural pressure does what

keeps the lungs against the thoracic wall and allows them to expand during inspiration by opposing the elastic recoil of lung tissue.

intrapleural pressure difference in inspiration

-8

intrapleural pressure difference in expiration

-5

transpulmonary pressure difference in inspiration

+7

transpulmonary pressure difference in expiration

+6

What muscles are involved in breathing?

Diaphragm, external and internal intercostal, parasternal intercostal, scalenes, pectoralis minor, stemocleidomastoid, abdominal, inspiratory muscles

In Inspiration the diaphragm

contracts

in expiration the diaphragm

relaxes

Diaphragm contraction does what

lowers making the thoracic cavity larger

Diaphragm relaxation does what?

raises, making the thoracic cavity smaller

External intercostal muscles

raise the rib cage during inspiration

Internal intercostal muscles

lower the rib cage during forced expiration

Parasternal intercostal muscles

found in between the costal cartilages and work with internal intercostals

What muscles are used for forced inspiration elevating the ribcage more?

scalenes, pectoralis minor and sternocleidomastoid

Relaxation of the inspiratory muscles causes

quiet expiration

The proces of quiet expiration is a ___ process

passive

What muscles are used for forced expiration?

abdominal

If the volume of the thoracic cavity increases vertically, the diaphragm is

contracting

If the volume of the thoracic cavity increases laterally what has happened?

parasternal and external intercostals raised the ribs

Thoracic and lung volume —> intrapulmonary pressure __ —> air in

increase; decrease

If the volume of thoracic cavity decreases vertically, the diaphragm did what?

relaxed

If the volume of the thoracic cavity decreases laterally what has happened?

external and parasternal intercostals relax for quiet expiration or internal intercostals contract in forced expiration

Thoracic and lung volume -___ —> intrapulmonary pressure __ —> air out

decrease; increase

Most of the oxygen in blood is bound to

hemoglobin

Each hemoglobin can carry _ molecules O2

4

how many hemoglobin/RBC?

280 million

Each RBC can carry _ O2 molecules

over a billion

Factors that change the affinity of hemoglobin for O2

pH and temperature

Affinity decreases at __ pH

lower

Affinity increases at _ pH

higer

Bohr effect

the increase or decrease of affinity in relation to pH

More unloading occurs at _ pH

lower

affinity is _ at increased temperature

decreased

where do RBCs obtain energy from?

anaerobic metabolism of glucose

what is made during the anaerobic metabolism of glucose?

2,3 diphosphoglyceric acid

what inhibits 2,3DPG?

oxygemoglobin

when is 2,3-DPG produced?

if a person is anemic or at high altitude

How is carbon dioxide carried in the blood?

1. Dissolved in plasma

2. as carbaminohemoglobin attached to an amino acid in hemoglobin

3. as bicarbonate ions

Carbonic anhydrase

catalyzes the reaction to form carbonic acid at high PCO2

carbonic acid is a weak acid that will dissociate into

bicarbonate and hydrogen ions

Carbon dioxide readily reacts with __ in the RBC of the systemic capillaries and plasma

water