chapter 9 respiratory system. points to ponder what are the parts and function of the upper and...

Chapter 9

Respiratory System

Points to Ponder• What are the parts and function of the upper and

lower respiratory system?• What is the mechanism for expiration and

inspiration?• How is breathing controlled by the nervous system

and through chemicals?• Where and how is exchange of gases

accomplished?• What are some common respiratory infections and

disorders?• What do you know about tobacco and health?• What is your opinion about bans and legislation on

smoking?

9.1 The respiratory system

Respiratory Pathway Air Flow

nose

pharynx

larynx

trachea

bronchus

bronchioles

alveoli

8.1 Overview of digestion

What constitutes the upper respiratory tract?

• Nose• Pharynx• Larynx

9.2 The upper respiratory tract

The Nose

• Opens at the nostrils/nares and leads into the nasal cavities

• Hairs and mucus in the nose filters the air– Mucus helps trap dust and move it to the pharynx to be

swallowed

• The nasal cavity has lot of capillaries that warm and moisten the air

• Specialized ciliated cells act as odor receptors– Nerve impulses generated by the receptors are interpreted

as smell

• Tear (lacrimal) glands drain into the nasal cavities that can lead to a runny nose


The Pharynx• Funnel-shaped cavity commonly called the “throat”• Connects the nasal and oral cavities to the larynx• 3 portions based on location:

– Nasopharynx where the Nasal cavity opens• Auditory tubes empty into this location

– Oropharynx where the Oral cavity opens– Laryngopharynx opens into the larynx

• Tonsils provide a lymphatic defense during breathing at the junction of the oral cavity and pharynx– Contain lymphocytes that protect against invasion of foreign

antigens that are inhaled

• Respiratory tract assists the immune system in maintaining homeostasis


The Larynx• Triangular, cartilaginous structure that passes air

between the pharynx and trachea• Called the voice box and houses vocal cords• Vocal Cords

– 2 mucosal folds that make up the vocal cords with an opening in the middle called the glottis

• Creation of Sound– Air is expelled through glottis forcing the vocal cords to

vibrate

• Pitch– High greater the tension, glottis becomes narrower– Lower glottis is wider

• Amplitude (volume): degree of vocal cord vibrations


The Larynx• Creation of Sound

– Air is expelled through glottis forcing the vocal cords to vibrate

• Pitch– High greater the tension, glottis becomes narrower– Lower glottis is wider

• Amplitude (volume): degree of vocal cord vibrations

Lower Respiratory Tract

• Trachea• Bronchial tree• Lungs

9.3 The lower respiratory tract

The Trachea

• A tube, often called the windpipe, that connects the larynx with the 1° bronchi

• Made of connective tissue, smooth muscle and C-shaped cartilaginous rings

• Lined with cilia and mucus that help to keep the lungs clean– Mucus membrane line trachea

• Pseudostratified ciliated columnar epithelium

• Mucus from goblet cells


The Trachea

• Coughing1. Tracheal wall contracts, narrowing the

diameter

2. Air moves more rapidly through the trachea

3. Expels mucus and foreign objects

The bronchial tree• Starts with two primary bronchi that lead from

the trachea into the lungs• The bronchi continue to branch into

secondary bronchi until they are small bronchioles about 1mm in diameter with thinner walls

• Bronchioles eventually lead to elongated sacs called alveoli

• Asthma Attach– smooth muscle of bronchioles contract

wheezing


The Lungs• The bronchi, bronchioles and alveoli beyond the 1°

bronchi make up the lungs• Right lung has 3 lobes --- Left lung has 2 lobes • Lobes are divided into lobules• Each lobule has a bronchiole serving many alveoli• Each lung is enclosed by membranes called pleura

– Double layer of serous membrane that produces serous fluid• Parietal Pleura – adhere to thoracic cavity wall• Visceral Pleura – adhere to surface of lungs

– Surface tension holds the two pleural layers together, therefore lungs follow the movement of the thorax when breathing

• Surface tension: tendency of water molecules to cling to one another due to hydrogen bonding between molecules


The Alveoli• ~ 300 million in lungs that

increase surface area• Alveoli are enveloped by

blood capillaries• The alveoli and capillaries are

simple squamous epithelium to allow exchange of gases– Oxygen: diffuse across

alveolar wall to bloodstream

– CO2: diffuse from blood across the alveolar wall to the aveoli

• Alveoli lined with surfactant that act to keep alveoli open– Decrease surface tension of

water


Two Phases of Breathing/Ventilation

1. Inspiration – an active process of inhalation that brings air into the lungs

2. Expiration – usually a passive process of exhalation that expels air from the lungs

9.4 Mechanism of breathing

Thoracic Cavity

• Lungs in thoracic cavity– Rib cage joined to vertebral column and

sternum– Intercostal muscles line between the ribs– Diaphragm and connective tissue

Inspiration – Active Phase1. The diaphragm and

external intercostal muscles contract– The diaphragm flattens

and the rib cage moves upward and outward (active phase)

2. Volume of the thoracic cavity and lungs increase

3. The air pressure within the lungs decrease

- creating partial vacuum

4. Air flows into the lungs

- Actual flow of air into the alveoli is passive


Expiration – Passive Phase1. The diaphragm and

external intercostal muscles relax

2. The diaphragm moves upward and becomes dome-shape – The rib cage moves

downward and inward3. Volume of the thoracic

cavity and lungs decrease

4. The air pressure within the lungs increases

5. Air flows out of the lungs


Maximum Inspiratory Effort and Forced Expiration

• Maximum inspiratory effort involves Back, chest, and neck– Increases the size of the thoracic cavity – Maximize expansion of the lungs

• Maximum Expiration effort– Contraction of the internal intercostal muscles

• Force rib cage to move downward and inward

– Abdominal wall muscles contract and push against the diaphragm

– Increased pressure in the thoracic cavity expels air

Different volumes of air during breathing

• Tidal volume – – the small amount of air that usually moves in and out with

each breath (500 mL)

• Vital capacity – – the maximum volume of air that can be moved in plus the

maximum amount that can be moved out during one breath

• Inspiratory and expiratory reserve volume – – the increased volume of air moving in or out of the body

(2,900 mL)

• Residual volume – – the air remaining in the lungs after exhalation– Air is no longer useful for gas exchange


Visualizing the Vital Capacity


Breathing controlled by the nervous system• Breathing = 12 – 20 ventilations/min• Rhythm of ventilation controlled by nervous system• Nervous control (involuntary):

– Inspiration• Respiratory control center in the brain (medulla oblongata)

sends out nerve impulses to contract muscle for inspiration– Expiration

• Respiratory control center stops sending neuronal signals to the diaphragm and rib cage

• Sudden infant death syndrome (SIDS) is thought to occur when this center stops sending out nerve signals

• Can voluntarily control breathing to force inspiration1. Stretch receptors in alveolar walls initiate inhibitory nerve

impulses 2. Stops respiratory center from sending out nerve impulses

temporarily

9.5 Control of ventilation

Breathing is chemically controlled

• Chemical control:– 2 sets of chemoreceptors sense the change in

chemical composition in body fluids (blood pH)1. Brain (medulla oblongata)

2. Circulatory system (carotid bodies and aortic bodies)

– Sensitive (stimulated by) carbon dioxide levels that change blood pH due to metabolism

– Decrease pH (below 7, increase in H+ ions)• Respiratory center increases rate and depth of

breathing• More CO2 is removed from blood

9.5 Control of ventilation

Exchange of gases in the body

• Oxygen and carbon dioxide are exchanged in the lungs and tissues

• The exchange of gases is dependent on diffusion

• Partial pressure is the amount of pressure each gas exerts (PCO2

or PO2)

• Oxygen and carbon dioxide will diffuse from the area of higher to the area of lower partial pressure

9.6 Gas exchanges in the body

External respiration • Exchange of gases between the lung alveoli and the

blood capillaries• PCO2

is higher in the lung capillaries than the air thus CO2 diffuses out of the plasma into the lungs– CO2 carried in plasma as bicarbonate ions (HCO3

-)• The partial pressure pattern for O2 is just the opposite

so O2 diffuses the red blood cells in the lungs– O2 diffuses into plasma and into RBC in lungs

Carbon dioxide transport: carbonic

H+ + HCO3- H2CO3 anhydrase H2O + CO2

Oxygen transport:Hb + O2 HbO2 (oxyhemoglobin)(deoxyhemoglobin)


External respiration• Hyperventilate (breathe at a high rate)

– Push reaction to the right– Fewer hydrogen ions alkalosis– High blood pH– Solution: Inhibit breathing

• Hypoventilate (breathe at a low rate)– Hydrogen ions build up in the blood acidosis– Buffer compensate for low pH– Solution: Increase breathing

Internal respiration

• The exchange of gases between the blood in the capillaries outside of the lungs and the tissue fluid

• PO2 is higher in the capillaries than the tissue fluid

therefore, O2 diffuses out of the blood into the tissues

Oxyhemoglobin gives up oxygen:

HbO2 Hb + O2

Most CO2 is carried as a bicarbonate ion:

carbonic

CO2 + H2O anhydrase H2CO3 H3 + HCO3

-


Internal respiration

1. Oxygen diffuses out of the blood into tissues- PO2 of tissue fluid is lower than that of blood

because cells use up oxygen in cellular respiration

2. CO2 diffuses into the blood from tissues

- PCO2 of tissue fluid is higher than the blood because CO2 is produced by cells and collected in tissue fluid

- CO2 enters the RBCs and plasma to be either

- Taken up by hemoglobin in RBC to from HbCO2

- Taken up by RBC and formed into HCO3-

- Excess H+ from this reaction combines with Hemoglobin to form HHb, reduced hemoglobin

Upper respiratory tract infections

• Sinusitis – blockage of sinuses

• Otitis media – infection of the middle ear– Tubes placed in the eardrums to prevent buildup of

pressure in the middle ear

• Tonsillitis – inflammation of the tonsils

• Laryngitis – infection of the larynx that leads to loss of voice

9.7 Respiration and health

Lower respiratory tract disorders• Pneumonia –

– infection of the lungs with thick, fluid build up

• Tuberculosis – – bacterial infection that leads to tubercles (capsules)

• Pulmonary fibrosis – – lungs lose elasticity because fibrous connective tissue builds up in the

lungs usually because of inhaled particles

• Emphysema – – chronic, incurable disorder in which alveoli are damaged and thus the

surface area for gas exchange is reduced

• Asthma – – bronchial tree becomes irritated causing breathlessness, wheezing

and coughing

• Lung cancer – – uncontrolled cell division in the lungs that is often caused by smoking

and can lead to death


Health focus: Things you should know about tobacco and health

• All forms of tobacco can cause damage• Smoking increases a person’s chance of lung,

mouth, larynx, esophagus, bladder, kidney, pancreas, stomach and cervix

• The 5-year survival rate for people with lung cancer is only 13%

• Smoking also increases the chance of chronic bronchitis emphysema, heart disease, stillbirths and harm to an unborn child

• Passive smoke can increase a nonsmokers chance of pneumonia, bronchitis and lung cancer


chapter 9 respiratory system. points to ponder what are the parts and function of the upper and...

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