Chapter 15 Respiratory System Flashcards
Respiration
Process of bringing oxygen to all body cells and carrying carbon dioxide in opposite direction
2 steps
*External respiration
*Internal respiration
External and Internal Respiration
External respiration – exchange of O2 and CO2 between inhaled air and pulmonary capillaries
* Occurs in the lungs
Internal respiration – exchange of O2 and CO2 between blood in systemic capillaries and all cells and tissues of the body
* Occurs in the body tissues
Respiratory System Functions
Primary function: bring O2 into the body and CO2 out of it
* Respiratory system works together with the cardiovascular system
Secondary functions
*Phonation (voice production)
* Regulation of body temperature
* Regulation of acid-base balance
*Sense of smell
Voice Production
= Phonation
Begins in larynx = voice box
Vocal cords = vocal folds
*Stretch across lumen of larynx
*Vibrate as air passes over them
*Produce basic sound of animal’s voice
Body Temperature Regulation (respiratory)
Involves many body systems
Utilizes superficial blood vessels lining nasal passages
*Inhaled air is warmed to prevent hypothermia
*Panting increases evaporation of fluids to cool circulating blood
Acid-Base Balance respiration
Important homeostatic mechanism of the animal body
Necessary for normal chemical reactions in cells
Respiratory system influences amount of CO2 in blood by the rate of breathing
* The more CO2, the lower the blood pH
* Normal pH of blood = 7.4 (range 7.35-7.45)
The Sense of Smell
= Olfactory Sense
Receptors for sense of smell located in sensory epithelium
* Located high in nasal passages
The Respiratory Tract
Lungs and system of tubes that connect lungs to the outside world
* Upper respiratory tract
—All structures outside the lungs
* Lower respiratory tract
—All structures within the lungs
Fix this card
Trace a molecule of O2 from the air to bloodstream of animal
* Upper Respiratory Tract
* Lower Respiratory Tract
Upper Respiratory Tract
Outside of lungs
Nostrils
Nasal Cavity
*Passages
Pharynx
Epiglottis
Larynx
Trachea
*Bifurcation
Nose and Nasal Passages
External openings of respiratory tube = nostrils = nares
Nasal passages lie between nares and pharynx
Midline is called the nasal septum
Nasal Passages
Lining:
*Pseudostratified columnar epithelium, cilia, mucus, blood vessels
Main function is to condition inhaled air
* Warming
* Humidifying
* Filtering
Nasal Passage Functions
Inhaled air warmed by blood flowing through blood vessels just beneath nasal epithelium
Inhaled air humidified by mucus and other fluids on epithelial surface
Inhaled air filtered as it passes through winding passages produced by turbinates
*Particles trapped in mucous layer
* Cilia move mucus and trapped foreign material upward to pharynx, mouth
Nasal Turbinates
(Nasal Conchae)
Divide each nasal passage into 3 main passageways
Thin, scroll-like bones covered with nasal epithelium
Dorsal and ventral
Another Important Nasal Passages Function
Olfactory sense
Sensory neurons leading to olfactory nerve (cranial nerve I)
Pharynx = Throat
Common passageway for respiratory and digestive systems
Divided at rostral end by soft palate:
* Nasopharynx (respiratory)
* Oropharynx (digestive)
Opens at caudal end into:
* Esophagus (digestive)
* Larynx (respiratory)
Larynx
( Voice Box)
Connects pharynx with the trachea
Supported by hyoid bone
Made mainly of cartilage segments:
* Epiglottis (1)
* Artenoid cartilages (2)
* Thyroid cartilage (1)
* Cricoid cartilage (1)
Larynx
short, irregular tube connecting pharynx with the trachea
Epiglottis
single, leaf shaped; projects forward from the ventral portion of the larynx
* During swallowing, the epiglottis is pulled back to cover the opening of the larynx
* Most rostral of the cartilages
Larynx Functions
Voice Production
* Vocal cords – two connective tissue bands attached to the arytenoid cartilages
* Together form boundaries of the glottis
* Stretched across lumen of larynx parallel to each other
* Vocal cords vibrate as air passes over them
Vocal cords – like a guitar
* Muscles attached to cartilages adjust tension in cords
* Complete relaxation opens the glottis wide; no sound
* Lessening the tension produces lower-pitched sounds
* Tightening the tension produces higher-pitched sounds
Swallowing
Breathing stops, opening into larynx (glottis) is covered by epiglottis, material to be swallowed moves to rear of pharynx, esophagus opens
After swallowing, larynx is reopened and breathing resumes
Trachea
= Windpipe
Short, wide tube
* Fibrous tissue and smooth muscle held open by cartilage rings
–C-shaped rings spaced along length of trachea prevent collapse during inhalation
–Ciliated lining
–Mucous layer
Extends from larynx into thorax where it divides
*Bifurcation of the trachea
Structures of the Lower Respiratory Tract –
The Bronchial Tree
Bronchi
Bronchioles
(bronchial tree)
Alveolar ducts
Alveoli
Autonomic nervous system controls diameter of tubes by adjusting muscle fibers in their walls
*Bronchodilation
*Bronchoconstriction
The Alveoli
Tiny, thin-walled sacs surrounded by capillaries
Sacs lined with a thin layer of fluid that contains a surfactant
External respiration takes place in alveoli
* Oxygen and carbon dioxide exchanged between blood and air
The Lungs
Subdivided into lobes
* Distinguished externally by visible grooves and clefts
* Distinguished internally by major branches of bronchi
Same basic pattern among species
* 3 lobes in left lung (cranial, middle, caudal)
* 4 lobes in right lung (cranial, middle, caudal, accessory)
* Exception: the horse
Hilus = small, well-defined area on medial side
* air, blood, lymph, and nerves enter and leave the lung
Pulmonary Circulation
Deoxygenated blood enters lungs
* From right ventricle of heart through pulmonary artery
Vessels follow bronchial tree and subdivide
Capillary networks around alveoli
* CO2 and O2 are exchanged
Thoracic Cavity
Thorax = Thoracic Cavity = Chest Cavity
Area bounded by
* Thoracic vertebrae, ribs and intercostal muscles, and sternum
Main contents
* Lungs, heart, large blood vessels, nerves, trachea, esophagus, lymphatic vessels, and lymph nodes
Diaphragm
Thin sheet of skeletal muscle
Forms caudal boundary of thorax
Acts as respiratory muscle
*Bases of lungs lie directly on its cranial surface
* Dome-shaped in relaxed state
* Flattens when muscle contracts and enlarges volume of thorax
Negative Intra-thoracic Pressure
Partial vacuum exists within thorax
*Pulls lungs tightly out against thoracic wall
Allows lungs to follow movements of thoracic wall and diaphragm
*Inspiration and expiration
Aids in return of blood to the heart
*Veins have no muscular pump to facilitate process
Inspiration
= Inhalation
Process of drawing air into the lungs
Results from enlargement of volume of thorax
* Lungs follow enlargement passively
*Air is drawn into lungs
Main inspiratory muscles
* Diaphragm and external intercostal muscles
Expiration
= Exhalation
Process of pushing air out of the lungs
Opposite of inspiration
*Size of thorax is decreased
* Lungs are compressed
*Air is pushed out through respiratory passageways
Main expiratory muscles
*Internal intercostal muscles and abdominal muscles
Respiratory Volumes
Standardized terms for describing quantity of air involved in respiration
Tidal volume – volume in a normal breath - most animals 5 cc per pound
Minute volume – volume of air an animal breathes in and out in 1 minute
* Multiply tidal volume X respiratory rate
Residual volume – volume of air remaining in the lungs after a maximum exhale (expiration)
Alveolar Gas Exchange
Inhaled air:
* High O2
—in air diffuses into blood where level is lower
* Low CO2
Blood entering capillary:
* Low O2
* High CO2
–in blood diffuses into air where level is lower
All occurs passively through diffusion
Trace molecule of air
(upper respiratory tract)
1- Into Nose
2- Nasal Cavity
– moistened, warmed and filtered
3- Pharynx (throat)
– common passageway for digestion and respiration
4 - epiglottis
5. larynx
6. trachea
(lower respiratory tract)
7. Bronchus
8. Bronchial tree
9. Alveolar duct (bronchioles)
10. Alveolus
Alveolus
A network of capillaries where blood becomes oxygenated
Alveolar Gas Exchange -Expiration
Exhaled air:
* Higher CO2
* Lower O2
Respiratory Center
Breathing controlled by area in medulla oblongata of the brain stem
* Directs timing and strength of respiratory muscle contraction
Individual control centers for inspiration, expiration, and breath-holding
Breathing can be consciously controlled for brief periods of time
Mechanical Control System for Breathing
Operates through stretch receptors in lungs
A preset and automatic system
* Nerve impulses sent to respiratory center indicate when lungs inflate to certain point
* Muscle contractions that produce inspiration are stopped
* Muscle contractions to produce expiration are initiated
* Another set of nerve impulses is sent when lungs deflate to a certain point
* Expiration is stopped; process of inspiration is begun
Net effect is normal, rhythmic, resting breathing baseline pattern
Chemical Control System for Breathing
System affects breathing pattern only when something is out of balance
* Makes adjustments to maintain homeostasis
Chemical receptors monitor blood
* Located in carotid artery and aorta, and the brain stem
Characteristics monitored
* CO2 content
* The pH
* O2 content
CO2 Variations in the Blood
Blood level of CO2 and blood pH usually linked
Increased CO2
in blood
* Decreases blood pH
* Triggers respiratory center to increase rate and
depth of respiration
Decreased CO2 in blood
*Increases blood pH
*Excess = respiratory alkalosis
* Triggers respiratory center to decrease rate and depth of respiration
Oxygen Variations in the Blood
– Hypoxia
Effects of variations not as clear-cut as with CO2
Slight hypoxia
* Respiratory center signaled to increase rate and depth of breathing
Severe hypoxia
* Neurons of respiratory system become so depressed that impulses cannot be sent to respiratory muscles
* Can cause breathing to decrease or stop completely
Stenotic Nares
Stenotic nares is part of the brachycephalic syndrome of short-nosed dogs. Breeds such as Boxers, Bulldogs, Cavalier King Charles Spaniels, Pugs, Boston Terriers, Shih Tzus, Lhasa Apsos, etc. are all considered brachycephalic breeds. Stenotic nares means the nostrils are pinched or narrow. This makes it more difficult to breathe and causes snorting and snoring in these animals. It is a congenital trait.
Elongated Soft Palate
In dogs with an elongated soft palate, the palate overlaps the epiglottis to a considerable degree, partially obstructing the animal’s airway during breathing. This is manifested by snorting, snoring, strider, gurgling and gagging. The obstruction is worse with exercise
Brachycephalic Breed issues
Short muzzle
stenotic nares
Elongated soft palate
choanae
The mouth and nasal chambers are linked by the choanae, internal nares that open from the nasal chambers into the roof of the mouth in birds.
syrinx
Produces sound in birds instead of larynx
An enlargement of the trachea above the sternum
Bird respiratory
*Mesobronchi -A bird’s two main-stem bronchi divide and contain no cartilaginous rings.
*The mesobronchi divide into four to six secondary ventrobronchi.
*The ventrobronchi divide to become the parabronchi that connect to air capillaries, where gas exchange occurs.
*Air sacs comprise the majority of the volume of the avian respiratory system.
—small membranous sacs that act as a storage site for air, aid in thermoregulation, and help provide buoyancy to water birds
