Functions of Respiratory System

Supply body with oxygen and dispose carbon dioxide.

Major Processes of Respiratory System

Pulmonary Ventilation & External Respiration

Pulmonary Ventilation

Movement of oxygen from lung air to blood.

External Respiration

Movement of oxygen from lung air to blood & movement of carbon oxygen from blood to lung air

Conducting Zone of Respiratory System

condiuts/passageways for air to reach sites for gas exchange.
-Nose
-Nasal Cavity
-Pharynx
-Larynx
-Trachea
-Bronchi & Branches

Respiratory Zone

Actual sites of gas exchange
-respiratory bronchioles
-alveolar ducts
-alveoli

Nose and Nasal Cavity

Provides airway for respiration
-moisten entering air
-warms entering air
-filters entering air
-houses olfactory receptors

External Nose

Root (frontal bone)
Bridge (Nasal Bone)
Septal, Lateral, Alar Cartilages (Hyaline)
Alae (Dense Connective Tissue

Nasal Cavity

Extends from nares (nostrils) to choanae (opening to pharynx). Floor of cavity is hard palate (anterior), muscular soft palate (posterior). Hairs extend into nasal vestibule to filter coarse particles from entering air.

Olfactory Mucosa

Mucous membrane lining superior region; has smell recptors

Respiratory Mucosa

Lines remainder of nasal cavity.
-ciliated, pseudostratified columnar epithelium
-goblet cells with mucous and serous glands
-mucus has lysozyme and defensins that trap dirt and kill bacteria

Conchae

Superior, Middle, Inferior protrusions that create turbulence in inspired air

Pharynx

Throat

Common passage way of the Pharynx

Respiratory Passageway = nasal cavity to larynx
Digestive Passageway = oral cavity to esophagus

Regions of the Pharrnx

Nasopharynx, Oropharynx, Laryngopharynx

Larynx

Connects pharynx to trachea.

Function of Larynx

Controls passage of air and food to proper channels

Epiglottis

Spoon shaped elastic cartilage extending from posterior tongue to anterior rim of thyroid cartilage.
-covers laryngeal inlet during swallowing...prevents food from trachea

Glottis

Opening between vocal folds, lets air pass through to trachea

Trachea

Flexible tube from larynx inferiorly branching into two main bronchi. Has sensory receptors that detect foreign particles and has a cough reflex.
-cleans, warms, moistens passing air

Layers of Trachea

1. Mucosa
2. Submucosa
3. Cartilage
4. Adventitia

Mucosa

Pseudostratified ciliated epithelium with goblet cells and sweeps mucus

Submucosa

CT layer around mucosa

Cartilage

C shaped rings of hyaline cartilage around anterior and side
-allows flexing and prevents collapse of tube lumen

Adventitia

Outermost layer of CT

Main Right and Left Bronchi

Division of Trachea, each enters respective lung at hilum
PRIMARY

Carina

Ridge formed by most inferior tracheal cartilage
-radiological landmark that seperates right and left main bronchi
-sensitive to mechanical stimulation, powerful cough reflex.

Lobar Bronchi

Three in right lung and two in the left lung
-supply each lobe of lungs
SECONDARY

Segmental Bronchi

Branching of lobar/secondary bronchi

Bronchiles

Passageways less than 1 mm diameter

Respiratory Bronchioles

Beginning of Respiratory Zone- where gas exchange occurs

Alveolar Ducts

Rings of smooth muscle cells and CT fibers

Alveolar Sacs

Clusters of alveoli attached to alveolar ducts

Alveoli

Microscopic air-filled chambers at end of bronchial tree
-walls are simple squamous epithelium
-external surface intimately associated with pulmonary capillaries
-main sites of gas exchange

Respiratory Membrane

In respiratory zone, layers through which gas exchange occurs by simple diffusion composed of wall of alveolus and wall of pulmonary capillary

Alveolar Walls

Mostly simple squamous epithelium (type I cells)
-also has type II cells (cuboidal cells secreting surfactant fluid)
-many macrophages that digest debris & bacteria
-surrounded by elastic fibers
-have alveolar pores

Alveolar Pores

Openings between adjacent alveoli
-allow equalization of inflation

Lungs

Mostly air-filled spaces and elastic CT

Where are the lungs located?

Right and left lungs are suspended in their own subcavities within thoracic cavity

Apex

Just deep to clavicle

Base

Just superior to diaphram

Hilum

Indentation on mediastinal aspect of each lung
-site entry of main bronchus to each lung
-also entry of pulmonary blood vessels and systemic blood vessels

How many lobes do the lungs have?

The left lung has 2 lobes and the right lungs have 3 lobes. Lobes are separated by fissures.

Blood Circulation of Lungs

Pulmonary & Bronchial

Pulmonary Circulation

Gas exchange. Carbon dioxide from blood to lung air and oxygen from lung to blood.

Pulmonary Plexus

Sympathetic & parasympathetic fibers
-enter at hilum and run along bronchial tree with blood vessels

Parasympathetic Fibers

Cause smooth muscle constriction of bronchiole tubes

Sympathetic Fibers

Release neurotransmitters that cause bronchiole smooth muscle relaxation and dilation of tubes

Pleurae

Thin, double-layer of serous membranes

Parietal Pleura

Lines inside of thoracic cavity and superior diaphram

Pleural Cavity

Space between parietal & visceral pleurae, filled with pleural fluid (lubricating)

Visceral Pleura

Lines the outer surface of lungs

Pressures

Atmospheric Pressure = 760 mmHg (at sea level)
Pulmonary Pressure/Alveolar Pressure = Atomspheric Pressure (after equilibration)
Intrapleural Pressure = about 3-4 mmHg less than Atmospheric Pressure

Intrapleural Pressure

Negative pressure always less than atmospheric pressure and is needed to keep lungs from collapsing.

Muscular Activity

Volume changes for breathing. Diaphragm contracts and flattens inferiorly. External intercostals contract to expand rib cage. Internal intercostals contract to contract rib cage for forced exhalation.

Recoil of Lungs

Elasticity of lung tissue allow passive exhalation:
1. elastic fibers around alveoli
2. surface tension of fluid lining inside of alveolar walls

Surfactant

Amphiphilic/amphipathic, detergent like molecule
-secreted by Type II alveolar cells
-decreases surface tension of fluid
-saves from having to reinflate alveoli

How to you treat premature babies who lack sufficient surfactant?

Inhaling it

Tidal Volume

About 500 mL, during quiet breathing

Inspiratory Reserve

About 3100 mL, amount of air that can be inhaled after normal inhale

Expiratory Reserve

About 1200 mL, amount of air that can be exhaled after normal exhale

Residual Volume

About 1200 mL, volume of air that cannot be exhaled

Spirometer

Instrument for measuring lung volumes and capacities

Obstructive Pulmonary Disease

increased airway resistance

Restrictive Disorders

Reduction in lung capacity

Forced Vital Capacity (FVC)

Deep breath, then forcefully exhale as quickly as possible

Forced Expiratory Volume (FEV)

Amount of air expelled within a particular time interval of FVC test

Dead Space

Some inspired air only gets into conducting zone, not reach respiratory zone, so not participate in gas exchange

Anatomical Dead Space

Volume of conducting zone (about 150mL)

Alveolar Dead Space

Volume from alveoli that do not have gas exchange

Minute Ventilation Rate (MVR)

=(TV)(breaths per minute)

Alveolar Ventilation Rate (AVR)

=(TV - DeadSpace)(breaths per minute)

Lung Compliance

Measure of ease with which lungs expand

Alveolar Gas Exchange/External Respiration

Blood in capillaries exchanges gases with air in alveoli

Gas Transport

About 98% of oxygen pick up in lungs is transported by hemoglobin in red blood cells.

Oxygen-hemoglobin Dissociation Curve

Unloading of oxygen from Hb to tissues influenced by tissue pressure of oxygen

Medullary Respiratory Centers

Ventral Respiratory Group (VRG) & Dorsal Respiratory Group (DRG)

Ventral Respiratory Group

Network of neurons in ventral brainstem that extends from pons-medulla to spinal cord and seems to be the rhythm-generating center

Inspiratory Neurons Fire

Impulses travel along phrenic nerve & intercostal nerves

Expiratory Neurons Fire

Inspiratory outputs stops

Dorsal Respiratory Group

Neurons intergrate input from peripheral stretch receptors and chemoreceptors, relays info to influence VRG activity

Chronic Obstructive Pulmonary Disease (COPD)

Any disorder in which there is long-term obstructive of airflow and substantial reduction of pulmonary ventilation.

Asthma

Most common chronic illness in children (around 5000 deaths per year of all ages and rising)

Allergic Asthma

Allergen exposure, release of imflammatory chemicals from mast cells

Non-Allergic Asthma

Triggered by things such as infections, pollutants, cold air, excercise, emotions

Symptoms of of Asthma

Bronchiole spasms, mucus buildup, severe coughing, wheezing, sometime suffocation, and later on tissue damage

Emphysema

-Destruction of alveolar walls -> larger, but fewer alveoli
-Lungs lose elasticity -> become over-compliant
-Inspiration OK; expiration requires much work
-Air passages tend to collapse & trap air
-Highly inflated lungs -> barrel-chested -> stretched inspiratory muscles