Human Physiology Chapter 16

external respiration

:ventilation and gas exchange between air and blood

internal respiration

:gas exchange between blood ans other tissues and oxygen utilization by the tissues

respiration

:general function is to obtain O2 for use by the bodys cells and to eliminate the CO2 the body cells produce

4 steps of external respiration

-ventilation

-exchange with air

-transport

-exchange with tissues

ventilation

:movement of air in and out of lungs

exchange with air

:O2 and CO2 are exchanged between air in alveoli and blood within the pulmonary capillaries be means of diffusion

transport

:blood transports O2 and CO2 between lungs and tissues

exchange with tissues

:O2 and Co2 are exchanged between tissues and blood by process of diffusion across systemic (tissue) capillaries

respiratory consists of

conducting zone and respiratory zone

the conducting zone contains

:respiratory airways leading to the lungs

-tranchea, primary bronchi, secondary bronchi, bronchioles, terminal bronchioles

respiratory zone consists of

-respiratory bronchioles, alveoli

alveoli

:very small, thin walled, inflatable sacs

function of alveoli

gas exchange

thoracic cavity

-heart, lungs, associated blood vessels, esophagus, thymus, and some nerves

two lungs

-divided into several lobes

-tissue consists of highly branched airways, alveoli, pulmonary blood vessels, and large quantities of elastic connective tissue

thorax

formed by 12 pairs of ribs which join sternum anteriorly and thoracic vertebrae posterily

diaphragm

-dome shaped sheet of skeletal muscle

-separates thoracic cavity from the abdominal cavity

pleural sac

-double walled closed sac that separated each lung from the thoracic wall

-plural cavity- interior part

-intrapleural fluid

atmospheric (barometric) pressure

the pressure exerted by the weight of the gas in the atmosphere

intra-alveolar pressure

:pressure inside lungs

intra-pleural pressure

:pressure outside the lungs, inside thoracic cavity

if the pressure is less than atmospheric pressure

air enters lungs

if the pressure is grater than atmospheric pressure

air leaves lungs

boyles law

at any constant temp, the pressure exerted by a gas varies inversely with the volume of gas

sequence of inspiration

1. contraction of diaphragm

2. increase lung volume

3. lowers pressure in alveoli to level below atmospheric

4. air enters lungs

sequence of expiration

1. relaxation of diaphragm

2. decrease lung volime

3. increases pressure in alveolus to level above atmospheric

4. air leaves lungs

primary determinant of resistance to airflow is

the radius of the conducting airway

chronic obstructive pulmonary disease

abnormally increases airway resistance

compliance

:refers to how much effort is required to stretch or distend the lungs

compliance is reduced by

factors that produce a resistance to distention

elastic recoil

:refers to how readily the lungs rebound after having been stretched

elastic recoil depends on

1. highly elastic connective tissue in the lungs

2. alveolar surface lining

alveolar surface lining

-reduces tendency of alveoli to recoil

-helps maintain lung stability

lung volume can be measured by

a spirometer

pulmonary ventilation

:volume of air breathed in and out in one minute

minute ventilation

minute ventilation

:tidal volume X respiratory rate

alveolar ventilation

:volume of air exchange between the atmosphere and the aveoli per minute

-less than pulmonary ventilation due to anatomic dead space

gas exchange involves

-simple diffusion of O2

-CO2 down partial pressure gradients

partial pressure

pressure exerted by each individual gas

O2 blood gas transport

alveoli --> blood --> tissues

CO2 blood gas transport

tissues --> blood --> alveoli

oxygen transport

1. dissolved in plasma

2. bound to hemoglobin

oxygen- hemoglobin disassociation curve

-shown in the curve that the major determinant of Hb saturation is blood PO2

3 ways to transport CO2

1. dissolved in plasma (10%)

2. bound to hemoglobin (30%)

3. bicarbonate ion (60%)

rhythmic breathing

-respiratory centers in brain stem establish a rhythmic breathing pattern

-medullary respiratory center

control of ventilation

-inputs to medullary inspiratory neurons from involuntary control

peripheral chemoreceptors

carotid bodies, and aortic bodies

control of repiration is stimulated by

PO2

PCO2

H+

control by PO2

-peripheral chemoreceptors

control by PCO2

-due to changes in H+ not CO2

-peripheral chemoreceptors

-central chemoreceptors

central chemoreceptors

-located in medulla

-respond to changed in brain extracellular fluid

-stimulated by increased PCO2 via associated changes in H+

metabolic acidosis

:changes in arterial H+ concentration is due to some cause other than primary change in PCO2

inhibition of ventilation

-increase in arterial PO2

-decrease in arterial PCO2

-decrease in H+

hypoxia

:abnormality in arterial PO2

-condition of having insufficiant O2 at the cell level

categories of hypoxia

-hypoxic hypoxia

-anemic hypoxia

-circulatory hypoxia

-histotoxic hypoxia

hyperpoxia

:abnormality in arterial PO2

-condition of having an above-normal arterial PO2

-can only occur when breathing supplemental O2

-can be dangerous

hypercapnia

-abnormality in arterial PCO2

:condition of having excess CO2 in arterial blood

-caused by hypoventilation

hypocapnia

-below-normal arterial PCO2 levels

-brought about by hyperventilation which can be triggered by (anxiety states, fever, aspirin poisoning)

normal pH of body fluids

7.4

alkalosis

pH > 7.45

respiratory alkalosis

caused by hyperventilation

metabolic alkalosis

caused by low acid levels or too much bicarbonate

acidosis

pH < 7.35

respiratory acidosis

caused by hypoventilation

metabolic acidosis

too much acid in blood or excessive bicarbonate loss