DA 6 Flashcards
Pharyngeal arches
- aggregations of mesenchyme in area of pharynx
- separated by grooves:
- pouches (inside) - lined by endoderm
- clefts (outside) - lined by ectoderm
How many paried pouches are there in mammals?
four
Pouches (inside) from pahryngeal arches are lined by…
endodern
Clefts (outside) from pharyngeal arches are lined by…
ectoderm
Derivative of pharyngeal Pouch I
Middle ear cavity and auditory tube
Derivaive of pharyngeal pouch II
Palatine tonsil
Derivative of pharyngeal pouch III
External parathyroid and thymus
Derivative of pharyngeal pouch IV
- Internal parathyroid and ultimobranchial body
- Ultimobranchial body will eventually become incorporated with thyroid gland to form parafollicular cells
Respiratory diverticulum
- Forms as an outgrowth of ventral part of foregut.
- Tracheoesophageal septum separates it from the rest of the primitive gut.
Resiratory system extends into _____ mesoderm.
Splanchnic
Respiratory system bifurcates to form _____
Lung Buds
Each lung bud enlarges to form ____
Primary bronchus
Primary bronchus branches to form _____
Definitive bronchial tree
Lung maturation: embrynic stage
Lung bud formation
Lung maturation: pseudo-glandular stage
Formation of terminal bronchioles
Lung maturation: canalicular stage
formation of respiratory bronchioles
Lung maturation: terminal sac stage (stage of primitive alveoli)
- Respiratory bronchioles divide to form alveoli
- Formation of alveolo-capillary membrane
- Production of surfactant
At what stage of lung maturation is respiration possible:
terminal sac stage
Lung maturation: alveolar stage
- All of bronchial tree is completed
- Increase in number of alveoli by septation of present ones.
- Lung growth and expansion
Respiratory capacity is increased by ____ and _____.
Exercise and hypoxia (at high altitude oxygen concentration remains the same, but oxygen pressure decreases, which means the oxygen from alveoli passes through a slower rate, this inreases rate and depth of respiration and facilitates growth and expansion of alveoli)
Majority of alveolar cells (95%) are….
Squamous
5% of alveolar cells are….
Cuboidal and produce surfactant (Type II)
Functionality of the lung
Varies with species, in most species lung is in terminal sac stage
When is lung functionally mature?
At birth
Surfactant
Phospholipid fluid coating alveoli
When is surfactant produced
Produced in late fetal stage
Function of surfactant
prevents collapse of alveoli in expiration
Why are breathing movements before birth important?
For conditioning of respiratory muscles.
Contributing factors of anomalies of respiratory system
- Its endodermal origin (has low differentiating ability)
- Its sequential development (insults affect different stages)
- Available space (limited expansion with small thoracic cavity)
Pharyngeal pouches anomalies are related to formation of ____ or ____.
Cysts of fistulas
Congenital guttural pouch tympany
- THis is a gaseous distension due to defective opening into pharynx.
- Signs are swelling caudal to mandible.
- Treatment/management - surgical correction - curative
- create opening through the pharynx or median septum to allow air to pass to the functional pouch.
Collapsed trachea
One of the most common causes of airway obstruction
- partial occlusion of trachea due to defective cartilages
- common in miniature and toy breeds of dog
- signs: honking cough, gagging
- treatment: surgical (prosthetic rings), cartilage building supplements
With a collapsed trachea it is important to manage______.
Obesity
Tracheal hypoplasia (stenosis)
- Local narrowng as primary defect (or fusion of tracheal cartilages)
- Predisposition - brachycephalic breeds
- Signs: nonspecific respiratory distress (coughing, wheezing)
Tracheoesophageal fistulas
Most severe and most common
- due to abnormal partitioning of espophagus and trachea
- Most common form is that associated with esopageal atresia
- Usually associated with other birth defects (VACtreL association)
- Symptoms: cyanosis, coughing, vomiting
- Treatment: surgical correction (complications likely - like refistulation)
- This condition can be aquired following surgeries or pressure from tracheostomy tube
What is the most common form of tracheoesphgel fistula?
Esophagela atresia (seen in figure A)
B, C, D are other variations
Lung anomalies are ____
rare and usually partial conditions
Lung agenesis
Failure of lung buds to develop - rare
Accessory lobes
From additional lung buds (lung hypoplasia also)
Pulmonary cysts
- Form when terminal bronchioles lose connection with main branch
- Result is poor drainage of the fluid filled cyst –> leads to chronic infections
Lung hypoplasia
Small, poorly developed lung (associated with skeletal defects or diphragmatic hernia)
Respiratory distress syndrome (RDS) is called what in humans?
Hyaline membrane disease
What is a complementary condition in domestic mammals of RDS?
Neonatal maladjustment syndrome (barker syndrome)
Causes of RDS:
- insufficiency of surfactant (premature birth)
- incomplete lung expansion (insufficient blood to newborn)
- Dystocia –> hypoxia –> irreversible lung changes
Symptoms of RDS
Cyanosis, apnea, shallow breathing
Management of RDS
- Aritifical surfactant with glucocorticoids (to speed up maturation of lungs)
- Continuous positive airway pressure (CPAP) to keep alveoli open all the time
Atelectasis:
absence of air in a normally air-filled space; some parts of lung at birth are still atelectactic at birth, lung that have never taken a breath will sink, lung that has taken at least one breath will float
Acquired form of respiratory distress syndrome is from …..
From fluid accumulation in the lungs
Primitive gut divisions:
Pharynx, foregut, midgut, hindgut
Pharynx
-Extends from orpharyngeal membrane to esophagus -not surrounded by coelom (cavity) -Its mesoderm is not split
